Inorganic composite high-strength water plugging material for oil and water wells and preparation method thereof

Abstract

The application provides an inorganic composite high-strength oil-water well water plugging material and a preparation method thereof, and belongs to the technical field of oil field chemicals. The material is prepared from the following raw materials in percentage by weight: 15-20% of high-activity mineral admixture, 2-8% of high-performance silicate, 3-5% of agricultural and forestry biomass material with a particle size of 1-10 microns, 5-8% of suspending agent, 0.5-0.7% of dispersing agent, 0.04-0.05% of retarder, 1-2% of reinforcing agent, itaconic acid modified acrylate and pH regulator, and the balance of water. The preparation method comprises a step-by-step mixing and stirring process. The application utilizes 3-5% of waste agricultural and forestry biomass, and through the synergistic effect of various components, the prepared water plugging material has the advantages of high compressive strength (1.79 MPa), controllable curing time (24-48 hours), good slurry stability, high temperature resistance (greater than or equal to 140 DEG C), etc. The application realizes the unification of waste resource utilization and high-performance water plugging material, and is especially suitable for water plugging operation in high-temperature fractured oil reservoirs.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical agents, and in particular to an inorganic composite high-strength oil and water well plugging material and its preparation method. Background Technology

[0002] In the later stages of oilfield development, water channeling is a common problem in oil wells, severely impacting oil recovery. Using water-blocking materials to seal high-permeability layers or fractures is a key solution. Currently, commonly used water-blocking materials mainly include organic polymers and inorganic Cement.

[0003] Organic polymer plugging agents (such as polyacrylamide), while having low initial viscosity and being easy to pump, are prone to degradation in high-temperature (>120℃) and high-salinity reservoir environments, leading to plugging failure. They are also relatively expensive, and some products may decompose at high temperatures, producing harmful substances. Inorganic plugging agents (such as cement grout), although having high strength and good temperature resistance, generally suffer from problems such as high brittleness, susceptibility to shrinkage cracks, weak adhesion to formation rocks, poor grout stability, and easy settling.

[0004] On the other hand, my country is extremely rich in agricultural and forestry biomass resources (such as rice husks and straw), with an annual output of approximately 700 million tons. Currently, a large amount of agricultural and forestry waste is incinerated or landfilled, which not only wastes resources but also causes serious environmental pollution. Although there are utilization pathways such as anaerobic fermentation to produce biogas, these methods suffer from low efficiency, insufficient cellulose utilization, and difficulties in treating biogas slurry and residue. Therefore, developing high-value utilization pathways for agricultural and forestry biomass is crucial.

[0005] Current technologies have not yet effectively achieved the synergistic effect of high-value utilization of agricultural and forestry biomass and performance improvement of inorganic plugging agents. Therefore, there is an urgent need to develop a new type of water-blocking material that is low-cost, environmentally friendly, resistant to high temperature and pressure, and possesses high strength and good construction performance. Summary of the Invention

[0006] This invention aims to solve at least one of the technical problems existing in the prior art, and proposes an inorganic composite high-strength oil and water well plugging material and its preparation method. The purpose of this invention is to solve a series of problems existing in traditional materials, such as poor environmental adaptability and strong resource dependence, thereby promoting the deep integration of biomass industry and oil and water well plugging technology.

[0007] This invention provides an inorganic composite high-strength oil and water well plugging material, made from the following raw materials by weight percentage:

[0008] The ingredients include 15%–20% highly active mineral admixtures, 2%–8% high-performance silicates, 3%–5% agricultural and forestry biomass materials, 5%–8% suspending agent, 0.5%–0.7% dispersant, 0.04%–0.05% retarder, 1%–2% reinforcing agent, 1%–2% itaconic acid modified acrylate, pH adjuster, and water.

[0009] Preferably, the highly active mineral admixture has a specific surface area of ​​400-450 m² / kg and is composed of the following components by mass percentage: 40%-55% calcium oxide, 30%-45% silicon dioxide, 10%-20% aluminum oxide, 10%-20% magnesium oxide, 0.5%-1% manganese oxide, and 0.5%-1% ferrous oxide.

[0010] Preferably, the agricultural and forestry biomass material is rice husk and / or straw powder that has been mechanically ground to a particle size of 1-10 μm; and / or, the reinforcing agent is composed of the following components in mass percentage: 30%-50% lime, 30%-40% calcium carbonate, and the balance being calcium chloride, and the particle size of the reinforcing agent is 3-10 μm.

[0011] Preferably, the dispersant is composed of the following components in weight percentage: 30%–40% lignin sulfonate, 10%–30% sodium polyphosphate, and the balance being sodium dodecyl sulfonate; and / or, the retarder is composed of the following components in weight percentage: 20%–30% salicylic acid, 30%–40% tannic acid, and the balance being polymethyl methacrylate.

[0012] Preferably, the suspending agent is composed of the following components by mass percentage: 40%–60% silicon dioxide, 20%–30% aluminum oxide, 10%–20% magnesium oxide, 1%–5% iron oxide, with the balance being fly ash; and / or, the pH adjuster is composed of the following components by mass percentage: 60%–75% sodium carbonate, 20%–35% sodium bicarbonate, with the balance being sodium hydroxide.

[0013] Preferably, the reinforcing agent is composed of the following raw materials in the indicated mass fractions: 30%–50% lime, 30%–40% calcium carbonate, and the remainder being calcium chloride.

[0014] Preferably, the itaconic acid-modified acrylate is prepared by the following method:

[0015] Itaconic acid was dissolved in deionized water, a reflux device was set up, and after stirring evenly, it was added to the polymerization reactor. Nitrogen gas was introduced for 10 minutes to remove air from the reaction system. Nitrogen gas was continuously introduced throughout the polymerization process so that the reaction was carried out under nitrogen protection.

[0016] The temperature of the reaction solution was heated to the reflux temperature with stirring.

[0017] Add the mixture of acrylate monomers and initiator dropwise, and continue the reaction for 1 hour to ensure the reaction proceeds fully;

[0018] After the reaction was completed, the reaction solution was cooled to room temperature, and after precipitation, filtration, washing and drying, itaconic acid modified acrylate was obtained.

[0019] This invention also provides a method for preparing inorganic composite high-strength oil and water well plugging material, the preparation method comprising the following steps:

[0020] S1. Add pH adjuster, suspending agent, retarder, agricultural and forestry biomass materials, and itaconic acid modified acrylate to water, stir, and obtain mixture a;

[0021] S2. Add the dispersant and high-performance silicate to the mixture a obtained in step S1, stir, and obtain mixture b;

[0022] S3. Mix the highly active mineral admixture and reinforcing agent evenly to obtain mixture c;

[0023] S4. Add the mixture c obtained in step S3 to the mixture b obtained in step S2, and stir to obtain the water-blocking material.

[0024] Preferably, in step S1, the stirring speed is 400-600 r / min and the stirring time is 10-20 min; in step S2, the stirring speed is 400-600 r / min and the stirring time is 10-20 min; in step S4, the stirring speed is 500-700 r / min and the stirring time is 10-20 min.

[0025] Preferably, in step S1, the stirring speed is 500 r / min and the stirring time is 15 min; in step S2, the stirring speed is 500 r / min and the stirring time is 15 min; and in step S4, the stirring speed is 600 r / min and the stirring time is 15 min.

[0026] Preferably, the agricultural and forestry biomass material is prepared by the following method:

[0027] After cleaning and drying agricultural and forestry waste raw materials such as rice husks and straw, the biomass raw materials are crushed using a crusher, and then screened with a vibrating screen to obtain uniform particles of 30 mesh.

[0028] The pre-selected 30-mesh uniform biomass particles were placed in a Raymond mill, and the rotation speed was controlled. The process was repeated multiple times until the diameter of the raw material reached the 1-10 μm level.

[0029] This invention provides an inorganic composite high-strength oil and water well plugging material and its preparation method. Addressing the common problems of existing oil and water well plugging materials, such as poor toughness, susceptibility to shrinkage cracks, weak adhesion to the matrix, high cost, and environmental unfriendliness, this invention provides an agricultural and forestry biomass-inorganic composite high-strength oil and water well plugging material and its preparation method. This material aims to utilize waste agricultural and forestry biomass to achieve resource utilization, while simultaneously obtaining a green oil and water well plugging material that combines high strength, high toughness, excellent impermeability, and durability. Attached Figure Description

[0030] Figure 1 This is a schematic flowchart illustrating a method for preparing an inorganic composite high-strength oil-water well plugging material according to an embodiment of the present invention.

[0031] Figure 2 This is a comparison chart showing the results of measuring the suspension performance of the method provided in the embodiments of the present invention. Detailed Implementation

[0032] To enable those skilled in the art to better understand the technical solutions of the present invention, exemplary embodiments of the present invention are described below in conjunction with the accompanying drawings, including various details of the embodiments of the present invention to aid understanding. These should be considered merely exemplary. Therefore, those skilled in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0033] Where there is no conflict, the various embodiments of the present invention and the features thereof may be combined with each other.

[0034] As used herein, the term “and / or” includes any and all combinations of one or more related enumerated entries.

[0035] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms “a” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that when the terms “comprising” and / or “made of” are used in this specification, the presence of the stated feature, integral, step, operation, element, and / or component is specified, but the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof is not excluded. Terms such as “connected” or “linked” are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect.

[0036] Unless otherwise specified, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art. It will also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having the meaning consistent with their meaning in the context of the relevant art and the invention, and will not be interpreted as having an idealized or overly formal meaning unless expressly so defined herein.

[0037] Within the existing technological system, the high-value utilization of agricultural and forestry biomass and the improvement of inorganic material performance have not yet achieved effective synergy. Specifically, currently used organic water-blocking agents have several problems: firstly, their cost is relatively high; secondly, under high-temperature and high-salt environmental conditions, these water-blocking agents are prone to degradation; and thirdly, certain types of organic water-blocking agents may decompose and produce harmful substances under high-temperature conditions.

[0038] To address at least one of the technical problems existing in the aforementioned related technologies, this invention provides an inorganic composite high-strength oil and water well plugging material, made from the following raw materials in parts by weight: 15%–20% highly active mineral admixture, 2%–8% high-performance silicate, 3%–5% agricultural and forestry biomass materials, 5%–8% suspending agent, 0.5%–0.7% dispersant, 0.04%–0.05% retarder, 1%–2% reinforcing agent, 2% itaconic acid-modified acrylate, pH adjuster, and the balance being water. The plugging material obtained by the above formulation can be adapted to environments with well depth temperatures above 140℃.

[0039] The reinforcing agent is composed of the following raw materials by mass fraction: 30%–50% lime, 30%–40% calcium carbonate, and the balance being calcium chloride. The particle size of the reinforcing agent is 3μm–10μm. It is used to enhance the compressive strength of the plugging agent, ensuring the sealing effect in deep reservoirs.

[0040] The dispersant is composed of the following raw materials by mass fraction: 30%–40% lignin sulfonate, 10%–30% sodium polyphosphate, and the balance being sodium dodecyl sulfonate. It is used to increase the dispersion of highly active mineral admixtures and biomass, reducing agglomeration that leads to low plugging strength and affects the plugging effect.

[0041] The retarder is composed of the following raw materials in the indicated mass fractions: 20%–30% salicylic acid, 30%–40% tannic acid, and the balance being polymethyl methacrylate. It is used to increase the curing time of the plugging agent, allowing it to be injected deeper into the reservoir, enhancing the sealing effect at the far end of the reservoir and ensuring the effectiveness of the application.

[0042] The suspending agent is composed of the following raw materials by mass fraction: 40%–60% silicon dioxide, 20%–30% aluminum oxide, 10%–20% magnesium oxide, 1%–5% iron oxide, and the balance being fly ash.

[0043] The pH adjuster is composed of the following raw materials by mass fraction: 60%–75% sodium carbonate, 20%–35% sodium bicarbonate, and the balance being sodium hydroxide. The pH adjuster can increase the weak acid content, creating a hydrolytic equilibrium condition that allows the pH to remain stable in an alkaline environment under certain conditions, thereby enhancing the sealing and gelling effect.

[0044] This material aims to utilize waste agricultural and forestry biomass to achieve resource utilization, while obtaining a green oil and water well plugging material with high strength, high toughness, excellent impermeability and durability.

[0045] The composite plugging agent made from this material has a density of 1.12 g / cm³ to 1.23 g / cm³ and a viscosity of [missing information]. The curing time is 24–48 hours, and the compressive strength is 1.7 MPa–2.1 MPa. It can solve the problems of poor pumpability and low strength of conventional inorganic plugging agents, as well as the difficulty in sealing fractured flow in oil reservoirs, and meet the water shut-off requirements of fractured oil reservoirs with temperatures above 140℃.

[0046] In another embodiment of the present invention, the highly active mineral admixture has a specific surface area of ​​400–450 m² / kg and is composed of the following components by mass percentage: calcium oxide 40%–55%, silicon dioxide 30%–45%, aluminum oxide 10%–20%, magnesium oxide 10%–20%, manganese oxide 0.5%–1%, and ferrous oxide 0.5%–1%. The highly active mineral admixture has a specific surface area of ​​400–450 m² / kg. 2 ·kg -1 .

[0047] Under high temperature and pressure, highly active mineral admixtures allow SiO2 and Al2O3 to adsorb onto the surface of geological rocks through van der Waals forces, forming a dense packing structure. Their high hardness (Mohs hardness 5-6) resists water erosion, while their porous structure (such as slag wool) locks in water through capillary action. The layered silicate structure in the suspending agent consists of two Si-O tetrahedra sandwiching an Al-O octahedron, with exchangeable Na+ between the layers. + / Ca 2+ Upon contact with water, the hydration of interlayer cations causes the crystal layers to expand, forming a gel-like barrier; sodium polyphosphate (such as sodium hexametaphosphate) in the dispersant passes through PO4... 3- Group and Ca 2+ / Mg 2+ The reaction produces a phosphate precipitate. PO4 3-The tetrahedral structure connects metal ions via POP bridging bonds, forming chain-like or cyclic polymers, increasing strength; high-performance silicates hydrolyze to generate silicic acid (H2SiO3), which further reacts with Ca... 2+ / Mg 2+ The reaction produces an insoluble calcium / magnesium silicate precipitate. (SiO4) 4- Tetrahedrons coordinate with metal ions through oxygen bridges (Si-O-Si) to form a three-dimensional network structure; phenolic hydroxyl and carboxyl groups (-COOH) in the retarder coordinate with metal ions (Ca) 2+ Mg 2+ Cross-linking forms coordination bonds, and the C=O double bond in the carboxyl group forms coordination bonds with metal ions. Phenolic hydroxyl groups enhance intermolecular forces through hydrogen bonds, inhibiting the precipitation reaction of metal ions. Agricultural biomass contains a large number of hydroxyl groups (-OH), which can be adsorbed onto strata rocks through hydrogen bonds and van der Waals forces. The hydroxyl groups on the cellulose molecular chain form hydrogen bonds with Si-O / Al-O groups, enhancing adhesion. At high temperatures, the organic acids produced by biomass degradation can react with calcium and magnesium ions to form precipitates, enhancing the strength of the plugging agent.

[0048] Further modification of acrylates with itaconic acid by adding the -COOH group can increase its solubility in water, and under alkaline conditions, the -COOR group hydrolyzes to produce a large amount of -COO. - , and thus Ca 2+ With carboxyl-COO - The reaction produces a new substance, Ca(COOR)2. Notably, the carboxyl group originates from a different polyester chain, and the same Ca... 2+ Connecting two carboxyl groups results in the generation of a large amount of Ca in the system. 2+ and -COO - A large number of itaconic acid-modified acrylate chains are generated through Ca 2+ They connect to form a cross-linked network structure composed of organic and inorganic substances.

[0049] As another embodiment of the present invention, agricultural and forestry biomass materials are prepared by the following method:

[0050] After cleaning and drying agricultural and forestry waste raw materials such as rice husks and straw, the biomass raw materials are crushed using a crusher, and then screened with a vibrating screen to obtain uniform particles of 30 mesh, which helps to control the output particle size during mechanical activation.

[0051] The pre-selected 30-mesh uniform biomass particles were placed in a Raymond mill, and the rotation speed was controlled. The process was repeated multiple times until the diameter of the raw material reached the 1-10 μm level.

[0052] refer to Figure 1As another embodiment of the present invention, the present invention also provides a method for preparing the water-blocking material, comprising the following steps: S1, adding pH adjuster, suspending agent, retarder, agricultural and forestry biomass materials, and itaconic acid modified acrylate to water, and stirring at 500 r / min for 15 min to obtain mixture a; S2, adding dispersant and high-performance silicate to mixture a obtained in step S1, and stirring at 500 r / min for 15 min to obtain mixture b; S3, mixing highly active mineral admixture and reinforcing agent evenly to obtain mixture c; S4, adding mixture c obtained in step S3 to mixture b obtained in step S2, and stirring at 600 r / min for 15 min to obtain the water-blocking material, with the following performance index: density 1.12~1.23 g / cm³. 3 viscosity The curing time is 24–48 h, and the compressive strength is 1.7–2.1 MPa.

[0053] The mechanism of action is as follows: After the slurry is pumped into the formation fractures, the suspending and dispersing agents ensure stable suspension of the particles, preventing sedimentation. The retarder controls the solidification reaction rate, allowing the slurry to penetrate deeper into the formation. Over time and with the influence of temperature, the high-performance silicate and highly reactive mineral admixtures undergo hydration reactions, forming a network-like gel and crystalline products with calcium ions provided by the reinforcing agent. Simultaneously, the micron-sized agricultural and forestry biomass particles not only bind to the inorganic network and rock surface through hydroxyl groups, but their high-temperature degradation products also participate in the reaction, further enhancing the structure. Ultimately, a dense, high-strength composite material is formed, firmly bonded to the formation, effectively blocking water flow channels.

[0054] In a further embodiment, the itaconic acid-modified acrylate is prepared by the following method:

[0055] Itaconic acid was dissolved in deionized water, a reflux device was set up, and after stirring evenly, it was added to the polymerization reactor. Nitrogen gas was introduced for 10 minutes to remove air from the reaction system. Nitrogen gas was continuously introduced throughout the polymerization process so that the reaction was carried out under nitrogen protection.

[0056] The temperature of the reaction solution was heated to the reflux temperature with stirring.

[0057] Add the mixture of acrylate monomers and initiator dropwise, and continue the reaction for 1 hour to ensure the reaction proceeds fully;

[0058] After the reaction was completed, the reaction solution was cooled to room temperature, and after precipitation, filtration, washing and drying, itaconic acid modified acrylate was obtained.

[0059] According to the water-blocking material and preparation method of the present invention, the comparative effects of the materials are illustrated below using 7 examples and 6 comparative examples, following the specific proportions (weight percentage) shown in Table 1 and strictly adhering to the above-mentioned methods. Figure 1 The preparation methods shown were used to prepare seven types of water-blocking materials as follows:

[0060] Example 1: Water-blocking material, made from the following raw materials by mass percentage: 20% high-activity mineral admixture, 2% high-performance silicate, 3% agricultural and forestry biomass materials, 8% suspending agent, 0.5% dispersant, 0.05% retarder, 2% reinforcing agent, 2% itaconic acid modified acrylate, pH adjuster, and the balance being water.

[0061] The high-activity mineral admixture has a particle size of 5μm to 30μm. The agricultural and forestry biomass materials have a particle size of 1 to 10μm. The reinforcing agent consists of the following raw materials in the indicated mass fractions: lime 30%, calcium carbonate 30%, with the balance being calcium chloride. The reinforcing agent has a particle size of 5μm to 13μm. The dispersant consists of the following raw materials in the indicated mass fractions: lignin sulfonate 40%, sodium polyphosphate 10%, with the balance being sodium dodecyl sulfonate. The retarder consists of the following raw materials in the indicated mass fractions: salicylic acid 20%, tannic acid 30%, with the balance being polymethyl methacrylate. The suspending agent consists of the following raw materials in the indicated mass fractions: silica 40% to 60%, alumina 20% to 30%, magnesium oxide 10% to 20%, iron oxide 1% to 5%, with the balance being fly ash. The activator consists of the following raw materials in the indicated mass fractions: sodium carbonate 75%, sodium bicarbonate 20%, with the balance being sodium hydroxide.

[0062] The preparation method for this example is as follows:

[0063] S1. Add pH adjuster, suspending agent, retarder, agricultural and forestry biomass, and itaconic acid modified acrylate to water, and stir at 500 r / min for 15 min to obtain mixture a;

[0064] S2. Add the dispersant and high-performance silicate to the mixture a obtained in S1, and stir at 500 r / min for 15 min to obtain mixture b;

[0065] S3. Mix the highly active mineral admixture and reinforcing agent evenly to obtain mixture c;

[0066] S4. Add the mixture c obtained in S3 to the mixture b obtained in S2, and stir at 600 r / min for 15 min to obtain an agricultural and forestry biomass-inorganic composite high-strength oil and water well plugging material.

[0067] Example 2: 15% highly active mineral admixture, 2% high-performance silicate, 3% agricultural and forestry biomass materials, 8% suspending agent, 0.5% dispersant, 0.05% retarder, 2% reinforcing agent, 2% itaconic acid-modified acrylate, pH adjuster, and the balance is water. The rest is the same as in Example 1.

[0068] Example 3: 15% highly active mineral admixture, 2% high-performance silicate, 3% agricultural and forestry biomass materials, 4% suspending agent, 0.5% dispersant, 0.05% retarder, 2% reinforcing agent, 2% itaconic acid-modified acrylate, pH adjuster, and the balance is water. The rest is the same as in Example 1.

[0069] Example 4: 15% highly active mineral admixture, 4% high-performance silicate, 3% agricultural and forestry biomass materials, 8% suspending agent, 0.5% dispersant, 0.05% retarder, 2% reinforcing agent, 2% itaconic acid-modified acrylate, pH adjuster, and the balance is water. The rest is the same as in Example 1.

[0070] Example 5: 15% highly active mineral admixture, 2% high-performance silicate, 6% agricultural and forestry biomass materials, 8% suspending agent, 0.5% dispersant, 0.05% retarder, 2% reinforcing agent, 2% itaconic acid-modified acrylate, pH adjuster, and the balance is water. The rest is the same as in Example 1.

[0071] Example 6: The raw material composition of the active mineral admixture is adjusted to: 0% calcium oxide, 30%–45% silicon dioxide, 10%–20% aluminum oxide, 10%–20% magnesium oxide, 0.5%–1% manganese oxide, 0.5%–1% ferrous oxide, etc. The rest is the same as in Example 1.

[0072] Example 7: The raw material composition of the reinforcing agent is adjusted to a mixture of lime and calcium chloride. The rest is the same as in Example 1.

[0073] Comparative Example 1: It differs from Example 1 only in that it does not include agricultural and forestry biomass materials.

[0074] Comparative Example 2: It differs from Example 1 only in that it does not include a suspending agent.

[0075] Comparative Example 3: It differs from Example 1 only in that no retarder is added.

[0076] Comparative Example 4: It differs from Example 1 only in that no pH adjuster is added.

[0077] Comparative Example 5: It differs from Example 1 only in that it does not contain high-performance silicate.

[0078] Comparative Example 6: It differs from Example 1 only in that no dispersant is added.

[0079] Comparative Example 7: A high-strength oil and water well plugging material synthesized according to the preparation method provided in Example 1, consisting of agricultural and forestry biomass-inorganic composite materials; the difference is that Comparative Example 7 does not contain itaconic acid-modified acrylate.

[0080] The compressive strength and curing time of the composite plugging agents of Examples 1-7 and Comparative Examples 1-7 were determined according to the "Sy / T5590-2004 Performance Evaluation Method for Profile Control Agents".

[0081] The method for further testing the curing time is as follows: the prepared composite oil-water well plugging material mixture is stirred evenly and poured into a 2050mm mold, and cured at 140℃. Every 3 hours, the cured sample is taken out and tested with a test needle. The time when the test needle cannot sink into the mold is the curing time.

[0082] Further testing of compressive strength is conducted using a periodically calibrated pressure testing machine. During operation, ensure the specimen's center is aligned with the indenter and load the specimen uniformly at the standard loading rate. Loading rates that are too fast or too slow will lead to deviations in results. After a set of experiments, outliers are removed, and the average result is taken.

[0083] Table 1 Compressive strength and consolidation time of water-blocking materials

[0084]

[0085] As can be seen from the test results of the composite plugging agent in Table 1, the compressive strength increases with the increase of the amount of highly active mineral admixture, with the highest compressive strength being 1.74 MPa; the compressive strength decreases with the decrease of calcium oxide content in the highly active mineral admixture; the calcium carbonate content in the reinforcing agent also affects the compressive strength of the composite plugging agent, and the compressive strength of the composite plugging agent decreases significantly when no calcium carbonate is added.

[0086] The composite plugging agents prepared in Examples 2, 4 and Comparative Example 5 showed that the compressive strength of the composite plugging agents first increased and then decreased with the addition of high-performance silicate, reaching the maximum value at an addition of 2%; the consolidation time increased with the addition of high-performance silicate.

[0087] The composite plugging agents prepared in Examples 1-7 and Comparative Example 1 have a compressive strength of 1.01 MPa when no agricultural or forestry biomass is added. As the proportion of agricultural or forestry biomass increases, the compressive strength after consolidation also increases, reaching more than 1.79 MPa when 6% is added.

[0088] The composite plugging agents prepared in Examples 1-7 and Comparative Example 3 showed that the solidification time of the plugging materials was significantly reduced without the addition of a retarder, and the amount of retarder added had little effect on the compressive strength of the composite plugging agent system.

[0089] The composite plugging agents prepared in Examples 1-7 and Comparative Example 4 showed that, without the addition of a pH adjuster, the solidification time of the plugging material increased, and the amount of retarder added had little effect on the compressive strength of the composite plugging agent system.

[0090] The composite plugging agents prepared in Examples 1-7 and Comparative Example 7 showed a significant decrease in compressive strength without the addition of itaconic acid-modified acrylate.

[0091] Figure 2 The results of this experiment measure the suspension properties of the water-blocking materials prepared in Examples 1-7 and Comparative Examples 2 and 6. The water-blocking materials prepared in Examples 1-7 and Comparative Examples 2 and 6 were used. The water separation rates of the water-blocking materials prepared in Examples 1-7 within 12 hours were 3.6%, 4.5%, 5.7%, 5.1% and 2.7%, respectively. Compared with Comparative Example 2, the present invention enhances the crosslinking ability of the water-blocking material in the oil displacement system by adding suspending agents and dispersants, and enhances the stability of the inorganic water-blocking material in the oil displacement system.

[0092] The beneficial effects of this invention are as follows:

[0093] Resource utilization and environmental protection: By using waste agricultural and forestry biomass as a key component, high-value utilization of waste is achieved, costs are reduced, and the environment is friendly.

[0094] High performance: Through the fine compounding and synergistic effect of agricultural and forestry biomass and a variety of inorganic materials, the resulting material has high compressive strength (up to 1.7 MPa or more), controllable curing time (24-48 h), and is suitable for high-temperature oil reservoir environments above 140℃.

[0095] Good stability: Through the combined action of suspending agents and dispersants, the system has high stability and low water separation rate, ensuring the uniformity and pumpability of the slurry during construction.

[0096] The synergistic mechanism is clear:

[0097] Highly active mineral admixtures: Under high temperature and pressure, they are adsorbed onto the geological rocks through van der Waals forces, forming a dense stacked structure. Their high hardness and porous structure resist erosion and lock in water.

[0098] Suspension agent: The layered silicate structure swells upon contact with water, forming a gel-like barrier.

[0099] Dispersants: They react with metal ions through functional groups to generate chain or cyclic polymers, increasing the strength of the system and preventing component aggregation.

[0100] High-performance silicates: after hydrolysis, they react with metal ions to form insoluble precipitates, creating a three-dimensional network structure.

[0101] Retarder: It delays the precipitation reaction and controls the curing time by coordinating with metal ions through phenolic hydroxyl and carboxyl groups.

[0102] Agricultural and forestry biomass: The large number of hydroxyl groups it contains enhances its adhesion to the rocks through hydrogen bonds and van der Waals forces; the organic acids produced by degradation at high temperatures can react with calcium and magnesium ions to form precipitates, further enhancing its strength.

[0103] Example embodiments have been disclosed herein, and while specific terminology has been used, it is for illustrative purposes only and should be construed as such, and is not intended to be limiting. In some instances, it will be apparent to those skilled in the art that features, characteristics, and / or elements described in conjunction with particular embodiments may be used alone, or in combination with features, characteristics, and / or elements described in conjunction with other embodiments, unless otherwise expressly indicated. Therefore, those skilled in the art will understand that various changes in form and detail may be made without departing from the scope of the invention as set forth in the appended claims.

Claims

1. An inorganic composite high-strength oil and water well plugging material, characterized in that, Made from the following raw materials by weight percentage: The ingredients include: 15%–20% highly active mineral admixtures, 2%–8% high-performance silicates, 3%–5% agricultural and forestry biomass materials, 5%–8% suspending agent, 0.5%–0.7% dispersant, 0.04%–0.05% retarder, 1%–2% reinforcing agent, 1%–2% itaconic acid modified acrylate, pH adjuster, and water. The specific surface area of ​​the highly active mineral admixture is 400-450 m². 2 / kg, and composed of the following components by mass percentage: calcium oxide 40%–55%, silicon dioxide 30%–45%, aluminum oxide 10%–20%, magnesium oxide 10%–20%, manganese oxide 0.5%–1%, ferrous oxide 0.5%–1%; The agricultural and forestry biomass material is rice husk and / or straw powder that has been mechanically ground to a particle size of 1-10 μm; and / or, the reinforcing agent is composed of the following components by mass percentage: 30%-50% lime, 30%-40% calcium carbonate, and the balance being calcium chloride, and the particle size of the reinforcing agent is 3-10 μm; The itaconic acid-modified acrylate is prepared by the following method: Itaconic acid was dissolved in deionized water, a reflux device was set up, and after stirring evenly, it was added to the polymerization reactor. Nitrogen gas was introduced for 10 minutes to remove air from the reaction system. Nitrogen gas was continuously introduced throughout the polymerization process so that the reaction was carried out under nitrogen protection. The temperature of the reaction solution was heated to the reflux temperature with stirring. Add the mixture of acrylate monomers and initiator dropwise, and continue the reaction for 1 hour to ensure the reaction is complete; After the reaction was completed, the reaction solution was cooled to room temperature, and after precipitation, filtration, washing and drying, itaconic acid modified acrylate was obtained.

2. The water-blocking material according to claim 1, characterized in that, The dispersant is composed of the following components by mass percentage: 30%–40% lignin sulfonate, 10%–30% sodium polyphosphate, and the balance being sodium dodecyl sulfonate; and / or, the retarder is composed of the following components by mass percentage: 20%–30% salicylic acid, 30%–40% tannic acid, and the balance being polymethyl methacrylate.

3. The water-blocking material according to claim 1, characterized in that, The suspending agent consists of the following components by mass percentage Composition: 40%–60% silicon dioxide, 20%–30% aluminum oxide, 10%–20% magnesium oxide, 1%–5% iron oxide, with the balance being fly ash; and / or, the pH adjuster is composed of the following components by mass percentage: 60%–75% sodium carbonate, 20%–35% sodium bicarbonate, with the balance being sodium hydroxide.

4. The water-blocking material according to claim 1, characterized in that, The reinforcing agent is composed of the following raw materials by mass fraction: 30%–50% lime, 30%–40% calcium carbonate, and the balance being calcium chloride.

5. A method for preparing the inorganic composite high-strength oil and water well plugging material as described in any one of claims 1 to 4, characterized in that, The preparation method includes the following steps: S1. Add pH adjuster, suspending agent, retarder, agricultural and forestry biomass materials, and itaconic acid modified acrylate to water, stir, and obtain mixture a; S2. Add the dispersant and high-performance silicate to the mixture a obtained in step S1, stir, and obtain mixture b; S3. Mix the highly active mineral admixture and reinforcing agent evenly to obtain mixture c; S4. Add the mixture c obtained in step S3 to the mixture b obtained in step S2, and stir to obtain the water-blocking material.

6. The preparation method according to claim 5, characterized in that, In step S1, the stirring speed is 400–600 r / min and the stirring time is 10–20 min; in step S2, the stirring speed is 400–600 r / min and the stirring time is 10–20 min; in step S4, the stirring speed is 500–700 r / min and the stirring time is 10–20 min.

7. The preparation method according to claim 6, characterized in that, The agricultural and forestry biomass materials are prepared by the following method: After cleaning and drying the raw materials of rice husks, straw and agricultural and forestry waste, the biomass raw materials are crushed using a crusher, and then screened with a vibrating screen to obtain uniform particles of 30 mesh. The pre-selected 30-mesh uniform biomass particles were placed in a Raymond mill, and the rotation speed was controlled. The process was repeated multiple times until the diameter of the raw material reached the 1-10 μm level.

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