Composite temporary plugging agents suitable for different temperature gradients and their preparation methods

Abstract

This invention discloses a composite temporary plugging agent suitable for different temperature gradients and its preparation method, belonging to the field of oil and gas field development technology. The composite temporary plugging agent comprises the following components by mass parts: silica sand: 2-4 parts; glass microspheres: 8-10 parts; alkaline solution: 1-3 parts; silane coupling agent: 4-6 parts; organic solvent: 80-90 parts; polymer monomer one: 4-10 parts; crosslinking agent one: 0.2-1.2 parts; polymer monomer two: 17-24 parts; comonomer: 4-5 parts; crosslinking agent two: 0.06-0.3 parts; initiator: 0.06-0.12 parts; modified nano-blended material: 0 parts or 3-6 parts; dispersant: 0.3-0.6 parts; viscous modifying liquid: 20-25 parts; wherein, the viscous modifying liquid comprises tetraethyl orthosilicate: 3-7 parts; dimethyl silicone oil: 3-7 parts. This invention effectively improves the fracturing effect of deep unconventional reservoirs, overcomes the shortcomings of existing temporary plugging agents in terms of insufficient performance and difficulty in synergizing key performances under high temperature and high pressure environments, and realizes their reliable application in reservoirs with different temperature gradients.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, and in particular to a composite temporary plugging agent suitable for different temperature gradients and its preparation method. Background Technology

[0002] With the increasing depletion of conventional oil and gas resources, the strategic importance of unconventional oil and gas resources has significantly increased. Deep shale oil and gas resources are widely distributed and abundant, and are considered an important alternative in the process of energy decarbonization. However, unconventional reservoirs are generally characterized by extremely low permeability, strong heterogeneity, and well-developed natural fractures. When using conventional fracturing techniques, only single symmetrical fractures are often formed, making it difficult to achieve economical and efficient development. Introducing temporary plugging agents during fracturing can block existing fractures, forcing fracturing fluid to form new fractures or activate natural fractures in the formation. This generates new fractures or activates natural fracture networks in the reservoir, effectively expanding the stimulation volume, increasing fracture complexity, and ultimately improving single-well production.

[0003] Although temporary plugging technology plays a significant role in unconventional oil and gas development, existing plugging agents (such as rigid particles, fibers, and chemical gels) still have many shortcomings and defects in application. In particular, under the harsh geological environment (high temperature and high pressure) of deep unconventional reservoirs, conventional plugging agents are prone to structural instability and functional failure during fracturing operations, severely limiting the effectiveness of the fracturing. On the one hand, their temperature and pressure resistance is insufficient, making them prone to softening, degradation, or failure in deep, high-temperature, and high-pressure reservoirs. On the other hand, there is a contradiction between their two key properties—"high temperature resistance and high pressure bearing capacity"—and "low density and controllable degradation," making it difficult to effectively balance them, and compromising the success rate of in-fracture temporary plugging fracturing operations. These problems severely restrict the application of temporary plugging technology in deep shale oil and gas development.

[0004] Current research has achieved good results in the development of high-temperature resistant and high-strength gel systems. However, current techniques still have shortcomings. Regarding high-temperature resistance, related literature 1 (CN117304894 A) improves the temperature resistance of the temporary plugging agent by adding thermoplastic materials (such as polyimide). Although this can increase the temperature resistance of the temporary plugging agent to about 250℃, the degradation temperature required is too high, making it impossible to achieve timely and complete degradation under conventional reservoir conditions. In addition, this method is costly to prepare and has poor economic efficiency.

[0005] The composite temporary plugging material provided in related literature 2 (CN116875288A) has a compressive strength of up to 120 MPa at room temperature, but its mass loss rate exceeds 80% at a high temperature of 120℃, resulting in the loss of plugging function; more importantly, its degradation products are acidic, and it is only suitable for carbonate reservoirs, which limits its scope of application.

[0006] In related literature 3 (CN116042198A), a temperature-responsive bio-based temporary plugging agent was obtained by epoxidation modification of vegetable oil. It has excellent plugging performance and certain temperature adaptability, but its applicable temperature range is limited to 90-160℃, which cannot meet the more refined temperature response and performance synergy requirements in ultra-high temperature reservoirs (e.g., ≥200℃) or medium temperature reservoirs (e.g., [80℃, 120℃]).

[0007] The above content is only used to help understand the technical solution of the present invention and does not represent an admission that the above content is prior art. Summary of the Invention

[0008] The main objective of this invention is to provide a composite temporary plugging agent and its preparation method suitable for different temperature gradients, aiming to solve or partially solve the above-mentioned problems.

[0009] To achieve the above objectives, the present invention provides a composite temporary plugging agent suitable for different temperature gradients. The composite temporary plugging agent comprises the following components by mass parts: silica sand: 2-4 parts; glass microspheres: 8-10 parts; alkaline solution: 1-3 parts; silane coupling agent: 4-6 parts; organic solvent: 80-90 parts; polymeric monomer one: 4-10 parts; crosslinking agent one: 0.2-1.2 parts; polymeric monomer two: 17-24 parts; comonomer: 4-5 parts; crosslinking agent two: 0.06-0.3 parts; initiator: 0.06-0.12 parts; modified nano-blended material: 0 parts or 3-6 parts; dispersant: 0.3-0.6 parts; viscous modifying liquid: 20-25 parts; wherein the viscous modifying liquid comprises tetraethyl orthosilicate: 3-7 parts; dimethyl silicone oil: 3-7 parts.

[0010] The alkaline solution is sodium hydroxide or ammonia solution, with a concentration of 2 wt% when the alkaline solution is sodium hydroxide solution and a concentration of 25 wt% when the alkaline solution is ammonia solution.

[0011] The organic solvent is ethanol with a concentration of 85 wt%.

[0012] The polymer monomer is one or more of sodium alginate, κ-carrageenan, and guar gum;

[0013] The dispersant is one or more of sodium citrate, sodium metasilicate, and sodium pyrophosphate.

[0014] The crosslinking agent is one or more of glucono-δ-lactone, potassium chloride, calcium disodium ethylenediaminetetraacetate, and glutaraldehyde.

[0015] The polymer monomer 2 is acrylamide;

[0016] The comonomer is one or more of 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, and trimethylolpropane trimethacrylate;

[0017] The second crosslinking agent is one of N'N-methylenebisacrylamide and polyethylene glycol diacrylate;

[0018] The initiator is two of the following: ammonium persulfate, potassium persulfate, and sodium bisulfite, and the molar ratio of the two substances in the initiator is 1:1.

[0019] The modified nano-blended material is a nanomaterial obtained by modifying the surface and edges of nano-lithium saponite with sodium pyrophosphate.

[0020] The viscous modification liquid is tetraethyl orthosilicate or dimethyl silicone oil.

[0021] Preferably, it includes:

[0022] Silica sand and glass microspheres are combined to form a microcore, and the obtained microcore is added to an alkaline solution and stirred evenly for pretreatment;

[0023] After mixing the silane coupling agent with a mixture of organic solvent and alkaline solution, the pretreated micronuclei are added, stirred thoroughly, filtered, and dried to obtain rigid micronuclei.

[0024] Based on the working temperature of the composite temporary plugging agent to be prepared, prepare a matrix layer at the corresponding working temperature gradient;

[0025] The prepared matrix layer is blended with the rigid microcore to obtain a hybrid material;

[0026] The prepared mixed material is heated to cause polymer monomer one and polymer monomer two in the mixed material to undergo cross-linking reactions respectively, forming a double network gel.

[0027] The obtained double-network gel was cut into blocks, dried, granulated and sieved to obtain matrix particles.

[0028] Tetraethyl orthosilicate, dimethyl silicone oil and deionized water are mixed and stirred to form a uniform and viscous modified liquid. The ratio of tetraethyl orthosilicate, dimethyl silicone oil and deionized water is determined according to the working temperature of the composite temporary plugging agent to be prepared.

[0029] The obtained modified liquid was added to the matrix particles at room temperature, stirred evenly at a constant temperature, allowed to stand to allow the particles to settle, the liquid was removed, and the settled particles were transferred to a container coated with a release agent and cured to obtain surface-modified temporary plugging agent particles.

[0030] Preferably, the working temperature of the composite temporary plugging agent is [80℃, 120℃];

[0031] Accordingly, the step of preparing a matrix layer at a corresponding operating temperature gradient based on the operating temperature of the composite temporary plugging agent to be prepared includes:

[0032] Under nitrogen protection, monomer one was stirred with deionized water at room temperature until completely dispersed to obtain the first solution;

[0033] Add dispersant, polymeric monomer II, and comonomer sequentially to the first solution, and stir at room temperature until completely dispersed to obtain the second solution;

[0034] The second solution is subjected to vacuum degassing to obtain a homogeneous third solution;

[0035] Add crosslinking agent one, crosslinking agent two, and initiator to the third solution, stir to dissolve, and obtain the matrix layer;

[0036] Wherein, the first polymeric monomer is κ-type carrageenan, and the mass fraction of the first polymeric monomer is 4-6 parts;

[0037] The first crosslinking agent is potassium chloride, and the mass fraction of the first crosslinking agent is 0.2-0.4.

[0038] Crosslinking agent two is N,N'-methylenebisacrylamide, and the mass fraction of crosslinking agent two is 0.06-0.1.

[0039] Preferably, the working temperature of the composite temporary plugging agent is (120℃, 160℃);

[0040] Accordingly, the step of preparing a matrix layer at a corresponding operating temperature gradient based on the operating temperature of the composite temporary plugging agent to be prepared includes:

[0041] Under nitrogen protection, monomer one was stirred with deionized water at room temperature until completely dispersed to obtain the first solution;

[0042] Add dispersant, polymeric monomer II, and comonomer sequentially to the first solution, and stir at room temperature until completely dispersed to obtain the second solution;

[0043] The second solution is subjected to vacuum degassing to obtain a homogeneous third solution;

[0044] Add crosslinking agent one, crosslinking agent two, and initiator to the third solution, stir to dissolve, and obtain the matrix layer;

[0045] Wherein, the first polymer is sodium alginate, and the mass fraction of the first polymer monomer is 5-10 parts;

[0046] The crosslinking agent is glucono-δ-lactone and calcium disodium ethylenediaminetetraacetate, and the molar ratio of glucono-δ-lactone to calcium disodium ethylenediaminetetraacetate is 1:2.

[0047] Crosslinking agent two is N'N-methylenebisacrylamide, and the mass fraction of crosslinking agent two is 0.2-0.3.

[0048] Preferably, the working temperature of the composite temporary plugging agent is (160℃, 200℃);

[0049] Accordingly, the step of preparing a matrix layer at a corresponding operating temperature gradient based on the operating temperature of the composite temporary plugging agent to be prepared includes:

[0050] Under nitrogen protection, monomer one was stirred with deionized water at room temperature until completely dispersed to obtain the first solution;

[0051] A dispersant, polymeric monomer II, comonomer, and modified nano-blended material are added sequentially to the first solution, and stirred at room temperature until completely dispersed to obtain a second solution.

[0052] The second solution is subjected to vacuum degassing to obtain a homogeneous third solution;

[0053] Add crosslinking agent II and initiator to the third solution, stir to dissolve, and obtain the matrix layer;

[0054] Wherein, the first polymer is a gelatin, and the first polymer monomer has a mass fraction of 5-10 parts;

[0055] Crosslinking agent two is N'N-methylenebisacrylamide, and the mass fraction of crosslinking agent two is 0.2-0.3.

[0056] Preferably, in the step of mixing tetraethyl orthosilicate, dimethyl silicone oil, and deionized water and stirring to form a uniform viscous modified liquid,

[0057] When the working temperature of the composite temporary plugging agent is [80℃, 120℃], the mass fractions of the tetraethyl orthosilicate and the dimethyl silicone oil are 3 parts and 3 parts, respectively.

[0058] Preferably, in the step of mixing tetraethyl orthosilicate, dimethyl silicone oil, and deionized water and stirring to form a uniform viscous modified liquid,

[0059] When the working temperature of the composite temporary plugging agent is (120℃, 160℃), the mass fractions of the tetraethyl orthosilicate and the dimethyl silicone oil are 5 parts and 5 parts, respectively.

[0060] Preferably, in the step of mixing tetraethyl orthosilicate, dimethyl silicone oil, and deionized water and stirring to form a uniform viscous modified liquid,

[0061] When the working temperature of the composite temporary plugging agent is (160℃, 200℃), the mass fractions of the tetraethyl orthosilicate and the dimethyl silicone oil are 7 parts and 7 parts, respectively.

[0062] The present invention has at least the following beneficial effects:

[0063] The composite temporary plugging agent provided by this invention precisely adjusts the concentration ratio and chemical formula of its different functional components according to the specific temperature conditions of the target reservoir. This controllable design enables the temporary plugging agent to synergistically optimize high-efficiency plugging performance and controllable degradation characteristics within a specific reservoir temperature range, thereby effectively improving the fracturing effect of deep unconventional reservoirs. It overcomes the shortcomings of existing temporary plugging agents in terms of insufficient performance and difficulty in synergizing key performance characteristics under high temperature and high pressure environments, and enables its reliable application in reservoirs with different temperature gradients.

[0064] Furthermore, the composite temporary plugging agent provided by this invention possesses a strong energy loss mechanism matrix, a rigid reinforcing phase, and a temperature-controlled protective material. The rigid reinforcing phase, acting as a micro-core, provides a stable structural support for the strong energy loss mechanism matrix layer (the flexible temporary plugging body), effectively enhancing the pressure-bearing capacity of the fracture sealing. The temperature-controlled protective material, with its high content, maintains the material's temperature-time dependent degradation, facilitating its transport in fracturing fluid and its arrival at the target location. By leveraging the synergistic effect of the "strong energy loss mechanism matrix layer + rigid reinforcing phase + temperature-controlled protective material," the problem of conventional intra-fracture temporary plugging agents being unable to simultaneously achieve "high temperature resistance, high pressure resistance" and "low density, degradability" is overcome. Ultimately, a composite particulate intra-fracture temporary plugging agent that meets the requirements of "remote transport, efficient plugging, and controllable degradation" in different temperature ranges of deep unconventional reservoirs is constructed. To achieve the core temporary plugging functions of pressure resistance, expansion, and temperature resistance of the matrix layer, the matrix is ​​prepared using a one-pot method, drawing on the concept of a dual-network structure. Attached Figure Description

[0065] Figure 1 A schematic diagram illustrating the preparation method of the low-density particulate temporary plugging agent provided by the present invention;

[0066] Figure 2 This is a graph showing the change in the water absorption and swelling ratio (120℃) of the modified particles of this invention over time.

[0067] Figure 3 A comparison chart of the mass expansion ratio (120℃) of modified particulate plugging agent and unmodified particulate plugging agent;

[0068] Figure 4 A comparison chart of the storage modulus and loss modulus of different composite temporary plugging agents;

[0069] Figure 5 A sample image of a rigid microcore in gel state provided by this invention;

[0070] Figure 6 The molecular structure formula and synthesis principle diagram of a first network gel of the intermediate-temperature composite temporary plugging agent provided by the present invention;

[0071] Figure 7 The molecular structure formula and synthesis principle diagram of the first network gel of the medium-high temperature composite temporary plugging agent provided by the present invention;

[0072] Figure 8 The molecular structure formula and synthesis principle diagram of the first network gel of the ultra-high temperature composite temporary plugging agent provided by the present invention;

[0073] Figure 9 The molecular structure formula and synthesis principle diagram of an embodiment of the second network gel (medium temperature, medium high temperature, and ultra-high temperature composite temporary plugging agent) provided by the present invention;

[0074] Figure 10 This is a schematic diagram illustrating the principle of matrix particle surface modification provided by the present invention.

[0075] Figure 11 Infrared spectra of different intermediate products provided by the present invention;

[0076] Figure 12 Infrared spectral results of the nanocomposite final product (composite temporary plugging agent)

[0077] Figure 13 SEM image of P(AM-co-SSS), a single-network intermediate (i.e., the first network gel);

[0078] Figure 14 SEM image of the dual-network end product (i.e., dual-network gel) κ-CG / P (AM-co-SSS);

[0079] Figure 15 SEM image of the dual-network final product (i.e., dual-network gel) SA / P (AM-co-SSS);

[0080] Figure 16 SEM image of Cur. / P(AM-co-SSS), a dual-network intermediate (i.e., dual-network gel);

[0081] Figure 17 SEM image of the dual-network final product (i.e., dual-network gel) Cur. / P(AM-co-SSS) / Laponite.

[0082] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0083] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details are presented in the embodiments of the present invention to facilitate a better understanding of the invention. However, the technical solutions claimed in the present invention can be implemented even without these technical details and various variations and modifications based on the following embodiments. The division of the following embodiments is for ease of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined with and referenced by each other without contradiction.

[0084] Therefore, the present invention provides a composite temporary plugging agent suitable for different temperature gradients, comprising the following components in parts by mass:

[0085] Silica sand: 2-4 parts; glass microspheres: 8-10 parts; alkaline solution: 1-3 parts; silane coupling agent: 4-6 parts; organic solvent: 80-90 parts; polymer monomer one: 4-10 parts; crosslinking agent one: 0.2-1.2 parts; polymer monomer two: 17-24 parts; comonomer: 4-5 parts; crosslinking agent two: 0.06-0.3 parts; initiator: 0.06-0.12 parts; modified nano-blended material: 0 parts or 3-6 parts; dispersant: 0.3-0.6 parts; viscous modifying liquid: 20-25 parts; wherein, the viscous modifying liquid includes tetraethyl orthosilicate: 3-7 parts; dimethyl silicone oil: 3-7 parts.

[0086] Of course, in some implementations, the composite temporary plugging agent suitable for different temperature gradients also includes water. The mass fraction of water is not specifically limited here and can be determined according to actual needs.

[0087] The alkaline solution is sodium hydroxide or ammonia solution, with a concentration of 2 wt% when the alkaline solution is sodium hydroxide solution and a concentration of 25 wt% when the alkaline solution is ammonia solution.

[0088] The organic solvent is ethanol with a concentration of 85 wt%.

[0089] The polymer monomer is one or more of sodium alginate, κ-carrageenan, and guar gum.

[0090] The dispersant is one or more of sodium citrate, sodium metasilicate, and sodium pyrophosphate.

[0091] The crosslinking agent is one or more of glucono-δ-lactone, potassium chloride, calcium disodium ethylenediaminetetraacetate, and glutaraldehyde.

[0092] The second polymer monomer is acrylamide.

[0093] The comonomer is one or more of 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, and trimethylolpropane trimethacrylate.

[0094] The second crosslinking agent is one of N'N-methylenebisacrylamide and polyethylene glycol diacrylate.

[0095] The initiator is two of the following: ammonium persulfate, potassium persulfate, and sodium bisulfite, and the molar ratio of the two substances in the initiator is 1:1.

[0096] The modified nano-blended material is a nanomaterial obtained by modifying the surface and edges of nano-lithium saponite with sodium pyrophosphate. The modified nano-blended material is 0 parts or 3-6 parts. When the operating temperature of the prepared composite temporary plugging agent is 80-160℃, the modified nano-blended material is 0 parts. When the operating temperature of the prepared composite temporary plugging agent is (160℃, 200℃), the modified nano-blended material is 3-6 parts. In some embodiments, the modified nano-blended material is nano-lithium saponite.

[0097] The viscous modified liquid comprises tetraethyl orthosilicate and dimethyl silicone oil, with the remainder being water.

[0098] Figure 1 The diagram illustrates the preparation method of the composite temporary plugging agent provided by the present invention. The preparation method of the composite temporary plugging agent can be divided into three processes: preparation of rigid microcore, preparation of matrix layer, blending of matrix layer and rigid microcore, and preparation of surface-modified temporary plugging agent particles.

[0099] (1) Fabrication of rigid micronuclei

[0100] The fabrication of the rigid micronucleus includes steps S110 and S120.

[0101] In step S110, silica sand and glass microspheres are combined to form a microcore, and the obtained rigid microcore is added to an alkaline solution and stirred evenly for pretreatment.

[0102] The mass fractions of silica sand and glass microspheres are 2-4 parts and 8-10 parts, respectively. Specifically, the first mass ratio of silica sand to glass microspheres is 1:(2-5).

[0103] Specifically, silica sand and glass microspheres are compounded in a first mass ratio (1:(2-5)) to form micronuclei. 10-12 parts of the formed micronuclei are added to a sodium hydroxide solution (in which the number of sodium hydroxide parts is 1-3 parts) and stirred evenly for pretreatment.

[0104] In some embodiments, silica sand and glass microspheres are compounded in a first mass ratio (1:(2-5)) to form micronuclei. 10-12 parts of the formed micronuclei are added to 200 ml of sodium hydroxide solution (of which the number of sodium hydroxide parts is 2 parts), and the mixture is magnetically stirred in a water bath at 85°C for 3 h. After washing with deionized water, the mixture is dried at 60°C for 24 h.

[0105] In step S120, the silane coupling agent is mixed with a mixture of organic solvent and alkaline solution, and then the pretreated micronucleus is added. After thorough stirring, the mixture is filtered and dried to obtain a rigid micronucleus.

[0106] Specifically, 4-6 parts of silane coupling agent are mixed with 80-90 parts of organic solvent and 1 part of alkaline solution, stirred at room temperature for 30 minutes, and then the pretreated micronucleus is added. The mixture is stirred in a water bath at 50°C for 2 hours, filtered and washed, and then dried at 60°C for 24 hours to obtain an interface-enhanced micronucleus, i.e., a rigid micronucleus.

[0107] (2) Preparation of the matrix layer

[0108] In step S200, a matrix layer is prepared according to the working temperature of the composite temporary plugging agent to be prepared, under the corresponding working temperature gradient.

[0109] Since the matrix layer plays a major role in the composite system, it needs to bear 80% of the stress in the formation. The matrix layer corresponding to the composite temporary plugging agent is different at different temperatures.

[0110] Based on the applicable temperature of different composite plugging agents, composite plugging agents can be divided into medium-temperature composite plugging agents ([80℃, 120℃]), medium-high temperature composite plugging agents ((120℃, 160℃]), and ultra-high temperature composite plugging agents ((160℃, 200℃)).

[0111] When the working temperature of the composite temporary plugging agent is [80℃, 120℃], step S200 includes steps S211 to S214.

[0112] In step S211, under nitrogen protection, the first monomer and deionized water are stirred at room temperature until completely dispersed to obtain the first solution.

[0113] In step S212, a dispersant, polymeric monomer II, and comonomer are added sequentially to the first solution, and the mixture is stirred at room temperature until it is completely dispersed to obtain a second solution.

[0114] In step S213, the second solution is degassed under vacuum to obtain a third solution of homogeneous system.

[0115] In step S214, crosslinking agent one, crosslinking agent two, and initiator are added to the third solution, and stirred to dissolve, thereby obtaining the matrix layer.

[0116] Wherein, the first polymeric monomer is κ-type carrageenan, and the mass fraction of the first polymeric monomer is 4-6 parts;

[0117] The first crosslinking agent is potassium chloride, and the mass fraction of the first crosslinking agent is 0.2-0.4 parts;

[0118] Crosslinking agent two is N,N'-methylenebisacrylamide, and the mass fraction of crosslinking agent two is 0.06-0.1.

[0119] The mass fraction of the dispersant is 0.3-0.6 parts;

[0120] The mass fraction of monomer two is 17-24 parts; in some embodiments, monomer two is acrylamide.

[0121] The comonomer is 4-5 parts by mass. In some embodiments, the second polymeric monomer is sodium p-styrene sulfonate.

[0122] The initiator is 0.06-0.12 parts by mass. In some embodiments, the initiator is ammonium persulfate and sodium bisulfite (molar ratio of 1:1).

[0123] When the working temperature of the composite temporary plugging agent is (120℃, 160℃), step S200 includes steps S221 to S224.

[0124] In step S221, under nitrogen protection, the first monomer and deionized water are stirred at room temperature until completely dispersed to obtain the first solution.

[0125] In step S222, a dispersant, polymeric monomer II, and comonomer are added sequentially to the first solution, and the mixture is stirred at room temperature until it is completely dispersed to obtain a second solution.

[0126] In step S223, the second solution is degassed under vacuum to obtain a homogeneous third solution.

[0127] In step S224, crosslinking agent one, crosslinking agent two, and initiator are added to the third solution, and stirred to dissolve, thereby obtaining the matrix layer.

[0128] Wherein, the first polymer is sodium alginate, and the mass fraction of the first polymer monomer is 5-10 parts;

[0129] The crosslinking agent is glucono-δ-lactone and calcium disodium ethylenediaminetetraacetate, and the molar ratio of glucono-δ-lactone to calcium disodium ethylenediaminetetraacetate is 1:2.

[0130] Crosslinking agent two is N'N-methylenebisacrylamide, and the mass fraction of crosslinking agent two is 0.2-0.3 parts;

[0131] The mass fraction of the dispersant is 0.3-0.6 parts;

[0132] The mass fraction of monomer two is 17-24 parts; in some embodiments, monomer two is acrylamide.

[0133] The comonomer is 4-5 parts by mass. In some embodiments, the second polymeric monomer is sodium p-styrene sulfonate.

[0134] The initiator is 0.06-0.12 parts by mass. In some embodiments, the initiator is potassium persulfate and sodium bisulfite (molar ratio of 1:1).

[0135] When the working temperature of the composite temporary plugging agent is (160℃, 200℃), step S200 includes steps S231 to S234.

[0136] In step S231, under nitrogen protection, the first monomer and deionized water are stirred at room temperature until completely dispersed to obtain the first solution.

[0137] In step S232, a dispersant, polymeric monomer II, comonomer, and modified nano-blended material are added sequentially to the first solution, and stirred at room temperature until completely dispersed to obtain a second solution.

[0138] In step S233, the second solution is degassed under vacuum to obtain a homogeneous third solution;

[0139] In step S234, crosslinking agent II and initiator are added to the third solution, stirred and dissolved to obtain the matrix layer;

[0140] Wherein, the first polymer is a gelatin, and the first polymer monomer has a mass fraction of 5-10 parts;

[0141] Crosslinking agent two is N'N-methylenebisacrylamide, and the mass fraction of crosslinking agent two is 0.2-0.3 parts;

[0142] The mass fraction of the dispersant is 0.3-0.6 parts;

[0143] The mass fraction of monomer two is 17-24 parts; in some embodiments, monomer two is acrylamide.

[0144] The comonomer is 4-5 parts by mass. In some embodiments, the second polymeric monomer is sodium p-styrene sulfonate.

[0145] The initiator is 0.06-0.12 parts by mass. In some embodiments, the initiator is potassium persulfate and sodium bisulfite (molar ratio of 1:1).

[0146] In some embodiments, the modified nanoblended material is nano-lithium saponin clay, in parts by weight of 6.

[0147] Modified nano-blended materials (such as nano-lithium saponin) were added to the ultra-high temperature composite temporary plugging agent, which effectively increased the stiffness and hardness of the matrix system and also endowed the system with excellent elasticity and toughness. Only one crosslinking agent, crosslinking agent II, was added to the ultra-high temperature composite temporary plugging agent, without the addition of crosslinking agent I, because kerogen can form a crosslinked network through thermal induction without the need for additional chemical crosslinking agents.

[0148] (3) The matrix layer is blended with the rigid microcore.

[0149] To improve strength and control density, a core blending process is employed, combining silica sand and glass microspheres in a specific ratio to form the core. The blended core material undergoes surface modification treatment to enhance its interfacial bonding with the subsequent matrix layer. This treatment comprises two steps: alkaline solution activation and silane coupling agent grafting. The particle size range and total amount of the core are controlled to avoid stress concentration and agglomeration, and to ensure the continuity of the matrix layer.

[0150] In step S310, the prepared matrix layer is blended with the rigid microcore to obtain a hybrid material.

[0151] In step S320, the prepared mixed material is heated to allow polymer monomer one and polymer monomer two in the mixed material to undergo cross-linking reactions to form a double network gel.

[0152] Specifically, the prepared mixed material is transferred to a 60°C oven for 12 hours to allow polymer monomer one and polymer monomer two in the mixed material to undergo cross-linking reactions, forming a double-network gel.

[0153] In this process, monomer one undergoes a cross-linking reaction to form a first network gel. Monomer two undergoes a cross-linking reaction to form a second network gel.

[0154] In step S330, the obtained double-network gel is cut into pieces, dried, granulated and sieved to obtain matrix particles.

[0155] Specifically, the obtained double-network gel was cut into blocks, dried at 80°C for 12 h, and then granulated and sieved to obtain matrix particles.

[0156] (4) Preparation of surface-modified temporary plugging agent particles (surface modification treatment)

[0157] Surface treatment of the matrix particles improves their migration properties in fracturing fluid. A specific organosilicon modification solution is prepared. The prepared matrix particles are immersed in this modification solution and stirred at a constant temperature for a certain period of time to ensure that the particle surface is uniformly coated. Excess solution is removed. The coated particles are then subjected to a gradient temperature curing treatment to form a dense protective layer on the particle surface.

[0158] In step S410, tetraethyl orthosilicate, dimethyl silicone oil and deionized water are mixed and stirred to form a uniform and viscous modified liquid. The ratio of tetraethyl orthosilicate, dimethyl silicone oil and deionized water is determined according to the working temperature of the composite temporary plugging agent to be prepared.

[0159] It should be noted that the modified liquids corresponding to the three composite temporary plugging agents at different working temperatures are different: medium-temperature composite temporary plugging agent ([80℃, 120℃]), medium-high temperature composite temporary plugging agent ((120℃, 160℃]), and ultra-high temperature composite temporary plugging agent ((160℃, 200℃]).

[0160] When the working temperature of the composite temporary plugging agent is [80℃, 120℃], the mass fractions of the tetraethyl orthosilicate and the dimethyl silicone oil are 3 parts and 3 parts, respectively.

[0161] When the working temperature of the composite temporary plugging agent is (120℃, 160℃), the mass fractions of the tetraethyl orthosilicate and the dimethyl silicone oil are 5 parts and 5 parts, respectively.

[0162] When the working temperature of the composite temporary plugging agent is (160℃, 200℃), the mass fractions of the tetraethyl orthosilicate and the dimethyl silicone oil are 7 parts and 7 parts, respectively.

[0163] Specifically, based on the working temperature of the composite temporary plugging agent to be prepared, take the corresponding mass fractions of tetraethyl orthosilicate and the dimethyl silicone oil, and stir at room temperature to form a uniform viscous modified liquid.

[0164] In step S420, the modified liquid obtained is added to the matrix particles at room temperature, stirred evenly at a constant temperature, allowed to settle, the liquid is removed, and the settled particles are transferred to a container coated with a release agent and cured to obtain surface-modified temporary plugging agent particles.

[0165] More specifically, the modified liquid is slowly added to the matrix particles at room temperature, stirred at a constant temperature for 1 hour, and then allowed to stand for 15 minutes to allow the particles to settle. The modified liquid is then removed, and the settled particles are transferred to a container coated with a release agent. The particles are initially cured at 60°C for 4 hours and then finally cured at 80°C for 8 hours to obtain surface-modified temporary plugging agent particles.

[0166] To facilitate verification of the performance of the composite temporary plugging agent provided by the present invention, the prepared composite temporary plugging agent was subjected to surface modification test, expansion performance test, degradation performance test, gel mechanical property test, and plugging performance test.

[0167] Example 1

[0168] Example 1 is a modified composite temporary plugging agent matrix of 40-70 mesh.

[0169] S1, 3g of silica sand and 9g of glass microspheres are compounded to form a microcore. The obtained microcore is added to 2g of alkaline solution (0.04g of sodium hydroxide and 1.96g of water) and stirred evenly for pretreatment to obtain the pretreated microcore.

[0170] S2, after mixing the silane coupling agent (5g silane coupling agent KH-550) with the mixture of organic solvent (85 ml) and alkaline solution (1.5 ml), add the pretreated microcore, stir thoroughly, filter, and dry to obtain rigid microcore;

[0171] S3 includes:

[0172] Under nitrogen protection, monomer 1 (4g of κ-type carrageenan) was stirred with 220 ml of deionized water at room temperature until completely dispersed to obtain the first solution;

[0173] Dispersant (0.4 g sodium pyrophosphate), polymeric monomer II (19.2 g acrylamide), and comonomer (4.8 g sodium p-styrene sulfonate) were added sequentially to the first solution, and stirred at room temperature until completely dispersed to obtain the second solution;

[0174] The second solution is subjected to vacuum degassing to obtain a homogeneous third solution;

[0175] Add crosslinking agent one (0.24 g potassium chloride), crosslinking agent two (0.072 g N'N-methylenebisacrylamide), and initiator (0.06 g potassium persulfate) to the third solution, stir to dissolve, and obtain the matrix layer;

[0176] Wherein, the first polymeric monomer is κ-type carrageenan, and the mass of the first polymeric monomer is 4g;

[0177] The first crosslinking agent is potassium chloride, and the mass of the first crosslinking agent is 0.24 g;

[0178] Crosslinking agent two is N,N'-methylenebisacrylamide, and the mass of crosslinking agent two is 0.072 g;

[0179] S4, the prepared matrix layer is blended with the rigid microcore to obtain a hybrid material;

[0180] S5, the prepared mixed material is heated to raise the temperature, so that polymeric monomer one and polymeric monomer two in the mixed material undergo cross-linking reactions to form a double network gel;

[0181] S6. The obtained double network gel is cut into pieces, dried, granulated and sieved to obtain matrix particles.

[0182] S7, Tetraethyl orthosilicate, dimethyl silicone oil and deionized water are mixed and stirred to form a uniform and viscous modified liquid, wherein the ratio of tetraethyl orthosilicate, dimethyl silicone oil and deionized water is determined according to the working temperature of the composite temporary plugging agent to be prepared.

[0183] S8. The obtained modified liquid is added to the matrix particles at room temperature, stirred evenly at a constant temperature, allowed to stand to allow the particles to settle, the liquid is removed, and the settled particles are transferred to a container coated with a release agent and cured to obtain surface-modified temporary plugging agent particles.

[0184] Example 2 is a medium-temperature composite temporary plugging agent with a mesh size of 40-70.

[0185] Unlike Example 1, S3 includes:

[0186] Under nitrogen protection, monomer 1 (4g of κ-type carrageenan) was stirred with 220 ml of deionized water at room temperature until completely dispersed to obtain the first solution;

[0187] Dispersant (0.45 g sodium pyrophosphate), polymeric monomer II (20.5 g acrylamide), and comonomer (4.5 g sodium p-styrene sulfonate) were added sequentially to the first solution, and stirred at room temperature until completely dispersed to obtain the second solution;

[0188] The second solution is subjected to vacuum degassing to obtain a homogeneous third solution;

[0189] Add crosslinking agent one (0.3 g potassium chloride), crosslinking agent two (0.18 g N'N-methylenebisacrylamide), and initiator (0.09 g potassium persulfate) to the third solution, stir to dissolve, and obtain the matrix layer;

[0190] Wherein, the first polymeric monomer is κ-type carrageenan, and the mass of the first polymeric monomer is 4g;

[0191] The first crosslinking agent is potassium chloride, and the mass of the first crosslinking agent is 0.3 g;

[0192] Crosslinking agent two is N,N'-methylenebisacrylamide, and the mass of crosslinking agent two is 0.18g.

[0193] Example 3 is a medium-high temperature composite temporary plugging agent with a mesh size of 40-70.

[0194] Unlike Example 1, S3 includes:

[0195] Under nitrogen protection, monomer 1 (4 g sodium alginate) and deionized water (69.138 ml) were stirred at room temperature until completely dispersed to obtain the first solution;

[0196] Dispersant (0.45 g sodium pyrophosphate), polymeric monomer 2 (20.5 g acrylamide), and comonomer (4.5 g sodium p-styrene sulfonate) were added sequentially to the first solution, and stirred at room temperature until completely dispersed to obtain the second solution;

[0197] The second solution is subjected to vacuum degassing to obtain a homogeneous third solution;

[0198] Add crosslinking agent one (0.36 g gluconate-δ-lactone and 0.34 g disodium calcium ethylenediaminetetraacetate), crosslinking agent two (0.18 g N'N-methylenebisacrylamide), and initiator (0.09 g potassium persulfate) to the third solution, stir to dissolve, and obtain the matrix layer;

[0199] Wherein, the first polymer is sodium alginate, and the mass of the first polymer monomer is 4 g;

[0200] The crosslinking agent is gluconate-δ-lactone and calcium disodium ethylenediaminetetraacetate, wherein the molar ratio of gluconate-δ-lactone and calcium disodium ethylenediaminetetraacetate is 1:2, and their masses are 0.36 g and 0.34 g, respectively.

[0201] Crosslinking agent two is N'N-methylenebisacrylamide, and the mass of crosslinking agent two is 0.18g.

[0202] Example 4 is an ultra-high temperature composite temporary plugging agent with a mesh size of 40-70.

[0203] Unlike Example 1, S3 includes:

[0204] Under nitrogen protection, monomer 1 (4 g gellan gum) and deionized water (66.504 mL) were stirred at room temperature until completely dispersed to obtain the first solution;

[0205] Dispersant (0.45 g sodium pyrophosphate), polymeric monomer II (20.5 g acrylamide), comonomer (4.5 g sodium p-styrene sulfonate), and modified nano-blended material (4.5 g nano lithium saponite) were added sequentially to the first solution and stirred at room temperature until completely dispersed to obtain the second solution.

[0206] The second solution is subjected to vacuum degassing to obtain a homogeneous third solution;

[0207] Add crosslinking agent II (0.18 g N'N-methylenebisacrylamide) and initiator (0.09 g potassium persulfate) to the third solution, stir to dissolve, and obtain the matrix layer;

[0208] Wherein, the first polymer is a gellan gum, and the mass of the first polymer monomer is 4 g.

[0209] Crosslinking agent two is N'N-methylenebisacrylamide, and the mass of crosslinking agent two is 0.18g.

[0210] Comparative Example 1

[0211] Unmodified temporary plugging agent matrix, 40-70 mesh.

[0212] Comparative Example 2

[0213] Conventional rigid temporary plugging agent for oil fields, 20-40 mesh.

[0214] Comparative Example 3

[0215] Ordinary expanding gel temporary plugging agent, 40-70 mesh.

[0216] Experiment 1: Surface Modification Test

[0217] Take 0.1 g of the composite temporary plugging agent matrix sample before and after modification and mix it with an excess of carrier liquid (0.5 wt% guar gum solution, 50 mPa·s). Example 1 uses the modified composite temporary plugging agent matrix (40-70 mesh); Comparative Example 1 uses the unmodified temporary plugging agent matrix (40-70 mesh). Place both samples in a pressure-resistant test tube and expand them at 120°C until the particles reach expansion equilibrium (i.e., no change in mass). Remove the particles at different time stages and remove excess water using a vacuum filtration flask. Record and calculate the mass expansion factor of the matrix layer samples before and after modification. The initial failure time of the modified protective layer is defined as the first increase in the sample mass expansion factor, and the complete failure time is defined as the first significant increase in the sample mass expansion factor.

[0218] Analysis based on the principles of surface modification and the test results of the expansion performance of modified particles at different temperatures (e.g.) Figure 1 The thermal degradation process of the modified protective layer can be divided into four stages: (1) Stable stage I: At this time, the modified protective layer network is intact, the hydrophobic properties are good, the water absorption of the modified particles is significantly delayed, and the water absorption rate is low; (2) Relaxation stage II: At this time, the modified protective layer network relaxes under temperature conditions, and small cracks may also appear, resulting in a small amount of liquid contacting the internal matrix particles, and the expansion ratio of the modified particles begins to increase; (3) Degradation stage III: The modified protective layer network begins to undergo severe degradation, the internal matrix particles begin to contact the carrying liquid over a large area, and the expansion ratio of the modified particles rises rapidly; (4) Failure stage IV: The protective layer completely fails, the hydrophobic properties are lost, and the modified particles reach a balanced expansion state.

[0219] like Figure 2 As shown, before modification: Comparative Example 1 had a faster expansion rate in 0–40 min, rapidly absorbed water in a short time, and reached expansion equilibrium after about 60 min.

[0220] After modification: The expansion curve of Example 1 showed a significantly gentler slope, a significantly reduced expansion rate, and an increased time (120 min) required to reach expansion equilibrium. Furthermore, compared to the unmodified system, the expansion ratio was slightly reduced after modification. The reduced expansion rate allows particles to remain smaller in the high-temperature fracturing fluid for a longer period, facilitating their migration deeper into the fracture with the fluid flow (avoiding premature expansion and blockage of the near-wellbore zone). Controlling the expansion ratio prevents strength degradation caused by excessive expansion of the polymer network.

[0221] Experiment 2: Expansion Performance Test

[0222] A certain mass (M0) of the prepared temporary plugging agent matrix layer sample (dried to constant weight) was mixed with an excess of carrying liquid (0.5 wt% guar gum solution, 50 mPa·s). Among them, Example 2 was a medium-temperature composite temporary plugging agent of 40-70 mesh, Example 3 was a medium-high temperature composite temporary plugging agent of 40-70 mesh, Example 4 was an ultra-high temperature composite temporary plugging agent of 40-70 mesh; Comparative Example 2 was a conventional rigid temporary plugging agent for oil fields of 20-40 mesh; and Comparative Example 3 was a common expanding gel temporary plugging agent of 40-70 mesh. The sample was placed in a high-temperature and high-pressure reactor and expanded at different temperatures (25℃, 120℃, 140℃, 160℃, 180℃, 200℃) until it reached expansion equilibrium (i.e., the mass did not change). The sample was removed at different time stages (10min, 20min, 30min, 40min, 50min, 60min) at the same temperature (60℃) and excess water was removed by vacuum filtration. The sample mass (M1) was recorded and the expansion factor of the temporary plugging agent was calculated as n = (M1-M0) / M0.

[0223] As shown in Table 1, based on the experimental results of the expansion ratio of the temporary plugging agent at different times at the same temperature (60℃), it can be concluded that: Examples 2-4: rapid expansion equilibrium was reached within 30–40 min at 60℃ (equilibrium ratio: 21.9–28), indicating that the surface modification layer effectively inhibited the water penetration rate and avoided early excessive swelling. Comparative Example 2 (rigid particles): the expansion ratio was always 0, verifying its non-expansion characteristics dependent on physical bridging. Comparative Example 3 (ordinary gel): the expansion continued to increase to 49.2 (far exceeding the modified group), highlighting the risk of uncontrolled swelling in the unmodified material. Based on the experimental results of the expansion ratio of temporary plugging agents at different temperatures over the same time period (1 hour), the following conclusions can be drawn: Example 2 is a medium-temperature composite temporary plugging agent, applicable to temperatures <140℃. At 140℃, it expands by 50%. At temperatures >160℃, due to excessively high temperatures, the protective layer partially fails, leading to degradation of the temporary plugging agent matrix network caused by high-temperature damage, and the expansion ratio drops sharply to 14.1%. Example 3 is a medium-high temperature composite temporary plugging agent, applicable to temperatures <180℃. At 180℃, it still maintains an effective expansion rate of 36.26%. The surface layer and the dual-network matrix work together to resist high temperatures and inhibit excessive swelling. Example 4 is an ultra-high temperature composite temporary plugging agent, which can still maintain structural integrity at 200℃. Because the dense protective layer can inhibit high-temperature swelling, the expansion ratio is reduced, while also blocking thermal degradation.

[0224] Table 1. Experimental results of expansion ratio of temporary plugging agent at different times at the same temperature (60℃)

[0225] Time / min 10 20 30 40 50 60 Example 2 18.9 22.5 27.8 28 28 28 Example 3 17.4 19.6 22 22.8 22.8 22.8 Example 4 12.5 16.4 20.5 21.9 21.9 21.9 Comparative Example 2 0 0 0 0 0 0 Comparative Example 3 33.6 37.1 49.2 49.2 49.2 49.2

[0226] Table 2. Experimental results of expansion ratio of temporary plugging agent at different temperatures during the same time period (1 hour).

[0227] Experimental temperature / ℃ 25 120 140 160 180 200 Example 2 34.7 42.5 50 14.1 - - Example 3 22.52 27.36 28.95 30.69 36.26 11.84 Example 4 13.95 22.5 24.3 27.1 25.2 25.85 Comparative Example 2 0 0 0 0 0 0 Comparative Example 3 12.8 42.2 - - - -

[0228] Note: "-" indicates that the temporary plugging agent has lost its solid form and its expansion ratio is difficult to measure.

[0229] Experiment 3: Degradation Performance Test

[0230] A certain mass of the temporary plugging agent matrix layer sample (M0) was placed in a high-temperature and high-pressure reactor and immersed in a fixed volume of water. Example 2 was a medium-temperature composite temporary plugging agent, Example 3 was a medium-high temperature composite temporary plugging agent, and Example 4 was an ultra-high temperature composite temporary plugging agent; Comparative Example 2 was a conventional rigid temporary plugging agent used in oilfields; and Comparative Example 3 was a common expanding gel temporary plugging agent. Degradation rate experiments were conducted at the same temperature (160℃) for different times, and degradation performance experiments were conducted at the same time (4h, 8h) for different temperatures. The particles were removed, excess water was removed using a vacuum filtration flask, and then dried in an 80℃ oven to constant weight. The mass of the dried sample (M1) was measured, and the degradation rate of the temporary plugging agent (η) was calculated. η = (M1 - M0) / M0 × 100%.

[0231] The experimental results are shown in Tables 3 and 4 below: Example 2 is a medium-temperature composite temporary plugging agent, which achieved a degradation rate of 33.4% at 160℃ for 4 hours and rapidly and completely degraded within 6-8 hours, demonstrating controllable time-dependent effectiveness and meeting the requirement for automatic release after temporary plugging in medium-temperature reservoirs. Example 3 is a medium-high temperature composite temporary plugging agent, which degraded by 79.9% at 160℃ for 8 hours, ensuring effective plugging during deep well fracturing cycles; complete degradation at 200℃ for 8 hours demonstrates high-temperature reliability. Example 4 is an ultra-high temperature composite temporary plugging agent, with a degradation rate of only 53.07% at 160℃ for 8 hours and 87.9% at 200℃ for 8 hours, exhibiting the best high-temperature tolerance and confirming the excellent tolerance of its tight protective layer to ultra-high temperature environments. Comparative Example 2 is a rigid particle, with the lowest degradation rate, incomplete degradation, high residual risk, and significant formation damage. Comparative Example 3 is a common gel temporary plugging agent, which degraded by 73.7% at 160℃ for 4 hours, but premature degradation could easily lead to plugging failure. It degrades instantly and completely at temperatures above 180℃, losing its temporary blocking function and stability.

[0232] Table 3. Experimental results of degradation rate of the temporary plugging agent matrix layer system at different times at the same temperature (160℃).

[0233] Time / h 2 4 6 8 10 Example 2 17.6 33.4 63.1 100 100 Example 3 9.2 16.5 45.2 79.9 100 Example 4 2.5 7.8 28.4 53.07 81.2 Comparative Example 2 0 6.8 11.8 16.5 23.6 Comparative Example 3 43.6 73.7 100 100 100

[0234] Table 4. Degradation performance of the temporary plugging agent matrix layer system at different temperatures over the same time (4h, 8h).

[0235] 160℃，4h 160℃，8h 180℃，4h 180℃，8h 200℃，4h 200℃，8h Example 2 33.4 100 100 100 100 100 Example 3 16.5 79.9 20.1 100 50.8 100 Example 4 7.8 53.07 33.6 70.2 38.5 87.9 Comparative Example 2 3.7 16.5 16.7 34.7 28.5 46.3 Comparative Example 3 73.7 100 100 100 100 100

[0236] Example 4: Mechanical properties of gel state

[0237] The mechanical property testing of the temporary plugging agent matrix layer system was divided into two parts: gel-state mechanical properties and particulate-state mechanical properties. Peak strain, compressive strength, and toughness were obtained through compression experiments on gel-state samples to characterize their mechanical properties. The tested gel-state samples were cylindrical with dimensions of Φ10 mm × 20 mm, and the compression rate was 10 mm·min. -1 Example 2 is a medium-temperature composite temporary plugging agent, Example 3 is a medium-high temperature composite temporary plugging agent, and Example 4 is a high temperature composite temporary plugging agent; Comparative Example 3 is a common expanding gel temporary plugging agent.

[0238] The experimental results are shown in Table 5 below. It can be concluded that the mechanical properties of the composite gel particle plugging agents in Examples 2-4 are significantly improved compared to the ordinary gel plugging agent in Comparative Example 3. In terms of compressive strength, Example 4 (ultra-high temperature type) has a strength of 15.8 MPa, a 129% increase compared to Comparative Example 3 (6.89 MPa); Example 3 (medium-high temperature type) reaches 13.4 MPa (a 94% increase); and Example 2 (medium temperature type) reaches 10.89 MPa (a 58% increase). This gradient increase confirms the positive correlation between temperature resistance and mechanical strength. Regarding elastic modulus, as the temperature resistance level increases, the modulus of Example 4 decreases to 1.76 MPa, still higher than the 0.63 MPa of Comparative Example 3, indicating that the ultra-high temperature type balances pressure requirements and crack compatibility through its "soft exterior, rigid interior" structure. The low-modulus outer shell alleviates stress concentration and avoids brittle fracture; the high-strength inner core resists formation closure pressure, completely solving the bridging failure problem caused by excessive softness in traditional gel plugging agents. In terms of toughness, Example 4 achieved a toughness value of 3.57 MJ·m. -3 Compared with Comparative Example 3, the increase was 449%, and Examples 3 and 2 also reached 2.43 MJ·m⁻¹. -3 (Increased by 274%) and 1.46 MJ·m -3 (Increased by 124%). This "strong and tough synergy" stems from the combined effect of the microcore and the protective layer. The microcore provides rigid support, while the gradient cross-linked protective layer absorbs energy through elastic deformation, giving the material both high compressive strength and damage resistance.

[0239] Table 5. Experimental Analysis of Compression Performance of Different Temporary Plugging Agent Matrix Systems

[0240] Maximum compressive strain / % Compressive strength / MPa Elastic modulus / MPa <![CDATA[Toughness / MJ·m -3 > Example 2 100 10.89 2.22 1.46 Example 3 100 13.4 2.02 2.43 Example 4 100 15.8 1.76 3.57 Comparative Example 3 100 6.89 0.63 0.65

[0241] The mechanical properties of particulate temporary plugging agents were characterized by obtaining their storage modulus and elastic modulus in the swollen state through rheological testing experiments. Example 2 was a medium-temperature composite temporary plugging agent, Example 3 was a medium-high temperature composite temporary plugging agent, and Example 4 was a high-temperature composite temporary plugging agent; Comparative Example 3 was a common expanding gel temporary plugging agent; the particle size of all samples was 20-40 mesh. Tests were conducted at 25°C using a Discovery HR-1 stress-controlled rheometer from XX Company. The test mode was variable shear strain (0-100%), and the frequency was 1 Hz. 0.1 g of the prepared temporary plugging agent matrix particulate sample was taken, and before the experiment, the particulate sample was mixed with an excess of guar gum carrying solution at room temperature for 30 min before testing.

[0242] Experimental results show that: Figure 4As shown, all the temporary plugging agents in the swollen state exhibited an "elastic-dominated" characteristic (storage modulus G' > loss modulus G''), confirming that the microcore and gradient protective layer synergistically constructed a stable composite gel temporary plugging agent network structure. Among them, the elastic modulus G' of Example 4 (high-temperature composite type) reached 34,632 Pa, which is 3.14 times that of Comparative Example 3 (11028 Pa). Examples 3 and 4 also improved the elastic modulus to a certain extent, proving that their three-dimensional network structure can withstand higher stress. At room temperature, the storage modulus showed the following order: Example 4 > Example 3 > Example 2 > Comparative Example 3. This gradient is positively correlated with the crosslinking density of the protective layer.

[0243] Example 5: Blocking Performance Test

[0244] To determine the sealing strength of the formed plugging layer, temporary plugging agent particles were injected into simulated rock cores with fractures. The highest plugging pressure and the time to reach the highest plugging pressure were used as evaluation indicators. Example 2 used a medium-temperature composite temporary plugging agent (40-70 mesh), Example 3 used a medium-high temperature composite temporary plugging agent (40-70 mesh), and Example 4 used a high temperature composite temporary plugging agent (40-70 mesh). Comparative Example 2 used a conventional rigid temporary plugging agent from the oilfield (20-40 mesh), and Comparative Example 3 used a common intumescent gel temporary plugging agent (40-70 mesh). Before the experiment, the particles were fully swollen at 90℃. The particle size of all samples was uniformly matched to the fracture width according to the "one-third" principle, i.e., the swollen particle size was close to 0.66 mm. The simulated rock core length was 30 cm, the fracture width was 2 mm, the discharge rate was 50 ml / min, and the temporary plugging agent concentration was 0.5% g / mL.

[0245] The experimental results are shown in Table 6. The time to reach the maximum sealing pressure reflects the ease with which the particles form a bridging seal, while the maximum sealing pressure reflects the quality of the temporary plugging agent's sealing performance. Comparative Example 2, due to the low sealing strength of rigid particles of a single particle size, is prone to instability and sealing failure. Comparative Example 3, due to its low strength, leads to bridging failure and fails to form pressure. Example 4 (ultra-high temperature type) achieved a maximum sealing pressure of 21.8 MPa, a 69% increase compared to Example 2 (medium temperature type, 12.9 MPa). Example 3 (medium-high temperature type) withstood a pressure of 19.0 MPa, confirming the positive relationship between temperature resistance and sealing strength (high temperature enhances structural stability). Example 3 only required 439 seconds to reach peak pressure, demonstrating its rapid bridging capability.

[0246] Table 6. Blocking performance test results

[0247] Maximum sealing pressure / MPa Time to reach maximum sealing pressure / s Example 2 12.9 1527 Example 3 19.0 1128 Example 4 21.8 439 Comparative Example 2 Rigid particles of a single size have low plugging strength and are prone to instability. - Comparative Example 3 Insufficient strength resulted in no pressure buildup. -

[0248] Figure 11 and Figure 12The diagram shows the infrared spectra of each product. This invention preferably uses κ-CG / P (AM-co-SSS), SA / P (AM-co-SSS), and Cur. / P (AM-co-SSS) / Laponite. For example... Figure 11 As shown,

[0249] All samples contained the following characteristic peak: 2933 cm⁻¹ -1 (Stretching vibration of -CH2- in the carbon chain), 1652 cm⁻¹ -1 (Stretching vibration of the -C=O- band of the AM amide group I), 1545 cm⁻¹ -1 (The bending vibration of the -C=O-NH2- band of the AM amide group II, 1452 cm⁻¹) -1 (Skeleton symmetric stretching vibration peak of -C=C- in the SSS benzene ring), 1180 cm⁻¹ -1 (The symmetric stretching vibration peak of the benzene-substituted group in SSS: sulfonic acid group -SO3- shifts to lower frequencies), these five characteristic peaks indicate that a second network of AM chemical cross-linking was formed in each gel sample system, and that AM and SSS copolymerization occurred in the network.

[0250] Figure 12 In comparison with the single-network gel system P(AM-co-SSS) and the nanocomposite single-network gel system P(AM-co-SSS) / Laponite, as well as various nanocomposite-reinforced double-network gel systems, a distinct characteristic absorption peak of Laponite can be observed: 995-1000 cm⁻¹. −1 (Stretching vibrations of Si−O), 410-430 cm⁻¹ −1 (The bending vibration of Si−O), and compared to the stretching vibration (1008 cm–1) and bending vibration (461 cm) of Laponite itself. -1 The characteristic peaks of the system all shifted to lower frequencies, indicating that Laponite in the system is not simply blended with the polymer matrix. There is an interaction between the P(AM-co-SSS) polymer chain and Laponite, resulting in characteristic absorption. That is, Laponite, to a certain extent, acts as a physical crosslinking site in the system, increasing the crosslinking density.

[0251] Figures 13 to 17 Based on SEM scanning results, structural analysis was performed on the matrix layer systems of different first-network gels. The single-network P (AM-co-SSS) system ( Figure 13 The polymer chains form a mesh-like structure, which is relatively uniform overall, with small pores dispersed throughout the structure; the double network κ-CG / P(AM-co-SSS) ( Figure 14 SA / P (AM-co-SSS) Figure 15 ) and Cur. / P (AM-co-SSS) ( Figure 16 The Cur. / P (AM-co-SSS) system forms a more complex network structure, with a denser structure, more prominent intertwined and interconnected structures, and exhibits greater diversity in network structure, even showing contrasts between regions of different densities, reflecting the differences in the dual network structure. In contrast, the Cur. / P (AM-co-SSS) system... Figure 16 The network formed is more regular and has no obvious pores; the nanocomposite dual network Cur. / P(AM-co-SSS) / Laponite system ( Figure 17 The composite temporary plugging agent exhibits a denser network structure. The addition of nano-Laponite adds "peak"-like protrusions to the original "groove and stripe" veins of the double network, and this multidimensional structure can increase the strength of the polymer network structure. The addition of nano-Laponite also affects the porosity of the matrix layer system, resulting in a significant reduction in the size and number of pores. This further verifies the advantages of the preparation method of the composite temporary plugging agent provided by this invention.

[0252] Obviously, the embodiments described above are merely some, not all, embodiments of the present invention. Based on the embodiments of the present invention, those skilled in the art can make other variations or modifications without creative effort, and all such variations or modifications should fall within the scope of protection of the present invention.

Claims

1. A method for preparing a composite temporary plugging agent suitable for different temperature gradients, characterized in that, include: Silica sand and glass microspheres are combined to form a microcore, and the obtained microcore is added to an alkaline solution and stirred evenly for pretreatment; After mixing the silane coupling agent with a mixture of organic solvent and alkaline solution, the pretreated micronuclei are added, stirred thoroughly, filtered, and dried to obtain rigid micronuclei. Based on the working temperature of the composite temporary plugging agent to be prepared, prepare a matrix layer corresponding to the working temperature gradient; The prepared matrix layer is blended with the rigid microcore to obtain a hybrid material; The prepared mixed material is heated to cause polymer monomer one and polymer monomer two in the mixed material to undergo cross-linking reactions respectively, forming a double network gel. The obtained double-network gel was cut into blocks, dried, granulated and sieved to obtain matrix particles. Tetraethyl orthosilicate, dimethyl silicone oil and deionized water are mixed and stirred to form a uniform and viscous modified liquid. The ratio of tetraethyl orthosilicate, dimethyl silicone oil and deionized water is determined according to the working temperature of the composite temporary plugging agent to be prepared. The obtained modified liquid was added to the matrix particles at room temperature, stirred evenly at a constant temperature, allowed to stand to allow the particles to settle, the liquid was removed, and the settled particles were transferred to a container coated with a release agent and cured to obtain surface-modified temporary plugging agent particles. Wherein, when the working temperature of the composite plugging agent is [80℃, 120℃]; correspondingly, the step of preparing a matrix layer under the corresponding working temperature gradient according to the working temperature of the composite plugging agent to be prepared includes: Under nitrogen protection, monomer one was stirred with deionized water at room temperature until completely dispersed to obtain the first solution; Add dispersant, polymeric monomer II, and comonomer sequentially to the first solution, and stir at room temperature until completely dispersed to obtain the second solution; The second solution is subjected to vacuum degassing to obtain a homogeneous third solution; Add crosslinking agent one, crosslinking agent two, and initiator to the third solution, stir to dissolve, and obtain the matrix layer; The polymerization monomer one is Type carrageenan, and the mass fraction of the polymerization monomer one is 4-6 parts. The first crosslinking agent is potassium chloride, and the mass fraction of the first crosslinking agent is 0.2-0.

4. Crosslinking agent two is N,N'-methylenebisacrylamide, and the mass fraction of crosslinking agent two is 0.06-0.

1. When the operating temperature of the composite plugging agent is (120℃, 160℃); correspondingly, the step of preparing a matrix layer under the corresponding operating temperature gradient according to the operating temperature of the composite plugging agent to be prepared includes: Under nitrogen protection, monomer one was stirred with deionized water at room temperature until completely dispersed to obtain the first solution; Add dispersant, polymeric monomer II, and comonomer sequentially to the first solution, and stir at room temperature until completely dispersed to obtain the second solution; The second solution is subjected to vacuum degassing to obtain a homogeneous third solution; Add crosslinking agent one, crosslinking agent two, and initiator to the third solution, stir to dissolve, and obtain the matrix layer; Wherein, the first polymeric monomer is sodium alginate, and the mass fraction of the first polymeric monomer is 5-10 parts; The crosslinking agent is glucono-δ-lactone and calcium disodium ethylenediaminetetraacetate, and the molar ratio of glucono-δ-lactone to calcium disodium ethylenediaminetetraacetate is 1:

2. Crosslinking agent two is N'N-methylenebisacrylamide, and the mass fraction of crosslinking agent two is 0.2-0.3; When the operating temperature of the composite plugging agent is (160℃, 200℃); correspondingly, the step of preparing a matrix layer under the corresponding operating temperature gradient according to the operating temperature of the composite plugging agent to be prepared includes: Under nitrogen protection, monomer one was stirred with deionized water at room temperature until completely dispersed to obtain the first solution; A dispersant, polymeric monomer II, comonomer, and modified nano-blended material are added sequentially to the first solution, and stirred at room temperature until completely dispersed to obtain a second solution. The second solution is subjected to vacuum degassing to obtain a homogeneous third solution; Add crosslinking agent II and initiator to the third solution, stir to dissolve, and obtain the matrix layer; Wherein, the first polymeric monomer is guar gum, and the mass fraction of the first polymeric monomer is 5-10 parts; Crosslinking agent two is N'N-methylenebisacrylamide, and the mass fraction of crosslinking agent two is 0.2-0.3; The modified nano-blended material has a mass fraction of 3-6 parts; the modified nano-blended material is a nanomaterial obtained by modifying the surface and edges of nano-lithium saponite with sodium pyrophosphate; The raw materials used in the preparation method are in the following proportions by mass: Silica sand: 2-4 parts; Glass microspheres: 8-10 parts; Alkaline solution: 1-3 parts; Silane coupling agent: 4-6 parts; Organic solvent: 80-90 parts; Monomer II: 17-24 parts; Comonomer: 4-5 parts; Initiator: 0.06-0.12 parts; Dispersant: 0.3-0.6 parts; The viscosity-modifying liquid is 20-25 parts; The viscous modified liquid contains 3-7 parts of tetraethyl orthosilicate and 3-7 parts of dimethyl silicone oil. The alkaline solution is sodium hydroxide or ammonia solution, with a concentration of 2 wt% when the alkaline solution is sodium hydroxide solution and a concentration of 25 wt% when the alkaline solution is ammonia solution. The organic solvent is ethanol with a concentration of 85 wt%. The dispersant is one or more of sodium citrate, sodium metasilicate, and sodium pyrophosphate. The polymer monomer 2 is acrylamide; The comonomer is sodium p-styrene sulfonate; The initiator is two of the following: ammonium persulfate, potassium persulfate, and sodium bisulfite, and the molar ratio of the two substances in the initiator is 1:

1.

2. The preparation method of the composite temporary plugging agent as described in claim 1, characterized in that, In the step of mixing tetraethyl orthosilicate, dimethyl silicone oil, and deionized water and stirring to form a uniform viscous modified liquid, When the working temperature of the composite temporary plugging agent is [80℃, 120℃], the mass fractions of the tetraethyl orthosilicate and the dimethyl silicone oil are 3 parts and 3 parts, respectively.

3. The preparation method of the composite temporary plugging agent as described in claim 1, characterized in that, In the step of mixing tetraethyl orthosilicate, dimethyl silicone oil, and deionized water and stirring to form a uniform viscous modified liquid, When the working temperature of the composite temporary plugging agent is (120℃, 160℃), the mass fractions of the tetraethyl orthosilicate and the dimethyl silicone oil are 5 parts and 5 parts, respectively.

4. The preparation method of the composite temporary plugging agent as described in claim 1, characterized in that, In the step of mixing tetraethyl orthosilicate, dimethyl silicone oil, and deionized water and stirring to form a uniform viscous modified liquid, When the working temperature of the composite temporary plugging agent is (160℃, 200℃), the mass fractions of the tetraethyl orthosilicate and the dimethyl silicone oil are 7 parts and 7 parts, respectively.

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