Gel plugging agent as well as preparation method and application thereof

Abstract

The invention relates to a gel plugging agent as well as a preparation method and application thereof. The gel plugging agent is prepared from the following raw material components: a water-soluble temperature-resistant quadripolymer, 4, 4-dihydroxydiphenylmethane, hexamethylenetetramine, a stabilizing auxiliary agent and a cross-linking delaying auxiliary agent, wherein the water-soluble temperature-resistant quadripolymer accounts for 0.1 to 3.0 parts by mass, the 4, 4-dihydroxydiphenylmethane accounts for 0.1 to 3.0 parts by mass, the hexamethylenetetramine accounts for 0.1 to 3.0 parts by mass, the stabilizing aid accounts for 0.1 to 3 parts by mass, the cross-linking delaying aid accounts for 0.02 to 0.6 part by mass, and the water-soluble temperature-resistant quadripolymer is obtained by copolymerization of four monomers, namely acrylamide, acrylonitrile, lactam and methylpropanesulfonic acid. The water-soluble temperature-resistant quadripolymer, the 4, 4-dihydroxydiphenylmethane and the hexamethylenetetramine are crosslinked into gel to form mesh-structure gel with dense pores and high strength, the stability of the gel in the environments of high temperature, shearing and the like is realized by binding the movement of water molecules, and the temperature resistance and the shearing resistance of the gel plugging agent are improved.

Description

Technical Field

[0001] This application relates to the field of oilfield development technology, and in particular to a gel plugging agent, its preparation method and application. Background Technology

[0002] In reservoirs where steam injection is used for thermal recovery, high-temperature resistant plugging agents are required for profile control or water shut-off. Currently, gel plugging agents are the most widely researched and used plugging agents. Gel plugging agents are typically gel systems formed by inorganic metal ion crosslinked polymer gel systems, as well as organic crosslinked agent gel systems such as phenolic resin crosslinked polymer gel systems and polyethyleneimine crosslinked polymer gel systems. Among these, gel systems formed by organic crosslinked agents exhibit better high-temperature resistance than those formed by inorganic metal ion crosslinked gel systems.

[0003] However, the sealing ability of conventional organic cross-linked polymer gels deteriorates at temperatures above 100℃~120℃. In steam injection thermal recovery processes such as steam huff and puff, steam drive, and steam-assisted gravity drainage, the injected steam temperature reaches over 300℃, and the reservoir temperature is often above 200℃. Conventional polymer gels cannot meet the high-temperature conditions of steam injection reservoirs or have a short effective period. Due to the prominent problems of uneven steam absorption and steam channeling in the mid-to-late stages of steam huff and puff, and during steam drive and steam-assisted gravity drainage, it is necessary to study high-temperature plugging methods for steam injection thermal recovery reservoirs to meet the requirements for high-temperature plugging and improved development efficiency. Summary of the Invention

[0004] This application provides a gel plugging agent, its preparation method, and its application to solve the following technical problem: how to improve the temperature resistance of the gel plugging agent.

[0005] In a first aspect, this application provides a gel plugging agent, wherein the raw material components of the gel plugging agent include: a water-soluble, heat-resistant quaternary copolymer, 4,4-dihydroxydiphenylmethane, and hexamethylenetetramine; wherein, by weight,

[0006] The water-soluble, heat-resistant quaternary copolymer is 0.1 to 3.0 parts, the 4,4-dihydroxydiphenylmethane is 0.1 to 3.0 parts, and the hexamethylenetetramine is 0.1 to 3.0 parts;

[0007] The water-soluble, heat-resistant quaternary copolymer is obtained by copolymerizing four monomers: acrylamide, acrylonitrile, lactam, and methylpropanesulfonic acid.

[0008] Optionally, the water-soluble, heat-resistant quaternary copolymer meets the following specifications: molecular weight of 3 million to 10 million, hydrolysis...

[0009] The degree can be 10% to 30%.

[0010] Optionally, the raw material components of the gel plugging agent may also include: stabilizing agents and crosslinking delaying agents.

[0011] Optionally, the stabilizing agent includes at least one of the following: isopropanol, butanol; and / or,

[0012] The crosslinking delaying agent includes at least one of the following: oxalic acid and acetic acid.

[0013] Optionally, the stabilizing agent is 0.1 to 3.0 parts, and the retarding crosslinking agent is 0.02 to 0.6 parts.

[0014] Secondly, this application provides a method for preparing the gel plugging agent according to any one of the first aspects, the method comprising:

[0015] The crosslinking retarder, hexamethylenetetramine, and water-soluble heat-resistant quaternary copolymer are added to the solvent in sequence to carry out the first mixing and obtain the first mixed solution.

[0016] The stabilizer was mixed with 4,4-dihydroxydiphenylmethane to obtain a second mixed solution.

[0017] The first mixed solution and the second mixed solution are mixed a third time to obtain a gel plugging agent.

[0018] Thirdly, this application provides an application of the gel plugging agent described in any one of the first aspects in oil reservoir development.

[0019] Optionally, the application includes: sequentially injecting a first protective gas, a gel plugging agent, and a second protective gas into the oilfield underground to achieve the plugging effect of the gel plugging agent in oil reservoir development.

[0020] Optionally, the first protective gas and the second protective gas each include at least one of the following: carbon dioxide, nitrogen, and natural gas.

[0021] Optionally, the volume of the first protective gas at standard atmospheric pressure and the volume of the second protective gas at standard atmospheric pressure are 50 to 200 times the volume of the gel plugging agent, respectively.

[0022] The technical solutions provided in this application have the following advantages compared with the prior art:

[0023] The gel plugging agent provided in this application embodiment has excellent temperature resistance due to its water-soluble, heat-resistant quaternary copolymer. The water-soluble, heat-resistant quaternary copolymer can control the viscosity of the gel plugging agent before and after gelation, ensuring the injection and sealing performance of the gel plugging agent into the formation. The water-soluble, heat-resistant quaternary copolymer, 4,4-dihydroxydiphenylmethane, and hexamethylenetetramine can crosslink to form a dense, high-strength network structure gel. By binding the movement of water molecules, the gel achieves stability under high temperature and shear conditions, thereby improving the temperature resistance and shear resistance of the gel plugging agent. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 A microstructure image of a gel plugging agent after gelation at 120°C, provided in an embodiment of this application;

[0027] Figure 2 A schematic flowchart illustrating a method for preparing a gel plugging agent according to an embodiment of this application;

[0028] Figure 3 This is a diagram showing the state of a gel plugging agent after gelation at 120°C, as provided in Example 4 of this application.

[0029] Figure 4 This is a diagram showing the state of a gel plugging agent after gelation at 150°C, as provided in Example 4 of this application.

[0030] Figure 5 This is a diagram showing the state of a gel plugging agent after gelation at 180°C, as provided in Example 4 of this application.

[0031] Figure 6 The gel plugging agent provided in this application embodiment is in the gelation state after gelation under 5MPa carbon dioxide and 120°C conditions. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0033] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0034] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0035] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0036] In a first aspect, this application provides a gel plugging agent, the raw material components of which include: a water-soluble heat-resistant quaternary copolymer, 4,4-dihydroxydiphenylmethane, and hexamethylenetetramine; wherein, by weight, the water-soluble heat-resistant quaternary copolymer is 0.1 to 3.0 parts, the 4,4-dihydroxydiphenylmethane is 0.1 to 3.0 parts, and the hexamethylenetetramine is 0.1 to 3.0 parts;

[0037] The water-soluble, heat-resistant quaternary copolymer is obtained by copolymerizing four monomers: acrylamide, acrylonitrile, lactam, and methylpropanesulfonic acid.

[0038] In the embodiments of this application, the water-soluble heat-resistant quaternary copolymer exhibits excellent temperature resistance (temperature resistance greater than...).

[0039] (120℃) The water-soluble, heat-resistant quaternary copolymer can regulate the viscosity of the gel plugging agent before and after gelation, ensuring the injection and sealing properties of the gel plugging agent for the formation; 4,4-dihydroxydiphenylmethane and hexamethylenetetramine synergistically act as crosslinking agents, and the water-soluble, heat-resistant quaternary copolymer, 4,4-dihydroxydiphenylmethane and hexamethylenetetramine can crosslink to form a dense, high-strength network structure gel, and achieve the stability of the gel under high temperature and shear conditions by binding the movement of water molecules, thereby improving the temperature resistance and shear resistance of the gel plugging agent.

[0040] The water-soluble, heat-resistant quaternary copolymer can be 0.1 to 3.0 parts, which can adjust the viscosity of the gel plugging agent before and after gelation, ensuring the injection and sealing properties of the gel plugging agent in the oil field, while taking into account the gelation performance and heat resistance of the gel plugging agent.

[0041] The 4,4-dihydroxydiphenylmethane can be 0.1 to 3.0 parts, and the hexamethylenetetramine can be 0.1 to 3.0 parts, thereby achieving crosslinking polymerization of the water-soluble heat-resistant quaternary copolymer with 4,4-dihydroxydiphenylmethane and hexamethylenetetramine to form a gel blocker with an ideal molecular weight, ensuring the gel-forming effect of the gel blocker. For example, the water-soluble heat-resistant quaternary copolymer can be 0.1, 0.2, 0.5, 1.0, 2.0, or 3.0 parts, the 4,4-dihydroxydiphenylmethane can be 0.1, 0.2, 0.5, 1.0, 2.0, or 3.0 parts, and the hexamethylenetetramine can be 0.1, 0.2, 0.5, 1.0, 2.0, or 3.0 parts. The polymer monomers of this water-soluble, heat-resistant quaternary copolymer include acrylamide, acrylonitrile, lactam, and methylpropanesulfonic acid. These four monomers can be polymerized to obtain a heat-resistant quaternary copolymer with high molecular chain strength and good stability. To ensure the water solubility of the quaternary copolymer, it requires hydrolysis treatment to convert some amide groups into carboxyl groups, increasing the hydrophilicity of the quaternary copolymer and thus obtaining a water-soluble, heat-resistant quaternary copolymer. This process also has a positive impact on the viscosity and temperature resistance of the gel plugging agent.

[0042] In some embodiments, the water-soluble, heat-resistant quaternary copolymer meets the following specifications: molecular weight of 3 million to 10 million, and degree of hydrolysis of 10% to 30%.

[0043] In the embodiments of this application, the molecular weight of the water-soluble heat-resistant quaternary copolymer can be from 3 million to 10 million, which allows the water-soluble heat-resistant quaternary copolymer to have good water solubility and gelling properties. The degree of hydrolysis of the water-soluble heat-resistant quaternary copolymer can be from 10% to 30%, which can simultaneously take into account the water solubility, gelling properties, and heat resistance of the water-soluble heat-resistant quaternary copolymer. For example, the molecular weight of the above-mentioned water-soluble heat-resistant quaternary copolymer can be 3 million, 4 million, 5 million, 6 million, 7 million, 8 million, 9 million, 10 million, etc., and the degree of hydrolysis can be 10%, 15%, 20%, 25%, 30%, etc.

[0044] In some embodiments, the raw material components of the gel plugging agent further include: stabilizing agents and retarding crosslinking agents.

[0045] In some embodiments, the stabilizing agent includes at least one of the following: isopropanol, butanol; and / or,

[0046] The crosslinking delaying agent includes at least one of the following: oxalic acid and acetic acid.

[0047] In some embodiments, the stabilizing agent is 0.1 to 3.0 parts, and the retarding crosslinking agent is 0.02 to 0.6 parts.

[0048] In this embodiment, the raw material components of the gel plugging agent may further include stabilizers and crosslinking retarder. The stabilizer ensures that the water-soluble, heat-resistant quaternary copolymer, 4,4-dihydroxydiphenylmethane, and hexamethylenetetramine are uniformly dispersed and stabilized in the solvent, achieving uniform gelation of the gel plugging agent. The crosslinking retarder ensures the gelation rate of the gel, achieving the injection performance and reservoir gelation depth of the gel plugging agent. The stabilizer can be one or more combinations of isopropanol and butanol, and the crosslinking retarder can be one or more combinations of oxalic acid and acetic acid. Under the action of the stabilizer and crosslinking retarder, the water-soluble, heat-resistant quaternary copolymer, 4,4-dihydroxydiphenylmethane, and hexamethylenetetramine crosslink to form a dense, high-strength network structure gel. This structure achieves stability of the gel under high temperature and shear conditions by binding water molecules. Figure 1 A microstructure image of a gel plugging agent after gelation at 120°C, provided in an embodiment of this application; please refer to [link to microstructure image]. Figure 1 The gel, after gelation, forms pores with a size of 1 to 5 micrometers, creating a dense network structure. In contrast, conventional gels have larger pores, lower strength, and poor polymer stability, resulting in weak water binding capacity. Under conditions such as high temperature and shear, they cannot bind water molecules, and some polymer molecules even break down, causing the gel to fail. Stabilizing agents can be 0.1 to 3.0 parts to ensure the gelation effect of the gel plugging agent, while crosslinking retarder agents can be 0.02 to 0.6 parts to regulate the gelation rate and delay crosslinking. For example, stabilizing agents can be 0.1, 0.2, 0.5, 1.0, 2.0, and 3.0 parts, and crosslinking retarder agents can be 0.02, 0.04, 0.1, 0.2, 0.4, and 0.6 parts. Furthermore, the raw material components of the aforementioned gel plugging agent also include a solvent, which is generally water.

[0049] Secondly, this application provides a method for preparing the gel plugging agent according to any one of the first aspects. Figure 2 A schematic flowchart illustrating a method for preparing a gel plugging agent according to an embodiment of this application; please refer to [link / reference]. Figure 2 The method includes:

[0050] S1. The crosslinking retarder, hexamethylenetetramine, and water-soluble, heat-resistant quaternary copolymer are added sequentially to the solvent to...

[0051] Perform the first mixing to obtain the first mixed solution;

[0052] S2. The stabilizer is mixed with 4,4-dihydroxydiphenylmethane to obtain a second mixed solution;

[0053] S3. The first mixed solution and the second mixed solution are mixed for a third time to obtain a gel plugging agent.

[0054] In the embodiments of this application, the solvent can generally be water, and hexamethylenetetramine and the retarded crosslinking aid can be used.

[0055] as well as

[0056] A water-soluble, heat-resistant quaternary copolymer is added to a solvent and stirred for 10–30 minutes to obtain a first mixed solution; 4,4-dihydroxydiphenylmethane is added to a stabilizing agent and stirred for 10–30 minutes to obtain a second mixed solution; the second mixed solution is added to the first mixed solution and stirred for 10–30 minutes to obtain a gel blocker.

[0057] The preparation method of the above-mentioned water-soluble heat-resistant quaternary copolymer includes the following steps: preparing an aqueous solution of polymeric monomers and an initiator, and reacting it at a certain temperature to obtain the water-soluble heat-resistant quaternary copolymer; the polymeric monomers are acrylamide, acrylonitrile, lactam, and methylpropanesulfonic acid. The mass fraction of the polymeric monomers in the aqueous phase is 10% to 25%. The initiator is potassium persulfate or azobisisobutyronitrile, and the mass fraction of the initiator in the aqueous phase is 0.05% to 0.15%. Specifically, it includes: Step 1: At room temperature, the polymeric monomers are added to deionized water and stirred at 350 to 600 r / min for 15 to 40 min, then the initiator is added and stirred at 350 to 600 r / min for 15 to 40 min to obtain an aqueous solution; Step 2: The aqueous solution obtained in Step 1 is stirred in a water bath at 60 to 80°C at 350 to 550 r / min for 4 to 6 h to obtain a heat-resistant quaternary copolymer solution; Step 3: Add sodium hydroxide at a mass of 0.1 to 0.2 times that of acrylamide monomer to the heat-resistant quaternary copolymer solution obtained in step 2, and stir for 15 to 30 minutes at a speed of 350 to 600 r / min in a water bath at 50 to 60°C to obtain a water-soluble heat-resistant quaternary copolymer solution; Step 4: Wash the water-soluble heat-resistant quaternary copolymer solution obtained in step 3 with anhydrous ethanol and filter it 3 times. Place the filter material in an oven at 50 to 70°C and dry it for more than 12 hours to obtain the water-soluble heat-resistant quaternary copolymer.

[0058] The preparation method of this gel plugging agent is based on the above-mentioned gel plugging agent. The specific raw materials of the gel plugging agent can be referred to in the above embodiments. Since the preparation method of this gel plugging agent adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0059] Thirdly, this application provides an application of the gel plugging agent described in any one of the first aspects in oil reservoir development.

[0060] In some embodiments, the application includes: sequentially injecting a first protective gas, a gel plugging agent, and a second protective gas into the underground of the oil field to achieve the plugging effect of the gel plugging agent in oil reservoir development.

[0061] In some embodiments, the first protective gas and the second protective gas each include at least one of the following: carbon dioxide, nitrogen, and natural gas.

[0062] In this embodiment, since the temperature of high-temperature reservoirs in steam-injected thermal recovery can reach 250°C or even higher, while the relatively stable temperature of the high-temperature resistant gel after gelation in this embodiment is below 200°C, the excessively high temperature in steam-injected thermal recovery reservoirs will shorten the effective period of the injected high-temperature resistant gel slugs. Injecting gas before injecting the high-temperature resistant gel slugs can isolate the injected high-temperature resistant gel slugs from the high-temperature steam or hot water in the formation. The subsequently injected high-temperature resistant gel slugs will reduce the formation temperature to below 200°C, prolonging the stabilization time of the injected high-temperature resistant gel slugs, and thus extending the effective period of the high-temperature resistant gel slug's plugging effect. Furthermore, the subsequent injection of high-temperature steam will shorten the effective period of the injected high-temperature resistant gel slugs. Injecting gas before subsequent steam injection can isolate the injected high-temperature resistant gel slugs from the subsequently injected high-temperature steam or hot water, prolonging the stabilization time of the injected high-temperature resistant gel slugs, and thus extending the effective period of the high-temperature resistant gel slug's plugging effect. Therefore, by injecting protective gas slugs before and after injecting the high-temperature resistant gel plugging agent into the steam injection thermal recovery high-temperature reservoir, the high-temperature resistant gel plugging agent is isolated from the underground steam and the injected steam, thus achieving high-temperature plugging control in the steam injection thermal recovery reservoir. This protective gas can be one or a combination of carbon dioxide, nitrogen, and natural gas.

[0063] In some embodiments, the volume of the first protective gas at standard atmospheric pressure and the volume of the second protective gas at standard atmospheric pressure are 50 to 200 times the volume of the gel plugging agent, respectively.

[0064] In this embodiment, the volume of the first protective gas and the volume of the second protective gas under standard atmospheric pressure can be 50 to 200 times the volume of the gel plugging agent, respectively. Injecting a moderate volume of gas ensures effective isolation without causing excessive gas leakage or a significant drop in the temperature of the underground steam chamber, thus affecting the mining effect. Conversely, injecting too little gas weakens the isolation effect of the gas on the high-temperature resistant gel slug, affecting the plugging effect. For example, the volumes of the first and second protective gases under standard atmospheric pressure can be 50, 70, 90, 110, 130, 150, 170, 190, and 200 times the volume of the gel plugging agent, respectively.

[0065] The gel plugging agent provided in this application can be used for profile control in injection wells and plugging in production wells in high-temperature oil reservoirs. Furthermore, this gel plugging agent can be used for the development of deep-buried high-temperature oil reservoirs; it can be used for steam-driven heavy oil reservoir development, steam huff-and-puff heavy oil reservoir development, fire-driven heavy oil reservoir development, and high-temperature hot water-driven heavy oil reservoir development. The gel plugging agent has a gelation time of 3 to 45 hours at an ambient temperature of 50°C to 150°C, and its cross-linked gel remains structurally stable at high temperatures of 150°C to 200°C with a slow gel breaking rate.

[0066] The application of this gel plugging agent in oil reservoir development is based on the above-mentioned gel plugging agent. The specific raw materials of the gel plugging agent can be referred to in the above embodiments. Since the application of this gel plugging agent in oil reservoir development adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0067] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0068] The preparation method of the water-soluble heat-resistant quaternary copolymer in Examples 1 to 7 includes: preparing an aqueous solution of copolymer monomers and an initiator, and reacting it at a certain temperature to obtain the water-soluble heat-resistant quaternary copolymer; the monomers of the copolymer are acrylamide, acrylonitrile, lactam and methylpropanesulfonic acid, and the mass fraction of each copolymer monomer in the aqueous phase is 10%; the initiator is azobisisobutyronitrile, and the mass fraction of the initiator in the aqueous phase is 0.05%. Specifically, the process includes: Step 1: At room temperature, the four copolymer monomers are added to deionized water and stirred at 500 r / min for 30 min, then an initiator is added and stirred at 500 r / min for 25 min to obtain an aqueous solution; Step 2: The aqueous solution obtained in Step 1 is stirred in a water bath at 75°C at 450 r / min for 5 h to obtain a quaternary copolymer; Step 3: Sodium hydroxide at 0.15 times the mass of acrylamide monomer is added to the quaternary copolymer obtained in Step 2 and stirred in a water bath at 55°C at 450 r / min for 20 min to obtain a water-soluble heat-resistant quaternary copolymer; Step 4: The water-soluble heat-resistant quaternary copolymer obtained in Step 3 is washed and filtered three times with anhydrous ethanol, and the filter is dried in a 60°C oven for 16 h to obtain a water-soluble heat-resistant quaternary copolymer.

[0069] Example 1

[0070] The components of the gel plugging agent (by weight) are: 0.5 parts water-soluble heat-resistant quaternary copolymer + 0.5 parts 4,4-dihydroxydiphenylmethane + 0.5 parts hexamethylenetetramine + 0.5 parts isopropanol + 0.05 parts oxalic acid.

[0071] The preparation method of the gel plugging agent includes: adding 0.5g hexamethylenetetramine, 0.05g oxalic acid and 0.5g water-soluble heat-resistant quaternary copolymer sequentially to 97.95g water, stirring for 20 minutes to obtain a first mixed solution; adding 0.5g 4,4-dihydroxydiphenylmethane to 0.5g isopropanol and stirring for 20 minutes to obtain a second mixed solution; adding the second mixed solution to the first mixed solution and stirring for 30 minutes to obtain the gel plugging agent.

[0072] The gelling agent in Example 1 gelled in 12 hours at 120°C and in 8 hours at 150°C. Before gelation, the viscosity at 50°C was 96.7 mPa·s; after gelation, the viscosity was 9275.7 mPa·s at 50°C, 6428.6 mPa·s at 150°C, and 3742.2 mPa·s at 180°C.

[0073] Example 2

[0074] The components of the gel plugging agent (by weight) are: 0.3 parts water-soluble heat-resistant quaternary copolymer + 0.3 parts 4,4-dihydroxydiphenylmethane + 0.3 parts hexamethylenetetramine + 0.3 parts butanol + 0.06 parts oxalic acid.

[0075] The preparation method of the gel plugging agent includes: adding 0.3g hexamethylenetetramine, 0.06g oxalic acid and 0.3g water-soluble heat-resistant quaternary copolymer sequentially to 98.74g water, stirring for 15 minutes to obtain a first mixed solution; adding 0.3g 4,4-dihydroxydiphenylmethane to 0.3g isopropanol and stirring for 15 minutes to obtain a second mixed solution; adding the second mixed solution to the first mixed solution and stirring for 30 minutes to obtain the gel plugging agent.

[0076] In Example 2, the gelation time of the gelling agent was 24 hours at an ambient temperature of 120°C and 16 hours at an ambient temperature of 150°C. The viscosity at 50°C before gelation was 76.3 mPa·s, and the viscosity at 50°C after gelation was 6543.7 mPa·s, 4342.8 mPa·s at 150°C, and 3281.3 mPa·s at 180°C.

[0077] Example 3

[0078] The components of the gel plugging agent (by weight) are: 0.7 parts water-soluble heat-resistant quaternary copolymer + 0.7 parts 4,4-dihydroxydiphenylmethane + 0.7 parts hexamethylenetetramine + 0.7 parts isopropanol + 0.14 parts oxalic acid.

[0079] The preparation method of the gel plugging agent includes: adding 0.7g hexamethylenetetramine, 0.14g oxalic acid and 0.7g water-soluble heat-resistant quaternary copolymer sequentially to 97.06g water, stirring for 15 minutes to obtain a first mixed solution; adding 0.7g 4,4-dihydroxydiphenylmethane to 0.7g isopropanol and stirring for 15 minutes to obtain a second mixed solution; adding the second mixed solution to the first mixed solution and stirring for 30 minutes to obtain the gel plugging agent.

[0080] The gelling agent in Example 3 gelled in 16 hours at 120°C and in 12 hours at 150°C. Before gelation, the viscosity at 50°C was 156.8 mPa·s; after gelation, the viscosity was 18432.6 mPa·s at 50°C, 13789.4 mPa·s at 150°C, and 9463.5 mPa·s at 180°C.

[0081] Example 4

[0082] The components of the gel plugging agent (by weight) are: 1.0 part water-soluble heat-resistant quaternary copolymer + 1.0 part 4,4-dihydroxydiphenylmethane + 1.0 part hexamethylenetetramine + 1.0 part butanol + 0.2 part oxalic acid.

[0083] The preparation method of the gel plugging agent includes: adding 1.0g hexamethylenetetramine, 0.2g oxalic acid and 1.0g water-soluble heat-resistant quaternary copolymer sequentially to 95.8g water, stirring for 25 minutes to obtain a first mixed solution; adding 1.0g 4,4-dihydroxydiphenylmethane to 1.0g isopropanol and stirring for 15 minutes to obtain a second mixed solution; adding the second mixed solution to the first mixed solution and stirring for 30 minutes to obtain the gel plugging agent.

[0084] The gelling agent in Example 4 gelled in 10 hours at 120°C and in 8 hours at 150°C. Before gelation, the viscosity at 50°C was 239.8 mPa·s; after gelation, the viscosity was 27643.5 mPa·s at 50°C, 21684.3 mPa·s at 150°C, and 18049.6 mPa·s at 180°C.

[0085] Example 5

[0086] The components of the gel plugging agent (by weight) are: 2.0 parts of heat-resistant quaternary copolymer + 2.0 parts of 4,4-dihydroxydiphenylmethane + 2.0 parts of hexamethylenetetramine + 2.0 parts of isopropanol + 0.40 parts of oxalic acid.

[0087] The preparation method of the gel plugging agent includes: adding 2.0g hexamethylenetetramine, 0.4g oxalic acid and 2.0g water-soluble heat-resistant quaternary copolymer sequentially to 91.6g water, stirring for 30 minutes to obtain a first mixed solution; adding 2.0g 4,4-dihydroxydiphenylmethane to 2.0g isopropanol and stirring for 15 minutes to obtain a second mixed solution; adding the second mixed solution to the first mixed solution and stirring for 30 minutes to obtain the gel plugging agent.

[0088] The gelling agent in Example 5 gelled in 8 hours at an ambient temperature of 120°C and in 6 hours at an ambient temperature of 150°C. Before gelation, the viscosity at 50°C was 362.6 mPa·s; after gelation, the viscosity was 42837.5 mPa·s at 50°C, 33978.2 mPa·s at 150°C, and 27463.9 mPa·s at 180°C.

[0089] Example 6

[0090] The components of the gel plugging agent (by weight) are: 3.0 parts of heat-resistant quaternary copolymer + 3.0 parts of 4,4-dihydroxydiphenylmethane + 3.0 parts of hexamethylenetetramine + 3.0 parts of isopropanol + 0.60 parts of oxalic acid.

[0091] The preparation method of the gel plugging agent includes: adding 3.0g of hexamethylenetetramine, 0.6g of oxalic acid and 3.0g of water-soluble heat-resistant quaternary copolymer sequentially to 87.4g of water, stirring for 30 minutes to obtain a first mixed solution; adding 3.0g of 4,4-dihydroxydiphenylmethane to 3.0g of isopropanol and stirring for 15 minutes to obtain a second mixed solution; adding the second mixed solution to the first mixed solution and stirring for 30 minutes to obtain the gel plugging agent.

[0092] The gelling agent in Example 6 gelled in 6 hours at an ambient temperature of 120°C and in 4 hours at an ambient temperature of 150°C. Before gelation, the viscosity at 50°C was 513.2 mPa·s; after gelation, the viscosity was 61383.5 mPa·s at 50°C, 49378.2 mPa·s at 150°C, and 40621.7 mPa·s at 180°C.

[0093] The gel plugging formulations in Examples 1-6 were compared with the viscosity test results before and after gelation. It can be seen that, under the condition of satisfying injectability (viscosity less than 500 mPa·s), the gel plugging formulations in Examples 4 and 5 have higher strength after gelation. Furthermore, the gel structure state of the gel plugging formulation in Example 4 was observed after gelation at different temperatures (120℃, 150℃, and 180℃). Figure 3 This is a diagram showing the state of a gel plugging agent after gelation at 120°C, as provided in Example 4 of this application. Figure 4This is a diagram showing the state of a gel plugging agent after gelation at 150°C, as provided in Example 4 of this application. Figure 5 This is a diagram showing the state of a gel plugging agent after gelation at 180°C, as provided in Example 4 of this application; please refer to [link / reference]. Figures 3-5 It can be seen that the gel formulation can form a stable gel plugging agent under high temperature conditions, which can meet the requirements of oilfield field for the high temperature resistance of the plugging agent.

[0094] The viscosity of the gel plugging agent of Example 4 after gelation in the absence of CO2 and under a CO2 pressure of 5 MPa is shown in Table 1. Figure 6 The gel blocking agent provided in this application embodiment is shown in its gelled state under conditions of 5 MPa carbon dioxide and 120°C; please refer to [link to relevant documentation]. Figure 6 It can be seen that the gel blocker provided in the embodiments of this application has a good gelling effect in high-temperature gelation in CO2 environment.

[0095] Table 1. Viscosity test results of gel plugging agent after gelation under 5MPaCO2 conditions.

[0096]

[0097] Example 7

[0098] In Example 7, the gel plugging agent formulation and preparation method from Example 4 of this application were used for high-temperature plugging of a steam-driven heavy oil reservoir. The reservoir was 800m deep, with three oil layers totaling 20m in thickness, and the underground heavy oil viscosity was 74000mPa·s. After 10 rounds of steam huff and puff development using a square well pattern with a 70m well spacing, the central well was converted to a steam injection well for a reverse nine-point well pattern steam drive. The steam drive lasted for 3 years (with a stage recovery rate of 10%). Then, the gel plugging agent provided in Example 4 was used for high-temperature plugging. The injection intensity of this gel plugging agent was 40m. 3 / m, with the pre- and post-injection CO2 volumes both 100 times the gel plugging agent volume, and high-temperature plugging performed annually for a total of 3 rounds. Using CMG numerical simulation software, it is predicted that implementing the aforementioned gel and CO2 high-temperature plugging three times on top of steam drive can increase crude oil production by 5921.7m³ compared to steam drive. 3 The recovery rate increased by 6.18%, and the output-input ratio reached 2.52.

[0099] One or more technical solutions in the embodiments of this application have at least the following technical effects or advantages:

[0100] (1) The gel plugging agent provided in this application has good cross-linking gelation and high temperature resistance, and can be used to modify or plug the reservoir under high temperature conditions, thereby improving the reservoir exploitation effect;

[0101] (2) The gel plugging agent provided in this application uses water-soluble heat-resistant quaternary copolymer, 4,4-dihydroxydiphenylmethane, hexamethylenetetramine, isopropanol, butanol, oxalic acid and acetic acid, which are all commonly used chemical reagents and are highly feasible.

[0102] (3) The gel plugging agent provided in this application has the characteristics of low initial viscosity, gelation at high temperature, stable viscosity at high temperature and good salt resistance. It has good sealing properties at high temperature and can be used in deep-buried high-temperature oil reservoirs or thermally recovered high-temperature oil reservoirs.

[0103] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A gel plugging agent, characterized in that, The raw material components of the gel plugging agent include: a water-soluble, heat-resistant quaternary copolymer, 4,4-dihydroxydiphenylmethane, and hexamethylenetetramine; wherein, by mass parts, The water-soluble, heat-resistant quaternary copolymer is 0.1 to 3.0 parts, the 4,4-dihydroxydiphenylmethane is 0.1 to 3.0 parts, and the hexamethylenetetramine is 0.1 to 3.0 parts; The water-soluble, heat-resistant quaternary copolymer is obtained by copolymerizing four monomers: acrylamide, acrylonitrile, lactam, and methylpropanesulfonic acid.

2. The gel plugging agent according to claim 1, characterized in that, The water-soluble, heat-resistant quaternary copolymer meets the following specifications: molecular weight of 3 million to 10 million, and degree of hydrolysis of 10% to 30%.

3. The gel plugging agent according to claim 1, characterized in that, The raw material components of the gel plugging agent also include: stabilizing agents and crosslinking delaying agents.

4. The gel plugging agent according to claim 3, characterized in that, The stabilizing agent includes at least one of the following: isopropanol, butanol; and / or, The crosslinking delaying agent includes at least one of the following: oxalic acid and acetic acid.

5. The gel plugging agent according to claim 3 or 4, characterized in that, The stabilizing agent is 0.1 to 3 parts, and the retarding crosslinking agent is 0.02 to 0.6 parts.

6. A method for preparing the gel plugging agent according to any one of claims 1 to 5, characterized in that, The method includes: The crosslinking retarder, hexamethylenetetramine, and water-soluble heat-resistant quaternary copolymer are added to the solvent in sequence to carry out the first mixing and obtain the first mixed solution. The stabilizer was mixed with 4,4-dihydroxydiphenylmethane to obtain a second mixed solution. The first mixed solution and the second mixed solution are mixed a third time to obtain a gel plugging agent.

7. The application of the gel plugging agent according to any one of claims 1 to 5 in oil reservoir development.

8. The application according to claim 7, characterized in that, The applications include: A first protective gas, a gel plugging agent, and a second protective gas are sequentially injected into the underground of the oil field to achieve the plugging effect of the gel plugging agent in oil reservoir development.

9. The application according to claim 8, characterized in that, The first protective gas and the second protective gas each include at least one of the following: carbon dioxide, nitrogen, and natural gas.

10. The application according to claim 8 or 9, characterized in that, The volume of the first protective gas at standard atmospheric pressure and the volume of the second protective gas at standard atmospheric pressure are 50 to 200 times the volume of the gel plugging agent, respectively.

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