Temperature and salt resistant in situ plugging enhanced gel composition, gels, and methods of making and using the same

Abstract

The present application relates to the technical field of oil field chemistry, and discloses a temperature-resistant and salt-resistant in-situ plugging enhanced gel composition, a gel and a preparation method and application thereof.The gel composition contains a first monomer, a second monomer, a first crosslinking agent, a second crosslinking agent, an initiator, an enhancer and water; optionally, the composition further contains a third monomer.The gel provided by the present application can be recrosslinked under the stimulation of high temperature and CO2 acidic conditions to form a block-shaped whole gel, thereby avoiding the problems of crosslinking uncertainty, chromatographic separation and easy reservoir damage of a crosslinking system in the ground, and simultaneously realizing the enhancement of plugging capacity under in-situ reservoir conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil field chemistry, in particular to a temperature-resistant and salt-resistant in-situ plugging enhanced gel composition, a gel and a preparation method and application thereof. BACKGROUND

[0002] Geological resources such as crude oil, natural gas, natural gas hydrate, geothermal fluid, etc. are all stored in underground reservoirs. In order to achieve efficient development, it is necessary to inject fluids (water, CO2, steam, polymer solution, etc.) into the underground to supplement the formation energy, so as to extract resources from the underground. In addition, carbon sequestration, gas storage and other underground space utilization technologies also need to inject fluids into the underground reservoir to achieve stable storage of fluids. The successful application of the above technologies requires that the injected fluid can be evenly migrated and distributed in the reservoir.

[0003] However, geological reservoirs often have strong heterogeneity due to the influence of sedimentation, structure, diagenesis, fluid and other factors. After injecting fluids into the underground, it is easy to occur channeling, leakage and other phenomena along faults, natural fractures, artificial fractures, micro-fractures and high permeability layers, which is an important reason for limiting the efficient development of geological energy and the safety of underground space utilization.

[0004] In order to solve the above problems of channeling and fluid leakage, gel plugging of channeling and leakage channels has always been considered an economic and effective method to reduce the heterogeneity of oil reservoirs. Underground crosslinking system is a widely used channeling plugging system in oilfield sites. The polymer, crosslinking agent and other chemicals are usually prepared into a gel solution and injected into the underground, and then the gel is formed at a certain temperature of the formation to plug the formation.

[0005] However, such gels have some uncertain factors during the gelation process, resulting in poor plugging effect. On the one hand, the gel solution is easy to enter the non-target layer after being injected into the underground, and the gelation will cause reservoir damage; on the other hand, when the gel solution passes through the formation porous medium, the interaction of various components in the gel solution with the surface of the rock is different, resulting in different migration speeds. This chromatographic separation phenomenon affects the subsequent gelation performance of the gel system.

[0006] Unlike the above channeling plugging system, the pre-crosslinked particle gel system is formed into gel particles on the ground, and the gel particles are prepared into a suspension and injected into the underground, avoiding the uncertainty of the gelation reaction under the formation conditions. At present, a variety of particle gel channeling plugging systems have been proposed at home and abroad to try to solve the problem of formation heterogeneity.

[0007] CN116023917A discloses a CO2 responsive gel system, its preparation method and a CO2 leakage prevention method for oil reservoirs. The viscosity of the gel system is low in the absence of CO2, and it is easy to inject. After reacting with CO2, the gel system forms a gel structure bridged by carbamate, thereby achieving the effect of plugging CO2. During CO2 flooding or storage, the CO2 responsive gel is injected into the leaked or easily leaked formation, which can effectively prevent and prevent CO2 leakage in the oil reservoir.

[0008] CN119529180A discloses a double-network CO2 responsive particle gel and its application method. The components of the system include 15%-20% acrylamide, 5%-10% zwitterionic monomer, 5%-10% CO2 responsive monomer, 0.25%-1% emulsifier, 0.05%-0.25% crosslinking agent, 0.075%-0.15% initiator and the balance water. The CO2 responsive monomer is composed of vinylpyridine and N,N-dimethylaminoethyl methacrylate in a mass ratio of (0.5-1):1. Then, indoor core displacement experiments are carried out, and it is found that when the core displacement is carried out in a core with a temperature of 60°C, a salt content of 10% in mineralized water and a fracture width of 0.3mm, the plugging rate of the gel particles is 99.0%.

[0009] CN105504158A discloses an intelligent gel particle that can be recrosslinked under formation conditions and a preparation method thereof. After the gel particle enters the formation, it can be recrosslinked under formation conditions to form a high-strength gel, thereby achieving effective plugging. The gel particle is mainly used to solve the problems of profile control, water plugging, filtration control and / or plugging during drilling and drilling completion.

[0010] CN112839994A discloses a recrosslinked particle gel for controlling CO2 consistency and preventing CO2 leakage. The technology provides a CO2 resistant particle gel that can be recrosslinked under underground conditions, which is used to improve the consistency of CO2 flow and control CO2 leakage problems.

[0011] The above technical solutions have the potential to solve fluid channeling and leakage to some extent, but oil and gas exploitation, storage, CO2 flooding and other projects often develop high-permeability fracture and cave channels. Although the traditional particle gel can reduce the permeability of high-permeability strips, fractures and large pores, it is limited by the matching relationship between the particle size and the channeling channel and the performance of the gel particle itself. Especially in the multiple harsh environments of high temperature, high salt, supercritical CO2 and acid corrosion in the reservoir, the traditional particle gel is difficult to achieve effective plugging, the plugging effect is short, and the economy of geological energy development and underground space utilization technology is reduced.

[0012] In addition, the traditional gel design relies on empirical trial and error method, and has problems of long cycle, high cost, and difficulty in global optimization. Especially in the face of complex reservoir environment of high temperature, high salt, acidic CO2 and other multi-factor coupling, the nonlinear interaction between components makes the molecular structure design and formula optimization inefficient.

[0013] In recent years, artificial intelligence technology has provided a new way for efficient design of functional gel by establishing a quantitative prediction model of material component-structure-performance. However, existing patents have not involved the directional design method of AI-driven temperature-resistant and salt-resistant CO2-responsive gel. SUMMARY

[0014] The purpose of the present application is to solve the problem that the traditional particle gel is difficult to resist the harsh environment of high temperature, high salt, supercritical CO2 acid corrosion and other multiple harsh environments of geological reservoir, and the plugging effect is short.

[0015] To achieve the above purpose, the first aspect of the present application provides a composition for a temperature-resistant and salt-resistant in-situ plugging enhanced gel, which contains a first monomer, a second monomer, a first crosslinking agent, a second crosslinking agent, an initiator, an enhancer and water; optionally, the composition further contains a third monomer;

[0016] The first monomer is selected from at least one of 2-acrylamido-2-methylpropane sulfonic acid, sodium styrene sulfonate, vinyl sulfonic acid, p-styrene sulfonic acid, 4-styrylbenzenesulfonic acid, methacrylic acid sulfobutyl ester, and propylene glycol sulfonate;

[0017] The second monomer is selected from at least one of N-vinyl pyrrolidone, diethylaminoethyl acrylate, dimethylaminoethyl methacrylate, vinyl imidazole, vinyl pyridine, and hydroxyethyl methacrylate;

[0018] The third monomer is selected from at least one of N-isopropyl acrylamide, hydroxyethyl acrylate, and N-(3-aminopropyl) methacrylamide;

[0019] The first crosslinking agent is selected from at least one of polyethyleneimine, borate compound, dialdehyde cellulose, N,N'-methylene bisacrylamide, and polyethylene glycol bisacrylate;

[0020] The second crosslinking agent is selected from a second acid-sensitive crosslinking agent and / or a second temperature-sensitive crosslinking agent;

[0021] The content of the first monomer is 5wt%-40wt%, the content of the second monomer is 5wt%-30wt%, the content of the third monomer is 0wt%-10wt%, the content of the first crosslinking agent is 0.01wt%-1wt%, the content of the second crosslinking agent is 0.01wt%-1wt%, the content of the reinforcing agent is 0.01wt%-10wt%, the content of the initiator is 0.01wt%-1wt%, and the balance is water, based on the total weight of the composition.

[0022] The second aspect of the present application provides a method for preparing a temperature-resistant and salt-resistant in-situ plugging enhanced gel, which is prepared by using the composition of the first aspect, and comprises: mixing and contacting the components in the composition to obtain the gel.

[0023] The third aspect of the present application provides the gel prepared by the second aspect.

[0024] The fourth aspect of the present application provides the use of the gel of the third aspect in at least one selected from the field of oilfield exploitation, the field of underground CO2 channeling plugging, and the field of CO2 geological storage.

[0025] The temperature-resistant and salt-resistant in-situ plugging enhanced gel prepared by the scheme of the present application can be pre-crosslinked into gel particles on the ground, and after being injected into a reservoir in the form of a suspension prepared by the gel particles and formation water, the gel particles can gather in strong channeling channel positions such as fractures, large pores and fracture-cavity, and under the stimulation of high temperature and CO2 acidity of the formation, the gel particles are recrosslinked to form a block-shaped integral gel.

[0026] The scheme provided by the present application avoids the problems of underground crosslinking system uncertainty, chromatographic separation and easy reservoir damage, and simultaneously realizes the enhancement of plugging capacity under in-situ reservoir conditions. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a physical map of the temperature-resistant and salt-resistant in-situ plugging enhanced gel Gel-1;

[0028] Figure 2 is the injection property test result of the temperature-resistant and salt-resistant in-situ plugging enhanced gel Gel-1. DETAILED DESCRIPTION

[0029] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are understood to be approximate values. The exact numerical values of the endpoints of the ranges and the separate points are not to be construed as being precise values, and they are understood to be used in a merely illustrative sense. Within the scope of this disclosure, any value can be used as a replacement for a value disclosed herein. For ranges, the endpoints are included within the range unless otherwise indicated. For numerical values, the endpoints are included within the range unless otherwise indicated.

[0030] It should be noted that, in various aspects of the present invention, for the same components in various aspects, the present invention is only described once in one aspect without repeated description, which should not be understood by those skilled in the art as a limitation of the present invention.

[0031] As mentioned above, the first aspect of the present invention provides a composition for a heat-resistant and salt-resistant in-situ plugging and reinforcing gel, the composition comprising a first monomer, a second monomer, a first cross-linking agent, a second cross-linking agent, an initiator, a reinforcing agent, and water; optionally, the composition further comprises a third monomer;

[0032] The first monomer is selected from at least one of 2-acrylamido-2-methylpropanesulfonic acid, sodium styrenesulfonate, vinylsulfonic acid, p-styrenesulfonic acid, 4-styrylbenzenesulfonic acid, sulfoethyl methacrylate, and hydroxypropanesulfonic acid;

[0033] The second monomer is selected from at least one of N-vinyl pyrrolidone, diethylaminoethyl acrylate, dimethylaminoethyl methacrylate, vinyl imidazole, vinyl pyridine, and hydroxyethyl methacrylate;

[0034] The third monomer is selected from at least one of N-isopropyl acrylamide, hydroxyethyl acrylate, and N-(3-aminopropyl) methacrylamide;

[0035] The first cross-linking agent is selected from at least one of polyethylene imine, borate compounds, dialdehyde cellulose, N,N'-methylenebisacrylamide, and polyethylene glycol diacrylate;

[0036] The second cross-linking agent is selected from a second acid-sensitive cross-linking agent and / or a second temperature-sensitive cross-linking agent;

[0037] Based on the total weight of the composition, the content of the first monomer is 5wt%-40wt%, the content of the second monomer is 5wt%-30wt%, the content of the third monomer is 0wt%-10wt%, the content of the first cross-linking agent is 0.01wt%-1wt%, the content of the second cross-linking agent is 0.01wt%-1wt%, the content of the reinforcing agent is 0.01wt%-10wt%, the content of the initiator is 0.01wt%-1wt%, and the balance is water.

[0038] Preferably, the content of the first monomer is 10wt%-35wt%, the content of the second monomer is 8wt%-20wt%, the content of the third monomer is 0wt%-5wt%, the content of the first crosslinking agent is 0.05wt%-0.5wt%, the content of the second crosslinking agent is 0.05wt%-0.5wt%, the content of the reinforcing agent is 0.05wt%-5wt%, the content of the initiator is 0.05wt%-0.5wt%, and the balance is water, based on the total weight of the composition.

[0039] Preferably, the second acid-sensitive crosslinking agent is selected from at least one of pinacol benzene boronic acid, tri-n-butyl borate, triethyl borate, diglycerol borate, trimethyl borate.

[0040] Preferably, the second temperature-sensitive crosslinking agent is selected from at least one of 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, hexamethylene diisocyanate-butanone oxime end-capped product, bis(trimethylsilyl)aminopropyl triethoxysilane.

[0041] According to a particularly preferred embodiment, the first monomer is 2-acrylamido-2-methylpropane sulfonic acid; the second monomer is N-vinyl pyrrolidone and / or dimethylaminoethyl methacrylate; the first crosslinking agent is polyethylene glycol bisacrylate; and the second crosslinking agent is pinacol benzene boronic acid. The inventors of the present application have found that in this preferred case, the gel provided by the present application can swell in the presence of supercritical CO2 in an acidic environment, the CO2-responsive group is protonated to become a positively charged ammonium salt, the molecular chain is stretched, the gel swells and exposes crosslinking sites. The inventors believe that the gel provided by the present application in the preferred case may have the following mechanism of action: under acidic conditions, the second crosslinking agent releases active sites after hydrolysis, the free boronic acid re-forms a dynamic covalent bond with the newly exposed vicinal diol group from the polyethylene glycol bisacrylate, re-crosslinks, forms an integral block structure, and further enhances the plugging capacity under in-situ reservoir conditions.

[0042] According to a particularly preferred embodiment, the first monomer is 2-acrylamido-2-methylpropanesulfonic acid; the second monomer is N-vinylpyrrolidone and / or dimethylaminoethyl methacrylate; the third monomer is N-isopropyl acrylamide; the first crosslinking agent is polyethylene glycol diacrylate; and the second crosslinking agent is 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane. The inventors of the present application have found that, in this preferred case, the gel provided by the present application, after entering the underground reservoir, at high temperatures, the 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane gradually hydrolyzes, exposing crosslinking sites, the hydrophilic groups in part of the polymer stretch into water, and water absorption and swelling are promoted. The inventors believe that the gel provided by the present application in the preferred case can have the following mechanism of action: under high temperature conditions, the active sites are released after the second crosslinking agent hydrolyzes, and after ring opening, they react with the surrounding amino groups / carboxyl groups to achieve recrosslinking, forming an overall block structure, and thus enhancing the plugging ability under in-situ reservoir conditions.

[0043] The present application does not have a particular requirement for the weight average molecular weight of the polyethyleneimine, which may, for example, be 1500-10000 g / mol.

[0044] Preferably, the reinforcing agent is a nanoparticle material with an average particle diameter of 10-500 nm.

[0045] Further preferably, the reinforcing agent is a nanoparticle material with an average particle diameter of 10-200 nm. The inventors have found that, in this preferred case, the mechanical strength of the recrosslinked plugging gel provided by the present application is better.

[0046] Further preferably, the reinforcing agent is selected from at least one of nanobentonite, nanosilica, nanotitanium oxide, nanometer aluminum oxide, nanometer calcium carbonate, carbon nanotubes, and graphene.

[0047] Further preferably, the reinforcing agent is selected from at least one of nanobentonite, nanosilica, nanotitanium oxide, nanometer aluminum oxide, and nanometer calcium carbonate.

[0048] Preferably, the initiator is selected from at least one of ammonium persulfate, sodium persulfate, potassium persulfate, tetramethyl ethylenediamine, and azobisisobutyronitrile.

[0049] Further preferably, the initiator is selected from at least one of ammonium persulfate, potassium persulfate, and sodium persulfate.

[0050] The inventors of the present application have found that the gel design method fused with artificial intelligence can significantly shorten the research and development cycle and guide the discovery of high-performance combinations that are difficult to find by traditional methods. The method includes:

[0051] (a) constructing a parameterized database containing the components of the first monomer, the second monomer, the first crosslinking agent, the second crosslinking agent, the initiator, the reinforcing agent, and water, collecting the molecular descriptors (such as the type of functional groups, the number of hydrophilic / hydrophobic groups, the molecular weight, the charge density) and the process conditions thereof;

[0052] (b) establishing a mapping model of the molecular structure and the components and the gel performance (recrosslinking time, breakthrough pressure, plugging rate) by a machine learning algorithm;

[0053] (c) searching for an optimal formula satisfying the target performance in the component constraint space by using an optimization algorithm.

[0054] As described above, the second aspect of the present application provides a method for preparing a temperature-resistant and salt-resistant in-situ plugging enhanced gel, which is performed by using the composition of the first aspect, and comprises: mixing and contacting the components in the composition to obtain the gel.

[0055] Preferably, the step of mixing and contacting comprises:

[0056] (1) performing ultrasonic dispersion treatment on the reinforcing agent in the presence of water to obtain solution 1;

[0057] (2) performing first contact between the solution 1 and a monomer material containing the first monomer and the second monomer to obtain solution 2; the monomer material optionally further contains a third monomer;

[0058] (3) sequentially adding the first crosslinking agent, the second crosslinking agent, and the initiator to the solution 2 to perform second contact, and performing gelation treatment on the obtained solution 3 to obtain intermediate 1;

[0059] (4) performing drying treatment on the intermediate 1 to obtain the gel.

[0060] Preferably, in step (1), the ultrasonic dispersion treatment is performed for 20-60 min.

[0061] According to a particularly preferred embodiment, the method further comprises, in step (1), before performing the ultrasonic dispersion treatment, introducing inert gas into the water for 10-40 min, and then performing the ultrasonic dispersion treatment.

[0062] Preferably, in step (2), the first contact is performed under the conditions of a temperature of 20-60℃, a time of 0.5-3 h, and a stirring speed of 500-1500 rpm.

[0063] Preferably, in step (3), the conditions of the second contacting include: temperature of 20-60℃, time of 1-6h, stirring speed of 500-1500rpm; and the temperature of the gelation treatment is 30-90℃, and the time is 4-24h. The inventors of the present application have found that, in this preferred case, the in-situ plugging enhanced gel provided by the present application has a three-dimensional network structure and has good water swelling capacity.

[0064] The present application does not have special requirements for the conditions of the gelation treatment in step (3), and those skilled in the art can use the known operations and process conditions in the art, and exemplarily, the gelation treatment can be carried out under static conditions.

[0065] Preferably, in step (4), the conditions of the drying treatment include: temperature of 40-90℃, time of 20-72h.

[0066] According to a particularly preferred embodiment, the method further comprises, in step (2), after the first contacting, adjusting the pH value of the solution 2 to 7-8, and then performing the step (3). The inventors of the present application have found that, in this preferred case, the CO2-responsive group in the second monomer in the scheme of the present application can be in a non-ionic state under this pH environment, thereby facilitating the shielding of the crosslinking sites and avoiding the uncertainty of the underground crosslinking system, while achieving the enhancement of the plugging capacity under the in-situ reservoir conditions.

[0067] Preferably, the method further comprises, in step (4), after the drying treatment, crushing the product obtained after drying to obtain the gel with a particle diameter of 20nm to 10mm. The inventors of the present application have found that, in this preferred case, the mineralizable plugging gel provided by the scheme of the present application has better CO2plugging efficiency. In addition, the gel synthesis method in the scheme of the present application is a one-pot method, and the bulk gel synthesized is difficult to reach the nanoscale after mechanical crushing; however, under the same synthesis conditions, using the reverse microemulsion method, the particle size can be optimized by controlling the water / oil ratio to synthesize gel particles of nanoscale (the minimum can be 20nm). The present application does not have special requirements for the conditions of the reverse microemulsion method, and for example, the method in Energy & Fuels, 2018 32 (3), 3068-3076 (DOI number: 10.1021 / acs.energyfuels.7b03649.) can be used for reference.

[0068] As described above, the third aspect of the present application provides the gel prepared by the second aspect.

[0069] As described above, the fourth aspect of the present application provides the use of the gel of the third aspect in at least one selected from the group consisting of the field of oilfield exploitation, the field of underground CO2 channeling plugging, and the field of CO2 geological storage.

[0070] The present application will be described in detail below by way of examples. In the following examples, various instruments and materials used are commercially available unless otherwise specified.

[0071] The first monomer I: 2-acrylamido-2-methylpropanesulfonic acid was purchased from Shanghai Jituo Biochemical Technology Co., Ltd., with the brand TCI-A0926-100G.

[0072] The first monomer II: sodium styrene sulfonate (SSS) was purchased from Beijing Huawei Ruikai Chemical Technology Co., Ltd., with the brand HWG00338.

[0073] The second monomer I: N-vinylpyrrolidone was purchased from Shanghai Jituo Biochemical Technology Co., Ltd., with the brand V20730.

[0074] The second monomer II: dimethylaminoethyl methacrylate was purchased from Beijing Inokai Technology Co., Ltd., with the brand R004180.

[0075] The third monomer: N-isopropyl acrylamide was purchased from Beijing Inokai Technology Co., Ltd., with the brand T77704.

[0076] The first crosslinking agent: polyethylene glycol diacrylate (PEGDA) was purchased from Shanghai Titan Science and Technology Co., Ltd., with the brand P17544.

[0077] The second acid-sensitive crosslinking agent: phenylboronic acid pinacol ester was purchased from Shanghai Titan Science and Technology Co., Ltd., with the brand GC37247.

[0078] The second temperature-sensitive crosslinking agent: 2-(3,4-epoxycyclohexyl) ethyl trimethoxysilane was purchased from Beijing Xinpaohai Chemical Technology Co., Ltd., with the brand E156231.

[0079] The initiator: ammonium persulfate.

[0080] The reinforcing agent I: nano-silicon dioxide with an average particle diameter of 20 nm was purchased from Beijing Inokai Technology Co., Ltd.

[0081] The reinforcing agent II: nano-silicon dioxide with an average particle diameter of 500 nm was purchased from Shanghai Maikelin Biochemical Technology Co., Ltd.

[0082] Room temperature or normal temperature as described herein means 25±2℃.

[0083] Example 1

[0084] (1) first, nitrogen is introduced into water for 30 min, then a reinforcing agent is added for ultrasonic dispersion treatment for 30 min to obtain solution 1;

[0085] (2) at 40°C, a monomer material containing the first monomer I and the second monomer I is added to the solution 1 for first contact, then the pH value is adjusted with 40% NaOH to obtain a solution 2 with a pH value of 7.5; the stirring speed of the first contact is 1200 rpm, and the stirring time is 2 h;

[0086] (3) at 40°C, a first crosslinking agent, a second crosslinking agent and an initiator are sequentially added to the solution 2 for second contact, the stirring speed of the second contact is 1200 rpm, and the stirring time is 2 h; and the obtained solution 3 is subjected to gelation treatment to obtain an intermediate 1, the gelation treatment is carried out at 40°C for 12 h;

[0087] (4) the intermediate 1 is subjected to drying treatment, the drying treatment is carried out at a temperature of 80°C for 24 h, and then subjected to crushing treatment to obtain a temperature-resistant and salt-resistant in-situ plugging and reinforcing gel, named as Gel-1, with an average particle diameter of 100 μm.

[0088] The remaining specific process parameters of this example are shown in Table 1.

[0089] Figure 1 is a physical map of the temperature-resistant and salt-resistant in-situ plugging and reinforcing gel Gel-1. Wherein, 1 is a block-shaped whole gel, and 2 is a gel particle after crushing.

[0090] Example 2

[0091] The same process as Example 1 is adopted, the difference is that the monomer material also contains a third monomer (N-isopropyl acrylamide), and the remaining steps are the same as Example 1, to obtain a particle gel, named as Gel-2.

[0092] The remaining specific process parameters of this example are shown in Table 1.

[0093] Examples 3-7

[0094] The same process as Example 1 is adopted, the difference is that the types / amounts of raw materials or process parameters are different, see Table 1 for details, to obtain a temperature-resistant and salt-resistant in-situ plugging and reinforcing gel.

[0095] Example 8

[0096] The same process as Example 1 is adopted, the difference is that the amount of raw materials is different, and the amount of raw materials is obtained by the following method:

[0097] The formulation data and performance indicators of Examples 1-7 and Comparative Example 1 (Tables 2 and 3) are collected, and the following features are extracted: monomer type, content, number of crosslinker functional groups, reinforcing agent particle size, process parameters (temperature, time);

[0098] With recrosslinking time, CO2 breakthrough pressure, and plugging rate as output targets, a random forest algorithm is used to train a prediction model, and the optimization objectives are set as: recrosslinking time ≤ 5 h at 150 ℃, breakthrough pressure ≥ 6.0 MPa / m, and plugging rate ≥ 99%;

[0099] An optimized formulation is obtained by searching within the component range of claim 1 using a genetic algorithm.

[0100] The remaining specific process parameters of this example are shown in Table 1.

[0101] Table 1

[0102]

[0103] Comparative Example 1

[0104] This comparative example is carried out using a method similar to Example 1, except that in step (3), 0.3 g of the first crosslinking agent is added, no second crosslinking agent is added, and the temperature of the second contact and gelation treatment is increased to 80 ℃. The remaining steps are the same as in Example 1, and a particulate gel is obtained, designated as KN-1.

[0105] Comparative Example 2

[0106] This comparative example is carried out using a method similar to Example 1, except that in step (3), 0.3 g of the second crosslinking agent is added, no first crosslinking agent is added, and the remaining steps are the same as in Example 1. The product prepared using this method fails to gel.

[0107] Test Example 1

[0108] Recrosslinking time comparison:

[0109] A high-precision electronic balance is used to weigh 5 g of the gel particles provided in Examples 1-7, respectively, and place them in a beaker containing the same volume of 10 wt% NaCl, and a plastic wrap is used to seal the beaker.

[0110] The beaker containing the gel sample is placed in a constant-temperature oven at 150 ℃, and the time is t 0, the time for weak crosslinking between the gel particles is recorded t 1, and the time for the disappearance of the boundaries between the particles is recorded t 2.

[0111] Table 2 is the re-crosslinking time of the temperature and salt resistant in-situ plugging enhanced gel Gel-1 to Gel-7 at 50℃, 100℃, 150℃, from which it can be seen that the increase of temperature helps to shorten the re-crosslinking time; at the same temperature, the re-crosslinking time of Gel-1 is the shortest; when the particle diameter of the enhancer is too large, the sensitivity of temperature to the re-crosslinking reaction is reduced, and the difference in re-crosslinking time at different temperatures becomes smaller; the re-crosslinking time of Gel-AI at 50℃ is 3.1h, which is close to the predicted value (3h).

[0112] Table 2

[0113]

[0114] Test Example 2

[0115] Injection test: the application exemplarily provides the test results of the in-situ plugging enhanced gel in Example 1.

[0116] Experimental device: high temperature and high pressure core displacement device.

[0117] Experimental material: the in-situ plugging enhanced gel (particle diameter of 80-100 mesh, i.e. 150-177μm) provided in Example 1.

[0118] Test steps:

[0119] 1) using a high-precision electronic balance, weigh 10g of gel particles, put them into a 1L beaker filled with 10wt% NaCl for swelling, and place them at room temperature for 24h, then take out the swollen gel particles and remove the surface free water;

[0120] 2) place the above treated particle gel in the middle container;

[0121] 3) prepare fracture cores with different fracture openings, including 0.1mm, 0.3mm, 0.5mm, 1mm and 2mm, and place the above fracture cores in the core holder;

[0122] 4) start the experimental device constant temperature system, and control the experimental temperature at 150℃;

[0123] 5) start the constant speed and constant pressure pump, and inject the swollen gel particles from the middle container into the fracture core at a constant speed of 0.5mL / min until particles are produced and the injection pressure reaches equilibrium, and record the gel injection process pressure gradient respectively.

[0124] Figure 2 is the injection test result of the temperature and salt resistant in-situ plugging enhanced gel Gel-1, from which it can be seen that the injection pressure gradient of the gel is small, and the gel has good injectivity. Figure 2It can be seen that the Gel-1 has good injectivity, and no obvious re-crosslinking occurs in the gel particles during the injection process to reduce the injectivity.

[0125] Test Example 3

[0126] CO2 breakthrough pressure test:

[0127] Experimental device and experimental materials: consistent with Test Example 2.

[0128] Test steps:

[0129] 1) 10 g of the particulate gel was weighed using a high-precision electronic balance, and was placed in a 1L beaker filled with 1wt% NaCl for swelling, and was placed at room temperature for 24 h. The swollen gel particles were taken out, and the free water on the surface was removed.

[0130] 2) The treated particulate gel was placed in a core holder.

[0131] 3) The constant-speed constant-pressure pump was started, and the expanded gel particles were injected from the middle container into the fractured core at a constant speed of 0.5 mL / min until the particles were produced, and the injection pressure reached equilibrium.

[0132] 4) The device temperature was increased to 150 ℃, 0.1 fracture volume (FPV) of CO2 was injected, so that the gel particles were re-crosslinked in the fracture, and the re-crosslinking time was referred to Table 2.

[0133] 5) After the gel particles were completely crosslinked, the displacement experiment was performed using CO2.

[0134] 6) The CO2 was injected at a constant pressure of 0.05 MPa in the constant-pressure mode, and the outlet pipeline was placed in an aqueous solution for observing whether the CO2 broke through. Specifically, when bubbles were produced, it indicated that the CO2 had broken through. When no bubbles were produced at the outlet end after 5 minutes, the CO2 injection pressure was increased, and the injection pressure was gradually increased by 0.05 MPa each time until bubbles appeared at the outlet end.

[0135] Table 3 is the CO2 breakthrough pressure test results of the temperature-resistant and salt-resistant in-situ plugging enhanced gels Gel-1 to Gel-7 and KN-1. As can be seen from Table 3, compared with KN-1 which does not have re-crosslinking ability, the gel particles of Gel-1 to Gel-7 are mutually adhered after re-crosslinking reaction, and have good plugging tightness; the CO2 breakthrough pressure of Gel-AI is 6.7 MPa / m, which is close to the predicted value (6.8 MPa / m).

[0136] Table 3

[0137]

[0138] Test Example 4

[0139] Sealing performance test: After the end of test example 3, the sealing ability of the gel to CO2 under high temperature and high pressure conditions was further explored.

[0140] Experimental device and experimental materials: consistent with test example 3.

[0141] Test steps:

[0142] 1) Set the back pressure to 30 MPa, and control the experimental temperature to be above 150℃.

[0143] 2) Inject CO2 into the sealed fracture core at a constant speed of 0.5 mL / min, and record the pressure values at both ends of the fracture core during the CO2 injection process.

[0144] 3) After the pressure at both ends of the core is stable, stop the CO2 injection, and maintain the high temperature and high pressure CO2 conditions to make the gel in the fracture recrosslink. The recrosslinking time is referred to Table 2.

[0145] 4) Start CO2 injection again, maintain a constant injection speed (0.5 mL / min), and record the core pressure values at both ends of the core.

[0146] 5) Calculate the sealing rate of the gel before and after recrosslinking to the fracture by formula (1) and formula (2).

[0147] Formula (1),

[0148] Formula (2),

[0149] In the formula, F rr is the residual resistance coefficient, dimensionless; K pregel is the permeability before gel injection, D; K postgel is the permeability after gel injection, D; is the differential pressure at both ends of the core after gel injection, MPa; is the differential pressure at both ends of the core before gel injection, MPa; E P is the sealing efficiency of the gel.

[0150] According to the calculation by formula (1) and formula (2), the sealing rates of the temperature-resistant and salt-resistant in-situ sealing enhanced gel Gel-1 to the fracture before and after recrosslinking are 85.5% and 99.9% respectively, indicating that the gel has sealing ability and in-situ self-enhancing performance under high temperature (150℃) and acidic CO2 (pH is 1.5~2) environment; the sealing efficiency of Gel-AI after recrosslinking is 99.98%, which is close to the predicted value (99.99%).

[0151] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Various simple modifications can be made to the technical solutions of the present application within the technical concept of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A composition for heat-resistant and salt-resistant in-situ plugging enhancement gel, characterized in that: The composition contains a first monomer, a second monomer, a first crosslinking agent, a second crosslinking agent, an initiator, a reinforcing agent and water; optionally, the composition further contains a third monomer; The first monomer is selected from at least one of 2-acrylamido-2-methylpropanesulfonic acid, sodium styrenesulfonate, vinylsulfonic acid, p-styrenesulfonic acid, 4-styrylbenzenesulfonic acid, sulfoethyl methacrylate, and hydroxypropanesulfonic acid; The second monomer is selected from at least one of N-vinyl pyrrolidone, diethylaminoethyl acrylate, dimethylaminoethyl methacrylate, vinyl imidazole, vinyl pyridine, and hydroxyethyl methacrylate; The third monomer is selected from at least one of N-isopropyl acrylamide, hydroxyethyl acrylate, and N-(3-aminopropyl) methacrylamide; The first cross-linking agent is polyethylene glycol diacrylate; The second cross-linking agent is selected from a second acid-sensitive cross-linking agent and / or a second temperature-sensitive cross-linking agent; The second acid-sensitive crosslinking agent is selected from at least one of phenylboronic acid pinacol ester, tri-n-butyl borate, triethyl borate, diglycerol borate, and trimethyl borate; The second temperature-sensitive crosslinking agent is selected from at least one of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, hexamethylene diisocyanate-butanone oxime end-capping product, and bis(trimethylsilyl)aminopropyltriethoxysilane; Based on the total weight of the composition, the content of the first monomer is 5wt%-40wt%, the content of the second monomer is 5wt%-30wt%, the content of the third monomer is 0wt%-10wt%, the content of the first cross-linking agent is 0.01wt%-1wt%, the content of the second cross-linking agent is 0.01wt%-1wt%, the content of the reinforcing agent is 0.01wt%-10wt%, the content of the initiator is 0.01wt%-1wt%, and the balance is water.

2. The composition according to claim 1, characterized in that Based on the total weight of the composition, the content of the first monomer is 10wt%-35wt%, the content of the second monomer is 8wt%-20wt%, the content of the third monomer is 0wt%-5wt%, the content of the first cross-linking agent is 0.05wt%-0.5wt%, the content of the second cross-linking agent is 0.05wt%-0.5wt%, the content of the reinforcing agent is 0.05wt%-5wt%, the content of the initiator is 0.05wt%-0.5wt%, and the balance is water.

3. The composition according to claim 1, characterized in that The reinforcing agent is a nanoparticle material with an average particle diameter of 10nm-200nm; And / or, the reinforcing agent is selected from at least one of nano-bentonite, nano-silicon dioxide, nano-titanium oxide, nano-aluminum oxide, nano-calcium carbonate, carbon nanotubes, and graphene.

4. The composition according to claim 3, characterized in that The initiator is selected from at least one of ammonium persulfate, sodium persulfate, potassium persulfate, tetramethylethylenediamine, and azobisisobutyronitrile.

5. A method for preparing a heat-resistant and salt-resistant in-situ plugging enhancement gel, characterized in that: The method is carried out using the composition according to any one of claims 1 to 4, and comprises: mixing and contacting the components in the composition to obtain the gel.

6. The method according to claim 5, characterized in that The step of performing the mixed contact comprises: (1) In the presence of water, the enhancer is subjected to ultrasonic dispersion treatment to obtain solution 1; (2) contacting the solution 1 with a monomer material containing a first monomer and a second monomer to obtain a solution 2; the monomer material optionally further contains a third monomer; (3) adding a first crosslinking agent, a second crosslinking agent, and an initiator to the solution 2 in sequence for a second contact, and subjecting the obtained solution 3 to a gelling treatment to obtain an intermediate 1; (4) Drying the intermediate 1 to obtain the gel.

7. The method according to claim 6, characterized in that In step (1), the ultrasonic dispersion treatment time is 20 min-60 min; And / or, in step (2), the conditions of the first contact include: temperature of 20-60°C, time of 0.5-3h, stirring speed of 500-1500rpm; And / or, in step (3), the conditions of the second contact include: temperature of 20-60°C, time of 1-6 hours, stirring speed of 500-1500 rpm; the temperature of the gelling treatment is 30-90°C, time of 4-24 hours; And / or, in step (4), the drying treatment conditions include: temperature of 40-90°C and time of 20-72h.

8. The method according to claim 6, characterized in that The method further comprises, in step (2), adjusting the pH value of the solution 2 to 7-8 after the first contact, and then performing step (3).

9. A gel prepared by the method according to any one of claims 5 to 8.

10. Use of the gel according to claim 9 in at least one of the fields selected from the group consisting of oil field exploitation, underground CO2 crossflow blocking, and CO2 geological storage.

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