CN114380942A - Heat-resistant and salt-resistant polyacrylamide nano-microspheres and preparation method thereof - Google Patents

Abstract

The invention relates to a temperature-resistant and salt-resistant polyacrylamide nano microsphere and a preparation method thereof, wherein the temperature-resistant and salt-resistant polyacrylamide nano microsphere comprises the following components: acrylamide monomer, anionic hydrophilic monomer, cationic hydrophilic monomer, nonionic water-soluble monomer, temperature-resistant salt-resistant monomer, hydrophobic monomer, deionized water, cross-linking agent, solvent, surfactant, initiator and phase transfer agent. The prepared temperature-resistant and salt-resistant nano-microsphere has controllable particle size, can be used for a stratum with a large pore throat and a stratum with a small pore throat, has good stability under the conditions of high salinity and high temperature, and can effectively block the pore throat for a long time, thereby achieving the purposes of increasing oil and improving recovery. The technical scheme of the invention can be applied to deep profile control, water shutoff and oil displacement of tertiary oil recovery, and the process is simple and is convenient for industrial large-scale production.

Description

Heat-resistant and salt-resistant polyacrylamide nano-microspheres and preparation method thereof

Technical Field

The invention relates to a temperature-resistant and salt-resistant polyacrylamide nano microsphere and a preparation method thereof, belonging to the technical field of chemical synthesis.

Background

The petroleum resource belongs to a valuable key strategic resource and has important influence and effect on national economic development and production and life of people. However, petroleum belongs to non-renewable resources and can not be continuously exploited, and the exploitation difficulty is increased along with the increase of exploration exploitation depth. Therefore, high oil recovery is also a problem of great concern and attention in the oil industry, and even in the industrial industry. The tertiary oil recovery technology belongs to a brand new oil recovery technology which is rapidly developed and aroused in recent years, and the wide popularization and the key application of the tertiary oil recovery technology can obviously improve the crude oil recovery rate and the total crude oil yield, and play an important role in promoting the stable development of the petroleum industry.

Before the middle of the 20 th century, oil field development was carried out by spontaneous injection based on the original energy of oil reservoir, and the oil recovery efficiency was low, only between 5% and 10%, so it is also called Primary Oil Recovery (POR). This is also a low technical level in the early stages of oil field development, the application of primary oil recovery, making over 90% of the ascertained oil reserves inefficiently exploited and mostly left underground. With the further development of the seepage theory, Darcy's law is also applied to the penetration of fluid in a porous medium, and the positive correlation between the oil well production and the pressure gradient is proved. Therefore, it is also known that the key factor of the low recovery rate of primary oil recovery is the energy sintering of the oil reservoir, so that an artificial water (gas) injection method, also called Secondary Oil Recovery (SOR), is also developed to supplement the energy of the oil reservoir and increase the pressure of the oil reservoir. The method also belongs to a development method widely applied to oil fields, the crude oil recovery rate is remarkably increased and is between 30 and 40, and the recovery technical level is greatly improved. However, secondary oil recovery still has 60% -70% of the ascertained oil output that is not efficiently recovered. Therefore, practitioners in the petroleum industry at home and abroad are also continuously conducting deep research to understand and master the factors influencing the secondary oil recovery rate and propose a brand new tertiary oil recovery technology (EOR). The tertiary oil recovery, namely after the oil reservoir adopts primary and secondary oil recovery, the properties and the phase state of the fluid are changed by physical and chemical methods, the interface action among gas-liquid, liquid-liquid and liquid-solid phases is changed, the influence range of injected water is enlarged, and the oil displacement efficiency is improved, so that the crude oil recovery rate is obviously improved.

Currently, four major technical families for tertiary oil recovery have been developed in the world, namely chemical flooding, gas flooding, thermal flooding and microbial flooding. Wherein the chemical flooding comprises polymer flooding, surfactant flooding, alkali flooding and binary and ternary composite flooding compounded by the polymer flooding, the surfactant flooding, the alkali flooding and the foam flooding; gas flooding comprises CO₂Miscible/immiscible flooding, nitrogen flooding, hydrocarbon gas flooding, flue gas flooding and the like; the thermal drive comprises steam huff and puff, hot water drive, steam drive, in-situ combustion and the like; the microbial flooding comprises microbial profile control or microbial flooding and the like. Among the four tertiary oil recovery technologies, some have already been applied industrially, some are developing pilot mine tests, and others are still in theoretical research.

The polymer flooding technology has clear mechanism and relatively simple technology, and the research of countries in the world is earlier, indoor research is carried out in the United states at the end of the fifties and at the beginning of the sixties, and mine field tests are carried out in 1964. Polymer mine site tests have been rapidly conducted in countries such as the soviet union, canada, uk, france, romania and germany since 1970. Since the 60's of the 20 th century, more than 200 fields or blocks have been tested for polymer flooding throughout the world. The polymer flooding is to add a small amount of water-soluble high molecular polymer into the injected water, improve the fluidity ratio and increase the sweep coefficient by increasing the viscosity of the water phase and reducing the permeability of the water phase, thereby increasing the oil recovery rate of crude oil.

In recent years, novel hydrophobically associating water-soluble polymers with temperature resistance, salt resistance and shear resistance are developed. It is a water-soluble polymer with a small amount of hydrophobic groups on the hydrophilic macromolecular chain of the polymer. Due to the hydrophobic effect of the hydrophobic groups and the effect of static electricity, hydrogen bonds or van der waals force, reversible physical association with certain strength is automatically generated among molecules, so that a huge three-dimensional net-shaped space structure is formed. The unique properties of which are receiving increasing attention.

China has become the world with the largest scale polymer flooding technology and the best large-area production increasing effect, and the polymer flooding technology becomes an important technical measure for continuous high and stable production of petroleum in China. The polymer microsphere is a particle dispersion system synthesized by an inverse emulsion or a dispersion polymerization method, and has good dispersibility in water and small particle size. In the reservoir water flooding process, when the water flooding pressure is increased, the water flooding agent can easily enter deeper parts of the stratum along with injected water, so that deep plugging is realized. When the water reaches a certain stratum depth, the water flow speed is reduced, a large number of small balls are continuously gathered and retained, and a pore throat is blocked in the migration process, so that a large blocking slug is finally formed, and the purposes of controlling water and stabilizing oil are achieved. The polymer microsphere has the characteristics that: (1) the particle size is small, the suspension property is good, and the oil can enter the deep part of a reservoir; (2) the retention capacity is strong, and the internal specific surface area can be greatly increased; (3) temperature-resistant and salt-resistant AMPS groups are introduced, so that the salt resistance is good; (4) the single phase system can realize the block on-line integral injection.

The research on the application of hydrogel microspheres for oil extraction to improve the recovery efficiency at home and abroad is less than forty years, but considerable achievements are obtained. The Field pilot test reported in the literature (James P, Frampton H, Brinkman J, et. Field application of a novel-depth water flooding compatibility tool. SPE84897, 2003) shows that the gel microsphere has good near-well injection and depth flooding increasing performance and obvious oil increasing effect. The polyacrylamide nano-microsphere is a space net-shaped polyacrylamide particle prepared by taking the microemulsion as a disperse system and acrylamide as a main monomer under the condition of adding a proper amount of a cross-linking agent. After the particles are injected into the stratum, the particles absorb water and expand, so that the volume of the particles is increased, the dominant water flow channels in the stratum can be blocked, and the sweep coefficient of the injected water is improved. The prepared polyacrylamide nano microspheres have small particle size and low aqueous solution viscosity, so that the polyacrylamide nano microspheres can easily enter the deep part of a stratum to realize deep profile control, and therefore, the polyacrylamide nano microspheres have great significance for controlling water and stabilizing oil of old oil reservoirs and improving the water injection development effect of offshore oil fields, low-permeability oil reservoirs and hypersalinity oil reservoirs.

Disclosure of Invention

One of the technical problems to be solved by the invention is that the existing polyacrylamide nano microsphere technology has the problems of higher production cost, poor oil displacement effect, poor compounding property with a surfactant for oil displacement and the like. The product is not stable enough, the strength is poor, the plugging effect needs to be improved, and the water absorption expansion effect is poor. The crude oil recovery rate is influenced by poor temperature resistance and salt resistance, easy deformation, precipitation and poor plugging effect in actual operation. The heat-resistant salt-resistant nano-microsphere adopts a reverse microemulsion polymerization method to reduce the consumption of common emulsifiers ineffective for oil displacement and reduce the cost, and because the oil displacement surfactant is used as an emulsifier and is distributed on an oil-water interface of the nano-microsphere and acts on the oil-water interface in a microemulsion mode, the oil washing efficiency of the oil displacement surfactant is improved, and a certain oil displacement regulating effect is achieved. In addition, the temperature resistance and salt resistance of the polymer microsphere are enhanced by introducing the temperature resistance and salt resistance comonomer.

The second technical problem to be solved by the invention is to provide a method for preparing the temperature-resistant and salt-resistant nano-microsphere, which solves the first technical problem, and an emulsifier system with better emulsification, capacity increase and stabilization effects and capability of reducing the tension of an oil-water interface is screened to prepare the polymer microemulsion with good stability. The prepared temperature-resistant salt-resistant low-nano microsphere can be directly used or used for on-site application of high-temperature high-salt tertiary oil recovery such as deep profile control, water shutoff, oil displacement and the like after being compounded with other oilfield chemicals to improve the recovery ratio.

In order to solve one of the technical problems, the invention adopts the following technical scheme:

a temperature-resistant and salt-resistant nano microsphere profile control and flooding agent is prepared from a reaction system comprising the following components in percentage by mass: 20-30% of acrylamide monomer, 1-3% of anionic hydrophilic monomer, 1-3% of cationic hydrophilic monomer, 0.1-0.5% of nonionic water-soluble monomer, 3-8% of temperature-resistant salt-resistant monomer, 0.1-0.5% of hydrophobic monomer, 0.01-0.05% of cross-linking agent, 40-48% of solvent, 10-16% of surfactant, 0.01-0.05% of initiator, 2-6% of phase transfer agent and the balance of deionized water.

The anionic hydrophilic monomer is preferably at least one of acrylic acid, methacrylic acid, maleic acid, itaconic acid and vinyl benzene sulfonic acid.

The cationic hydrophilic monomer is preferably at least one of dimethyl ethyl allyl ammonium chloride, dimethyl diallyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl dimethyl ethyl ammonium bromide, methacryloyloxyethyl trimethyl ammonium chloride and 2-acrylamido-2-methylpropyl trimethyl ammonium chloride.

In the technical scheme, the cationic hydrophilic monomer can generate an electrostatic interaction with negative charges in the stratum, so that the adhesion between the nano microspheres and gaps is improved, and the hydrophobic groups can enable association bridging to occur among the microspheres and enhance the plugging capability of the nano microspheres, so that large pores in the stratum are plugged effectively, and the water plugging and profile control effect is obvious.

In the above technical solution, the nonionic water-soluble monomer is preferably at least one of methacrylamide, N-isopropylacrylamide, N-dimethylacrylamide, N-diethylacrylamide, N-methylolacrylamide, N-vinylformamide, N-vinylacetamide, N-vinylpyridine, and N-vinylpyrrolidone.

In the technical scheme, the temperature-resistant and salt-resistant monomer is preferably at least one of 3-acrylamide-3-methylbutyrate sodium, 2-acrylamide-2-methylpropanesulfonic acid and acrylamide monomers.

In the technical scheme, the hydrophobic monomer is preferably a hydrophobic monomer with a cyclic structure, such as styrene and derivatives thereof, maleic anhydride, N-phenylmaleimide and the like,

hydrophobic monomers with long chain structures such as N-alkyl acrylate and anionic surface active monomers such as acrylamide sodium azaalkyl sulfonate with surface active vinyl carbon chain number of 8-18 or allylalkyl ammonium chloride with surface active vinyl carbon chain number of 12-22.

The hydrophobic monomer units are distributed in a hydrophobic association polymer macromolecular chain in a random or micro-block structure, so that the temperature resistance, salt resistance and aging resistance of the polymer are improved, the association among hydrophobic groups is easy to realize intermolecular association bridging, the polymer is decomposed under the shearing action and can recover after being sheared, and the retention rate of the viscosity of the polymer solution is improved. However, the reports on the hydrophobic association structure microspheres are less related.

In the above technical solution, the crosslinking agent is preferably at least one of N, N-methylene bisacrylamide, N-methylene bismethacrylamide, triallylamine, epichlorohydrin, polyethylene glycol diacrylate, divinylbenzene, polyethylene glycol diacrylate, ethylene glycol diacrylate, diallyldimethylammonium chloride, ethylene glycol dimethacrylate, pentaerythritol triacrylate, and N, N' -m-phenylene bismaleimide.

In the technical scheme, the solvent is preferably at least one of solvent naphtha, aliphatic hydrocarbon, aromatic hydrocarbon and alicyclic hydrocarbon; the solvent oil is at least one of kerosene and white oil; the aliphatic hydrocarbon is at least one of butane, pentane, octane, heptane and hexane; the aromatic hydrocarbon is at least one of benzene, toluene, ethylbenzene, xylene and cumene. The alicyclic compound is preferably at least one of cyclopentane, cyclohexane, methylcyclohexane and cyclooctane. It is also possible to use vegetable oils, preferably at least one of peanut oil, soybean oil, sunflower oil and castor oil.

In the technical scheme, the surfactant is a composite emulsifier system which comprises at least one of nonionic lipophilic surfactant, hydrophilic surfactant, cationic emulsifier and anionic emulsifier and surfactant for oil displacement, the hydrophilic-lipophilic balance value of the composite emulsifier is between 3 and 9, the common nonionic lipophilic surfactant and hydrophilic surfactant are Span (Span) system, the ingredients of the composite emulsifier are sorbitan ester, and addition products of alkylphenol and fatty alcohol respectively and ethylene oxide (the serial numbers of the commercial products are OP and MOA), or graft or block copolymer only with ethylene oxide chain links is adopted, such as PMMA-g-PEO and the like, and the cationic emulsifier is Cetyl Trimethyl Ammonium Bromide (CTAB), Dodecyl Trimethyl Ammonium Chloride (DTAC), tetradecyl-dimethyl pyridinium ammonium bromide and the like, the anionic emulsifier is mainly selected from sodium bis (2-ethylhexyl) sulfosuccinate (AOT), Sodium Dodecyl Sulfate (SDS), etc.;

the other part is a surfactant suitable for oil displacement of a high-temperature and high-salinity oil reservoir, such as a polyether carboxylate/sulfonate anionic/nonionic surfactant, alkanolamide, a betaine type amphoteric ion surfactant and the like, and the mass ratio of the two surfactants is adjusted, so that the hydrophilic-lipophilic balance value of an emulsifier system is between 3 and 9;

in order to increase the stability of the system, some alcohols or salts can be added as auxiliary emulsifying agents. Preferably, the surfactant is at least one of span 80, span 60, span 40, Tween 20, Tween 60, Tween 80, 0P-10 and TX-10.

In the above technical scheme, the initiator is preferably at least one selected from peroxide initiators, redox composite initiators and azo compounds; wherein, the peroxide initiator is preferably selected from at least one of ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide and benzoyl peroxide; the oxidizing agent in the redox composite initiator is preferably at least one of ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide and benzoyl peroxide, and the reducing agent is preferably at least one of sodium bisulfite, potassium bisulfite, sodium sulfite, potassium sulfite, sodium thiosulfate and ferrous chloride; the azo compound is preferably at least one selected from azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptonitrile, dimethyl azobisisobutyrate, azobisisobutylamidine hydrochloride, 2 '-azo [2- (2-imidazolin-2-yl) propane ] dihydrochloride, azobis (2, 5-dimethyl-6-carboxyl) hexanenitrile and 4, 4' -azobis (4-cyanovaleric acid); the initiator is more preferably a mixed initiator of a peroxide initiator, a redox complex initiator and an azo compound, wherein the mass ratio of the reducing agent in the peroxide initiator, the redox complex initiator and the azo compound is preferably 1: (1-5): (1-5).

To solve the second technical problem, the invention adopts the following technical scheme: the preparation method of the temperature-resistant and salt-resistant polyacrylamide microsphere comprises the following steps:

s1, preparation of an aqueous phase: dissolving acrylamide monomers, anionic hydrophilic monomers and cationic hydrophilic monomers in deionized water, and uniformly stirring; then adding a temperature-resistant and salt-resistant monomer, stirring and dissolving completely, and then adding a NaOH solution to adjust the pH value to 7.0; then adding a nonionic water-soluble monomer, a co-emulsifier and a cross-linking agent, uniformly stirring to obtain a water phase I, and respectively dissolving an oxidant and a reducing agent in water to form an oxidant water solution water phase II and a reducing agent water solution water phase III; controlling the temperature to be 15-30 ℃ in the stirring reaction process;

s2, preparation of polymerization solution: adding a hydrophobic monomer and a surfactant into a solvent, stirring and dissolving uniformly, then slowly adding the aqueous phase I solution prepared in the step S1, and stirring uniformly to obtain a transparent or semitransparent polymerization solution;

s3, polymerization: introducing an inert gas into the polymerization solution obtained in the step S2, and displacing oxygen to carry out the reaction under a deoxygenation condition; adding the water phase II prepared in the S1, controlling the initial temperature to be between 10 and 30 ℃, then adding an initiator, rapidly raising the temperature to be between 65 and 85 ℃, and then stirring for reaction for 0.5 to 1 hour to obtain a light yellow transparent emulsion; the polymerization reaction is carried out at a stirring speed of 300-500 r/min; the inert gas in the step S3 is at least one of helium, nitrogen and argon;

s4, phase transfer: and after the reaction is stable, reducing the temperature of the light yellow transparent emulsion obtained in the step S3 to 20-30 ℃, then adding a phase transfer agent, and uniformly stirring to obtain the light yellow transparent heat-resistant salt-resistant polyacrylamide nano microspheres.

The initiator in the S3 adopts a redox composite initiator; the dropping concentration of the redox composite initiator reducing agent solution (aqueous phase III prepared by S1) is 10wt%, and the dropping speed is 5 ml/h.

Compared with the prior art, the invention has the advantages that:

1) the temperature-resistant and salt-resistant polyacrylamide nano-microsphere prepared by the technical scheme of the invention has the advantages that the initial particle size of the polymer microsphere is 50-200 nm, the polymer microsphere still has good plugging performance after long-term aging under high temperature and high mineralization degree, the total mineralization degree range is 40000 mg/L-80000 mg/L, and the pore throat can be plugged in deep places under the environment at 90 ℃, so that the purposes of increasing oil and improving the recovery ratio are achieved.

2) According to the invention, cationic monomer and hydrophobic monomer units are introduced into the conventional acrylamide polymer microspheres, so that excellent temperature resistance, salt resistance and ageing resistance are shown; association bridging occurs among the microspheres, the gripping force among the microspheres and between the microspheres and the pore canal wall is improved, the large pore canal can be effectively blocked, the water shutoff profile control effect is obvious, and better technical effect is obtained.

3) According to application requirements, the temperature-resistant salt-resistant polyacrylamide microspheres can be directly dissolved and diluted by clear water, salt water or oilfield produced water, and can be applied to tertiary oil recovery as a water-plugging profile control agent alone or after being compounded with other oilfield chemicals to improve the crude oil recovery rate.

Detailed Description

The technical solution of the present invention is further illustrated below according to a number of examples. In the description of the present specification, the contents of each embodiment means that a specific technical feature described in connection with it is included in at least one embodiment of the present invention. In this specification, schematic representations of the embodiments do not necessarily refer to the same embodiment or example. Furthermore, the particular features described may be combined in any suitable manner in any one or more of the embodiments or examples.

Example 1

The preparation method of the temperature-resistant and salt-resistant polyacrylamide nano-microsphere comprises the following steps:

s1, preparation of an aqueous phase: 200g of acrylamide monomer, 30g of anionic hydrophilic monomer and 10g of cationic hydrophilic monomer are dissolved in deionized water, and the mixture is uniformly stirred at the speed of 250 r/min; then adding 50g of AMPS, stirring and dissolving completely, and then adding NaOH solution to adjust the PH value to 7.0; then adding 1g of methylene bisacrylamide monomer, 8g of isopropanol and 1g of crosslinking agent monomer (the crosslinking agent monomer is a mixture of N, N-methylene bisacrylamide and N, N-methylene bismethacrylamide, wherein the mass ratio of the N, N-methylene bisacrylamide to the N, N-methylene bismethacrylamide is 1: 1), stirring for 10min until the mixture is completely dissolved into a water phase I, and respectively dissolving 1g of potassium persulfate serving as an oxidizing agent and 1g of sodium bisulfite serving as a reducing agent in water to form an aqueous phase II serving as an oxidizing agent and an aqueous phase III serving as a sodium bisulfite serving as a reducing agent (10 wt%); controlling the temperature to be 25 ℃ in the stirring reaction process;

s2, preparation of polymerization solution: adding 5g of styrene monomer, 40g of S-80 and 60g of T-60 into 400g of white oil, stirring at the speed of 350r/min for 15min, dissolving uniformly, then slowly adding the aqueous phase I solution prepared in the step S1, stirring fully for 30min, and mixing uniformly to obtain a transparent polymerization solution;

s3, polymerization: introducing nitrogen gas into the polymerization solution of step S2 at a flow rate of 3L/min for 40min to displace oxygen gas, and allowing the reaction to proceed under deoxygenation conditions; adding the water phase II prepared in the S1, controlling the initial temperature to be 15 ℃, then dropwise adding a reducing agent sodium bisulfite solution at the dropping speed of 8ml/min, linearly increasing the temperature curve to be 80 ℃, and then stirring for reaction for 0.5 hour to obtain a light yellow transparent emulsion; wherein the stirring speed in the stirring process is 350 r/min;

s4, phase transfer: and after the reaction is stable, reducing the temperature of the faint yellow transparent and bright emulsion obtained in the step S3 to 25 ℃, then adding 30g of OP-10, and stirring at the speed of 250r/min for 30min to obtain the faint yellow transparent and bright temperature-resistant and salt-resistant polyacrylamide nano microspheres.

The temperature-resistant and salt-resistant polyacrylamide nano-microspheres obtained in the embodiment have an initial average particle size of 70 nm; the method is resistant to the high temperature of 90 ℃, and the total mineralization is resistant to the deep part of the stratum under the environment of 40000 mg/L-80000 mg/L; the water can smoothly enter the deep part of the stratum along with the injected water, and can be kept stable for 28 days after the water is gradually expanded after water absorption, so that effective plugging is formed at the pore throat of the water seepage channel.

Example 2

The preparation method of the temperature-resistant and salt-resistant polyacrylamide nano-microsphere comprises the following steps:

s1, preparation of an aqueous phase: dissolving 250g of acrylamide monomer, 10g of anionic hydrophilic monomer and 10g of cationic hydrophilic monomer in deionized water, and uniformly stirring at the speed of 250 r/min; then adding 30g of AMPS, stirring and dissolving completely, and then adding NaOH solution to adjust the PH value to 7.0; then adding 1g of methylene bisacrylamide monomer, 8g of isopropanol and 1g of crosslinking agent monomer (the crosslinking agent monomer is a mixture of N, N-methylene bisacrylamide and N, N-methylene bismethacrylamide, wherein the mass ratio of the N, N-methylene bisacrylamide to the N, N-methylene bismethacrylamide is 1: 1.5), stirring for 10min until the mixture is completely dissolved into a water phase I, and respectively dissolving 2g of potassium persulfate serving as an oxidizing agent and 2g of sodium bisulfite serving as a reducing agent in water to form an aqueous phase II serving as an oxidizing agent and an aqueous phase III serving as a sodium bisulfite serving as a reducing agent (10 wt%); controlling the temperature to be 25 ℃ in the stirring reaction process;

s2, preparation of polymerization solution: adding 5g of styrene monomer, 80g of S-80 and 40g of S-20 into 440g of white oil, stirring at the speed of 350r/min for 15min, dissolving uniformly, then slowly adding the aqueous phase I solution prepared in the step S1, stirring fully for 30min, and mixing uniformly to obtain a transparent polymerization solution;

s3, polymerization: introducing nitrogen gas into the polymerization solution of step S2 at a flow rate of 3L/min for 40min to displace oxygen gas, and allowing the reaction to proceed under deoxygenation conditions; adding the water phase II prepared in the S1, controlling the initial temperature to be 15 ℃, then dropwise adding a reducing agent sodium bisulfite solution at the dropping speed of 8ml/min, linearly increasing the temperature curve to be 80 ℃, and then stirring for reaction for 0.5 hour to obtain a light yellow transparent emulsion; wherein the stirring speed in the stirring process is 350 r/min;

s4, phase transfer: and after the reaction is stable, reducing the temperature of the light yellow transparent emulsion obtained in the step S3 to 25 ℃, then adding 20g of OP-10, and stirring at the speed of 250r/min for 30min to obtain the light yellow transparent temperature-resistant salt-resistant polyacrylamide nano microspheres.

The temperature-resistant and salt-resistant polyacrylamide nano-microspheres obtained in the embodiment have an initial average particle size of 90 nm; the method is resistant to the high temperature of 100 ℃ and the deep stratum in the environment with the total mineralization degree ranging from 40000mg/L to 80000 mg/L; the water can smoothly enter the deep part of the stratum along with the injected water, and can be kept stable for 35 days after the water is gradually expanded after water absorption, so that effective plugging is formed at the pore throat of the water seepage channel.

Example 3

The preparation method of the temperature-resistant and salt-resistant polyacrylamide nano-microsphere comprises the following steps:

s1, preparation of an aqueous phase: dissolving 250g of acrylamide monomer, 30g of anionic hydrophilic monomer and 15g of cationic hydrophilic monomer in deionized water, and uniformly stirring at the speed of 250 r/min; then adding 40g of AMPS, stirring and dissolving completely, and then adding NaOH solution to adjust the PH value to 7.0; then adding 1g of methylene bisacrylamide monomer, 8g of isopropanol and 1g of crosslinking agent monomer (the crosslinking agent monomer is a mixture of N, N-methylene bisacrylamide and N, N-methylene bismethacrylamide, wherein the mass ratio of the N, N-methylene bisacrylamide to the N, N-methylene bismethacrylamide is 1.5: 1), stirring for 10min until the mixture is completely dissolved into a water phase I, and respectively dissolving 2g of potassium persulfate serving as an oxidizing agent and 4g of sodium bisulfite serving as a reducing agent in water to form an aqueous phase II serving as an oxidizing agent and an aqueous phase III serving as a sodium bisulfite serving as a reducing agent (10 wt%); controlling the temperature to be 25 ℃ in the stirring reaction process;

s2, preparation of polymerization solution: adding 5g of styrene monomer, 80g of S-80 and 40g of T-60 into 480g of white oil, stirring at the speed of 350r/min for 15min, dissolving uniformly, then slowly adding the aqueous phase I solution prepared in the step S1, stirring fully for 30min, and mixing uniformly to obtain a transparent polymerization solution;

s3, polymerization: introducing nitrogen gas into the polymerization solution of step S2 at a flow rate of 3L/min for 40min to displace oxygen gas, and allowing the reaction to proceed under deoxygenation conditions; adding the water phase II prepared in the S1, controlling the initial temperature to be 15 ℃, then dropwise adding a reducing agent sodium bisulfite solution at the dropping speed of 8ml/min, linearly increasing the temperature curve to be 80 ℃, and then stirring for reaction for 0.5 hour to obtain a light yellow transparent emulsion; wherein the stirring speed in the stirring process is 350 r/min;

s4, phase transfer: and after the reaction is stable, reducing the temperature of the faint yellow transparent and bright emulsion obtained in the step S3 to 25 ℃, then adding 40g of TX-10, and stirring at the speed of 250r/min for 30min to obtain the faint yellow transparent and bright temperature-resistant and salt-resistant polyacrylamide nano microspheres.

The temperature-resistant and salt-resistant polyacrylamide nano-microspheres obtained in the embodiment have an initial average particle size of 110 nm; the high temperature of the stratum reaching 80 ℃ is resisted, and the deep stratum in the environment with the total mineralization degree range of 40000 mg/L-80000 mg/L is resisted; the water can smoothly enter the deep part of the stratum along with the injected water, and can be kept stable for 25 days after the water is gradually expanded after water absorption, so that effective plugging is formed at the pore throat of the water seepage channel.

Example 4

The preparation method of the temperature-resistant and salt-resistant polyacrylamide nano-microsphere comprises the following steps:

s1, preparation of an aqueous phase: 200g of acrylamide monomer, 30g of anionic hydrophilic monomer and 10g of cationic hydrophilic monomer are dissolved in deionized water, and the mixture is uniformly stirred at the speed of 250 r/min; then adding 50g of AMPS, stirring and dissolving completely, and then adding NaOH solution to adjust the PH value to 7.0; then adding 1g of methylene bisacrylamide monomer, 8g of isopropanol and 1g of crosslinking agent monomer (the crosslinking agent monomer is a mixture of N, N-methylene bisacrylamide and N, N-methylene bismethacrylamide, wherein the mass ratio of the N, N-methylene bisacrylamide to the N, N-methylene bismethacrylamide is 1: 1), stirring for 10min until the mixture is completely dissolved into a water phase I, and respectively dissolving 1g of potassium persulfate serving as an oxidizing agent and 1g of sodium bisulfite serving as a reducing agent in water to form an aqueous phase II serving as an oxidizing agent and an aqueous phase III serving as a sodium bisulfite serving as a reducing agent (10 wt%); controlling the temperature to be 25 ℃ in the stirring reaction process;

s2, preparation of polymerization solution: adding 5g of styrene monomer, 40g of S-80 and 60g of T-60 into 400g of white oil, stirring at the speed of 350r/min for 15min, dissolving uniformly, then slowly adding the aqueous phase I solution prepared in the step S1, stirring fully for 30min, and mixing uniformly to obtain a transparent polymerization solution;

s3, polymerization: introducing nitrogen gas into the polymerization solution of step S2 at a flow rate of 3L/min for 40min to displace oxygen gas, and allowing the reaction to proceed under deoxygenation conditions; adding the water phase II prepared in the S1, controlling the initial temperature to be 25 ℃, then dropwise adding a reducing agent sodium bisulfite solution at the dropping speed of 4ml/min, raising the temperature to be 60 ℃, and then stirring for reacting for 3 hours to obtain a light yellow transparent emulsion; wherein the stirring speed in the stirring process is 350 r/min;

s4, phase transfer: and after the reaction is stable, reducing the temperature of the faint yellow transparent and bright emulsion obtained in the step S3 to 25 ℃, then adding 30g of OP-10, and stirring at the speed of 250r/min for 30min to obtain the faint yellow transparent and bright temperature-resistant and salt-resistant polyacrylamide nano microspheres.

The temperature-resistant and salt-resistant polyacrylamide nano-microspheres obtained in the embodiment have an initial average particle size of 11 μm; the high temperature of the stratum reaching 85 ℃ is resisted, and the deep stratum in the environment with the total mineralization degree range of 40000 mg/L-80000 mg/L is resisted; the water can smoothly enter the deep part of the stratum along with the injected water, and the stability can be maintained for 30 days after the water absorption is gradually expanded, so that the effective plugging is formed at the pore throat of the water seepage channel. 2.360 mu m under the condition of 85 ℃ and the total mineralization of 80000mg/L, wherein the concentration of calcium and magnesium ions is 2000mg/L²The plugging efficiency of core plugging can reach more than 80%, the water plugging and profile control effect is obvious, and a better technical effect is achieved.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.

Claims (10)

1. The temperature-resistant and salt-resistant polyacrylamide nano microsphere is characterized by comprising the following components in percentage by mass: 20-30% of acrylamide monomer, 1-3% of anionic hydrophilic monomer, 1-3% of cationic hydrophilic monomer, 0.1-0.5% of nonionic water-soluble monomer, 3-8% of temperature-resistant salt-resistant monomer, 0.1-0.5% of hydrophobic monomer, 0.01-0.05% of cross-linking agent, 40-48% of solvent, 10-16% of surfactant, 0.01-0.05% of initiator, 2-6% of phase transfer agent and the balance of deionized water.

2. The temperature-resistant and salt-resistant polyacrylamide nano-microsphere according to claim 1, which is characterized in that: the anionic hydrophilic monomer is at least one of acrylic acid, methacrylic acid, maleic acid, itaconic acid and vinyl benzene sulfonic acid; the cationic hydrophilic monomer is at least one of dimethyl ethyl allyl ammonium chloride, dimethyl diallyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl dimethyl ethyl ammonium bromide, methacryloyloxyethyl trimethyl ammonium chloride and 2-acrylamido-2-methylpropyl trimethyl ammonium chloride.

3. The temperature-resistant and salt-resistant polyacrylamide nano-microsphere according to claim 1, which is characterized in that: the non-ionic water-soluble monomer is at least one of methacrylamide, N-isopropyl acrylamide, N-dimethyl acrylamide, N-diethyl acrylamide, N-hydroxymethyl acrylamide, N-vinyl formamide, N-vinyl acetamide, N-vinyl pyridine and N-vinyl pyrrolidone.

4. The temperature-resistant and salt-resistant polyacrylamide nano-microsphere according to claim 1, which is characterized in that: the temperature-resistant and salt-resistant monomer is at least one of 3-acrylamide-3-sodium methylbutyrate, 2-acrylamide-2-methylpropanesulfonic acid and acrylamide monomers.

5. The temperature-resistant and salt-resistant polyacrylamide nano-microsphere according to claim 1, which is characterized in that: the hydrophobic monomer is a hydrophobic monomer with a ring structure and comprises styrene and derivatives thereof, maleic anhydride and N-phenylmaleimide; or the hydrophobic monomer with a long-chain structure comprises N-alkyl acrylate, or acrylamide sodium azaalkylsulfonate anionic surface active monomer with a vinyl carbon chain number of 8-18, or allyl alkyl ammonium chloride cationic surface active monomer with a vinyl carbon chain number of 12-22.

6. The temperature-resistant and salt-resistant polyacrylamide nano-microsphere according to claim 1, which is characterized in that: the cross-linking agent is at least one of N, N-methylene bisacrylamide, N-methylene bismethacrylamide, triallylamine, epichlorohydrin, polyethylene glycol diacrylate, divinylbenzene, polyethylene glycol diacrylate, ethylene glycol diacrylate, diallyl dimethyl ammonium chloride, ethylene glycol dimethacrylate, pentaerythritol triacrylate and N, N' -m-phenylene bismaleimide.

7. The temperature-resistant and salt-resistant polyacrylamide nano-microsphere according to claim 1, which is characterized in that: the solvent is at least one of solvent oil, aliphatic hydrocarbon, aromatic hydrocarbon or alicyclic compound; the solvent oil is at least one of kerosene and white oil; the aliphatic hydrocarbon is at least one of butane, pentane, octane, heptane and hexane; the aromatic hydrocarbon is at least one of benzene, toluene, ethylbenzene, xylene and cumene; the alicyclic compound is at least one of cyclopentane, cyclohexane, methylcyclohexane and cyclooctane, or at least one of vegetable oil, peanut oil, soybean oil, sunflower seed oil and castor oil.

8. The temperature-resistant and salt-resistant polyacrylamide nano-microsphere according to claim 1, which is characterized in that: the surfactant is a composite emulsifier system and comprises at least one of nonionic lipophilic surfactant, hydrophilic surfactant, cationic emulsifier and anionic emulsifier, specifically at least one of span 80, span 60, span 40, tween 20, tween 60, tween 80, 0P-10 and TX-10; and surfactant for oil displacement, wherein the hydrophilic-lipophilic balance value of the composite emulsifier is between 3 and 9; the other part is a surfactant suitable for high-temperature and high-salt reservoir oil displacement, and comprises polyether carboxylate/sulfonate anionic/non-surfactant, alkanolamide and betaine type amphoteric ion surfactant.

9. The temperature-resistant and salt-resistant polyacrylamide nano-microsphere according to claim 1, which is characterized in that: the initiator is at least one of a peroxide initiator, a redox composite initiator and an azo compound, and further is a mixed initiator of the peroxide initiator, the redox composite initiator and the azo compound, wherein the mass ratio of the reducing agent in the peroxide initiator, the redox composite initiator and the azo compound is 1: (1-5): (1-5); wherein the peroxide initiator is at least one of ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide and benzoyl peroxide; the redox composite initiator comprises an oxidant, a reducing agent and a redox composite initiator, wherein the oxidant is at least one of ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide and benzoyl peroxide, and the reducing agent is at least one of sodium bisulfite, potassium bisulfite, sodium sulfite, potassium sulfite, sodium thiosulfate and ferrous chloride; the azo compound is at least one of azodiisobutyronitrile, azodiisovaleronitrile, azodiisoheptanonitrile, azodiisobutyl dimethyl isobutyrate, azodiisobutyl amidine hydrochloride, 2 '-azo [2- (2-imidazoline-2-yl) propane ] dihydrochloride, azodi (2, 5-dimethyl-6-carboxyl) hexanenitrile and 4, 4' -azobis (4-cyano valeric acid).

10. A method for preparing the temperature-resistant and salt-tolerant polyacrylamide nano-microspheres according to any one of claims 1-9, which comprises the following steps:

s1, preparation of an aqueous phase: dissolving acrylamide monomers, anionic hydrophilic monomers and cationic hydrophilic monomers in deionized water, and uniformly stirring; then adding a temperature-resistant and salt-resistant monomer, stirring and dissolving completely, and then adding a NaOH solution to adjust the pH value to 7.0; then adding a nonionic water-soluble monomer, a co-emulsifier and a cross-linking agent, uniformly stirring to obtain a water phase I, and respectively dissolving an oxidant and a reducing agent in water to form an oxidant water solution water phase II and a reducing agent water solution water phase III; controlling the temperature to be 15-30 ℃ in the stirring reaction process;

s2, preparation of polymerization solution: adding a hydrophobic monomer and a surfactant into a solvent, stirring and dissolving uniformly, then slowly adding the aqueous phase I solution prepared in the step S1, and stirring uniformly to obtain a transparent or semitransparent polymerization solution;

s3, polymerization: introducing an inert gas into the polymerization solution obtained in the step S2, and displacing oxygen to carry out the reaction under a deoxygenation condition; adding the aqueous phase II prepared in the step S1, controlling the initial initiation temperature to be 10-30 ℃, then adding an initiator, specifically adopting a redox composite initiator, wherein the dropwise adding concentration of the aqueous phase III of the reducing agent is 10wt%, and the dropwise adding speed is 5 ml/h; rapidly raising the temperature to 65-85 ℃, and then stirring for reaction for 0.5-1 hour to obtain a light yellow transparent emulsion; the polymerization reaction is carried out at a stirring speed of 300-500 r/min; the inert gas in the step S3 is at least one of helium, nitrogen and argon;

s4, phase transfer: and after the reaction is stable, reducing the temperature of the light yellow transparent emulsion obtained in the step S3 to 20-30 ℃, then adding a phase transfer agent, and uniformly stirring to obtain the light yellow transparent heat-resistant salt-resistant polyacrylamide nano microspheres.