High-temperature-resistant composite gel system for blocking low-permeability oil reservoirs and preparation method and application thereof

Abstract

The application discloses a high-temperature-resistant composite gel system for low-permeability oil reservoir plugging, which is composed of the following components: 6-30% of inorganic polymer main agent, 0.02-1% of high-molecular organic thickening agent, 0.05-2% of crosslinking agent, 0.5-5% of curing agent, 0.1-5% of reinforcing agent, and the rest of water. The application discloses a preparation method of the high-temperature-resistant composite gel system for low-permeability oil reservoir plugging, and the specific steps are as follows: the formula amount of the inorganic polymer main agent, the formula amount of the high-molecular organic thickening agent, the formula amount of the crosslinking agent, the formula amount of the curing agent and the formula amount of the reinforcing agent are respectively added into the formula amount of water, and stirring is carried out at a rotating speed of at least 400 r / min for at least 60 minutes, so that the high-temperature-resistant composite gel system for low-permeability oil reservoir plugging is obtained. The application further discloses an application of the high-temperature-resistant composite gel system for low-permeability oil reservoir plugging as a profile control water plugging agent in the exploitation of low-permeability oil reservoirs.

Description

Technical Field

[0001] This invention relates to a high-temperature resistant composite gel system for plugging low-permeability oil reservoirs, its preparation method and application, belonging to the field of oilfield chemical technology. Background Technology

[0002] Low-permeability reservoirs are crucial for increasing oil reserves and production. However, these reservoirs have low matrix permeability and severe reservoir heterogeneity. During water injection development, issues such as small water sweep area and fingering along high-permeability zones or fractures often occur, severely impacting development effectiveness. Furthermore, some low-permeability reservoirs have high formation temperatures and high salinity, significantly limiting the selection of plugging and conditioning agents.

[0003] Commonly used particulate and gel-based plugging agents in oilfields have problems such as difficulty in injection, insufficient temperature resistance, and low plugging strength when plugging and regulating low-permeability reservoirs, especially pressure-driven reservoirs.

[0004] Chinese invention patent application CN 112724947 A provides a high-temperature resistant, high-strength gel material and its application. The gel material is composed of polyacrylamide, organic crosslinking agent and water. Its system viscosity can reach 4700 mPa·s and it has good salt resistance. However, its temperature resistance is only up to 90℃, which does not meet the requirements of high-temperature oil reservoir plugging and regulation.

[0005] Chinese invention patent application CN 113025292 A discloses a high-strength gel plugging agent for sealing the horizontal wellbore before well workover in thermal recovery and its preparation method. The gelling fluid is composed of a heat-resistant polymer, partially hydrolyzed polyacrylamide, phenolic crosslinking agent, chromium crosslinking agent, oxygen scavenger, organic acid, sodium clay, and the balance water. This plugging agent is prepared from 80°C hot wastewater. At temperatures below 100°C, the gelling fluid undergoes primary crosslinking, forming a weakly crosslinked gelling fluid with a certain viscosity, possessing pumpability while preventing fluid loss to the formation and dilution upon contact with wellbore water. Above 100°C, it rapidly crosslinks to form a high-strength gel plug to seal the wellbore, preventing the leakage of hot formation fluids. It remains stable at 200°C for 3–5 days, ensuring the safety of well workover operations in thermal recovery horizontal wells. After 7 days, the gel gradually breaks down, allowing production to resume without affecting oil production efficiency. While this system has high strength, the weak crosslinking before injection results in high viscosity and a short stabilization time at high temperatures.

[0006] Chinese invention patent application CN 110003869 A discloses a fracture plugging agent based on expandable particles and solidifiable particles. This system consists of separately stored expandable particles, solidifiable particles, and a curing agent. The solidifiable particles in the system have high strength, strong temperature and salt resistance, and wide applicability to oil reservoirs. The immovable slugs formed by the solidifiable particles act as a screen, significantly increasing the breakthrough pressure gradient of the expandable particles in the fracture, thus promoting the retention of the expandable particles within the fracture and their continuous water-blocking effect. However, the particle size of this system is large, and the resulting slugs have a certain permeability, making them difficult to inject into low-permeability reservoirs.

[0007] Chinese invention patent application CN 114316931 A discloses a selective organic particulate plugging agent for high-temperature, high-salinity fractured reservoirs. It is prepared by mixing, extrusion, and shearing with an oil-soluble resin as the main agent and adding expansion agents, density regulators, dispersants, and other additives. The system has adjustable density, and the resulting particulate plugging agent exhibits good temperature and salt resistance, excellent oil-water selectivity, and a water phase plugging rate exceeding 83% and an oil phase plugging rate of approximately 15%. It shows promising application prospects in channel adjustment, water shut-off, and profile control. However, the particle size distribution of this system is between micrometers and millimeters, making it difficult to inject into low-permeability reservoirs.

[0008] In summary, existing commonly used systems suffer from poor temperature resistance and short shelf life of gels, and the injection of particulate plugging agents is difficult, making it difficult to meet the plugging and profile control needs of low-permeability oilfields. Therefore, there is an urgent need to develop a system with low injection viscosity before curing and excellent injectability and temperature resistance to provide technical support for water plugging and profile control in low-permeability reservoirs. Summary of the Invention

[0009] Technical Problem: Existing systems suffer from poor temperature resistance, difficulty in particle injection, and short shelf life, making them unsuitable for profile control and water shut-off in low-permeability reservoirs. There is an urgent need to develop a plugging and control system for low-permeability reservoirs that offers good injectability, excellent temperature resistance, and a long shelf life. To overcome these shortcomings, this invention discloses a high-temperature resistant composite gel system for plugging low-permeability reservoirs, its preparation method, and its applications.

[0010] Technical solution: A high-temperature resistant composite gel system for plugging low-permeability reservoirs, comprising the following components by mass percentage:

[0011] 6%–30% inorganic polymer main agent, 0.02%–1% high molecular weight organic thickener, 0.05%–2% crosslinking agent, 0.5%–5% curing agent, 0.1%–5% reinforcing agent, and the balance is water.

[0012] The preparation method of the high-temperature resistant composite gel system for plugging low-permeability reservoirs described above includes the following specific steps:

[0013] Add the formulated amounts of inorganic polymerizing agent, high molecular weight organic thickener, crosslinking agent, curing agent, and reinforcing agent to water respectively, and stir at a speed of at least 400 r / min for at least 60 minutes to obtain a high-temperature resistant composite gel system for plugging low-permeability oil reservoirs.

[0014] The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs was prepared using the method described above.

[0015] The above-mentioned application of high-temperature resistant composite gel system as profile control and water shut-off agent in the exploitation of low-permeability oil reservoirs.

[0016] The innovation of this invention:

[0017] 1. Inorganic materials have the characteristics of low viscosity and high temperature resistance, while organic materials have the characteristics of network structure and low dilution. Through the synergistic effect of the two, an interpenetrating double gel network is formed, so that the low-permeability oil reservoir plugging high temperature resistant composite gel system provided by the present invention has the advantages of good injectability, temperature and salt resistance, high strength, long effective period and excellent water plugging effect.

[0018] Design principle of the invention:

[0019] The inorganic polymeric agent in this invention has a low molecular weight, low viscosity after dissolving in water, and no solid components, making it easy to inject into the formation. This effectively overcomes the problem of low injection viscosity in existing plugging agent systems. Simultaneously, the curing agent in the high-temperature resistant composite gel system for plugging low-permeability reservoirs reacts and solidifies to form an inorganic polymeric gel network with high density and strength. Furthermore, the inorganic agent exhibits excellent temperature and salt resistance. Therefore, the high-temperature resistant composite gel system for plugging low-permeability reservoirs simultaneously possesses the characteristics of easy injection, temperature and salt resistance, and high strength. However, due to the system's excessively low viscosity when dissolved in water, it is easily diluted by formation water after injection, leading to a decrease in system strength.

[0020] Therefore, this invention introduces a high molecular weight organic thickener. This component has a high molecular weight and can control the viscosity of the system after dissolving in water. On the one hand, the high molecular weight organic thickener forms a network structure after hydration, which can bind the inorganic main agent and inhibit the dilution effect of formation water on the system to a certain extent, overcoming the defect that the system is easily diluted. On the other hand, the high molecular weight organic thickener can undergo a cross-linking reaction with the cross-linking agent to form a three-dimensional network structure and interpenetrate with the inorganic main agent gel network, which further increases the strength of the system and can improve the toughness and thermal stability of the system.

[0021] In addition to its curing function, the curing agent in this invention can also adjust the pH value of the high-temperature resistant composite gel system for plugging low-permeability oil reservoirs, placing the system in a weakly alkaline environment. This induces the polymerization reaction of the inorganic main agent at high temperatures, forming an inorganic gel network.

[0022] The environmentally friendly crosslinking agent in this invention crosslinks the linear network structure into a three-dimensional network structure using an organic polymer thickener, thereby enhancing the polymer's ability to inhibit system solution dilution and improve the system's curing strength.

[0023] Finally, the nanoparticles in this invention can form hydrogen bonds and van der Waals forces with the inorganic main agent and the organic polymer thickener backbone, which can further enhance the interaction forces between the network structures of the system, inhibit the thermal degradation of the system, and further improve the strength and thermal stability of the system.

[0024] Beneficial Effects: The high-temperature resistant composite gel system for plugging low-permeability reservoirs disclosed in this invention, its preparation method, and its application have the following beneficial effects:

[0025] 1. Through the synergistic effect of inorganic main agent and high molecular organic thickener, combined with the reinforcing effect of curing agent, crosslinking agent and reinforcing agent, the low-permeability oil reservoir plugging high temperature resistant composite gel system provided by the present invention overcomes the shortcomings of the existing system, and at the same time has good injectability, excellent plugging ability and long-term water shut-off ability.

[0026] 2. Indoor tests and evaluations show that the viscosity of the prepared gelling solution is less than 100 mPa·s, with excellent injection performance; after curing, it has high strength and a storage modulus greater than 100 Pa; it is resistant to temperatures up to 150℃ and salt concentrations up to 200,000 mg / L; the system has a long shelf life, with thermal stability exceeding 180 days under high temperature and high salt conditions; and indoor evaluation shows that the core water-blocking rate is higher than 95%, demonstrating excellent water-blocking effect. Detailed Implementation

[0027] The specific embodiments of the present invention are described in detail below.

[0028] The "range" disclosed in this invention is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 10–50 is listed for a specific parameter, it is also expected that ranges of 10–40 and 20–50 are also included. Furthermore, if the minimum range values ​​are 1 and 2, and the maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0–5" means that all real numbers between "0–5" have been listed herein; "0–5" is merely a shortened representation of these numerical combinations.

[0029] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0030] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0031] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0032] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0033] Unless otherwise specified, the reaction will proceed under normal temperature and pressure conditions.

[0034] Unless otherwise specified, all parts or percentages are by weight or by weight percentage.

[0035] In this invention, all the substances used are known substances that can be purchased or synthesized by known methods.

[0036] In this invention, all the devices or equipment used are conventional devices or equipment known in the art and are readily available.

[0037] The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs consists of the following components by mass percentage:

[0038] 6%–30% inorganic polymer main agent, 0.02%–1% high molecular weight organic thickener, 0.05%–2% crosslinking agent, 0.5%–5% curing agent, 0.1%–5% reinforcing agent, and the balance is water.

[0039] Furthermore, by mass percentage, it consists of the following components:

[0040] 8%–15% inorganic polymer main agent, 0.05%–0.5% high molecular weight organic thickener, 0.1%–0.2% crosslinking agent, 1%–3% curing agent, 0.5%–1% reinforcing agent, and the balance is water.

[0041] Furthermore, the inorganic polymerization agent is one or more of polyaluminum chloride, modified aluminum chloride, sodium silicate, and potassium silicate, preferably polyaluminum chloride.

[0042] Furthermore, the basicity of the polyaluminum chloride is 40% to 85%.

[0043] Furthermore, the polymeric organic thickener is one or more of the following: partially hydrolyzed polyacrylamide, polyacrylamide, acrylamide / 2-acrylamide-2-methylpropanesulfonic acid copolymer, acrylamide / N-vinylpyrrolidone copolymer, and acrylamide / 2-acrylamide-2-methylpropanesulfonic acid / N-vinylpyrrolidone copolymer.

[0044] Furthermore, the molecular weight of the polymeric organic thickener is 8 million to 15 million.

[0045] Further, the crosslinking agent is one or more of chromium chloride, chromium acetate, zirconium oxychloride, polyethyleneimine, hydroxylamine, water-soluble phenolic resin, and hydroquinone / urotropine composite crosslinking agent, preferably polyethyleneimine.

[0046] Furthermore, the molecular weight of the crosslinking agent is 5000 to 20000.

[0047] Furthermore, the curing agent is one or more of urea, sodium carbonate, sodium bicarbonate, sodium dihydrogen phosphate, potassium carbonate, and potassium bicarbonate, preferably urea.

[0048] Furthermore, the reinforcing agent is one or more of nano-silica particles, nano-alumina particles, nano-iron oxide particles, nano-magnesium oxide, and nano-bentonite, preferably nano-silica particles.

[0049] Furthermore, the median particle size of the reinforcing agent is 10–50 nm.

[0050] The preparation method of the high-temperature resistant composite gel system for plugging low-permeability reservoirs described above includes the following specific steps:

[0051] Add the formulated amounts of inorganic polymerizing agent, high molecular weight organic thickener, crosslinking agent, curing agent, and reinforcing agent to water respectively, and stir at a speed of at least 400 r / min for at least 60 minutes to obtain a high-temperature resistant composite gel system for plugging low-permeability oil reservoirs.

[0052] The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs was prepared using the method described above.

[0053] The above-mentioned application of high-temperature resistant composite gel system as profile control and water shut-off agent in the exploitation of low-permeability oil reservoirs.

[0054] In one embodiment:

[0055] The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs consists of the following components by mass percentage:

[0056] 6% inorganic polymer main agent, 0.02% high molecular weight organic thickener, 0.05% crosslinking agent, 0.5% curing agent, 0.1% reinforcing agent, and the balance is water.

[0057] In other embodiments, the low-permeability reservoir plugging method utilizes a high-temperature resistant composite gel system, which, by mass percentage, comprises the following components:

[0058] 8% inorganic polymer main agent, 0.05% high molecular weight organic thickener, 0.1% crosslinking agent, 1% curing agent, 0.5% reinforcing agent, and the balance is water.

[0059] Furthermore, the basicity of the polyaluminum chloride is 40%. In other embodiments, the basicity of the polyaluminum chloride is 85%. In other embodiments, the basicity of the polyaluminum chloride is 65%.

[0060] Furthermore, the inorganic polymerization agent is polyaluminum chloride.

[0061] Furthermore, the polymeric organic thickener is partially hydrolyzed polyacrylamide.

[0062] Furthermore, the molecular weight of the polymeric organic thickener is 8 million.

[0063] Furthermore, the crosslinking agent is chromium chloride.

[0064] Furthermore, the crosslinking agent has a molecular weight of 5000.

[0065] Furthermore, the curing agent is urea.

[0066] Furthermore, the reinforcing agent is nano-silica particles.

[0067] Furthermore, the median particle size of the reinforcing agent is 10 nm.

[0068] The preparation method of the high-temperature resistant composite gel system for plugging low-permeability reservoirs described above includes the following specific steps:

[0069] Add the formulated amounts of inorganic polymerizing agent, high molecular weight organic thickener, crosslinking agent, curing agent, and reinforcing agent to water respectively, and stir at 400 r / min for 240 minutes to obtain a high-temperature resistant composite gel system for plugging low-permeability oil reservoirs.

[0070] The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs was prepared using the method described above.

[0071] The above-mentioned application of high-temperature resistant composite gel system as profile control and water shut-off agent in the exploitation of low-permeability oil reservoirs.

[0072] In another embodiment:

[0073] The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs consists of the following components by mass percentage:

[0074] 30% inorganic polymer main agent, 1% high molecular weight organic thickener, 2% crosslinking agent, 5% curing agent, 5% reinforcing agent, and the balance is water.

[0075] In other embodiments, the low-permeability reservoir plugging method utilizes a high-temperature resistant composite gel system, which, by mass percentage, comprises the following components:

[0076] 15% inorganic polymer main agent, 0.5% high molecular weight organic thickener, 0.2% crosslinking agent, 3% curing agent, 1% reinforcing agent, and the balance is water.

[0077] Furthermore, the inorganic polymerization agent is modified aluminum chloride.

[0078] Furthermore, the polymeric organic thickener is polyacrylamide.

[0079] Furthermore, the molecular weight of the polymeric organic thickener is 15 million.

[0080] Furthermore, the crosslinking agent is chromium acetate.

[0081] Furthermore, the crosslinking agent has a molecular weight of 20,000.

[0082] Furthermore, the curing agent is sodium carbonate.

[0083] Furthermore, the reinforcing agent is nano-alumina particles.

[0084] Furthermore, the median particle size of the reinforcing agent is 50 nm.

[0085] The preparation method of the high-temperature resistant composite gel system for plugging low-permeability reservoirs described above includes the following specific steps:

[0086] Add the formulated amounts of inorganic polymerizing agent, high molecular weight organic thickener, crosslinking agent, curing agent, and reinforcing agent to water respectively, and stir at 800 r / min for 60 minutes to obtain a high-temperature resistant composite gel system for plugging low-permeability oil reservoirs.

[0087] The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs was prepared using the method described above.

[0088] The above-mentioned application of high-temperature resistant composite gel system as profile control and water shut-off agent in the exploitation of low-permeability oil reservoirs.

[0089] In yet another embodiment:

[0090] The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs consists of the following components by mass percentage:

[0091] 10% inorganic polymer main agent, 0.3% high molecular weight organic thickener, 0.15% crosslinking agent, 2% curing agent, 0.8% reinforcing agent, and the balance is water.

[0092] Further, the inorganic polymerization main agent is sodium silicate. In other embodiments, the inorganic polymerization main agent is potassium silicate. In other embodiments, the inorganic polymerization main agent is a mixture of polyaluminum chloride, modified aluminum chloride, sodium silicate, and potassium silicate in equal mass ratios.

[0093] Further, the polymeric organic thickener is an acrylamide / 2-acrylamide-2-methylpropanesulfonic acid copolymer. In other embodiments, the polymeric organic thickener is an acrylamide / N-vinylpyrrolidone copolymer. In other embodiments, the polymeric organic thickener is an acrylamide / 2-acrylamide-2-methylpropanesulfonic acid / N-vinylpyrrolidone copolymer. In other embodiments, the polymeric organic thickener is a mixture of partially hydrolyzed polyacrylamide, polyacrylamide, acrylamide / 2-acrylamide-2-methylpropanesulfonic acid copolymer, acrylamide / N-vinylpyrrolidone copolymer, and acrylamide / 2-acrylamide-2-methylpropanesulfonic acid / N-vinylpyrrolidone copolymer in equal mass ratios.

[0094] Furthermore, the molecular weight of the polymeric organic thickener is 12 million.

[0095] Further, the crosslinking agent is polyethyleneimine. In other embodiments, the crosslinking agent is zirconium oxychloride. In other embodiments, the crosslinking agent is hydroxylamine. In other embodiments, the crosslinking agent is a water-soluble phenolic resin. In other embodiments, the crosslinking agent is a hydroquinone / hexamethylenetetramine composite crosslinker. In other embodiments, the crosslinking agent is a mixture of chromium chloride, chromium acetate, zirconium oxychloride, polyethyleneimine, hydroxylamine, water-soluble phenolic resin, and hydroquinone / hexamethylenetetramine composite crosslinking agent in equal mass ratios.

[0096] Furthermore, the crosslinking agent has a molecular weight of 10,000.

[0097] Further, the curing agent is sodium bicarbonate. In other embodiments, the curing agent is sodium dihydrogen phosphate. In other embodiments, the curing agent is potassium carbonate. In other embodiments, the curing agent is potassium bicarbonate. In other embodiments, the curing agent is a mixture of urea, sodium carbonate, sodium bicarbonate, sodium dihydrogen phosphate, potassium carbonate, and potassium bicarbonate in equal mass ratios.

[0098] Further, the reinforcing agent is nano-iron oxide particles. In other embodiments, the reinforcing agent is nano-magnesium oxide. In other embodiments, the reinforcing agent is nano-bentonite. In other embodiments, the reinforcing agent is a mixture of nano-silica particles, nano-alumina particles, nano-iron oxide particles, nano-magnesium oxide, and nano-bentonite in equal mass ratios.

[0099] Furthermore, the median particle size of the reinforcing agent is 30 nm.

[0100] The preparation method of the high-temperature resistant composite gel system for plugging low-permeability reservoirs described above includes the following specific steps:

[0101] Add the formulated amounts of inorganic polymerizing agent, high molecular weight organic thickener, crosslinking agent, curing agent, and reinforcing agent to water respectively, and stir at 1200 r / min for 80 minutes to obtain a high-temperature resistant composite gel system for plugging low-permeability oil reservoirs.

[0102] The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs was prepared using the method described above.

[0103] The above-mentioned application of high-temperature resistant composite gel system as profile control and water shut-off agent in the exploitation of low-permeability oil reservoirs.

[0104] Example 1:

[0105] The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs consists of the following components by mass percentage:

[0106] 8% polyaluminum chloride, 0.05% heat-resistant polymer, 0.1% environmentally friendly crosslinking agent, 1% curing agent, 0.5% nanoparticles, 90.35% water.

[0107] Furthermore, the basicity of polyaluminum chloride is 80%;

[0108] Furthermore, the heat-resistant polymer is an acrylamide / 2-acrylamide-2-methylpropanesulfonic acid copolymer with a molecular weight of 10 million;

[0109] Furthermore, the environmentally friendly crosslinking agent is a polyethyleneimine crosslinking agent with a molecular weight of 10,000;

[0110] Furthermore, the curing agent is urea;

[0111] Furthermore, the nanoparticles are acidic silica with a median particle size of 15 nm.

[0112] Furthermore, after weighing the above components according to the proportions and mixing them, the mixture is stirred for 60 minutes at a speed of 400 r / min using an electric stirrer to obtain the low-permeability reservoir plugging high-temperature resistant gel system described in this invention.

[0113] Example 2:

[0114] The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs consists of the following components by mass percentage:

[0115] 15% polyaluminum chloride, 0.1% heat-resistant polymer, 0.2% environmentally friendly crosslinking agent, 3% curing agent, 1% nanoparticles, 80.7% water.

[0116] Furthermore, the basicity of polyaluminum chloride is 70%;

[0117] Furthermore, the heat-resistant polymer is an acrylamide / 2-acrylamide-2-methylpropanesulfonic acid copolymer with a molecular weight of 15 million;

[0118] Furthermore, the environmentally friendly crosslinking agent is a polyethyleneimine crosslinking agent with a molecular weight of 5000;

[0119] Furthermore, the curing agent is urea;

[0120] Furthermore, the nanoparticles are acidic silica with a median particle size of 15 nm.

[0121] Furthermore, after weighing the above components according to the proportions and mixing them, the mixture is stirred for 60 minutes at a speed of 400 r / min using an electric stirrer to obtain the low-permeability reservoir plugging high-temperature resistant gel system described in this invention.

[0122] Example 3:

[0123] The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs consists of the following components by mass percentage:

[0124] 12% polyaluminum chloride, 0.08% heat-resistant polymer, 0.15% environmentally friendly crosslinking agent, 2% curing agent, 0.8% nanoparticles, 84.97% water.

[0125] Furthermore, the basicity of polyaluminum chloride is 80%;

[0126] Furthermore, the heat-resistant polymer is an acrylamide / 2-acrylamide-2-methylpropanesulfonic acid copolymer with a molecular weight of 12 million;

[0127] Furthermore, the environmentally friendly crosslinking agent is a polyethyleneimine crosslinking agent with a molecular weight of 10,000;

[0128] Furthermore, the curing agent is urea;

[0129] Furthermore, the nanoparticles are acidic silica with a median particle size of 15 nm.

[0130] Furthermore, after weighing the above components according to the proportions and mixing them, the mixture is stirred for 60 minutes at a speed of 400 r / min using an electric stirrer to obtain the low-permeability reservoir plugging high-temperature resistant gel system described in this invention.

[0131] Example 4:

[0132] The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs consists of the following components by mass percentage:

[0133] 8% polyaluminum chloride, 0.05% heat-resistant polymer, 0.1% environmentally friendly crosslinking agent, 1% curing agent, 0.5% nanoparticles, 90.35% water.

[0134] Furthermore, the basicity of polyaluminum chloride is 80%;

[0135] Furthermore, the heat-resistant polymer is an acrylamide / N-vinylpyrrolidone copolymer with a molecular weight of 8 million;

[0136] Furthermore, the environmentally friendly crosslinking agent is a polyethyleneimine crosslinking agent with a molecular weight of 20,000;

[0137] Furthermore, the curing agent is urea;

[0138] Furthermore, the nanoparticles are acidic silica with a median particle size of 15 nm.

[0139] Furthermore, after weighing the above components according to the proportions and mixing them, the mixture is stirred for 60 minutes at a speed of 400 r / min using an electric stirrer to obtain the low-permeability reservoir plugging high-temperature resistant gel system described in this invention.

[0140] Comparative Example 1:

[0141] A commonly used oilfield gel-based water shut-off agent, comprising the following components by weight percentage:

[0142] 1% polymer, 0.4% organic crosslinking agent, 0.5% nanoparticles and 98.1% water.

[0143] Furthermore, the polymer is partially hydrolyzed polyacrylamide;

[0144] Furthermore, the organic crosslinking agent is a water-soluble phenolic resin crosslinking agent;

[0145] Furthermore, the nanoparticles are nano-silica;

[0146] Furthermore, after weighing the above components according to the proportions and mixing them, stir with an electric mixer at a speed of 400 r / min for 60 minutes to obtain a gel-type water shut-off agent commonly used in oil fields.

[0147] Comparative Example 2:

[0148] A commonly used particulate plugging agent in oil fields, comprising the following components by mass percentage:

[0149] 5% granules, 5% curable granules, 1% curing agent, 4% suspending agent and 85% water.

[0150] Furthermore, the particles are a mixture of water-swellable particles and walnut shell particles;

[0151] Furthermore, the curable particles are thermosetting resin particles;

[0152] Furthermore, the curing agent is a resin binder;

[0153] Furthermore, the suspending agent is nano-bentonite;

[0154] Furthermore, after weighing the above components according to the proportions and mixing them, stir them with an electric stirrer at a speed of 400 r / min for 60 minutes to obtain the granular water shut-off agent commonly used in oil fields.

[0155] Performance testing

[0156] The viscosity, post-curing strength, thermal stability, and sealing ability of the plugging and conditioning systems prepared in the above embodiments and comparative examples were evaluated.

[0157] The injection performance of the system is characterized by the viscosity of the system solution, and the evaluation method is as follows:

[0158] The viscometer was used to measure the viscosity of the homogeneously prepared sample of this invention at 25°C for 7.34 s. -1 The viscosity value below.

[0159] The strength of the system is characterized by its storage modulus after curing, and the measurement method is as follows:

[0160] The prepared solution was sealed in a metal aging vessel and then aged in a 150°C oven for one day. After the system solidified, the oven was turned off, and the sample was allowed to cool to room temperature before the elastic modulus of the system was measured using a rheometer.

[0161] The temperature resistance and shelf life of the system are characterized by the dehydration rate after aging at 150°C for 180 days. The lower the dehydration rate, the better the thermal stability and the longer the shelf life. The evaluation method is as follows:

[0162] Weigh a certain mass of the system solution, seal it in a metal aging tank, and then place it in a 150℃ oven for aging. Every once in a while, take out the cooled aging tank and observe whether water is released after the system solidifies. Use the dehydration rate to evaluate the thermal stability of the system. The dehydration rate after the system has been aged for a period of time is calculated as the ratio of the mass of water released to the mass of the initial solution.

[0163] The system's plugging capacity is characterized by its water-blocking rate in the core sample. A higher water-blocking rate indicates a stronger plugging capacity. The evaluation method is as follows:

[0164] The plugging ability of the plugging agent system in the core was evaluated using a physical model experimental setup. The setup consisted of a 25cm long model with an inner diameter of 2.5cm and a permeability of approximately 50×10⁻⁶. -3 μm 2 The test was conducted under simulated conditions of 150℃ and 100,000 mg / L formation water salinity. In the experiment, the test system was injected into a rock core, and after the system solidified, the pressure difference between the two ends of the core was measured. The permeability after the system plugged the core was then calculated; the plugging rate was derived from the permeability before and after plugging.

[0165] The experimental results are shown in Table 1. It can be seen that the viscosity of the high-temperature resistant composite gel system solution used for plugging low-permeability reservoirs in Examples 1-3 is low, all below 50 mPa·s, with excellent injection performance, high elastic modulus (strength), all greater than 120 Pa, and a dehydration rate of less than 5% after heat treatment at 150℃ for 180 days, with excellent stability and a water plugging rate of more than 95%, demonstrating excellent water plugging effect.

[0166] The viscosity of the system solution increases with the increase of heat-resistant polymer and crosslinking agent. The strength of the system after curing increases with the increase of polyaluminum chloride, curing agent and heat-resistant polymer.

[0167] Because the system contains organic components such as heat-resistant polymers, a small amount of dehydration occurs after high-temperature heat treatment, but the volume of the plugging and conditioning system remains basically unchanged, which does not affect the plugging and conditioning effect.

[0168] The performance of commonly used oilfield water shut-off agents, namely gel-based and granular-based agents, was evaluated in the comparative studies.

[0169] In Comparative Example 1, the gel-based water shut-off agent solution had high initial viscosity and low strength after curing. After aging at 150℃ for 180 days, it suffered severe dehydration with a dehydration rate as high as 45%. The water shut-off rate in the fractured core was low, and it was generally unsuitable for water shut-off in high-temperature, low-permeability oil reservoirs.

[0170] In Comparative Example 2, the particulate plugging agent showed good thermal stability, but it was in a dispersed state and lacked accurate strength data. In addition, the viscosity of the injected base liquid was too high, causing the particles to be filtered out during core injection and forming a filter cake at the injection end, making it difficult to inject into the core fractures to form an effective seal.

[0171] Table 1 Comparison of system performance in the examples and comparative examples.

[0172]

[0173]

[0174] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A high-temperature resistant composite gel system for plugging low-permeability oil reservoirs, characterized in that, It consists of the following components by weight percentage: 6%–30% inorganic polymer main agent, 0.02%–1% high molecular weight organic thickener, 0.05%–2% crosslinking agent, 0.5%–5% curing agent, 0.1%–5% reinforcing agent, and the balance is water.

2. The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs as described in claim 1, characterized in that, It consists of the following components by weight percentage: 8%–15% inorganic polymer main agent, 0.05%–0.5% high molecular weight organic thickener, 0.1%–0.2% crosslinking agent, 1%–3% curing agent, 0.5%–1% reinforcing agent, and the balance is water.

3. The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs as described in claim 1 or 2, characterized in that, The inorganic polymerization agent is one or more of polyaluminum chloride, modified aluminum chloride, sodium silicate, and potassium silicate, preferably polyaluminum chloride, and / or The basicity of the polyaluminum chloride is 40% to 85%.

4. The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs as described in claim 1 or 2, characterized in that, The polymeric organic thickener is one or more of the following: partially hydrolyzed polyacrylamide, polyacrylamide, acrylamide / 2-acrylamide-2-methylpropanesulfonic acid copolymer, acrylamide / N-vinylpyrrolidone copolymer, acrylamide / 2-acrylamide-2-methylpropanesulfonic acid / N-vinylpyrrolidone copolymer, and / or The molecular weight of the polymeric organic thickener is 8 million to 15 million.

5. The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs as described in claim 1 or 2, characterized in that, The crosslinking agent is one or more of chromium chloride, chromium acetate, zirconium oxychloride, polyethyleneimine, hydroxylamine, water-soluble phenolic resin, and hydroquinone / urotropine composite crosslinking agent, preferably polyethyleneimine, and / or The molecular weight of the crosslinking agent is 5000 to 20000.

6. The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs as described in claim 1 or 2, characterized in that, The curing agent is one or more of urea, sodium carbonate, sodium bicarbonate, sodium dihydrogen phosphate, potassium carbonate, and potassium bicarbonate, preferably urea.

7. The high-temperature resistant composite gel system for plugging low-permeability oil reservoirs as described in claim 1 or 2, characterized in that, The reinforcing agent is one or more of nano-silica particles, nano-alumina particles, nano-iron oxide particles, nano-magnesium oxide, and nano-bentonite, preferably nano-silica particles, and / or The median particle size of the reinforcing agent is 10–50 nm.

8. The method for preparing the high-temperature resistant composite gel system for plugging low-permeability oil reservoirs according to any one of claims 1-7, characterized in that, The specific steps are as follows: Add the formulated amounts of inorganic polymerizing agent, high molecular weight organic thickener, crosslinking agent, curing agent, and reinforcing agent to water respectively, and stir at a speed of at least 400 r / min for at least 60 minutes to obtain a high-temperature resistant composite gel system for plugging low-permeability oil reservoirs.

9. A high-temperature resistant composite gel system for plugging low-permeability oil reservoirs, characterized in that: It is prepared by the method described in claim 8.

10. The application of the high-temperature resistant composite gel system for plugging low-permeability reservoirs as a profile control and water shut-off agent in the exploitation of low-permeability reservoirs, according to any one of claims 1-7 and 9.

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