Self-degrading organogel
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-02-23
- Publication Date
- 2026-03-11
Smart Images
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Abstract
Description
[Background technology]
[0001] Overview Petroleum and its products are an integral part of modern society. To access petroleum, oil wells are drilled into the ground. During drilling operations, a fluid called drilling fluid is circulated in the borehole. Drilling fluids facilitate the drilling process by bringing rock cuttings to the surface, providing stability for the well, as well as cooling and lubricating the drill bit. Lavrov, A., Lost circulation: Mechanisms and solutions, Gulf Professional Publishing, Elsevier (2016). However, when undesirable lateral fractures are present in the rock mass, they provide an escape route for the drilling fluid, which is then lost from the formation. This situation is called lost circulation and is one of the most serious, costly and time-consuming problems of drilling operations. Lavrov; Rabia, H., Oilwell drilling engineering: Principles and practice, Graham & Trotman, London (1985).
[0002] One of the most traditional and widely used methods to mitigate fluid losses is to incorporate solid particles into drilling fluids. White, Robert J. Lost-circulation Materials and their Evaluation, Paper presented at the Drilling and Production Practice, New York, New York, January 1956. These particulates, which can be anything from paper to chalk to food waste, are carried by the fluid into fractures where they accumulate and eventually plug the fractures. However, these traditional lost circulation materials (LCMs) have limited flow blocking capabilities in large fractures. Boukadi, F., Yaghi, B., Al-Hadrami, H., Bemani, A., Babadagli, T., & De Mestre, P., "A Comparative Study of Lost Circulation Materials." Energy Sources, 26(11), 1043-1051 (2004).
[0003] In contrast to conventional approaches, one or more embodiments of the present invention may be directed to a more reliable gel-based LCM. In addition to effective flow blocking, another important feature that may be exhibited by one or more embodiments is self-degradation. Because fractures play a key role in the oil recovery process, it is highly desirable to have the LCM degrade once drilling operations are completed. It is therefore important to design a material that can effectively plug fractures and degrade after a controlled period of time. The degradation period needs to be carefully controlled because the LCM needs to be an effective plugging agent that lasts throughout the drilling of the well, but not so long that it interferes with the ability to recover oil during production.
[0004] A novel LCM was developed by converting oil-based fluids into gels. Dibenzylidene sorbitol (DBS), a food-grade compound, was found to transform oil-based fluids into gels through self-assembly. DBS was selected because it is environmentally friendly, inexpensive compared to other low molecular weight gelators, and supplied in bulk by multiple vendors. Gels formed by DBS are very robust and can effectively seal crevices. These gels are also degradable under acidic conditions. The degradation time can be controlled by the type and concentration of acid. [Prior art documents] [Non-patent literature]
[0005] [Non-Patent Document 1] Lavrov, A., Lost circulation: Mechanisms and solutions, Gulf Professional Publishing, Elsevier (2016) [Non-Patent Document 2] Lavrov; Rabia, H., Oilwell drilling engineering: Principles and practice, Graham & Trotman, London (1985) [Non-Patent Document 3] White, Robert J. Lost-circulation Materials and their Evaluation, Paper presented at the Drilling and Production Practice, New York, New York, January 1956 [Non-Patent Document 4] Boukadi, F., Yaghi, B., Al-Hadrami, H., Bemani, A., Babadagli, T., & De Mestre, P., "A Comparative Study of Lost Circulation Materials." Energy Sources, 26(11), 1043-1051 (2004) Summary of the Invention
[0006] Quick Overview The present disclosure provides an autodegradable gel composition comprising a liquid, a gelling agent, and a degradation agent, where the degradation agent degrades the gelling agent over time.
[0007] In some embodiments, the gelling agent is a low molecular weight compound.
[0008] In some embodiments, the gelling agent is dibenzylidene sorbitol (DBS), methyl dibenzylidene sorbitol (methyl-DBS), dimethyl dibenzylidene sorbitol (dimethyl-DBS), any other functional derivative of dibenzylidene sorbitol, or a combination thereof.
[0009] In some embodiments, the gelling agent is DBS.
[0010] In some embodiments, the concentration of the gelling agent is from about 0.25 wt.% to about 15 wt.%.
[0011] In some embodiments, the concentration of the gelling agent is from about 0.25 wt.% to about 5 wt.%.
[0012] In some embodiments, the concentration of the gelling agent is from about 2 wt.% to about 4 wt.%.
[0013] In some embodiments, the concentration of the gelling agent is about 0.25 wt.%.
[0014] In some embodiments, the concentration of the gelling agent is about 0.5 wt.%.
[0015] In some embodiments, the concentration of the gelling agent is about 1 wt.%.
[0016] In some embodiments, the concentration of the gelling agent is about 2 wt.%.
[0017] In some embodiments, the concentration of the gelling agent is about 3 wt.%.
[0018] In some embodiments, the concentration of the gelling agent is about 4 wt.%.
[0019] In some embodiments, the degrading agent comprises one or more acids.
[0020] In some embodiments, the one or more acids are mineral acids, organic acids, Lewis acids, or combinations thereof.
[0021] In some embodiments, the mineral acid is hydrochloric acid.
[0022] In some embodiments, the organic acid is butanoic acid, hexanoic acid, octanoic acid, decanoic acid, dodecanoic acid, citric acid, formic acid, or a combination thereof.
[0023] In some embodiments, the Lewis acid is aluminum(III) chloride or bismuth(III) triflate.
[0024] In some embodiments, the autodegradable gel composition further comprises a solvent.
[0025] In some embodiments, the solvent is dimethylsulfoxide (DMSO), dihydrolevoglucosenone (silane), dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), or a combination thereof.
[0026] In some embodiments, the solvent is DMSO.
[0027] In some embodiments, a portion of the DMSO is encapsulated within the wax particles.
[0028] In some embodiments, the liquid comprises an oil-based liquid or an aqueous liquid.
[0029] In some embodiments, the oily liquid comprises mineral oil.
[0030] In some embodiments, the liquid further comprises hexanol, an organic acid, or a combination thereof.
[0031] In some embodiments, the liquid comprises about 20 wt.% to about 80 wt.% mineral oil and about 20 wt.% to about 80 wt.% hexanol, an organic acid, or a combination thereof.
[0032] In some embodiments, the liquid comprises about 30 wt.% to about 50 wt.% mineral oil and about 30 wt.% to about 50 wt.% hexanol.
[0033] The present disclosure also provides a method of preventing fluid loss in a rock formation, comprising the steps of: injecting a fluid into a borehole in the rock formation; and Injecting a plugging material into a borehole, the plugging material including a gelling agent that gels into a gel that plugs fractures or pores in a rock formation.
[0034] In some embodiments, the loss occurs before, during, or after the drilling operation.
[0035] In some embodiments, the occlusive material is an anti-lost circulation agent.
[0036] In some embodiments, the fluid is a drilling fluid.
[0037] In some embodiments, the gelling agent gels into an autodegradable gel that degrades over time.
[0038] In some embodiments, the gelling agent gels into an autodegrading gel in the downhole portion of the borehole.
[0039] In some embodiments, the gel forms without heating.
[0040] In some embodiments, the closure of the cleft is reversible.
[0041] In some embodiments, the gel seals the cracks for about 1 day to about 16 weeks.
[0042] In some embodiments, the gel seals the cracks for about 2 weeks to about 6 weeks.
[0043] In some embodiments, the closure of the cleft is reversed by degradation of the gel.
[0044] In some embodiments, the fractures or pores contain oil, brine, or other reservoir fluids.
[0045] In some embodiments, the plugging of the fracture prevents fluid from contacting reservoir fluid.
[0046] In some embodiments, the fluid does not contact the reservoir fluid.
[0047] In some embodiments, the reservoir fluid is not contaminated by the drilling fluid.
[0048] The present disclosure also provides a method for improving recovery of reservoir fluids from a fracture or pore comprising plugging the fracture or pore with an autodegradable gel composition described herein. [Brief description of the drawings]
[0049] [Figure 1]FIG. 1 is a photographic schematic showing that a concentrated dibenzylidene sorbitol (DBS) solution in DMSO (gelling solution) is added to a base oil and mixed to obtain a DBS gel. [Diagram 2] Figure 2A is a line graph showing a stress amplitude sweep at 10 Hz in gels with different DBS concentrations, and Figure 2B is a line graph showing the dependence of elastic modulus (G') and yield stress (σy) on DBS concentration in the gels. [Diagram 3] 3A is a line graph showing the pressure profile of the flow interruption experiment described herein. The gel has a DBS concentration of 0.5 wt% and the tube has an inner diameter of 3 mm. FIG. 3B is a line graph showing the maximum pressure that the plug can withstand as a function of plug length. The gel has a DBS concentration of 0.5 wt% and the tube has an inner diameter of 3 mm. [Figure 4] FIG. 4A is a series of photographs showing that when pressure is applied, a rupture occurs at the interface and the plug moves along the thick tube (photo (i)); a step change in tube diameter causes the plug to stop moving and, when the pressure is high enough, the plug enters the thin tube (photo (ii)); and finally, the plug exits the flow loop (photo (iii)). The thick and thin tubes have inner diameters of 6.35 mm and 1.38 mm, respectively. FIG. 4B is a line graph showing the characteristic pressure profile of the flow interruption experiment described herein with a step change in tube diameter. The thick and thin tubes have inner diameters of 6.35 mm and 1.38 mm, respectively. [Diagram 5] Schematic showing the degradation of DBS gel upon contact with aqueous hydrochloric acid over a period of four days. After four days, free oil and remaining gel are visible. [Figure 6] FIG. 1 is a schematic diagram showing the synthesis of a self-degrading emulsion gel, in which an aqueous phase is dispersed in an oil phase, which is then gelled using DBS; due to the presence of acid in the aqueous phase, the DBS is gradually hydrolyzed and the gel is eventually degraded. [Figure 7]This is a set of two photographs showing the degradation of a clear DBS gel over several days due to the presence of organic acids (butanoic, hexanoic, or octanoic acids). The gels were made using mineral oil containing 20 wt.% of the organic acid. The DBS concentration in the gels was 0.5 wt.% and the experiment was performed at 65°C. [Figure 8] Figure 8A is a schematic diagram showing how DBS gel is chemically degraded, eventually resulting in a dilute solution. Figure 8B is a line graph showing the decrease in elastic modulus (G') over time as the DBS gel is degraded. The gel contained 0.5 wt% DBS and 20 wt.% hexanoic acid. The experiment was performed at 65°C. [Figure 9] 1 is a line graph showing the decrease in elastic modulus (G') over time as DBS gel is degraded in the presence of C-8, C-10, C-6, or C-12 fatty acids. [Figure 10] 1 is a set of three photographs showing the degradation of DBS gel by contacting the gel with DMSO, including encapsulation of DMSO in wax capsules. [Figure 11] A schematic diagram (top) showing the degradation of DBS gel whose surface has been dusted with bismuth(III) triflate (BiTf), and a set of photographs showing the difference between DBS gels that have not been treated with BiTf (bottom left) and DBS gels that have been treated with BiTf (bottom right) after 12 hours. [Figure 12] A schematic diagram (top) showing the decomposition of DBS gel with aluminum(III) chloride (AlCl3) dispersed therein and a set of photographs showing the decomposition of DBS gel with AlCl3 dispersed therein over a period of 6 days at a temperature of 70°C. [Figure 13] Scatter plots showing G' as a function of stress amplitude for gels with DBS concentrations of 0.25 wt.%, 0.5 wt.%, 1 wt.%, 2 wt.%, or 5 wt.% (A) and G' and σy as a function of DBS wt.% (B). [Figure 14]A series of scatter plots showing a stress sweep test (left), a step stress test (center), and multiple cycles of a step stress test (right) for a 1 wt.% DBS gel in hexanol, all measured at a constant frequency of 10 Hz. [Figure 15] FIG. 1 is a scatter plot showing the mass percent of DBS gel that remains unchanged after addition of 0.3 M, 0.4 M, 0.5 M, or 1 M aqueous hydrochloric acid (HCl) over time. [Figure 16] Schematic diagram showing the degradation of DBS gel over time (top) and scatter plot showing G' as a function of time for DBS gels with added 0.2 M, 0.5 M, or 1 M HCl. [Figure 17] A set of chemical structures showing the decomposition of DBS in acid to form benzaldehyde and sorbitol (top) and a set of photographs showing the decomposition of pure DBS over time in 2 M HCl (bottom). [Figure 18] A set of line graphs showing the infrared spectrum (left) of the upper oil layer of DBS decomposed by HCl and the 1H nuclear magnetic resonance (NMR) spectrum (right) of the upper oil layer of DBS decomposed by HCl. [Figure 19] FIG. 1 is a schematic diagram (top) showing how a lost circulation agent, such as the autodegrading gel described herein, can be used to plug fractures in a borehole, and a set of photographs (bottom) showing how the autodegrading DBS gel (bottom layer in left photo) can stop the flow of mineral oil (top layer in left photo) for approximately 12 hours. [Figure 20] 1 is a line graph showing the viscosity of DBS gel as a function of shear rate at 20° C. [Figure 21] 1 is a line graph showing the viscosity of DBS gel as a function of shear rate at 40° C. [Figure 22] 1 is a line graph showing the viscosity of DBS gel as a function of shear rate at 70° C. [Diagram 23] 1 is a line graph showing the storage modulus of DBS gels as a function of the concentration of DBS in the gel. [Figure 24]1 is a line graph showing the storage modulus of DBS gels as a function of the concentration of octanoic acid in the gel. [Diagram 25] 1 is a line graph showing the storage modulus of DBS gel as a function of mud contaminant concentration. [Figure 26] 1 is a line graph showing the decrease in storage modulus of DBS gel upon failure and subsequent recovery over time, repeated over several cycles. [Figure 27] 1 is a line graph showing the viscosity of DBS gel as a function of shear rate. [Figure 28] 1 is a line graph showing the viscosity as a function of time of DBS gels formed at different shear rates. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0050] Detailed Description definition Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. In case of conflict, the present application, including definitions, will control. Unless otherwise required by context, singular terms shall include the plural and plural terms shall include the singular.
[0051] The documents listed and / or referenced in this disclosure are incorporated herein by reference in their respective entireties, except for any statements that contradict the express disclosure herein, except for any disclaimers or disclaimers of subject matter, and except to the extent the incorporated material contradicts the express disclosure herein, in which case the language in the present disclosure will control.
[0052] The incorporation by reference of such documents shall not be deemed an admission that the incorporated material is prior art to the present disclosure or is believed to be material to the patentability of the present disclosure.
[0053] Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure, suitable methods and materials are described below. The materials, methods, and examples are illustrative only and are not intended to be limiting. Other features and advantages of the present disclosure will be apparent from the detailed description and claims.
[0054] In order to further define this disclosure, the following terms and definitions are provided.
[0055] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. The term "a" (or "an"), as well as the terms "one or more" and "at least one," can be used interchangeably herein. In certain aspects, the term "a" or "an" means "single." In other aspects, the term "a" or "an" includes "two or more" or "multiple."
[0056] The term "about" is used herein to mean approximately, roughly, approximately, or approximately. When the term "about" is used in conjunction with a numerical range, it modifies that range by extending the boundaries above and below the numerical values specified. In general, the term "about" is used herein to modify numerical values above and below the stated value by a variance of 10 percent above or below (higher or lower).
[0057] As used herein, the term "base oil" refers to the liquid to which the gelling solution is added to produce a gel. In addition to the above-mentioned base oils, any liquid containing oil ("oily liquid") may be used, including oily liquids containing different amounts of mineral oil and co-solvents such as hexanol. Any liquid containing water ("aqueous liquid") may be used.
[0058] As used herein, the term "gelling agent" refers to any compound that forms a gel when exposed to a stimulus, including, but not limited to, the addition of a solvent or liquid, such as an oily liquid, an increase or decrease in temperature, or an increase or decrease in pressure.
[0059] As used herein, the term "gel" refers to a semi-solid substance containing cross-linked materials. In some embodiments, the cross-links are covalent bonds. In some embodiments, the cross-links are hydrogen bonds. In some embodiments, the cross-links are intermolecular forces.
[0060] As used herein, the term "gelling solution" refers to a solution that includes a gelling agent.
[0061] As used herein, the term "mineral oil" refers to any mixture of higher alkanes from a mineral source, such as petroleum distillates including diesel, or similar synthetically derived mixtures such as synthetic olefins (PAOs).
[0062] As used herein, the term "fluid" refers to any liquid whose flow can be retarded or prevented by a plugging material. As used herein, the term "plugging material" refers to any material that can be used to retard or prevent the flow of a fluid. In some embodiments, the fluid is water. In some embodiments, the fluid is a drilling fluid. In some embodiments, the plugging material is a self-degrading gel as described herein. In some embodiments, the plugging material is used to retard or prevent the flow of fluids from a borehole, e.g., a hole formed in a rock formation by drilling.
[0063] As used herein, the term "disintegration agent" refers to any agent that, when added to a gel, causes the gel to disintegrate into a liquid solution. In some embodiments, the disintegration agent is an aqueous acid. In some embodiments, the disintegration agent is a Lewis acid. In some embodiments, the disintegration agent is a solvent. EXAMPLES
[0064] Results and Discussion of the Examples Gel preparation without heating: Typically, the preparation of low molecular weight gels requires heating to very high temperatures. However, heating the solvent requires high energy input and may be impractical for large-scale industrial applications. Therefore, a method was utilized to synthesize DBS gels without heating. In some embodiments, a high concentration of DBS (e.g., 15 wt.%) is dissolved in dimethyl sulfoxide (DMSO) to generate a gelling solution. A predetermined amount of this gelling solution is then added to a base oil containing mineral oil and a co-solvent (hexanol). The mixture is then gently stirred, and gelation occurs in less than one minute. The synthesis method is shown in Figure 1. The co-solvent increases the solvent compatibility and promotes the formation of a homogenous gel. A base oil composition of 80 wt.% mineral oil and 20 wt.% hexanol was selected. Gels formed by the conventional heating and non-heating methods were then compared using dynamic rheology. The results showed no significant difference in elastic modulus (G') for both gels. Similar methods can be used to synthesize gels of other low molecular weight gelators or other DBS derivatives (e.g., methyl-DBS or dimethyl-DBS). Other gelators besides DBS may also be used.
[0065] Figure 1 shows how to synthesize DBS gel without heating. A concentrated DBS solution in DMSO (gelling solution) is added to the base oil. Upon mixing, a robust DBS gel is obtained.
[0066] Effect of DBS concentration: The viscoelastic properties of DBS gels were studied. The elastic modulus (G') and viscous modulus (G'') were measured as a function of gallant concentration. Fully developed gels were obtained at DBS concentrations as low as 0.25 wt.%. Gels were identified using oscillatory shear rheology. In gels, G' is typically higher than G'' and G' is typically independent across the frequency range. These gel characteristics were exhibited by all samples containing DBS concentrations of 0.25 wt.% and above. Increasing DBS concentration increases the strength of the gel as indicated by the increasing value of G' (Figure 2A). Figure 2B shows the dependence of G' on gelator concentration, which is followed by a power law dependence with exponent n = 2. The increase in gel strength with increasing DBS concentration was also observed by examining the storage modulus in the linear viscoelastic (LVE) region, as shown in Figure 23. The strength of the gel can also be modified by adjusting the concentration of organic acids present, as shown in Figure 24. These gels are organized by weak intermolecular interactions, therefore the gels exhibit thixotropic behavior. Upon application of high stress amplitudes (higher than the yield stress), the gels behave like liquids. Figure 2A shows that at low applied stresses, G' is constant. Above the yield stress value, a sharp drop in G' is observed. Figure 2B shows that the yield stress increases with increasing gallant concentration. There is also a power law dependence between the yield stress and gelator concentration, with the power exponent n = 1.3.
[0067] Figure 2 shows the dependence of the viscoelastic properties of the gels on DBS concentration. (A) Stress amplitude sweep at 10 Hz in gels with different DBS concentrations. (B) Dependence of elastic modulus (G') and yield stress (σy) on DBS concentration in the gels.
[0068] DBS gels also exhibit shear thinning and thixotropy; that is, the nanofibrillar network of DBS is held together by weak bonds that can be broken by shear. This causes the sample to liquefy under shear and the viscosity decreases with increasing shear rate. When shear is stopped, the network quickly recovers and the gel regains its elastic (solid) characteristics. These aspects are illustrated by Figure 14, which shows data for a 1% DBS gel in hexanol.
[0069] Figure 14(A) (left) shows plots of the elastic modulus G' and viscous modulus G'' as a function of stress amplitude. At low stresses, G' ~ 40,000 Pa remains constant, indicating that the DBS network is unchanged. However, the yield stress σ y Above a pressure of about 200 Pa, G' decreases rapidly, indicating that the network is broken, i.e., the sample is transformed into a liquid.
[0070] Figure 14(B) (center) shows the results of a step stress test on the above sample. At low stress (10 Pa), the gel remains unchanged (G'>G''). At a second step, at 300 Pa (>σ y ), which breaks the network and the rheology becomes liquid-like (G''>G'). In a final step, the stress is returned to 10 Pa and the gel state is rapidly regained (in <20 s). The rapid recovery of the DBS network is also seen upon repeated cycles of the step stress test (Figure 14(C)(right)). Even after 10 such cycles, the gel modulus G' remained virtually unchanged.
[0071] The rheology of DBS gels as a function of DBS concentration was also studied. As DBS increased, the elastic modulus of the gel, G', and the yield stress of the gel, σ y Both G' and σ increase steadily. y The log-log plot of both quantities follows the polymer law (Figure 13 (bottom)) and G' ~ c 2 and σ y ~ c1.3 This shows that.
[0072] The gel also maintains its strength over a wide range of temperatures, for example, from about 10° C. to about 90° C. or from about 20° C. to about 70° C. As shown in Figures 20-22, at 20° C., 40° C., and 70° C., the DBS gel decreases in viscosity as the shear rate increases, but quickly recovers when the shear rate is reduced back to normal, demonstrating its strength over a wide range of temperatures.
[0073] Gels may also exhibit self-healing properties. As used herein, the term "self-healing" refers to the ability of a gel that has lost its initial strength (e.g., as measured by viscosity) to spontaneously regain its initial strength (or a significant proportion thereof). DBS Gel exhibits self-healing properties, as shown in FIG. 26, where the DBS Gel breaks down and reforms many times.
[0074] It was also found that the shear rate during gel formation affects the viscosity of the gel: As shown in Figure 28, gels formed at low shear rates are much more viscous than gels formed at high rates.
[0075] Gel Occlusion Ability: To gain a better understanding of the gel's occlusion ability, occlusion experiments were performed. A smooth plastic tube was occluded with 0.5 wt.% DBS gel. Water was then pumped and the pressure required to break the plug and resume flow was measured. A characteristic pressure profile is shown in Figure 3A. The rupture of the plug occurs at the interface between the gel and the smooth plastic tube. The gel plug does not deform but moves along the length of the pipe due to the water pressure. The length of the plug was varied and it was observed that the rupture pressure increased with increasing plug length (Figure 3B).
[0076] Figure 3 shows the plugging of a smooth plastic tube with DBS gel. (A) shows the characteristic pressure profile of a flow interruption experiment. (B) shows a plot of the maximum pressure that the plug can withstand as a function of plug length. The gel has a DBS concentration of 0.5 wt.% and the tube has an inner diameter of 3 mm.
[0077] To mimic a fracture in a rock formation with a non-constant diameter, plastic pipes with two different diameters were connected (Figure 4A). A plug was placed in the larger diameter tube and water was pumped through it. As before, fracture occurred at the interface. When the plug reached the mouth of the thinner tube, it stopped and the pressure continued to build up. Eventually, the gel deformed and entered the thinner tube. The gel then assumed a cylindrical shape with a diameter equal to the inner diameter of the thinner tube. The gel then traveled along the tube and exited the tube as a cylindrical plug. A characteristic pressure profile of this flow experiment is shown in Figure 4B. The pressure required to deform the gel will be much higher than the pressure that would cause an interfacial fracture between the gel and the smooth tube.
[0078] Figure 4 shows a flow interruption experiment with a step change in tube diameter. (A) (i) When pressure is applied, a fracture occurs at the interface and the plug moves along the thick tube. (ii) There is a step change in the tube diameter and the plug stops moving. When the pressure is high enough, the plug enters the thin tube. (iii) Eventually, the plug exits the flow loop. (B) shows the characteristic pressure profile of a flow interruption experiment with a step change in tube diameter. The thick and thin tubes have inner diameters of 6.35 mm and 1.38 mm, respectively.
[0079] In some embodiments, the gel can plug cracks or pores in the rock formation. In some embodiments, the plugging is reversible. In some embodiments, the plugging is reversed by dissolution of the gel after a period of time. The length of time it takes for the plugging to be reversed by dissolution can be controlled by varying various aspects of the gel, including but not limited to the gelling agent, the disintegration agent, or the concentration of the gelling agent and / or disintegration agent. The disintegration of the gel can occur by various methods described herein.
[0080] In some embodiments, the gel fills the cracks or pores for about 1 day to about 4 weeks. In some embodiments, the gel fills the cracks or pores for about 2 weeks to about 6 weeks. In some embodiments, the gel fills the cracks or pores for about 1 day to about 2 days, about 1 day to about 3 days, about 1 day to about 4 days, about 1 day to about 5 days, about 1 day to about 6 days, about 1 day to about 1 week, about 1 day to about 2 weeks, about 1 day to about 3 weeks, about 2 days to about 3 days, about 2 days to about 3 days, about 2 days to about 4 days, about 2 days to about 5 days, about 2 days to about 6 days, about 2 days to about 1 week, about 2 days to about 2 weeks, about 2 days to about 3 weeks, about 2 days to about 4 weeks, about 3 days to about 4 days, about 3 days to about 5 days, about 3 days to about 6 days, about 3 days to about 1 week, about 3 days to about 2 weeks, about 3 days for about 3 weeks, about 3 days to about 4 weeks, about 4 days to about 5 days, about 4 days to about 6 days, about 4 days to about 1 week, about 4 days to about 2 weeks, about 4 days to about 3 weeks, about 4 days to about 4 weeks, about 5 days to about 6 days, about 5 days to about 1 week, about 5 days to about 2 weeks, about 5 days to about 3 weeks, about 5 days to about 4 weeks, about 6 days to about 1 week, about 6 days to about 2 weeks, about 6 days to about 3 weeks, about 6 days to about 4 weeks, about 1 week to about 2 weeks, about 1 week to about 3 weeks, about 1 week to about 4 weeks, about 2 weeks to about 3 weeks, about 2 weeks to about 4 weeks, or about 3 weeks to about 4 weeks. In some embodiments, the gel fills the cracks or pores for about 2 weeks to about 5 weeks, about 2 weeks to about 6 weeks, about 2 weeks to about 7 weeks, about 2 weeks to about 8 weeks, about 2 weeks to about 9 weeks, about 2 weeks to about 10 weeks, about 2 weeks to about 11 weeks, about 2 weeks to about 12 weeks, about 2 weeks to about 13 weeks, about 2 weeks to about 14 weeks, about 2 weeks to about 15 weeks, about 2 weeks to about 16 weeks, about 3 weeks to about 5 weeks, about 3 weeks to about 6 weeks, about 3 weeks to about 7 weeks, about 3 weeks to about 8 weeks, about 3 weeks to about 9 weeks, about 3 weeks to about 10 weeks, about 3 weeks to about 11 weeks, about 3 weeks to about 12 weeks, about 3 weeks to about 13 weeks, about 3 ... about 14 weeks, about 3 weeks to about 15 weeks, about 3 weeks to about 16 weeks, about 4 weeks to about 5 weeks, about 4 weeks to about 6 weeks, about 4 weeks to about 7 weeks, about 4 weeks to about 8 weeks, about 4 weeks to about 9 weeks, about 4 weeks to about 10 weeks, about 4 weeks to about 11 weeks, about 4 weeks to about 12 weeks, about 4 weeks to about 13 weeks, about 4 weeks to about 14 weeks, about 4 weeks to about 15 weeks, about 4 weeks to about 16 weeks, about 5 weeks to about 6 weeks, about 5 weeks to about 7 weeks, about 5 weeks to about 8 weeks, about 5 weeks to about 9 weeks, about 5 weeks to about 10 weeks, about 5 weeks to about 11 weeks, about 5 weeks to about 12 weeks, about 5 weeks to about 13 weeks, about 5 weeks to about 14 weeks,About 5 weeks to about 15 weeks, about 5 weeks to about 16 weeks, about 6 weeks to about 7 weeks, about 6 weeks to about 8 weeks, about 6 weeks to about 9 weeks, about 6 weeks to about 10 weeks, about 6 weeks to about 11 weeks, about 6 weeks to about 12 weeks, about 6 weeks to about 13 weeks, about 6 weeks to about 14 weeks, about 6 weeks to about 15 weeks, about 6 weeks to about 16 weeks, about 7 weeks to about 8 weeks, about 7 weeks to about 9 weeks, about 7 weeks to about 10 weeks, about 7 weeks to about 11 weeks, about 7 weeks to about 12 weeks, about 7 weeks to about 13 weeks, about 7 weeks to about 14 weeks, about 7 weeks to about 15 weeks, about 7 weeks to about 16 weeks, about 8 weeks to about 9 weeks, about 8 weeks to about 10 weeks, about 8 weeks to about 11 weeks, about 8 weeks to about 12 weeks, about 8 weeks to about 13 weeks, about 8 weeks to about 14 weeks, about 8 weeks to about 15 weeks, about 8 weeks to about 16 weeks, about 9 weeks to about 10 weeks , about 9 weeks to about 11 weeks, about 9 weeks to about 12 weeks, about 9 weeks to about 13 weeks, about 9 weeks to about 14 weeks, about 9 weeks to about 15 weeks, about 9 weeks to about 16 weeks, about 10 weeks to about 11 weeks, about 10 weeks to about 12 weeks, about 10 weeks to about 13 weeks, about 10 weeks to about 14 weeks, about 10 weeks to about 15 weeks, about 10 weeks to about 16 weeks, about 11 weeks to about 12 weeks, about 11 weeks to about 13 weeks , about 11 weeks to about 14 weeks, about 11 weeks to about 15 weeks, about 11 weeks to about 16 weeks, about 12 weeks to about 13 weeks, about 12 weeks to about 14 weeks, about 12 weeks to about 15 weeks, about 12 weeks to about 16 weeks, about 13 weeks to about 14 weeks, about 13 weeks to about 15 weeks, about 13 weeks to about 16 weeks, about 14 weeks to about 15 weeks, about 14 weeks to about 16 weeks, or about 15 weeks to about 16 weeks.
[0081] In some embodiments, the gel seals the cracks or pores for about 1 day. In some embodiments, the gel seals the cracks or pores for about 2 days, about 3 days, about 4 days, about 5 days, about 9 days, about 1 week, about 2 weeks, about 3 weeks, or about 4 weeks. In some embodiments, the gel seals the cracks or pores for about 5 weeks, about 6 weeks, about 7 weeks, about 8 weeks, about 9 weeks, about 10 weeks, about 11 weeks, about 12 weeks, about 13 weeks, about 14 weeks, about 15 weeks, or about 16 weeks.
[0082] Self-degrading gel: Since DBS gel is formed by weak intermolecular forces, the gel can be degraded by solvents that can dissolve DBS. DBS gel degrades when it comes into contact with DMSO, which is a good solvent for DBS. DBS partitions out of the gel into the DMSO, and eventually the gel is physically degraded. In other embodiments, the gel is chemically degraded. DBS gel has also been found to degrade in the presence of acid. FIG. 5 shows that when an aqueous hydrochloric acid (HCl) solution is contacted with DBS gel, the gel begins to degrade and is completely degraded over a period of several days. DBS contains two acetal groups, which react with acid to produce aldehydes. Thus, without wishing to be bound by theory, it is hypothesized that in the presence of acid, DBS is chemically hydrolyzed to benzaldehyde and sorbitol according to the following reaction scheme: TIFF2025508464000001.tif27143
[0083] Hydrolysis of DBS converts the gel into a dilute solution, since the degradation products, benzaldehyde and sorbitol, do not exhibit self-organization. Tollens tests were performed on the samples before and after acid digestion. The results showed that aldehydes were produced upon decomposition, supporting the above hypothesis.
[0084] Figure 5 shows the degradation of DBS gel in the presence of aqueous acid. When DBS gel is contacted with aqueous HCl, the gel begins to degrade and eventually degrades completely over the course of several days. After 4 days, free oil and remaining gel are visible.
[0085] Since acid degradation is a relatively slow process, it is possible to synthesize gels with acid already present in the gel. The obtained gels are stable for several days due to gradual degradation, but eventually decompose into a dilute solution. To produce autodegradable gels, water-in-oil emulsions were created. A mineral oil-hexanol mixture was used for the oil phase, and hydrochloric acid (HCl) of the desired concentration was used for the aqueous phase. The gelling solution was then quickly added to form the emulsion gel. This process is shown diagrammatically in Figure 6. These emulsion gels exhibited autodegradable behavior with the decomposition time dependent on the concentration of acid.
[0086] Figure 6 shows a schematic of the synthesis of the self-degrading emulsion gel. The aqueous phase is dispersed in the oil phase, which is then gelled using DBS. Due to the presence of acid, the DBS is gradually hydrolyzed and the gel is eventually degraded.
[0087] The degradation time of the autodegradable emulsion gels was observed to decrease with increasing concentration of acid. It was also found that weak acids, such as formic acid, take longer to degrade compared to emulsion gels containing the same concentration of HCl. In the example, the concentration of hydronium ions determines the degradation time. Weak acids dissociate incompletely, so a higher concentration of acid is required to achieve similar degradation times as gels containing strong acids. Thus, the degradation time of these autodegradable emulsion gels can be controlled by the type and concentration of acid used. In some embodiments, one or more acids are used to degrade the gel, for example, one or more, two or more, three or more, or four or more acids.
[0088] In some embodiments, the gel degrades over a period of about 1 day to about 4 weeks. In some embodiments, the gel degrades over a period of about 2 weeks to about 6 weeks. In some embodiments, the gel degrades over a period of about 1 day to about 2 days, about 1 day to about 3 days, about 1 day to about 4 days, about 1 day to about 5 days, about 1 day to about 6 days, about 1 day to about 1 week, about 1 day to about 2 weeks, about 1 day to about 3 weeks, about 2 days to about 3 days, about 2 days to about 3 days, about 2 days to about 4 days, about 2 days to about 5 days, about 2 days to about 6 days, about 2 days to about 1 week, about 2 days to about 2 weeks, about 2 days to about 3 weeks, about 2 days to about 4 weeks, about 3 days to about 4 days, about 3 days to about 5 days, about 3 days to about 6 days, about 3 days to about 1 week, about 3 days to about 2 weeks, about 3 days to about 3 weeks, about 3 days decomposition over a period of about 4 weeks, about 4 days to about 5 days, about 4 days to about 6 days, about 4 days to about 1 week, about 4 days to about 2 weeks, about 4 days to about 3 weeks, about 4 days to about 4 weeks, about 5 days to about 6 days, about 5 days to about 1 week, about 5 days to about 2 weeks, about 5 days to about 3 weeks, about 5 days to about 4 weeks, about 6 days to about 1 week, about 6 days to about 2 weeks, about 6 days to about 3 weeks, about 6 days to about 4 weeks, about 1 week to about 2 weeks, about 1 week to about 3 weeks, about 1 week to about 4 weeks, about 2 weeks to about 3 weeks, about 2 weeks to about 4 weeks, or about 3 weeks to about 4 weeks. In some embodiments, the gel is administered for about 2 weeks to about 5 weeks, about 2 weeks to about 6 weeks, about 2 weeks to about 7 weeks, about 2 weeks to about 8 weeks, about 2 weeks to about 9 weeks, about 2 weeks to about 10 weeks, about 2 weeks to about 11 weeks, about 2 weeks to about 12 weeks, about 2 weeks to about 13 weeks, about 2 weeks to about 14 weeks, about 2 weeks to about 15 weeks, about 2 weeks to about 16 weeks, about 3 weeks to about 5 weeks, about 3 weeks to about 6 weeks, about 3 weeks to about 7 weeks, about 3 weeks to about 8 weeks, about 3 weeks to about 9 weeks, about 3 weeks to about 10 weeks, about 3 weeks to about 11 weeks, about 3 weeks to about 12 weeks, about 3 weeks to about 13 weeks, about 3 weeks to about 14 weeks between about 3 weeks and about 15 weeks, between about 3 weeks and about 16 weeks, between about 4 weeks and about 5 weeks, between about 4 weeks and about 6 weeks, between about 4 weeks and about 7 weeks, between about 4 weeks and about 8 weeks, between about 4 weeks and about 9 weeks, between about 4 weeks and about 10 weeks, between about 4 weeks and about 11 weeks, between about 4 weeks and about 12 weeks, between about 4 weeks and about 13 weeks, between about 4 weeks and about 14 weeks, between about 4 weeks and about 15 weeks, between about 4 weeks and about 16 weeks, between about 5 weeks and about 6 weeks, between about 5 weeks and about 7 weeks, between about 5 weeks and about 8 weeks, between about 5 weeks and about 9 weeks, between about 5 weeks and about 10 weeks, between about 5 weeks and about 11 weeks, between about 5 weeks and about 12 weeks, between about 5 weeks and about 13 weeks, between about 5 weeks and about 14 weeks,About 5 weeks to about 15 weeks, about 5 weeks to about 16 weeks, about 6 weeks to about 7 weeks, about 6 weeks to about 8 weeks, about 6 weeks to about 9 weeks, about 6 weeks to about 10 weeks, about 6 weeks to about 11 weeks, about 6 weeks to about 12 weeks, about 6 weeks to about 13 weeks, about 6 weeks to about 14 weeks, about 6 weeks to about 15 weeks, about 6 weeks to about 16 weeks, about 7 weeks to about 8 weeks, about 7 weeks to about 9 weeks, about 7 weeks to about 10 weeks, about 7 weeks ~about 11 weeks, about 7 weeks to about 12 weeks, about 7 weeks to about 13 weeks, about 7 weeks to about 14 weeks, about 7 weeks to about 15 weeks, about 7 weeks to about 16 weeks, about 8 weeks to about 9 weeks, about 8 weeks to about 10 weeks, about 8 weeks to about 11 weeks, about 8 weeks to about 12 weeks, about 8 weeks to about 13 weeks, about 8 weeks to about 14 weeks, about 8 weeks to about 15 weeks, about 8 weeks to about 16 weeks, about 9 weeks to about 10 weeks, about 9 weeks ~about 11 weeks, about 9 weeks to about 12 weeks, about 9 weeks to about 13 weeks, about 9 weeks to about 14 weeks, about 9 weeks to about 15 weeks, about 9 weeks to about 16 weeks, about 10 weeks to about 11 weeks, about 10 weeks to about 12 weeks, about 10 weeks to about 13 weeks, about 10 weeks to about 14 weeks, about 10 weeks to about 15 weeks, about 10 weeks to about 16 weeks, about 11 weeks to about 12 weeks, about 11 weeks to about 13 weeks, about 11 weeks to decomposed over a period of about 14 weeks, about 11 weeks to about 15 weeks, about 11 weeks to about 16 weeks, about 12 weeks to about 13 weeks, about 12 weeks to about 14 weeks, about 12 weeks to about 15 weeks, about 12 weeks to about 16 weeks, about 13 weeks to about 14 weeks, about 13 weeks to about 15 weeks, about 13 weeks to about 16 weeks, about 14 weeks to about 15 weeks, about 14 weeks to about 16 weeks, or about 15 weeks to about 16 weeks.
[0089] In some embodiments, the gel degrades over a period of about 1 day. In some embodiments, the gel degrades over a period of about 2 days, about 3 days, about 4 days, about 5 days, about 9 days, about 1 week, about 2 weeks, about 3 weeks, or about 4 weeks. In some embodiments, the gel degrades over a period of about 5 weeks, about 6 weeks, about 7 weeks, about 8 weeks, about 9 weeks, about 10 weeks, about 11 weeks, about 12 weeks, about 13 weeks, about 14 weeks, about 15 weeks, or about 16 weeks.
[0090] The degradation time can be easily adjusted by various parameters, including but not limited to acid content and temperature. The higher the acid concentration and temperature, the faster the degradation. As shown in Figures 15 and 16, the effect of acid content, i.e., [HCl], was studied. Gels of 2% DBS in 80 / 20 PEG / acid solution were made and the molar concentration of the acid was varied from 0.2 to 1 M. In each case, the gels were incubated at 30 °C and the mass fraction of the unchanged gel, m gel (which coexists with the sol) was measured over time. gel The curves show that m decreases to zero over several days, and that this decrease is more rapid at higher acid contents. gel The decomposition time t degr is the time for the gel to completely decompose (i.e., m gel = 0) or the time at the midpoint of the S-curve (i.e., m gel In either case, as [HCl] increases, t degr For example, when [HCl] = 0.3 M in the aqueous phase, t degr (m gel = 0) is 10 days, but when [HCl] = 1 M, t degr (m gel = 0) is only 3 days.
[0091] The rheology of the intact gel portion of the above experiment was also studied as the gel degraded. The elastic modulus G' of the intact gel was measured over time, as shown in Figure 16 (bottom). It can be seen that G' decreases exponentially with time t (to reveal the exponential nature of the decline, the data are shown as a semi-log plot of G' versus t, where the data lie on a straight line). Also, the higher the [HCl], the faster the decline in G', i.e., the steeper the slope of the semi-log plot.
[0092] To elucidate the reaction mechanism, the experiment shown in Figure 17 (bottom) was performed. 5 g of solid DBS powder was placed on top of 5 g of 2 M aqueous HCl and allowed to stand at 70 °C. Over time (approximately 48 h), all the solid disappeared, leaving two liquid phases: an upper oil phase and a lower aqueous phase. The upper phase was examined using Fourier transform infrared (FTIR) spectroscopy. A carbonyl (C=O) peak is clearly seen in the spectrum shown in Figure 18 (left). Neither DBS nor the aqueous HCl solution contain carbonyl groups, meaning that the carbonyl comes from the reaction product.
[0093] The upper phase was further investigated using nuclear magnetic resonance (NMR) spectroscopy. The NMR spectrum (Figure 18, right) identified the presence of benzaldehyde, a molecule with a carbonyl (C=O) group. This helps to clarify the reaction of DBS with acid. DBS molecules contain acetal groups (see structure in Figure 17, top left). In organic synthesis, acetals are often used as protecting groups because they are stable to strong bases and nucleophiles, but hydrolyze under acidic conditions. Without wishing to be bound by theory, it is believed that DBS is likely hydrolyzed by acid to form benzaldehyde and sorbitol, as shown in the reaction scheme in Figure 17 (top). Sorbitol does not appear in the NMR spectrum because it is hydrophilic and therefore likely partitions into the aqueous phase shown in Figure 17 (bottom right). Neither benzaldehyde nor sorbitol are able to self-assemble into nanofibrils, which explains why the gel breaks down.
[0094] Further findings revealed that DBS gels can be degraded in the absence of water. Even when pure organic acids are added to DBS gels, DBS gels degrade. The use of organic acids offers two advantages over emulsion gels. First, the gels formed are homogeneous, and second, the use of organic acids eliminates the need for co-solvents. The system is single-phase because organic acids can dissolve directly in the oil phase. This is useful because for two-phase systems, a consistent preparation method is advantageous since emulsion droplets can have a large effect on gel strength and degradation time. Furthermore, long-chain aliphatic organic acids dissolve directly in mineral oil. Organic acids can function as both degraders and co-solvents. Thus, autodegrading organogels can be easily made with fewer ingredients. As with emulsion gels, the degradation time decreases with increasing acid concentration. The type of organic acid can also affect the degradation time. Figure 7 shows that gels containing butanoic acid degrade faster than gels containing hexanoic acid, which degrade faster than gels containing octanoic acid. In this experiment the mass based concentration of each acid was the same (20 wt.%), which means that the molar concentration of the longer chain fatty acids was lower, which may be the reason for the slower decomposition rate.
[0095] Figure 7 shows a self-degradable organogel. The figure shows that a transparent DBS gel degrades over several days due to the presence of organic acids. The gel was made using mineral oil containing 20 wt.% organic acids. The DBS concentration in the gel was 0.5 wt.% and the experiment was carried out at 65 °C.
[0096] The elastic modulus G' of the autodegrading organogel was also measured as a function of time. As expected, the G' value decreased with time due to the degradation of DBS. The concept of autodegrading organogel is shown diagrammatically in Figure 8A. Depending on the type and concentration of acid, the gel's lifetime can be controlled. Figure 8B shows the decrease in G' value over one week for DBS gel containing 20 wt.% hexanoic acid. DBS gels can also be degraded in the presence of solid Lewis acids such as AlCl3. Thus, autodegrading organogels can be prepared by dispersing particles of solid acids in the gel. The synthesis of autodegrading organogels as novel lost circulation prevention agents was demonstrated by incorporation of acids. This material can be more generally referred to as a "plugging material" since it can effectively plug leaks in situations other than drilling. The same concept can also be achieved with various DBS derivatives (e.g., methyl-DBS or dimethyl-DBS).
[0097] In some embodiments, the plugging material can be used as a plugging agent in a subsurface application, hi some embodiments, the subsurface application is completion, restoration, intervention, or production.
[0098] Plugging materials may also be used to improve the recovery of reservoir fluids from fractures or pores in rock formations. Reservoir fluids may be trapped in fractures or pores when plugged by the plugging material. When the plugging material degrades, these fluids can be recovered. In contrast, if a non-reversible / non-degradable plugging material is used, it is unlikely that these fluids will be recovered.
[0099] Figure 8 illustrates the concept of an autodegrading gel. (A) In the presence of acid, DBS is chemically degraded. Eventually, the gel is converted to a dilute solution. (B) As DBS is degraded, the elastic modulus of the gel decreases. G' values are shown for gels containing 0.5 wt.% DBS and 20 wt.% hexanoic acid. The experiment was performed at 65 °C.
[0100] The degradation rate of DBS gel is a function of the type of acid, the concentration of the acid, and the temperature. Through systematic experiments, the relationship between the degradation rate and the above variables can be studied. Based on such a "formula," it becomes possible to "dial in" the degradation time. For example, to ensure that the gel degrades after 7 days at a temperature of 65°C, the formula described herein may suggest using a specific organic acid (e.g., hexanoic acid) at a specific concentration. Preliminary results show that DBS gel also degrades in the presence of aluminum chloride, a solid Lewis acid. Degradation with environmentally friendly particulate Lewis acid dispersed in the gel may also be studied. Rheological experiments may also be performed to obtain a plot of G' as a function of time. Rheological studies can also be used to correlate with flow blockage experiments. That is, DBS gels may be designed to be strong enough to block flow.
[0101] In some embodiments, the Lewis acid acts as a catalyst. As shown in Figure 11, the addition of a Lewis acid, such as bismuth (III) triflate, can promote the decomposition of DBS gel. In some embodiments, the Lewis acid is aluminum (III) chloride or bismuth (III) triflate. Other Lewis acids are known to those skilled in the art.
[0102] Moreover, a similar strategy can be used for water gelation. Low molecular weight gelators, including DBS, can form good hydrogels with cosolvents. Therefore, this approach can be extended to make self-degrading aqueous gels.
[0103] Other solvents besides or in addition to DMSO may be used to form gels, including, but not limited to, dihydrolevoglucosenone (DMSO), dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP).
[0104] The concentrations of the various components of the autodegradable gel may be varied. In some embodiments, the concentration of the gelling agent is about 2 wt.% to about 4 wt.%. In some embodiments, the concentration of the gelling agent is about 0.25 wt.% to about 15 wt.%, about 1 wt.% to about 10 wt.%, about 2 wt.% to about 8 wt.%, or about 3 wt.% to about 5 wt.%.
[0105] In some embodiments, the concentration of the gelling agent is about 2 wt.%. In some embodiments, the concentration of the gelling agent is about 0.25 wt.%, about 0.5 wt.%, about 0.75 wt.%, about 1 wt.%, about 2 wt.%, about 3 wt.%, about 4 wt.%, about 5 wt.%, about 6 wt.%, about 7 wt.%, about 8 wt.%, about 9 wt.%, about 10 wt.%, about 11 wt.%, about 12 wt.%, about 13 wt.%, about 14 wt.%, or about 15 wt.%.
[0106] In some embodiments, the concentration of mineral oil is from about 20 wt.% to about 80 wt.%, from about 30 wt.% to about 80 wt.%, from about 40 wt.% to about 80 wt.%, from about 50 wt.% to about 80 wt.%, from about 60 wt.% to about 80 wt.%, from about 70 wt.% to about 80 wt.%, from about 20 wt.% to about 70 wt.%, from about 30 wt.% to about 70 wt.%, from about 40 wt.% to about 70 wt.%, from about 50 wt.% to about 70 wt.%, from about 60 wt.% to about 70 wt.%, from about 20 wt.% to about 60 wt.%, from about 30 wt.% to about 60 wt.%, from about 40 wt.% to about 60 wt.%, from about 50 wt.% to about 60 wt.%, about 20 wt.% to about 50 wt.%, about 30 wt.% to about 50 wt.%, about 40 wt.% to about 50 wt.%, about 20 wt.% to about 40 wt.%, or about 20 wt.% to about 30 wt.%.
[0107] In some embodiments, the concentration of mineral oil is about 50 wt.%. In some embodiments, the concentration of mineral oil is about 10 wt.%, about 20 wt.%, about 30 wt.%, about 40 wt.%, about 60 wt.%, about 70 wt.%, about 80 wt.%, or about 90 wt.%.
[0108] In some embodiments, the concentration of the acid is from about 20 wt.% to about 80 wt.%, from about 30 wt.% to about 80 wt.%, from about 40 wt.% to about 80 wt.%, from about 50 wt.% to about 80 wt.%, from about 60 wt.% to about 80 wt.%, from about 70 wt.% to about 80 wt.%, from about 20 wt.% to about 70 wt.%, from about 30 wt.% to about 70 wt.%, from about 40 wt.% to about 70 wt.%, from about 50 wt.% to about 70 wt.%, from about 60 wt.% to about 70 wt.%, from about 20 wt.% to about 60 wt.%, from about 30 wt.% to about 60 wt.%, from about 40 wt.% to about 60 wt.%, from about 50 wt.% to about 60 wt.%, about 20 wt.% to about 50 wt.%, about 30 wt.% to about 50 wt.%, about 40 wt.% to about 50 wt.%, about 20 wt.% to about 40 wt.%, or about 20 wt.% to about 30 wt.%.
[0109] In some embodiments, the concentration of the acid is about 50 wt.%. In some embodiments, the concentration of the acid is about 10 wt.%, about 20 wt.%, about 30 wt.%, about 40 wt.%, about 60 wt.%, about 70 wt.%, about 80 wt.%, or about 90 wt.%.
[0110] In some embodiments, the strength of the gel can be changed by the presence of one or more additives. In some embodiments, the gel strength is increased by the presence of one or more additives. In some embodiments, the gel strength is decreased by the presence of one or more additives. In some embodiments, the additive is a solid. In some embodiments, the additive is a polymer. The polymer can be a synthetic polymer or a biopolymer. In some embodiments, the additive is a drilling mud or a component of the drilling mud. As shown in Figure 25, the presence of increasing amounts of drilling mud in the DBS gel increases the storage modulus in the LVE region, indicating an increase in gel strength.
[0111] The foregoing description of specific aspects will make fully apparent the general nature of the present disclosure, such that others, by applying knowledge within the skill of the art, may readily modify and / or adapt such specific aspects to various applications without undue experimentation and without departing from the general concept of the present disclosure.
[0112] Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed aspects, based on the teaching and guidance presented herein. As the phrases or terms in the specification should be interpreted by one of ordinary skill in the art in light of the teaching and guidance of the present disclosure, it should be understood that the phrases or terms in the specification are for the purpose of description and not for the purpose of limitation.
[0113] The breadth and scope of the present disclosure should not be limited by any of the above-described exemplary aspects, but should be defined only in accordance with the following claims and the equivalents of such claims.
Claims
1. 1. A self-degrading gel composition comprising a liquid, a gelling agent, and a degrading agent, the gelling agent is dibenzylidene sorbitol (DBS), methyl dibenzylidene sorbitol (methyl-DBS), dimethyl dibenzylidene sorbitol (dimethyl-DBS), any other functional derivative of dibenzylidene sorbitol, or a combination thereof; The self-degrading gel composition, wherein the decomposing agent comprises one or more acids at a concentration of 20 wt.% or more, and the decomposing agent decomposes the gelling agent over time.
2. 10. The self-degrading gel composition of claim 1, wherein the concentration of the gelling agent is from about 0.25 wt.% to about 15 wt.%.
3. 10. The self-degrading gel composition of claim 1, wherein the one or more acids are mineral acids, organic acids, Lewis acids, or combinations thereof.
4. 10. The self-degrading gel composition of claim 1, further comprising a solvent.
5. 5. The self-degrading gel composition of claim 4, wherein the solvent is dimethyl sulfoxide (DMSO), dihydrolevoglucosenone (silane), dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), or a combination thereof.
6. 6. The self-degrading gel composition of claim 5, wherein the solvent is DMSO, and a portion of the DMSO is encapsulated within wax particles.
7. 10. The self-degrading gel composition of claim 1, wherein the liquid comprises an oil-based liquid or an aqueous liquid.
8. 1. A method for preventing fluid loss in a rock formation, comprising: injecting a fluid into a borehole in the rock formation; and injecting a plugging material into the borehole; the occlusive material is a self-degrading gel composition; the self-degrading gel composition comprises a liquid, a gelling agent, and a degrading agent; the gelling agent is dibenzylidene sorbitol (DBS), methyl dibenzylidene sorbitol (methyl-DBS), dimethyl dibenzylidene sorbitol (dimethyl-DBS), any other functional derivative of dibenzylidene sorbitol, or a combination thereof; the decomposing agent comprises one or more acids at a concentration of 20 wt. % or more, and the decomposing agent decomposes the gelling agent over time; The plugging material fills cracks or pores in the rock formation.
9. 9. The method of claim 8, wherein the loss occurs before, during, or after the drilling operation.
10. 9. The method of claim 8, wherein the occlusive material is a lost circulation agent.
11. The method of claim 8 , wherein the fluid is a drilling fluid.
12. The method of claim 8, wherein the occlusive material is a self-degrading gel that degrades over time.
13. The method of claim 8, wherein the plugging material gels in the downhole portion of the borehole.
14. 9. The method of claim 8, wherein the concentration of the gelling agent is from about 0.25 wt.% to about 15 wt.%.
15. The method of claim 8 , wherein the plugging material further comprises a solvent.
16. The method of claim 8, wherein the liquid of the self-degrading gel composition is an oil-based liquid or an aqueous liquid.
17. The method of claim 8 , wherein the occlusive material forms a gel without heating.
18. The method of claim 8, wherein the closure of the crevice is reversible.