A profile control and water plugging agent

Abstract

The present invention relates to a profile-control and water-blocking agent, and belongs to the technical field of oil and gas field chemicals. The profile-control and water-blocking agent of the present invention utilizes the super-strong water-absorbing property of the bulk-swelling particles to absorb a large amount of profile-control and water-blocking liquid, causing partial expansion. Since the bulk-swelling particles are coated with a water-soluble coating layer, the profile-control and water-blocking liquid will not be released during the injection process. After the profile-control and water-blocking agent of the present invention is injected into the formation and accumulates in the formation, the water-soluble coating layer wrapped on the outside dissolves in water at the formation temperature, and the bulk-swelling particles begin to absorb water and swell, forming an accumulation, blocking the dominant channel; at the same time, the profile-control and water-blocking liquid in the bulk-swelling particles is released and dissolved in the surrounding water environment of the bulk-swelling particles under the action of the concentration difference. Under the action of the formation temperature, the profile-control and water-blocking liquid undergoes a polymerization reaction to generate a three-dimensional network solid, so that the accumulated bulk-swelling particles and the bulk-swelling particles and the formation rocks are cemented into one, thereby achieving the scouring resistance of the profile-control and water-blocking agent and improving the effective time of the action.

Description

Technical Field

[0001] The invention relates to a profile control and water plugging agent, belonging to the technical field of oil and gas field chemicals. Background Art

[0002] With waterflooding, heterogeneous oil and gas fields become more heterogeneous, forming dominant flow channels along which the injected water "rushes," increasing the water cut in the oil and gas wells and reducing the waterflood sweep volume and recovery rate. To increase the waterflood sweep volume and recovery rate, these dominant flow channels must be blocked, causing the injected water to "circumvent" and redirect the injected water. Commonly used technologies can be divided into two categories: mechanical and chemical. Depending on the application, they are designated as mechanical stratified water injection for water injection wells and mechanical stratified water shutoff for oil and gas production wells; and chemical profile control and chemical water shutoff for water injection wells and oil and gas production wells. However, because mechanical stratified water injection and stratified water shutoff require the use of tools, they are often limited by well conditions and tubing. Chemical profile control and water shutoff, on the other hand, simply requires the injection of chemical profile control and water shutoff agents into the reservoir. This facilitates application and is not limited by well conditions or tubing, making it a commonly used technology.

[0003] Chemical profile control and water plugging technologies can be categorized as chemical reaction-based and physical accumulation-based based on their mechanism of action. Chemical reaction-based profile control and water plugging fluids primarily consist of a first polymerizable monomer (a polymerizable monomer with one ethylenically unsaturated double bond, such as acrylic acid or acrylamide), a second polymerizable monomer (a polymerizable monomer with at least two ethylenically unsaturated double bonds, such as N,N-methylenebisacrylamide), and an initiator. These polymerize beneath the formation to form a plug for water plugging. However, because the reaction takes time and is significantly affected by formation conditions (temperature, salinity, and water), success is often limited. Physical accumulation-based profile control and water plugging agents primarily utilize bulk-swelling particles. These bulk-swelling particles (also known as gel particles, elastic particles, or water-swelling particles) can be adjusted over a wide range of composition, additives, and particle size, making them adaptable to reservoirs with varying conditions (temperature, salinity, and pore throat size), making them a commonly used profile control and water plugging agent for continental caustic oil reservoirs. Volume-swelling particles are a solid material with a three-dimensional network, synthesized on the surface. They are typically produced through the polymerization reaction of a chain-extending monomer (a monomer with one ethylenically unsaturated double bond, such as acrylic acid or acrylamide), a cross-linking monomer (a monomer with at least two ethylenically unsaturated double bonds, such as N,N-methylenebisacrylamide), and an initiator. Volume-swelling particles exhibit excellent water absorption and swelling properties (expansion multiples exceeding 5). After injection into the formation and entering the dominant flow channel, the particles absorb water, swell, and accumulate to block the dominant channel, achieving profile control and water blocking in the injection-production well. However, after entering the dominant flow channel, due to low or no water content, the particles absorb little or no water and do not accumulate to block the channel, demonstrating a certain degree of selectivity in channel blocking. By adding various fillers (such as organic fibers and inorganic particles) during the synthesis process, volume-swelling particles can adapt to different reservoir conditions (temperatures up to 140°C, mineralization up to 30×10 4 mg / L) with different plugging strength requirements. Depending on the size of the reservoir pore channels, bulk-swelling particles can be manufactured in millimeter or micron sizes. However, since bulk-swelling particles themselves are non-reactive, they simply physically accumulate after injection into the formation, making them easily dispersed by the injected water and removed from oil and gas wells, resulting in a short-lived solution.

[0004] To extend the duration of action and shelf life of profile-modifying water-blocking agents, Chinese patent document CN115651421A discloses a controlled-release grouting and water-blocking material, its preparation method, and its application. This controlled-release grouting and water-blocking material consists of a water-absorbing, swellable core and a water-soluble, slow-release coating. The swellable core is formed by mixing bentonite, high-volume-swelling particles, and xanthan gum, and then granulating it using a disc granulator, leveraging the xanthan gum's cohesive properties. The water-soluble slow-release coating is formed by applying a film-forming solution to the swellable core using a coating machine and then drying it. The patent document applies a layer of slow-release coating to the surface of the swellable core using a coating machine. The coating thickness is adjusted by controlling the mass ratio of the coating film-forming solution to the swellable core particles, achieving a controllable onset of water absorption within the swellable core. However, the grouting water blocking material disclosed in the patent document still has the problem of being washed away by water flow and becoming ineffective. Summary of the Invention

[0005] The purpose of the present invention is to provide a profile control and water plugging agent, which can solve the problem of short effective period of the current bulk-expanding granular profile control and water plugging agent.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the profile control and water plugging agent of the present invention is:

[0007] A profile control and water plugging agent comprises bulky particles and a water-soluble coating layer covering the bulky particles, wherein the bulky particles are adsorbed with a profile control and water plugging liquid; and the mass ratio of the bulky particles to the profile control and water plugging liquid is 2:(6-12).

[0008] The profile-control and water-blocking agent of the present invention utilizes the super-strong water-absorbing properties of the bulk-swelling particles to absorb a large amount of profile-control and water-blocking liquid, causing partial expansion. Since the bulk-swelling particles are coated with a water-soluble coating layer, the profile-control and water-blocking liquid will not be released during the injection process. After the profile-control and water-blocking agent of the present invention is injected into the formation and accumulates in the formation, the water-soluble coating layer on the outside dissolves in water at the formation temperature, and the bulk-swelling particles begin to absorb water and expand, forming an accumulation, blocking the dominant channel; at the same time, the profile-control and water-blocking liquid in the bulk-swelling particles is released and dissolved in the surrounding water environment of the bulk-swelling particles under the action of the concentration difference. Under the action of the formation temperature, the profile-control and water-blocking liquid undergoes a polymerization reaction to generate a three-dimensional network solid, so that the accumulated bulk-swelling particles and the bulk-swelling particles and the formation rocks are cemented into one, thereby achieving the scour resistance of the profile-control and water-blocking agent and increasing the effective time of the action. However, the amount of profile control and water plugging agents entering non-dominant channels is small, preventing accumulation. Furthermore, due to high oil saturation and low water content, the water-soluble coating layer either remains insoluble or, if dissolved, the bulk-swelling particles cannot fully expand, preventing the release of the profile control and water plugging fluid. These two factors prevent blockage in non-dominant channels, demonstrating a degree of selectivity. Furthermore, by selecting different bulk-swelling particle types, different plugging strength requirements can be achieved under different formation temperatures.

[0009] If the amount of profile control and water plugging fluid used is too small, after the bulk-swelling particles accumulate, the release concentration of the profile control and water plugging fluid in the surrounding water is low, no polymerization reaction occurs, or the three-dimensional network strength generated by the polymerization reaction is weak; if the amount of profile control and water plugging fluid used is too large, the water absorption and expansion performance of the bulk-swelling particles themselves will decrease, and the size increase after injection into the formation will be small, making it difficult for them to accumulate in the dominant channel.

[0010] In the present invention, the bulking particles refer to polymer particle profile control and water plugging agents. Any polymer particle profile control and water plugging agent suitable for oil and gas fields can be used as the bulking particles of the present invention. The bulking particles can be prepared by themselves or commercially available products can be used. Commercially available products suitable for the bulking particles of the present invention include: bulking particles CQKL-1 (white and translucent), bulking particles (white and translucent), drilling bulking plugging agent (light yellow), slow expansion profile control agent for oil production (light yellow), new plugging agent HJK-3 produced by Kaifeng Hengju Biological Co., Ltd., pre-crosslinked bulking agent particles for drilling fluid profile control agent, water plugging agent and plugging agent (light yellow) produced by Hebei Yanxing Chemical Co., Ltd. and pre-crosslinked bulking particles (white and translucent, light yellow) produced by Jinan Dongfeng Chemical Co., Ltd. In order to reduce costs and ensure the stability of raw materials, preferably, the bulking particles are mainly prepared by polymerization reaction of chain extension polymerization monomers and cross-linking polymerization monomers, and the chain extension polymerization monomers are selected from one or any combination of styrene sulfonate, 2-acrylamido-2-methylpropane sulfonate, acrylamide monomers, and acrylic acid monomers.

[0011] Preferably, the cross-linking polymerization monomer is N,N-methylenebisacrylamide and / or polyethylene glycol diacrylate. Preferably, the polyethylene glycol diacrylate is polyethylene glycol 400 diacrylate or polyethylene glycol 700 diacrylate.

[0012] Preferably, the bulking particles are prepared by a method comprising the following steps: polymerizing a chain extending polymerization monomer, a cross-linking polymerization monomer and an initiator in water. Preferably, the mass ratio of the chain extending polymerization monomer, the cross-linking polymerization monomer and the initiator is (35-40): (0.3-0.5): (0.6-1). For example, the mass ratio of the chain extending polymerization monomer, the cross-linking polymerization monomer and the initiator is 35:0.3:0.6. Preferably, the initiator used in the preparation method of the bulking particles is composed of a water-soluble persulfate and a water-soluble sulfite. For example, the initiator used in the preparation method of the bulking particles is composed of ammonium persulfate and sodium sulfite. Preferably, the temperature of the polymerization reaction carried out in the preparation method of the bulking particles is not lower than 30°C, and the time is not less than 24 hours.

[0013] The particle size of the bulk-swelling particles can be selected based on the pore throat size of the dominant water flow channel, i.e., the particle size of the bulk-swelling particles is 1 / 3 to 1 / 9 of the pore throat size of the dominant water flow channel. Preferably, the particle size of the bulk-swelling particles is nanometer-scale, micrometer-scale, or millimeter-scale. More preferably, the particle size of the bulk-swelling particles is 0.1 to 10 mm. For example, the particle size of the bulk-swelling particles is 1 to 2 mm.

[0014] Preferably, the profile control and water plugging fluid comprises a water-soluble polymerizable monomer, an initiator and water, wherein the water-soluble polymerizable monomer comprises a first polymerizable monomer and a second polymerizable monomer, wherein the first polymerizable monomer has one ethylenically unsaturated double bond, and the second polymerizable monomer has at least two ethylenically unsaturated double bonds.

[0015] The first polymerizable monomer is used to provide a basic skeleton of the product obtained by the subsequent polymerization. Preferably, the first polymerizable monomer is selected from one or any combination of p-styrene sulfonate, 2-acrylamido-2-methylpropane sulfonate, acrylamide monomers, and acrylic acid monomers.

[0016] Preferably, the acrylamide monomer used to prepare the bulk-swelling particles and the acrylamide monomer used to form the profile control and water plugging fluid are each independently selected from one or any combination of acrylamide, methacrylamide, and N,N-dimethylacrylamide. Preferably, the acrylic acid monomer used to prepare the bulk-swelling particles and the acrylic acid monomer used to form the profile control and water plugging fluid are each independently selected from one or any combination of acrylic acid, methacrylic acid, acrylic acid salts, methacrylic acid salts, hydroxyethyl methacrylate, and hydroxyethyl acrylate.

[0017] The second polymerizable monomer is used to provide a certain degree of crosslinking to the product obtained by subsequent polymerization to improve the strength of the product. Preferably, the second polymerizable monomer is N,N-methylenebisacrylamide and / or polyethylene glycol diacrylate. Further preferably, the second polymerizable monomer is selected from one or any combination of N,N-methylenebisacrylamide, polyethylene glycol 400 diacrylate, and polyethylene glycol 700 diacrylate.

[0018] Preferably, in the profile control and water plugging fluid, the mass ratio of the first polymerizable monomer to the second polymerizable monomer is (30-40):(0.1-0.5). Excessive use of the second polymerizable monomer will result in poor toughness and shear resistance in the three-dimensional network structure generated underground, i.e., weak resistance to injection water scouring. Excessive use of the second polymerizable monomer will result in low strength and vulnerability to high injection pressure differentials in the three-dimensional network structure generated underground.

[0019] Preferably, in the profile control and water plugging fluid, the mass ratio of the first polymerizable monomer to water is (30-40):(60-65). Excessive water usage will result in less water-soluble polymerizable monomer being released into the formation after the bulk-swelling particles accumulate, resulting in the failure to form a three-dimensional network structure underground or a low-strength three-dimensional network structure being formed. Excessive water usage will cause some of the water-soluble polymerizable monomer to precipitate on the surface of the bulk-swelling particles during the preparation of the profile control and water plugging agent.

[0020] The type of initiator in the profile control and water plugging fluid can be selected according to the type of polymerized monomer and the operating temperature requirements. Preferably, the initiator in the profile control and water plugging fluid is a water-soluble initiator. Preferably, the water-soluble initiator in the profile control and water plugging fluid is a persulfate. Preferably, the persulfate in the profile control and water plugging fluid is selected from one or any combination of ammonium persulfate, potassium persulfate, sodium persulfate, and calcium persulfate. Compared with other water-soluble initiators, persulfate initiators have the advantages of low price, good water solubility, the ability to form a uniform aqueous solution with water-soluble monomers, and no precipitation and stratification. In addition, they can be absorbed by the bulk-swelling particles simultaneously with the water-soluble polymerized monomers during the preparation of the profile control and water plugging agent.

[0021] Preferably, in the profile control and water plugging fluid, the mass ratio of the first polymerization monomer to the initiator is (30-40):(0.02-0.04). Excessive use of initiator will result in an excessively rapid reaction rate, a short time for the underground three-dimensional network structure to form, insufficient reaction, and poor structural performance. Excessive use of initiator will result in the failure to form a three-dimensional network structure underground or a prolonged period of time for the three-dimensional network structure to form, causing the chain extension monomer to be diluted by formation water and a decrease in strength.

[0022] In order to ensure the safety during the injection of the profile control and water plugging agent and prevent the profile control and water plugging liquid from releasing and reacting in the wellbore to cause blockage, preferably, the profile control and water plugging liquid also includes a polymerization inhibitor. Preferably, the polymerization inhibitor is a water-soluble polymerization inhibitor. For example, the polymerization inhibitor is selected from one or any combination of ferric ferrocyanide, ferric chloride, and copper chloride. Preferably, the mass ratio of the first polymerization monomer and the polymerization inhibitor is (30-40): (0.01-0.05). If the amount of polymerization inhibitor is too much, the polymerization reaction will be delayed for a long time, resulting in the dilution of the water-soluble polymerization monomer by the formation water, and the three-dimensional network structure will not be generated underground or the strength of the generated three-dimensional network structure will be low; if the amount of polymerization inhibitor is too little, when the reactive substance is released in the wellbore, a polymerization reaction may occur in the wellbore, blocking the wellbore and causing a safety accident.

[0023] Preferably, the profile control and water plugging fluid comprises the following components in parts by mass: 30-40 parts of the first polymerizable monomer, 0.1-0.5 parts of the second polymerizable monomer, 0.02-0.04 parts of the initiator, 0.01-0.05 parts of the polymerization inhibitor, and 60-65 parts of water.

[0024] Preferably, the first polymerizing monomer and the chain extending polymerizing monomer are of the same composition type; the first polymerizing monomer is composed of p-styrene sulfonate and 2-acrylamido-2-methylpropane sulfonate, and the chain extending polymerizing monomer is composed of p-styrene sulfonate and 2-acrylamido-2-methylpropane sulfonate; or the first polymerizing monomer is an acrylamide monomer, and the chain extending polymerizing monomer is an acrylamide monomer; or the first polymerizing monomer is an acrylic acid monomer, and the chain extending polymerizing monomer is an acrylic acid monomer; or the first polymerizing monomer is composed of acrylamide monomer and acrylic acid monomer, and the chain extending polymerizing monomer is composed of acrylamide monomer and acrylic acid monomer. Making the chain extending polymerizing monomer the same as the first polymerizing monomer can make the three-dimensional network structure generated by the underground polymerization of the bulk-expanding particles and the profile control and water plugging fluid have the same temperature resistance and salt resistance, avoiding the incompatibility between the two, which makes the structure's temperature resistance and salt resistance worse. For example, when p-styrene sulfonate and 2-acrylamido-2-methylpropane sulfonate are used as the chain extending monomers, a heat resistance of 105°C and a mineralization resistance of 25×10 4 mg / L of volume expansion particles, and when the first polymerization monomer is not the same substance but an acrylic monomer is used, it is not salt-resistant, that is, it will not expand when encountering salt, and may even shrink when encountering high salt water.

[0025] Preferably, the second polymerizable monomer and the cross-linking polymerizable monomer have the same composition type; the second polymerizable monomer is N,N-methylenebisacrylamide, and the cross-linking polymerizable monomer is N,N-methylenebisacrylamide; or the second polymerizable monomer is polyethylene glycol diacrylate, and the cross-linking polymerizable monomer is polyethylene glycol diacrylate.

[0026] The water-soluble coating layer needs to completely cover the bulky particles. The mass of the water-soluble coating layer can be determined based on the surface area of ​​the bulky particles. Preferably, the particle size of the bulky particles is 1 to 2 mm, and the mass ratio of the bulky particles to the water-soluble coating layer is 2:(1 to 6).

[0027] Preferably, the mass ratio of the bulk-swelling particles, the profile-control and water-plugging liquid, and the water-soluble coating layer is 2:(6-12):(1-6).

[0028] The present invention does not limit the material of the water-soluble coating layer; any water-soluble polymer that can form a film is suitable for use in the present invention. Preferably, the water-soluble coating layer comprises a water-soluble polymer. Preferably, the water-soluble polymer is water-soluble starch, polyvinyl alcohol, cellulose, or chitosan. The water-soluble coating layer can be determined based on the temperature of the oil and gas field formation in which it is applied. When the temperature of the oil and gas field formation is not less than 65°C, the water-soluble polymer is polyvinyl alcohol. Preferably, the polyvinyl alcohol is polyvinyl alcohol 1799, polyvinyl alcohol 2099, polyvinyl alcohol 2499, or polyvinyl alcohol 2699.

[0029] Preferably, the water-soluble coating layer is made of a polymer glue, which includes a water-soluble polymer, a surfactant, an organic solvent and water.

[0030] Preferably, the mass ratio of the water-soluble polymer, surfactant, organic solvent and water is (12-15):(0.2-0.5):(3-6):(75-85).

[0031] Preferably, the surfactant is selected from one or any combination of anionic surfactants, cationic surfactants, zwitterionic surfactants, and nonionic surfactants. Preferably, the surfactant is an alkyl sulfate. For example, the surfactant is sodium lauryl sulfate. Surfactants can reduce interfacial tension, allowing the polymer to dissolve quickly; they can also reduce the viscosity of the polymer glue, increasing fluidity and facilitating film formation.

[0032] Preferably, the organic solvent is an alcohol solvent. For example, the organic solvent is glycerol. Organic solvents can accelerate the dissolution of the polymer, allowing it to quickly form a uniform adhesive solution; and can also increase the film-forming plasticity of the polymer adhesive solution.

[0033] Preferably, the polymer glue is prepared by mixing a water-soluble polymer, a surfactant, an organic solvent and water. Preferably, the mixing temperature is not lower than 95°C.

[0034] Preferably, the profile-controlling and water-plugging agent is prepared by a method comprising the following steps: using a polymer glue to wrap and modify the bulk-swelling particles adsorbed with the profile-controlling and water-plugging liquid to form a water-soluble coating layer to obtain the profile-controlling and water-plugging agent.

[0035] The preparation method of the profile control and water plugging agent of the present invention is simple to operate, the raw materials used are cheap and easily available, and can be produced on a large scale. The prepared profile control and water plugging agent can be formed into a whole by chemical bonding after being accumulated underground, and has good scour resistance and a long action time.

[0036] Preferably, the bulk-swelling particles adsorbed with the profile-control and water-plugging fluid are produced by adsorbing the profile-control and water-plugging fluid onto the bulk-swelling particles. For example, the bulk-swelling particles and the profile-control and water-plugging fluid are mixed to allow the bulk-swelling particles to absorb the fluid; or the mixture of the bulk-swelling particles and the profile-control and water-plugging fluid is allowed to stand to allow the bulk-swelling particles to absorb the fluid. To prevent solvent volatilization, the bulk-swelling particles and the profile-control and water-plugging fluid are mixed or the mixture is allowed to stand under sealed conditions.

[0037] The wrapping modification can be done manually or by using a coating machine. Preferably, the wrapping modification method comprises the following steps: the body-swelling particles adsorbed with the profile control and water plugging liquid are wrapped and modified by a coating machine using a polymer glue.

[0038] An application of the profile control and water plugging agent as described above in oil and gas field development.

[0039] When the profile controlling and water plugging agent of the present invention is used in the development of oil and gas fields, since the outer layer of the profile controlling and water plugging agent is wrapped with a water-soluble coating layer, the profile controlling and water plugging liquid can be prevented from being released during the injection process. After being injected into the formation and accumulated in the formation, the water-soluble coating layer wrapped on the outside dissolves in water at the formation temperature. The profile controlling and water plugging liquid can undergo a polymerization reaction under the action of the formation temperature to form a three-dimensional network structure, so that the accumulated bulk-expanding particles are filled in the three-dimensional network structure and cemented with the formation rock as a whole, thereby achieving the scour resistance of the profile controlling and water plugging agent and improving the effective period.

[0040] Preferably, the application comprises the following steps: injecting the profile control and water plugging agent into the oil and gas field formation.

[0041] Preferably, the application comprises the following steps: mixing a profile control and water plugging agent with water to obtain a suspension, and then injecting the suspension into an oil and gas field formation. The profile control and water plugging agent is injected as a suspension, and since the profile control and water plugging agent is coated with a water-soluble coating layer, the release of polymerizable reactive substances during the injection process can be prevented.

[0042] When the water-soluble coating layer is polyvinyl alcohol, preferably, the temperature of the oil and gas field formation is not lower than 65°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The profile control and water plugging agent of Example 2 of the present invention is heated at 80°C and 25×10 4 Schematic diagram of the simulated water with a salinity of mg / L after cementation in a 250 mL high temperature bottle;

[0044] Figure 2 The profile control and water plugging agent of Example 1 of the present invention is mixed with quartz sand at 105°C and 30×10 4 Schematic diagram of the appearance of simulated water with a mineralization of mg / L after cementation in a 100mL high-temperature tube;

[0045] Figure 3 The profile control and water plugging agent of Example 2 of the present invention is mixed with quartz sand at 80°C and 25×10 4 Schematic diagram of the appearance of simulated water with a mineralization of mg / L after cementation in a 250mL high-temperature bottle. DETAILED DESCRIPTION

[0046] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0047] Example 1

[0048] The profile control and water plugging agent of this embodiment comprises bulky particles and a water-soluble coating layer encapsulating the bulky particles, wherein the bulky particles adsorb a profile control and water plugging liquid; the mass ratio of the bulky particles, the profile control and water plugging liquid, and the water-soluble coating layer is 2:6:1;

[0049] The preparation method of the bulking particles in this embodiment is as follows: 65 parts by mass of water, 5 parts by mass of sodium p-styrene sulfonate, 30 parts by mass of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS-Na), 0.3 parts by mass of N,N-methylenebisacrylamide, 0.3 parts by mass of ammonium persulfate and 0.3 parts by mass of sodium sulfite are added to a reactor in sequence, and stirred until the mixture in the reactor is fully dissolved. Then, nitrogen is introduced into the reactor, and the mixture in the reactor is heated to 30° C. and stirred for 24 hours to obtain a solid rubber block, which is then cut, granulated, dried, and sieved to obtain bulking particles with a particle size of 1 to 2 mm.

[0050] The profile control and water plugging fluid in this embodiment is composed of the following components in parts by mass: 40 parts of the first polymerizable monomer, 0.5 parts of the second polymerizable monomer, 0.02 parts of the initiator, 0.05 parts of the polymerization inhibitor, and 60 parts of water; the first polymerizable monomer is composed of sodium p-styrene sulfonate and sodium 2-acrylamido-2-methylpropane sulfonate in a mass ratio of 5:35, the second polymerizable monomer is N,N-methylenebisacrylamide, the initiator is potassium persulfate, and the polymerization inhibitor is ferric ferrocyanide;

[0051] The water-soluble coating layer is made of a polymer glue, which is prepared by stirring and mixing polyvinyl alcohol, a surfactant, an organic solvent and water at 95°C. The mass ratio of polyvinyl alcohol, surfactant, organic solvent and water is 12:0.5:6:85. The polyvinyl alcohol is polyvinyl alcohol 2699, the surfactant is sodium lauryl sulfate, and the organic solvent is glycerol.

[0052] Example 2

[0053] The profile control and water plugging agent of this embodiment comprises bulky particles and a water-soluble coating layer encapsulating the bulky particles, wherein the bulky particles adsorb a profile control and water plugging liquid; the mass ratio of the bulky particles, the profile control and water plugging liquid, and the water-soluble coating layer is 2:8:2;

[0054] The preparation method of the bulking particles in this embodiment is as follows: 65 parts by mass of water, 40 parts by mass of acrylamide (AM), 0.5 parts by mass of N,N-methylenebisacrylamide, 0.5 parts by mass of ammonium persulfate, and 0.5 parts by mass of sodium sulfite are added to a reactor in sequence, and stirred until the mixture in the reactor is fully dissolved. Then, nitrogen is introduced into the reactor, and the mixture in the reactor is heated to 30° C. and stirred for reaction for 24 hours. Then, the solid obtained by the reaction is cut and granulated, and dried to obtain bulking particles with a particle size of 1 to 2 mm.

[0055] The profile control and water plugging fluid in this embodiment is composed of the following components in parts by weight: 36 parts of the first polymerizable monomer, 0.4 parts of the second polymerizable monomer, 0.03 parts of the initiator, 0.04 parts of the polymerization inhibitor, and 62 parts of water; the first polymerizable monomer is acrylamide, the second polymerizable monomer is N,N-methylenebisacrylamide, the initiator is potassium persulfate, and the polymerization inhibitor is ferric ferrocyanide;

[0056] The water-soluble coating layer is made of a polymer glue, which is prepared by stirring and mixing polyvinyl alcohol, a surfactant, an organic solvent and water at 95°C. The mass ratio of polyvinyl alcohol, surfactant, organic solvent and water is 13:0.4:5:82. The polyvinyl alcohol is polyvinyl alcohol 2499, the surfactant is sodium lauryl sulfate, and the organic solvent is glycerol.

[0057] Example 3

[0058] The profile control and water plugging agent of this embodiment comprises bulky particles and a water-soluble coating layer encapsulating the bulky particles, wherein the bulky particles adsorb a profile control and water plugging liquid; the mass ratio of the bulky particles, the profile control and water plugging liquid, and the water-soluble coating layer is 2:10:4;

[0059] The preparation method of the bulking particles in this embodiment is as follows: 65 parts by mass of water, 20 parts by mass of acrylamide (AM), 15 parts by mass of sodium acrylate (AA-Na), 0.3 parts by mass of N,N-methylenebisacrylamide, 0.3 parts by mass of ammonium persulfate, and 0.3 parts by mass of sodium sulfite are added to a reactor in sequence, and stirred until the mixture in the reactor is fully dissolved. Then, nitrogen is introduced into the reactor, and the mixture in the reactor is heated to 30° C. and stirred for reaction for 24 hours. Then, the solid obtained by the reaction is cut and granulated, and dried to obtain bulking particles with a particle size of 1 to 2 mm.

[0060] The profile control and water plugging fluid in this embodiment is composed of the following components in parts by weight: 33 parts of the first polymerizable monomer, 0.3 parts of the second polymerizable monomer, 0.04 parts of the initiator, 0.03 parts of the polymerization inhibitor, and 65 parts of water; the first polymerizable monomer is composed of acrylamide and sodium acrylate in a mass ratio of 20:13, the second polymerizable monomer is N,N-methylenebisacrylamide, the initiator is ammonium persulfate, and the polymerization inhibitor is ferric ferrocyanide;

[0061] The water-soluble coating layer is made of a polymer glue, which is prepared by stirring and mixing polyvinyl alcohol, a surfactant, an organic solvent and water at 95°C. The mass ratio of polyvinyl alcohol, surfactant, organic solvent and water is 14:0.3:4:78. The polyvinyl alcohol is polyvinyl alcohol 2099, the surfactant is sodium lauryl sulfate, and the organic solvent is glycerol.

[0062] Example 4

[0063] The profile control and water plugging agent of this embodiment comprises bulky particles and a water-soluble coating layer encapsulating the bulky particles, wherein the bulky particles adsorb a profile control and water plugging liquid; the mass ratio of the bulky particles, the profile control and water plugging liquid, and the water-soluble coating layer is 2:12:6;

[0064] The preparation method of the bulking particles in this embodiment is as follows: 65 parts by mass of water, 35 parts by mass of sodium acrylate (AA-Na), 0.3 parts by mass of N,N-methylenebisacrylamide, 0.3 parts by mass of ammonium persulfate, and 0.3 parts by mass of sodium sulfite are added to a reactor in sequence, and stirred until the mixture in the reactor is fully dissolved. Then, nitrogen is introduced into the reactor, and the mixture in the reactor is heated to 30° C. and stirred for reaction for 24 hours. Then, the solid obtained by the reaction is cut and granulated, and dried to obtain bulking particles with a particle size of 1 to 2 mm.

[0065] The profile control and water plugging fluid in this embodiment is composed of the following components in parts by weight: 30 parts of the first polymerizable monomer, 0.1 parts of the second polymerizable monomer, 0.04 parts of the initiator, 0.01 parts of the polymerization inhibitor, and 65 parts of water; the first polymerizable monomer is sodium acrylate, the second polymerizable monomer is N,N-methylenebisacrylamide, the initiator is ammonium persulfate, and the polymerization inhibitor is ferric chloride;

[0066] The water-soluble coating layer is made of a polymer glue, which is prepared by stirring and mixing polyvinyl alcohol, a surfactant, an organic solvent and water at 95°C. The mass ratio of polyvinyl alcohol, surfactant, organic solvent and water is 15:0.2:3:75. The polyvinyl alcohol is polyvinyl alcohol 1799, the surfactant is sodium lauryl sulfate, and the organic solvent is glycerol.

[0067] The profile-control and water-plugging agents of Examples 1-4 are prepared by the following steps: placing the bulk-swelling particles into a profile-control and water-plugging liquid to obtain a mixed liquid, then placing the mixed liquid in a sealed container and allowing it to stand at 20°C to 25°C. When there is no flowing liquid in the sealed container, the bulk-swelling particles are taken out, and then the bulk-swelling particles adsorbed with the profile-control and water-plugging liquid are wrapped and modified with a polymer glue by a coating machine to obtain the profile-control and water-plugging agent.

[0068] Comparative Example 1

[0069] The only difference between the profile controlling and water plugging agent of this comparative example and the profile controlling and water plugging agent of Example 1 is that the bulk-swelling particles used in the profile controlling and water plugging agent of this comparative example are the bulk-swelling particles used in the profile controlling and water plugging agent of Example 2.

[0070] Comparative Example 2

[0071] The only difference between the profile controlling and water plugging agent of this comparative example and the profile controlling and water plugging agent of Example 1 is that the bulk-swelling particles used in the profile controlling and water plugging agent of this comparative example are the bulk-swelling particles used in the profile controlling and water plugging agent of Example 3.

[0072] Comparative Example 3

[0073] The only difference between the profile controlling and water plugging agent of this comparative example and the profile controlling and water plugging agent of Example 1 is that the bulk-swelling particles used in the profile controlling and water plugging agent of this comparative example are the bulk-swelling particles used in the profile controlling and water plugging agent of Example 4.

[0074] Comparative Example 4

[0075] The only difference between the profile controlling and water plugging agent of this comparative example and the profile controlling and water plugging agent of Example 1 is that the mass of the profile controlling and water plugging liquid used in the profile controlling and water plugging agent of this comparative example is 0, that is, the bulk-swelling particles do not absorb the profile controlling and water plugging liquid.

[0076] Experimental Example 1

[0077] In order to test whether the profile control and water plugging agents of Examples 1-4 and Comparative Examples 1-4 can be cemented to form a three-dimensional network structure of non-flowing solids under formation conditions after accumulation, and the anti-aging performance of the solids formed by cementation, 15g of the profile control and water plugging agents of Examples 1-4 and Comparative Examples 1-4 were placed in a 100mL high-temperature tube or a 250mL high-temperature bottle, and then 50g of simulated water of different salinity was added to the high-temperature tube or the high-temperature bottle. The high-temperature tube or the high-temperature bottle containing the profile control and water plugging agent and the simulated water was placed in an oven at different temperatures and allowed to stand. Every 1 hour, the high-temperature tube or the high-temperature bottle was shaken to observe whether the liquid in the high-temperature tube still had fluidity. The starting time when the liquid in the high-temperature tube did not flow was recorded, which was the start of the cementation reaction time. Then, the observation was continued every 24 hours for 30 days to observe whether the non-flowing solid in the high-temperature tube or the high-temperature bottle would become a viscous liquid (i.e., age) as the placement time increased. The time when the non-flowing solid in the high-temperature tube began to become a viscous liquid was defined as the anti-aging time. The profile control and water plugging agent of Example 2 was heated to 80°C and 25×10 4 The schematic diagram of the simulated water with a mineralization of mg / L after cementation in a 250mL high temperature bottle is as follows Figure 1 The initial cementation reaction time and anti-aging time of different profile control and water plugging agents in simulated water at different temperatures and salinities are shown in Table 1.

[0078] Table 1 Initial cementation reaction time and anti-aging time of different profile control and water plugging agents in simulated water at different temperatures and salinities

[0079]

[0080] The experimental results show that the profile control and water plugging agent of Comparative Example 4 did not undergo polymerization reaction at the experimental temperature and salinity, and no solid was formed. The particles were only physically stacked and could be dispersed by shaking. In addition, the initial cementation reaction time of the profile control and water plugging agents of Examples 1-4 at the experimental temperature and salinity was greater than 15 hours, which is much longer than the injection time of the profile control and water plugging agent from the wellhead to the bottom of the well (generally 8 hours), and can meet the needs of on-site construction. However, the initial cementation reaction time of the profile control and water plugging agents of Comparative Examples 1-3 at the experimental temperature and salinity was less than 8 hours, which could not meet the requirements of on-site construction.

[0081] When the profile control and water plugging agents of Comparative Examples 1-3 undergo polymerization reactions at the experimental temperature and salinity to form cemented solids, after being placed at 105°C for a certain period of time (no more than 10 days), the cemented solids begin to turn into a viscous liquid, indicating that the aging performance of the cemented solids is poor. However, the profile control and water plugging agents of Examples 1-4 can undergo polymerization reactions to form cemented solids at the experimental temperature and salinity, and the cemented solids do not turn into a viscous liquid after being placed for 30 days.

[0082] Experimental Example 2

[0083] In order to test whether the profile control and water plugging agents of Examples 1-4 and Comparative Examples 1-4 can be bonded with the surrounding rocks under formation conditions and the anti-aging properties of the solids formed by the bonding, 40-80 mesh quartz sand was used to simulate formation rocks. First, the 40-80 mesh quartz sand was soaked in simulated water for 24 hours, then the quartz sand was removed and the quartz sand and the profile control and water plugging agent were mixed uniformly in a mass ratio of 1:1 to obtain a mixture. 50 g of the mixture was then added to a 100 mL high-temperature tube or a 250 mL high-temperature bottle, followed by 30 g of simulated water. The high-temperature tube or bottle containing the mixture and simulated water was then placed in an oven at different temperatures and allowed to stand. Every hour, the liquid in the high-temperature tube or bottle was shaken to observe whether it still had fluidity. The time when the liquid in the high-temperature tube stopped flowing was recorded, which was the start time of the bonding reaction. Then continue to observe every 24 hours for 30 days to see whether the stagnant solid in the high-temperature tube or high-temperature bottle will turn into a viscous liquid (i.e., aging occurs) as the placement time increases. The time when the stagnant solid in the high-temperature tube begins to turn into a viscous liquid is defined as the anti-aging time. 4 The schematic diagram of the appearance of the simulated water with a mineralization of mg / L after cementation in a 100mL high-temperature tube is as follows Figure 2 As shown, the profile control and water plugging agent of Example 2 was mixed with quartz sand at 80°C and 25×10 4 The schematic diagram of the appearance of the simulated water with a mineralization of mg / L after cementation in a 250mL high-temperature bottle is as follows Figure 3 shown.

[0084] The initial cementation reaction time and anti-aging time of different profile control and water plugging agents in simulated water at different temperatures and different salinities are shown in Table 2.

[0085] Table 2 Initial cementation reaction time and anti-aging time of different profile control and water plugging agents and quartz sand in simulated water at different temperatures and different salinities

[0086]

[0087] The experimental results show that the mixture formed by the profile control and water plugging agent and quartz sand of Comparative Example 4 did not undergo polymerization reaction at the experimental temperature and salinity, and no solid was formed. The particles were only physically stacked and could be dispersed by shaking. In addition, the mixture formed by the profile control and water plugging agent and quartz sand of Examples 1-4 could undergo polymerization and cementation at the experimental temperature and salinity, becoming one, and the starting cementation reaction time was much longer than the starting cementation reaction time of the profile control and water plugging agent at the experimental temperature and salinity, which could better meet the on-site construction time requirements. The starting cementation reaction time of the mixture formed by the profile control and water plugging agent and quartz sand of Comparative Examples 1-3 at the experimental temperature and salinity was still relatively short.

[0088] When the mixture formed by the profile control and water plugging agent and quartz sand of Comparative Examples 1-3 undergoes a polymerization reaction at the experimental temperature and salinity to form a cemented solid, after being placed at 105°C for a certain period of time (no more than 7 days), the cemented solid begins to turn into a viscous liquid, indicating that the aging performance of the cemented solid is poor. However, the cemented solid formed by the mixture formed by the profile control and water plugging agent and quartz sand of Examples 1-4 at the experimental temperature and salinity did not turn into a viscous liquid after being placed for 30 days.

[0089] Experimental Example 3

[0090] The anti-scour performance of the profile control and water plugging agent was evaluated by artificial sand filling pipe. The sand filling pipe size is: 30cm long, 2.54cm inner diameter. The quartz sand particle size is 40-80 mesh, and the mineralization degree is 25×10 4 Soak fully in simulated water with a concentration of 100 mg / L for 24 hours. The experimental steps are as follows:

[0091] (1) Sand filling of sand filling pipe: first fill the soaked quartz sand into the sand filling pipe to 1 / 3 of the height, then fill the mixture of profile control and water plugging agent and quartz sand with a mass ratio of 1:1 into the sand filling pipe to 2 / 3 of the height, and finally fill the soaked quartz sand into the sand filling pipe until the sand filling pipe is full;

[0092] (2) Connection process: the sand-filled tube is placed in an oven at a constant temperature of 80°C;

[0093] (3) Saturated water: Saturated water with a salinity of 25×10 4mg / L of simulated water until the pressure is constant, record the flow rate and injection pressure p0, and calculate the water phase permeability K and pore volume PV of brine in the sand-filled pipe;

[0094] (4) Aging of sand filling pipe: stop water injection and let it stand for 48 hours;

[0095] (5) Subsequent water flooding: At a constant flow rate of 50 mL / h, a water with a salinity of 25×10 4 mg / L of simulated water, record the pressure at which water begins to flow out of the sandfill pipe, which is the subsequent waterflood breakthrough pressure. Continue to inject simulated water at a constant flow rate of 50 mL / h, three times the pore volume, and record the injection pressure every time 1 PV is injected to obtain the waterflood pressure at different injection PVs.

[0096] The experimental results of evaluating the anti-scour performance of the profile control and water plugging agents of Example 2 and Comparative Example 4 are shown in Table 3.

[0097] Table 3 Anti-scour performance of profile control and water plugging agents of Example 2 and Comparative Example 4

[0098]

[0099] As can be seen from Table 3, after the profile control and water plugging agent of Example 2 is injected into the formation, a cementation reaction occurs in the formation, and the profile control and water plugging agents themselves and the profile control and water plugging agents and the formation become one. The subsequent water drive breakthrough pressure reaches 32.5 MPa. With the subsequent water injection and flushing, the pressure does not change significantly, and the anti-scouring ability is strong. However, after the profile control and water plugging agent of Comparative Example 4 is injected into the formation, it only blocks the dominant channel by physical accumulation after volume expansion. No cementation occurs between the gel particles or between the gel particles and the formation rock. The subsequent water drive breakthrough pressure is only 1.5 MPa, and the water drive pressure drops rapidly with the subsequent water injection and flushes. When the pore volume is 3 times, the pressure basically returns to the level before injection, and the anti-scouring ability is poor.

[0100] When the anti-scour performance of the profile control and water plugging agents of Examples 1 and 3-4 was tested according to the above method, the test results were close to the anti-scour performance of the profile control and water plugging agent of Example 2.

[0101] When the N,N-methylenebisacrylamide used in preparing the bulk-swelling particles in Example 2 is replaced by polyethylene glycol 400 diacrylate or polyethylene glycol 700 diacrylate, and the second polymerizable monomer in the profile control and water plugging fluid is replaced by N,N-methylenebisacrylamide with polyethylene glycol 400 diacrylate or polyethylene glycol 700 diacrylate, the performance of the resulting profile control and water plugging agent is consistent with that of the profile control and water plugging agent in Example 2 (the performance testing method is carried out according to the method of Experimental Examples 1-3).

Claims

1. A profile control and water plugging agent, characterized in that: The invention comprises bulk-swelling particles and a water-soluble coating layer encapsulating the bulk-swelling particles, wherein the bulk-swelling particles are adsorbed with a profile-control and water-plugging liquid; the mass ratio of the bulk-swelling particles to the profile-control and water-plugging liquid is 2:(6-12); the bulk-swelling particles are prepared by a method comprising the following steps: polymerizing a chain-extending polymerization monomer, a cross-linking polymerization monomer, and an initiator in water; the mass ratio of the chain-extending polymerization monomer, the cross-linking polymerization monomer, and the initiator is (35-40):(0.3-0.5):(0.6-1), the chain-extending polymerization monomer is selected from one or any combination of p-styrene sulfonate, 2-acrylamido-2-methylpropane sulfonate, an acrylamide monomer, and an acrylic acid monomer; the cross-linking polymerization monomer is N,N-methylenebisacrylamide and / or polyethylene glycol diacrylate; The profile control and water plugging fluid comprises the following components in parts by weight: 30-40 parts of a first polymerizable monomer, 0.1-0.5 parts of a second polymerizable monomer, 0.02-0.04 parts of an initiator, 0.01-0.05 parts of a polymerization inhibitor, and 60-65 parts of water; The first polymerizable monomer and the chain-extending polymerizable monomer are of the same composition type, and the second polymerizable monomer and the cross-linking polymerizable monomer are of the same composition type.

2. The profile control and water plugging agent according to claim 1, characterized in that: The particle size of the bulky particles is 1 to 2 mm.

3. The profile control and water plugging agent according to claim 1, characterized in that: The first polymerizable monomer is selected from one or any combination of p-styrene sulfonate, 2-acrylamido-2-methylpropane sulfonate, acrylamide monomers, and acrylic acid monomers; the second polymerizable monomer is N,N-methylenebisacrylamide and / or polyethylene glycol diacrylate.

4. The profile control and water plugging agent according to claim 3, characterized in that: The first polymerizable monomer is composed of p-styrene sulfonate and 2-acrylamido-2-methylpropane sulfonate, and the chain-extending polymerizable monomer is composed of p-styrene sulfonate and 2-acrylamido-2-methylpropane sulfonate; or the first polymerizable monomer is an acrylamide monomer, and the chain-extending polymerizable monomer is an acrylamide monomer; or the first polymerizable monomer is an acrylic acid monomer, and the chain-extending polymerizable monomer is an acrylic acid monomer; or the first polymerizable monomer is composed of an acrylamide monomer and an acrylic acid monomer, and the chain-extending polymerizable monomer is composed of an acrylamide monomer and an acrylic acid monomer.

5. The profile control and water plugging agent according to claim 3, characterized in that: The second polymerizable monomer is N,N-methylenebisacrylamide, and the cross-linking polymerizable monomer is N,N-methylenebisacrylamide; or the second polymerizable monomer is polyethylene glycol diacrylate, and the cross-linking polymerizable monomer is polyethylene glycol diacrylate.

6. The profile control and water plugging agent according to claim 1 or 2, characterized in that: The mass ratio of the bulky particles to the water-soluble coating layer is 2:(1-6); the water-soluble coating layer is made of a polymer glue, which includes a water-soluble polymer, a surfactant, an organic solvent and water; the water-soluble polymer is water-soluble starch, polyvinyl alcohol, cellulose and chitosan.

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