Oil reservoir deep profile control and displacement combined particle and preparation method and application thereof

Abstract

The invention discloses oil reservoir deep profile control and displacement combined particles and a preparation method and application thereof. The profile control and displacement combined particles comprise large-particle-size pre-crosslinked particles which are formed by polymerizing main agents including acrylamide and acrylic acid under the combined action of a conventional crosslinking agent and a metal crosslinking agent; the small-particle-size pre-crosslinked particles are formed by polymerizing main agents acrylamide and acrylic acid under the combined action of a conventional crosslinking agent and a decomposable crosslinking agent. According to the invention, the large-particle-size pre-crosslinked particles swell during aging at a certain temperature, and the metal crosslinking agent coated in the large-particle-size pre-crosslinked particles is gradually released; when the particles are aged at a certain temperature, the decomposable cross-linking agent of the small-particle-size pre-crosslinked particles can be subjected to chain scission to release carboxylate radicals, the carboxylate radicals and the metal cross-linking agent released by the large-particle-size pre-crosslinked particles are subjected to intermolecular complexation, the particles are cross-linked to form a net-shaped structure, weak gel is formed, the deep plugging strength of the existing pre-crosslinked particles is greatly improved, and the plugging effect is greatly improved. And the deep retention capacity of the system can be improved, and the purpose of efficient deep profile control and displacement is finally achieved.

Description

Technical Field

[0001] This invention relates to the field of offshore oilfield development technology, and in particular to a deep reservoir regulation and drive composite particle, its preparation method, and its application. Background Technology

[0002] With the development of water injection in my country's oilfields, major oilfields have successively entered the late-stage oil production phase of high or ultra-high water cut reservoirs. Due to the heterogeneity of the reservoir in both planar and vertical directions, differences in oil-water viscosity, and imbalances within oil-water well groups, significant intra- and inter-layer conflicts have arisen. As water injection development deepens, these conflicts intensify, leading to serious problems with large pores in the oil layers, a faster rate of water cut increase, poorer development results, and reduced waterflood recovery. Currently, pre-crosslinked gel particle-based oil displacement technology has become an effective means to improve oil recovery in high and ultra-high water cut reservoirs.

[0003] Pre-crosslinked gel particle-based enhanced oil recovery (EOR) technology is a method developed in the last decade. It's not simply a bottomhole treatment measure relying on profile control and water shut-off to reduce water cut; rather, it's a method of increasing oil recovery by adjusting intra- or inter-layer imbalances and increasing swept volume. The basic principle is to inject a pre-crosslinked gel system to block water flow channels in high-permeability zones, forcing water flow to be redirected to areas or layers with higher residual oil content, effectively expanding the swept volume and improving oil recovery. The pre-crosslinked system primarily functions to "block" and "redirect" the flow. "Blocking" involves the gel blocking high-permeability layers; "redirecting" involves the gel forcing the fluid to change its flow direction, redirecting it to areas or layers with higher residual oil content. This adjusts intra- and inter-layer imbalances simultaneously. Currently, the main problems with pre-crosslinked systems are that the system's strength and flexibility are insufficient to meet field requirements, and its performance deteriorates under high-temperature and high-salt conditions.

[0004] Currently, conventional gel particles used in pre-crosslinked systems have significant shortcomings. The particles absorb water rapidly, swelling before injection into the formation, complicating the injection process and hindering deep formation penetration. Furthermore, water absorption reduces particle strength and mechanical properties, making them prone to shear breakage and degradation, thus negating their flood control effect. To address the issues of poor shear resistance and low viscosity during flood control, it is necessary to modify conventional crosslinking agents and systems. This would allow the particles to swell slowly after water absorption, minimizing formation shear stress. Upon penetrating deeper formations, intermolecular complexation would lead to interparticle crosslinking into a network structure, increasing the viscosity of the gel particle dispersion system and forming a weak gel, thereby achieving deep flood control.

[0005] Therefore, it is necessary to provide a deep reservoir regulation and drive composite particle and its preparation method to overcome the above problems. Summary of the Invention

[0006] In order to solve the above-mentioned technical problems, the present invention provides a deep reservoir regulation and driving composite particle, its preparation method and application.

[0007] In a first aspect, the present invention provides a deep reservoir regulation and drive combination particle, which is achieved by the following technical solution.

[0008] A deep reservoir regulation and flooding composite particle, comprising: Large-diameter pre-crosslinked particles, with a particle size of 120-150μm, are polymerized by a main agent composed of acrylamide and acrylic acid under the combined action of conventional crosslinking agents and temperature-salinity dual-response coated metal crosslinking agents. Small-diameter pre-crosslinked particles, with a particle size of 50-70μm, are polymerized by a main agent composed of acrylamide and acrylic acid under the combined action of conventional crosslinking agent and thermosensitive decomposable crosslinking agent. The mass ratio of large-diameter pre-crosslinked particles to small-diameter pre-crosslinked particles is 9:1-3:1.

[0009] By adopting the above technical solution, the two types of pre-crosslinked particle solutions of the present invention have low initial viscosity and are relatively dispersed, thus they can penetrate deep into the reservoir. When aged at a certain temperature, the large-diameter pre-crosslinked particles swell, and the metal crosslinking agent encapsulated inside them is gradually released. When aged at a certain temperature, the decomposable crosslinking agent of the small-diameter pre-crosslinked particles breaks its chain and releases carboxylate ions, which undergo intermolecular complexation with the metal crosslinking agent released by the large-diameter pre-crosslinked particles. The particles crosslink into a network structure, forming a weak gel. This significantly improves the deep sealing strength of existing pre-crosslinked particles, while also enhancing the deep retention capacity of the system, and ultimately achieving the goal of efficient deep regulation and driving.

[0010] The large-particle-size pre-crosslinked particles of this invention are polymerized from acrylamide and acrylic acid as the main agents under the combined action of conventional crosslinking agents and metal crosslinking agents. Because the metal crosslinking agent reacts slowly during gelation, it is encapsulated within the large-particle-size pre-crosslinked particles. During aging at a certain temperature, the large-particle-size pre-crosslinked particles swell, and the encapsulated metal crosslinking agent is gradually released.

[0011] The small-diameter pre-crosslinked particles of this invention are polymerized from acrylamide and acrylic acid as the main agents under the combined action of conventional crosslinking agents and decomposable crosslinking agents. During aging at a certain temperature, the decomposable crosslinking agent in the small-diameter pre-crosslinked particles undergoes chain breakage, releasing carboxylate ions. These ions can then interact with the metal crosslinking agents released from the large-diameter pre-crosslinked particles through intermolecular complexation, resulting in a network structure between the particles and forming a weak gel.

[0012] Furthermore, in the large-particle-size pre-crosslinked particles, the main agent composed of acrylamide and acrylic acid accounts for 30% of the total system.

[0013] Furthermore, in the large-particle-size pre-crosslinked particles, the mass ratio of acrylamide (AM) to acrylic acid (AA) is 100:0-80:20; preferably, the acrylic acid content accounts for 0%-20% of the total amount of the main agent, such as 0%, 5%, 10%, 15%, 20%, and the acrylamide monomer accounts for 80%-100% of the total amount of the main agent, such as 80%, 85%, 90%, 95%, 100%.

[0014] Furthermore, in large-diameter pre-crosslinked particles, the total amount of conventional crosslinking agent and temperature-salinity dual-response coated metal crosslinking agent is 0.1%-1% of the main agent mass, and the mass ratio of conventional crosslinking agent to temperature-salinity dual-response coated metal crosslinking agent is 4:1-1:4.

[0015] Furthermore, in the small-diameter pre-crosslinked particles, the mass ratio of acrylamide to acrylic acid is 80:20-60:40; preferably, the acrylic acid content accounts for 20%-40% of the total amount of the main agent, such as 20%, 25%, 35%, 40%, and the acrylamide monomer accounts for 60%-80% of the total amount of the main agent, such as 60%, 65%, 75%, 80%.

[0016] Furthermore, in small-diameter pre-crosslinked particles, the total amount of conventional crosslinking agent and thermosensitive decomposable crosslinking agent is 0.1%-1% of the main agent mass, and the mass ratio of conventional crosslinking agent to thermosensitive decomposable crosslinking agent is 4:1-1:4.

[0017] Furthermore, the preparation method of the temperature-salinity dual-response coated metal crosslinking agent is as follows: Take the metal crosslinking agent and add a composite coating material of modified chitosan and low methoxyl pectin. The total amount of the composite coating material is 20%-30% of the mass of the metal crosslinking agent. Place the mixture in a high-speed stirring environment at 300-500 r / min for 15-20 min, and simultaneously add 5% calcium chloride solution dropwise at a rate of 1-2 mL / min to form a dense coating layer on the surface of the metal crosslinking agent. Then transfer it to a vacuum condition of 40-50℃ and -0.08 MPa for 2-3 h to dry.

[0018] Furthermore, the metal crosslinking agent is any one of chromium acetate, zirconium acetate, aluminum citrate, zirconium citrate, and chromium lactate; the mass ratio of modified chitosan to low-methoxyl pectin is 2:1 to 4:1; and the amount of calcium chloride added is 3% to 15% of the mass of the metal crosslinking agent. Specifically, the modified chitosan is carboxylated chitosan.

[0019] Furthermore, the preparation method of the thermosensitive decomposable crosslinking agent is as follows: polyethylene glycol diacrylate and itaconic anhydride are mixed at a mass ratio of 2:1 to 8:1, and azobisisobutyronitrile is added as an initiator accounting for 0.8%-1.2% of the total monomer mass; the temperature is raised to 65-75℃ under nitrogen protection and the reaction is kept at a constant temperature for 3-4 hours; after cooling, 10% sodium hydroxide solution is added to adjust the pH to 6.5-7.5, and unreacted impurities are removed by filtration.

[0020] Furthermore, the common crosslinking agents are N,N-methylenebisacrylamide and / or divinylbenzene.

[0021] Secondly, the present invention provides a method for preparing deep reservoir regulation and drive composite particles, which is achieved by the following technical solution.

[0022] A method for preparing the above-mentioned deep reservoir regulation and flooding composite particles includes the following steps: Preparation of large-size pre-crosslinked particles: A. Add acrylic monomer to deionized water and stir until homogeneous; then add acrylamide monomer and stir until homogeneous. B. Add a conventional crosslinking agent and a first initiator to the mixture obtained in step A, and stir until homogeneous; then add a temperature-salinity dual-response coated metal crosslinking agent and continue stirring until homogeneous; C. After purging with nitrogen for 30 minutes, add the second initiator at 10-40°C (preferably 15-35°C), continue purging with nitrogen for 2-3 minutes, and then seal. D. React at 55-65℃ for 2-4 hours, and after the reaction is completed, place at room temperature for 1-5 hours. Then, cut, dry, and granulate to a particle size of 120-150μm to obtain large-size pre-crosslinked particles. Preparation of small-diameter pre-crosslinked particles: a. Add acrylic monomer to deionized water and stir until homogeneous; adjust the pH to 7.0-9.0 using NaOH; then add acrylamide monomer and stir until homogeneous; b. Add a conventional crosslinking agent and a first initiator to the mixture obtained in step a, and stir until homogeneous; then add a thermosensitive decomposable crosslinking agent and continue stirring until homogeneous; c. After purging with nitrogen for 30 minutes, add the second initiator at 10-40°C (preferably 15-35°C), continue purging with nitrogen for 2-3 minutes, and then seal. d. React at 55-65℃ for 2-4 hours. After the reaction is complete, let stand at room temperature for 1-5 hours. Then, cut, dry, and granulate to a particle size of 50-70μm to obtain small-diameter pre-crosslinked particles.

[0023] Furthermore, the first initiator is potassium persulfate or ammonium persulfate, and the second initiator is sodium bisulfite; based on the total amount of the main agent, the mass fraction of both the first and second initiators is 0.03%-0.3%.

[0024] Thirdly, the present invention provides an application of a combination of deep reservoir regulation and drive particles, which is achieved by the following technical solution.

[0025] Application of the above-mentioned deep reservoir conditioning and driving combination particles as a conditioning and driving agent in oilfield development.

[0026] Furthermore, large-diameter pre-crosslinked particles and small-diameter pre-crosslinked particles are dissolved in water to form a regulating solution, with the total amount of large-diameter pre-crosslinked particles and small-diameter pre-crosslinked particles being 700–1400 mg / L.

[0027] This application has the following beneficial effects.

[0028] Both types of pre-crosslinked particle solutions of this invention have low initial viscosity and are relatively dispersed, thus allowing them to penetrate deep into oil reservoirs. During aging at a certain temperature, the large-diameter pre-crosslinked particles swell, and the metal crosslinking agent encapsulated within them is gradually released. During aging at a certain temperature, the decomposable crosslinking agent of the small-diameter pre-crosslinked particles breaks its chain and releases carboxylate ions, which undergo intermolecular complexation with the metal crosslinking agent released by the large-diameter pre-crosslinked particles. The particles crosslink into a network structure, forming a weak gel. This significantly improves the deep-sealing strength of existing pre-crosslinked particles while also enhancing the deep-sea retention capacity of the system, ultimately achieving the goal of efficient deep-sea regulation and driving.

[0029] This invention addresses the fundamental problem of uncontrollable release timing of conventional metal crosslinking agents by using a temperature-salinity dual-response coating modified metal crosslinking agent. The coating layer only releases metal ions due to salt-induced swelling and rupture in the deep reservoir, preventing premature reaction in the shallow formation that could lead to particle agglomeration and increased injection resistance, thus ensuring the combined particles can successfully reach the deep target area. Simultaneously, the decomposable crosslinking agent undergoes salt-sensitive modification, accelerating chain scission and carboxylate release only in high-salinity environments. This improves the stability of the crosslinking agent in high-temperature and high-salinity environments and achieves precise matching with the release rate of the metal crosslinking agent, solving the problem of rapid performance degradation of conventional flood control agents under high-temperature and high-salinity conditions.

[0030] In addition, the composite particles can adaptively adjust the reaction process according to the reservoir temperature and salinity gradient, so that they will not form gels too early to block shallow formation pores, nor will they lose their regulation and drive effect due to reaction lag. At the same time, the compatibility between the particles and formation fluids is significantly improved, reducing damage to reservoir pores and further ensuring long-term regulation and drive effect, breaking through the dilemma of existing pre-crosslinked particles that are either difficult to inject or have weak sealing. Attached Figure Description

[0031] Figure 1 This invention uses the combined particles in Example 1 and the large-diameter pre-crosslinked particles prepared in Comparative Example 1 as examples to measure the viscosity changes of the driving solution at different aging times using a coaxial cylindrical rotor Z41 Ti. Figure 2 The present invention uses scanning electron microscopy to observe the microstructure of the modified driving solution after 15 days of aging, taking the combined particles in Example 1 and the large-size pre-crosslinked particles prepared in Comparative Example 1 as examples. Figure 3 The present invention uses the combined particles in Example 1 and the large-size pre-crosslinked particles prepared in Comparative Example 1 as examples to illustrate the results of the modulation simulation experiment. Detailed Implementation

[0032] The present patent application will be further described below with reference to the embodiments. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the materials used in the preparation process in the following embodiments have not undergone further processing and have been commercially available.

[0033] The low-methoxyl pectin used in the following preparation examples and embodiments of the present invention has an esterification degree of 35% and was purchased from Guangdong Fangxin Biotechnology Co., Ltd. The polyethylene glycol diacrylate used in the following preparation examples and embodiments of the present invention has a degree of polymerization of 450 and was purchased from Sigma-Aldrich (Merck). The carboxylated chitosan used in the following preparation examples and embodiments of the present invention has a degree of deacetylation ≥95%, a viscosity of 100-200 mPa·s, and was purchased from Aladdin.

[0034] Preparation Example 1 The preparation method of temperature-salinity dual-response coated metal crosslinking agent is as follows: Take 100g of the metal crosslinking agent zirconium citrate, add a composite coating material of carboxylated chitosan and low-methoxyl pectin, the total amount of the composite coating material is 25g, and the mass ratio of carboxylated chitosan to low-methoxyl pectin is 3:1; place the mixture in a high-speed stirring at 400r / min for 15min, and at the same time add 5% calcium chloride solution dropwise at a rate of 1.5mL / min, the amount of calcium chloride added is 10% of the mass of the metal crosslinking agent, so that the composite coating material forms a dense coating layer on the surface of the metal crosslinking agent; then transfer to 45℃ and -0.08MPa vacuum conditions to dry for 2.5h.

[0035] Preparation Example 2 The preparation method of the thermosensitive decomposable crosslinking agent is as follows: Take 88g of polyethylene glycol diacrylate and 11g of itaconic anhydride, mix them evenly, and add 1.2g of azobisisobutyronitrile as an initiator; heat to 75℃ under nitrogen protection and react at a constant temperature for 4h; after cooling, add 10% sodium hydroxide solution to adjust the pH to 7, and filter to remove unreacted impurities.

[0036] Example 1 A method for preparing deep reservoir regulation and flooding composite particles includes the following steps: Weigh 500 mL of deionized water into a wide-mouth flask, place the flask on a magnetic stirrer, add 20 g of acrylic acid monomer, and stir until homogeneous; add 80 g of acrylamide monomer, and stir until homogeneous and transparent; add 0.1 g of N,N'-methylenebisacrylamide and 0.3 g of sodium bisulfite to the flask respectively, stir until homogeneous, then add 0.3 g of the temperature-salinity dual-response coated metal crosslinking agent prepared in Preparation Example 1; purge with nitrogen for 30 min, while controlling the solution temperature at 20 °C, then add ammonium persulfate, continue purging with nitrogen for 3 min, and seal. Observe the temperature change of the system and record the highest temperature reached and the time. When the system temperature drops to 65 °C, place it in a constant temperature water bath at the same temperature and continue heating for 4 h. After the reaction is complete, remove the flask, let it stand at room temperature for 2 h, then cut, dry, and granulate to obtain large-particle-size pre-crosslinked particles with a particle size of 120-150 μm.

[0037] Weigh 500 mL of deionized water into a wide-mouth flask, place the flask on a magnetic stirrer, add 30 g of acrylic acid monomer, and stir until homogeneous. Add NaOH solution to adjust the pH of the mixed solvent to 8.0, and stir in the wide-mouth flask until completely dissolved. After complete dissolution, add 70 g of acrylamide monomer and stir until homogeneous and transparent. Then add 0.1 g of N,N'-methylenebisacrylamide and 0.3 g of sodium bisulfite to the flask respectively, stir well, and then add 0.4 g of the decomposable crosslinking agent prepared in Preparation Example 2. Purge with nitrogen for 30 min while controlling the solution temperature at 20 °C, then add ammonium persulfate, continue purging with nitrogen for 3 min, and seal the flask. Observe the temperature change of the system and record the highest temperature reached and the time. When the system temperature drops to 65℃, it is placed in a constant temperature water bath at the same temperature and heated for another 4 hours. After the reaction is completed, the flask is taken out and placed at room temperature for 2 hours before being cut, dried, and granulated to obtain small-diameter pre-crosslinked particles with a particle size of 50-70μm.

[0038] Large-diameter pre-crosslinked particles and small-diameter pre-crosslinked particles were dissolved in water to form a regulating solution. The total amount of large-diameter and small-diameter pre-crosslinked particles was 1000 mg / L, and the ratio of large-diameter pre-crosslinked particles to small-diameter pre-crosslinked particles was 9 / 1.

[0039] Example 2 A method for preparing deep reservoir regulation and flooding composite particles includes the following steps: Weigh 500 mL of deionized water into a wide-mouth flask, place the flask on a magnetic stirrer, add 15 g of acrylic acid monomer, and stir until homogeneous; add 85 g of acrylamide monomer, and stir until homogeneous and transparent; then add 0.1 g of N,N'-methylenebisacrylamide and 0.3 g of sodium bisulfite to the flask respectively, stir until homogeneous, and then add 0.3 g of the temperature-salinity dual-response coated metal crosslinking agent prepared in Preparation Example 1; purge with nitrogen for 30 min, while controlling the solution temperature at 20 °C, then add ammonium persulfate, continue purging with nitrogen for 3 min, and seal. Observe the temperature change of the system and record the highest temperature reached and the time. When the system temperature drops to 65 °C, place it in a constant temperature water bath at the same temperature and continue heating for 4 h. After the reaction is complete, remove the flask, let it stand at room temperature for 2 h, then cut, dry, and granulate to obtain large-particle-size pre-crosslinked particles with a particle size of 120-150 μm.

[0040] Weigh 500 mL of deionized water into a wide-mouth flask, place the flask on a magnetic stirrer, add 35 g of acrylic acid monomer, and stir until homogeneous. Add NaOH solution to adjust the pH of the mixed solvent to 8.0, and stir in the wide-mouth flask until completely dissolved. After complete dissolution, add 65 g of acrylamide monomer and stir until homogeneous and transparent. Then add 0.1 g of N,N'-methylenebisacrylamide and 0.3 g of sodium bisulfite to the flask respectively, stir well, and then add 0.4 g of the decomposable crosslinking agent prepared in Preparation Example 2. Purge with nitrogen for 30 min, while controlling the solution temperature at 20 °C. Then add ammonium persulfate, continue purging with nitrogen for 3 min, and seal the flask. Observe the temperature change of the system and record the highest temperature reached and the time. When the system temperature drops to 65℃, it is placed in a constant temperature water bath at the same temperature and heated for another 4 hours. After the reaction is completed, the flask is taken out and placed at room temperature for 2 hours before being cut, dried, and granulated to obtain small-diameter pre-crosslinked particles with a particle size of 50-70μm.

[0041] Large-diameter pre-crosslinked particles and small-diameter pre-crosslinked particles were dissolved in water to form a regulating solution. The total amount of large-diameter and small-diameter pre-crosslinked particles was 1000 mg / L, and the ratio of large-diameter pre-crosslinked particles to small-diameter pre-crosslinked particles was 6 / 1.

[0042] Example 3 A method for preparing deep reservoir regulation and flooding composite particles includes the following steps: Weigh 500 mL of deionized water into a wide-mouth flask, place the flask on a magnetic stirrer, add 10 g of acrylic acid monomer, and stir until homogeneous; add 90 g of acrylamide monomer, and stir until homogeneous and transparent; then add 0.1 g of N,N'-methylenebisacrylamide and 0.3 g of sodium bisulfite to the flask respectively, stir until homogeneous, and then add 0.3 g of the temperature-salinity dual-response coated metal crosslinking agent prepared in Preparation Example 1; purge with nitrogen for 30 min, while controlling the solution temperature at 20 °C, then add ammonium persulfate, continue purging with nitrogen for 3 min, and seal. Observe the temperature change of the system and record the highest temperature reached and the time. When the system temperature drops to 65 °C, place it in a constant temperature water bath at the same temperature and continue heating for 4 h. After the reaction is complete, remove the flask, let it stand at room temperature for 2 h, then cut, dry, and granulate to obtain large-particle-size pre-crosslinked particles with a particle size of 120-150 μm.

[0043] Weigh 500 mL of deionized water into a wide-mouth flask, place the flask on a magnetic stirrer, add 40 g of acrylic acid monomer, and stir until homogeneous. Add NaOH solution to adjust the pH of the mixed solvent to 8.0, and stir in the wide-mouth flask until completely dissolved. After complete dissolution, add 60 g of acrylamide monomer and stir until homogeneous and transparent. Then add 0.1 g of N,N'-methylenebisacrylamide and 0.3 g of sodium bisulfite to the flask respectively, stir well, and then add 0.4 g of the decomposable crosslinking agent prepared in Preparation Example 2. Purge with nitrogen for 30 min, while controlling the solution temperature at 20 °C. Then add ammonium persulfate, continue purging with nitrogen for 3 min, and seal the flask. Observe the temperature change of the system and record the highest temperature reached and the time. When the system temperature drops to 65℃, it is placed in a constant temperature water bath at the same temperature and heated for another 4 hours. After the reaction is completed, the flask is taken out and placed at room temperature for 2 hours before being cut, dried, and granulated to obtain small-diameter pre-crosslinked particles with a particle size of 50-70μm.

[0044] Large-diameter pre-crosslinked particles and small-diameter pre-crosslinked particles were dissolved in water to form a regulating solution. The total amount of large-diameter and small-diameter pre-crosslinked particles was 1000 mg / L, and the ratio of large-diameter pre-crosslinked particles to small-diameter pre-crosslinked particles was 3 / 1.

[0045] Comparative Example Weigh 500 mL of deionized water into a wide-mouth flask, place the flask on a magnetic stirrer, add 20 g of acrylic acid monomer, and stir until homogeneous; add 80 g of acrylamide monomer, and stir until homogeneous and transparent; then add 0.1 g of N,N'-methylenebisacrylamide and 0.3 g of sodium bisulfite to the flask respectively, stir until homogeneous, and then add 0.3 g of the temperature-salinity dual-response coated metal crosslinking agent prepared in Preparation Example 1; purge with nitrogen for 30 min, while controlling the solution temperature at 20 °C, then add ammonium persulfate, continue purging with nitrogen for 3 min, and seal. Observe the temperature change of the system and record the highest temperature reached and the time. When the system temperature drops to 65 °C, place it in a constant temperature water bath at the same temperature and continue heating for 4 h. After the reaction is complete, remove the flask, let it stand at room temperature for 2 h, and then perform processes such as shearing, drying, and granulation to form large-diameter pre-crosslinked particles.

[0046] Large-diameter pre-crosslinked particles were dissolved in water to form a 1000 mg / L regulating and driving solution.

[0047] Performance testing Viscosity test: Figure 1 Taking the combined particles in Example 1 and the large-diameter pre-crosslinked particles prepared in Comparative Example 1 as examples, the viscosity changes of the aging solution at different aging times were measured using a coaxial cylindrical rotor Z41 Ti. As the swelling time increased, the viscosity of the combined particles increased significantly, indicating that they are more likely to undergo intermolecular crosslinking and form a complete network framework structure.

[0048] Morphological characteristics: Figure 2 Taking the combined particles in Example 1 and the large-particle-size pre-crosslinked particles prepared in Comparative Example 1 as examples, the microstructure of the modified driving solution after 15 days of aging was observed using scanning electron microscopy. The network structure of the combined particles is more compact, indicating that the crosslinking between particles is more complete, and the viscosity is relatively higher.

[0049] Adjustment drive simulation experiment: Refer to the standard "QH / S2132-2022 (20680) - Performance Evaluation of Offshore Oilfield Regulator Drive System". Figure 3 A modulated displacement simulation experiment was conducted using the combined particles from Example 1 and the large-size pre-crosslinked particles prepared in Comparative Example 1 as examples. The two modulated displacement solutions were injected into a solution with a permeability of 5000 × 10⁻⁶. -3 μm 2 In artificial rock cores, the relationship between pressure and injection volume was recorded, and the plugging rate was calculated. The plugging rate of the composite particles was 93.72%, while that of the large-diameter pre-crosslinked particles was 82.71%. The composite particles showed better deep plugging performance.

[0050] The deep reservoir regulation and drive composite particles provided by this invention address the challenges of developing high water-cut reservoirs in offshore oilfields. They achieve efficient deep regulation and drive through a dual-particle-size synergistic design: large-particle-size pre-crosslinked particles (120-150 μm) are formed by copolymerizing acrylamide and acrylic acid as the main agents (mass ratio 80:20-100:0) with conventional crosslinking agents (such as N,N-methylenebisacrylamide) and metal crosslinking agents (such as chromium acetate), with metal ions encapsulated within the particles; small-particle-size pre-crosslinked particles (50-70 μm) are formed by copolymerizing acrylamide and acrylic acid as the main agents (mass ratio 60:40-80:20) after neutralization under weakly alkaline conditions with conventional crosslinking agents and decomposable crosslinking agents (polyethylene glycol diacrylate), with the decomposable crosslinking agent undergoing chain scission at high temperatures to release carboxylate ions. Both types of particles exhibit good dispersibility upon injection, allowing them to penetrate deep into the reservoir. During high-temperature swelling, the metal ions released by the larger particles undergo intermolecular complexation with the carboxylate ions released by the smaller particles, forming a network-like weak gel structure that significantly enhances plugging strength and retention capacity. The preparation process includes monomer dissolution, initiator polymerization, curing, and granulation. In application, the total concentration of the flooding solution is adjusted to 700-1400 mg / L, with a particle size ratio of 9 / 1-3 / 1. Experiments show that this combined particle composition achieves good results at a permeability of 5000 × 10⁻⁶. -3 μm 2 The core plugging rate reaches 93.72%, which is better than the 82.71% of single large-diameter particles. It has advantages such as low initial viscosity and good injection properties, and is suitable for deep regulation and displacement in high-temperature and high-salinity oil reservoirs to improve the recovery rate.

[0051] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A deep reservoir regulation and displacement composite particle, characterized in that, include: Large-diameter pre-crosslinked particles, with a particle size of 120-150μm, are polymerized by a main agent composed of acrylamide and acrylic acid under the combined action of conventional crosslinking agents and temperature-salinity dual-response coated metal crosslinking agents. Small-diameter pre-crosslinked particles, with a particle size of 50-70μm, are polymerized by a main agent composed of acrylamide and acrylic acid under the combined action of conventional crosslinking agent and thermosensitive decomposable crosslinking agent. The mass ratio of large-diameter pre-crosslinked particles to small-diameter pre-crosslinked particles is 9:1-3:

1.

2. The deep reservoir regulation and displacement composite particle according to claim 1, characterized in that, In large-diameter pre-crosslinked particles, the mass ratio of acrylamide to acrylic acid is 100:0-80:20; the total amount of conventional crosslinking agent and temperature-salinity dual-response coated metal crosslinking agent is 0.1%-1% of the main agent mass, and the mass ratio of conventional crosslinking agent to temperature-salinity dual-response coated metal crosslinking agent is 4:1-1:

4.

3. The deep reservoir regulation and displacement composite particle according to claim 1, characterized in that, In small-diameter pre-crosslinked particles, the mass ratio of acrylamide to acrylic acid is 80:20-60:40; the total amount of conventional crosslinking agent and thermosensitive decomposable crosslinking agent is 0.1%-1% of the main agent mass, and the mass ratio of conventional crosslinking agent to thermosensitive decomposable crosslinking agent is 4:1-1:

4.

4. The deep reservoir regulation and displacement composite particle according to claim 1, characterized in that, The preparation method of temperature-salinity dual-response coated metal crosslinking agent is as follows: Take the metal crosslinking agent and add a composite coating material of modified chitosan and low methoxyl pectin. The total amount of the composite coating material is 20%-30% of the mass of the metal crosslinking agent. Place the mixture in a high-speed stirring environment at 300-500 r / min for 15-20 min, and simultaneously add 5% calcium chloride solution dropwise at a rate of 1-2 mL / min. Then transfer it to a vacuum condition of 40-50℃ and -0.08 MPa to dry for 2-3 h.

5. The deep reservoir regulation and displacement composite particle according to claim 4, characterized in that, The metal crosslinking agent is any one of chromium acetate, zirconium acetate, aluminum citrate, zirconium citrate, and chromium lactate; the mass ratio of modified chitosan to low-methoxyl pectin is 2:1 to 4:1; the amount of calcium chloride added is 3% to 15% of the mass of the metal crosslinking agent.

6. The deep reservoir regulation and displacement composite particle according to claim 1, characterized in that, The preparation method of the thermosensitive decomposable crosslinking agent is as follows: Polyethylene glycol diacrylate and itaconic anhydride are mixed at a mass ratio of 2:1 to 8:1, and azobisisobutyronitrile is added at a mass ratio of 0.8% to 1.2% of the total monomers. The mixture is heated to 65-75℃ under nitrogen protection and reacted at a constant temperature for 3-4 hours. After cooling, 10% sodium hydroxide solution is added to adjust the pH to 6.5-7.5, and unreacted impurities are removed by filtration.

7. The deep reservoir regulation and displacement composite particle according to claim 1, characterized in that, Common crosslinking agents are N,N-methylenebisacrylamide and / or divinylbenzene.

8. A method for preparing the deep reservoir regulation and displacement composite particles according to any one of claims 1-7, characterized in that, Includes the following steps: Preparation of large-size pre-crosslinked particles: A. Add acrylic monomer to deionized water and stir until homogeneous; then add acrylamide monomer and stir until homogeneous. B. Add a conventional crosslinking agent and a first initiator to the mixture obtained in step A, and stir until homogeneous; then add a temperature-salinity dual-response coated metal crosslinking agent and continue stirring until homogeneous; C. After purging with nitrogen for 30 minutes, add the second initiator at 10-40°C, continue purging with nitrogen for 2-3 minutes, and then seal. D. React at 55-65℃ for 2-4 hours, and after the reaction is completed, place at room temperature for 1-5 hours. Then, cut, dry, and granulate to a particle size of 120-150μm to obtain large-size pre-crosslinked particles. Preparation of small-diameter pre-crosslinked particles: a. Add acrylic monomer to deionized water and stir until homogeneous; adjust the pH to 7.0-9.0 using NaOH; then add acrylamide monomer and stir until homogeneous; b. Add a conventional crosslinking agent and a first initiator to the mixture obtained in step a, and stir until homogeneous; then add a thermosensitive decomposable crosslinking agent and continue stirring until homogeneous; c. After purging with nitrogen for 30 minutes, add the second initiator at 10-40°C, continue purging with nitrogen for 2-3 minutes, and then seal. d. React at 55-65℃ for 2-4 hours. After the reaction is complete, let stand at room temperature for 1-5 hours. Then, cut, dry, and granulate to a particle size of 50-70μm to obtain small-diameter pre-crosslinked particles.

9. The application of the deep reservoir conditioning and driving composite particles according to any one of claims 1-7 as a conditioning and driving agent in oilfield development.

10. The application according to claim 9, characterized in that: Large-diameter pre-crosslinked particles and small-diameter pre-crosslinked particles are dissolved in water to form a regulating solution, with the total amount of large-diameter and small-diameter pre-crosslinked particles being 700–1400 mg / L.

Images