Composition for controlled release superhigh temperature resistant salt-tolerant gel, gel and preparation method and application thereof

Abstract

The present application relates to the field of oil and gas field development blocking agent, disclose a kind of for controlling release type superhigh temperature resistant salt gel composition, gel and its preparation method and application.The composition contains combination A, combination B, water-soluble initiator;The combination A contains water-soluble monomer, first crosslinking agent, water;The water-soluble monomer contains monomer A and monomer B with mass ratio of 1:1-3;The combination B contains oil-soluble monomer, second crosslinking agent, in-situ enhancer, emulsifier, water phase stabilizer, oil phase stabilizer, oil-soluble initiator, oil phase solvent and water phase solvent.The gel provided by the present application is significantly better than conventional blocking gel under the stability of high temperature and high salinity acidic multiple conditions superposition, and has temperature response controllable enhancement, and the blocking performance is higher after in-situ enhancement.

Description

Technical Field

[0001] This invention relates to the field of plugging agents for oil and gas field development, specifically to a composition, gel, preparation method, and application of a controlled-release, ultra-high temperature resistant, salt-resistant gel. Background Technology

[0002] During oil and gas field development, due to the strong heterogeneity of reservoirs (such as natural fractures, hydraulically fractured fractures, and high-permeability zones), injected driving fluids or produced oil and gas can easily cross-flow along high-permeability channels (i.e., "channeling channels"). Channeling of displacing fluids can cause premature gas or water breakthroughs in production wells, severely impacting oil and gas field recovery and development efficiency. Currently, particulate gel (PPG) plugging agents are widely used due to their minimal reservoir damage and strong plugging properties.

[0003] However, conventional particulate gels have several limitations under formation conditions. Firstly, they are prone to hydrolysis, degradation, or dehydration and shrinkage under the combined effects of high temperature, high salinity, and acidity. Secondly, their plugging properties are unstable due to physical bridging of particles, making them susceptible to migration under high-velocity flow near the wellbore. Ultimately, this leads to plugging failure and short-lived plugging, failing to meet the long-term effective plugging requirements of oil and gas reservoirs. Addressing the inherent contradiction between "injectability" and "plugging strength" in conventional particulate gels, re-crosslinkable pre-fabricated particulate gels (RPPGs) with "secondary crosslinking" properties have become a research hotspot. The core idea is to inject particles with low initial strength or in a swollen state, allowing them to penetrate deep into the formation. Subsequently, a secondary crosslinking reaction is triggered at the target location to form a monolithic gel block, significantly improving plugging strength.

[0004] CN112839994A discloses a re-crosslinked particulate gel for controlling CO2 consistency and preventing CO2 leakage. This prior art provides a CO2-resistant particulate gel that can be re-crosslinked under underground conditions to improve the consistency of CO2 flow and control CO2 leakage problems.

[0005] CN117467066A discloses a CO2-responsive smart gel sealant, its preparation method, and its application. In this prior art, the CO2-responsive smart gel sealant is in a liquid state before contact with CO2. Upon contact with CO2, the tertiary amine groups of the intermediate polymer are protonated and combine with the negatively charged groups in the polyanion to form ionic bonds. The molecular chains crosslink and entangle to form a three-dimensional network, ultimately forming a gel.

[0006] However, existing secondary crosslinking systems (RPPG) often have uncontrollable reaction rates, lack applicability to a wide temperature range, and are prone to early crosslinking or dilution and loss of crosslinking agents during migration. Furthermore, they are insufficient in sealing strength and prone to sealing failure under complex conditions of high temperature, high salinity, and acidity, and often cannot achieve targeted sealing of deep reservoirs.

[0007] Therefore, developing a series of novel plugging agents that can maintain high strength and long-term stability under formation conditions, especially plugging agents with broad-spectrum temperature range, salt and acid resistance, and controllable in-situ enhancement function, is of great significance for solving the problems of gas channeling and water channeling in oil and gas reservoirs. Summary of the Invention

[0008] The purpose of this invention is to provide a sealing gel that combines high strength, high stability, and the ability to achieve in-situ enhancement in response to temperature stimuli.

[0009] To achieve the above objectives, a first aspect of the present invention provides a composition for a controlled-release, ultra-high temperature resistant, salt-resistant gel, the composition comprising combination A, combination B, and a water-soluble initiator;

[0010] Based on the total weight of the combination A, the combination A contains 24-40 wt% water-soluble monomers, 0.1-1 wt% first crosslinking agent, and 59-75 wt% water;

[0011] The water-soluble monomer contains monomer A and monomer B in a mass ratio of 1:1-3;

[0012] The monomer A is selected from at least one of sodium 2-acrylamido-2-methylpropanesulfonate, divinylsulfonic acid, and sodium p-styrenesulfonate;

[0013] The monomer B is selected from at least one of acrylamide, acrylic acid, methacrylic acid, methacrylamide, and N-vinylpyrrolidone;

[0014] The first crosslinking agent is selected from at least one of N,N'-methylenebisacrylamide, 1,2-divinylbenzene, and polyethyleneimine;

[0015] Based on the total weight of the aforementioned combination B, the combination B contains 20-40 wt% oil-soluble monomer, 0.1-1 wt% second crosslinking agent, 3-8 wt% in-situ reinforcing agent, 2-10 wt% emulsifier, 0.05-0.5 wt% aqueous phase stabilizer, 0.05-0.5 wt% oil phase stabilizer, 0.3-1 wt% oil-soluble initiator, 38-74.5 wt% oil phase solvent and 0-1 wt% aqueous phase solvent;

[0016] The oil-soluble monomer is selected from at least one of methyl methacrylate, styrene, vinyl chloride, vinyl ester resin, acrylonitrile, vinyl acetate, and methyl acrylate.

[0017] A second aspect of the present invention provides a method for preparing a controlled-release, ultra-high temperature resistant, salt-resistant gel, the method comprising using the components of the composition described in the first aspect of the present invention, including:

[0018] (1) In the presence of an oil-phase solvent, an oil-soluble monomer, a second crosslinking agent, an oil-soluble initiator, an oil-phase stabilizer, and an emulsifier are first mixed to obtain mixture I; and

[0019] In the presence of an aqueous solvent, the in-situ reinforcing agent and the aqueous stabilizer are mixed a second time to obtain mixture II;

[0020] (2) The mixture I and the mixture II are subjected to emulsification and polymerization reactions in sequence to obtain a material containing an in-situ reinforcing agent;

[0021] (3) In the presence of water, the water-soluble monomer and the first crosslinking agent are mixed for the third time to obtain mixture III;

[0022] (4) The mixture III, the material containing the in-situ reinforcing agent, and the water-soluble initiator are subjected to a contact reaction and dried to obtain the controlled-release ultra-high temperature resistant and salt-resistant gel.

[0023] The third aspect of the present invention provides a controlled-release, ultra-high temperature resistant, and salt-resistant gel prepared by the method described in the second aspect.

[0024] The fourth aspect of the present invention provides the application of the controlled-release ultra-high temperature resistant and salt-resistant gel described in the third aspect in the sealing and profile control of gas and water channeling in oil and gas field development, underground storage, geothermal energy, and carbon sequestration projects.

[0025] The technical solution provided by this invention has at least the following advantages:

[0026] The controlled-release ultra-high temperature resistant and salt-resistant gel provided by this invention can release in-situ reinforcing elements under different formation temperatures, triggering a physicochemical reaction. This process can significantly improve the mechanical strength, elasticity and temperature resistance of the sealing material, transforming it from dispersed particles into a stronger blocky sealing body, thereby achieving long-term effective sealing of gas or water channeling. Attached Figure Description

[0027] Figure 1 This is a SEM image of the material containing in-situ reinforcing agent prepared in Example 1 of the present invention (after drying to constant weight);

[0028] Figure 2 This refers to the inlet and outlet pressure difference during water injection of the controlled-release ultra-high temperature resistant and salt-resistant gel prepared in Example 1 of this invention before and after in-situ reinforcement.

[0029] Figure 3 The pressure difference between the two ends of the fracture core during water injection after water channeling occurs, before and after in-situ reinforcement of the controlled-release ultra-high temperature resistant and salt-resistant gel prepared in Example 1 of this invention. Detailed Implementation

[0030] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0031] As previously stated, a first aspect of the present invention provides a composition for a controlled-release, ultra-high temperature resistant, salt-resistant gel, the composition comprising combination A, combination B, and a water-soluble initiator;

[0032] Based on the total weight of the combination A, the combination A contains 24-40 wt% water-soluble monomers, 0.1-1 wt% first crosslinking agent, and 59-75 wt% water;

[0033] The water-soluble monomer contains monomer A and monomer B in a mass ratio of 1:1-3;

[0034] The monomer A is selected from at least one of sodium 2-acrylamido-2-methylpropanesulfonate, divinylsulfonic acid, and sodium p-styrenesulfonate;

[0035] The monomer B is selected from at least one of acrylamide, acrylic acid, methacrylic acid, methacrylamide, and N-vinylpyrrolidone;

[0036] The first crosslinking agent is selected from at least one of N,N'-methylenebisacrylamide, 1,2-divinylbenzene, and polyethyleneimine;

[0037] Based on the total weight of the aforementioned combination B, the combination B contains 20-40 wt% oil-soluble monomer, 0.1-1 wt% second crosslinking agent, 3-8 wt% in-situ reinforcing agent, 2-10 wt% emulsifier, 0.05-0.5 wt% aqueous phase stabilizer, 0.05-0.5 wt% oil phase stabilizer, 0.3-1 wt% oil-soluble initiator, 38-74.5 wt% oil phase solvent and 0-1 wt% aqueous phase solvent;

[0038] The oil-soluble monomer is selected from at least one of methyl methacrylate, styrene, vinyl chloride, vinyl ester resin, acrylonitrile, vinyl acetate, and methyl acrylate.

[0039] Preferably, monomer A is sodium 2-acrylamido-2-methylpropanesulfonate and / or sodium p-styrenesulfonate; monomer B is selected from at least one of acrylic acid, N-vinylpyrrolidone, and acrylamide; and the oil-soluble monomer is selected from at least one of methyl methacrylate, vinyl chloride, and vinyl ester resin. The inventors have found that, in this preferred embodiment, the controlled-release, ultra-high temperature resistant, and salt-resistant gel prepared from this composition exhibits higher stability and strength.

[0040] Preferably, in the composition, the volume ratio of combination A to combination B is 10-25:1. The inventors have found that, under this preferred condition, the controlled-release, ultra-high temperature resistant, salt-resistant gel provided by the present invention exhibits higher stability and strength in high-temperature, high-mineralization, acidic environments.

[0041] Preferably, the mass ratio of the water-soluble initiator to combination A is 0.006-0.02:1.

[0042] In a preferred embodiment, the water-soluble initiator is selected from a combination of ammonium persulfate and sodium bisulfite, or from ammonium persulfate.

[0043] According to a particularly preferred embodiment, the water-soluble initiator is a combination of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1.

[0044] Preferably, the second crosslinking agent is selected from at least one of ethylene glycol dimethacrylate, triallyl isocyanurate, dicyclopentenyl acrylate, trimethylolpropane trimethacrylate, and 1,4-butanediol dimethacrylate.

[0045] Preferably, the in-situ reinforcing agent is selected from at least one of chromium acetate, chromium malonate, N,N-methylenebisacrylamide, polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, formaldehyde, glutaraldehyde, phenolic resin, urea-formaldehyde resin, polyethyleneimine, tetrabutyl titanate or isopropyl titanate, tetrabutyl zirconate, aluminum citrate, aluminum chloride, zirconium acetate, zirconium lactate, zirconium citrate, zirconium oxychloride, zirconium sulfate, zirconium acetylacetonate, organoboron zirconium, and organamine zirconium.

[0046] Preferably, the oil-soluble initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate.

[0047] Preferably, the aqueous phase stabilizer is selected from at least one of polyvinyl alcohol and polyethylene glycol.

[0048] Preferably, the oil phase stabilizer is selected from at least one of hexadecane, hexadecyl alcohol, and methyl isobutyl ketone.

[0049] Preferably, the emulsifier is selected from at least one of Span 80, Span 60, and Span 20.

[0050] In some embodiments, the oil phase solvent is selected from at least one of cyclohexane, isooctane, and isoamyl alcohol; the aqueous phase solvent is water.

[0051] As previously described, a second aspect of the present invention provides a method for preparing a controlled-release, ultra-high temperature resistant, salt-resistant gel, wherein the method utilizes the components of the composition described in the first aspect of the present invention, comprising:

[0052] (1) In the presence of an oil-phase solvent, an oil-soluble monomer, a second crosslinking agent, an oil-soluble initiator, an oil-phase stabilizer, and an emulsifier are first mixed to obtain mixture I; and

[0053] In the presence of an aqueous solvent, the in-situ reinforcing agent and the aqueous stabilizer are mixed a second time to obtain mixture II;

[0054] (2) The mixture I and the mixture II are subjected to emulsification and polymerization reactions in sequence to obtain a material containing an in-situ reinforcing agent;

[0055] (3) In the presence of water, the water-soluble monomer and the first crosslinking agent are mixed for the third time to obtain mixture III;

[0056] (4) The mixture III, the material containing the in-situ reinforcing agent, and the water-soluble initiator are subjected to a contact reaction and dried to obtain the controlled-release ultra-high temperature resistant and salt-resistant gel.

[0057] This invention does not impose any particular restrictions on the operation of the first mixing and the second mixing in step (1). Those skilled in the art can choose according to known techniques, as long as each component in mixture I and each component in mixture II can be mixed evenly. This invention will not be described in detail here, and those skilled in the art should not understand it as a limitation of this invention. For example, the conditions for the first mixing are: temperature 25°C, time 30 min, and rotation speed 1000 rpm; the conditions for the second mixing are: temperature 25°C, time 10 min, and rotation speed 600 rpm.

[0058] In a preferred embodiment, in step (2), the emulsification is performed using intermittent ultrasonic treatment. The conditions for intermittent ultrasonic treatment include: power of 70-90W, duration of a single ultrasonic treatment of 8-12s, interval of a single treatment of 8-12s, and total treatment time of 1.5-2.5min.

[0059] According to a preferred embodiment, in step (2), the conditions for the polymerization reaction include: a temperature of 50-70°C and a time of 2-5 hours.

[0060] Preferably, in step (4), the conditions for the contact reaction include: a temperature of 25-45°C and a time of 4-6 hours.

[0061] The present invention does not impose any particular restrictions on the conditions for the third mixing in step (3). Those skilled in the art can select the conditions based on known techniques in the art. The present invention will not elaborate further here, and those skilled in the art should not understand this as a limitation of the present invention. For example, the conditions for the third mixing are: temperature of 25°C, time of 30 min, and rotation speed of 800 rpm.

[0062] In this invention, the first mixing, the second mixing, the third mixing, the polymerization reaction, and the contact reaction are preferably carried out under stirring conditions. There are no special requirements for the specific stirring speed, and those skilled in the art can do so based on parameters known in the art.

[0063] More preferably, in step (4), the contact reaction is carried out under a nitrogen atmosphere.

[0064] Preferably, in step (4), the drying conditions include a temperature of 45-55°C and a time of 45-50 hours.

[0065] In some embodiments, the contact reaction in step (4) includes: first mixing the material containing the in-situ reinforcing agent with the mixture III, the mixing conditions including: a rotation speed of 1400-1600 rpm and a time of 12-18 min; then adding the water-soluble initiator to carry out the contact reaction.

[0066] In some embodiments, in step (4), the volume ratio of the mixture III to the material containing the in-situ reinforcing element is 10-25:1.

[0067] Preferably, the mass ratio of the water-soluble initiator to the mixture III is 0.006-0.02:1.

[0068] In some embodiments, in step (4), the method further includes: sequentially crushing and screening the dried product to obtain the controlled-release ultra-high temperature resistant salt-resistant gel.

[0069] Preferably, the controlled-release ultra-high temperature resistant and salt-resistant gel is granular with an average particle diameter of 145-155 μm; in this invention, the particle diameter of the granular controlled-release ultra-high temperature resistant and salt-resistant gel is determined by sieving.

[0070] This invention first involves emulsifying and polymerizing mixture I and mixture II to obtain the material containing the in-situ reinforcing agent. This material is then dispersed in mixture III, resulting in a controlled-release, ultra-high temperature resistant, and salt-resistant gel possessing a gel bulk network and the material containing the in-situ reinforcing agent dispersed within this network. During application, the in-situ reinforcing agent is controllably released at different formation temperatures, reacting with the gel bulk network to achieve in-situ enhancement of gel strength.

[0071] As previously stated, the third aspect of the present invention provides a controlled-release, ultra-high temperature resistant, and salt-resistant gel prepared by the method described in the second aspect.

[0072] The controlled-release ultra-high temperature resistant and salt-resistant gel provided by the present invention comprises: a bulk gel network and a temperature-responsive material containing an in-situ reinforcing element dispersed in the bulk gel network; the material can release the in-situ reinforcing element when a preset temperature is reached, and the in-situ reinforcing element can in-situ reinforce the bulk gel network.

[0073] The gel provided by this invention has the following characteristics: (a) Temperature responsiveness: It is a particulate dispersion when injected at room temperature, with good injectability; it responds to formation temperature and releases in-situ enhancing agents; (b) In-situ enhancement: Through in-situ enhancement reaction, the gel strength is significantly improved under formation conditions, overcoming the problem that conventional gels have a significantly reduced plugging rate under multiple superimposed conditions of high temperature, high salinity, and acidity; (c) Good plugging effect: The enhanced gel has high strength and good stability, and can effectively plug fractures and high permeability channels in oil and gas reservoirs.

[0074] As mentioned above, the fourth aspect of the present invention provides the application of the controlled-release ultra-high temperature resistant and salt-resistant gel described in the third aspect in the sealing and profile control of gas and water channeling in oil and gas field development, underground storage, geothermal, and carbon sequestration projects.

[0075] The present invention will be described in detail below through embodiments. Unless otherwise specified, the raw materials and equipment used in the following embodiments are commercially available products, and some of the raw materials are listed in Table 1.

[0076] Table 1

[0077]

[0078] Example 1

[0079] The controlled-release, ultra-high temperature resistant, and salt-resistant gel was prepared using the following steps:

[0080] (1) 20g of oil-soluble monomer-I, 0.5g of second crosslinking agent-I, 0.45g of oil-soluble initiator, 0.25g of oil phase stabilizer and 5g of emulsifier are first mixed in 68.25g of oil phase solvent (specifically cyclohexane) to obtain mixture I; and

[0081] 5g of in-situ enhancer and 0.05g of aqueous phase stabilizer were mixed in 0.5g of aqueous phase solvent (specifically water) to obtain mixture II;

[0082] The conditions for the first mixing were: temperature 25℃, time 30 min, and rotation speed 1000 rpm.

[0083] The conditions for the second mixing were: temperature 25°C, time 10 min, and rotation speed 600 rpm.

[0084] (2) Mix the mixture I obtained in step (1) with the mixture II, and emulsify them into a water-in-oil (W / O) emulsion by intermittent ultrasonic treatment; then carry out a polymerization reaction to obtain a material containing an in-situ reinforcing agent;

[0085] The conditions for ultrasonic treatment were as follows: the ultrasonic power was 80W, the duration of a single ultrasonic treatment was 10s, the interval between treatments was 10s, and the total treatment time was 2min.

[0086] The polymerization reaction conditions were: temperature 50℃, time 5h, and rotation speed 300rpm.

[0087] (3) Mix 10g of monomer AI, 20g of monomer BI and 0.5g of the first crosslinking agent-I in 69.5g of water to obtain mixture III;

[0088] The conditions for the third mixing step are: temperature 25℃, time 30 min, and rotation speed 800 rpm.

[0089] (4) Under a nitrogen atmosphere, the mixture III obtained in step (3) and the material containing in-situ reinforcing agent obtained in step (2) are mixed at a volume ratio of 25:1; then water-soluble initiator-I is added to carry out a contact reaction to obtain a block-shaped composite gel; the obtained composite gel is dried, crushed and screened to obtain a granular controlled-release ultra-high temperature salt resistant gel with an average particle diameter of 150 μm.

[0090] The conditions for mixing were: 1500 rpm for 15 min.

[0091] The conditions for the contact reaction were: temperature 25℃, rotation speed 200 rpm, and time 4 h.

[0092] Drying conditions: temperature 50℃, time 48h.

[0093] Examples 2-9

[0094] Examples 2 through 9 all follow the same procedure as Example 1, with the differences listed in Table 2.

[0095] Comparative Examples 1-4

[0096] Comparative Examples 1-4 were all carried out using the same procedure as Example 1, with the differences listed in Table 2.

[0097] Table 2

[0098]

[0099] Table 2 (continued)

[0100]

[0101] Test Example 1

[0102] The present invention provides, by way of example, SEM images of the material containing in-situ reinforcing agent prepared in Example 1 (after drying to constant weight), as shown below. Figure 1 As shown. By Figure 1 It can be seen that the average particle diameter of the material obtained in Example 1 of the present invention is 5 μm, and the particle size distribution is concentrated.

[0103] Test Example 2

[0104] This invention provides the controlled-release, ultra-high temperature resistant, and salt-resistant gels prepared in the above embodiments and comparative examples, showing the results of temperature response controllability enhancement, resistance under multiple superimposed conditions of high temperature, high mineralization, and acidity, as well as the in-situ enhancement response temperature range. The results are shown in Table 3. Test conditions: The controlled-release, ultra-high temperature resistant, and salt-resistant gels used in the test were all granular with a particle size of 150 μm. They were placed in an aqueous solution containing NaCl (28 wt%), CaCl2 (5 wt%), and pH=2.5 to achieve a set swelling ratio of 10:1, and tested at a specific temperature. The dehydration rate S in Table 3 was calculated using formula (I).

[0105]

[0106] In formula (I), m is the mass of the controlled-release ultra-high temperature resistant and salt-resistant gel before the tolerance test; m t This refers to the quality of the controlled-release, ultra-high temperature resistant, and salt-resistant gel after it has undergone tolerance testing.

[0107] Table 3

[0108]

[0109] Test Example 3

[0110] The controlled-release ultra-high temperature salt-resistant gel was placed in an aqueous solution containing NaCl (28wt%), CaCl2 (5wt%), and pH=2.5 to achieve a set swelling ratio of 10:1 and was then used. This was recorded as the controlled-release ultra-high temperature salt-resistant gel before in-situ reinforcement. The controlled-release ultra-high temperature salt-resistant gel before in-situ reinforcement was then subjected to in-situ reinforcement treatment at 130℃ for 48 hours to obtain the controlled-release ultra-high temperature salt-resistant gel after in-situ reinforcement.

[0111] The results of the sealing performance tests of the controlled-release ultra-high temperature resistant and salt-resistant gels prepared in the examples and comparative examples before and after in-situ reinforcement are shown in Table 4.

[0112] The steps for the blocking performance test are as follows:

[0113] (1) Inject controlled-release ultra-high temperature salt-resistant gel (before or after in-situ reinforcement) into a core with a fracture opening of 0.5 mm (70 mm in length and 2.5 mm in diameter) at a rate of 0.1 mL / min until the core fracture is filled;

[0114] (2) Starting from 0.1MPa, water is injected by constant pressure method, and the pressure is increased in a stepwise manner at a rate of 0.2MPa every 5 minutes. The water channeling breakthrough is judged based on whether the pressure drops suddenly or whether a large amount of plugging agent is suddenly produced at the outlet. The breakthrough pressure gradient during the pressurization process is recorded.

[0115] (3) After the water channeling is broken, water is injected into the sealed fracture core at a constant rate (0.5 mL / min), and the pressure difference between the inlet and outlet at both ends of the fracture core is recorded during the water injection process.

[0116] The increase factor n of the residual drag coefficient after in-situ reinforcement in Table 4 is calculated using formula (II).

[0117] In formula (II), ΔP1 is the inlet-outlet pressure difference before in-situ reinforcement, and ΔP2 is the inlet-outlet pressure difference after in-situ reinforcement.

[0118] Table 4

[0119]

[0120] The inlet and outlet pressure differences of the controlled-release, ultra-high temperature resistant, and salt-resistant gel prepared in Example 1 of this invention before and after in-situ reinforcement during water injection are as follows: Figure 2 As shown. By Figure 2 It can be seen that the controlled-release ultra-high temperature resistant and salt-resistant gel provided by the present invention has significantly improved its blocking ability after in-situ reinforcement. The breakthrough pressure gradient of the in-situ reinforced controlled-release ultra-high temperature resistant and salt-resistant gel is 1.97 times that before reinforcement.

[0121] The pressure difference between the two ends of the fracture core during water injection after in-situ reinforcement and before and after in-situ reinforcement of the controlled-release ultra-high temperature resistant and salt-resistant gel prepared in Example 1 of this invention is as follows: Figure 3 As shown. By Figure 3 It can be seen that the inlet and outlet pressure difference of the controlled-release ultra-high temperature salt-resistant gel before in-situ reinforcement was 0.12 MPa, and the inlet and outlet pressure difference of the controlled-release ultra-high temperature salt-resistant gel after in-situ reinforcement was 12.6 MPa. Since the water drive flow rate and the parameters of the fracture core model were the same, the residual resistance coefficient of the particle gel after in-situ reinforcement was increased by 104 times compared with that before in-situ reinforcement.

[0122] The results above show that the controlled-release, ultra-high temperature resistant, salt-resistant gel provided by this invention has high stability under multiple superimposed conditions of high temperature, high mineralization, and acidity, and has controllable temperature response enhancement. The in-situ enhancement further improves the plugging performance.

[0123] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a controlled-release, ultra-high temperature resistant, salt-resistant gel, characterized in that, This method uses the components of a composition for controlled-release, ultra-high temperature resistant, salt-resistant gels, including: (1) In the presence of an oil-phase solvent, an oil-soluble monomer, a second crosslinking agent, an oil-soluble initiator, an oil-phase stabilizer, and an emulsifier are first mixed to obtain mixture I; and In the presence of an aqueous solvent, the in-situ reinforcing agent and the aqueous stabilizer are mixed a second time to obtain mixture II; (2) The mixture I and the mixture II are subjected to emulsification and polymerization reactions in sequence to obtain a material containing an in-situ reinforcing agent; (3) In the presence of water, the water-soluble monomer and the first crosslinking agent are mixed for the third time to obtain mixture III; (4) The mixture III, the material containing the in-situ reinforcing agent, and the water-soluble initiator are subjected to a contact reaction and dried to obtain the controlled-release ultra-high temperature resistant and salt-resistant gel; The composition for controlled-release ultra-high temperature resistant and salt-resistant gel contains combination A, combination B, and a water-soluble initiator; based on the total weight of combination A, combination A contains 24-40 wt% water-soluble monomer, 0.1-1 wt% first crosslinking agent, and 59-75 wt% water; The water-soluble monomer contains monomer A and monomer B in a mass ratio of 1:1-3; The monomer A is selected from at least one of sodium 2-acrylamido-2-methylpropanesulfonate and sodium p-styrenesulfonate; The monomer B is selected from at least one of acrylamide, acrylic acid, methacrylic acid, methacrylamide, and N-vinylpyrrolidone; The first crosslinking agent is selected from at least one of N,N'-methylenebisacrylamide, 1,2-divinylbenzene, and polyethyleneimine; Based on the total weight of the aforementioned combination B, the combination B contains 20-40 wt% oil-soluble monomer, 0.1-1 wt% second crosslinking agent, 3-8 wt% in-situ reinforcing agent, 2-10 wt% emulsifier, 0.05-0.5 wt% aqueous phase stabilizer, 0.05-0.5 wt% oil phase stabilizer, 0.3-1 wt% oil-soluble initiator, 38-74.5 wt% oil phase solvent and 0-1 wt% aqueous phase solvent; The oil-soluble monomer is selected from at least one of methyl methacrylate, styrene, vinyl chloride, vinyl ester resin, acrylonitrile, vinyl acetate, and methyl acrylate; The in-situ reinforcing agent is selected from at least one of chromium acetate, chromium malonate, N,N'-methylenebisacrylamide, polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, formaldehyde, glutaraldehyde, phenolic resin, urea-formaldehyde resin, polyethyleneimine, n-butyl titanate, isopropyl titanate, tetrabutyl zirconate, aluminum citrate, aluminum chloride, zirconium acetate, zirconium lactate, zirconium citrate, zirconium oxychloride, zirconium sulfate, zirconium acetylacetone, organoboron zirconium, and organamine zirconium.

2. The method according to claim 1, characterized in that, In the composition, the volume ratio of combination A to combination B is 10-25:

1.

3. The method according to claim 1, characterized in that, In the composition, the mass ratio of the water-soluble initiator to composition A is 0.006-0.02:

1.

4. The method according to any one of claims 1-3, characterized in that, The water-soluble initiator is selected from a combination of ammonium persulfate and sodium bisulfite, or one of the following: ammonium persulfate.

5. The method according to any one of claims 1-3, characterized in that, The second crosslinking agent is selected from at least one of ethylene glycol dimethacrylate, triallyl isocyanurate, dicyclopentenyl acrylate, trimethylolpropane trimethacrylate, and 1,4-butanediol dimethacrylate.

6. The method according to any one of claims 1-3, characterized in that, The oil-soluble initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate; And / or, the aqueous phase stabilizer is selected from at least one of polyvinyl alcohol and polyethylene glycol; And / or, the oil phase stabilizer is selected from at least one of hexadecane, hexadecyl alcohol, and methyl isobutyl ketone; And / or, the emulsifier is selected from at least one of Span 80, Span 60, and Span 20.

7. The method according to claim 1, characterized in that, In step (2), the conditions for the polymerization reaction include: a temperature of 50-70°C and a time of 2-5 hours; And / or, in step (4), the conditions for the contact reaction include: a temperature of 25-45°C and a time of 4-6 hours.

8. The controlled-release, ultra-high temperature resistant, salt-resistant gel prepared by the method according to any one of claims 1-7.

9. The application of the controlled-release ultra-high temperature resistant and salt-resistant gel according to claim 8 in the sealing and profile control of gas and water channeling in oil and gas field development, underground storage, geothermal energy, and carbon sequestration projects.

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