Injection of carbon dioxide nanobubbles in a subterranean formation

Abstract

Sequestering carbon in a subterranean formation by injecting a waste slurry having entrained carbon dioxide nanobubbles.

Description

[0001] TITLE: INJECTION OF CARBON DIOXIDE NANOBUBBLES

[0002] IN A SUBTERRANEAN FORMATION

[0003] Cross-Reference to Related Applications

[0004] This is an International Application for Patent under the auspices of the PCT and claims priority to U.S. Provisional application number 63 / 657,097, filed June 6, 2024.

[0005] FIELD

[0006]

[0001] The disclosed methods and apparatus generally relate to methods for preparing and injecting a waste slurry containing carbon dioxide (CO2) nanobubbles into a subterranean formation.

[0007] BACKGROUND

[0008]

[0002] It is known to inject slurry waste, such as organic waste or drilling waste into a subterranean formation for long-term storage or sequestration of the waste. Slurry waste is often injected into the formations during an injection process having multiple, sequential injections, often in batches. Often such injection procedures are fracturing injections, that is, where the slurry is pumped into the formation above fracturing pressure, thereby fracturing (“fracking”) the formation. The waste slurry is injected into a target zone during a waste injection or disposal operation.

[0009]

[0003] In an effort to reduce the effects of global climate change, industry is seeking ways to reduce carbon release into the environment and to reduce the total carbon in the environment. One source of carbon is organic waste, which is high in carbon content, has little or no commercial value, and is prime for long term or permanent storage or sequestration in subterranean formations by injection well operations. Sequestration includes using a slurry of organic waste, bearing carbon, which is prepared and injected into the subterranean formation for permanent storage to isolate the waste from the surface and atmosphere.

[0010] BRIEF DESCRIPTION OF THE DRAWINGS

[0011]

[0004] Drawings of the preferred embodiments of the present disclosure are attached hereto so that the embodiments of the present disclosure may be better and more fully understood:

[0012]

[0005] FIG. 1 is a schematic of an exemplary injection well disposal operation and surface processing according to aspects of the disclosure.

[0013] DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

[0014]

[0006] The disclosed methods and apparatus generally relate to methods for preparing and injecting a waste slurry containing carbon dioxide (CO2) nanobubbles into a subterranean formation. FIG. 1 is a schematic of an exemplary injection well disposal operation and surface processing according to aspects of the disclosure and is discussed throughout.

[0015]

[0007] One method of injecting carbon into a subterranean formation for sequestration or disposal is the direct injection of carbon dioxide. Obviously, carbon dioxide is a gas at normal temperatures and pressures, so injection requires pressurizing the carbon dioxide, usually to supercritical stage at the surface prior to injection. This requires raising and maintaining both the temperature and the pressure of the carbon dioxide such that it remains in a supercritical state. This requires energy, pressure rated tanks and piping, etc. Further, the pressure must be maintained during the pumping and injection operation.

[0016] Carbon Dioxide Nanobubbles

[0017]

[0008] The disclosed methods utilize relatively stable nanobubbles of carbon dioxide in a slurry to inject the carbon dioxide into a subterranean formation, eliminating the need for high pressurization of the carbon dioxide gas prior to injection.

[0018]

[0009] In the methods disclosed herein, the carbon dioxide is in the form of nanobubbles and / or microbubbles. The terms are not used interchangeably herein. Microbubbles, as used herein, refers to bubbles which are 100 nanometers to 100 micrometers in diameter, that is, 100-100,000 nanometers. Microbubbles small size, in comparison to more typical macrobubbles, results in a large surface area-to-volume ratio, facilitating efficient gas-liquid mass transfer. Microbubbles have a slow buoyancy and so tend to remain entrained in the liquid longer than macrobubbles. Microbubbles have a higher internal pressure that macrobubbles, and lower internal pressure than nanobubbles. Microbubbles also tend to dissolve into the bearing liquid rather than escaping the liquid.

[0019]

[0010] Nanobubbles, for purposes of this disclosure, refers to bubbles which are 1-100 nanometers in diameter. Nanobubbles are extremely small and tend to be stable in a carrying liquid, as they lack significant buoyancy. Nanobubbles can remain entrained in liquid for weeks or months. Nanobubbles have a higher internal pressure than microbubbles. The extremely small size of nanobubbles results in an extraordinarily high surface area-to-volume ratio.

[0020] [Oil] Nanobubbles of carbon dioxide can be created using methods and processes known in the art in surface vessels and facilities 14 and not discussed in detail herein. Exemplary methods include those mentioned below without limitation. Some methods of nanobubble creation will be more efficient in heavier waste slurries. Nanobubbles can be created using hydrodynamic cavitation wherein liquid is forced through a nozzle or orifice at high speed. Nanobubbles can be created in a liquid using a venturi nozzle, venturi injector or the like. Nanobubbles can be created or enhanced using ultrasonic cavitation wherein high-frequency ultrasonic waves are used to create pressure changes in the liquid. In such a method, dissolved carbon dioxide forms nanobubbles. Carbon dioxide nanobubbles can be created by passing the gas through nanoporous media such as nanoporous membranes, sometimes called membrane sparging. Similarly, carbon dioxide nanobubbles can be created by injection of the gas through appropriately sized filters. Carbon dioxide nanobubbles can be created by rapid depressurization of dissolved carbon dioxide in a liquid. Physical irritation can be applied to larger carbon dioxide bubbles (macrobubbles) in a fluid, creating nanobubbles. Nanobubbles can be created on the surface of a solid immersed in a liquid, for example, by alcohol-water exchange or gas supersaturation.

[0021]

[0012] Microbubbles can be created using methods and apparatus known in the art. For example, microbubbles can be generated using mechanical agitation, sonication, vortex mixing, electrospray, atomization, or microfluidic processes.

[0022]

[0013] The process for creating microbubbles or nanobubbles in a slurry may include intermediate steps, such as, without requirement or limitation, dissolving carbon dioxide in a carrier liquid or first liquid 16 prior to mixing the CO2-laden liquid into a slurry, dissolving CO2 into a liquid prior to creating the bubbles in the liquid, adding one or more chemicals such as surfactants, lipids, or the like, to a liquid or the slurry, etc.

[0023]

[0014] A carbon dioxide supply or source 12 is needed to provide the CO2 for entrainment in the waste slurry 18. Since a goal of the disclosure is to sequester waste carbon dioxide, the source 12 can be a supply of waste carbon dioxide. For example, power plants using fossil fuels generate considerable waste carbon dioxide. Industrial waste carbon dioxide is common from industries such as steel production, cement production, chemical production such as lime and ammonia production, and refining industries. Oil and gas production can also be a supply of waste carbon dioxide. Preparation of an Injectable Waste Slurry

[0024]

[0015] An injectable waste slurry is a carbon-bearing waste slurry and can include bio-sludge, organic waste, or oil and gas drilling waste (such as frack waste-water and the like). The slurry includes both liquid and solids. The slurry must be properly prepared for injection into a subterranean zone by injection or fracturing injection.

[0025]

[0016] Carbon-bearing waste is prepared into an injectable slurry using combinations of the carbon-bearing waste and mixing with an available liquid or water supply. The liquid supply can be treated or untreated waste-water, brackish water, filtrate water, produced water, brine, freshwater, saltwater, etc., based on the location of the operation. The process includes preparation of a slurry suitable for injection, or fracturing injection, in an injection well. Such processes may include filtering, grinding or other preparation or removal of unsuitable solids, for example. Fluid weight and viscosity may be altered through the addition of additives, removal of material, etc. These materials need to be slurrified, which includes particle size degradation, oversized particle removal, and mixing or blending with a carrier fluid. It can also include viscosifying the final fluid, adding chemicals to change pH or to accelerate or decelerate microbial action, etc.

[0026]

[0017] Carbon-bearing waste fluids 22, often in non-slurry form, are prepared in surface facilities 20 into a slurry 18. Preparation can include sifting and screening, separation, grinding of particles, rheological treatment, addition of selected bacteria and organisms, dilution, dewatering and the like. The waste materials can include wastes produced during exploration, drilling, completion, and production phases of oil and gas operations. Further, waste materials can be by-products of sewage treatment processes, biosolid waste fluids, waste organic materials, such as food and animal waste, or contaminated materials. Further, waste materials can come from post-industrial operation waste, carbon-bearing materials created for sequestration, and other sources as are known in the art. Waste fluids can be delivered to the injection site by pipeline, truck, from an onsite or off-site slurry or sewage facility, etc. The slurry or a slurry concentrate can be held in storage tanks 24 prior to injection.

[0027]

[0018] The bubbles of carbon dioxide are entrained into the waste slurry. The bubbles can be created or entrained into a first liquid 28, such as a water or water-based liquid, during an earlier step, wherein the first liquid is not an injectable slurry or not for injection. Methods for creating carbon dioxide bubbles are addressed above. It may be easier in some embodiments to create a CO2 bubble-bearing first liquid 16, rather than creating the CO2 bubbles directly in the waste slurry 18. The CO2 bubble-bearing first liquid 16 can then be mixed with the waste slurry 18, or mixed with a pre-slurry liquid which itself is added to or used to create the slurry. Various tanks, pressure tanks, pressure pumps, fluid control circuits, valving and the like can be used in the process as is understood by those of skill int the art.

[0028]

[0019] The carbon dioxide bubbles can alternately be created in the slurry directly, creating a CO2 bubble-bearing slurry. Methods for creating carbon dioxide bubbles are addressed above.

[0029] Injection of Waste Slurry Bearing Carbon Dioxide Nanobubbles into a Subterranean Zone

[0020] The prepared CO2 bubble-bearing slurry 14 is injected into a subterranean zone 30 specifically chosen for the purpose. The slurry is injected into a formation zone made of porous rock or the like, and the process can include fracturing injection. (Unless stated otherwise herein, a subterranean zone does not include a cavern but rather is made up of rock.)

[0030]

[0021] Fracturing injection of a slurry is done at above fracture pressure for the formation. The formation must be isolated, such as by impermeable strata above 32 and below 34 the target zone, such that the injected slurry does not encroach other zones. Fracturing injection is known in the art and not described in detail here. The injection of solid carbon-bearing wastes in the form of a slurry into a subterranean formation can be done above the fracturing gradient of the formation.

[0031]

[0022] In some cases, the solids in the slurry make injection without fracturing infeasible as the non-fractured pore space is not large enough to inject the solids particles. Consequently, fracturing injection can be required, as it provides large enough fractures and cracks for the injection and retention of the solids particles.

[0032]

[0023] The solids content of the slurry is preferably below 50% by volume, with particle sizes of less than 1000 microns, or preferably less than 500 microns, or more preferably less than 300 microns. The slurry must be fluidly viscous as it must be injected at a relatively high flow rate.

[0033] Exemplary Injection Well

[0034]

[0024] FIG. 1 is a schematic of an exemplary injection well operation and surface processing according to aspects of the disclosure. An injection well 40 has a wellbore 42 extending through the targeted zone 30 or zones. An injection well 40 may be a converted production well in a formation or zone depleted of its hydrocarbons or a dedicated disposal or injection well. The wellbore 42 is typically cased 12 along at least a portion of its depth. One or more tubulars 10 can be positioned in the wellbore and injection can occur through the tubulars or along the annulus between the wellbore and tubular. Downhole tools, as is known in the art, can be employed during injection and hydraulic fracturing operations such as packers 46, seals, valves, screens, and measuring and sensing equipment (such as pressure sensors, bottom hole sensors, etc.). Measurement equipment can sense, record, and transmit data representative of temperature pressure, flow rate, acidity, etc., as measured at the surface, in the wellbore, at the bottom of the hole, etc. At issue here are pressure sensors for measuring or allowing calculation of formation pressure after shut-in of the well after waste fluid injection operations. Measurements may be made at downhole, wellbore, wellhead locations.

[0025] Pumping equipment, such as an injection pump 48 is positioned at the wellhead 50 to pump waste fluids into the wellbore under pressure. Injectate is pumped into the wellbore and into the target subterranean zone 30. The target zone 30 is bounded above by zone 32 and below by zone 34 which do not allow migration of injected slurry or materials out of zone 30. In some embodiments, the injectate is pumped under pressure above the fracture gradient resulting in fractures in the zone. In other embodiments, the zone includes a cavern and the injectate is injected into the cavern. Associated operational valving, controls, and safety valves are known in the art and are represented here by a single block.

[0035]

[0026] Waste containing material is transported to an injection site, the organic waste containing material having a solids content. Various surface equipment for treating and storing the carbon- bearing waste can be employed as is known in the art. The surface equipment can include tanks, pumps, grinders, filters, weirs, centrifuges, and various other equipment. The surface equipment can be used to perform the various tasks described elsewhere herein in preparing the transported materials into a slurry injectate and the like. The equipment can also be used to place additives from an additive source 26, such as surfactants, into a first liquid during or before creation of micro- or nanobubbles, or into the waste slurry.

[0036]

[0027] The waste slurry injectate bears carbon dioxide nanobubbles or microbubbles. Hence it is not necessary to maintain the injectate at temperatures and / or pressures needed to keep the carbon dioxide at supercritical phase. When the terms “microbubble” or “nanobubble” are used, it necessitates that the bubbles are in gaseous phase, and not liquid or supercritical phase. It is therefore not necessary to explicitly state that the bubbles or the liquid bearing the bubbles are below a pressure necessary for maintaining the carbon dioxide in supercritical or liquid phase. It is not possible to state a single pressure (or temperature, or combination) at which this is true, as it will depend on the characteristics of the injectable slurry. For example, generally carbon dioxide exists as a supercritical fluid at about 31 degrees Celsius and about 1070 psi. Hence, the carbon dioxide is not supercritical at a lower temperature and / or pressure. However, the injectable slurry bearing carbon dioxide nanobubbles, for example, can be stored and injected at temperatures and pressures well below these ranges. One of the advantages of the disclosure is in not having to pressurize the carbon dioxide or the CO2 bubble-bearing slurry at high pressure, high temperature, or both. The slurry may be pumped under pressure for purposes of injection or fracturing injection, obviously.

[0037]

[0028] In some embodiments, the nanobubbles or microbubbles are in gaseous phase in surface storage and at the wellhead during the injection process, but move to the supercritical phase at reservoir pressure. That is, the benefits of having stable nanobubbles or microbubbles at the surface is still gained although in the reservoir the bubbles will tend to and can become supercritical fluid.

[0029] Storage of the nanobubble-bearing first liquid and / or waste slurry can be in appropriate tank or vessel 24. Storage can occur under a low pressure, for example, in the range from 2 to 6 atmospheres (29 to 88 psi). This relatively low pressure is designed to maintain the nanobubbles in nanobubble form rather than dissolving into the liquid or slurry, or escaping from the liquid or slurry.

[0038]

[0030] It is understood that the ability to inject carbon dioxide entrained in a pumpable slurry as nanobubbles, for example, creates benefits and feasibilities not available when simply pumping carbon dioxide larger bubbles (macrobubbles), which will separate from the slurry or liquid easily and before injection.

[0039]

[0031] Persons of skill in the art will recognize changes, additions and deletions of particular steps of the process that can be made depending on the circumstances of the wastes, slurry preparation, injection operations, etc. The methods presented in the claims are explicitly disclosed in this application. Steps can be repeated, as those of skill in the art will understand. Steps can be rearranged, as those of skill in the art will understand.

[0040]

[0032] The present disclosure may be further exemplified by the following numbered examples and clauses, which provide some non-limiting embodiments:

[0041]

[0033] Example 1. A method of sequestering carbon dioxide in a target zone in a subterranean formation, comprising: creating carbon dioxide nanobubbles from a carbon dioxide source; entraining the carbon dioxide nanobubbles in an injection waste slurry, thereby creating a carbon dioxide nanobubble-bearing waste slurry; and then injecting the carbon dioxide nanobubblebearing waste slurry into the subterranean formation.

[0042]

[0034] Example 2. The method of claim 1 , wherein creating carbon dioxide nanobubbles further comprises: creating the nanobubbles in a first liquid.

[0043]

[0035] Example 3. The method of example 2, wherein the first liquid is water or a water-based liquid.

[0044]

[0036] Example 4. The method of example 1 , wherein creating the nanobubbles further comprises: hydrodynamic cavitation, ultrasonic cavitation, or membrane sparging.

[0045]

[0037] Example 5. The method of example 2, further comprising dissolving carbon dioxide in the first liquid prior to creating the nanobubbles.

[0046]

[0038] Example 6. The method of example 1, wherein creating the nanobubbles further comprises creating the nanobubbles in a waste slurry.

[0047]

[0039] Example 7. The method of example 1, wherein creating the nanobubbles or entraining the nanobubbles in the waste slurry further comprises use of a surfactant.

[0040] Example 8. The method of example 1 , further comprising storing the carbon dioxide nanobubble-bearing waste slurry at the earth’s surface at a pressure of about 2 to 6 atmospheres.

[0048]

[0041] Example 9. The method of example 1, wherein injecting the carbon dioxide nanobubble-bearing waste slurry further comprises injecting at a pressure below that necessary to cause the carbon dioxide to change to supercritical phase, and wherein a target zone pressure changes the carbon dioxide to a supercritical phase.

[0049]

[0042] Example 10. The method of example 1, further comprising fracturing the target zone using the carbon dioxide nanobubble-bearing waste slurry.

[0050]

[0043] Example 11. A method of sequestering carbon dioxide in a target zone in a subterranean formation, comprising: creating carbon dioxide microbubbles from a carbon dioxide source; entraining the carbon dioxide microbubbles in an injection waste slurry, thereby creating a carbon dioxide microbubble-bearing waste slurry; and then injecting the carbon dioxide microbubblebearing waste slurry into the subterranean formation.

[0051]

[0044] Example 12. The method of example 11, wherein creating carbon dioxide microbubbles further comprises: creating the microbubbles in a first liquid.

[0052]

[0045] Example 13. The method of example 2, wherein the first liquid is water or a water-based liquid.

[0053]

[0046] Example 14. The method of example 11, wherein creating the microbubbles further comprises: mechanical agitation, sonication, vortex mixing, or microfluidic processes.

[0054]

[0047] Example 15. The method of example 12, further comprising dissolving carbon dioxide in the first liquid prior to creating the microbubbles.

[0055]

[0048] Example 16. The method of example 11, wherein creating the microbubbles further comprises creating the microbubbles in a waste slurry.

[0049] Example 17. The method of example 1 1 , wherein creating the microbubbles or entraining the microbubbles in the waste slurry further comprises use of a surfactant.

[0056]

[0050] Example 18. The method of example 11, further comprising storing the carbon dioxide microbubble-bearing waste slurry at a pressure of about 2 to 6 atmospheres.

[0057]

[0051] Example 19. The method of example 11, wherein injecting the carbon dioxide microbubble-bearing waste slurry further comprises injecting at a pressure below that necessary to cause the carbon dioxide to change to supercritical phase.

[0058]

[0052] Example 20. The method of example 11, further comprising fracturing the target zone using the carbon dioxide microbubble-bearing waste slurry.

[0059] Conclusion

[0060]

[0053] The words or terms used herein have their plain, ordinary meaning in the field of this disclosure, except to the extent explicitly and clearly defined in this disclosure or unless the specific context otherwise requires a different meaning. If there is any conflict in the usages of a word or term in this disclosure and one or more patent(s) or other documents that may be incorporated by reference, the definitions that are consistent with this specification should be adopted.

[0061]

[0054] Whenever a numerical range of degree or measurement with a lower limit and an upper limit is disclosed, any number and any range falling within the range is also intended to be specifically disclosed. For example, every range of values (in the form “from a to b,” or “from about a to about b,” or “from about a to b,” “from approximately a to b,” and any similar expressions, where “a” and “b” represent numerical values of degree or measurement) is to be understood to set forth every number and range encompassed within the broader range of values.

[0062]

[0055] While the foregoing written description of the disclosure enables one of ordinary skill to make and use the embodiments discussed, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiments, methods, and examples herein. The disclosure should therefore not be limited by the above-described embodiments, methods, and examples. While this disclosure has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments as well as other embodiments of the disclosure will be apparent to persons skilled in the art upon reference to the description. It is, therefore, intended that the appended claims encompass any such modifications or embodiments.

[0063]

[0056] The particular embodiments disclosed above are illustrative only, as the present disclosure may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. It is, therefore, evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope of the present disclosure. The various elements or steps according to the disclosed elements or steps can be combined advantageously or practiced together in various combinations or sub-combinations of elements or sequences of steps to increase the efficiency and benefits that can be obtained from the disclosure. It will be appreciated that one or more of the above embodiments may be combined with one or more of the other embodiments, unless explicitly stated otherwise. Furthermore, no limitations are intended to the details of construction, composition, design, or steps herein shown, other than as described in the claims.

[0064]

[0057] The systems, methods, and apparatus in the embodiments described above are exemplary. Therefore, many details are neither shown nor described. Even though numerous characteristics of the embodiments of the present disclosure have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the present disclosure is illustrative, such that changes may be made in the detail, especially in matters of shape, size and arrangement of the components within the principles of the present disclosure to the full extent indicated by the broad general meaning of the terms used in the attached claims. The description and drawings of the specific examples above do not point out what an infringement of this patent would be but are to provide at least one explanation of how to make and use the present disclosure. The limits of the embodiments of the present disclosure and the bounds of the patent protection are measured by and defined in the following claims.

Claims

It is claimed:

1. A method of sequestering carbon dioxide in a target zone in a subterranean formation, comprising: creating carbon dioxide nanobubbles from a carbon dioxide source; entraining the carbon dioxide nanobubbles in an injection waste slurry, thereby creating a carbon dioxide nanobubble-bearing waste slurry; and then injecting the carbon dioxide nanobubble-bearing waste slurry into the subterranean formation.

2. The method of claim 1, wherein creating carbon dioxide nanobubbles further comprises: creating the nanobubbles in a first liquid.

3. The method of claim 2, wherein the first liquid is water or a water-based liquid.

4. The method of claim 1, wherein creating the nanobubbles further comprises: hydrodynamic cavitation, ultrasonic cavitation, or membrane sparging.

5. The method of claim 2, further comprising dissolving carbon dioxide in the first liquid prior to creating the nanobubbles.

6. The method of claim 1, wherein creating the nanobubbles further comprises creating the nanobubbles in a waste slurry.

7. The method of claim 1, wherein creating the nanobubbles or entraining the nanobubbles in the waste slurry further comprises use of a surfactant.

8. The method of claim 1, further comprising storing the carbon dioxide nanobubble-bearing waste slurry at the earth’s surface at a pressure of about 2 to 6 atmospheres.

9. The method of claim 1 , wherein injecting the carbon dioxide nanobubble-bearing waste slurry further comprises injecting at a pressure below that necessary to cause the carbon dioxide to change to supercritical phase, and wherein a target zone pressure changes the carbon dioxide to a supercritical phase.

10. The method of claim 1, further comprising fracturing the target zone using the carbon dioxide nanobubble-bearing waste slurry.

11. A method of sequestering carbon dioxide in a target zone in a subterranean formation, comprising: creating carbon dioxide microbubbles from a carbon dioxide source; entraining the carbon dioxide microbubbles in an injection waste slurry, thereby creating a carbon dioxide microb ubblc-bcaring waste slurry; and then injecting the carbon dioxide microbubble-bearing waste slurry into the subterranean formation.

12. The method of claim 11, wherein creating carbon dioxide microbubbles further comprises: creating the microbubbles in a first liquid.

13. The method of claiml 2, wherein the first liquid is water or a water-based liquid.

14. The method of claim 11 , wherein creating the microbubbles further comprises: mechanical agitation, sonication, vortex mixing, or microfluidic processes.

15. The method of claim 12, further comprising dissolving carbon dioxide in the first liquid prior to creating the microbubbles.

16. The method of claim 11 , wherein creating the microbubbles further comprises creating the microbubbles in a waste slurry.

17. The method of claim 11 , wherein creating the microbubbles or entraining the microbubbles in the waste slurry further comprises use of a surfactant.

18. The method of claim 11 , further comprising storing the carbon dioxide microbubblebearing waste slurry at a pressure of about 2 to 6 atmospheres.

19. The method of claim 11 , wherein injecting the carbon dioxide microbubble-bearing waste slurry further comprises injecting at a pressure below that necessary to cause the carbon dioxide to change to supercritical phase.

20. The method of claim 11, further comprising fracturing the target zone using the carbon dioxide microbubble-bearing waste slurry.

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