CN103739778B - A kind of nucleocapsid structure polyacrylamide microsphere profile control reservoir oil displacing agent and preparation method thereof - Google Patents

Abstract

The invention discloses a polyacrylamide microsphere profile control and oil displacement agent with a core-shell structure and a preparation method; fully stirring and dissolving acrylamide, a cationic monomer, a crosslinking agent and an initiator, and synthesizing the core part by a dispersion polymerization method; and then , add the mixed solution of acrylamide, anionic monomer, third monomer, crosslinking agent and initiator to the reaction device in batches, control the reaction conditions to remain unchanged, react on the surface of the inner core to form a shell part, and obtain a cationic polymer Acrylamide is the core, which is polymerized on the surface of the core to obtain a core-shell polyacrylamide microsphere profile control and oil displacement agent with an anionic polyacrylamide shell layer. The particle size range of the microsphere profile control and oil displacement agent is 1-100 μm. The microsphere has an interpenetrating network system, which forms a viscoelastic body after absorbing water, and forms a gel after a certain period of time. The sealing time is long, the leakage is small, and it can withstand the pressure above 5MPa.

Description

A core-shell structure polyacrylamide microsphere profile control oil displacement agent and preparation method thereof

technical field

The invention relates to a core-shell structure polyacrylamide microsphere profile control oil displacement agent and a preparation method.

Background technique

Due to the lithological changes of formations in most domestic oil production areas, the development of pores, fractures, and karst caves are different, the causes of lost circulation are complex, the types of loss are different, and there are many restrictive factors, and the plugging technology is highly targeted. So far, it is difficult to use a general The mode is used for leak prevention and plugging. In particular, the problem of lost circulation in fractured formations is more serious. According to incomplete statistics, the domestic reserves of fractured and complex formations account for about 50% of the total reserves. However, due to the development of formation fractures and holes, the leakage problem is difficult to solve, resulting in extremely serious losses. Therefore, the problem of vicious leakage in fractured complex formations has become the focus of attention in the drilling industry.

Fractured formation loss is an important factor affecting the safety, efficiency, cost and even the discovery and protection of oil and gas reservoirs in drilling engineering. In fractured formations, pores, cracks, and karst caves exist intersecting or exist alone. Especially when large karst caves or fractures are drilled and malignant leakage occurs, it is difficult to stop the leakage, and the plugging effect of conventional plugging materials is poor. In order to ensure safe drilling, improve drilling efficiency, reduce construction costs, and improve the protection effect of oil and gas layers, it is necessary to study high-efficiency plugging materials to deal with lost circulation in fractured formations.

Profile control and water shutoff technology has always been an effective means for oilfields to improve water flooding development effects and realize reservoir production increase. For profile control and water shutoff, deep profile control and flooding technology is a technology that maximizes secondary oil recovery while performing limited tertiary oil recovery. The traditional inorganic profile control agent is easy to precipitate and cannot enter the deep formation for plugging, the movable weak gel has poor cross-linking controllability, high cost, and the water-swellable polymer gel particles are large, so there is a contradiction between injection depth and plugging strength , the failure is faster; the polymer microsphere deep profile control technology is a new type of deep profile control technology developed to solve the above contradictions.

Cross-linked polymer microspheres are a class of widely used water-absorbing resins. Effective plugging is formed at crevices or pore throats to increase the oil recovery rate of the oil field. Polyacrylamide-based polymer microspheres have the advantage of being applied in the field of oil field profile control and oil displacement. The construction process is simple and convenient, and can be injected directly through the water injection pipeline, abandoning the traditional injection method of profile control pumps; The automation and standardization of the drug process avoids the complicated on-site manual liquid preparation in the traditional profile control process, and eliminates the influence of human factors on quality control; in terms of plugging performance, it has good shear resistance and underground self-crosslinking , Repeated cross-linking properties.

The polymer microsphere with core-shell structure provided by the present invention uses micron-sized cationic polyacrylamide as the core, and anionic polyacrylamide is wrapped on the surface of the core to form a shell through chemical bonds. The polyacrylamide inner core, the anionic polyacrylamide shell, and the inner core and the shell form a mutual transmission network structure. The provided core-shell polymer microspheres have good water absorption and elasticity, can absorb water, swell and cross-link within a certain time and temperature range to form a polymer gel, and can maintain good sealing strength for a long time. The prepared microspheres have a regular spherical shape, the particle size range is in the micron order and the particle size is controllable, and are suitable for reservoir conditions with different sizes of formation fractures and pore roars.

Contents of the invention

The purpose of the present invention is to use dispersion polymerization technology to prepare polyacrylamide microspheres with micron-sized core-shell structure, which has outstanding water absorption and swelling properties, while maintaining high strength, temperature resistance and salt resistance, and has a regular spherical shape and uniform particle size distribution.

Technical scheme of the present invention is as follows:

A core-shell structure polyacrylamide microsphere profile control and oil displacement agent of the present invention uses cationic polyacrylamide as the core, polymerizes on the surface of the core to obtain an anionic polyacrylamide shell, and the core-shell structure polyacrylamide microsphere adjusts The particle size range of the oil displacing agent is 1-100 μm.

The preparation method of the core-shell structure polyacrylamide microsphere profile control and oil displacement agent of the present invention, the specific steps are as follows:

(1) Add 1-40% of acrylamide, 1-10% of cationic monomer, and 0.1-15% of stabilizer for the total weight of the nuclear solution; then add 0.1-8% of the total weight of acrylamide and cationic monomer The crosslinking agent is an initiator of 0.01% to 5% of the total weight of the polymerized monomers, which is shaken until completely dissolved to obtain solution A;

(2) Add 1-40% acrylamide, 1-5% anionic monomer, 0.1-15% stabilizer, 0.1-3% third monomer for the total weight of the shell solution; then add acrylamide, The anionic monomer and the cross-linking agent with a total weight of 0.1-8% of the third monomer are shaken until completely dissolved to obtain solution B;

(3) adding an initiator of 0.01 to 5% of the total weight of monomers polymerized in the shell solution in step (2) into the solvent, shaking until completely dissolved, and obtaining solution C;

(4) Add 1/3 of solution A into the reaction vessel, pass _N2 into the solution to evacuate for 0.5h, control the temperature at 40-80°C, and stir at 200-500r/min; then react at constant temperature for 3h to obtain the Polymer solution; keep the above reaction conditions unchanged, add the remaining A solution to the reaction system, and continue the reaction for 3 hours; obtain the microsphere core mixture;

(5) Control the reaction conditions of step 4 to remain unchanged, add solution C to the obtained microsphere core mixture, and continue to adsorb for 1h in the _N2 environment; then slowly add solution B to the reaction system dropwise, and control the reaction conditions to continue React for 3 hours, and finally cool, filter, and dry to obtain a core-shell structure polyacrylamide microsphere profile control and oil displacement agent.

The cationic monomer is selected from acryloyloxyethyltrimethylammonium chloride, dimethyldiallylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, N,N'- One of dimethylaminoethacrylate hydrochloride, β-aminoethacrylate hydrochloride or N,N'-ethyl dimethylaminoethacrylate.

The anionic polyacrylamide shell is selected from the following:

(1) Anionic monomers are selected from acrylate, α-olefin sulfonate, 2-acrylamido-2-methylpropane sulfonate, β-allyl sulfonate, sodium styrene sulfonate, 2- One of acrylamido-2-methylpropanesulfonic acid;

(2) The third monomer is selected from one of styrene, acrylic acid, lauryl methacrylate, N-(4-ethyl)phenylacrylamide, methyl methacrylate, and 4-vinylpyridine;

The selected solvent can well dissolve the required monomers, including acrylamide, ionic monomer I, ionic monomer II, the third monomer, crosslinking agent, initiator and stabilizer, but at the same time do not dissolve their copolymerization product.

Described solvent is: methyl alcohol, ethanol, propanol, butanol, acetone, benzene, toluene, cyclohexane, kerosene, diesel oil, white oil, methylene chloride, chloroform or their mixed solvent, or above organic solvent and water mixture.

The initiator is selected from one of disazo initiators, organic peroxides or redox initiators.

The stabilizer is selected from polyethylene glycol, hydroxypropyl cellulose, castor oil polyoxyethylene ether, polyvinylpyrrolidone, polyvinyl alcohol or sodium dodecylbenzenesulfonate.

The crosslinking agent is selected from divinylbenzene, diisocyanate, N,N'-methylene bisacrylamide, pentaerythritol triacrylate, dimethyl diallyl ammonium chloride or polyethylene glycol diacrylic acid One of the esters.

The core part solution is composed of: 1-40% of the total weight of the core part solution of acrylamide, 1-10% of cationic monomer, 0.1-15% of stabilizer, 0.1-8% of the total weight of acrylamide and cationic monomer The cross-linking agent is an initiator of 0.01% to 5% of the total weight of each monomer, and the rest is a solvent.

The solution of the shell part is composed of: the total weight of the shell part solution is 1-40% acrylamide, 1-5% anionic monomer, 0.1-3% third monomer, 0.1-15% stabilizer, which is acrylamide 1, the crosslinking agent of 0.1-8% of the total weight of the anionic monomer and the third monomer, the initiator of 0.01-5% of the total weight of each monomer, and the rest is the solvent.

The synthesis method is used to prepare polyacrylamide microspheres with core-shell structure suitable for different formation pore throat diameters by changing the reaction process conditions.

During the preparation process of the core-shell polymer microsphere provided by the present invention, the organic solvent in the reaction system can be recovered and reused with high efficiency, realizing the green cycle of the production process.

In the present invention, acrylamide, cationic monomer, cross-linking agent and initiator are fully stirred and dissolved, and the core part is synthesized by dispersion polymerization; then, acrylamide, anionic monomer, third monomer, cross-linking agent and initiator are synthesized The mixed solution is added to the reaction device in stages, the reaction conditions are kept constant, and the shell part is formed by reaction on the surface of the inner core to obtain a core-shell structure in which cationic polyacrylamide is used as the core and polymerized on the surface of the inner core to obtain an anionic polyacrylamide shell Polyacrylamide microsphere profile control and oil displacement agent; the polyacrylamide microsphere profile control and oil displacement agent with core-shell structure of the present invention has the following advantages:

(l) The microsphere has an interpenetrating network system, which forms a viscoelastic body after absorbing water, and forms a gel after a certain period of time. The plugging time is long and the leakage is small. As long as the appropriate particle size, dosage and injection pressure are selected, all can See results in a short period of time;

(2) The microsphere has a core-shell structure, good injection performance and simple injection process;

(2) The pressure bearing effect is good, at least withstand the pressure of 5MPa or more;

(3) The particle size of the microspheres is controllable, and the particle size of the microspheres can be selected according to the needs when sealing the leakage layer.

detailed description

Example 1

Microsphere preparation experiment

Weigh successively 1g (1%) of acrylamide, 3g (3%) of N,N'-dimethylaminoethylacrylic acid hydrochloride, 0.32g (8%) of divinylbenzene, 0.043g (1 %) of azobisisobutyronitrile, 0.1g (0.1%) of polyethylene glycol, add ethanol and butanol mixed solvent to 100g, wherein the ratio of ethanol to butanol is 4:6, fully stirred until completely dissolved; Add 1/3 of the solution into the reaction container, pass _N2 into the solution to evacuate for 0.5h, control the temperature at 40°C, and stir at a speed of 300r/min; then react at a constant temperature for 3h; obtain a prepolymer solution; control the above reaction conditions Unchanged, the remaining solution was evenly added dropwise to the reaction system, and the reaction was continued for 3 hours; the white solid continued to increase, and the microsphere core mixture was obtained;

Weigh 0.6g (1%) of azobisisobutyronitrile, add a mixed solvent of ethanol and butanol to 10g, wherein the ratio of ethanol to butanol is 4:6, stir well until it is completely dissolved, and add it to the microsphere core mixture In the process, the reaction conditions were controlled to be constant, and the constant temperature was reacted for 1 hour; 24g (40%) of acrylamide, 0.6g (1%) of 2-acrylamido-2-methylpropanesulfonic acid, 1.8g (3% ) of styrene, 4.8g (8%) of divinylbenzene, 0.6g (0.1%) of polyethylene glycol, add ethanol and butanol mixed solvent to 50g, fully stir until completely dissolved, and prepare the above The solution was evenly added dropwise to the above solution, controlled at 40°C, 300r/min, and continued to react for 3h under the protection of _N2 to obtain a white turbid system;

Finally, it was cooled, filtered and washed, and the resulting solid was dried to obtain a white powder. According to the characterization, the particle size of the powder is about 63 μm, of which the inner core size of the microsphere is about 41 μm, and the water absorption ratio is 64 times.

Evaluation experiment of water shutoff agent for microsphere plugging No. 1 rock sample

Accurately weigh 0.5 g of the core-shell polyacrylamide microspheres prepared in Example 1, add 99.5 g of oilfield formation water, and obtain a 5‰ microsphere dispersion after fully dispersing, keep the temperature at 60°C for 5 to 24 hours, A uniform microsphere dispersion system was obtained. Under the condition of constant temperature of 60°C, the oilfield formation water is first injected into the microsphere plugging No. 1 rock sample water plugging agent evaluation experimental device, and after the original data collection is completed, the configured microsphere dispersion is injected into the plugging core for water plugging In the agent evaluation experimental device, the collected data shows that the injection pressure increases by 5.64MPa compared with the water injection, and the permeability decreases by 14.72md.

Example 2

Microsphere preparation experiment

Weigh successively 7g (10%) of acrylamide, 0.7g (1%) of dimethyl diallyl ammonium chloride, 0.154g (2%) of N,N'-methylenebisacrylamide, 0.235 g (3%) of benzoyl peroxide, 0.7g (1%) of castor oil polyoxyethylene ether, add cyclohexane to 70g, fully stir until completely dissolved; add 1/3 of the solution into the reaction vessel, Introduce _N2 into the solution to evacuate for 0.5h, control the temperature at 60°C, and stir at a speed of 200r/min; In the reaction system, the reaction was continued for 3 hours; the white solid continued to increase, and the microsphere core mixture was obtained;

Weigh 0.436g (3%) of benzoyl peroxide, add cyclohexane to 5g, fully stir until completely dissolved and add to the microsphere core mixture, control the reaction conditions unchanged, and react at constant temperature for 1h; weigh 12g in sequence (30%) of acrylamide, 0.6g (1.5%) of acrylate, 1g (2.5%) of lauryl methacrylate, 0.952g (7%) of N,N'-methylenebisacrylamide, 0.6 g (1%) castor oil polyoxyethylene ether, add cyclohexane to 35g, fully stir until completely dissolved, evenly add the above prepared solution into the above solution, control 40°C, 300r/min, N ₂ The reaction was continued for 3 hours under protection to obtain a white turbid system;

Finally, it was cooled, filtered and washed, and the resulting solid was dried to obtain a white powder. After characterization and determination, the particle size of the powder is about 86 μm, of which the inner core size of the microsphere is about 54 μm, and the water absorption rate is 68 times.

Evaluation experiment of water shutoff agent for microsphere plugging No. 2 rock sample

Accurately weigh 0.5 g of the core-shell polyacrylamide microspheres prepared in Example 2, add 99.5 g of oilfield formation water, and obtain a 5‰ microsphere dispersion after fully dispersing, keep the temperature at 60°C for 5 to 24 hours, A uniform microsphere dispersion system was obtained. Under the condition of constant temperature of 60°C, the oilfield formation water is first injected into the microsphere plugging No. 2 rock sample water plugging agent evaluation experimental device, and after the original data collection is completed, the configured microsphere dispersion is injected into the plugging core for water plugging In the agent evaluation experimental device, the collected data shows that the injection pressure increases by 6.17MPa compared with the water injection, and the permeability decreases by 17.53md.

Example 3

Microsphere preparation experiment

Weigh successively 20g (40%) of acrylamide, 5g (10%) of N,N'-dimethylamino ethyl ethacrylate, 0.75g (3%) of polyethylene glycol diacrylate, 0.003g (0.01%) of benzoyl peroxide, 2g (4%) of polyvinyl alcohol, add toluene to 50g, fully stir until completely dissolved; add 1/3 of the solution into the reaction vessel, and pass _N2 into the solution Evacuate for 0.5h, control the temperature at 80°C, and stir at a speed of 200r/min; then react at a constant temperature for 3h; obtain a prepolymer solution; control the above reaction conditions unchanged, add the remaining solution evenly to the reaction system, and continue to react for 3h ; The white solid is constantly increasing, and the microsphere core mixture is obtained;

Take by weighing 0.003g (0.01%) of benzoyl peroxide, add toluene to 10g, fully stir until fully dissolved and join in the microsphere core mixture, control the reaction conditions constant, constant temperature reaction 1h; %) of acrylamide, 4g (5%) of α-olefin sulfonate, 1.2g (1.5%) of 4-vinylpyridine, 0.996g (3%) of polyethylene glycol diacrylate, 0.6g ( 4%) of polyvinyl alcohol, add toluene to 70g, fully stir until completely dissolved, evenly drop the prepared solution into the above solution, control 80°C, 300r/min, and continue to react for 3h under the protection of _N2 to obtain white turbid system;

Finally, it was cooled, filtered and washed, and the resulting solid was dried to obtain a white powder. According to the characterization and determination, the particle size of the powder is about 24 μm, of which the inner core size of the microsphere is about 18 μm, and the water absorption rate is 56 times.

Evaluation experiment of water shutoff agent for microsphere plugging No. 3 rock sample

Accurately weigh 0.5 g of the core-shell polyacrylamide microspheres prepared in Example 3, add 99.5 g of oilfield formation water, and obtain a 5‰ microsphere dispersion after fully dispersing, keep the temperature at 60°C for 5 to 24 hours, A uniform microsphere dispersion system was obtained. Under the condition of constant temperature of 60°C, the oilfield formation water is first injected into the microsphere plugging No. 3 rock sample water plugging agent evaluation experimental device, and after the original data collection is completed, the configured microsphere dispersion is injected into the plugging core for water plugging In the agent evaluation experimental device, the collected data shows that the injection pressure increases by 5.83MPa compared with the water injection, and the permeability decreases by 21.04md.

Example 4

Microsphere preparation experiment

Weigh successively 37.5g (25%) of acrylamide, 10.5g (7%) of methacryloxyethyl trimethylammonium chloride, 0.048g (0.1%) of diisocyanate, 2.402g (5%) azobisisobutyronitrile, 0.9g (0.6%) of sodium dodecylbenzenesulfonate, add benzene to 50g, fully stir until completely dissolved; add 1/3 of the solution into the reaction vessel, and pass through the solution Enter _N2 to evacuate for 0.5h, control the temperature at 50°C, and stir at a speed of 500r/min; then react at a constant temperature for 3h; obtain a prepolymer solution; control the above reaction conditions unchanged, and evenly add the remaining solution dropwise into the reaction system, The reaction continued for 3 hours; the white solid continued to increase, and the microsphere core mixture was obtained;

Weigh 0.125g (5%) of azobisisobutyronitrile, add benzene to 7g, stir fully until completely dissolved and add to the microsphere core mixture, control the reaction conditions to remain unchanged, and react at constant temperature for 1h; weigh 0.5g in sequence (1%) acrylamide, 1.5g (3%) beta-allylsulfonate, 0.5g (1%) N-(4-ethyl)phenylacrylamide, 0.003g (0.1%) diisocyanate, 0.3g (0.6%) sodium dodecylbenzene sulfonate, add benzene to 43g, fully stir until completely dissolved, evenly add the prepared solution to the above solution, control 80 ℃, 300r /min, under the protection of _N2 , the reaction was continued for 3h to obtain a white turbid system;

Finally, it was cooled, filtered and washed, and the resulting solid was dried to obtain a white powder. According to the characterization and measurement, the particle size of the powder is about 40 μm, among which, the size of the inner core of the microsphere is about 38 μm, and the water absorption rate is 72 times.

Evaluation experiment of water shutoff agent for microsphere plugging No. 4 rock sample

Accurately weigh 0.5 g of the core-shell polyacrylamide microspheres prepared in Example 4, add 99.5 g of oilfield formation water, and obtain a 5‰ microsphere dispersion after fully dispersing, keep the temperature at 60°C for 5 to 24 hours, A uniform microsphere dispersion system was obtained. Under the condition of constant temperature of 60°C, the oilfield formation water is first injected into the microsphere plugging No. 4 rock sample water plugging agent evaluation experimental device, and after the original data collection is completed, the prepared microsphere dispersion is injected into the plugging core for water plugging In the agent evaluation experimental device, the collected data showed that the injection pressure increased by 6.38MPa compared with water injection, and the permeability decreased by 15.71md.

Example 5

Microsphere preparation experiment

Weigh successively 6g (20%) of acrylamide, 1.5g (5%) of acryloyloxyethyl trimethylammonium chloride, 0.45g (6%) of dimethyl diallyl ammonium chloride, 0.038 g (0.5%) of potassium persulfate, 4.5 g (15%) of polyvinylpyrrolidone, add ethanol and water mixture to 30 g, wherein the ratio of alcohol to water is 7:3, fully stir until completely dissolved; 3 Add to the reaction container, pass _N2 into the solution to evacuate for 0.5h, control the temperature at 65°C, and stir at 400r/min; then react at a constant temperature for 3h; obtain a prepolymer solution; control the above reaction conditions unchanged, The remaining solution was evenly added dropwise to the reaction system, and the reaction was continued for 3 hours; the white solid continued to increase, and the microsphere core mixture was obtained;

Take by weighing 0.7g (0.5%) of potassium persulfate, add ethanol, water mixture to 25g, wherein the ratio of alcohol to water is 7:3, fully stir until fully dissolved, join in the microsphere core mixed solution, control the reaction conditions Change, constant temperature reaction for 1h; successively weigh 14g (10%) of acrylamide, 5.6g (4%) of 2-acrylamido-2-methylpropanesulfonate, 0.14g (0.1%) of acrylic acid, 1.184 g (6%) of dimethyl diallyl ammonium chloride, 4.2g (3%) of polyvinylpyrrolidone, add ethanol and water mixture to 115g, wherein the ratio of alcohol to water is 7:3, fully stir until complete Dissolve, add the above prepared solution evenly dropwise to the above solution, control, 65°C, 400r/min, and continue to react for 3h under the protection of _N2 to obtain a white turbid system;

Finally, it was cooled, filtered and washed, and the resulting solid was dried to obtain a white powder. According to the characterization, the particle size of the powder particles is about 15 μm, among which, the size of the inner core of the microsphere is about 10 μm, and the water absorption ratio is 61 times.

Evaluation experiment of water shutoff agent for microsphere plugging No. 5 rock sample

Accurately weigh 0.5 g of the core-shell polyacrylamide microspheres prepared in Example 5, add 99.5 g of oilfield formation water, and obtain a 5‰ microsphere dispersion after fully dispersing, keep the temperature at 60°C for 5 to 24 hours, A uniform microsphere dispersion system was obtained. Under the condition of constant temperature of 60°C, the oilfield formation water is first injected into the microsphere plugging No. 5 rock sample water plugging agent evaluation experimental device, and after the original data collection is completed, the prepared microsphere dispersion is injected into the plugging core for water plugging In the agent evaluation experimental device, the collected data shows that the injection pressure increases by 5.38MPa compared with the water injection, and the permeability decreases by 18.79md.

Example 6

Microsphere preparation experiment

Weigh successively the acrylamide of 42g (30%), the beta-aminoethylacrylic acid hydrochloride of 10.5g (7.5%), the pentaerythritol triacrylate of 1.575g (3%), the dihydrochloride of 1.352g (2.5%) Azodiisobutyronitrile, 2.8g (2%) of hydroxypropyl cellulose, add carbon tetrachloride to 140g, fully stir until completely dissolved; 1/3 of the solution is added to the reaction vessel, and N ₂ Evacuate for 0.5h, control the temperature at 50°C, and stir at a speed of 300r/min; then react at a constant temperature for 3h; obtain a prepolymer solution; control the above reaction conditions unchanged, add the remaining solution evenly to the reaction system, and continue the reaction 3h; the white solid is continuously increasing, and the microsphere core mixture is obtained;

Weigh 0.209g (2.5%) of azobisisobutyronitrile, add carbon tetrachloride to 7g, fully stir until completely dissolved, add to the microsphere core mixture, control the reaction conditions to remain constant, and react at constant temperature for 1h; Weigh 6g (10%) of acrylamide, 1.2g (2%) of sodium styrene sulfonate, 0.9g (1.5%) of methyl methacrylate, 0.243g (3%) of pentaerythritol triacrylate, 9g (15%) hydroxypropyl cellulose, add carbon tetrachloride to 53g, fully stir until completely dissolved, evenly add the above prepared solution into the above solution, control, 50 ° C, 300r/min, N ₂ The reaction was continued for 3 hours under protection to obtain a white turbid system;

Finally, it was cooled, filtered and washed, and the resulting solid was dried to obtain a white powder. According to the characterization and measurement, the particle size of the powder is about 40 μm, among which, the size of the inner core of the microsphere is about 30 μm, and the water absorption rate is 71 times.

Evaluation experiment of water shutoff agent for plugging No. 6 rock sample with microspheres

Accurately weigh 0.5 g of the core-shell polyacrylamide microspheres prepared in Example 6, add 99.5 g of oilfield formation water, and obtain a 5‰ microsphere dispersion after fully dispersing, keep the temperature at 60°C for 5 to 24 hours, A uniform microsphere dispersion system was obtained. Under the constant temperature condition of 60°C, the oilfield formation water is first injected into the microsphere plugging No. 6 rock sample water plugging agent evaluation experimental device, and after the original data collection is completed, the configured microsphere dispersion is injected into the plugging core for water plugging In the agent evaluation experimental device, the collected data showed that the injection pressure increased by 6.53MPa compared with water injection, and the permeability decreased by 20.38md.

The present invention is not limited to the technology described in the embodiment, its description is illustrative, not restrictive, the authority of the present invention is defined by the claims, based on those skilled in the art can change and reorganize according to the present invention The technologies related to the present invention obtained by such methods are all within the protection scope of the present invention.

Claims (5)

1. A preparation method of core-shell structure polyacrylamide microsphere profile control and oil displacement agent is characterized in that it is prepared by dispersion polymerization technology, and its concrete steps are as follows: (1) Add 1-40% acrylamide, 1-10% cationic monomer and 0.1-15% stabilizer for the total weight of the nuclear solution; then add 0.1-8% of the total weight of acrylamide and cationic monomer The crosslinking agent is an initiator of 0.01% to 5% of the total weight of the polymerized monomers, which is shaken until completely dissolved to obtain solution A; (2) Add 1-40% acrylamide, 1-5% anionic monomer, 0.1-3% third monomer, and 0.1-15% stabilizer for the total weight of the shell solution; then add acrylamide, The anionic monomer and the cross-linking agent with a total weight of 0.1-8% of the third monomer are shaken until completely dissolved to obtain a solution B; (3) adding an initiator of 0.01 to 5% of the total weight of monomers polymerized in the shell solution in step (2) into the solvent, shaking until completely dissolved, and obtaining solution C; (4) Add 1/3 of solution A into the reaction vessel, pass _N2 into the solution to evacuate for 0.5h, control the temperature at 40-80°C, and stir at 200-500r/min; then react at constant temperature for 3h to obtain Prepolymer solution; keep the above reaction conditions unchanged, add the remaining solution A to the reaction system, and continue the reaction for 3 hours; obtain the microsphere core mixture; (5) Control the reaction conditions of step (4) to be constant, add solution C to the microsphere core mixed solution obtained, N _The environment continues to adsorb for 1h; then solution B is slowly added dropwise to the reaction system, and the control reaction conditions are not changed. The reaction was continued for 3 hours, and finally cooled, filtered, and dried to obtain a core-shell structure polyacrylamide microsphere profile control and oil displacement agent; The cationic monomer is selected from one of acryloyloxyethyltrimethylammonium chloride, dimethyldiallylammonium chloride or methacryloyloxyethyltrimethylammonium chloride; The anionic monomer is selected from acrylate, α-olefin sulfonate, 2-acrylamido-2-methylpropane sulfonate, β-allyl sulfonate, sodium styrene sulfonate, 2-acrylamide One of base-2-methylpropanesulfonic acid; the third monomer is selected from styrene, acrylic acid, lauryl methacrylate, N-(4-ethyl)phenylacrylamide, methyl methacrylate Esters, one of 4-vinylpyridine. 2. preparation method as claimed in claim 1 is characterized in that used solvent is: methyl alcohol, ethanol, propanol, butanol, acetone, benzene, toluene, cyclohexane, kerosene, diesel oil, white oil, methylene dichloride , chloroform or their mixed solvents, or the mixed solution of the above organic solvents and water. 3. The preparation method according to claim 1, characterized in that the initiator is selected from the group consisting of azobisisobutyronitrile, organic peroxides or redox initiators. 4. the preparation method as claimed in claim 1 is characterized in that described stabilizing agent is selected from polyethylene glycol, hydroxypropyl cellulose, castor oil polyoxyethylene ether, polyvinylpyrrolidone, polyvinyl alcohol or dodecyl One of the sodium alkylbenzene sulfonates. 5. the preparation method as claimed in claim 1 is characterized in that described linking agent is selected from divinylbenzene, diisocyanate, N,N'-methylenebisacrylamide, pentaerythritol triacrylate, dimethyl Diallyl ammonium chloride or polyethylene glycol diacrylate.