A composite gel particle plugging agent for plugging steam channeling and its preparation and application

Abstract

The application discloses a composite gel particle plugging agent for plugging steam channeling and preparation and application thereof, and belongs to the technical field of oil field chemistry. The plugging agent has a triple composite structure of "rigid inorganic core-elastic gel shell-oil-soluble surface layer", the elastic gel shell penetrates and is chemically anchored in the porous structure of the core through a crosslinked network, and an organic-inorganic interpenetrating interface is formed. The surface modifier is an oil-soluble polymer. The plugging agent realizes the synergy of rigid support, elastic plugging and flexible selectivity, so that the volume retention rate of the plugging agent is greater than or equal to 85%, the single-particle compressive strength is greater than or equal to 1.5 MPa, and the ratio (selectivity index) of the plugging rate of the water phase channel to the damage rate of the oil phase channel is greater than or equal to 7.0 after the plugging agent is aged for 7 days in a steam environment at 300 DEG C and a salinity of 20*10 4 mg / L, and the technical problems of easy failure, low plugging strength and lack of flexible selectivity of existing plugging agents under extreme high temperature and high salinity are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, and more specifically to a composite gel particle plugging agent for sealing steam channeling, its preparation and application. Background Technology

[0002] Thermal recovery of heavy oil, especially steam injection and steam drive, is an effective means of developing heavy oil reservoirs. However, during long-term steam injection, due to reservoir heterogeneity and the presence of natural or induced fractures, steam "channeling" or "steam migration" is highly likely to occur. Steam flows rapidly along high-permeability zones or fractures to the production well, resulting in a small steam sweep volume, low thermal efficiency, and a sharp increase in water cut in the production well, seriously affecting development effectiveness and economic benefits.

[0003] To control steam channeling, chemical plugging agents are typically used. Gel-particle plugging agents have attracted attention due to their good deformability and ability to migrate to deeper formations. Current common technical solutions and their limitations include:

[0004] Pre-crosslinked gel particles: Water-absorbing resin particles synthesized and crosslinked on the ground. Their advantages are high strength, but they generally have limited temperature resistance (usually below 200℃), and are prone to dehydration, decomposition, and pulverization under high-temperature steam, losing their sealing ability; in addition, the particle elastic modulus is uniform, and their adaptability to complex pore throats is insufficient.

[0005] Underground cross-linked gel: A polymer and cross-linking agent solution is injected underground to form a gel. Its gelation time and strength are difficult to control precisely, it is easily diluted or washed away in high-permeability channels, its sealing strength is insufficient, and it is sensitive to high temperature and high salinity environments.

[0006] Inorganic / organic simple composite particles: Inorganic fillers (such as fly ash and clay) are combined with polymer gel through physical mixing. Although these particles improve temperature resistance to some extent, the inorganic and organic phases are only in physical contact with each other, and the interfacial bonding is weak. Under high temperature, high pressure and the scouring and shearing of formation fluids, interfacial delamination is very likely to occur, leading to particle breakage and sealing failure.

[0007] Particles with a preliminary core-shell concept: Existing technologies have reported the use of inorganic nanomaterials as the core and polymers as the shell in other fields (such as drilling fluid plugging). However, these particles are typically small in size (nanoscale), loosely structured, and lack strong interfacial bonding between the outer shell and the core. Their design goals and performance requirements are drastically different from plugging agents used to seal millimeter-scale steam channel blockages. Directly applying them to steam channel blockage makes it difficult to address the issues of long-term structural integrity, high-strength plugging, and selective entry into heterogeneous reservoirs for large-scale particles at high temperatures.

[0008] In summary, existing technologies lack a steam channeling plugging agent that can simultaneously meet the following stringent requirements: 1) extreme high temperatures above 300℃ and ultra-high salinity (>20×10⁻⁶). 4 1) It is stable for a long time under conditions of (mg / L); 2) It possesses both rigid and flexible mechanical properties, providing high-strength support while adapting to deformation to fit the pore throat; 3) It has flexible selectivity, preferentially entering and blocking high-water-content vapor channels while causing minimal damage to oil-bearing areas. Therefore, developing such plugging agents is a crucial technical problem that urgently needs to be solved in the field of profile control and water shut-off in heavy oil thermal recovery. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a composite gel particle plugging agent for sealing vapor channeling, its preparation method, and its application. This invention creatively designs and constructs a unique three-layer composite structure of a "rigid inorganic core - elastic gel shell - oil-soluble surface layer," and crucially achieves the permeation and chemical anchoring of the outer gel shell and the porous core structure, forming a strong and tough organic-inorganic interpenetrating interface. This synergistically resolves the contradiction of being unable to simultaneously achieve optimal temperature resistance, strength, adaptability, and selectivity.

[0010] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0011] The primary objective of this application is to provide: a composite gel particle plugging agent for sealing vapor channeling, wherein the plugging agent is a composite particle with a core-shell structure, comprising:

[0012] a) Core: Composed of high-temperature resistant inorganic porous material, wherein the high-temperature resistant inorganic porous material is selected from at least one of modified sepiolite, porous ceramic micro powder, expanded vermiculite, and sintered diatomaceous earth; the core not only serves as a thermally stable framework (melting point >1500℃), but its open porous structure also provides a key foundation for subsequent interfacial bonding.

[0013] b) Outer shell: Covering the outer surface of the core, it is a three-dimensional network elastic gel layer formed by a cross-linking reaction of a temperature-resistant and salt-resistant polymer (such as HPAM, AM / AMPS, hydrophobic associative polymer), a cross-linking agent, and a delay modifier; wherein, the outer shell gel penetrates and is chemically anchored in the porous structure of the core through its cross-linking network, forming an organic-inorganic interpenetrating interface, which can effectively transfer stress and prevent interfacial delamination under high temperature and high pressure, giving the particles excellent long-term stability and high strength.

[0014] c) Surface Modifier: Adhered to the surface of the outer shell, it is an oil-soluble polymer selected from at least one of polymethyl methacrylate, styrene-maleic anhydride copolymer, and polyvinylpyrrolidone-stearate; this layer gives the particles flexible selectivity: it remains inert in the oil phase environment, ensuring that the particles have good flowability, do not stick together, and cause little damage in the oil-containing area; when entering a high water content or steam channel, it softens or partially dissolves under the action of high temperature water / steam, exposing the hydrophilic gel shell, which promotes the particles to absorb water, stick together, and efficiently accumulate and seal;

[0015] The temperature- and salt-resistant polymer mentioned in step b) is at least one of partially hydrolyzed polyacrylamide, acrylamide / 2-acrylamido-2-methylpropanesulfonic acid copolymer, and hydrophobic associative polymer; the crosslinking agent is an organic phenolic resin crosslinking agent or an organic chromium crosslinking agent; and the delay modifier is sodium lactate, oxalic acid, or disodium ethylenediaminetetraacetate.

[0016] The synergistic effect of the above three-layer structure ultimately enables the plugging agent to exhibit the following comprehensive properties: at 300℃ and a mineralization of 20×10⁻⁶... 4 After aging for 7 days in a steam environment of mg / L, the volume retention rate is ≥85% and the single particle compressive strength is ≥1.5 MPa; in the dual-tube parallel core experiment, the selectivity index (high permeability tube blockage rate / low permeability oil-bearing tube permeability damage rate) is ≥7.0.

[0017] As a preferred technical solution, the thickness of the organic-inorganic interpenetrating interface is 5-50 μm.

[0018] As a preferred technical solution, based on the total mass of the composite gel particles, the mass percentage of the core is 70%-90%, the mass percentage of the shell is 9%-29%, and the mass percentage of the surface modifier is 0.5%-5%.

[0019] As a preferred technical solution, the concentration of the temperature-resistant and salt-resistant polymer in the shell is 5000-15000 mg / L.

[0020] As a preferred technical solution, the particle size range of the composite gel particles is 0.1 mm - 5.0 mm; the dissolution rate of the oil-soluble polymer surface modification layer is less than 5% after immersion in a simulated oil phase environment for 48 hours, while it can soften or partially dissolve within 30 minutes after immersion in hot water at 90°C.

[0021] Another object of this application is to provide: a method for preparing the above-mentioned composite gel particle plugging agent for sealing vapor channeling, comprising the following steps:

[0022] S1. Core pretreatment: The high-temperature resistant inorganic porous material is crushed and sieved to the target particle size range, and then subjected to acid washing and high-temperature activation treatment to obtain a pretreated core material with high surface activity and open pores;

[0023] S2. Preparation of shell prepolymer solution: Dissolve the temperature-resistant and salt-resistant polymer in high-mineralization water and stir until completely dissolved. Then, add the crosslinking agent and the delay regulator in sequence and mix evenly to obtain the shell prepolymer solution. The addition of the delay regulator can delay the crosslinking reaction and provide a time window for subsequent wetting and granulation.

[0024] S3. Core-shell composite and granulation: The pretreated core material obtained in step S1 is added to the shell prepolymer liquid prepared in step S2. The prepolymer liquid is fully wetted and penetrated into the core pores by strong stirring. Then, wet core-shell particles are formed by dripping, extrusion or spray granulation.

[0025] The beneficial effect of the above operation is that, during the delayed crosslinking window, the low-viscosity prepolymer solution is fully wetted and penetrated into the pores of the activated core by vigorous stirring.

[0026] S4. Stepwise crosslinking and curing: The wet core-shell particles are first placed at 40-60℃ for 2-4 hours for preliminary crosslinking and shaping, and then heated to 80-120℃ for 6-12 hours for deep crosslinking and curing. During this process, the prepolymer liquid completes the crosslinking reaction on the surface of the core and in the pores to form an interpenetrating interface, resulting in composite particles with a stable gel shell.

[0027] S5. Surface modification: The composite particles obtained in step S4 are immersed in or sprayed with an organic solvent solution of an oil-soluble polymer, and then dried to remove the solvent, so that the oil-soluble polymer is attached to the particle surface in the form of a continuous film, thereby obtaining the composite gel particle plugging agent.

[0028] The high-temperature resistant inorganic porous material mentioned in step S1 is selected from at least one of modified sepiolite, porous ceramic powder, expanded vermiculite, and sintered diatomaceous earth;

[0029] The temperature-resistant and salt-resistant polymer in step S2 is at least one of partially hydrolyzed polyacrylamide, acrylamide / 2-acrylamido-2-methylpropanesulfonic acid copolymer, and hydrophobic associative polymer; the crosslinking agent is an organic phenolic resin crosslinking agent or an organic chromium crosslinking agent; and the delay modifier is sodium lactate, oxalic acid, or disodium ethylenediaminetetraacetate.

[0030] As a preferred technical solution, the temperature of the high-temperature activation treatment in step S1 is 500-800℃; the salinity of the water prepared in step S2 is ≥10×10 4mg / L; the mass-to-volume ratio of the pretreated core material to the shell prepolymer liquid in step S3 is 1 g : 8-12 mL.

[0031] Another object of this application is to provide the application of the composite gel particle plugging agent or the composite gel particle plugging agent prepared by the method in sealing steam crossflow channels during heavy oil thermal recovery.

[0032] As a preferred technical solution, the composite gel particle plugging agent is dispersed in the carrier fluid at an injection concentration of 0.5%-3.0% and injected into the target oil reservoir formation; the carrier fluid is oilfield produced water or high-salinity brine.

[0033] As a preferred technical solution, the composite gel particle plugging agent exhibits a selectivity index ≥7.0 in the dual-tube parallel core displacement experiment, and is suitable for plugging large steam-flowing channels or fractures with a temperature of 150℃-350℃ and a permeability ≥1.0 D.

[0034] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) Unexpected long-term high-temperature stability and strength: Due to the formation of an "organic-inorganic interpenetrating interface", the inorganic core and the organic gel shell are no longer in simple physical contact, but form a mechanical interlock and chemical bond. During high-temperature aging, the core effectively blocks the direct conduction of heat to the gel interior, while the gel network anchored in the pores acts like a "rivet" to inhibit the propagation of microcracks in the core under thermal stress. Comparative experiments show that the strength retention rate (approximately 72%) of the particles of the present invention with interpenetrating interfaces (Example 1) after aging at 300°C for 7 days is much higher than that of the particles that are only physically mixed (Comparative Example 2, approximately 30%). The synergistic enhancement effect brought about by this interface structure forcibly formed through a specific process is something that those skilled in the art could not have predicted based solely on the common knowledge that "inorganic materials are resistant to high temperatures" and "polymers can be crosslinked".

[0036] (2) Achieving a balance between "adaptive" plugging and high-strength plugging: The unique core-shell structure enables each particle to possess a composite mechanical behavior of "rigid core + elastic shell". When plugging the throat, the elastic shell undergoes large deformation to adapt to the shape and provide an initial seal; when the pressure increases, the internal rigid core provides the ultimate support point to prevent the particle from being squeezed out as a whole. This "rigid-flexible" characteristic allows the plugging body to withstand pressure gradients of over 30 MPa / m, which is 2-3 times that of traditional single-material particles, and it has excellent long-term stability.

[0037] (3) A breakthrough in flexible and selective blocking effect was achieved: The combination of the "oil-soluble surface layer" and the "core-shell structure" produced a synergistic effect. The surface layer ensures selective entry, while once activated in the target channel, its high-strength core-shell structure provides a blocking strength far exceeding that of ordinary selective particles. Experimental data show that the selectivity index of the particles of this invention is 7.74, while the selectivity index of similar core-shell particles without surface modification layer (Comparative Example 3) is only 1.31. This shows that the combination of surface modification layer and high-strength core-shell structure produces a selective blocking efficiency of 1+1>>2, which has not been revealed in the prior art.

[0038] (4) The preparation process is innovative and repeatable: the synergy of the "delayed crosslinking" and "step curing" processes precisely controls the formation process of the interpenetrating interface, solves the common technical problems in the preparation of core-shell materials such as uneven encapsulation and shell detachment, and ensures the uniformity and stability of product performance. Detailed Implementation

[0039] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. Example 1

[0040] (Modified sepiolite core + HPAM gel shell + PMMA surface layer)

[0041] (1) Kernel preprocessing

[0042] Take 100.0 g of 150-mesh modified sepiolite powder. Soak it in 500 mL of 5% (w / w) dilute hydrochloric acid solution at 60℃ with constant stirring for 3 hours. Filter and wash the filter cake with deionized water until the washing liquid is neutral (pH≈7). Place the washed solid in a muffle furnace and calcine it at 750℃ at a rate of 5℃ / min for 4 hours. After cooling in the furnace, grind and sieve to obtain the activated sepiolite core material for later use. BET testing showed that its specific surface area increased from 25 m² / g to approximately 280 m² / g.

[0043] (2) Preparation of shell prepolymer solution

[0044] In a 2L beaker, add 1000 mL of a mineral with a mineralization degree of 18 × 10⁻⁶. 4A simulated saline solution (formulation: NaCl 150 g / L, CaCl2 20 g / L, MgCl2 10 g / L) was prepared. 15.0 g of partially hydrolyzed polyacrylamide (HPAM, molecular weight approximately 15 million, degree of hydrolysis 25%) was slowly added under mechanical stirring in a 40°C water bath for 6 hours until completely dissolved, yielding a transparent, viscous solution. Then, 3.0 g of organic phenolic resin crosslinking agent (PF-2 type) and 0.8 g of sodium lactate were added sequentially, and stirring was continued at low speed for 1 hour to obtain a homogeneous and stable shell prepolymer solution. At this point, the HPAM concentration was approximately 15000 mg / L.

[0045] (3) Core-shell composite and granulation

[0046] 100.0 g of pretreated sepiolite core material was added to the prepolymer solution. Using a high-speed shear emulsifier, the mixture was continuously stirred at 5000 rpm for 40 minutes to ensure the low-viscosity prepolymer solution fully wetted and penetrated the micro-nano pores of the sepiolite. Subsequently, the uniform slurry was extruded through a precision extrusion sieve with a 1.0 mm aperture into thin strips, which were immediately cut into cylindrical wet particles approximately 1.2 mm long using a rotary cutter. In this step, the mass-to-volume ratio of core material to prepolymer solution was approximately 1 g : 10 mL.

[0047] (4) Step crosslinking curing

[0048] The wet granules were evenly spread in an enamel tray and placed in a forced-air drying oven with a humidity >80%. First, they were cured at 55℃ for 3 hours to complete the initial cross-linking and shaping. Then, the temperature was increased to 110℃ for further deep cross-linking and curing for 12 hours. After cooling to room temperature, dried core-shell composite granules were obtained. Observation showed that the outer shell gel had penetrated into the core pores, forming an organic-inorganic interpenetrating interface with a thickness of approximately 20-30 μm.

[0049] (5) Surface modification

[0050] Prepare 200 mL of an 8% (w / w) solution of polymethyl methacrylate (PMMA, molecular weight approximately 100,000) in ethyl acetate. Immerse the core-shell composite particles described above in this solution and stir slowly for 5 minutes to ensure uniform surface contact. After removal, place them in a fume hood at 50°C and dry for 4 hours to allow the solvent to completely evaporate and for PMMA to form a continuous film on the particle surface. The final product, particle A, is obtained. Example 2

[0051] (Porous ceramic core + AM / AMPS gel shell + SMA surface layer)

[0052] (1) Kernel preprocessing

[0053] Take 80.0 g of porous alumina ceramic powder with a particle size of 80 mesh and an average pore size of about 5 μm, soak it in 5% dilute hydrochloric acid solution for 1 hour, filter it and wash it with deionized water until neutral. Then place it in a muffle furnace, heat it directly to 800℃ at 5℃ / min, calcine it for 2 hours, and cool it for later use.

[0054] (2) Preparation of shell prepolymer solution

[0055] In 1000 mL, the mineralization is ≥10×10 4 To a saline solution containing mg / L of chromium ions, add 12.0 g of acrylamide / 2-acrylamido-2-methylpropanesulfonic acid copolymer (AM / AMPS, AMPS molar content 30%) and stir to dissolve. Then add a chromium acetate solution with a chromium ion (Cr³⁺) content of 5000 mg and 0.5 g of sodium lactate, and mix thoroughly. At this point, the concentration of the AM / AMPS copolymer in the prepolymer solution is approximately 12000 mg / L.

[0056] (3) Core-shell composite and granulation

[0057] 80.0 g of pretreated ceramic micropowder was added to the prepolymer solution and stirred at high speed for 30 minutes to ensure thorough wetting. Granulation was performed using a spray dryer with the inlet temperature set at 180℃ and the feed rate controlled to rapidly dry the droplets into spheres. Spherical wet particles with a particle size distribution of 0.2-0.8 mm were collected.

[0058] (4) Step crosslinking curing

[0059] The particles were preheated and crosslinked at 60°C for 2 hours, and then deeply cured at 100°C for 8 hours.

[0060] (5) Surface modification

[0061] Particles B were obtained by impregnation and spraying with a 6% styrene-maleic anhydride copolymer (SMA) toluene solution, followed by drying at 60°C. Example 3

[0062] (High-core kernel accounts for 90%)

[0063] (1) Kernel preprocessing

[0064] Take 90.0 g of a mixture of modified sepiolite and sintered diatomaceous earth at a mass ratio of 2:1, and perform acid washing and activation treatment at 700℃ as in Example 1.

[0065] (2) Preparation of shell prepolymer solution

[0066] 6.0 g of hydrophobic associating polymer was added to 1000 mL of highly saline solution and stirred until dissolved. An appropriate amount of organic phenolic resin crosslinking agent and 0.3 g of disodium ethylenediaminetetraacetate (EDTA-2Na) were added as a delay regulator and mixed thoroughly. At this point, the concentration of the hydrophobic associating polymer in the prepolymer solution was approximately 6000 mg / L.

[0067] (3) Core-shell composite and granulation

[0068] 90.0 g of core material was added to 1000 mL of shell prepolymer solution and stirred vigorously to ensure thorough wetting. The slurry was then added dropwise into hot paraffin at 80°C to form spherical particles with a particle size of approximately 2.0 mm.

[0069] (4) Step crosslinking curing

[0070] Preliminary setting at 50℃ for 4 hours, deep curing at 105℃ for 10 hours.

[0071] (5) Surface modification

[0072] A very thin layer was applied using a 2% polyvinylpyrrolidone-stearate (PVP-SA) ethanol solution, resulting in minimal surface modifier adhesion after drying. This yielded particle C.

[0073] Comparative Example 1 (Particle D): Pure polymer particles

[0074] Operation: Completely omit the "kernel preprocessing" and "kernel-shell compositing" steps.

[0075] Preparation: The shell prepolymer liquid (without the core) prepared in Example 1 was directly dropped into hot paraffin at 80°C. After crosslinking and curing, pure HPAM gel particles with a particle size of about 1.2 mm were obtained. No surface modification was performed.

[0076] Comparative Example 2 (Particle E): Simple Mixture of Particles

[0077] Operation: Disrupt the formation process of the "interpenetrating interface" and replace it with physical mixing.

[0078] preparation:

[0079] (1) Take 100.0 g of the same batch of pretreated dry sepiolite powder as in Example 1.

[0080] (2) Prepare a batch of pure HPAM gel according to the method of Example 1, but without adding a core, and dry and mechanically pulverize it to a particle size similar to that of Example 1.

[0081] (3) Mix 100.0 g of sepiolite powder and 100.0 g of pulverized dry gel particles in a high-speed mixer for 10 minutes to obtain a mixture. No surface modification is performed.

[0082] Comparative Example 3 (particle F): Particles without surface layer

[0083] Procedure: Omit the "surface modification" step.

[0084] Preparation: Follow steps 1-4 of Example 1 exactly to prepare core-shell composite particles with interpenetrating interfaces. In step 5 (surface modification), skip the PMMA solution impregnation step and directly dry the cured composite particles at 50°C for the same time to obtain the product.

[0085] Comparative Example 4 (Particle G): Inorganic Core Particle

[0086] Operation: All steps of “preparation of shell prepolymer liquid”, “core-shell composite”, “step crosslinking curing” and “surface modification” are omitted.

[0087] Preparation: Take 100.0 g of the same batch of pretreated and activated dry sepiolite powder as in Example 1, and sieve it to control the particle size distribution within the range of 1.0-1.5 mm as a control sample.

[0088] Performance testing

[0089] (1) Long-term stability test of high temperature and salt resistance

[0090] To determine the long-term high-temperature and salt resistance stability of the plugging agents prepared in this application (Examples 1, 2, and 3) and the plugging agents prepared in Comparative Examples 1, 2, 3, and 4, the following experiments were conducted:

[0091] 1) Place each sample particle in a high-temperature, high-pressure reactor, and add 20×10 mineralization... 4 The saline solution has a concentration of mg / L and a sufficient liquid-to-solid ratio.

[0092] 2) Set the temperature to 300℃ and the pressure to 5 MPa (simulating a steam environment) and conduct a static aging test.

[0093] 3) Take samples on days 1, 3, and 7 respectively, cool them, and then test them:

[0094] Volume retention rate: The volume of water displacement was measured using a graduated cylinder and compared with that before aging.

[0095] Single-particle compressive strength: Using a micro-force material testing machine, 20 intact particles were randomly selected, and 4) they were crushed at a rate of 1 mm / min. The average strength value was taken. The experimental results are shown in Table 1.

[0096] Table 1. Results of long-term stability tests for high temperature and salt resistance

[0097]

[0098] Conclusion: As shown in Table 1, the strengths of Examples 1, 2, and 3 after 7 days of aging were 1.8, 1.6, and 2.1 MPa, respectively, with a volume retention of ≥85%. Comparative Example 1 (without a core) completely failed; Comparative Example 2 (without an interpenetrating interface) experienced a sharp drop in performance, strongly demonstrating the decisive role of the "interpenetrating interface" in long-term stability.

[0099] (2) Evaluation of selective plugging performance (dual-tube parallel core test)

[0100] To test the plugging flexibility of the plugging agents prepared in Examples 1 (with surface layer), 2, and 3, Comparative Example 3 (without surface layer, same structure), and Comparative Example 1 (pure gel), the following experiments were conducted:

[0101] 1) Core preparation: Two parallel sand-filled pipe models (30cm long, 2.5cm in diameter) were constructed. One pipe was filled with coarse sand to simulate a high-permeability water channel (K_w ≈ 3.5 D), and the other pipe was filled with fine sand to simulate a low-permeability oil-bearing zone (K_o ≈ 0.8 D). After saturation with water, the low-permeability pipe was driven to bound water saturation using simulated oil.

[0102] 2) Injection and Monitoring: Inject a 0.8% concentration plugging agent suspension into the parallel inlet at a rate of 1.0 mL / min. After injecting 0.5 PV, switch to subsequent water drive. Monitor and record the inlet pressure and outlet flow rate of both pipes in real time.

[0103] Data processing:

[0104] Plugging rate = (1 - Permeability of aqueous phase after clogging / Initial permeability of aqueous phase) × 100%;

[0105] Damage rate = (1 - oil phase permeability after plugging / initial oil phase permeability) × 100%;

[0106] Selectivity Index (SI) = High-permeability pipe blockage rate / Low-permeability oil-bearing pipe permeability damage rate; the experimental results are shown in Table 2.

[0107] Table 2 Evaluation results of selective plugging performance of different groups

[0108]

[0109] Results analysis: Examples 1-3 with oil-soluble surface layers all achieved high selectivity indices (SI>7.0). Comparative Example 3 (same structure but without surface layer) had an SI close to 1, proving that the oil-soluble surface layer is the key to generating "flexible selectivity," rather than the core-shell structure itself.

[0110] (3) Breakthrough pressure gradient test

[0111] To verify the high sealing strength (supporting the invention effect) brought about by the "rigid-flexible" structure, tests were conducted on Examples 1 and 2, and Comparative Examples 1 and 4. The experimental procedures are as follows:

[0112] 1) Use a single high-permeability sand-filled pipe (K ≈ 5.0 D, where K is the internationally recognized symbol for permeability), saturated with water.

[0113] 2) Inject 0.3 PV plugging agent suspension, shut in the well and let it age for 24 hours to allow the particles to remain at the pore throat;

[0114] 3) Increase the injection pressure stepwise at a rate of 0.05 MPa / min, and record the pressure-flow curve until the flow rate increases sharply (the plug is broken down). The pressure at this point is the breakthrough pressure.

[0115] 4) Calculate the breakthrough pressure gradient: breakthrough pressure / core length; the experimental results are shown in Table 3.

[0116] Table 3. Pressure gradient test results for different groups

[0117]

[0118] Results Analysis: The sealing strength of the composite particles of the present invention (Examples 1 and 2) is approximately three times that of the pure gel particles in Comparative Example 1, demonstrating the synergistic mechanical advantages of the "core-shell structure". Comparative Example 4, despite having high pressure, failed to effectively seal the particles, highlighting the necessity of an elastic outer shell.

[0119] (4) Oil resistance and thermal responsiveness test of surface modified layer

[0120] The following tests were conducted to evaluate the oil resistance and thermal responsiveness of the material prepared in this application:

[0121] Take 1.0 g of the particle samples obtained in each example and immerse them in 50 mL of simulated oil phase environment (using decane). After 48 hours, filter, dry, and weigh, and calculate the solubility. Take another 1.0 g of sample and add it to 50 mL of 90℃ deionized water, and observe the changes in the particle surface state within 30 minutes. The results are shown in Table 4.

[0122] Table 4. Results of oil resistance and thermal responsiveness tests for different groups

[0123]

[0124] Results Analysis: As shown in Table 4, after the particles of Examples 1, 2 and 3 were soaked in the simulated oil phase (decane) for 48 hours, the dissolution rate of their surface modified layer was extremely low (< 2%), indicating that the oil-soluble polymer layer has excellent chemical stability in the oil phase environment. This ensures that the plugging particles can remain intact and have good mobility when passing through underground oil-bearing areas.

[0125] Meanwhile, in 90°C hot water, the surface layer of all the particles in the examples softened significantly within 30 minutes, exposing the internal hydrophilic gel shell. This rapid thermal response behavior contrasts sharply with the phenomenon in Comparative Example 3 (without a surface layer) where the particles directly absorbed water, swelled, and severely adhered to each other.

[0126] The above results collectively demonstrate that the oil-soluble surface layer introduced in this invention successfully endows particles with the key characteristics of "inert stability in the oil phase and flexible activation in the water / vapor phase." This characteristic is the physicochemical basis for the plugging agent to selectively enter and efficiently block high water-content channeling, while minimizing damage to the oil-bearing layer (i.e., achieving a high selectivity index).

[0127] In summary, this invention, through specific material selection and innovative preparation processes, constructs a core-shell structured composite gel particle with an "organic-inorganic interpenetrating interface," supplemented with an oil-soluble, flexible surface layer. This design achieves a breakthrough and unexpected synergistic improvement in three aspects: long-term stability, plugging strength, and flexible selectivity of the plugging agent under extreme high-temperature and high-salt environments. It effectively solves existing technical challenges and provides a novel solution for the efficient management of steam channeling in heavy oil thermal recovery.

[0128] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0129] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. 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 the invention. Therefore, the invention 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 disclosed herein.

Claims

1. A composite gel particle plug for plugging steam channeling, characterized in that, The plugging agent is a composite particle with core-shell structure, comprising: a) Inner core: composed of high-temperature-resistant inorganic porous material, the high-temperature-resistant inorganic porous material is selected from at least one of modified sepiolite, porous ceramic micro-powder, expanded vermiculite, and sintered diatomite; b) Shell: coated on the outer surface of the inner core, it is a three-dimensional network elastic gel layer formed by cross-linking reaction of temperature-resistant and salt-resistant polymer, cross-linking agent, and delay regulator; wherein the shell gel penetrates and chemically anchors in the porous structure of the inner core through its cross-linking network, forming an organic-inorganic interpenetrating interface; c) Surface modifier: attached to the surface of the shell, it is an oil-soluble polymer selected from at least one of polymethyl methacrylate and styrene-maleic anhydride copolymer; The temperature-resistant and salt-resistant polymer in step b) is at least one of partially hydrolyzed polyacrylamide, acrylamide / 2-acrylamido-2-methylpropanesulfonic acid copolymer, and hydrophobic associating polymer; the cross-linking agent is an organic phenolic resin cross-linking agent or an organic chromium cross-linking agent; and the delay regulator is sodium lactate, oxalic acid, or disodium ethylenediaminetetraacetate.

2. The composite gel particle plug of claim 1, wherein, The thickness of the organic-inorganic interpenetrating interface is 5-50 μm.

3. The composite gel particle plug of claim 1, wherein, The mass percentage of the inner core is 70%-90%, the mass percentage of the shell is 9%-29%, and the mass percentage of the surface modifier is 0.5%-5%, based on the total mass of the composite gel particle.

4. The composite gel particle plug of claim 1, wherein, The particle size of the composite gel particle ranges from 0.1 mm to 5.0 mm; the oil-soluble polymer surface modification layer has a dissolution rate of less than 5% after being soaked in a simulated oil phase environment for 48 hours, and can be softened or partially dissolved within 30 minutes of being soaked in hot water at 90°C.

5. A method of making the composite gel particle plug of any one of claims 1-4, wherein the method comprises: The method comprises the following steps: S1. Inner core pretreatment: crushing and sieving the high-temperature-resistant inorganic porous material to the target particle size range, and then performing acid washing and high-temperature activation treatment to obtain a pretreated inner core material with high surface activity and open pores; S2. Shell prepolymer liquid preparation: dissolving the temperature-resistant and salt-resistant polymer in high-mineralization prepared water, stirring until completely dissolved, then sequentially adding the cross-linking agent and the delay regulator, and mixing uniformly to obtain a shell prepolymer liquid; S3. Core-shell compounding and granulation: adding the pretreated inner core material obtained in step S1 to the shell prepolymer liquid prepared in step S2, and stirring vigorously to allow the prepolymer liquid to fully infiltrate and penetrate into the inner core pores, and then forming wet core-shell particles by dropwise addition, extrusion, or spray granulation; S4. Stepwise cross-linking and curing: first placing the wet core-shell particles in a 40-60°C environment for 2-4 hours of preliminary cross-linking and setting, and then heating to 80-120°C for 6-12 hours of deep cross-linking and curing, during which the prepolymer liquid completes the cross-linking reaction on the inner core surface and in the pores to form an interpenetrating interface, thereby obtaining composite particles with a stable gel shell; S5. Surface modification: immersing or spraying the composite particles obtained in step S4 in an organic solvent solution of the oil-soluble polymer, and then drying to remove the solvent, so that the oil-soluble polymer is attached to the surface of the particles in the form of a continuous film, thereby obtaining the composite gel particle plugging agent. The high-temperature-resistant inorganic porous material in step S1 is selected from at least one of modified sepiolite, porous ceramic powder, expanded vermiculite and sintered diatomite; The temperature-resistant and salt-resistant polymer in step S2 is at least one of partially hydrolyzed polyacrylamide, acrylamide / 2-acrylamido-2-methylpropane sulfonic acid copolymer and hydrophobic associating polymer; the crosslinking agent is an organic phenolic resin crosslinking agent or an organic chromium crosslinking agent; the retardation regulator is sodium lactate, oxalic acid or disodium ethylenediaminetetraacetate; and the concentration of the temperature-resistant and salt-resistant polymer in the shell prepolymer solution is 5000-15000 mg / L.

6. The method of claim 5, wherein, The temperature of the high-temperature activation treatment in step S1 is 500-800°C; the mineralization of the prepared water in step S2 is ≥10×10 4 mg / L; and the mass-volume ratio of the pretreated core material to the shell prepolymer solution in step S3 is 1g:8-12 mL.

7. The use of the composite gel particle plugging agent according to any one of claims 1-4 or prepared by the method of any one of claims 5-6 in plugging steam channeling channels in a heavy oil thermal recovery process.

8. Use according to claim 7, characterized in that, The composite gel particle plugging agent is dispersed in a carrying fluid at an injection concentration of 0.5%-3.0% and injected into a target oil reservoir formation; the carrying fluid is oilfield produced water or high salinity brine.

9. Use according to claim 7, characterized in that, The composite gel particle plugging agent has a selectivity index ≥7.0 in a double-tube parallel core displacement experiment and is suitable for plugging steam channeling large pore channels or cracks with a temperature of 150-350°C and a permeability ≥1.0 D.

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