A flow barrier and containment strategy for underground storage of energy carriers using clay suspensions

Abstract

Aspects of the present disclosure generally relate to compositions, processes, and systems for subsurface containment or storage of a fluid. In an aspect, a composition for subsurface containment or storage of a fluid is provided. The composition includes an amount of a swellable clay and an aqueous material. Compositions described herein may be set-delayed compositions. In another aspect is provided a subsurface storage or containment system for a fluid that includes a porous medium and a composition described herein. In another aspect, a process for forming a subsurface storage or containment system for a fluid is provided. The process includes introducing a composition comprising a swellable clay and an aqueous material into a subsurface formation.

Description

PCT Patent ApplicationAttorney Docket No.: UWYO-0130PCTitle: A Flow Barrier and Containment Strategy for Underground Storage of Energy Carriers Using Clay SuspensionsInventors: Behbood Abedi; Saman AryanaCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and benefit from U.S. Provisional Application No. 63 / 733,941, filed on December 13, 2024, which is incorporated herein by reference in its entirety.FIELD

[0002] Aspects of the present disclosure generally relate to compositions, processes, and systems for subsurface containment or storage of a fluid.BACKGROUND

[0003] Energy carriers such as hydrogen play a critical role in enabling a low-carbon economy, and ultimately zero-carbon emissions. To be a useful fuel source, large-scale storage of hydrogen is necessary. Despite its high potential, hydrogen geological storage is still in its infancy, with very few7large-scale underground hydrogen storage projects being undertaken worldwide. Existing and developing approaches for subsurface storage of hydrogen rely on salt domes and salt caverns. Yet salt domes and caverns suffer from low storage capacities and insufficient seal integrity, and their effectiveness as part of a broader energy storage network is limited by their low7number and limited geographical locations. These constraints hinder the mass adoption of hydrogen as a clean energy7source. Conventional underground gas storage in salt caverns and porous formations are challenged by leakage, limited to specific geologies and certain geographical locations, lateral and vertical containment failures, as well as induced and triggered seismicity. Underground hydrogen storage (UHS) presents several additional challenges. First, molecular hydrogen (EU) is the smallest molecule known, and unlike carbon dioxide (CO2) and methanol, easily diffuses through porous media, making subsurface leakage of hydrogen a significant concern. Second, unlike CO2, UHS requires intermittent injection and withdrawal rates that need to respond dynamically to market demands. However, under repeated injections and withdrawals of hydrogen, subsurface formations are subject to mechanical stresses and strains, potentially compromising their integrity.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0004] Conventional strategies for containment include the use of polymer solutions. The viscosity of polymer solutions ty pically decreases with rising temperatures and is influenced by factors such as polymer concentration, molecular weight, salt, and hydrolysis. Recently, polymers have been developed that withstand high temperatures; such polymers include thermoviscosifying polymers (TVP), sulfonate polymers, and Schizophyllan biopolymers. However, conventional thermoviscosifying polymers have complex synthesis processes and high production costs. While some polymers exhibit reversible thermogelation behavior and possess thermal gelatinization characteristics, they only exhibit thermoviscosifying behavior at relatively high temperatures. In addition, the elastic properties of the polymer solutions result in high injection pressures, thereby impairing injectivity of the polymer solutions.

[0005] There is a need for new compositions, processes, and systems for subsurface containment or storage of a fluid.SUMMARY

[0006] Aspects of the present disclosure generally relate to compositions, processes, and systems for subsurface storage or containment of a fluid such as hydrogen, natural gas, methanol, or CO2, among others. The inventors found an innovative containment strategy based on time-dependent soft solids, for example, clay suspensions that may be utilized to reinforce natural subsurface seals and engineer flow barriers in order to, e.g., make subsurface storage of fluids scalable and geographically agnostic. Generally, the composition (a suspension) may be injected at its initial state — low viscosity and low elasticity — into aporous medium (e g., arock). The low viscosity and low elasticity enables easy pumping and injection of the suspension into the porous medium as well as easy targeted delivery. Once inside the targeted zone of the subsurface, the suspension may mature into a soft solid having a much higher viscosity and elasticity than its initial state, thereby acting as a flow barrier. The fluids contained by the matured suspension does not adversely affect the microstructure of the suspension. For example, the inventors found that, instead, hydrogen increases the suspension’s viscosity and elasticity. Moreover, the suspension enhances the porous medium’s compressive strength, while hydrogen exposure increases their stiffness and ductility. Further, the inventors found that the ability of rockPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC samples (porous media) saturated with the suspensions to contain higher injected gas pressures may be enhanced by aging at higher temperatures.

[0007] In an aspect, a composition for subsurface containment or storage of a fluid is provided. The composition includes an amount of a swellable clay in a range from about 1 wt% to about 5 wt% based on a total wt% of the composition, the total wt% of the composition equal to 100 wt%. The composition further includes an aqueous material.

[0008] In another aspect, a set-delayed composition for subsurface containment or storage of a fluid is provided. The set-delayed composition includes an amount of a swellable clay in a range from about 1 wt% to about 5 wt% based on a total wt% of the composition, the total wt% of the composition equal to 100 wt%. The set-delayed composition further includes an aqueous material.

[0009] In another aspect, a subsurface storage or containment system for a fluid is provided. The subsurface storage or containment system includes a porous medium. The subsurface storage or containment system further includes a composition comprising: an amount of a swellable clay in a range from about 1 wt% to about 5 wt% based on a total wt% of the composition, the total wt% of the composition equal to 100 wt%; and an aqueous material.

[0010] In another aspect, a subsurface storage or containment system for a fluid is provided. The subsurface storage or containment system includes a porous medium. The subsurface storage or containment system further includes hydrated interlayers of a swellable clay. The subsurface storage or containment system further includes hydrogen molecules disposed in interlayer spaces between the hydrated interlayers of the clay.

[0011] In another aspect, a process for forming a subsurface storage or containment system for a fluid is provided. The process includes introducing a composition described herein into a subsurface formation.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] So that the manner in which the above recited features of the present disclosure may be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate onlyPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC exemplary aspects and are therefore not to be considered limiting of its scope, may admit to other equally effective aspects.

[0013] FIG. 1 is a generalized illustration of selected aspects of the present disclosure.

[0014] FIG. 2 shows a frequency sweep of the 2 wt% clay aqueous suspension at a strain of y = 1 %. Prior to the test, it was confirmed by an amplitude sweep that the strain amplitude value selected was within the linear viscoelastic region.

[0015] FIG. 3 shows a general view and unit cells of smectite clay.

[0016] FIGS. 4A-4C: FIG. 4A shows a structure of smectite clay, FIG. 4B shows exfoliation of the smectite clay and disordering in aqueous media, and FIG. 4C shows formation of rigid structures involving clay-clay interactions, similar to a house-of-cards structure.

[0017] FIG. 5 is a phase diagram showing non-limiting clay concentrations and nonlimiting salt concentrations that may be utilized for compositions described herein.

[0018] FIG. 6 shows the effect of aging on the viscosity of a 2 wt% smectite clay aqueous suspension. The viscosities were measured y = 1 s '. The solid line represents a fitting to the data.

[0019] FIG. 7 shows an X-ray diffraction pattern of synthetic clay.

[0020] FIGS. 8A-8B: FIG. 8A shows the effect of aging on the shear stress of a 2 wt% clay aqueous suspension, and FIG. 8B shows the effect of aging on the shear stress of a 2000 ppm xanthan aqueous dispersion. The shear stresses were measured at y = 100 s '. The solid line represents a fitting to the data.

[0021] FIGS. 9A-9B: FIG. 9A shows shear stress of a 2 wt% clay aqueous suspension after one day of aging at room temperature and at 75°C, measured at y = 100 s '; and FIG. 9B shows the effect of aging on the shear stress of the 2 wt% clay aqueous suspension stored at room temperature, 45°C, and 75°C, measured at y = 100 s '

[0022] FIGS. 10A-10D show strain amplitude sweep test of a 2 wt% clay aqueous suspension at co = 6.28 rad / s: FIG. 10A shows results for the stored (aged) suspension after one day, FIG. 10B shows results for the stored (aged) suspension after four days, FIG. 10C shows results for the stored (aged) suspension after 30 days, and FIG. 10D shows results for the stored (aged) suspension after thirty days compared to the one-day aged sample.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0023] FIGS. 11A-11D show the effects of temperature and time on xanthan gum rheology: FIG. 11 A shows shear stress and viscosity decline of 2000 ppm xanthan aqueous dispersion measured at a constant shear rate of 100 s ' at 75 °C over 1 h; FIG. 1 IB shows shear stress values determined for a fresh 5000 ppm xanthan aqueous dispersion at room temperature and after 4 days stored at 75°C at constant shear rate of 100 s ': FIG. 11C shows data for strain amplitude sweep test for 3000 and 5000 ppm xanthan aqueous dispersions at co = 10 rad / s; and FIG. 11D shows strain amplitude sweep test of 5000 ppm xanthan aqueous suspension after being stored for 8 days at 75°C at co = 10 rad / s.

[0024] FIGS. 12A-12B: FIG. 12A shows a frequency sweep of a 2% clay aqueous suspension at a strain of y = 1%, and FIG. 12B shows a frequency sweep of aqueous xanthan dispersions at a strain amplitude of y = 10%. Prior to the test, it was confirmed by an amplitude sweep that the strain amplitude value selected was within the linear viscoelastic (LVE) region.

[0025] FIGS. 13A-13B show a 2 wt% clay aqueous suspension aged for 3 and 5 months at room temperature and 45°C: FIG. 13A shows a frequency sweep at a strain of y = 1%, and FIG. 13B shows a strain amplitude sweep test at co = 6.28 rad / s.

[0026] FIG. 14 shows microstructure destruction and construction of 2 wt% clay suspension.

[0027] FIGS. 15A-15B: FIG. 15A shows a flow' curve of the 2 wt% clay aqueous suspension. Data points were obtained from constant shear rate tests; and FIG. 15B shows creep tests for the 2 wt% clay aqueous suspension for a 1-h duration.

[0028] FIGS. 16A-16B: FIG. 16A shows a flow curve of the 0.14 wt% Carbopol aqueous dispersion, with the solid line represents the best Herschel-Bulkley fit; and FIG. 16B show s creep tests for the Carbopol solution for a 1-h duration.

[0029] FIGS. 17A-17B show 2 wt% clay aqueous suspensions aged for 1 week at 75°C and exposed to H2 and N2 at 10 bar: FIG. 17A shows strain amplitude sweep test data at co = 6.28 rad / s, and FIG. 17B shows shear stress data at y = 100 s '.

[0030] FIGS. 18A-18B show deviatoric stress Aoa versus the axial strain (right) and radial strain (left) responses of Hanna sandstone plugs under the confining pressures of 5 MPa (FIG. 18A), and 10 MPa (FIG. 18B).PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0031] FIG. 19A-19B show a normal image (FIG. 19A) and backscater image (FIG. 19B) of the clay.

[0032] FIG. 20 shows results from scanning electron microscopy (SEM)-microprobe analysis of the clay.

[0033] FIG. 21 A shows the evolution of G' and G” over time at a stress amplitude of 3 Pa, which is below the dynamic yield stress of 2% clay suspension.

[0034] FIG. 21B shows the evolution of G' and G" over time at a strain amplitude of 0.1% below the yield strain of 5000 ppm xanthan aqueous dispersion.

[0035] FIG. 22 shows a non-limiting containment strategy according to at least one aspect of the present disclosure.

[0036] FIG. 23 A shows TGA curves of Laponite powder as received.

[0037] FIG. 23B shows TGA curve of Laponite powder dried at 120°C for 4 hours.

[0038] FIG. 23C shows a comparison of TGA curves for the as received Laponite powder and dried Laponite powder samples.

[0039] FIG. 24 shows a schematic sequence of rheological tests conducted on the samples for Example 4.

[0040] FIGS. 25A-25C shows creep test results for three Laponite suspensions tested on the 16th day of aging at room temperature: FIG. 25 A (2 wt%); FIG. 25B (2.5 wt%); and FIG. 25C (3 wt%).

[0041] FIG. 26 shows selected fabrication operations for fabricating microfluidic chips.

[0042] FIG. 27A is an illustration of evaporation during the aging process resulting in gaps between aged Laponite and grain walls.

[0043] FIG. 28B is an illustration of a properly aged Laponite suspension, which remains nearly transparent, ensuring effective containment.

[0044] FIG. 28 shows an experimental setup for hydrogen injection into microchips.

[0045] FIGS. 29A-29C show data for the evolution of steady-state shear stress of three Laponite suspensions aged at different temperatures over 30 days: FIG. 29A (2 wt%); FIG. 29B (2.5 wt%); and FIG. 29C (3 wt%).

[0046] FIGS. 30A-30C show results of strain amplitude sweep tests for three Laponite suspensions aged at 45°C and 75°C, tested on the 4th day of aging: FIG. 30A (2 wt%); FIG. 30B (2.5 wt%); and FIG. 30C (3 wt%).PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0047] FIGS. 31A-3 II show data for oscillation frequency sweep tests: Evolution of G' over aging time for different concentrations and temperatures: FIGS. 31A-31C (2 wt% Laponite suspension); FIGS. 31D-31F (2.5 wt% Laponite suspension); and FIGS. 31G-31I (3 wt% Laponite suspension).

[0048] FIG. 32A shows dimensions of the microfluidic pattern design.

[0049] FIG. 32B shows calculated permeability' of the pore network within the microfluidic device.

[0050] FIG. 33 shows a pressure profile for hydrogen injection into a microfluidic device containing 2 wt% Laponite suspension aged at 75°C and tested on various days of aging.

[0051] FIG. 34 shows a pressure profile for hydrogen injection into a microfluidic device containing 2.5 wt% Laponite suspension aged at 75°C and tested on various days of aging.

[0052] FIGS. 35A-35D show aged 2.5 wt% Laponite suspension in the microfluidic device: FIG. 35A (before breakthrough); FIG. 35B (after breakthrough (day 1 of aging)); FIG. 35C (after breakthrough (day 4 of aging)); and FIG. 35D (after breakthrough (day 7 of aging)).

[0053] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one aspect may be beneficially incorporated in other aspects without further recitation.DETAILED DESCRIPTION

[0054] Aspects of the present disclosure generally relate to compositions, processes, and systems for subsurface storage or containment of a fluid. As used herein, a “composition"’ may include component(s) of the composition, reaction product(s) of two or more components of the composition, a remainder balance of remaining starting component(s), or combinations thereof. Compositions of the present disclosure may be prepared by any suitable mixing process.

[0055] Applications of aspects described herein may include: creating subsurface reservoirs to contain and store energy carriers (e.g., fluids such as hydrogen, natural gas, or methanol, among others) and help produce geologic hydrogen economically; strengtheningPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC natural subsurface seals and creating engineered barriers, making even previously unsuitable geologic structures viable energy (e.g., fluids such as hydrogen, natural gas, methanol, etc.) storage sites; and managing challenges posed by geological discontinuities, such as faults and fractures, to maintain formation seal integrity.

[0056] Aspects described herein may be utilized to store any suitable fluid, such as a fluid used as an energy source. Suitable liquids may include, for example, hydrogen (H2), carbon dioxide (CO2). natural gas, methanol, petroleum-based fluids, bio-based fluids, fossil fuel-based fluids, or combinations thereof. Such fluids may include those in the gaseous form and / or liquid form. Natural gas may include gaseous hydrocarbons such as methane, ethane, propane, butane, or combinations thereof. Natural gas may optionally include CO2, N2, hydrogen sulfide (H2S), helium, or combinations thereof.

[0057] Water, which is a viscous fluid, has a constant viscosity at constant temperature and the viscosity does not increase over time. Water does not show elastic response. A material, such as stainless steel, is an elastic solid, and its elasticity is constant at constant temperature and does not increase over time. Stainless steel does not show viscous response. Compositions described herein — for example, clay suspensions, possess both properties: shows some portion of a viscous response and some portion of an elastic response. Also, the compositions are time-dependent material and shows aging, whereby even at constant temperature, its viscosity and elasticity increases over time. The compositions, when prepared, may be very fluid-like; and as time passes and depending on the temperature, the composition may become more solid-like (for example, viscosity and elasticity increases).

[0058] For compositions described herein, various properties of the compositions — such as viscosity — may depend on time, shear rate, temperature, concentration of clay, or combinations thereof, among other parameters. In many cases described herein, viscosity was measured at a shear rate of 100 s ', because, for example, mixing of the composition, pumping of the composition, and / or introducing the composition into a subsurface formation may occur at high shear rates. When inside the porous media of a subsurface formation and at rest, viscosity of the composition will be higher because, for example, the shear rate is lower.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0059] Elasticity, and the elasticity modulus measurement, of the composition may be measured using a frequency sweep at a linear viscoelastic region, which means it is a property without altering the microstructure. Also, the elasticity modulus may be measured from the strain sweep at the linear viscoelastic region (the plateau where the data are strainindependent). Static yield stress of the composition is the stress or the pressure needed to exert on the composition to make the solid-like state of the composition to flow. Static yield stress may be measured using creep tests over 1 hour periods.

[0060] Non-limiting advantages of aspects described herein may include:

[0061] (a) Compositions of the present disclosure may be a high elasticity material inside a porous media. Here, during injection into a porous media, the elastic modulus may be about 1 Pascal (Pa) or lower, and depending on the aging time and aging temperature, the elastic modulus of the composition inside the porous media may increase to about 100 Pa or more, such as about 1,000 Pa or more.

[0062] (b) Compositions of the present disclosure may be very stable over time, even at high temperatures. Conventional technologies, including polymer solutions (such as xanthan gum), are not stable over time.

[0063] (c) Compositions of the present disclosure may be utilized to for containment or storage of hydrogen gas. Hydrogen does not adversely affect the microstructure of the composition. In fact, the viscosity7and / or elasticity of the composition of may increase in the presence of hydrogen.

[0064] (d) Compositions of the present disclosure may be relatively inexpensive and simple to produce in contrast to conventional technologies.Compositions

[0065] Aspects of the present disclosure generally relate to compositions. Such compositions may be used for any suitable application, such as, for subsurface storage or containment of any suitable fluid such as a fluid used as an energy source, such as H2, natural gas, methanol, CO2, or combinations thereof, among other fluids.

[0066] Compositions of the present disclosure may include clay and an aqueous material. The composition may be in the form of a suspension, a dispersion, or a solution. The composition may be utilized for subsurface containment or storage of a fluid. The composition may be characterized as a time-dependent soft solid. For example, thePCT Patent ApplicationAttorney Docket No.: UWYO-0130PC composition may be a material that exhibits properties that change over time due to, for example, its viscoelastic nature. The dependency may be observed in phenomena such as stress and creep. The change in the compositions properties may depend on aging (an amount of time after which the composition is formed), temperature, or combinations thereof. For example, a property of the composition such as steady-state shear viscosity, elastic modulus, density7, or combinations thereof may change over time. The composition may have non-Newtonian characteristics.

[0067] Any suitable clay may be utilized. The clay may be natural, synthetic, semisynthetic, or combinations thereof. The clay may be swellable, such as upon exposure to an aqueous material. The clay may be in the form of particles.

[0068] The clay may include a smectite clay. The smectite clay may include layered silicates, such as layered silicate sheets. Smectite is a mixture of swelling sheet silicates. The clay may include laponite (a synthetic smectite clay), synthetic montmorillonite, fluorohectorite, or a combination thereof.

[0069] The smectite clay may include a lithium sodium magnesium silicate. The smectite clay may have the general chemical formula represented by formula (I):Na+a[Mg6-«LiaSi802o(OH)4] (I), wherein a of formula (I) is the degree of isomorphous substitution of Li+for Mg2+. In some aspects, which may be combined with other aspects, the smectite clay may have the chemical formula Nao.7[Si8Mg55Lio.3H4024] or Sis.oo(Mg5.45Lio.4o)H4024Nao.75. The smectite clay may include laponite. The clay may include layered silicate sheets. Mg may be at least partially substituted with Al, Fe, or both. Additionally, or alternatively, Si may be at least partially substituted with Al. Additionally, or alternatively, Na may be at least partially substituted with K, Li, Ca, Mg, NFL, H, or combinations thereof.

[0070] The clay may be surface modified with one or more organic molecules for use in, e g., non-aqueous environments. Additionally, or alternatively, the clay may be doped with a transition metal, such as Ti, Zn, or combinations thereof. Additionally, or alternatively, the clay may be doped with a rare earth metal, such as Ce, La, or combinations thereof.

[0071] The clay may include a three-layer 2: 1 TOT crystallographic structure comprising two silica tetrahedral (T) layers and 1 octahedral (O) central layer. The twoPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC silica tetrahedral layers of the TOT crystallographic structure may be electrostatically cross-linked via the octahedral central layer. The three layers may be separated by an interlayer (or free space) which may host hydrated cations and / or water molecules). Swelling of the clay may be due to incorporation of water and / or hydrated cations in the interlayer space.

[0072] The clay may have any suitable average particle size. An average particle size of the clay may be in a range from about 10 nm to about 100 nm, such as from about 15 nm to about 50 nm, such as from about 20 nm to about 30 nm. Any of the foregoing numbers may be used singly to describe an open-ended range or in combination to describe a close- ended range.

[0073] The clay may have any suitable bulk density. A bulk density of the clay may be in a range from about 700 kg / m3to about 1,300 kg / m3, such as from about 800 kg / m3to about 1,200 kg / m3, such as from about 900 kg / m3to about 1,100 kg / m3, such as about 1,000 kg / m3. Any of the foregoing numbers may be used singly to describe an open-ended range or in combination to describe a close-ended range.

[0074] The clay may have any suitable particle density. A particle density of the clay may be in a range from about 2.5 g / cm3to about 2.6 g / cm3, such as about 2.55 g / cm3. Any of the foregoing numbers may be used singly to describe an open-ended range or in combination to describe a close-ended range.

[0075] The clay may have any suitable molecular weight, accounting for the clay’s crystalline lattice and repeated units. A molecular weight of the clay may be in a range from about 2,000 g / mol to about 6,000 g / mol, such as from about 3,000 g / mol to about 5,000 g / mol, such as about 4,000 g / mol, or in a range from about 2,000 g / mol to about 2,500 g / mol, such as from about 2,100 g / mol to about 2,300 g / mol, such as about 2,286.9 g / mol. Any of the foregoing numbers may be used singly to describe an open-ended range or in combination to describe a close-ended range.

[0076] Any suitable aqueous material may be utilized such as water, distilled water, brine, or combinations thereof. The aqueous material may include one or more salts. The one or more salts include a cation and an anion. The cation and / or the anion may be monoatomic or polyatomic. Monoatomic cations may include an alkali metal (e.g., Li, K, Rb, and Cs), an alkaline earth metal (e.g., Be, Mg, Ca, Sr, and Ba), a transition metal (Fe,PCT Patent ApplicationAttorney Docket No.: UWYO-0130PCZn, Mn), or combinations thereof. Polyatomic cations may include such as ammonium (NR4+, wherein each R is independently H or alkyl), pyridinium, or combinations thereof. Anions may include one or more elements from Group 15-Group 17 of the periodic table of the elements, such as N, P, S, O, F, Cl, Br, I, or combinations thereof. Monoatomic anions may include a halide (F, Cl, Br, and I), oxides, or combinations thereof. Polyatomic anions may include a carbonate, a nitrate, a sulfate, a sulfonate, a tosyl, a trifluoromethesulfonate, a phosphate, a phosphonate, a hydroxide, or combinations thereof. Other ions are contemplated. In a solution or suspension, the salt(s) may exist as one or more ions. For example, one or more anions (e.g., Cl, Br, I, Sr, et cetera) and one or more cations (e.g., Na, K, Ca, Mg, et cetera) may exist in the solution or suspension.

[0077] Illustrative, but non-limiting, examples of salts may include sodium chloride (NaCl). sodium bromide (NaBr). sodium iodide (Nal). sodium sulfate (Na2SO4), potassium chloride (KC1), potassium bromide (KBr), potassium iodide (KI), potassium nitrate (KNCh), calcium chloride (CaCh), calcium bromide (CaBn), calcium iodide (Cab), calcium sulfate (CaSO4), calcium oxide (CaO), magnesium chloride (MgCh), magnesium sulfate (Mg2SO4), and / or Mg(OH)2, among others. One or more of these salts may be hydrates, e.g., hexahydrates.

[0078] Compositions described herein may include any suitable concentration of salt(s). A concentration of salt(s) in the composition may be in a range from about 1 / 105M (about 0.01 mM) to about 1 / 102M (about 10 mM), such as from about 2.5 / 104M (about 0.25 mM) to about 7.5* 1(L3M (about 7.5 mM). such as from about 5x 104M (about 0.5 mM) to about 5 / IO3M (about 5 mM), such as from about 7.5 / 104M (about 0.75 mM) to about 2.5 / 103M (about 2.5 mM), such as about 1 x I03M (about 1 mM). Any of the foregoing numbers may be used singly to describe an open-ended range or in combination to describe a close-ended range.

[0079] Additionally, or alternatively, compositions described herein may include a concentration of salt (Cs, in units of Molarity) in the composition and a concentration of smectite (Cw, in units of wt%) that follows the Cs~Cw phase diagram show n in FIG. 5. In FIG. 5, various regions — IL, IG, NG, and F — are shown. IL refers to isotropic liquid phase, IG refers to isotropic gel (or glass) phase, NG refers to nematically ordered gel, and F refers to flocculation. FIG. 5 is discussed in the Examples section. In various aspects, which mayPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC be combined with other aspects, compositions described herein may be located in the IG phase / region of the Cs-Cw phase diagram shown in FIG. 5.

[0080] Compositions described herein may have any suitable pH. For example, the composition may have a pH of about 8 or more, such as a pH in a range from about 8 to about 12, such as from about 9 to about 11, such as from about 9.5 to about 10.5. Any of the foregoing numbers may be used singly to describe an open-ended range or in combination to describe a close-ended range.

[0081] Compositions described herein may include any suitable amount of clay. An amount of clay in the composition may be in a range from about 0. 1 wt% to about 5 wt%, such as from about 0.5 wt% to about 5 wt%, such as from about 1 wt% to about 5 wt%, such as from about 1 wt% to about 4.5 wt%, such as from about 1 wt% to about 4 wt%, or from about 1.5 wt% to about 4.5 wt%, such as from about 1.5 wt to about 3.5 wt%, such as from about 2 wt% to about 3 wt%, such as from about 2.5 wt% to about 3 wt% based on a total wt% of the composition. The total wt% of the composition is equal to 100 wt%. Alternatively, an amount of clay in the composition may be in a range from about 1 wt% to about 3 wt%, such as from about 1.5 wt% to about 2.5 wt%, such as about 2 wt% based on the total wt% of the composition. Alternatively, an amount of clay in the composition may be in a range from about 1.5 wt% to about 3 wt%, such as from about 1.6 wt% to about 2.9 wt%, such as from about 1.7 wt% to about 2.8 wt%, such as from about 1.8 wt% to about 2.7 wt%. such as from about 1.9 wt% to about 2.6 wt%, such as from about 2 wt% to about 2.5 wt%, such as from about 2. 1 wt% to about 2.4 wt%, such as from about 2.2 wt% to about 2.3 wt% based on the total wt% of the composition. Any of the foregoing numbers may be used singly to describe an open-ended range or in combination to describe a close-ended range.

[0082] Compositions described herein may include any suitable amount of aqueous material. An amount of aqueous material in the composition may be in a range from about 95 wt% to about 99.9 wt%, such as from about 95 wt% to about 99.5 wt%, such as from about 95 wt% to about 99 wt%, such as from about 95.5 wt% to about 99 wt%, such as from about 96 wt% to about 99 wt%, or from about 95.5 wt% to about 98.5 wt%, such as from about 96.5 wt to about 98.5 wt%, such as from about 97 wt% to about 98 wt%, such as from about 97 wt% to about 97.5 wt% based on the total wt% of the composition, thePCT Patent ApplicationAttorney Docket No.: UWYO-0130PC total wt% of the composition equal to 100 wt%. Alternatively, an amount of aqueous material in the composition may be in a range from about 97 wt% to about 99 wt%, such as from about 97.5 wt% to about 98.5 wt%, such as about 98 wt% based on the total wt% of the composition. Alternatively, an amount of aqueous material in the composition may be in a range from about 97 wt% to about 98.5 wt%, such as from about 97.1 \\1% to about98.4 wt%, such as from about 97.2 wt% to about 98.3 wt%, such as from about 97.3 wt% to about 98.2 wt%, such as from about 97.4 wt% to about 98.1 wt%, such as from about97.5 wt% to about 98 wt%, such as from about 97.6 wt% to about 97.9 wt%, such as from about 97.7 wt% to about 97.8 wt%, based on the total wt% of the composition. Any of the foregoing numbers may be used singly to describe an open-ended range or in combination to describe a close-ended range.

[0083] The clay of the composition may be mesoporous. At least a portion of the clay may be in the form of clay platelets. The clay platelets may be disc-shaped or substantially disc-shaped. The clay platelets may have any suitable average thickness, such as in a range from about 0.8 nm to about 1.2 nm, such as from about 0.9 nm to about 1 nm, such as about 0.92 nm. The clay platelets may have any suitable average diameter, such as about 50 nm or less, such as in a range from about 10 nm to about 40 nm, such as from about 20 nm to about 30 nm, such as about 25 nm.

[0084] At least a portion of the clay in the composition may be in the form of nanosized clay platelets. Clay platelets in an aqueous media (aqueous material) are described further herein with respect to FIGS. 4A-4C. At least a portion of the nanosized clay platelets in the composition may be disordered, such as in an edge-to-face fashion at the mesoscopic level, optionally resulting in a continuous structure throughout the composition, while avoiding nematic gel formation, flocculation, and isotropic liquid formation. Additionally, or alternatively, at least a portion of the nanosized clay platelets may be mesostructured when a pH of the composition is about 8 or higher, such as a pH in a range from about 9 to about 11. Additionally, or alternatively, at least a portion of the nanosized clay platelets in the composition may be crystalline.

[0085] Face-to-face stacking is typically observed in dry form. Once in suspension, the dominant stacking will be face-to-rim (e.g., edge-to-face), which results in the selforganizing backbone of the soft-solid. Accordingly, compositions described herein may bePCT Patent ApplicationAttorney Docket No.: UWYO-0130PC free of, or substantially free of, face-to-face stacking of the nanosized clay platelets. Free of face-to-face stacking of the nanosized clay platelets means that an undetectable amount of the nanosized clay platelets are stacked face-to-face in the composition. Substantially free of face-to-face stacking of the nanosized clay platelets means that less than 3% of the nanosized clay platelets are stacked face-to-face in the composition. Additionally, or alternatively, compositions described herein may be free of, or substantially free of, a stacked nanolayer morphology of the nanosized clay platelets. Free of stacked layer morphology means that an undetectable amount of the nanosized clay platelets are in a stacked layer morphology. Substantially free of stacked layer morphology means that less than 3% of the nanosized clay platelets are oriented in a stacked layer morphology7in the composition.

[0086] In some aspects, which may be combined with other aspects, at least a portion of the clay in the composition may be in the form of disordered edge-to-face nanolayers, and the disordered edge-to-face nanolayers may have a thickness in a range from about 0.8 nm to about 1.2 nm.

[0087] In some aspects, which may be combined with other aspects, a composition may include from about 1.8 wt% to about 2.7 wt% of the clay and have a pH in a range from about 9 to about 11, such as about 10. In these and other aspects, a concentration of salt in the composition may be about 9 / I O2M or less (about 0.09 M or less), such as in a range from about U K)4M to about 9x I O2M (from about 0.0001 M to about 0.09 M), such as from about 5 / 104M to about 5 / I O2M (from about 0.0005 M to about 0.05 M), such as from about I / 103M to about 1 / 102M (from about 0.001 M to about 0.01 M).

[0088] Compositions described herein may be utilized to store a fluid such as a fluid used as an energy source. Such fluids may include gases such as hydrogen (H2), carbon dioxide (CO2), natural gas. methanol, petroleum-based fluids, bio-based fluids, fossil fuelbased fluids, or combinations thereof. Natural gas may include gaseous hydrocarbons such as methane, ethane, propane, butane, or combinations thereof. Natural gas may optionally include CO2, N2, hydrogen sulfide (H2S), helium, or combinations thereof.

[0089] Upon exposure of the composition to one or more of the fluids to be stored (such as H2), the fluid may intercalate in and / or between two or more layers of the clay structure (e.g., two or more layers of the TOT crystallographic structure) and increase the viscosityPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC and / or elasticity of the composition relative to the viscosity and / or elasticity of the composition prior to exposure to the fluid.

[0090] As described herein, aging and / or temperature may influence properties of the composition. Aging generally refers to curing. Aging / curing may be performed at any suitable temperature as described herein.

[0091] The composition may be characterized as having an improved flow barrier to a fluid (e.g., the fluid to be stored, such as H2) upon exposure of the composition to a temperature of greater than ambient temperature (e.g., a temperature greater than 20°C, such as 45°C or 75°C) relative to exposure of the same composition to a temperature of ambient temperature (20°C). Additionally, or alternatively, the composition may be characterized as having an improved flow barrier to a fluid (e.g., fluid to be stored, such as H2) after aging the composition for a period of more than 24 hours than aging the same composition for a period of less than 5 hours.

[0092] The composition may be capable of remaining in a pumpable or injectable fluid state for a period of time of about 1 day or less, such as about 15 hours or less, such as about 10 hours or less. Capable of being pumpable or injectable is determined based on the viscosity. The composition is pumpable or injectable when the steady-state shear viscosity of the composition is about 0.1 Pa s (100 cP) or less. Upon aging and / or exposure to adequate temperature (for example, 20°C or higher), the composition may serve as a container for the fluid and / or a flow barrier for the fluid.

[0093] As described herein, properties of the compositions described herein may be time-dependent. Such properties may include, for example, density, steady-state shear viscosity, elastic modulus, or combinations thereof, among other properties.

[0094] The compositions may be aged at any suitable temperature, such as a temperature in a range from about 10°C to about 100°C, such as from about 20°C to about 100°C, such as from 50°C to about 100°C, such as from about 60°C to about 90°C, such as from about 65°C to about 85°C, such as from about 70°C to about 80°C, such as about 75°C, or in a range from about 30°C to about 60°C, such as from about 35°C to about 55°C, such as from about 40°C to about 50°C, such as about 45°C. or in a range from about 10°C to about 30°C, such as from about 15°C to about 25°C, such as about 20°C.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0095] Prior to injection, the composition may be cured for any suitable duration. For example, prior to injection, the composition may be cured for about 7 days or less (at 20°C).

[0096] Compositions of the present disclosure may have any suitable initial density. The initial density of the composition refers to the density of the composition shortly after preparation (e.g., aging the composition for 1 hour). An initial density of the composition may be in a range from about 1 g / mL to about 1.3 g / mL, such as from about 1.05 g / mL to about 1.2 g / mL, such as about 1.1 g / mL. or from about 1 g / mL to about 1.1 g / mL.

[0097] After aging (for example, aging the composition at 20°C for t=4 days), the composition may have a higher density than that of the initial density. Additionally, or alternatively, cry stallinity of the composition may change upon aging. For example, a structure of the composition after aging for 4 days at 20°C is more cry stalline than the structure of the composition after aging for 24 hours at 20°C.

[0098] The composition may initially have one or more of the following properties measured (initially refers to a time period of aging the composition at 20°C for t=l hour):

[0099] (a) The composition may have a steady-state shear viscosity in a range from about 0.001 Pascal-second (Pa s) to about 0.1 Pa s, such as from about 0.005 Pa s to about 0.07 Pa s, such as from about 0.01 Pa s to about 0.05 Pa s, such as from about 0.015 Pa s to about 0.036 Pa s, such as from about 0.018 Pa- s to about 0.031 Pa s for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 20°C for 1=1 hour). Steady-state shear viscosity is measured as described in the Examples.

[0100] (b) The composition may have an elastic modulus in the linear viscoelastic region in a range from about 0.4 Pa to about 10 Pa, such as from about 1 Pa to about 4 Pa for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 20°C for t=l hour). Elastic modulus is measured as described in the Examples.

[0101] After aging the composition for 24 hours or more, the composition may be in the form of a soft solid with a higher steady-state shear viscosity and / or higher elastic modulus than a steady-state shear viscosity and / or elastic modulus of the composition that is aged for 1 hour.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0102] The composition may have an elastic modulus in the linear viscoelastic region in a range from about 8 Pa to about 12 Pa, such as from about 9 Pa to about 11 Pa for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 75°C for t=24 hours).

[0103] After injection into, for example, a formation the composition may still age.

[0104] After aging the composition for 30 days, the composition may have one or more of the following properties:

[0105] (a) The composition may be characterized as a soft solid. A composition may be defined as a soft solid when under small-amplitude oscillatory shear and after structural recovery from flow, its storage modulus (G') exceeds its loss modulus (G") by a substantial margin, typically with G'»G" and G'7G' < 0.3. In this regime, the materials exhibit a predominantly elastic response, support shear without flowing, and show time-dependent structural buildup characteristic of arrested, jammed microstructures.

[0106] (b) The composition may be characterized as having a steady-state shear viscosity in a range from about 0. 1 Pa- s to about 0.25 Pa- s, such as from about 0.11 Pa- s to about 0.22 Pa s, such as about 0.12 Pa s or about 0.22 Pa s for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 20°C for t=30 days at a shear rate (y) of 100 s1).

[0107] (c) The composition may be characterized as having an elastic modulus in the linear viscoelastic region in a range from about 90 Pa to about 220 Pa, such as from about 95 Pa to about 200 Pa, such as from about 100 Pa to about 205 Pa, such as from about 1 10 Pa to about 210 Pa for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 20°C for t=30 days at an angular frequency of oscillation of 0.01 rad / s and a shear strain of 1%);

[0108] (d) The composition may be characterized as having a steady-state shear viscosity in a range from about 0.15 Pa s to about 0.70 Pa s, such as from about 0.18 Pa s to about 0.60 Pa s, such as from about 0.39 Pa s to about 0.66 Pa s, such as from about 0.4 Pa- s to about 0.68 Pa- s for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 45°C for t=30 days at a shear rate (y) of 100 s ').PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0109] (e) The composition may be characterized as having an elastic modulus in the linear viscoelastic region in a range from about 420 Pa to about 660 Pa, such as from about 440 Pa to about 650 Pa, such as from about 430 Pa to about 640 Pa, such as from about 420 Pa to about 630 Pa for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 45°C for t=30 days at an angular frequency of oscillation of 0.01 rad / s and a shear strain of 1%).

[0110] (1) The composition may be characterized as having a steady-state shear viscosity in a range from about 0.38 Pa s to about 1.5 Pa s, such as from about 0.4 Pa s to about 1.2 Pa s, such as from about 0.5 Pa s to about 1.3 Pa s, such as from about 1.1 Pa s to about 1.4 Pa s for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 75°C for t=30 days at a shear rate (y) of 100 s ' ).[OHl] (g) The composition may be characterized as having an elastic modulus in the linear viscoelastic region in a range from about 550 Pa to about 1,250 Pa, such as from about 550 Pa to about 1,225 Pa, such as from about 600 Pa to about 1.200 Pa, such as from about 650 Pa to about 1,175 Pa, such as from about 675 Pa to about 1,150 Pa, such as from about 700 Pa to about 1,100 Pa, such as from about 708 Pa to about 1,066 Pa for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 75°C for t=30 days at an angular frequency of oscillation of 0.01 rad / s and a shear strain of 1%).

[0112] Compositions of the present disclosure may have any suitable breakthrough pressure. Breakthrough pressure is a pressure at which the composition fails. After aging the composition at 75°C for t=l 8 days, the composition may be characterized as having a breakthrough pressure, across a 38.38 mm-long porous medium, in a range from about 18 psi to about 405 psi (about 0.12 MPa to about 2.79 MPa), such as from about 68 psi to about 382 psi (about 0.47 MPa to about 2.63 MPa), such as from about 88 psi to about 362 psi (about 0.61 MPa to about 2.50 MPa), such as from about 99 psi to about 351 psi (about 0.68 MPa to about 2.42 MPa), such as from about 105 psi to about 346 psi (about 0.724 MPa to about 2.39 MPa) for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt%. Breakthrough pressure is measured as described in the Examples.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0113] With breakthrough pressure, the scale of the experiments should be considered, as the length of the microfluidic device patterns where the composition was aged is only 38.38 mm. When extrapolating to reservoir scale and assuming a linear relationship between pressure drop (AP) and the length of the porous medium, as described by Darcy’s law, a thicker geobarrier could proportionally withstand higher pressures. For example, if 18-day aged composition withstands about 105 psi (about 0.724 MPa) and about 346 psi (about 2.39 MPa), respectively, over 38.38 mm, then a 3-meter-thick barrier may withstand approximately 8,207 psi (about 56.59 MPa) and 27,045 psi (about 186.47 MPa). These projected values are significantly higher than typical pressure gradients expected in underground hydrogen storage settings.

[0114] Compositions of the present disclosure may be characterized as a set-delayed composition. As used herein, a set-delayed composition is a composition formulated to remain in a fluid state for an extended period before gelling into a solid or semi-solid state (soft solid), thereby providing time for placement and manipulation, including in challenging environments such as subsurface formations.

[0115] For subsurface use. fluid samples from the target subsurface formation may be analyzed to ensure, e.g., desired thixotropic and time-dependent behavior in the subsurface. Accordingly, properties such as pH, elasticity, and / or viscosity, and / or components of the composition such as amount of salt and / or amount of clay, etc., may be adjusted for compositions described herein. Because subsurface fluids can have varying characteristics, such as different salinity levels and pH, injecting a clay suspension into fluid-saturated porous media may alter its properties, potentially placing it in a different region of the phase diagram than intended. Therefore, sampling the formation fluids prior to clay injection may help adjust the suspension's properties to ensure it behaves as expected.Systems

[0116] Aspects described herein also generally relate to subsurface storage or containment systems for a fluid such as those fluids described herein utilized for energy sources (e.g., H2, CO2, natural gas, methanol, or combinations thereof, among others). Subsurface storage or containment systems for a fluid may include a porous medium (e.g., a rock) and a composition of the present disclosure.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0117] Any suitable porous media may be utilized such as geomaterials. Geomaterials may include consolidated and unconsolidated sand, soil, conventional rocks (e.g., conventional rocks of sandstone and carbonate types), as well as any other suitable geomaterials from geological formations that may be considered unconventional. The porous media may include quartz, calcite (CaCCh), feldspar, dolomite (MgCCh), silica, illite, apatite, muscovite, rutile, gypsum, anhydrite, chamosite, clinochlore, zircon, biotite, pyrite, expansible clays, kaolinite, mica minerals, trace minerals, organic matter, or combinations thereof. The porous media may include rock.

[0118] The composition of the system include any suitable composition described herein. The composition of the system may serve to enhance various characteristics of the porous medium (rock) to which it touches and / or saturates. For example, as the composition ages (whether or not the aging is performed at higher than ambient temperature), the viscosity and yield strength (yield stress) of the composition may increase, thereby enhancing the compressive strength of saturated rock.

[0119] In some aspects, which may be combined with other aspects, a subsurface storage or containment system for a fluid may include a porous medium, hydrated interlayers of a swellable clay, and molecules of the fluid to be stored (e.g., hydrogen molecules) disposed in interlayer spaces between the hydrated interlayers of the clay. Here, the hydrated interlayers of the clay may be a result of the exposing the swellable clay to aqueous material (e.g.. forming the composition). These interlayer regions may form, as least in part, through electrostatic interactions and hydrogen-bonding between adjacent monolayers of the hydrated clay. Additionally, or alternatively, the negatively charged surfaces of the clay particles may interact with positively charged ions in the water, resulting in interparticle attractions. As clay particles hydrate into individual layers, subsequent ordering of the layers may give rise to the interlayers. The hydrated interlayers may allow guest molecules (such as hydrogen molecules) to be accommodated in interlayer spaces between the interlayers. For example, by exposing the composition to the fluid to be stored, molecules of the fluid to be stored may diffuse into the interlayer spaces.Processes

[0120] Aspects described herein also generally relate to processes for forming a subsurface storage or containment system for a fluid such as those fluids described hereinPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC utilized for energy sources (e.g., H2, CO2, natural gas, methanol, or combinations thereof, among others). An example subsurface storage or containment system is shown in FIG. 22, described below.

[0121] The process may include introducing any suitable composition described herein into a subsurface formation. The composition may be introduced in a vertical well and / or horizontal well of the subsurface formation. Introducing may include, for example, flowing, injecting, and / or pumping. The composition may be introduced into a target zone of the subsurface formation. Once delivered into the target zone, the composition matures into a soft solid with higher viscosity and yield stress inside the porous medium.

[0122] As described herein, compositions of the present disclosure may have low steady-state shear viscosity and / or low elasticity' prior to aging, enabling injectability. For example, prior to the injection (e.g., soon after suspension preparation (t = 1 hour)), the composition may have a steady-state shear viscosity (measured after aging at 20°C for t=l hour) in a range from about 0.001 Pascal-seconds (Pa s) to about 0.1 Pa s for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% measured at a shear rate (y) of 100 s f For comparison, water's viscosity is 0.001 Pa s.

[0123] After the injection, the composition may age inside a target zone of the subsurface formation into a soft solid. The soft solid may have a higher viscosity and / or higher elasticity' than a viscosity and / or elasticity of the composition prior to injection. For example, after aging for 30 days (t=30 days), the soft solid may have a steady -state shear viscosity (measured after aging at 20°C for t=30 days at a shear rate (y) of 100 s ') in a range from about 0. 1 Pa- s to about 1.5 Pa s for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt%. Additionally or alternatively, and after the aging, the soft solid may have an elastic modulus in the linear viscoelastic region (measured after aging at 75°C for t=30 days at an angular frequency of oscillation of 0.01 rad / s and a shear strain of 1%) in a range from about 90 Pa to about 1,250 Pa for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt%.

[0124] As used herein, “room temperature” refers to 20°C.

[0125] Aspects of the present disclosure may be further understood by the following non-limiting examples. The following non-limiting examples are put forth so as to providePCT Patent ApplicationAttorney Docket No.: UWYO-0130PC those of ordinary skill in the art with a complete disclosure and description of how to make and use aspects of the present disclosure, and are not intended to limit the scope of aspects of the present disclosure.Examples

[0126] The Examples show preparation and use of compositions (suspensions) described herein in, for example, processes and systems of the present disclosure. The Examples also describe rheological and geomechanical properties of the compositions of the present disclosure. Compositions of the present disclosure were compared to conventional aqueous polymer dispersions commonly used in the industry, such as xanthan gum and Carbopol .

[0127] As used herein, G' refers to storage modulus, and G" refers to loss modulus.Example 1A: Containment

[0128] Herein is proposed a disruptive containment innovation centered on a composition that includes a swellable clay and water, such as a synthetic smectite clay suspension. As described herein, a smectite clay suspension (swellable clay and water) maybe designed to reinforce natural subsurface seals and create engineered flow barriers (See FIG. 1). Once in the target zone, a smectite clay suspension described herein (e.g., a 1.5 wt% to about 3 wt% smectite clay suspension) may significantly7reduce hydrogen diffusion rate. Furthermore, the inventors unexpectedly discovered that not only does hydrogen not adversely affect the microstructure integrity of the selected smectite clay suspension, but hydrogen also has a positive impact on its viscosity and elasticity when the clay suspension comes in contact with hydrogen, making it a candidate for hydrogen storage. Unlike conventional underground technologies, the inventors designed this innovative technology7so that higher temperatures may help create better flow barriers, and high temperatures may no longer be a concern. An example of a subsurface storage or containment system is described herein with respect to FIG. 22.

[0129] Referring back to FIG. 1, compositions of the present disclosure (for example, a low viscosity and elasticity- suspension) may be injected into the subsurface to create a soft-solid flow barrier. The soft solid may provide for subsurface containment and engineered reservoirs to contain, store, and / or produce energy earners (such as H2 or other energy carriers).PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0130] Aspects described herein aim to make subsurface energy (e.g., fluids such as hydrogen, natural gas, methanol, etc.) storage more efficient, reliable, and geographically agnostic. Unlike existing approaches such as salt caverns, aspects described herein offer the advantage of being geographically agnostic and scalable. Embodiments described herein inject a smectite clay suspension through vertical and / or horizontal wells to create soft solids that act as effective flow barriers. The time-dependent non-Ncwtonian character enables easier pumping and targeted delivery at its initial low viscosity and elasticity, while the suspension ages inside the target zone and matures into a soft solid with much higher viscosity and elasticity that enable it to act as a container and a flow barrier, differentiating it from competing technologies that struggle with injectability and dispersion. This enables the capture and concentration of injected or produced geologic hydrogen and other energy carriers in the subsurface, funneling it towards wellheads for production. The inventors developed a scalable, non-toxic, safe, and economically viable technology that minimizes leakage and directs geologic hydrogen to production wellheads at high concentration and pressure. Conventional approaches for subsurface storage of fluids, primarily in salt caverns, suffer from geographic limitations, low storage capacities, and insufficient seal integrity. These constraints hinder the mass adoption of hydrogen as a clean energy source. Aspects described herein aim to radically transform the subsurface energy (e.g., fluids such as hydrogen, natural gas, methanol, etc.) storage landscape by developing an innovative containment technology that addresses these challenges.

[0131] Rheological properties of smectite clay suspensions may change over time, with the aging process taking more than a year. The inventors thus examined the shear stress (viscosity ) of the suspension under study when the temperature increases using constant shear rate tests. For the 2 wt% smectite clay suspension, it was observed that after only one day of aging at 75°C, the measured shear stress at y = 100 (1 / s) is over four times higher than the shear stress obtained for the same period at room temperature (See FIG. 9A discussed below with Example 2). The influence of aging on measured shear stresses at 75°C, 45°C, and room temperature over the course of 30 days was also measured (See FIG. 9B discussed below with Example 2). The shear stress (viscosity) buildup is greater at45°C than at room temperature, and at 75°C it is the greatest. At both 45°C and room temperature, a similar logarithmic increase is observed, but at 75°C the rate of increase is much larger.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PCThus, as the temperature rises, the suspension does not degrade, but rather becomes more viscous, and its aging accelerates. This means that high temperatures speed up the process of viscosity build up in the porous medium.

[0132] A second rheological property that is useful in determining whether an approach may have flow barrier and containment strategy success is the suspension’s elasticity and gel strength. A common problem in the industry is that fluids with relatively high elasticity cannot be injected and dispersed inside porous media. The inventors conducted strain amplitude sweep tests at different temperatures after various stages of aging. The aim of these tests was to monitor how loss modulus G" and storage modulus G' evolve over time. The storage modulus measures the energy needed to rupture the microstructure of a sample. All the tests were carried out at co = 6.28 rad / s. Results are shown in FIGS. 10A-10D, and further discussed below with respect to Example 2.

[0133] As shown in FIG. 10A, on the first day following suspension preparation, gelling had not yet started since G" is greater than G', which is very favorable for injection and dispersion into a porous medium. The same period at 75°C revealed that G' is slightly greater than G", indicating the gelling had already begun. According to FIG. 10B, after four days at room temperature, G' has now become slightly higher than G", but the suspension still had low elasticity and gel strength (G > G" indicates that the suspension is becoming more solid-like). However, after four days at 75°C, the G' value increased to 100 Pa, indicating that it began to mature into a soft solid. Following 30 days of aging at 75°C. FIG. 10C shows that the G' had risen to 1000 Pa, suggesting a soft solid with a strong gel strength, and at room temperature, G' also reached above 100 Pa, indicating that the suspension matures into a soft solid. Lastly, the aging process was monitored at another temperature, namely 45°C in FIG. 10D, along with the results at 75°C. Comparing them with G' and G" on the first day of preparation at room temperature, it was observed that the G' of sample aged at 75°C had grown 1000 times, and around 300 times at 45°C.

[0134] In H2 storage, the state of a flow barrier’s microstructure (e.g., a suspension that includes a sw ellable clay in water such as a smectite clay suspension) at long timescales may be impactful on the ability of the flow barrier to constrain H2 movement. The oscillation frequency sweep is a useful test for evaluating rheological changes as a function of time. It oscillates the sample continuously at multiple frequencies. Frequency isPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC inversely proportional to time, so high frequencies correspond to short timescales and low frequencies to long timescales. An oscillation frequency sweep was performed at the predetermined linear viscoelastic (LVE) region; with a strain amplitude of g = 1 % for the smectite clay suspension, between frequency values of 100 rad / s and 0.1 rad / s (See FIG. 2). FIG. 2 shows that G' is largely independent of frequency for smectite clay suspension samples at different stages of aging. Phase angle was not included in FIG. 2 in order to avoid clutter. The phase angle was either constant or decreased with decreasing frequency, suggesting a viscoelastic solid or gel structure. Therefore, it may be concluded that the material will maintain its structure and be more stable.

[0135] Based on core flooding results in sandstone porous medium, at early stages of aging (1 week) at 75°C, a core saturated with 2 wt% smectite clay at relatively low overburden pressure contained a gas pressure of about 100 psi (about 690 kPa). Based on the rheological results, the containment pressure keeps increasing over time, and considering that a week is a small period compared to the hydrogen storage process’s characteristic time. So the inventors discovered an application of suspension in underground porous flow, which possesses better injectability and target delivery, its elasticity and viscosity increase over time and at higher temperatures, and hydrogen cannot damage its microstructure integrity.Example IB: Smectite Clay Suspension

[0136] The inventors found that the following three factors may be considered when making a smectite clay suspension or solution — a composition described herein — with desirable rheological properties: (a) pH; (b) ionic strength (amount of salt); and (c) smectite clay concentration.IB. 1. Effect of pH and ionic strength

[0137] The surfaces of smectite clay platelets carry a negative charge due to isomorphic substitution (for example, some magnesium ions are replaced by lithium ions in the octahedral layer). However, the edges of the platelets may become positively charged in an aqueous suspension / solution, depending on the pH of the water (see the structure of smectite clay in FIG. 3).

[0138] A high pH may be more favorable to produce a stable gel network with a controlled rheological profile. At high pH (alkaline conditions), the concentration ofPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC hydrogen ions (H+) is low, and the suspension contains more hydroxide ions (OH-). In this environment, the hydroxyl groups on the edges tend to lose protons and become deprotonated, resulting in negatively charged edges. In contrast, at low pH (acidic conditions), the concentration of hydrogen ions (H+) in the suspension is high. Under such conditions, the hydroxyl groups on the edges of the smectite clay platelets may gain protons and become positively charged.

[0139] At a pH in a range from about 9 to about 11. such as about 10, the edges of the smectite clay platelets are negatively charged due to the deprotonation of edge hydroxyl groups. However, the relatively high salt concentration ( I O3M) helps screen the electrostatic repulsion between the negatively charged surfaces and edges. This screening effect allows smectite clay platelets to come closer together without forming strong aggregates. In such conditions, the electrostatic repulsion is reduced, but not eliminated, resulting in a more controlled, gradual gelation process. This produces a stable gel network with a controlled rheological profile, useful in applications requiring precise tuning of viscosity and flow behavior.

[0140] FIG. 4 A shows a structure of smectite clay, FIG. 4B shows exfoliation of the smectite clay and disordering in aqueous media, and FIG. 4C shows formation of rigid structures involving clay-clay interactions, similar to a house-of-cards structure. This desired house-of-cards structure, which requires some period of time (aging) of the suspension / solution includes clay platelets (e.g., nanosized clay platelets) that are disordered in an edge-to-face fashion at the mesoscopic level which results in a continuous structure throughout the composition, while avoiding nematic gel formation, flocculation, and isotropic liquid formation. As shown, the clay platelets (e.g., nanosized clay platelets) may form a continuous structure throughout the composition.I.B.2. Effect of smectite clay concentration

[0141] The concentration of smectite clay in a suspension may significantly affect its rheological properties, such as viscosity, yield stress, viscoelasticity, and the ability to form gels. The desired rheological properties of a smectite clay suspension may be tailored by adjusting, for example, its concentration, as well as other parameters including pH, ionic strength, temperature, combinations thereof, among others.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0142] The phase diagram of smectite clay suspension (or solution), shown in FIG. 5, informs the behavior of suspension as a function of smectite clay and salt concentrations at constant pH (10 pH). This diagram and boundaries are defined from multiple experiments including rheological measurements, DLS, x-ray scattering, zeta potential, and visual inspection.

[0143] In the phase diagram of smectite clay suspensions, different line sty les (solid, dashed, etc.) and the presence of multiple lines separating regions are used to convey different levels of certainty, types of transitions, or behaviors of the system. The dashed lines often indicate gradual transitions between different phases rather than sharp, well- defined boundaries. These transitions occur when the system does not exhibit a clear-cut change from one phase to another but rather a continuous change in properties such as viscosity, storage modulus (G'), or turbidity.

[0144] Regions in the phase diagram of FIG. 5 include:

[0145] (a) Isotropic Liquid (IL): This region represents the Isotropic Liquid phase, where the smectite clay particles are dispersed in the liquid without significant aggregation or ordering. The suspension remains fluid-like with low viscosity, and the particles are well separated due to electrostatic repulsions.

[0146] (b) Isotropic Gel (IG): This region is where the smectite clay suspension transitions to a gel-like state. In this phase, the system forms a network structure where particles are connected by attractive interactions (such as Van der Waals forces or screened electrostatic forces), resulting in a non-flowing, solid-like gel. The IG region on the phase diagram represents a state where the smectite clay suspension will eventually form a gel. This does not necessarily mean that the suspension will be a gel immediately after preparation. Instead, it will undergo a time-dependent process (known as ‘‘aging’") where it transitions from a liquid-like state to a gel-like state. Initially, right after preparation, the suspension may behave like a low-viscosity liquid. As time progresses, the viscosity increases, and the system evolves into a gel-like state.

[0147] (c) Nematically Ordered Gel (NG): The Nematically Ordered Gel region represents a more structured phase where smectite clay particles are not only aggregated into a gel network but also exhibit some degree of nematic ordering. Nematic order implies that the disc-like smectite clay particles are aligned along a certain direction, although theyPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC might still be randomly distributed in position. In the NG region, the suspension will be a gel immediately after preparation or very shortly thereafter. This is because the combination of high smectite clay concentration and moderate to high salt concentration promotes rapid aggregation and network formation, resulting in a gel state. The high concentration of particles and ions screens electrostatic repulsions, allowing for attractive interactions (like Van der Waals forces) to dominate and cause rapid aggregation. Therefore, the system quickly becomes arrested in a gel state.

[0148] (d) Flocculation (F) Region: Flocculation is a process where dispersed particles come together to form loosely bound aggregates or clumps, known as flocs, without forming a continuous network throughout the suspension. Unlike a gel, where there is a percolated network that spans the entire system, flocculation results in a more localized aggregation of particles.

[0149] The solid lines in the phase diagram generally represent well-defined phase boundaries or sharp transitions between different states of the system. These lines are based on experimental data where the phase change is clear and reproducible. The dashed lines represent less well-defined boundaries or gradual transitions between phases. These boundaries are not as sharp or may indicate a crossover rather than a distinct phase change. I.B.3. Selected Parameters for measurements

[0150] Viscous parameter - dynamic viscosity: Smectite clay has a thixotropic behavior, meaning that its viscosity changes as a function of time. For instance, FIG. 6 shows the viscosity build for 2 wt% smectite clay aqueous suspension over time. Because the viscosity (or shear stress) is also function of temperature, the viscosity (or shear stress) at different aging temperatures may also be measured. The effect of aging on the shear stress of a smectite clay suspension stored at room temperature, 45°C, and 75°C, measured at y = 100 s ' is shown in FIG. 9B and further described below.

[0151] Elastic properties (G' and G") - strain amplitude sweep tests - at different aging times and temperature: G' and G" are measured in the linear viscoelastic region at one day, four days, and 30 days at room temperature (20°C), 45°C, and 75°C aged samples with 2 wt% smectite clay aqueous suspension. FIGS. 10A-10D, further described below, shows the change in elastic properties of 2 wt% smectite clay aqueous suspension.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0152] Frequency sweep test - for long term stability : Oscillation frequency sweep was used to evaluate rheological changes as a function of time. It oscillates the sample continuously at multiple frequencies. Frequency is inversely proportional to time, so high frequencies correspond to short timescales and low frequencies to long timescales. FIGS. 12A and 12B, further described below, show a frequency sweep of a 2 wt% smectite clay aqueous suspension at a strain of y = 1% (FIG. 12A), and an aqueous xanthan dispersions at a strain amplitude of y = 10% (FIG. 12B). Prior to the test, it was confirmed by an amplitude sweep that the strain amplitude value selected was in the LVE region.

[0153] Dynamic and static yield stress - for pumpability / inj ectability: This test may be performed on a fresh sample. FIG. 15 A, further described below, shows a flow curve of a 2 wt% smectite clay aqueous suspension (data points were obtained from constant shear rate tests). FIG. 15B. further described below, shows creep tests for a 2 wt% smectite clay aqueous suspension for a 1-hour duration.Example 2: Containment Strategy for Subsurface Hydrogen Storage Based on Time- Dependent Soft Solids

[0154] The inventors found an innovative containment strategy based on timedependent soft solids, for example, 2 wt% smectite clay suspensions, to reinforce natural subsurface seals and engineer flow barriers, with an eye toward making H2 subsurface storage scalable and geographically agnostic. This suspension may be injected at its initial low viscosity and low elasticity state into a porous medium, allowing for easy pumping and targeted delivery. Once inside the target zone, the suspension matured into a soft solid with much higher viscosity and elasticity, acting as a potential flow barrier. The inventors determined rheological properties of the suspensions and demonstrated that hydrogen does not adversely affect their microstructure, but rather increased the suspensions’ viscosity and elasticity. Moreover, the suspensions enhanced the rock samples' compressive strength, while hydrogen exposure increased their stiffness and ductility. The ability of rock samples saturated with the suspensions to contain higher injected gas pressures was found to be enhanced by aging at higher temperatures.2.1. Introduction

[0155] Energy carriers such as hydrogen play a critical role in enabling a low-carbon economy, and ultimately zero-carbon emissions. Hydrogen represents a paradigm shift inPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC energy storage, especially for renewable energy on an industrial scale, according to the United Nations Industrial Development Organization. Hydrogen plays an important role in limiting global warming, as well as reducing emissions in energy -intensive industries. The Intergovernmental Panel on Climate Change (IPCC) 1.5 C Report highlights its significant role as a fossil-based fuel substitute. As a fuel source, hydrogen offers a potential path to long-term economic growth in the United States and may account for up to 14 percent of the nation's total energy demand by 2050. In the same way, hydrogen plays a prominent role in Europe’s transition: without large-scale hydrogen, the European Union will fail to reach its decarbonization goal.

[0156] The scale of the anticipated hydrogen use will require low-cost, bulk hydrogen storage. Large-scale storage, especially in geological formations, is critical for transitioning to sustainable energy systems that rely on hydrogen as an energy carrier. However, in spite of its high potential, hydrogen geological storage is still in its infancy, with very few large- scale underground hydrogen storage projects being undertaken worldwide. These projects, including Spindietop in the USA with a 906,000 m3of storage capacity, utilize salt domes.

[0157] The storage capacity of salt domes and caverns is, however, limited and their effectiveness as part of a broader energy network depends on their geographical locations. At present, much research at national and international scales is focused on underground gas storage in salt caverns and in porous formations, such as depleted oil and gas reservoirs, aquifers, or unmineable coal seams, and effective containment remains a challenge in subsurface formations, where fluids must be effectively contained by the cap rock over the long-term and leakage risks must be mitigated to enable safe and reliable storage.

[0158] Lateral and vertical containment are desirable for subsurface storage. In geological sequestration projects, lateral and vertical containment failures, as well as induced and triggered seismicity, have been identified as prominent failure modes. Lateral containment failures occur when gas pressure fronts exceed the storage reservoir’s boundaries while vertical failures often result from wellbore or caprock failures. Underground hydrogen storage (UHS) presents several additional challenges compared to other geologic storage scenarios: hydrogen is the smallest molecule and, unlike other fluids such as CO2 and methane, and it may diffuse through rock fabric, making subsurface leakage of hydrogen a significant concern. Moreover, unlike CO2, UHS requiresPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC intermittent injection and withdrawal rates that need to respond dynamically to market demands. Secure containment boundaries conventionally rely on geologic traps, such as combinations of primarily anticline structures paired with impermeable sealing layers. Under repeated injections and withdrawals of gas, subsurface formations are subject to mechanical stresses and strains, potentially compromising their integrity.

[0159] One potential containment solution, commonly used in enhanced oil recovery operations, is polymer solutions. The viscosity of polymer solutions typically decreases with rising temperatures and is influenced by factors such as polymer concentration, molecular weight, salt, and hydrolysis. In recent years, polymers have been developed that withstand high temperatures. Such polymers include thermoviscosifying polymers (TVP), sulfonate polymers, and Schizophyllan biopolymers. In most cases, these polymers are either nearly insensitive to temperature changes or may recover their original viscosity after cooling. In addition, smart thermoviscosifying polymers aqueous solutions have been reported to show an increase in viscosity and elastic moduli with rising temperature. However, existing thermoviscosifying polymers have complex synthesis processes and high production costs. While some polymers exhibit reversible thermogelation behavior and possess thermal gelatinization characteristics, they only exhibit thermoviscosifying behavior at relatively high temperatures. In porous media, viscoelastic fluid flow- may generally be divided into two distinct regimes: shear dominant and extensional dominant. Flow regimes dominated by extensional viscosity may show apparent shear thickening above critical shear rates. The phenomenon attributed to the elastic properties of polymer solutions may result in high injection pressures, thereby impairing injectivity of the polymer solutions. Despite these considerations, partially hydrolyzed polyacrylamide (HP AM) and xanthan gum (XG) have been widely used. These limitations, along with their potential environmental footprint in the subsurface, may prevent their large-scale production and adoption by the industry, which typically favors products with low cost, high polymer content, and generally higher molecular weights.

[0160] The inventors propose a containment strategy that complements existing approaches such as salt caverns and depleted reservoirs by addressing seal integrity constraints and creating flow barners with reduced hydrogen diffusivity and enhanced containment integrity. Advantageously, the technology described herein utilizes the time-PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC dependent non-Newtonian fluid dynamics of smectite clay suspensions, which undergo changes in their physical properties over time, including viscous and elastic properties, thixotropic behavior, and transition to a gel-like state. Aging of these suspensions involves complex, time-dependent changes in their rheological properties and microstructure, influenced by factors such as concentration, pH, ionic strength, and temperature. Through electrostatic interactions and van der Waals forces, smectite clay platelets form a three- dimensional network, transitioning the suspension from a liquid-like state to a solid-like gel. The suspensions are initially low in viscosity and elasticity, providing for ease of injection into the target zone at early stages. As the liquid ages inside the porous media (target zones), it matures into a soft solid with significantly higher viscosity and elasticity, forming an effective flow barrier. Herein, the inventors investigated the rheological properties of 2 wt% smectite clay suspensions including viscosity and elasticity build-up over time and under high temperatures, its long-term stability, cyclic loading and timedependency, and dynamic and static yield stresses. The contributions of the suspension’s rheological properties to a successful containment strategy are described. The suspensions are also compared with those of aqueous polymer dispersions commonly used in the industry, specifically xanthan gum and Carbopol, two classes of polymers. Also explored is how hydrogen may affect the microstructure and rheology of the suspensions, determining the impact on geomechanics of saturated rock and the maximal pressure such formations withstand under gas injection.22 Materials2.2.1. Smectite clav

[0161] An aqueous suspension of smectite clay with the chemical formula Sis.oo (Mg5.45Lio.4o)H4024Nao.75, a molecular weight of 2286.9 g / mol (dry state) and a bulk density of 1000 kg / m3(powder) was prepared. To obtain a gel phase with the desired yield stress, the aqueous suspension included 2 wt% smectite clay with a 1 x 103M NaCl concentration (from a 0.4 mol / L NaCl solution).

[0162] The preparation procedure for the aqueous suspension of smectite clay was performed as follows: Smectite clay was added to water very slowly, a process that typically takes about 5 minutes for preparing 1 liter of suspension. This slow pouring prevents agglomeration and ensures a smooth mixture. Once all the powder was added, thePCT Patent ApplicationAttorney Docket No.: UWYO-0130PC suspension was mixed at a mixing speed of 1600 rpm. After 30 minutes of mixing, the NaCl solution was introduced. The total mixing time is 1 hour.2.2.2. Aqueous polymer dispersions

[0163] Two conventional polymers, Carbopol 980 NF and xanthan gum, commonly used as gelling and thickening agents in the industry, were prepared as aqueous dispersions for comparison and as benchmarking against the suspensions described herein. These materials exhibit time-independent (or very slight time-dependent) material behavior.

[0164] An aqueous solution of 0. 14 wt% Carbopol 980 NF polymer with a bulk density of 176 kg / m3and a molecular weight around 72 g / mol was prepared according to the following procedure: First, the Carbopol powder was sifted through a 20-mesh stainless steel screen to eliminate aggregates that prevent complete hydration. Then, a plastic container was initially filled with a predetermined mass of ultra-pure water obtained from a reverse osmosis system. The container with water was placed on a mechanical stirrer equipped with a 3-blade marine propeller. The stirrer was turned on at 600 rpm and the sifted Carbopol powder was gradually poured into the container, at approximately halfway between the blades and the container’s wall, to avoid adhesion to solid surfaces. After pouring the polymer, the rotation was increased and maintained at 1200 rpm for 15 min, and then the solution w as kept at rest for 30 min. To exclude air bubbles, the 3-blade marine propeller was then replaced by an anchor stirrer, and the rotation was set to 150 rpm. At this point, 0.322 wt% of NaOH aqueous solution (18 wt% NaOH) was added to neutralize the dispersion. Finally, the mixing rate was increased to 300 rpm and maintained for 5 days to homogenize the dispersion. A lid was employed throughout, to minimize water evaporation and avoid contamination.

[0165] Xanthan gum from Xanthomonas campestris is a polysaccharide with many industrial uses. It has a molecular weight of 241. 1 g / mol and a bulk density of 1500 kg / m3. Aqueous dispersions of xanthan gum were prepared with deionized water and mixed at 300 rpm for three days using a magnetic stirrer. Various concentrations w ere prepared, namely 2000, 3000, and 5000 ppm by weight.2.2.3. Core plugs for geomechanics test

[0166] Eight plugs from Hanna sandstone, typical of potential storage formations, with a diameter of 38 mm and a height of 76 mm were prepared for this study. The HannaPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC sandstone cores were obtained from a depth of 15 m of the Hanna Basin located in southeast Wyoming. The average porosity of Hanna sandstone determined using the gravimetric method ranged from 13.8% to 15.4%.2,2.4. Core plugs for pressure containment test

[0167] Four core plugs from the Hanna basin with the same dimensions as above were used for the tests. The gas (air) permeability of these sandstone core plugs was determined via averaging three measurements at different gas flow rates. The permeability was determined to be approximately 40 ± 7 millidarcies (mD) under a confinement pressure of about 1,000 psi (about 6.9 MPa). The porosity of the plugs ranged from 13.8% to 15.4%. 2.3. Non-limiting Results & Discussion2.3.1. Material characterization2.3.1.1. X-ray powder diffraction

[0168] The X-ray powder diffraction (XRD) pattern of the smectite clay powder was measured at 275K using a Rigaku Smart Lab X-ray diffractometer using Cu Ka radiation in the 2-9 scan mode. The sample was lightly ground in a porcelain crucible and the resulting powder was transferred to a 1 mm deep sample holder, where the surface of the powder was smoothed to align exactly with the diffraction plane. The resulting pattern, shown in FIG. 7 agreed with that of the Raman and X-ray Raman Unified Frontier (RRUFF) geologic database for Hectorite (a typical smectite), with no indications of second phases. As shown in FIG. 7, the (300) reflection at 60.75° had a narrow and symmetric line width while the remaining reflections had trailing intensity to higher 26' / smaller lattice dimensions. Because smectite clay is classified as a 2: 1 layered magnesium silicate, this 20 skew is indicative of a distribution of interlayer spacing from that of a fully hydrated structure (OOl)max = 12.5 A to multiple partially hydrated structures having (OOl)min 12.35 A. Individual diffraction peaks were fitted to Lorentzian line shapes to derive peak full widths at half maxima, which were then used to determine crystallite size via the Scherrer equation. This resulted in an average size of 84.8 A ± 5.0 A.2.3.1.2. Scanning electron microscopy

[0169] Because the smectite clay is a dielectric insulator, samples were placed on a metal holder and coated with 100 A of carbon prior to measurement to ensure electrical conductivity and to prevent unwanted sample charging. Scanning electron microscopePCT Patent ApplicationAttorney Docket No.: UWYO-0130PC(SEM) normal and backscatter images of the clay, show n in FIGS. 19A and 19B, indicate an absence of any micaceous features or crystalline facets due to the extreme nanocrystalline size of the clay particles. The lack of any crystalline features, or lamella and conchoidal fractures suggested that the fundamental cry stallite size is below the smallest particles (1 pm) imaged by SEM and that there is no planar alignment between them, in agreement with the X-ray results. Elemental analysis by SEM microprobe was performed for elements having atomic number >6. As shown in FIG. 20, all elements are uniformly distributed and the magnesium to silicon ratio is approximately 2. This was consistent with the expected value for the 2: 1 clay mineral class to which the smectite clay belongs. The lack of any elements other than Si, Mg, and O is noteworthy. Typically, there is Na+or K+dispersed between the Mg / Si / O layers. Their absence here may suggest either the presence of Li+or HsO as the interlayer cation species, neither of which is detected by a standard microprobe.

[0170] Scanning electron microscope (SEM) images, shown in FIG. 20, were collected with an FEI QUANTA 450 with a Schottky Field Emitter Gun. As shown in FIG. 20, an elemental analysis by SEM microprobe was performed for elements having atomic number > 6, e.g., O, Mg, and Si.2,3.2. Rheological properties

[0171] The aqueous suspensions described herein exhibited unique rheological characteristics in contrast to polymer solutions commonly used in the oil and gas industry. These characteristics may allow the suspensions to be an effective time-dependent soft solid as flow barriers in UHS. This Section further details these properties and their application in containment strategies.

[0172] Rheological measurements were conducted using a strain-controlled rheometer, ARES-G2, and a stress-controlled rheometer, AR-G2 from TA instruments. In cases where wall slip is expected, cross-hatched parallel plates with a diameter of 40 mm, an average surface roughness of 500 pm, and a plate gap of 1 mm were used. For high shear rates and samples with lower viscosity, DIN smooth-surface concentric cylinders with a bob diameter of 27.97 mm and a cup diameter of 30 mm were used.2.3.2.1. Aging over time and under high temperature conditionsPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0173] It was found that the rheological properties of the smectite clay suspensions described herein change over time, with the aging process taking more than a year. Here, the shear stress at y = 100 s ' was measured at various points during the first 30 days after preparation. Because the smectite clay suspensions are highly thixotropic (time-dependent), a relatively high constant shear rate was chosen for these tests in order to shorten the steadystate period. FIG. 8A illustrates how shear stress (viscosity) builds up over the course of 30 days. Initially, the rate of increase was higher, but then decreased over time. By leveraging the aging property of the suspension, the smectite clay may be easily injected after preparation. Once delivered into the target zone, the suspension matures into a soft solid with higher viscosity and yield stress inside the porous medium.

[0174] In FIG. 8B, for the same period, a 2,000 ppm aqueous dispersion of xanthan gum showed no increase in shear stress (viscosity). Thus, to achieve a xanthan gum (comparative example) with a high viscosity and yield stress, a high concentration dispersion was prepared. However, the resulting viscosity' may make pumping of this comparative aqueous dispersion more challenging and less likely to reach the target zone.

[0175] Next, the shear stress (viscosity) of the smectite clay suspensions was examined at increasing temperatures using constant shear rate tests as shown in FIG. 9A. FIG. 9B shows the influence of aging on measured shear stresses at 75°C, 45°C, and room temperature over the course of 30 days. The shear stress (viscosity) buildup was greater at 45°C than at room temperature, and at 75°C it was the greatest. After only one day of aging at 75°C, the measured shear stress of the suspensions at y = 100 s ' is over four times higher than the shear stress obtained for the same period at room temperature. At both 45°C and room temperature, a similar logarithmic increase was observed, but at 75°C the rate of increase was much larger. Thus, as the temperature rises, the smectite clay suspension did not degrade, but rather became more viscous, and its aging accelerated. This indicates that, in a subsurface setting, ambient high temperatures may speed up the process of viscosity build up.

[0176] A second rheological property that serves as a useful metric for flow barrier and containment functions of the suspension is its elasticity and gel strength. To investigate this characteristic, strain amplitude sweep tests at different temperatures after various stages of aging were conducted. An aim of these tests was to monitor the evolution of loss modulusPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC(G") and storage modulus (G') over time. The storage modulus measures the energy needed to rupture the microstructure of a sample. All the tests were carried out at co = 6.28 rad / s.

[0177] As shown in FIG. 10A. on the first day following suspension preparation, gelling had not yet started in the room temperature sample because G" is greater than G', which is very favorable for injection and dispersion into a porous medium. However, at 75°C, G' is slightly greater than G", indicating the gelling had already begun. Despite this change, at this stage, the suspension may still be easily injected in porous media.

[0178] According to FIG. 10B, after four days at room temperature, G' was slightly higher than G", but the suspension still had low elasticity and gel strength. However, after four days at 75°C, the G' value increased to 100 Pa, which indicates that the suspension had begun to mature into a soft solid.

[0179] Following 30 days of aging at 75°C, and as shown in FIG. IOC. G' had risen to 1,000 Pa, suggesting a soft solid with a strong gel strength, and at room temperature, G' also reached values above 100 Pa, indicating that the suspension was maturing into a soft solid. Additionally, the aging process at 45°C, as shown in FIG. 10D, was monitored along with results from 75°C. Comparing these results with G' and G" values on the first day of preparation at room temperature showed that G' of the sample aged at 75°C and 45°C increased approximately 1,000 times and 300 times, respectively.

[0180] To benchmark and compare the performance of the suspensions against control data, similar shear stress and strain amplitude measurements using aqueous dispersions of xanthan gum at 75°C were performed. FIG. 11 A shows that shear stress and viscosity of a 2,000 ppm xanthan aqueous dispersion measured at y = 100 s1declined around 20% over only one hour. In FIG. 11B, the shear stress values were determined at y = 100 s ' for a fresh 5,000 ppm xanthan aqueous dispersion at room temperature and after 4 days stored at 75°C. According to the results, the xanthan aqueous dispersion lost roughly 50% of its viscosity after being exposed for four days to 75°C. Furthermore, strain amplitude sweep tests were performed on 3,000 and 5,000 ppm xanthan aqueous dispersions at co = 10 rad / s. The G' values for the 3,000 ppm and 5,000 ppm xanthan aqueous dispersions were found to be approximately 2 Pa and 10 Pa, respectively. Although these dispersion concentrations were relatively high, the resulting gel strengths were not adequate to act as effective flow7barriers. For a gel with a G' equal to 1,000 Pa, one may need to use a much higherPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC concentration of xanthan gum, which would again severely limit injectivity (See FIG. 11 C). In FIG. 11D, the strain amplitude sweep test at CD = 10 rad / s was repeated after storing a 5,000 ppm of xanthan aqueous suspension at 75°C for eight days. Because G" was greater than G', the xanthan aqueous dispersion was no longer a gel and the dispersion had lost its elasticity completely.

[0181] Thus, using the rheological results in hand, the inventors were able to pre-age the suspension and fine-tune its viscosity and elasticity for injection, improving subsurface dispersion (rock coverage) and potentially reducing fluid preparation costs. All rheological tests after the aging period (storage) were carried out at room temperature so that the conditions were the same for all tests, and the reversibility of the rheological properties of the aged suspensions were evaluated. Different concentrations of xanthan gum were also tested to demonstrate that the absence of time-dependent aging features is independent of concentration.23.2.2. Long-term storage stability

[0182] The state of microstructure of the flow barrier, e.g., the suspensions, at long timescales is a useful parameter to determine effective and long term UHS operations. To this end, the oscillation frequency sweep was used to evaluate rheological changes as a function of time. It oscillates the sample continuously at multiple frequencies. Frequency is inversely proportional to time, so high frequencies correspond to short timescales and low frequencies to long timescales. The linear viscoelastic region (LVE) was examined by strain-controlled amplitude sweeps. Because applied strains or stresses in the LVE region are not sufficient to cause structural breakdown, microstructural properties may be measured. After that, an oscillation frequency sweep was performed at the predetermined LVE to determine temporal behavior — a strain amplitude of y = 1 % for the smectite clay suspension and at y = 10% for xanthan dispersions was used, between frequency values of 100 rad / s and 0.1 rad / s.

[0183] FIG. 12A shows that G' is largely independent of frequency for the smectite clay suspension samples at different stages of aging. To avoid clutter, the phase angle is not included in FIG. 12A. The phase angle was either constant or decreases with decreasing frequency, suggesting a viscoelastic solid or gel structure. Therefore, it is concluded that the material may maintain its structure and be more stable.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0184] FIG. 12B shows that G' decreases with decreasing frequency for the xanthan suspension samples. The data showed that the phase angle increases as well. This indicates that the elastic elements of the structure are becoming liquid-like, which implies a lower degree of stability. Also, the rate of increase in phase angle is greatest at a xanthan gum concentration of 2,000 ppm, and at 3,000 ppm of xanthan gum is greater than at 5,000 ppm of xanthan gum, which indicates that as the concentrations of xanthan gum dispersion are lower, the stability of the long-term solution will be less.

[0185] It was not feasible to mitigate water evaporation at 75°C for longer periods, but the tests were continued at room temperature and 45°C. The frequency sweep tests (FIG. 13 A) after 5 months of aging of the smectite clay suspensions shows that G' and G" were parallel and that their distance continued to grow, demonstrating that smectite clay suspension stability tended to improve continuously over time. This result is supported by the measurements in FIG. 13B showing that G' of a smectite clay suspension still rises even aged for 5 months at 45°C.

[0186] Based on these results, it may be concluded that — contrary to common polymer solutions applications used in the oil and gas industry, where longer periods and higher temperatures lead to severe detrimental complications, — longer periods and higher temperatures strengthen the smectite clay suspensions’ characteristics that make it suitable for underground storage operations.2.3.2.3. Cyclic loading & time-dependency

[0187] It is also useful to determine whether the soft solids under study resist fatigue caused by underground hydrogen storage cycles. To this end, the smectite clay suspension’s performance under cyclic loading was assessed by examining whether the microstructure of the suspension begins to deteriorate after several cycles of destruction and reconstruction. To ensure a fully destructured state, the smectite clay suspension was sheared at a relatively high shear rate of y = 100 s1for 20 min. The sample was then allowed to rest at oa= 3 Pa, below the dynamic yield stress for 3,000 s. This rest period was determined by an oscillatory time sweep test, shown in FIGS. 21 A and 2 IB. This cycle was repeated four times.

[0188] As shown in FIG. 14, after each cycle, the shear stress of the starting point had only a small reduction. Therefore, it was determined that minimal to no microstructurePCT Patent ApplicationAttorney Docket No.: UWYO-0130PC deterioration was present in the smectite clay suspension sample. To provide an estimate of the microstructure construction time, small-amplitude oscillatory tests over time were conducted. Initially, the smectite clay suspension sample was pre-sheared at a constant rate until steady state was reached. A strain or stress amplitude was then immediately applied at a fixed oscillatory frequency. The output data included the evolution of storage and loss moduli. To allow an unconstrained microscopic construction over time, the applied strain or stress amplitude was below the yield strain or dynamic yield stress, respectively.

[0189] The smectite clay suspension was subjected to a constant shear rate of y = 100 s ' for 2,400 seconds, followed by a 7,200 seconds rest period at oa= 3 Pa, below the dynamic yield stress. As shown in FIG. 21 A, G' climbed sharply below 1,500 s, while G" dropped rapidly, suggesting a gelling process. As time passed, the rate of change G" diminished and eventually reached a constant value after 3,000 seconds.

[0190] The thixotropic behavior of the smectite clay suspensions is noteworthy that, in addition to resisting microstructure degradation resulting from cyclic loading, the smectite clay suspensions’ time-dependent characteristics may bring even more advantages to the process of injection into porous media compared to conventional polymer solutions commonly used in the industry.

[0191] The 5,000 ppm xanthan aqueous dispersion was subjected to a constant shear rate of y = 100 s ' for 300 s followed by a rest period of 300 s at ya= 0. 1%, below the yield strain. However, as shown in FIG. 21 B, G' and G" for an aqueous dispersion of xanthan were parallel and showed negligible changes from the first seconds of testing, demonstrating its time-independency, which indicated microstructure construction occurred almost instantly, in contrast to the smectite clay suspensions which take much longer to rebuild. Here, the thixotropic / time-dependent behavior allows for ease of handling and injection while the suspension is fresh. Once it is delivered to the target zone in the subsurface, given the temperature conditions, the suspension is expected to age and become solid-like, resisting flow and creating a barrier against leakage of stored fluids.

[0192] The smectite clay’s thixotropic microstructure construction offers advantages in injection operations, such as time-to-address issues that may arise during injection, due to the lengthy microstructure rebuild. The smectite clay’s thixotropic microstructure alsoPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC provides better control of apparent shear thickening, or yield stress build-up, utilizing the time-dependent nature of the smectite clay suspensions.2.3.2.4. Dynamic and static yield stresses

[0193] The static yield stress (indicating a transition from solid to liquid) and the dynamic yield stress (indicating a fluid-to-solid transition) are useful for a containment strategy', representing fluid pumpability7and its flow barrier performance. FIG. 15 A shows shear stress values obtained from constant shear rate tests for the suspension plotted against related shear rates. Because the smectite clay suspension has a high level of timedependency, reaching a steady7state requires long periods of time, especially at low shear rates. Due to shear banding, flow curves for the smectite clay suspensions were nonmonotonic. There is a critical shear rate ycd= 1 s ', below which the applied shear rates are not uniformly felt by the entire sample, “cd” refers to the dynamic yield stress at the given critical share rate. Instead, two (or more) bands form. Thus, the shear-banded region did not belong to the flow curve. Therefore, the flow curve of the suspension was plotted until the critical shear rate. Thus, the dynamic yield stress was equal to the steady-state stress corresponding to ycd= 1 s ', namely ocd = 6.8 Pa (FIG. 15 A).

[0194] Static yield stress was determined by creep tests. After the pre-test procedure, a fresh sample was subjected to a constant shear stress for one hour. The output was the time evolution of the shear rate. The test was repeated with different shear stress values: when shear rates approached zero monotonically, the imposed stress value was below the static yield stress; and when the shear rate tended to non-zero steady-state values, the imposed stress value was above the static yield stress. FIG. 15B shows that the static yield stress of the suspension under study was between 16 Pa and 17 Pa. Tests with the suspensions were conducted on the 18th day of aging after preparation. Because the smectite clay suspension is highly thixotropic, all tests were started at the same structuring level, e.g., the same initial condition. Therefore, a pre-test was utilized before every creep test with the suspension. The suspension’s microstructure breaks down while being loaded into the rheometer, so a rest period was allowed before starting the test.

[0195] It is also useful to estimate how long it takes the suspension to rebuild its microstructure. Small-amplitude oscillatory tests over time were used to estimate this microstructure construction time. A pre-test procedure was adopted in this work to facilitatePCT Patent ApplicationAttorney Docket No.: UWYO-0130PC the comparison of the rheological properties of the suspension with those of aqueous polymer dispersions. Thus, the following pre-test procedure was followed: first, the sample was subjected to a constant shear rate of y = 100 s ' for 1,200 seconds (s); then it was allowed to rest a period of 1,500 s at y = 0.1%, below the yield strain.

[0196] The static and dynamic yield stress values of 0.14 wt% Carbopol aqueous dispersion were compared with those of the smectite clay suspension. The Carbopol aqueous solution flow curve is shown in FIG. 16A. In order to verify repeatability, identical tests were performed in ascending and descending manners, resulting in essentially the same curves. A Herschel-Bulkley fitting resulted in a dynamic yield stress of 13.7 Pa for the Carbopol solution. The static yield stress of 0.14 wt% Carbopol aqueous solution was determined by creep tests using the same procedure as for the suspension. According to FIG. 16B, for the Carbopol solution, the static yield stress oyslies between 14.2 Pa and 14.6 Pa. Therefore, it was observed that dynamic and static yield stress values are very similar for this class of time-independent yield stress fluids.

[0197] Therefore, the suspensions have a static yield stress that is more than two times higher than its dynamic yield stress, compared to other yield stress fluids such as Carbopol aqueous dispersions. This quality' gives the smectite clay suspensions favorable pumpability' (dynamic yield stress) while providing containment capability' (static yield stress) once inside porous media.2.3.2.5. Effect of hydrogen

[0198] Physisorption — physical adsorption that follows the Langmuir adsorption equation — dominates adsorption in clay minerals. In general, as pressure increases, adsorption capacity' increases; however, as temperature increases, adsorption capacity decreases. Under high pressure, hydrogen gas intercalates within smectitic and synthetic clays’ interlayers when the crystallite spacing is at least 10.8 A. An interlayer of the suspension is a space between adjacent monolayers. Hydrated interlayers allow guest molecules to be accommodated under appropriate conditions, enabling water molecules to spread the interlayers and provide molecular pillars between them. Under pressure, hydrogen molecules diffuse into the interlayer spaces, where they may reside. The smectite clay suspensions form interlayers primarily through electrostatic interactions and hydrogen-bonding between monolayers. The negatively charged surfaces of the particlesPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC may also interact with positively charged ions in the water, resulting in interparticle attractions. As smectite clay suspension particles hydrate into individual layers, subsequent ordering of the layers gives rise to the interlayers.

[0199] Due to the demonstrated interlayer changes with hydrogen exposure, the inventors designed tests to determine what the intercalation of hydrogen in interlayers of 2 wt% smectite clay suspension does to its rheology. Four samples of smectite clay suspensions were utilized, two of which were aged at 75°C and 10 bar, and exposed to nitrogen for one week. Two other samples of smectite clay suspensions were aged at the same pressure, temperature, and time, but exposed to hydrogen gas. The suspensions exposed to hydrogen exhibited approximately 1.8 times greater elasticity through strain amplitude sweep tests. In constant shear rate tests, the steady-state shear stress increased by more than 50% for hydrogen-exposed suspensions as shown in FIG. 17. While there are no concrete studies regarding this phenomenon, the inventors believe the increase in elasticity and viscosity may be due to the favorable interlayer arrangements caused by intercalating hydrogen molecules. This is a very promising phenomenon in porous media flow, because as the injected aged smectite clay suspension comes in contact with hydrogen, it becomes even more elastic and viscous, enhancing its performance as a flow barrier. Moreover, these results suggest that smectite clay suspensions may significantly reduce hydrogen diffusion rates.2,3.3. Geomechanics2.3.3.1. Core plugs subjected to various treatments

[0200] Four treatment conditions were applied to selected plugs from the Hanna basin: (1) Baseline: oven-dried plugs were used with no further treatment; (2) Saturated with water: plugs were vacuum-saturated with water for 24 h; (3) The plugs were placed inside a beaker filled with the suspension. The beaker and plugs were then placed inside a vacuum incubator for 24 h to saturate the plugs. Then, the saturated plugs were placed in an autoclave vessel (MTIHPV10LH) at 75°C for one week; and (4) Treated with hydrogen (H2): the initial saturation was similarly applied to the rock plugs. These plugs were later treated in the autoclave vessel filled with H2 gas (99.999% purity) for one week at 75°C and a pressure of 10 bar. Two rock plugs under each treatment condition were prepared for triaxial compression (TC) tests under confining pressures of 5 and 10 MPa. Table 1PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC summarizes the plug identification, treatment condition, and confining pressure for the eight plugs SI to S8.Table 1

[0201] The TC tests were conducted at 75°C using a high-pressure and high- temperature polyaxial equipment (NER AutoLab 1500) at the University of Wyoming. Each plug was covered with a Viton jacket and instrumented with one radial and two axial LVDTs (Linear Variable Differential Transformer). An initial confining pressure of 2 MPa was applied to the plug, the temperature was increased to 75°C, and the confining pressure was increased to the target value (5 or 10 MPa) at a rate of 3 MPa / min. Next, an initial deviatoric stress of 2 MPa was applied to the plug, and the deviatoric stress was increased at a rate of 0.003 mm / s until failure occurred.2.3.3.2. Geomechanics tests results

[0202] FIG. 18A shows plots of deviatoric stress (Aoa) versus the axial (on the right) and radial (on the left) strain (s) from the TC tests on plugs SI , S3, S5, and S7 under the confining pressure of 5 MPa. Oven-dried plug S 1 exhibited a higher peak strength of about 25 MPa than 18 MPa of plug S3 saturated with water, which serves as a lubricant for shearing and could dissolve binding minerals. Interestingly, plug S5 and plug S7 treated with the suspension exhibited a higher peak compressive strength of about 42 MPa, which is 68% higher than that of plug S 1 and 133% higher than that of plug S3. As the suspensionPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC aged at higher temperatures, its viscosity and yield strength (y ield stress) increased, enhancing the compressive strength of saturated rock.

[0203] The comparable axial stress-strain responses of plug S5 and plug S7 suggested an insignificant effect of H2 treatment on the behavior of the rock. Plug S5 and plug S7 failed at a similar axial strain of about 6.8 m(s), compared to 9.8 m(e) of plug SI. Young’s moduli of 8 GPa and 7.6 GPa for plug S5 and plug S7, respectively, were higher than the Young's moduli of 6 GPa for plug S3 and 4.3 GPa for plug SI. The higher Young’s modulus may be attributed to saturation with the suspension and the increase in G' of the suspension at 75°C (See FIG. 10). Plug S5 experienced a smaller radial strain at failure than S7. Hence, the smaller Poisson’s ratio 0.05 of plug S5 than 0.12 of plug S7 indicated that plug S5 is more compressible than plug S7. However, plug S3 saturated with water had a relatively high Poisson's ratio of 0.6, which is comparable to that of water, suggesting the incompressible behavior of plug S3 was dominated by water saturation. While not wishing to be bound by any theory, it is believed that compressibility' is mostly attributed to their intrinsic microstructure and saturated pore fluid rather than hydrogen reaction. Regarding the post-failure behavior, plug S3, plug S5, and plug S7 failed with a sudden drop in the Aoa, indicating a brittle failure behavior, while plug SI failed in a more ductile manner due to the continuous closure of empty' pore spaces under Aoa. The stress-strain responses showed a significant effect from the smectite clay suspension’s treatment and minimal effect of H2 reaction on the compressive strength, toughness, and Young's modulus of the Hanna sandstone under the confining pressure of 5 MPa.

[0204] FIG. 18B shows the plots of (Aod) versus the axial (on the right) and radial (on the left) strain (s) from the TC tests on plug S2, plug S4, plug S6, and plug S8 under the confining pressure of 10 MPa. Plug S6 treated with the smectite clay suspension and plug S8 treated with smectite clay +H2 exhibited comparable compressive strengths of 50 MPa and 48 MPa, respectively, which are approximately 58% higher than 31 MPa of oven-dried plug S2 and 133% higher than 21 MPa of the water-saturated plug S4. Similar to the observations under the confining pressure of 5 MPa, this comparison suggests that the higher viscosity and shear strength (yield stress) of the smectite clay suspension at 75°C increased the compressive strength of the rock plugs. Plug S6 failed at an axial strain of 12.3 m(s), which was higher than 6.3 m(s) of plug S8, 5.9 m(c) of plug S2, and 2.9 m(s) ofPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC plug S4. This comparison suggests that (1) the saturation may have increased the axial strain at failure, (2) H2 treatment reduces this effect in plug S8, and (3) water saturation significantly reduces the axial strain at failure. The radial responses of plug S6 and plug S8 prior to failure were comparable, and so are their Poisson’s ratios of 0.08 and 0.1, respectively. However, plug S6 failed at a slightly higher radial strain than plug S8, which may be attributed to the increase in G' of the smectite clay suspension in plug S8 due to H2 treatment (See FIG. 17). Plug S2 experienced a higher radial strain than S6 due to the continuous deformation of empty pore spaces in plug S2. The Young’s modulus of 10 GPa for S8 is higher than 7.4 GPa for S2, 8 GPa for S4, and 5.6 GPa for plug S6 due to the increase in G' of the suspension in plug S8 resulting from H2 treatment (See FIG. 17). These pre-failure responses suggest that H2 treatment of saturated core plugs may have increased the stiffness of Hanna sandstone at 10 MPa. Comparing the post-failure behavior, plug S6 experienced a sudden decrease in Ao<i and a more brittle failure. In contrast, plug S8 experienced a gradual decrease in Aoa with increasing axial strain, indicating a more ductile failure. Plug S2 and plug S4 experienced a more brittle failure behavior than both plug S6 and plug S8. Hence, the ductile failure becomes more pronounced at a combination of higher confining pressure, the smectite clay suspension’s saturation, and H2 treatment. Saturation with the smectite clay suspension increased the peak compressive strength of the Hanna sandstone under both confining pressures. This may be due to the smectite clay suspension filling the rock plugs' pore space. The existence of elements like Si and the increase in the shear strength of the smectite clay suspension with time and at 75°C increased the resistance of rock plugs against shearing in the triaxial compression tests. The reaction between H2 and rock is the result of a complex interplay between various factors such as mineralogy, porosity, temperature, pressure, and treatment duration. While other studies reported more significant changes in rock properties after H2 treatment, no major alterations, except the increase in the stiffness, toughness, and ductility of the rock, were determined on Hanna sandstone in this study.2,3.4. Pressure containment experiments

[0205] How aging enhances the containment performance of the suspensions in porous media was also evaluated. After vacuum-saturating four core plugs, they were aged for three distinct periods at 75°C, namely 1 day, 8 days, and 21 days. Air was used for thePCT Patent ApplicationAttorney Docket No.: UWYO-0130PC flooding tests. As soon as the first air bubble appeared in the outlet tube, containment was assumed to have been breached (the outlet tube was inserted in a water container to clearly discern bubbles). The flooding tests were designed to be similar to creep tests. A constant pressure of about 10 psi (about 69 kPa) was applied by an ISCO 500D syringe pump. This pressure was established and maintained for one minute. If no bubble was detected, the pressure was raised by about 10 psi (about 69 kPa), and the procedure was repeated until the first air bubble was detected. Based on the rapid breakthrough on day one. it was concluded that the actual containment pressure was lower than about 10 psi (about 69 kPa). A confining pressure of about 1,000 psi (about 6.9 MPa) was also imposed. The same flooding procedure was followed for the saturated core plug aged for eight days. The first bubbles appeared at about 80 psi (about 550 kPa). In this state of aging, an additional test was performed under a confining pressure of about 2.000 psi (about 14 MPa). A goal was to evaluate whether confining pressure significantly affects the obtained containment pressure. However, the containment was once again breached at about 80 psi (about 550 kPa). Thus, the next flooding test for the 21-day-aged core plug was also conducted at a confining pressure of 1,000 psi (about 6.9 MPa). The saturated core plug aged for 21 days exhibited a maximum containment pressure of about 220 psi (about 1.5 MPa). Due to the presence of signs of evaporation at this high temperature, and not being able to control it, these flooding tests were not continued for longer periods. Nevertheless, consistent with the smectite clay suspensions’ aging behavior, the containment pressure is expected to further increase with time.2.4. Non-limiting Conclusions

[0206] To address storage and containment challenges in hydrogen subsurface systems, the inventors propose a strategy based on smectite clay suspensions. Various properties of these suspensions may offer effective subsurface containment and storage in service of the ongoing transition to more sustainable energy systems. The time-dependent nonNewtonian fluid dynamics of the suspensions was explored, which start with low viscosity and elasticity for ease of injection, and transform into high-viscosity, elastic soft solids inside the target zone to serve as a potential flow barrier.

[0207] Example 2 presents an extensive study of rheology, geomechanics, and porous media flow of 2 wt% smectite clay suspensions exposed to hydrogen to evaluate itsPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC performance engineering underground reservoirs for subsurface hydrogen storage. Nonlimiting findings from this study include the following:

[0208] (a) Unlike most polymeric aqueous dispersions conventionally used in the industry, the long-term stability of smectite clay suspensions was not adversely affected by high temperatures. Instead, the higher temperatures and longer periods enabled the soft solid under study to form more effective flow barriers with greater elasticity7and viscosity values.

[0209] (b) The reversible time-dependent characteristics of the smectite clay suspensions resisted microstructure degradation resulting from cyclic loading, which is useful for subsurface hydrogen storage. Also, its thixotropic microstructure offers many advantages in operations, such as handling sudden pump shutdowns.

[0210] (c) The findings suggested that hydrogen does not adversely affect the microstructure of the smectite clay suspensions. Instead, it was found that hydrogen increased the suspensions’ viscosity and elasticity7due to its intercalation into the smectite clay suspensions’ interlayers.

[0211] (d) Hydrogen molecules may be entrapped in interlayers of the smectite clay suspensions, suggesting a possible significant reduction in hydrogen diffusion.

[0212] (e) Under both confining pressures of 5 MPa and 10 MPa, saturation with the smectite clay suspensions increased the compressive strength of sandstone core plugs.

[0213] (I) Under a confining pressure of 5 MPa, H2 treatment has a negligible effect on the mechanical properties of saturated rock samples. However, under the higher confining pressure of 10 MPa, H2 exposure increases the stiffness, toughness, and ductility of the saturated plugs.

[0214] (g) Ductile failure became more pronounced at a combination of the smectite clay suspension’s saturation and H2 exposure.

[0215] (h) Rock samples saturated with the smectite clay suspension that were aged longer and at higher temperatures may contain higher pressures in porous media. As synthetic clay may be synthesized inexpensively and is easily produced on a large scale, it offers a promising approach for achieving subsurface containment and engineered reservoirs, such as with higher concentrations of the smectite clay suspension, such as 2.5 wt% or 3 wt%, e.g., higher viscosity and elasticity aiming at higher containment pressures.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0216] With strategies described herein, natural subsurface seals may be strengthened and engineered barriers may be created. The proposed strategies can complement existing technologies, such as salt caverns and depleted reservoirs, such as when they are constrained by size and seal integrity, making previously unsuitable geologic structures viable for hydrogen storage.Example 3: Illustrative, but Non-limiting, Subsurface Storage or Containment System

[0217] FIG. 22 shows an example subsurface storage or containment system according to at least one embodiment. Table 2 shows selected components of the system.Table 2

[0218] Below a wellhead 2201 may be disposed an engineered subsurface reservoir 2209 for storing any suitable fluid such as H2, CO2, natural gas, methanol, or combinations thereof, among others. Around the engineered subsurface reservoir 2209 is a target zone 2211. The target zone may include a pre-defined area surrounding at least a portion of the engineered subsurface reservoir 2209. The target zone may include a porous medium, for example, rock. In the target zone may be placed a composition described herein (e.g., a synthetic smectite clay suspension). For example, a composition that includes a swellable clay and an aqueous material into a subsurface formation (such as a clay suspension having low viscosity and elasticity) may be introduced through a pipe 2203 (or other suitable conduit) into the reservoir to form a soft solid flow barrier 2207. Residual composition may exit the reservoir through pipe 2205. Pipe 2203 and pipe 2205 may be a vertical and / or horizontal well.

[0219] The composition, e.g., a suspension that includes swellable clay in water, may be designed to reinforce natural subsurface seals and create engineered flow barriers (e.g., soft solid flow barrier 2207). Once in the target zone 2211, the composition may serve toPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC significantly reduce diffusion of fluid (for example, H2, CO2, natural gas, methanol, or combinations thereof, among others) out of the subsurface. The inventors unexpectedly found that not only does hydrogen not adversely affect the microstructure integrity of the clay suspension (composition), but hydrogen also has a positive impact on its viscosity and elasticity when the clay suspension comes into contact with hydrogen. In contrast to conventional approaches for underground storage (such as polymer solutions), the compositions described herein may be designed so that higher temperatures may help create better flow barriers, and high temperatures may no longer be a concern. In contrast to conventional approaches for hydrogen storage, such as salt domes and salt caverns which are porous, leaky, and have low7storage capacity, the system allows for high storage capacity7and significantly less leakage of hydrogen. Moreover, the system is not limited to specific geologies and geographic locations.Example 4: Engineered Barriers for Subsurface Hydrogen Storage

[0220] The study presented in Example 4 investigates the potential of Laponite suspensions as flow7barriers for geological hydrogen storage by assessing their rheological properties and ability to contain hydrogen in a microfluidic device. The Laponite suspensions are example compositions comprising a swellable clay and an aqueous material according to aspects described herein.

[0221] Based on a phase diagram, 2 wt%, 2.5 wt%, and 3 wt% Laponite suspensions initially exhibited low viscosity but developed high elasticity and viscosity over time, properties useful for effective injection and sealing. Comprehensive rheological characterization, including steady state shear viscosity evolution, and oscillatory tests, revealed that under the conditions tested the 3 wt% suspension became a gel too rapidly, making it unsuitable for injection. As described in Example 4, microfluidic devices mimicking Berea sandstone pore structure were fabricated and experiments were conducted by injecting 2 wt% and 2.5 wt% suspensions, aging them for different time periods at 75°C, and performing hydrogen injection tests using a custom-built setup. Breakthrough pressure measurements showed that the 2 wt% suspension tolerated about 105 psi (about 724 kPa) aging for 18 days at 75°C. while the 2.5 wt% suspension withstood about 346 psi (about 2.39 MPa) after aging for 18 days at 75°C. These findings highlight the potential ofPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC swellable clay suspensions (e.g., a 2.5 wt% Laponite suspension) as effective in-situ geobarriers for geological hydrogen storage.4.1. Materials and methods4.1.1. Chemicals

[0222] Laponite® RD powder was obtained from Kremer Pigmente GmbH & Co. KG. This synthetic layered silicate has a bulk density of approximately 1000 kg / m3. Laponite is a synthetic smectite clay. Laboratory -grade sodium chloride (NaCl) and sodium hydroxide (NaOH) were purchased from Sigma- Aldrich and used to adjust the salinity and pH of the suspension. Borosilicate wafers coated with chrome and photoresist from TELIC Company were used as substrates for microfluidic fabrication. Various chemical agents were used during the fabrication process, including a photoresist developer (Microposit 351), a chrome etchant (Transene), a glass etchant (BD etchants / Transene). a silylation agent (HDMS), and a photoresist resin (SU-08 / Microchem). Additionally, N-methyl-2- pyrrolidone (NMP, Ultra-Pure Solutions) was used for cleaning, along with Piranha Solution, composed of sulfuric acid (H2SO4, Sigma- Aldrich) and hydrogen peroxide (H2O2, Fisher Chemical). An HCI-H2O2 solution (both from Fisher Chemical) was also used in the process.4.1.2. Suspension preparation

[0223] Due to the high surface area and negatively charged surfaces of Laponite platelets, the Laponite powder is highly hygroscopic and tends to absorb moisture. The water content varies depending on storage conditions. To ensure reproducible suspension preparation and experimental consistency, the initial water content was characterized and the appropriate drying procedures were applied to remove loosely bound water before preparing the suspension.

[0224] A NETZSCH TG 209F3 Thermogravimetric Analyzer (TGA) was used to determine the thermal stability and water content of the Laponite samples before and after drying. It was found that most free water is removed at around 120°C. To avoid potential structural changes due to excessive heating, drying at 120°C for 4 hours was deemed sufficient. The drying protocol was followed for all experiments. The TGA curves for dried and as-received samples are presented in FIG. 23. In this study, the pH of the suspension was maintained at 10 and the salinity was kept around I 03M. The remaining suspensionPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC preparation steps followed the procedure outlined in B. Abedi et al. “Containment strategy for subsurface H2 storage based on time-dependent soft solids.'’ (2024) International Journal of Hydrogen Energy, 82, 1001-1014.4, 1.3. Rheological tests

[0225] A strain-controlled rheometer, ARES-G2, from TA instruments was used for all rheological tests. Due to the likelihood of wall slip, a cross-hatched parallel plate geometry with a 40 mm diameter, 500 pm surface roughness, and 1mm gap was used. Laponite suspensions were prepared at concentrations of 2 wt%, 2.5 wt%, and 3 w4% (w / w), and each concentration was divided into three separate batches. These batches were aged under three different conditions: room temperature (20°C), 45°C, and 75°C. Several rheological tests were conducted at different aging intervals (1st, 4th, 7th, 11th, 18th, and 30th days of preparation). FIG. 24 illustrates the sequence of rheological tests.

[0226] Additionally, it was observed that evaporation significantly affected the rheology of Laponite suspensions, especially at high temperatures. As a result, samples aged at high temperatures without proper sealing became more brittle and exhibited inconsistent rheological behavior. Therefore, aging suspensions were stored in well-sealed containers and the gel was sampled from the middle of the batch for consistent rheology measurements.4.1.3.1. Pre-shear / recovery step, viscosity evolution

[0227] The thixotropic nature of Laponite suspension poses challenges in performing rheological tests. One challenge is the partial destruction of the microstructure when loading the sample into the rheometer’s geometry' before testing. To obtain consistent results, all tests were started from the same initial condition, ensuring that different structural disruptions during loading do not bias the results. This was achieved through a pre-shear / recovery step (or microstructure destruction / rebuild steps), which involved shearing the entire sample at a constant share rate for a defined duration to fully break dow n the microstructure, immediately followed by a specific recovery7period to allows microstructure reformation.

[0228] When subjected to constant shear (relatively high shear rate), the viscosity (or shear stress) of aged Laponite suspensions is expected to exponentially decrease until reaching a steady-state value. These steady-state viscosity values, obtained from constantPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC shear rate tests, can be used to assess viscosity evolution under different aging conditions. Viscosity is a rheological parameter that describes the fluid's resistance to flow of fluids in porous media. For Laponite suspensions to be effective as in-situ geobarriers in subsurface applications, the suspensions should initially exhibit low viscosity for easy injection. Over time, viscosity of the suspension should increase, enabling the aged fluid to resist flow and provide containment.

[0229] Herein is reported the evolution of steady-state viscosity over 30 days of aging at a constant shear rate. Accounting for the suspension’s thixotropy, viscosity measurements were obtained by shearing the suspension at a constant shear rate of y = 100 s ' for 1200 seconds. Additionally, oscillation time sweep tests were conducted to obser e the evolution of microstructure build-up for 1500 seconds referred as recovery period, immediately following complete disruption by steady-state shearing. The test was performed at an oscillation frequency of 6.28 rad / s and an oscillation strain of 0.1%, which is small enough to avoid disturbing the microstructure build-up. Here, the steady-state shear viscosity of 2 wt%, 2.5 wt%. and 3 wt% Laponite suspensions aged at three different temperatures — room temperature (20°C), 45°C, and 75°C — over various aging periods were measured and reported.4.1.3.2. Linear viscoelastic region - Strain amplitude sweep test.

[0230] Strain amplitude sweep tests are typically performed before oscillatory frequency sweep tests to determine the LVE. ensuring that frequency sweeps are conducted without disrupting the microstructure. These tests provide certain rheological properties such as gel strength and offer insights into the fluid-like or solid-like behavior of the samples.

[0231] Strain amplitude sweep tests were performed after the pre-shear / recovery step for all samples at different aging periods. The evolution of the storage modulus (G) and loss modulus (G") was measured across a strain amplitude range (y) from 0.1% to 1000%, at a constant angular frequency of co = 6.28 rad / s. The storage modulus (G') represents a measure of the stored energy in a material during deformation, while the loss modulus (G") represents the energy dissipated as heat. The LVE region is defined as the range where G' remains independent of strain, indicating that frequency tests can be performed without disrupting the microstructure. Furthermore, the values of G' and G" provide insight into thePCT Patent ApplicationAttorney Docket No.: UWYO-0130PC viscoelastic behavior of the sample. If G' > G", the sample behaves as a viscoelastic solid, whereas if G" > G', the material behaves as a viscoelastic liquid. A larger separation between G' and G" indicates stronger elastic or viscous dominance.4. 1.3.3. Elasticity Evolution - Oscillatory frequency sweep tests

[0232] Since Laponite suspensions undergo structural changes over time, understanding the kinetics of this process is valuable, particularly for containment applications where a stable microstructure should be maintained. After a pre-shear step, oscillatory frequency sweep tests were conducted within the established linear viscoelastic (LVE) region, as determined from strain amplitude sweep tests. In these tests, higher frequencies correspond to shorter timescales, while lower frequencies represent longer timescales. During the tests, the angular frequency (CD) was varied over a wide range from 0.01 to 100 rad / s. The evolution of G' was assessed at different aging stages and temperatures. The results and their interpretations are presented in Results Section 4.2.4.1.3.4. Static yield stress - creep test

[0233] Aged Laponite suspensions exhibit static yield stress, meaning a minimum threshold stress is required to initiate flow by breaking down the three-dimensional microstructure. A creep recovery test is commonly used to measure static yield stress by applying controlled stress and measuring the resulting shear rate. For subsurface applications, yield stress indicates the pressure required to initiate flow and assesses the strength of the flow barrier after aging. In this study, the static yield stress of 2 wt%, 2.5 wt%. and 3 wt% Laponite suspensions on their 16th day of aging were measured and compared. After a pre-shear / recovery step, through creep tests stepwise stresses were applied, each maintained for one hour. The shear rate evolution was recorded. If the shear rate decreases monotonically toward zero, the applied stress is below the static yield stress; otherwise, the applied stress matches or exceeds the static yield stress.

[0234] The static yield stress for 2 wt%, 2.5 wt%, and 3 wt% suspensions were found to be equal to 25 Pa, 27 Pa, and 51 Pa respectively and the creep test curves are presented in FIG. 25.4.1.4. Microfluidic chip fabrication & Laponite injection

[0235] Selected operations of a method 2600 for microfluidic chip fabrication are shown in FIG. 26. The microchip design was developed by adding connections to porePCT Patent ApplicationAttorney Docket No.: UWYO-0130PC images gathered from CT-scanned Berea sandstone. The process involved superimposing a skeleton onto the initial pore mosaic to create throats. Then, editing the throats width based on three-dimensional (3D) network data such that the two-dimensional (2D) throat size distribution resembles the one in the rock sub-volume. A last step involved smoothing the pattern to correct imperfections in the grains to ensure morphology of the rock subvolume is accurately represented in the quasi-2D chip. Microchips were then fabricated using an in-house photolithography method. This method was chosen for its ability to reproduce microchips with complex porous geometries. In summary, the method 2600 for microfluidic chip fabrication included:

[0236] 2605: CT scan to collect pore space CT images.

[0237] 2610: Collect pore network data

[0238] 2615: Create a design based on pore CT images and throat size data (initial pore mosaic —> final mosaic).

[0239] 2620: Create a photomask with distribution systems from the final mosaic.

[0240] 2625: Fabricate the microchip.

[0241] Following fabricating, freshly prepared Laponite suspensions were injected into the microfluidic device using a syringe pump (PHD Ultra®) at a flow rate of 0. 1 mL / min until complete pore volume saturation was visually confirmed. During initial tests, an issue affecting the quality7of aging within the microfluidic pores was identified. Evaporation from the device’s inlet and outlets during high temperature aging led to the appearance of gaps between the aged Laponite suspension and the pore walls. This phenomenon can be observed by examining the texture of the aged Laponite inside the microfluidic device under a microscope or a high-resolution camera. These gaps cause the saturated and aged devices to not be able to contain hydrogen (FIG. 27 A). Properly aging samples required minimizing the potential for evaporation of the suspension by immersing the entire microfluidic device during the aging process in a batch of Laponite suspension (FIG. 27B). This procedure was adopted throughout this study.4,1.5. Hydrogen injection setup

[0242] An experimental setup 2800 capable of injecting hydrogen into microchips (microfluidic devices made herein) was constructed to evaluate the strength of the in-situ geobarrier formed by the Laponite suspension in a microfluidic device. The experimentalPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC setup 2800 is show n in FIG. 28. Table 3 shows selected components of the experimental setup 2800 for hydrogen injection into ini crochips.Table 3

[0243] An H-Cube® Mini Plus (Thales Nano), as a hydrogen gas generator 2825, was used to produce hydrogen via electrolysis of deionized (DI) water. This hydrogen gas generator 2825 eliminates the risks associated with handling hydrogen tanks in the laboratory. The system generates hydrogen at a maximum rate of 30 mL / min and water at 0.1 mL / min rate. Residual water was then separated via gravity -driven phase separation in a pressure-resistant glass separator 2817 (glass cylinder, 1 cm inner diameter, 30 cm length) equipped with a moisture filter 2815. A vessel for effluent water 2827 was coupled to the bottom of glass separator 2817 via a three-way valve 2831. Three-way valve 2831 allowed for selective fluid communication between various components of the experimental setup 2800.

[0244] The separated hydrogen was transferred to a floating piston accumulator 2819 (Phoenix Instrument, 40 cc volume). Pressure was regulated by injecting water from the bottom using pump 2821 (Teledyne ISCO D-500). A digital pressure transducer 2813 (ProSense SPTD25-20-1000H) with a range from 0 psig to 1000 psig (from 0 MPa to 6.9 MPa) and + / - 0.5% accuracy, was used to monitor the pressure, with measurements recorded at a rate of 5 datapoints per second. Pressure acquisition data was obtained usingPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC pressure acquisition hardware and software 2823 (NI Data Acquisition (DAQ) hardware (National Instruments) and LabVIEW software). This pressure acquisition hardware and software 2823 collected and converted the 4-20 mA analog output into digital data.

[0245] Once the desired pressure was reached inside the transfer vessel, the pressure profile was monitored for two minutes to check for system leaks. If pressure remained stable, three-way valve 2829 was opened, directing the pressurized hydrogen into a microfluidic chip 2807 containing aged Laponite via microfluidic chip inlet 2807a. The pressure profile was monitored for an additional two minutes. At each pressure step, the aged Laponite was exposed to pressurized hydrogen for at least four minutes. If no leakage was detected, the pressure was increased incrementally by about 10-25 psi (about 69-170 kPa). Three-way valve 2829 was also operationally coupled to pressure regulator 2803. Three-way valve 2829 allowed for selective fluid communication between various components of the experimental setup 2800.

[0246] The pressure profile served as a primary indicator of potential leaks. Due to the small hydrogen volume in the transfer vessel, a sharp pressure drop indicated breakthrough. In addition to pressure monitoring, two visual observation methods were employed: (i) a digital camera 2805 (Phase One IQ3, 60 MP achromatic sensor) captured images at the end of each injection step; and (ii) tubing connected to microfluidic chip outlet 2807b was submerged in a water bath 2809, allowing continuous, real-time monitoring of hydrogen breakthrough. The digital camera 2805 was operationally coupled to image acquisition hardware / software 2801 to view experimental results. Use of light table 2811 may allow for better visualization of the microfluidic chip 2807.4.2. Non-limiting Results4.2,1, Pre-shear / recovery step, viscosity evolution

[0247] Once steady-state shear viscosities were obtained at the end of the 1200-second shearing process, these values were plotted against their corresponding aging day. The results, presented in FIG. 29, show the evolution of steady-state shear viscosity over 30 days. From FIG. 29, it can be observed that viscosity increased logarithmically over time, particularly for the samples aged at room temperature and 45°C. However, the initial viscosity values and the rate of viscosity increase differed among the concentrations. The initial viscosities of the 2 wt%, 2.5 wt%, and 3 wt% suspensions were 0.018 Pa s, 0.031PCT Patent ApplicationAttorney Docket No.: UWYO-0130PCPa s, and 0.150 Pa s, respectively, measured within a few hours after preparation. These low initial viscosities may be useful for ensuring ease of injecting the suspension into porous media, whereas higher viscosity over time may be useful for forming a strong flow barrier that resists movement. The evolution of the microstructure was observed during 1500 second recovery period using oscillatory time sweep tests. The data indicated that, with time and concentration, the elastic modulus increases and this rate of increase is a function of clay concentration and temperature.4.2.2. Linear viscoelastic region - Strain amplitude sweep test

[0248] Strain amplitude sweep tests were performed for all samples under different aging conditions over 30 days. A purpose of these tests was to determine the LVE region, which is a prerequisite for oscillatory frequency sweep tests. FIGS. 30A-30C present representative strain amplitude sweep test results for 2 wt%, 2.5 wt%, and 3 wt% Laponite suspensions aged at room temperature, 45°C and 75°C, tested on the 4th day of aging. From FIGS. 30A-30C, the LVE region corresponds to a strain range of 1-10%, where a plateau in G' was observed for all cases. The crossover points of G' and G" marked the yield point, indicating the transition from solid-like to liquid-like behavior due to the breakdown of microstructure. The increase in G' and reduced fluctuations in G" at higher temperatures indicate stronger gels due to thermal effects. The yield points shifted to lower strains at higher aging temperatures, indicating that the gel structures became stiffer and more brittle. Unlike the 2 wt% and 2.5 wt% suspensions, the 3 wt% suspension exhibited minimal temperature dependence, suggesting that it rapidly formed a rigid structure upon preparation.4.2.3. Elasticity' evolution - oscillatory frequency sweep tests

[0249] Based on the strain amplitude sweep tests, a constant strain value of 1% was selected for the oscillatory frequency sweep tests, ensuring measurements remained within the LVE region to preserve microstructure integrity. The angular frequency during the test was varied from 0.01 rad / s to 100 rad / s. To identify a suitable Laponite concentration, the elastic modulus (G') was analyzed over aging time and temperature conditions. The representative smectite clay suspension / solution should exhibit lower elasticity immediately after preparation and progressively develop higher elasticity with increased aging time and the influence of elevated temperatures. FIGS. 31 A-31I present the evolutionPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC of G' for 2 wt% (FIGS. 31A-31C), 2.5 wt% (FIGS. 31D-31F), and 3 wt% (FIGS. 31G-31I) Laponite suspensions at various temperatures.

[0250] The results show that all samples exhibited increasing elasticity over time. Similar to the evolution of viscosity, the increase in elasticity at 75°C was greater than 45 °C, which in turn was higher than at room temperature. Additionally, the 3 wt% suspension exhibited high initial elasticity and minimal evolution in G', reinforcing the notion that its microstructure forms rapidly after preparation. The G' values for the 2 wt% and 2.5 wt% Laponite suspensions aged at 75°C surpassed that of the 3 wt% suspension after 11 days of aging, making them potentially better candidates for long-term containment applications.4.2.4. Microfluidic device

[0251] A microfluidic chip was fabricated with three replicated patterns on each substrate, enabling simultaneous aging of Laponite suspensions under different conditions. The porous media in the chips were 4.12 mm wide and 38.38 mm long, with a porosity of 32% and a permeability of 5 Darcy . The specific dimensions of the pattern design are shown in FIG. 32A.

[0252] The pore network pattern replicates characteristics of Berea Sandstone, including pore size distribution and pore throat distribution. The average depth of the pore network was measured to be approximately 17 pm using a 3D laser microscope (Olympus LEXT OLS4000). Permeability was determined using a modified version of the method described in S. Pradhan et al. "“A semi-experimental procedure for the estimation of permeability of microfluidic pore network.” (2019), MethodsX, 6. 704-713. The total pressure drop across the porous media chip (AP_chip) was measured at five flow rates (0.01 mL / min, 0.02 mL / min, 0.04 mL / min, 0.06 mL / min, and 0.08 mL / min). Accounting for pressure losses in the inlet and outlet lines, permeability was calculated using Darcy’s law from the slope of Darcy velocity versus AP / (p L), resulting in an average value of approximately 5 Darcy (see FIG. 32B).4.2.5. Hydrogen injection results

[0253] Under the conditions investigated, the rheological findings supported eliminating the 3 wt% suspension from injection tests due to its rapid gelation and limited elasticity evolution over aging at various temperatures. Also, the tests helped to select 75°CPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC as the aging temperature, which favors elasticity of the suspension over time. (G' modulus). Consequently, 2 wt% and 2.5 wt% suspensions were selected for further analysis. After preparation, 2 wt% and 2.5 wt% Laponite suspensions were immediately injected into the microfluidic chips and submerged in a sealed glass beaker for aging at 75°C. Injection pressure data from hydrogen inj ection experiments were recorded on aging days 1 , 4, 7, 11 , and 18. FIG. 33 presents a pressure profile for hydrogen injection into a microfluidic device containing a 2 wt% Laponite suspension aged at 75°C for various periods of time. The pressure profile serves as a reliable leak indicator, as even minor leaks cause a noticeable pressure drop. In most cases, a sudden pressure drop indicated a breakthrough, often accompanied by bubble formation at the outlet. FIG. 34 shows a pressure profile for hydrogen injection into a microfluidic device containing a 2.5 wt% Laponite suspension aged at 75°C.

[0254] The pressure tolerance of the system (breakthrough pressure) was found to increase as the Laponite suspension aged. Here, the results indicate that a 2 wt% Laponite suspension aged for 18 days withstood a pressure difference of about 105 psi (about 724 kPa), whereas a2.5 wt% Laponite suspension aged for 18 days at 75°C withstood a pressure difference of about 346 psi (about 2.39 MPa). Given the 38.38 mm length of the porous medium in the microfluidic chips, these results correspond to pressure gradients of about 834 psi / ft (about 18.9 MPa / m) and 2,749 psi / ft (about 62. 18 MPa / m) for the 2 wt% and 2.5 wt% 18-day aged Laponite suspensions, respectively. The scale of the experiments should be contemplated, as the length of the microfluidic device patterns where the Laponite was aged is only 38.38 mm. When extrapolating to the reservoir scale and assuming a linear relationship between pressure drop (AP) and the length of the porous medium, as described by Darcy’s law, a thicker geobarrier could proportionally withstand higher pressures. For example, if 18-day aged 2 wt% and 2.5 wt% Laponite suspensions withstand about 105 psi (about 724 kPa) and 346 psi (about 2.39 MPa), respectively, over 38.38 mm, then a 3- meter-thick barrier may withstand about 8,207 psi (about 56.59 MPa) and about 27,045 psi (about 186.47 MPa). These projected values are significantly higher than typical pressures observed in conventional underground hydrogen storage settings, which range from 700 psi to 3,000 psi (from 4.8 to 20.7 MPa) in salt caverns, and from approximately 1,450 psiPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC to 4,350 psi (approximately 9.99 to 29.9 MPa) in depleted oil and gas reservoirs and saline aquifers.

[0255] When breakthrough occurred, a sudden pressure drop was clearly observed, corresponding to hydrogen finding a preferential pathway. This was further confirmed through captured images. A properly aged Laponite suspension within the pore matrix of the microfluidic device appears nearly transparent under the digital camera (see FIG. 35A) and remains unchanged until the hydrogen breakthrough event takes place. When the hydrogen injection pressure reaches the maximum tolerable threshold, an abrupt breakthrough occurs, as illustrated in FIGS. 35A-35D.

[0256] The hydrogen-swept area (dark paths) at breakthrough pressure depended on the maturity' of the Laponite suspension. As observed in FIGS. 35A-35D, breakthrough was evident in all cases, with higher resistance to flow was observed in the more aged suspensions.4.5. Non-limiting Conclusions

[0257] This study investigated the use of Laponite suspensions at varying concentrations as potential in-situ geobarriers for geological hydrogen storage by assessing their rheological properties and hydrogen-blocking ability in a microfluidic device. The Laponite suspensions are example compositions comprising a swellable clay and an aqueous material according to aspects described herein.

[0258] A comprehensive rheological characterization was conducted for all three suspensions. Given the high thixotropic nature of Laponite. a pre-shear / recovery step was applied before testing. The pre-shear included 1200 seconds of shearing at a shear rate of 100 s ', followed by 1500 seconds of microstructure rebuild, during which small-amplitude time sweep tests were performed to monitor microstructure evolution. Steady -state shear viscosity values were measured over 30 days at different aging temperatures (room temperature, 45°C, and 75°C). The results showed a logarithmic increase in viscosity over time for all cases, especially at room temperature and 45°C. The rate of change in viscosity increased with aging temperature for all suspensions, with the highest rate observed at 75°C, followed by 45°C, and the lowest at room temperature (20°C). The 3 wt% suspension exhibited higher initial viscosity, and a relatively slower viscosity evolution compared to the 2 wt% and 2.5 wt% suspensions under the conditions tested. The 2 wt%, 2.5 wt%, andPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC3 wt% suspensions aged at 75°C exhibited an increase in viscosity from about 0.018 to about 1.06 Pa s, from about 0.03 to about 1.37 Pa s. and from about 0.15 to about 0.78 Pa s, respectively, between Day 1 and Day 30.

[0259] To further investigate the elastic behavior of Laponite suspensions, strain amplitude sweep tests and oscillation frequency sweep tests were performed. The linear viscoelastic region of each sample was first determined, followed by frequency sweep tests within this region to analyze the evolution of elastic behavior through storage modulus (G') and loss modulus (G"). Over 30 days of aging, all samples exhibited an increase in elastic modulus, with the most significant growth observed for the 2 wt% and 2.5 wt% suspensions aged at 75°C. The 2 wt%, 2.5 wt%, and 3 wt% suspensions aged at 75°C exhibited an increase in elastic modulus — from about 52 Pa to about 708 Pa, from about 94 Pa to about 1,166 Pa. and from about 253 Pa to about 706 Pa, respectively — measured at a reference angular frequency of co = 100 rad / s. These findings further confirmed the rapid gelation of the 3 wt% suspension, which attained high viscosity and elasticity prematurely, making it potentially undesirable for injection applications depending on the conditions.

[0260] Based on these findings, 2 wt% and 2.5 wt% Laponite suspensions were selected for further evaluation. A microfluidic device replicating the pore volume and pore throat distribution of Berea sandstone was fabricated using glass substrates and a chemical etching technique. After thorough characterization, 2 wt% and 2.5 wt% Laponite suspensions were injected into the microfluidic device and aged at 75°C for different durations. Hydrogen injection experiments were then conducted at various aging times using a custom-built hydrogen injection setup. This setup featured a flow reactor that generated hydrogen via electrolysis and injected it through a piston accumulator. Leakage and breakthrough events were monitored using a highly sensitive pressure transducer, a high-resolution camera, and direct visual observations of hydrogen bubble formation at the outlet.

[0261] The hydrogen injection pressure profiles and breakthrough pressures revealed that the 2 wt% Laponite suspension aged at 75°C for 18 days withstood a pressure difference of about 834 psi / ft (about 18.9 MPa / m), while the 2.5 wt% suspension tolerated a pressure difference of approximately 2,749 psi / ft (about 62.18 MPa / m) after 18 days ofPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC aging at the same temperature. These findings demonstrate the potential of Laponite suspensions as effective flow barriers for geological hydrogen storage applications.

[0262] Overall, Example 4 demonstrates that aspects described herein are useful for subsurface containment or storage of a fluid such as H2 gas, CO2, methanol, natural gas, or combinations thereof.Aspects Listing

[0263] The present disclosure provides, among others, the following aspects, each of which may be considered as optionally including any alternate aspects:

[0264] Aspect 1. A composition for subsurface containment or storage of a fluid, the composition comprising: an amount of a swellable clay in a range from about 1 wt% to about 5 wt% based on a total wt% of the composition, the total wt% of the composition equal to 100 wt%; and an aqueous material.

[0265] Aspect 2. The composition according to Aspect 1, wherein the fluid comprisesH2 gas, CO2, methanol, natural gas, or combinations thereof.

[0266] Aspect 3. The composition according to any one of the preceding Aspects, wherein the fluid comprises H2 gas.

[0267] Aspect 4. The composition according to any one of the preceding Aspects, wherein the clay comprises a mesoporous silicate clay.

[0268] Aspect 5. The composition according to any one of the preceding Aspects, wherein at least a portion of the clay is in the form of nanosized clay platelets.

[0269] Aspect 6. The composition of according to Aspect 5, wherein at least a portion of the nanosized clay platelets are disordered in an edge-to-face fashion at the mesoscopic level, optionally resulting in a continuous structure throughout the composition, while avoiding nematic gel formation, flocculation, and isotropic liquid formation.

[0270] Aspect 7. The composition of according to any one of Aspects 5-6, wherein at least a portion of the nanosized clay platelets form a continuous structure throughout the composition, and / or at least a portion of the nanosized clay platelets are in the form of a continuous structure throughout the composition.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0271] Aspect 8. The composition according to any one of Aspects 5-7, wherein at least a portion of the nanosized clay platelets are mesostructured when the pH of the composition is about 8 or higher, such as a pH in a range from about 9 to about 11.

[0272] Aspect 9. The composition according to any one of Aspects 5-8, wherein: the nanosized clay platelets are in a disordered edge-to-face fashion; and the nanosized clay platelets are crystalline.

[0273] Aspect 10. The composition according to any one of the preceding Aspects, wherein the composition is free, or substantially free, of face-to-face stacking of nanosized clay platelets.

[0274] Aspect 11. The composition according to any one of the preceding Aspects, wherein at least a portion of the clay is in the form of disordered edge-to-face nanolayers, the disordered edge-to-face nanolayers have a thickness in a range from about 0.8 nm to about 1.2 nm.

[0275] Aspect 12. The composition according to Aspect 11, wherein the composition is free, or substantially free, of a stacked nanolayer morphology of the nanosized clayplatelets.

[0276] Aspect 13. The composition according to any one of the preceding Aspects, wherein: at least a portion of the clay is in the form of clay platelets; and / or at least a portion of the clay platelets are disc-shaped (or substantially discshaped).

[0277] Aspect 14. The composition according to any one of the preceding Aspects, wherein: at least a portion of the clay is in the form of clay platelets; and one or both of: the clay platelets have an average thickness in a range from about 0.8 nm to about 1.2 nm, such as from about 0.9 nm to about 1 nm, such as about 0.92 nm; or the clay platelets have an average diameter of about 50 nm or less, such as in a range from about 10 nm to about 40 nm, such as from about 20 nm to about 30 nm, such as about 25 nm.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0278] Aspect 15. The composition according to any one of the preceding Aspects, wherein the amount of the swellable clay in the composition is: in a range from about 1 wt% to about 4.5 wt%. such as from about 1 wt% to about 4 wt% or from about 1.5 wt% to about 4.5 wt%, such as from about 1.5 wt to about 3.5 wt%, such as from about 2 wt% to about 3 wt%, such as from about 2.5 wt% to about 3 wt% based on the total wt% of the composition; in a range from about 1 wt% to about 3 wt%, such as from about 1.5 wt% to about 2.5 wt%, such as about 2 wt% based on the total wt% of the composition; or in a range from about 1.5 wt% to about 3 wt%, such as from about 1.6 wt% to about 2.9 wt%, such as from about 1.7 wt% to about 2.8 wt%, such as from about 1.8 wt% to about 2.7 wt%, such as from about 1.9 wt% to about 2.6 wt%, such as from about 2 wt% to about 2.5 wt%, such as from about 2.1 wt% to about 2.4 wt%, such as from about 2.2 wt% to about 2.3 wt% based on the total wt% of the composition.

[0279] Aspect 16. The composition according to any one of the preceding Aspects, wherein the swellable clay comprises smectite.

[0280] Aspect 17. The composition according to any one of the preceding Aspects, wherein the swellable clay comprises a lithium sodium magnesium silicate.

[0281] Aspect 18. The composition according to any one of the preceding Aspects, wherein the swellable clay comprises layered silicate sheets.

[0282] Aspect 19. The composition according to any one of the preceding claims, wherein the composition has a pH of about 8 or more, such as in a range from about 8 to about 14, such as from about 8 to about 12.

[0283] Aspect 20. The composition according to any one of the preceding Aspects, wherein the composition has a pH in a range from about 9 to about 11.

[0284] Aspect 21. The composition according to any one of the preceding Aspects, wherein the aqueous material comprises a salt.

[0285] Aspect 22. The composition according to any one of the preceding Aspects, wherein a concentration of salt (Cs, in units of Molarity) in the composition and a concentration of smectite (Cw, in units of wt%) in the composition are located in the isotropic gel (or glass) region (1G region) of the Cs-Cw phase diagram (at a pH of about 10) shown in FIG. 5.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0286] Aspect 23. The composition according to any one of the preceding Aspects, wherein, when the composition comprises from about 1.8 wt% to about 2.7 wt% of the swellable clay and a pH of the composition is about 10. the concentration of salt in the composition is about 9x 102M or less (about 0.09 M or less), such as in a range from about 1 * 104M to about 9x 102M.

[0287] Aspect 24. The composition of according to any one of the preceding Aspects, wherein intercalation of the fluid in or between two or more layers of the swellable clay increases the viscosity and elasticity of the composition.

[0288] Aspect 25. The composition according to any one of the preceding Aspects, wherein the composition has an improved flow barrier to a fluid upon exposure of the composition to a temperature greater than ambient temperature relative to exposure of the composition to a temperature of ambient temperature.

[0289] Aspect 26. The composition according to any one of the preceding Aspects, wherein the composition is a time-dependent soft solid.

[0290] Aspect 27. The composition according to any one of the preceding Aspects, wherein the composition has non-Newtonian characteristics.

[0291] Aspect 28. The composition according to any one of the preceding Aspects, wherein, upon aging, the composition sen es as a container for the fluid and a flow' barrier for the fluid.

[0292] Aspect 29. The composition according to any one of the preceding claims, wherein the composition is capable of remaining in a pumpable and / or injectable fluid state for a period of about 1 day (24 hours) or less.

[0293] Aspect 30. The composition according to any one of the preceding Aspects, wherein the composition has an initial density in a range from about 1 g / mL to about 1.3, such as from about 1 g / mL to about 1.1 g / mL.

[0294] Aspect 31. The composition according to any one of the preceding Aspects, w herein the composition: has a density7after aging for 4 days at 20°C that is in a range from about 1 g / mL to about 1.3 g / mL; and the structure of the composition after aging for 4 days at 20°C is more crystalline than the structure of the composition after aging for 1 day (24 hours) at 20°C.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0295] Aspect 32. The composition according to any one of the preceding Aspects, wherein the composition has: a steady-state shear viscosity' in a range from about 0.001 Pa s to about 0.1 Pa s, such as from about 0.005 Pa s to about 0.07 Pa s, such as from about 0.01 Pa s to about 0.05 Pa s, such as from about 0.015 Pa s to about 0.036 Pa s, such as from about 0.018 Pa s to about 0.031 Pa s for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 20° C for t=l hour).

[0296] Aspect 33. The composition according to any one of the preceding Aspects, wherein the composition has an elastic modulus in the linear viscoelastic region in a range from about 0.4 Pa to about 10 Pa for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 20°C for t=l hour).

[0297] Aspect 34. The composition according to any one of the preceding Aspects, wherein the composition has an elastic modulus in the linear viscoelastic region in a range from about 8 Pa to about 12 Pa for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 75°C for t=24 hours).

[0298] Aspect 35. The composition according to any one of the preceding Aspects, wherein, after the composition ages for 24 hours or more, the composition is a soft solid with a higher steady-state shear viscosity and a higher elastic modulus than a steady-state shear viscosity and an elastic modulus of the composition that is aged for 1 hour.

[0299] Aspect 36. The composition according to any one of the preceding Aspects, wherein, after the composition ages for 30 days: the composition is characterized as the soft solid.

[0300] Aspect 37. The composition according to any one of the preceding Aspects, wherein, after the composition ages for 30 days: the composition is characterized as the soft solid; and the composition is characterized by one or more of: an elastic modulus in the linear viscoelastic region in a range from about 90 Pa to about 220 Pa, such as from about 95 Pa to about 200 Pa, such as from about 100 Pa to about 205 Pa, such as from about 110 Pa to about 210 Pa for a composition comprisingPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 20°C for t=30 days at an angular frequency of oscillation of 0.01 rad / s and a shear strain of 1%); an elastic modulus in the linear viscoelastic region in a range from about 420 Pa to about 660 Pa, such as from about 440 Pa to about 650 Pa, such as from about 430 Pa to about 640 Pa, such as from about 420 Pa to about 630 Pa for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 45°C for t=30 days at an angular frequency of oscillation of 0.01 rad / s and a shear strain of 1%); an elastic modulus in the linear viscoelastic region in a range from about 550 Pa to about 1,250 Pa, such as from about 550 Pa to about 1,225 Pa, such as from about600 Pa to about 1,200 Pa, such as from about 650 Pa to about 1.175 Pa, such as from about675 Pa to about 1,150 Pa, such as from about 700 Pa to about 1,100 Pa, such as from about708 Pa to about 1,066 Pa for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 75 °C for t=30 days at an angular frequency of oscillation of 0.01 rad / s and a shear strain of 1%); or combinations thereof.

[0301] Aspect 38. The composition according to any one of the preceding Aspects, wherein, after the composition ages for 30 days: the composition is characterized as the soft solid; and the composition is characterized by one or more of: a steady-state shear viscosity in a range from about 0.1 Pa s to about 0.25 Pa s, such as from about 0.11 Pa s to about 0.22 Pa s, such as about 0.12 Pa s or about 0.22 Pa s for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 20°C for t=30 days at a shear rate (y) of 100 s '): a steady-state shear viscosity in a range from about 0.15 Pa s to about 0.70 Pa s, such as from about 0. 18 Pa s to about 0.60 Pa s, such as from about 0.39 Pa s to about 0.66 Pa s. such as from about 0.4 Pa s to about 0.68 Pa s for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 45°C for t=30 days at a shear rate (y) of 100 s '):PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC a steady-state shear viscosity in a range from about 0.38 Pa s to about 1.5 Pa s, such as from about 0.4 Pa- s to about 1.2 Pa- s, such as from about 0.5 Pa- s to about 1.3 Pa s, such as from about 1.1 Pa s to about 1.4 Pa s for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 75°C for t=30 days at a shear rate (y) of 100 s '): or combinations thereof.

[0302] Aspect 39. The composition according to any one of the preceding Aspects, wherein after the composition ages for 18 days: the composition is characterized as the soft solid; and the composition is characterized as having a breakthrough pressure, across a 38.38 mm-long porous medium, in a range from about 18 psi to about 405 psi (about 0. 12 MPa to about 2.79 MPa), such as from about 68 psi to about 382 psi (about 0.47 MPa to about 2.63 MPa), such as from about 88 psi to about 362 psi (about 0.61 MPa to about 2.50 MPa), such as from about 99 psi to about 351 psi (about 0.68 MPa to about 2.42 MPa), such as from about 105 psi to about 346 psi (about 0.724 MPa to about 2.39 MPa) for a composition comprising an amount of the clay in a range from about 1.8 wt% to about 2.7 wt% (measured after aging the composition at 75°C for t=l 8 days).

[0303] Aspect 40. A set-delayed composition for subsurface containment or storage of a fluid, the set-delayed composition comprising: an amount of a swellable clay in a range from about 1 wt% to about 5 wt% based on a total wt% of the composition, the total wt% of the composition equal to 100 wt%; and an aqueous material.

[0304] Aspect 41. The set-delayed composition according to Aspect 40, wherein the fluid comprises H2 gas, CO2. methanol, natural gas, or combinations thereof.

[0305] Aspect 42. The set-delayed composition according to any one of Aspects 40-41 , wherein the fluid comprises H2 gas.

[0306] Aspect 43. The set-delayed composition according to any one of Aspects 40-42, wherein the set-delayed composition comprises the composition according to any one of Aspects 1-39.

[0307] Aspect 44. A set-delayed composition for subsurface containment or storage of a fluid, the set-delayed composition comprising:PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC an amount of a swellable clay in a range from about 1 wt% to about 5 wt% based on a total wt% of the set-delayed composition, the total wt% of the set-delayed composition equal to 100 wt%; and an aqueous material.

[0308] Aspect 45. The set-delayed composition according to Aspect 44, wherein the set-delayed composition comprises the composition according to any one of Aspects 1-43.

[0309] Aspect 46. The set-delayed composition according to any one of Aspects 44-45, wherein the fluid comprises H2 gas, CO2, methanol, natural gas, or combinations thereof.

[0310] Aspect 47. The set-delayed composition according to any one of Aspects 44-46, wherein the fluid comprises H2 gas.

[0311] Aspect 48. The set-delayed composition according to any one of Aspects 44-47, wherein the amount of the swellable clay in the set-delayed composition is in a range from about 1.8 wt% to about 2.7 wt%.

[0312] Aspect 49. The set-delayed composition according to any one of Aspects 44-48, wherein the swellable clay comprises smectite.

[0313] Aspect 50. The set-delayed composition according to any one of Aspects 44-49, wherein the swellable clay comprises a lithium sodium magnesium silicate.

[0314] Aspect 51. The set-delayed composition according to any one of Aspects 44-50, wherein the swellable clay is represented by formula (I):Na+a[Mg6-aLiaSi8O20(OH)4] (I), wherein: a of formula (I) is the degree of isomorphous substitution of Li+for Mg2+.

[0315] Aspect 52. The set-delayed composition according to any one of Aspects 44-51, wherein at least a portion of the swellable clay is in the form of nanosized clay platelets.

[0316] Aspect 53. The set-delayed composition according to Aspect 52, wherein at least a portion of the nanosized clay platelets are in the form of a continuous structure throughout the set-delayed composition.

[0317] Aspect 54. The set-delayed composition according to any one of Aspects 52-53, wherein: at least a portion of the nanosized clay platelets are disordered in an edge-to-face fashion at the mesoscopic level; and the nanosized clay platelets are crystalline. Aspect 55.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PCThe set-delayed composition according to any one of Aspects 44-54, wherein the set- delayed composition has a pH in a range from about 8 to about 12.

[0318] Aspect 56. The set-delayed composition according to any one of Aspects 44-55, wherein: at least a portion of the swellable clay is in the form of nanosized clay platelets; and at last a portion of the nanosized clay platelets are mesostructured when the pH of the set-delayed composition is in a range from about 8 to about 12.

[0319] Aspect 57. The set-delayed composition according to any one of Aspects 44-56, wherein the set-delayed composition is aged at a temperature in a range from about 50°C to 100°C.

[0320] Aspect 58. The set-delayed composition according to any one of Aspects 44-57, wherein, when the set-delayed composition comprises from about 1.8 wt% to about 2.7 wt% of the swellable clay and a pH of the set-delayed composition is about 10, a concentration of salt in the set-delayed composition is about 0.09 M or less.

[0321] Aspect 59. The set-delayed composition according to any one of Aspects 44-58, wherein: the set-delayed composition is a time-dependent soft solid; and the set-delayed composition has non-Newtonian characteristics.

[0322] Aspect 60. The set-delayed composition according to any one of Aspects 44-58, wherein the set-delayed composition is characterized as having a breakthrough pressure, across a 38.38 mm-long porous medium, in a range from about 20 psi to about 400 psi (measured after aging the set-delayed composition at 75°C for 1=18 days).

[0323] Aspect 61. A subsurface storage or containment system for a fluid, comprising: a porous medium, such as a rock; and a composition comprising: an amount of a swellable clay in a range from about 1 wt% to about 5 wt% based on a total wt% of the composition, the total wt% of the composition equal to 100 wt%; and an aqueous material.

[0324] Aspect 62. The subsurface storage or containment system according to Aspect 61 , wherein the amount of the swellable clay in the composition is in a range from about 1.8 wt% to about 2.7 wt%.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0325] Aspect 63. The subsurface storage or containment system according to any one of Aspects 61-63, wherein the fluid comprises H2 gas, CO2, methanol, natural gas, or combinations thereof.

[0326] Aspect 64. The subsurface storage or containment system according to any one of Aspects 61-63, wherein the fluid comprises H2 gas.

[0327] Aspect 65. The subsurface storage or containment system according to any one of Aspects 61-64, wherein the composition comprises the composition according to any one of Aspects 1-60.

[0328] Aspect 66. A subsurface storage or containment system for a fluid, comprising: a porous medium (e.g., a rock); hydrated interlayers of a sw ellable clay; and hydrogen molecules disposed in interlayer spaces between the hydrated interlayers of the swellable clay.

[0329] Aspect 67. The subsurface storage or containment system according to Aspect 66, wherein the hydrated interlayers of the swellable clay are formed from a composition described herein, such as a composition according to any one of Aspects 1-60.

[0330] Aspect 68. The subsurface storage or containment system according to claim 19, wherein the swellable clay comprises a smectite clay.

[0331] Aspect 69. A process for forming a subsurface storage or containment system for a fluid, comprising: introducing a composition comprising a swellable clay and an aqueous material into a subsurface formation, the composition comprising an amount of the swellable clay in a range from about 1 wt% to about 5 wt% based on a total wt% of the composition, the total wt% of the composition equal to 100 wt%.

[0332] Aspect 70. The process according to Aspect 69, wherein the fluid comprises H2 gas, CO2, methanol, natural gas, or combinations thereof.

[0333] Aspect 71. The process according to any one of Aspects 69-70, wherein the fluid comprises H2 gas.

[0334] Aspect 72. The process according to any one of Aspects 69-71. wherein the composition comprises the composition according to any one of Aspects 1-60.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC

[0335] Aspect 73. The process according to any one of Aspects 69-72, wherein the subsurface storage or containment system formed comprises any suitable subsurface storage or containment system described herein, for example, the subsurface storage or containment system according to any one of Aspects 61-68.

[0336] Aspect 74. The process according to Aspect any one of Aspects 69-73, wherein the composition is introduced into a vertical and / or horizontal well of the subsurface formation.

[0337] Aspect 75. The process according to any one of Aspects 69-74, wherein introducing the composition into the subsurface comprises injecting or pumping the composition into the subsurface.

[0338] In the foregoing, reference is made to aspects of the disclosure. However, it should be understood that the disclosure is not limited to specific described aspects. Instead, any combination of the following features and elements, whether related to different aspects or not, is contemplated to implement and practice the disclosure. Furthermore, although aspects of the disclosure may achieve advantages over other possible solutions and / or over the prior art, whether or not a particular advantage is achieved by a given aspect is not limiting of the disclosure. Thus, the foregoing aspects, features, embodiments, implementations, and advantages are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in a claim(s). Likewise, reference to ‘‘the disclosure'’ shall not be construed as a generalization of any inventive subject matter described herein and shall not be considered to be an element or limitation of the appended claims except where explicitly recited in a claim(s).

[0339] As is apparent from the foregoing general description and the specific aspects, while forms of the aspects have been illustrated and described, various modifications may be made without departing from the spirit and scope of the present disclosure. Accordingly, it is not intended that the present disclosure be limited thereby. Likewise, the term “comprising” is considered synonymous with the term “including.” Likewise whenever a formulation, a composition, an element or a group of elements is preceded with the transitional phrase “comprising,” it is understood that we also contemplate the same formulation, composition or group of elements with transitional phrases “consisting essentially of,” “consisting of,” “selected from the group of consisting of,” or “Is”PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC preceding the recitation of the formulation, composition, element, or elements and vice versa, for example, the terms “comprising,” “consisting essentially of,” “consisting of’ also include the product of the combinations of elements listed after the term.

[0340] References cited herein are incorporated by reference herein in their entirety to indicate the state of the art as of their publication or filing date and it is intended that this information may be employed herein, if desired, to exclude specific aspects that are in the prior art.

[0341] For purposes of this present disclosure, and unless otherwise specified, all numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and consider experimental error and variations that would be expected by a person having ordinary skill in the art. It will be further understood that there are a number of values disclosed therein, and that each value is also herein disclosed as “about” that particular value in addition to the value itself. In aspects, use of the term “about” may refer to ±20% of the stated value, ±15% of the stated value, ±10% of the stated value, ±5% of the stated value, ±3% of the stated value, ±2% of the stated value, or ±1% of the stated value.

[0342] For the sake of brevity, only certain ranges are explicitly disclosed herein. However, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, within a range includes every point or individual value between its end points even though not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited. For example, by disclosing a wt% from 1 wt% to 5 wt%, an intent is to recite individually 1 wt%, 2 wt%, 3 wt%, 4 wt%, and 5 wt%, including any sub-ranges and combinations of sub-ranges encompassed therein such that any of the foregoing numbers may be used singly to describe an open-ended range or in combination to describe a close-ended range. %Moreov er, all numerical end points of ranges disclosed herein are approximate, unless excluded by proviso. As a representative example, if a composition includes 1 wt% to 5 wt% of aPCT Patent ApplicationAttorney Docket No.: UWYO-0130PC substance, this range should be interpreted as encompassing temperatures in a range from “about'’ 1 wt% to “about” 5 wt%.

[0343] As used herein, the indefinite article “a” or “an” shall mean “at least one” unless specified to the contrary or the context clearly indicates otherwise. For example, aspects comprising “a salt” include aspects comprising one, two, or more salts, unless specified to the contrary or the context clearly indicates only one salt is included.

[0344] While the foregoing is directed to aspects of the present disclosure, other and further aspects of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

PCT Patent ApplicationAttorney Docket No.: UWYO-0130PCClaimsWhat is claimed is:

1. A set-delayed composition for subsurface containment or storage of a fluid, the set- delayed composition comprising: an amount of a swellable clay in a range from about 1 wt% to about 5 wt% based on a total wt% of the set-delayed composition, the total wt% of the set-delayed composition equal to 100 wt%; and an aqueous material.

2. The set-delayed composition according to claim 1, wherein the fluid comprises H2 gas, CO2. methanol, natural gas, or combinations thereof.

3. The set-delayed composition according to claim 1, wherein the fluid comprises H2 gas.

4. The set-delayed composition according to claim 1, wherein the amount of the swellable clay in the set-delayed composition is in a range from about 1.8 wt% to about 2.7 wt% based on the total wt% of the set-delayed composition.

5. The set-delayed composition according to claim 1, wherein the swellable clay comprises smectite.

6. The set-delayed composition according to claim 1, wherein the swellable clay comprises a lithium sodium magnesium silicate.

7. The set-delayed composition according to claim 1, wherein the swellable clay is represented by formula (I):Na+“[Mg6-aLiaSis02o(OH)4] (I), wherein: a of formula (I) is the degree of isomorphous substitution of Li+for Mg2+.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC8. The set-delayed composition according to claim 1, wherein at least a portion of the swellable clay is in the form of nanosized clay platelets.

9. The set-delayed composition according to claim 8, wherein at least a portion of the nanosized clay platelets are in the form of a continuous structure throughout the set-delayed composition.

10. The set-delayed composition according to claim 8, wherein: at least a portion of the nanosized clay platelets are disordered in an edge-to-face fashion at the mesoscopic level; and the nanosized clay platelets are crystalline.

11. The set-delayed composition according to claim 1, wherein the set-delayed composition has a pH in a range from about 8 to about 12.

12. The set-delayed composition according to claim 1, wherein: at least a portion of the swellable clay is in the form of nanosized clay platelets; and at last a portion of the nanosized clay platelets are mesostructured when the pH of the set-delayed composition is in a range from about 8 to about 12.

13. The set-delayed composition according to claim 1. wherein the set-delayed composition is aged at a temperature in a range from about 50°C to 100°C.

14. The set-delayed composition according to claim 1, wherein, when the set-delayed composition comprises from about 1.8 wt% to about 2.7 wt% of the swellable clay and a pH of the set-delayed composition is about 10, a concentration of salt in the set-delayed composition is about 0.09 M or less.

15. The set-delayed composition according to claim 1, wherein: the set-delayed composition is a time-dependent soft solid; and the set-delayed composition has non-Newtonian characteristics.PCT Patent ApplicationAttorney Docket No.: UWYO-0130PC16. The set-delayed composition according to claim 1, wherein the set-delayed composition is characterized as having a breakthrough pressure, across a 38.38 mm-long porous medium, in a range from about 20 psi to about 400 psi (measured after aging the set-delayed composition at 75°C for t=18 days).

17. A subsurface storage or containment system for a fluid, comprising: a porous medium; and a composition comprising: an amount of a swellable clay in a range from about 1 \vt% to about 5 wt% based on a total wt% of the composition, the total wt% of the composition equal to 100 wt%; and an aqueous material.

18. The subsurface storage or containment system according to claim 17, wherein the amount of the swellable clay in the composition is in a range from about 1.8 wt% to about 2.7 wt%.

19. A subsurface storage or containment system for H2, comprising: a porous medium; hydrated interlayers of a swellable clay; and hydrogen molecules disposed in interlayer spaces between the hydrated interlayers of the swellable clay.

20. The subsurface storage or containment system according to claim 19, wherein the swellable clay comprises a smectite clay.

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