CN115449017B - Star polymer filtrate reducer and preparation method thereof - Google Patents

Abstract

The invention provides a star polymer filtrate reducer and a preparation method thereof, belonging to the technical field of oilfield chemistry, wherein the preparation method comprises the following steps: uniformly mixing a trithio chain transfer agent, a water-soluble emulsifier, an inorganic salt water phase stabilizer, an inorganic peroxy initiator, a metal complexing agent, a molecular weight regulator and an acrylic acid-sulfonate aqueous solution to obtain a water phase solution; mixing oil and oil-soluble emulsifier to obtain oil phase solution; adding the aqueous phase solution into the oil phase solution, emulsifying to obtain water-in-oil emulsion, adding a reducing agent aqueous solution into the water-in-oil emulsion, and reacting to obtain a first product solution; sequentially adding an aqueous solution containing an acrylamide monomer and a branching agent and an aqueous solution containing the acrylamide monomer, a nucleating agent and a temperature stabilizer into emulsion for reaction to obtain the star polymer filtrate reducer; the fluid loss additive has the advantages of good fluid loss effect, excellent temperature resistance and salt resistance and high dissolution speed.

Description

Star polymer filtrate reducer and preparation method thereof

Technical Field

The invention relates to the technical field of oilfield chemistry, in particular to a star polymer filtrate reducer and a preparation method thereof.

Background

With the continuous aggravation of contradiction between the reduction of the shallow oil reservoir content and the increase of the energy demand, the oil fields at home and abroad are more dedicated to drilling deep wells and complex wells, the stratum where the oil and gas reservoirs are located is more and more complex in environment, so that the drilling fluid technology is more challenged, the original drilling fluid treatment agent and the drilling fluid system can not completely meet the requirements of the development of the deep well and ultra-deep well drilling technology, and the development of the high-temperature resistant drilling fluid treatment agent and the drilling fluid system is being attempted in various countries in the world.

In the drilling process, the property that free water in the drilling fluid permeates into the stratum through the well wall under the action of pressure difference becomes the fluid loss property of the drilling fluid; the excessive filtration loss of the drilling fluid in the drilling process not only can damage the oil and gas layer and reduce the productivity and the well wall collapse and other problems, but also can easily cause drilling accidents. At present, a conventional drilling fluid filtrate reducer such as polyacrylamide is mainly of a linear structure, in order to improve the filtrate reducing performance of the filtrate reducer, a structural functional group or a hydrophobic association monomer is generally enlarged on the basis of the linear structure, but the structure has the defects of easy curling and easy failure under severe conditions such as high temperature, high salt and the like, and meanwhile, the solubility of the filtrate reducer is poor, so that in order to solve the problems, a filtrate reducer with good filtrate reducing effect, excellent temperature and salt resistance and good solubility needs to be studied.

Disclosure of Invention

The invention provides a star polymer fluid loss additive and a preparation method thereof, and the prepared fluid loss additive is of a multi-arm star hyperbranched structure and has the advantages of good fluid loss effect, excellent temperature resistance and salt resistance and high dissolution speed.

In a first aspect, the invention provides a method for preparing a star polymer fluid loss additive, comprising the following steps:

(1) Uniformly mixing a trithio chain transfer agent, a water-soluble emulsifier, an inorganic salt water phase stabilizer, an inorganic peroxy initiator, a metal complexing agent, a molecular weight regulator and an acrylic acid-sulfonate aqueous solution to obtain a water phase solution; mixing oil and oil-soluble emulsifier to obtain oil phase solution;

the acrylic acid-sulfonate aqueous solution is prepared from acrylic acid monomers, sulfonate monomers and alkaline substances through a neutralization reaction;

(2) Adding the aqueous phase solution into the oil phase solution, emulsifying to obtain water-in-oil emulsion, adding a reducing agent aqueous solution into the water-in-oil emulsion, and reacting to obtain a first product solution;

(3) Sequentially adding an organic peroxy initiator and an aqueous solution containing an acrylamide monomer and a branching agent into the first product solution, and reacting to obtain a second product solution;

(4) And sequentially adding an azo initiator and an aqueous solution containing an acrylamide monomer, a nucleating agent and a temperature stabilizer into the second product solution, adding a phase inversion agent after reaction, and uniformly mixing to obtain the star polymer filtrate reducer.

Preferably, in step (1), the acrylic acid-sulfonate aqueous solution is prepared as follows: uniformly mixing an acrylic monomer, a sulfonate monomer and water, adding an alkaline substance for neutralization reaction, and obtaining an acrylic acid-sulfonate aqueous solution after the neutralization reaction;

when the acrylic acid-sulfonate aqueous solution is prepared, the addition amounts of the raw material components are as follows: 35-38% of acrylic monomer, 15-17% of sulfonate monomer, 18-20% of alkaline substance and 25-32% of water.

Preferably, in the step (1), the temperature of the neutralization reaction is 10-15 ℃.

Preferably, in step (1), the acrylic monomer is at least one of acrylic acid, methacrylic acid, 2-bromoacrylic acid, 2-furoic acid, 2-propylacrylic acid, or 2-ethylacrylic acid;

the sulfonate monomer is at least one of vinyl sulfonic acid, 7-amino-4-hydroxy-2-naphthalene sulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid or [2- (methacryloyloxy) ethyl ] dimethyl- (3-sulfopropyl) ammonium hydroxide;

The alkaline substance is at least one of sodium hydroxide, potassium hydroxide or ammonia water.

Preferably, in step (1), the trithio-based chain transfer agent is at least one of dimethyl trithiocarbonate, bis (carboxymethyl) trithiocarbonate, cyanomethyl dodecyl trithiocarbonate, S-dibenzyl trithiocarbonate, 2-cyano-2-propyldodecyl trithiocarbonate or 2- (dodecyl trithiocarbonate group) -2-methylpropanoic acid;

the water-soluble emulsifier is at least one of polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monostearate, polyoxyethylene mountain plow anhydride tristearate or polyoxyethylene sorbitan monooleate;

the inorganic salt water phase stabilizer is at least one of ammonium sulfate, sodium acetate and ammonium chloride;

the inorganic peroxy initiator is at least one of lithium peroxide, potassium persulfate or zinc peroxide;

the metal complexing agent is at least one of diethylenetriamine pentamethylene phosphonic acid, ethylenediamine tetraacetic acid or nitrilotriacetic acid;

the molecular weight regulator is at least one of sodium propionate, sodium succinate or sodium salicylate.

Preferably, in step (1), the oil is at least one of white oil, kerosene or rapeseed oil; the oil-soluble emulsifier is at least one of sorbitan monopalmitate, sorbitan monolaurate, sorbitan oleate or sorbitan oleate triester.

Preferably, in the step (1), when preparing the star polymer filtrate reducer, the addition amounts of the raw material components in the aqueous phase solution are as follows: 2-2.5% of trithio chain transfer agent, 3-4% of water-soluble emulsifier, 0.8-1.1% of inorganic salt water phase stabilizer, 0.0086-0.0089% of inorganic peroxy initiator, 0.0065-0.0071% of metal complexing agent, 0.0095-0.011% of molecular weight regulator and 28-29% of acrylic acid-sulfonate aqueous solution.

Preferably, in the step (1), when preparing the star polymer filtrate reducer, the addition amounts of the raw material components in the oil phase solution are as follows: 23-24% of oil and 3-4% of oil-soluble emulsifier.

Preferably, in the step (2), the reducing agent in the aqueous solution of the reducing agent is at least one of sodium chlorite, cuprous sulfide, potassium metabisulfite and sodium thiosulfate;

when the star polymer filtrate reducer is prepared, the addition amount of the aqueous solution of the reducer is 0.012-0.014%.

Preferably, in the step (2), the mass concentration of the aqueous solution of the reducing agent is 0.8-1.1%; the adding speed of the aqueous solution of the reducing agent is 3-5 mL/h, and the adding time is 1.8-2 h.

Preferably, in the step (3), the organic peroxygen initiator is at least one of tert-butyl peroxybenzoate, cumene peroxide or diisopropylbenzene peroxide;

the acrylamide monomer is at least one of acrylamide, methacrylamide, N-isopropyl acrylamide, N-tertiary butyl acrylamide or N- (trityl) methacrylamide;

the branching agent is at least one of 16-hydroxy hexadecanoic acid, butyl p-hydroxybenzoate, 4' -hydroxybutyrylaniline, 4-hydroxy-1-naphthalene sulfonic acid sodium salt or 11-hydroxy undecyl phosphoric acid.

Preferably, in step (3), when preparing the star polymer fluid loss additive, the addition amounts of each raw material component in the second product solution are as follows: 0.0085-0.0087% of organic peroxide initiator, 7-8% of acrylamide monomer, 2-3% of branching agent and 7-8% of water.

Preferably, in the step (4), the azo initiator is at least one of diisopropyl azodicarboxylate, dibenzyl azodicarboxylate, di-2-methoxyethyl azodicarboxylate or bis (4-chlorobenzyl) azodicarboxylate;

The nucleating agent is at least one of diallyl disulfide, 1, 5-hexadiene, allyl disulfide, diallyl carbonate or diallyl amine;

the temperature stabilizer is at least one of N-phenylthiourea, thiosemicarbazide, 4-methyl thiosemicarbazide or benzyl mercaptan;

the phase inversion agent is at least one of trideceth (18) ether, polyethylene glycol (12) trideceth, hexaethylene glycol dodecyl ether or decaethylene glycol monoldodecyl ether.

Preferably, in the step (4), when preparing the star polymer filtrate reducer, the addition amounts of the raw material components in the step (4) are as follows: 0.012-0.013% of azo initiator, 6-7% of acrylamide monomer, 0.5-0.7% of nucleating agent, 0.8-1.1% of temperature stabilizer, 5.6-15.6% of water and 1.3-1.5% of phase inversion agent.

Preferably, in the step (1), the method further comprises the step of adjusting the pH of the aqueous phase solution to 7.9-8.0 by using the alkaline substance;

in the step (2), the reaction temperature is 25-30 ℃, and the reaction time is 1.8-2 h;

in the step (3), the reaction temperature is 35-40 ℃, and the reaction time is 2-2.5 h;

in the step (4), the reaction temperature is 50-55 ℃, and the reaction time is 2-2.5 h.

Preferably, the reaction is carried out under the condition of nitrogen, and the nitrogen introducing time is 30-35 min.

In a second aspect, the invention provides a star polymer fluid loss additive, which is prepared by the preparation method in any one of the first aspects.

Compared with the prior art, the invention has at least the following beneficial effects:

(1) According to the invention, the trithio chain transfer agent and the acrylic acid-sulfonate aqueous solution are introduced into the aqueous solution, the trithio chain transfer agent can enable reversible addition-fragmentation chain transfer free radical polymerization reaction to occur between monomers, and compared with common free radical polymerization, most of free radicals in the polymerization reaction are generated in the initial stage of the reaction, so that most of molecular chains can be ensured to have the same initial growth time, and meanwhile, the polymerization reaction can provide the same growth possibility for all the molecular chains, so that the uniform length and charge concentration of each arm of the star polymer can be ensured, and the prepared star polymer has the advantages of narrow molecular weight distribution, good solubility, low viscosity, high activity and the like; simultaneously, sulfonate groups with larger steric hindrance, long-chain groups and benzene ring structures are respectively introduced in the process of synthesizing the arm head and the arm trunk, so that the temperature resistance and salt resistance of the star polymer filtrate reducer are obviously improved on the basis of ensuring the excellent filtrate reduction performance and solubility of the star polymer filtrate reducer;

(2) According to the invention, the acrylamide monomer and the nucleating agent are mixed for nucleation reaction, the nucleating agent can be used for connecting amide groups in a chemical combination and physical mode to form a spherical cross-linkable 'core' structure, the 'core' structure can be further polymerized with active groups in an 'arm' structure, so that a multi-arm star-shaped polymer is formed, the viscosity of a polymer solution in the invention is lower than that of a linear polymer solution with the same molecular weight, and the polymer solution has the advantages of smaller hydrodynamic force and symmetrical structure;

(3) According to the invention, the inorganic salt water phase stabilizer is added into the water phase solution, so that the water phase solution system can be stabilized in the water-in-oil emulsion system, the emulsification effect is improved, and further, demulsification is effectively avoided in the inverse emulsion polymerization process; meanwhile, the phase inversion agent is added after polymerization is finished, so that the dissolution rate of the polymer can be further improved, and the star polymer filtrate reducer has the advantages of quick dissolution, good dispersibility and convenience in field application;

(4) The filtrate reducer prepared by the invention is of a multi-arm star-shaped hyperbranched structure, has the advantages of both hyperbranched structure and star-shaped structure, not only has excellent filtrate reducing performance, but also has the advantages of narrow molecular weight distribution coefficient, low molecular weight, low solution viscosity, concentrated charge, quick dissolution, temperature resistance, salt resistance, shearing resistance, convenient application and the like, the viscosity-phase molecular mass is 180-230 ten thousand, the relative molecular mass distribution coefficient PDI is less than or equal to 1.3, the composite salt water-based slurry filtrate loss is less than or equal to 15mL at 220 ℃, and the composite salt water-based slurry filtrate loss rate is more than or equal to 85%.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments, and all other embodiments obtained by persons of ordinary skill in the art without making creative efforts based on the embodiments of the present invention are all within the scope of protection of the present invention.

The invention provides a preparation method of a star polymer filtrate reducer, which comprises the following steps:

(1) Uniformly mixing a trithio chain transfer agent, a water-soluble emulsifier, an inorganic salt water phase stabilizer, an inorganic peroxy initiator, a metal complexing agent, a molecular weight regulator and an acrylate-sulfonate aqueous solution to obtain a water phase solution; mixing oil and oil-soluble emulsifier to obtain oil phase solution;

the acrylic acid salt-sulfonate aqueous solution is prepared from acrylic acid monomers, sulfonate monomers and alkaline substances through a neutralization reaction;

(2) Adding the aqueous phase solution into the oil phase solution, emulsifying to obtain water-in-oil emulsion, adding a reducing agent aqueous solution into the water-in-oil emulsion, and reacting to obtain a first product solution; firstly, generating a linear structural chain with uniform molecular chain length distribution and concentrated charge distribution through reversible addition-fragmentation chain transfer polymerization, wherein the structural chain is used as an arm head of a star polymer;

(3) Sequentially adding an organic peroxy initiator and an aqueous solution containing an acrylamide monomer and a branching agent into the first product solution, and reacting to obtain a second product solution; the amide groups in the acrylamide monomer can be subjected to hydrogen bond substitution reaction with a branching agent to obtain an 'arm trunk' with a hyperbranched structure, and then the arm trunk is initiated by an initiator to connect the 'arm head' and the 'arm trunk', so that a complete 'arm' is formed;

(4) Sequentially adding an azo initiator and an aqueous solution containing an acrylamide monomer, a nucleating agent and a temperature stabilizer into the second product solution, adding a phase inversion agent after reaction, and uniformly mixing to obtain the star polymer filtrate reducer; the nucleating agent can perform nucleation reaction with acrylamide monomers to form spherical cores, and then the spherical cores are initiated by an initiator, active groups in the arm stems can further polymerize with the cores to form the multi-arm star-shaped hyperbranched structure polymer, and the arm length and the arm number of the final polymer can be adjusted by adjusting the addition proportion of the acrylamide monomers in the arm forming process, wherein the arm number of the star-shaped polymer is preferably 5-10;

The invention adopts a 'first arm and then core' method to prepare a star polymer filtrate reducer, firstly adopts a reversible addition-fragmentation chain transfer free radical polymerization method to respectively prepare an 'arm head' of a linear structure and an 'arm stem' of a hyperbranched structure, the linear structure chain and the hyperbranched structure chain are further connected together through covalent bonds, and the crosslinkable 'core' and active groups in the hyperbranched structure chain are further polymerized to form a multi-arm star hyperbranched polymer; the sulfonate groups can be arranged in a block manner on a linear chain, meanwhile, the long-chain groups and the benzene ring groups are contained on the 'arm trunk' branched chains, the sulfonate groups, the long-chain groups and the benzene ring groups in the 'arm head' and 'arm trunk' structures have larger steric hindrance, the main chain structure can be better protected under the conditions of high temperature and high salt, the main chain structure has good temperature resistance and salt resistance, and the 'arm' of the star polymer can be ensured to be more stretched through the mutual repulsive interaction among the sulfonate groups, so that the excellent filtrate loss reducing performance of the final filtrate loss reducing agent is ensured; the multi-arm star-shaped hyperbranched structure polymer filtrate reducer is finally prepared through the mutual coordination of reversible addition-fragmentation chain transfer free radical polymerization reaction, grafting reaction and nucleation reaction, and the filtrate reducer has the advantages of hyperbranched structure and star-shaped structure; reversible addition-fragmentation chain transfer radical polymerization is a double bond addition and fragmentation reaction based on a propagating radical with a compound containing a structure of-s=c-S, which enables active propagation of the polymer chain, which is mostly generated at the initial stage of the reaction, except for chain initiation, chain propagation and chain termination reactions, in comparison with the general radical polymerization, so that most of the chains have the same initial growth time; meanwhile, the polymerization reaction increases reversible chain addition and fracture processes, so that the equal possibility of growth is provided for all chains, the uniform chain length of the arm head part reaction can be ensured, the charge is concentrated, and the polymer filtrate reducer has the advantages of narrow molecular weight distribution, good solubility, low bulk and solution viscosity, high activity and the like.

According to some preferred embodiments, in step (1), the preparation method of the aqueous acrylate-sulfonate solution is as follows: uniformly mixing an acrylic monomer, a sulfonate monomer and water, adding an alkaline substance for neutralization reaction, and obtaining an acrylic acid salt-sulfonate aqueous solution after the neutralization reaction; in order to introduce sulfonate groups into a polymerization reaction, so that the sulfonate groups form linear structural chains in block arrangement in the water-in-oil inverse emulsion polymerization process, the invention firstly performs neutralization reaction with acrylic acid and sulfonate monomers and alkaline substances to form acrylic acid-sulfonate aqueous solution, and then mixes the aqueous solution with trithio chain transfer agent and the like to obtain aqueous solution, thereby not only ensuring that the water-in-oil inverse emulsion polymerization process is controllable, but also being more beneficial to forming linear structural chains in block arrangement of sulfonate groups, wherein the chain length distribution is uniform;

when the acrylic acid-sulfonate aqueous solution is prepared, the addition amounts of the raw material components are as follows: 35-38% (35%, 35.5%, 36%, 36.5%, 37%, 37.5% or 38%), 15-17% (15%, 15.5%, 16%, 16.5% or 17%) of a sulfonate monomer, 18-20% (e.g., 18%, 18.5%, 19%, 19.5% or 20%) of a basic substance, 25-32% (e.g., 25%, 26%, 27%, 28%, 29%, 30%, 31% or 32%) of water; in the invention, because the sulfonic acid group in the sulfonate monomer has the characteristics of large steric hindrance and high charge density, the salt resistance of a molecular chain can be improved, if the addition amount of the sulfonate monomer is lower than the range, the formation of the molecular chain with high salt resistance is not facilitated, and if the addition amount of the sulfonate monomer is higher than the range, the salt resistance can be improved to a certain extent, but the cost of the reaction can be correspondingly improved; the addition amounts of the components in the invention are expressed in mass percent.

According to some preferred embodiments, in the step (1), the neutralization reaction temperature is 10 to 15 ℃ (10 ℃, 11 ℃, 12 ℃, 13 ℃, 14 ℃ or 15 ℃), and the reaction time is h (for example, may be); and (3) during the neutralization reaction, testing the pH value of the solution by adopting a pH meter, and stopping adding the alkaline substance when the pH value of the solution is 7.0-7.05.

According to some preferred embodiments, in step (1), the acrylic monomer is at least one of acrylic acid, methacrylic acid, 2-bromoacrylic acid, 2-furanacrylic acid, 2-propylacrylic acid or 2-ethylacrylic acid; the sulfonate monomer is at least one of vinyl sulfonic acid, 7-amino-4-hydroxy-2-naphthalene sulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid or [2- (methacryloyloxy) ethyl ] dimethyl- (3-sulfopropyl) ammonium hydroxide; the sulfonate monomer not only contains sulfonic acid groups, but also contains double bond structures capable of participating in reaction, so that the sulfonic acid groups are more beneficial to block arrangement on a molecular chain; the alkaline substance is at least one of sodium hydroxide, potassium hydroxide or ammonia water; potassium hydroxide is preferred in the present invention.

According to some preferred embodiments, in step (1), the trithio-based chain transfer agent is at least one of dimethyl trithiocarbonate, bis (carboxymethyl) trithiocarbonate, cyanomethyl dodecyl trithiocarbonate, S-dibenzyl trithiocarbonate, 2-cyano-2-propyldodecyl trithiocarbonate or 2- (dodecyl trithiocarbonate group) -2-methylpropanoic acid; according to the invention, the trithio chain transfer agent, the water-soluble emulsifier, the inorganic salt aqueous phase stabilizer and the like are added into the aqueous phase solution, the aqueous phase solution and the oil phase solution are emulsified to form the water-in-oil emulsion, and the addition of the trithio chain transfer agent can enable the reversible addition-fragmentation chain transfer free radical inverse emulsion polymerization reaction to occur in the invention, so that most chains can have the same initial growth time and the same chain growth possibility, thereby forming a linear structure 'arm head' with uniform chain length distribution and concentrated charge distribution; the water-soluble emulsifier is at least one of polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monostearate, polyoxyethylene mountain plow anhydride tristearate or polyoxyethylene sorbitan monooleate; the inorganic salt water phase stabilizer is at least one of ammonium sulfate, sodium acetate and ammonium chloride; meanwhile, in order to further stabilize the water phase system in the water-in-oil emulsion, the inorganic salt water phase stabilizer is added into the water phase solution, so that the emulsion effect of the water-in-oil emulsion can be improved, the stability of the water-in-oil emulsion can be improved, and the demulsification phenomenon in the reverse phase polymerization process is avoided; the inorganic peroxy initiator is at least one of lithium peroxide, potassium persulfate or zinc peroxide; the metal complexing agent is at least one of diethylenetriamine pentamethylene phosphonic acid, ethylenediamine tetraacetic acid or nitrilotriacetic acid; the molecular weight regulator is at least one of sodium propionate, sodium succinate or sodium salicylate.

According to some preferred embodiments, in step (1), the oil is at least one of white oil, kerosene or rapeseed oil; the oil-soluble emulsifier is at least one of sorbitan monopalmitate, sorbitan monolaurate, sorbitan oleate or sorbitan oleate triester.

According to some preferred embodiments, in step (1), in preparing the star polymer fluid loss additive, the following raw material components are added to the aqueous phase solution: 2 to 2.5% (for example, 2%, 2.1%, 2.2%, 2.3%, 2.4% or 2.5%) of a trithio-based chain transfer agent, 3 to 4% (for example, 3%, 3.2%, 3.5%, 3.7% or 4%) of a water-soluble emulsifier, 0.8 to 1.1% (for example, 0.8%, 0.9%, 1.0% or 1.1%) of an inorganic salt aqueous phase stabilizer, 0.0086 to 0.0089% (for example, 0.0086%, 0.0087%, 0.0088% or 0.0089%, 0.0065-0.0071% metal complexing agent (e.g. 0.0065%, 0.0068%, 0.0070% or 0.0071%), molecular weight regulator 0.0095-0.011% (e.g. 0.0095%, 0.0097%, 0.0099% or 0.011%) and 28-29% (e.g. 28.2%, 28.5%, 28.7%, 28.9% or 29%) of acrylate-sulfonate aqueous solution; in the invention, the water-in-oil emulsion reverse phase polymerization formed by emulsifying the water-phase emulsion and the oil-phase emulsion firstly forms a linear structure chain with uniform chain length distribution, the addition of the trithio chain transfer agent can ensure that the reversible addition-fragmentation chain transfer polymerization reaction occurs in the invention, and the experiment proves that if the addition amount of the trithio chain transfer agent is lower than the range, the reversible addition-fragmentation chain transfer polymerization reaction can occur in each component, thereby causing the formation of the multi-arm star-shaped hyperbranched polymer structure in the invention to be unfavorable; if the addition amount of the trithio chain transfer agent is higher than the above range, the molecular chain becomes shorter in the polymerization reaction process, and the properties such as filtration reduction and the like of the polymer are finally adversely affected; the water-soluble emulsifier can reduce the interfacial tension of each component in the water-in-oil system, ensure that the disperse phase is dispersed in the continuous phase in the form of micro-droplets in the emulsification process, keep a uniform emulsifying state, and the inorganic salt water phase stabilizer can further stabilize the emulsion system and avoid demulsification; in the invention, the addition amount of the inorganic salt water phase stabilizer is lower or higher than the range, which is not beneficial to effectively improving the stability of the polymer emulsion system; meanwhile, in the invention, the acrylate-sulfonate aqueous solution can introduce sulfonate groups into a molecular chain, so that the temperature resistance and salt resistance of polymer molecules are improved, if the content of the acrylate-sulfonate aqueous solution is lower than the range, the temperature resistance and salt resistance of the polymer cannot be effectively improved, and if the content of the acrylate-sulfonate aqueous solution is higher than the range, the temperature resistance and salt resistance of the polymer can be further improved to a certain extent, but the total solid content is increased, the system is easy to be unstable, and the cost is increased; therefore, the content of each component in the aqueous phase solution is controlled within the range, which is more beneficial to ensuring the formation of the polymer filtrate reducer with narrow molecular weight coefficient distribution, good solubility, good temperature resistance and salt resistance and good filtrate reduction effect.

According to some preferred embodiments, in step (1), when preparing the star polymer fluid loss additive, the addition amounts of each raw material component in the oil phase solution are as follows: 23-24% (e.g., 23%, 23.2%, 23.5%, 23.8%, or 25%) of oil, 3-4% (e.g., 3%, 3.2%, 3.5%, 3.8%, or 4%) of oil-soluble emulsifier.

According to some preferred embodiments, in step (2), the reducing agent in the aqueous reducing agent solution is at least one of sodium chlorite, cuprous sulfide, potassium metabisulfite, sodium thiosulfate; when the star polymer fluid loss additive is prepared, the amount of the aqueous solution of the reducing agent added is 0.012 to 0.014% (for example, 0.012%, 0.013%, or 0.014%).

According to some preferred embodiments, in step (2), the mass concentration of the aqueous solution of the reducing agent is 0.8-1.1% (for example, may be 0.8%, 0.9%, 1.0% or 1.1%); the addition rate of the aqueous solution of the reducing agent is 3-5 mL/h (for example, 3mL/h, 3.5mL/h, 4mL/h, 4.5mL/h or 5 mL/h), and the addition time is 1.8-2 h (for example, 1.8h, 1.9h or 2 h).

In the preparation of the oil phase solution and the water-in-oil emulsion, the solution can be stirred for 15-20 min under the rotating speed condition of 1500-2000 r/min in order to ensure that the solution is more uniformly dispersed; in the invention, in addition to the preparation process of the oil phase solution and the water-in-oil emulsion, in the mixing process and the reaction process of other components, in order to ensure that the reaction is more complete and to avoid demulsification, the rotation speed can be properly regulated to prolong the stirring time, and the stirring can be carried out for 20-25 min at 250-300 r/min; for example, in the step (2), firstly, adding the aqueous phase solution into the oil phase solution at one time, and stirring at a high speed of 1500-2000 r/min for 15-20 min to ensure sufficient emulsification so as to obtain the water-in-oil emulsion; and then introducing nitrogen into the water-in-oil emulsion system to remove oxygen, reducing the stirring rotation speed to prevent demulsification, dropwise adding a reducing agent aqueous solution into the water-in-oil emulsion system at the rotation speed of 250-300 r/min, and keeping the temperature for 2-3 hours at the same temperature to ensure more complete reaction after the reaction is finished by controlling the adding time and the adding speed of the reducing agent aqueous solution.

According to some preferred embodiments, in step (3), the organic peroxygen initiator is at least one of tert-butyl peroxybenzoate, cumene peroxide or diisopropylbenzene peroxide; the acrylamide monomer is at least one of acrylamide, methacrylamide, N-isopropyl acrylamide, N-tertiary butyl acrylamide or N- (trityl) methacrylamide; the branching agent is at least one of 16-hydroxy hexadecanoic acid, butyl p-hydroxybenzoate, 4' -hydroxybutyrylaniline, 4-hydroxy-1-naphthalene sulfonic acid sodium salt or 11-hydroxy undecyl phosphoric acid; the branching agent adopted in the invention is a small molecular surfactant with hydroxyl at the chain end and long chain or benzene ring structure in the chain, the hydroxyl at the chain end can be subjected to a hydrogen bond substitution reaction with an amide group in an acrylamide monomer, and short chain small molecules containing long chain or benzene ring are grafted on the long chain of the amide group to form a hyperbranched structure, so that the shearing resistance and deformation resistance of the polymer can be improved, and the steric hindrance of the polymer is increased due to the existence of the long chain structure and the benzene ring structure, so that the temperature resistance and salt resistance and filtration loss resistance of the polymer are further improved.

According to some preferred embodiments, in step (3), in preparing the star polymer fluid loss additive, the following raw material components are added to the second product solution: 0.0085-0.0087% (for example, 0.0085%, 0.0086% or 0.0087%), 7-8% (for example, 7%, 7.2%, 7.5%, 7.8% or 8%), 2-3% (for example, 2%, 2.2%, 2.5%, 2.8% or 3%) of branching agent, 7-8% (for example, 7%, 7.2%, 7.5%, 7.8% or 8%) of water; in the invention, the branching agent can carry out substitution reaction with the acrylamide monomer, and a small molecular chain is grafted on an amide group to form a hyperbranched structure, so that the shearing resistance, the temperature resistance, the salt tolerance and the filtration reduction performance of the polymer are improved, if the addition amount of the branching agent is lower than the range, the hyperbranched structure is not formed, the shearing resistance, the temperature resistance, the salt tolerance and the filtration reduction performance of the polymer cannot be effectively enhanced, and if the addition amount of the branching agent is higher than the range, the solubility of the polymer is reduced.

According to some preferred embodiments, in step (4), the azo-based initiator is at least one of diisopropyl azodicarboxylate, dibenzyl azodicarboxylate, di-2-methoxyethyl azodicarboxylate or bis (4-chlorobenzyl) azodicarboxylate; the nucleating agent is at least one of diallyl disulfide, 1, 5-hexadiene, allyl disulfide, diallyl carbonate or diallyl amine; the temperature stabilizer is at least one of N-phenylthiourea, thiosemicarbazide, 4-methyl thiosemicarbazide or benzyl mercaptan; the phase inversion agent is at least one of trideceth (18) ether, polyethylene glycol (12) trideceth, hexaethylene glycol dodecyl ether or decaethylene glycol monoldodecyl ether.

According to some preferred embodiments, in step (4), when preparing the star polymer fluid loss additive, the addition amounts of the raw material components in step (4) are as follows: 0.012 to 0.013% (for example, 0.012% or 0.013%), 6 to 7% of an acrylamide monomer (for example, 6%, 6.2%, 6.5%, 6.8% or 7%), 0.5 to 0.7% of a nucleating agent (for example, 0.5%, 0.55%, 0.6%, 0.65% or 0.7%), 0.8 to 1.1% of a temperature stabilizer (for example, 0.8%, 0.9%, 1.0% or 1.1%), 5.6 to 15.6% of water (for example, 5.6%, 6%, 8%, 10%, 12%, 15% or 15.6%), 1.3 to 1.5% of a phase inversion agent (for example, 1.3%, 1.4% or 1.5%); in the present invention, the content of the nucleating agent is lower than the above range, which may adversely affect the nucleation process of the acrylamide monomer and thus be unfavorable for forming a star polymer structure, and if the content of the nucleating agent is higher than the above range, the acrylamide may form a macromolecular network structure, thereby causing the solubility of the star polymer to be deteriorated; according to the invention, the polymer product meeting the field requirement can be prepared by adjusting the addition proportion of the acrylamide monomer in the whole reaction and further adjusting the arm length and the arm number of the star polymer.

According to some preferred embodiments, in step (1), the method further comprises a step of adjusting the pH of the aqueous phase solution to 7.9-8.0 (e.g., 7.9, 7.95, or 8.0) with the alkaline substance; the pH of the aqueous solution in the present invention is preferably in the above range, so that the polymerization rate can be ensured to be in a proper range.

In the step (2), the temperature of the reaction is preferably 25-30 ℃ (for example, may be 25 ℃, 26 ℃, 27 ℃, 28 ℃, 29 ℃ or 30 ℃), the time of the reaction is preferably 1.8-2 hours (for example, may be 1.8 hours, 1.9 hours or 2 hours), and in order to ensure that the reaction is more complete, the reaction is preferably kept at 25-30 ℃ for 2-3 hours after the completion of the reaction; in the step (3), the temperature of the reaction is 35-40 ℃ (for example, the temperature can be 35 ℃, 36 ℃, 37 ℃, 38 ℃, 39 ℃ or 40 ℃), the time of the reaction is 2-2.5 hours (for example, the time can be 2 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours or 2.5 hours), and the reaction is continued to be kept at 35-40 ℃ for 3-4 hours after the completion of the reaction; in the step (4), the temperature of the reaction is 50-55 ℃ (for example, the temperature can be 50 ℃, 51 ℃, 52 ℃, 53 ℃, 54 ℃ or 55 ℃), the time of the reaction is 2-2.5 hours (for example, the time can be 2 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours or 2.5 hours), and the reaction is continued to be kept at the temperature of 50-55 ℃ for 3-4 hours after the completion of the reaction; according to the invention, different polymerization reactions are initiated at different temperature stages, and the reaction temperature of a reaction system is raised stepwise, so that the polymerization reaction is ensured to be more complete, the stability in the inverse emulsion polymerization process is improved, and the star-shaped polymer structure with uniform chain length of a molecular chain and narrow PDI (polymer product identifier) relative to a molecular mass distribution coefficient is ensured to be prepared; in the invention, after the reaction in the step (4) is completed, the temperature of the reaction system is changed to room temperature (20-25 ℃), a phase inversion agent is added into the reaction system and stirred for 20-25 min, and the addition of the phase inversion agent can further improve the dissolution rate of the star polymer filtrate reducer, so that the star polymer filtrate reducer is more convenient to use on site.

According to some preferred embodiments, the reaction is performed under nitrogen conditions, and the nitrogen flowing time is 30-35 min (for example, 30min, 31min, 32min, 33min, 34min or 35 min); in the method, oxygen is used as a polymerization inhibitor to adversely affect the polymerization reaction, so that the polymerization reaction is carried out under the nitrogen atmosphere, and meanwhile, in the step (3), in order to ensure that the polymerization reaction is more controllable, the polymerization reaction is prevented from being carried out in advance after the addition of an organic peroxy initiator, so that in the step (3), the organic peroxy initiator can be firstly added into a first product solution under the air atmosphere after the air is blown to remove nitrogen for 25-30 min, and then the nitrogen is introduced for 30-35 min, and then the aqueous solution containing the acrylamide monomer and the branching agent is continuously dropwise added for reaction; in the step (4), air is firstly blown to remove nitrogen for 25-30 min before the azo initiator is added, then nitrogen is introduced for 30-35 min, and then an aqueous solution containing an acrylamide monomer, a nucleating agent and a temperature stabilizer is dropwise added for reaction.

The invention also provides a star polymer fluid loss additive, which is prepared by the preparation method provided by the invention.

In order to more clearly illustrate the technical scheme and advantages of the invention, a star polymer filtrate reducer and a preparation method thereof are described in detail below through several examples.

Example 1:

(1) The preparation method of the acrylic acid-sulfonate aqueous solution comprises the following steps: adding 370g of acrylic monomer (2-ethyl acrylic acid), 157g of sulfonate monomer (2-acrylamide-2-methylpropanesulfonic acid) and 282g of deionized water into a reaction kettle, stirring for 20min at 270r/min, controlling the temperature of the system to be 13 ℃ in a water bath, adding 191g of alkaline substance (potassium hydroxide) into the system for neutralization reaction, and using a pH meter to test the pH value of the system to be 7.03 to obtain an acrylate-sulfonate aqueous solution (2-ethyl potassium acrylate-2-acrylamide-2-methylpropanesulfonate aqueous solution);

aqueous phase solution: 23g of a trithio chain transfer agent (2-cyano-2-propyldodecyl trithiocarbonate), 36g of a water-soluble emulsifier (polyoxyethylene mountain plow anhydride tristearate), 8.4g of an inorganic salt aqueous phase stabilizer (ammonium sulfate), 0.087g of an inorganic peroxy initiator (potassium persulfate), 0.068g of a metal complexing agent (diethylenetriamine pentamethylene phosphonic acid), 0.1g of a molecular weight regulator (sodium succinate) and 285g of an acrylate-sulfonate aqueous solution are stirred and mixed uniformly at 270r/min to obtain an aqueous phase solution, and the pH of the aqueous phase solution is adjusted to 7.96 by using 3.5g of an alkaline substance (potassium hydroxide);

Oil phase solution: adding 235g of oil (white oil) and 36g of oil-soluble emulsifier (sorbitan trioleate) into a reaction kettle, stirring for 18min at 1800r/min, mixing uniformly to obtain an oil phase solution, and controlling the system temperature at 22 ℃ through a water bath;

(2) Adding the aqueous phase solution into the oil phase solution at one time, and stirring and emulsifying for 18min at 1800r/min to obtain water-in-oil emulsion; introducing nitrogen into the emulsion for 32min, controlling the temperature of the system to 27 ℃, dropwise adding a 1% mass concentration aqueous solution of a reducing agent (potassium metabisulfite) into the water-in-oil emulsion at a speed of 3mL/h under the condition of stirring at a speed of 270r/min, and keeping the temperature at 27 ℃ for 2.4h after the reaction to obtain a first product solution;

(3) Introducing air into the first product solution for 27min, firstly adding 0.086g of organic peroxy initiator (tert-butyl peroxybenzoate), introducing nitrogen for 32min, raising the temperature of the system to 38 ℃, and dropwise adding 73g of acrylamide monomer (N-isopropyl acrylamide), 23g of branching agent (16-hydroxy hexadecyl carbonic acid) and 75g of deionized water into the first product solution at a speed of 3mL/h within 2.3h at a rotating speed of 270r/min, and keeping the temperature at 38 ℃ for 3.4h after the reaction to obtain a second product solution;

(4) Air was introduced into the second product solution for 27 minutes, 0.125g of an azo initiator (dibenzyl azodicarbonate) was first added, nitrogen was introduced for 32 minutes, the system temperature was raised to 52℃and an aqueous solution prepared beforehand of 63g of an acrylamide monomer (N-isopropylacrylamide), 5.3g of a nucleating agent (allyldisulfide), 8.6g of a temperature stabilizer (4-methylaminothiourea) and 125.2g of deionized water was added dropwise to the second product solution at a rate of 3mL/h over 2.3 hours, the reaction was continued at 52℃for 3.4 hours, the system temperature was then brought to room temperature (23 ℃) and 14g of a phase inversion agent (trideceth (18) ether) was added thereto and stirred at 270r/min for 23 minutes, to obtain a star polymer filtrate reducer.

Example 2:

(1) The preparation method of the acrylic acid-sulfonate aqueous solution comprises the following steps: adding 355g of acrylic monomer (2-ethyl acrylic acid), 168g of sulfonate monomer (7-amino-4-hydroxy-2-naphthalene sulfonic acid) and 297g of deionized water into a reaction kettle, stirring and mixing uniformly at 270r/min, controlling the temperature of the system to be 13 ℃ in a water bath, adding 180g of alkaline substance (potassium hydroxide) into the system for neutralization reaction, and using a pH meter to test the pH value of the system to be 7.0 to obtain an acrylate-sulfonate aqueous solution (2-ethyl potassium acrylate-7-amino-4-hydroxy-2-naphthalene sulfonate aqueous solution);

Aqueous phase solution: 25g of a trithio chain transfer agent (2- (dodecyl trithiocarbonate group) -2-methylpropanoic acid), 30g of a water-soluble emulsifier (polyoxyethylene mountain plow anhydride tristearate), 8g of an inorganic salt aqueous phase stabilizer (ammonium sulfate), 0.086g of an inorganic peroxy initiator (lithium peroxide), 0.071g of a metal complexing agent (diethylenetriamine pentamethylene phosphonic acid), 0.095g of a molecular weight regulator (sodium succinate) and 290g of an acrylate-sulfonate aqueous solution were stirred at 270r/min for 20min to be mixed uniformly to obtain an aqueous phase solution, and the pH of the aqueous phase solution was adjusted to 8.0 by using 5g of an alkaline substance (potassium hydroxide);

oil phase solution: adding 240g of oil (white oil) and 30g of oil-soluble emulsifier (sorbitan monolaurate) into a reaction kettle, stirring for 20min at 1950r/min, mixing to obtain an oil phase solution, and controlling the system temperature at 22 ℃ through a water bath;

(2) Adding the aqueous phase solution into the oil phase solution at one time, and stirring and emulsifying for 20min at 1950r/min to obtain water-in-oil emulsion; introducing nitrogen into the emulsion for 30min, controlling the temperature of the system to 27 ℃, dropwise adding a reducing agent aqueous solution (potassium metabisulfite) with the mass concentration of 0.9% into the water-in-oil emulsion at the speed of 4mL/h under the stirring speed of 270r/min, and keeping the temperature at 27 ℃ for 2.4h after the reaction to obtain a first product solution;

(3) Introducing air into the first product solution for 30min, firstly adding 0.085g of organic peroxy initiator (tert-butyl peroxybenzoate), introducing nitrogen for 32min, raising the temperature of the system to 38 ℃, and dropwise adding an aqueous solution prepared in advance from 70g of acrylamide monomer (N-isopropyl acrylamide), 28g of branching agent (16-hydroxy hexadecyl carbonic acid) and 70g of deionized water into the first product solution at a speed of 3mL/h within 2.3h, and keeping the temperature at 38 ℃ for 3.4h after the reaction to obtain a second product solution;

(4) Air is introduced into the second product solution for 30min, 0.13g of azo initiator (di-2-methoxyethyl azo-diformate) is firstly added, nitrogen is introduced for 30min, the temperature of the system is increased to 52 ℃, 60g of acrylamide monomer (N-isopropyl acrylamide), 5g of nucleating agent (diallyl carbonate), 8g of temperature stabilizer (4-methyl thiosemicarbazide) and 118g of deionized water are added into the second product solution dropwise at a speed of 3mL/h within 2.3h, the temperature is kept at 52 ℃ for 3.4h after the reaction, then the temperature of the system is increased to room temperature (23 ℃) and 13g of phase inversion agent (dodecyl glycol) is added into the system, and the mixture is stirred for 23min at 270r/min, thus obtaining the star polymer filtrate reducer.

Example 3:

(1) The preparation method of the acrylic acid-sulfonate aqueous solution comprises the following steps: adding 380g of acrylic monomer (acrylic acid), 150g of sulfonate monomer (2-acrylamide-2-methylpropanesulfonic acid) and 270g of deionized water into a reaction kettle, stirring for 20min at 270r/min, controlling the temperature of the system to be 10 ℃ in a water bath, adding 200g of alkaline substance (potassium hydroxide) into the system for neutralization reaction, and using a pH meter to test the pH value of the system to be 7.03 to obtain an acrylate-sulfonate aqueous solution (2-potassium ethylacrylate-2-acrylamide-2-methylpropanesulfonate aqueous solution);

aqueous phase solution: 20g of a trithio chain transfer agent (cyanomethyl dodecyl trithiocarbonate), 39g of a water-soluble emulsifier (polyoxyethylene sorbitan monooleate), 11g of an inorganic salt aqueous phase stabilizer (ammonium sulfate), 0.089g of an inorganic peroxy initiator (zinc peroxide), 0.065g of a metal complexing agent (nitrilotriacetic acid), 0.11g of a molecular weight regulator (sodium propionate) and 280g of an acrylic acid-sulfonate aqueous solution are stirred at 270r/min for 20min and mixed uniformly to obtain an aqueous phase solution, and 3g of an alkaline substance (potassium hydroxide) is used for regulating the pH of the aqueous phase solution to 7.96;

oil phase solution: adding 230g of oil (white oil) and 40g of oil-soluble emulsifier (sorbitan trioleate) into a reaction kettle, stirring for 18min at 1800r/min, mixing uniformly to obtain an oil phase solution, and controlling the system temperature at 25 ℃ through a water bath;

(2) Adding the aqueous phase solution into the oil phase solution at one time, and stirring and emulsifying for 18min at 1800r/min to obtain water-in-oil emulsion; introducing nitrogen into the emulsion for 32min, controlling the temperature of the system to be 30 ℃, dropwise adding a 1% mass concentration reducer aqueous solution (potassium metabisulfite) into the water-in-oil emulsion at a speed of 3mL/h under the condition of stirring at a speed of 270r/min, and keeping the temperature at 30 ℃ for 2h after the reaction to obtain a first product solution;

(3) Introducing air into the first product solution for 27min, firstly adding 0.087g of organic peroxy initiator (cumene peroxide), introducing nitrogen for 32min, raising the temperature of the system to 35 ℃, and dropwise adding 79g of acrylamide monomer (N-isopropyl acrylamide), 20g of branching agent (4' -hydroxybutyrylaniline) and 78g of deionized water into the first product solution at a speed of 3mL/h within 2.1h at a rotating speed of 270r/min, and keeping the temperature at 35 ℃ for 4h after the reaction to obtain a second product solution;

(4) Air was introduced into the second product solution for 27 minutes, 0.12g of an azo initiator (dibenzyl azodicarbonate) was first added, nitrogen was introduced for 32 minutes, the system temperature was raised to 50℃and an aqueous solution prepared beforehand of 68g of an acrylamide monomer (N-isopropylacrylamide), 6.5g of a nucleating agent (diallyl carbonate), 9g of a temperature stabilizer (benzylmercaptan) and 101.5g of deionized water was added dropwise to the second product solution at a rate of 3mL/h over 2.1 hours, the reaction was continued to be kept at 50℃for 4 hours, the system temperature was then raised to room temperature (20 ℃) and 15g of a phase inversion agent (dodecylglycol monolauryl ether) was added thereto, and stirring was carried out at 270r/min for 23 minutes, to obtain a star polymer filtrate reducer.

Example 4:

example 4 is substantially the same as example 1 except that: in the step (1), the addition amount of trithio chain transfer (2-cyano-2-propyldodecyl trithiocarbonate) was 28g.

Example 5:

example 5 is substantially the same as example 1 except that: in the step (1), the addition amount of trithio chain transfer (2-cyano-2-propyldodecyl trithiocarbonate) was 19g.

Example 6:

example 6 is substantially the same as example 1 except that: in the step (1), the amount of the aqueous solution of acrylic acid salt-sulfonic acid salt was 270g.

Example 7:

example 7 is substantially the same as example 1 except that: in the step (1), the amount of the aqueous solution of acrylic acid salt-sulfonic acid salt was 300g.

Example 8:

example 8 is substantially the same as example 1 except that: in step (3), the amount of the branching agent (16-hydroxyhexadecanoic acid) added was 18g.

Example 9:

example 9 is substantially the same as example 1 except that: in step (3), the amount of the branching agent (16-hydroxyhexadecanoic acid) added was 32g.

In the embodiment, the branching agent is excessively added, and each molecular chain in the system is physically crosslinked to form a space network, so that the solubility of the final polymer is poor, and the filtration reducing performance is reduced.

Example 10:

example 10 is substantially the same as example 1 except that: in step (4), the addition amount of the nucleating agent (allyl disulfide) was 4.8g.

Example 11:

example 11 is substantially the same as example 1 except that: in step (3), the addition amount of the nucleating agent (allyl disulfide) was 7.2g.

In this example, the nucleating agent was added too much, the final system was insoluble in water, and the subsequent index could not be tested.

Comparative example 1:

comparative example 1 is substantially the same as example 1 except that: in step (1), no trithio chain transfer agent (2-cyano-2-propyldodecyl trithiocarbonate) was added to the aqueous solution.

Comparative example 2:

comparative example 2 is substantially the same as example 1 except that: in step (3), no branching agent (16-hydroxyhexadecanoic acid) is added.

Comparative example 3:

comparative example 3 is substantially the same as example 1 except that: in step (4), no nucleating agent (allyl disulfide) is added.

Comparative example 4:

comparative example 4 is substantially the same as example 1 except that: in the step (4), an inorganic salt aqueous phase stabilizer (ammonium sulfate) is not added; without adding the aqueous phase stabilizer, demulsification occurs in the polymerization reaction process, and the performance cannot be tested.

Comparative example 5:

comparative example 5 is substantially the same as example 1 except that: removing the step (3) and the step (4), and directly mixing the aqueous solution containing the acrylamide monomer and the branching agent in the step (3) and the aqueous solution containing the acrylamide monomer, the nucleating agent and the temperature stabilizer in the step (4) with the components in the step (1) to obtain an aqueous phase solution; namely, when preparing the aqueous phase solution in the step (1): 25g of a trithio chain transfer agent (2- (dodecyl trithiocarbonate group) -2-methylpropanoic acid), 30g of a water-soluble emulsifier (polyoxyethylene mountain plow anhydride tristearate), 8g of an inorganic salt aqueous phase stabilizer (ammonium sulfate), 130g of an acrylamide monomer (N-isopropyl acrylamide), 28g of a branching agent (16-hydroxy hexadecyl carbonic acid), 5g of a nucleating agent (diallyl carbonate), 0.086g of an inorganic peroxy initiator (tert-butyl hydroperoxide), 0.071g of a metal complexing agent (diethylenetriamine penta-methylene phosphonic acid), 0.095g of a molecular weight regulator (sodium succinate) and 290g of an acrylate-sulfonate aqueous solution are stirred and mixed uniformly at 270r/min to obtain an aqueous phase solution, and the pH of the aqueous phase solution is adjusted to 8.0 by using 5g of an alkaline substance (potassium hydroxide);

(2) Adding the aqueous phase solution into the oil phase solution at one time, and stirring and emulsifying for 20min at 1950r/min to obtain water-in-oil emulsion; introducing nitrogen into the emulsion for 30min, controlling the temperature of the system to 27 ℃, dropwise adding a reducing agent aqueous solution (potassium metabisulfite) with the mass concentration of 0.9% into the water-in-oil emulsion at the stirring speed of 270r/min for 1.9h at the speed of 4mL/h, keeping the temperature at 27 ℃ for 2.4h after the reaction, then, cooling the system to room temperature (23 ℃), adding 13g of a phase inversion agent (dodecyl glycol) into the system, and stirring the mixture at 270r/min for 23min to obtain the polymer filtrate reducer.

Comparative example 6:

comparative example 6 is substantially the same as example 1 except that: in step (3), the branching agent is 1-phenylundecane.

The branching agent in the comparative example does not have branching effect, so that the arms of the star polymer have no branching chains, and the filtrate reducing performance of the final polymer filtrate reducer is reduced.

Comparative example 7:

comparative example 7 is substantially the same as example 1 except that: in step (4), the nucleating agent is cyclodextrin.

In this example, the nucleating agent is replaced with cyclodextrin, resulting in too strong a subsequent crosslinking effect, the final product being insoluble and failing to test the subsequent index.

Comparative example 8:

comparative example 8 is substantially the same as example 1 except that: in the step (1), the aqueous solution is not added with the aqueous solution of the acrylate-sulfonate, the step (3) is removed, and the aqueous solution containing the acrylic monomer and the branching agent in the step (3) is directly added into the step (1) to obtain an aqueous solution; namely: in the preparation of the aqueous phase solution in step (1): 23g of a trithio chain transfer agent (2-cyano-2-propyldodecyl trithiocarbonate), 36g of a water-soluble emulsifier (polyoxyethylene mountain plow anhydride tristearate), 8.4g of an inorganic salt aqueous phase stabilizer (ammonium sulfate), 0.087g of an inorganic peroxy initiator (potassium persulfate), 0.068g of a metal complexing agent (diethylenetriamine pentamethylene phosphonic acid), 0.1g of a molecular weight regulator (sodium succinate) and 73g of an acrylamide monomer (N-isopropylacrylamide), 23g of a branching agent (16-hydroxy hexadecyl carbonic acid) and 285g of deionized water are stirred at 270r/min for 20min to obtain an aqueous phase solution, and the pH of the aqueous phase solution is adjusted to 7.96 by using 3.5g of an alkaline substance (potassium hydroxide);

(2) Adding the aqueous phase solution into the oil phase solution at one time, and stirring and emulsifying for 18min at 1800r/min to obtain water-in-oil emulsion; introducing nitrogen into the emulsion for 32min, controlling the temperature of the system to 27 ℃, dropwise adding a 1% mass concentration aqueous solution of a reducing agent (potassium metabisulfite) into the water-in-oil emulsion at a speed of 3mL/h under the condition of stirring at a speed of 270r/min, and keeping the temperature at 27 ℃ for 2.4h after the reaction to obtain a first product solution;

(3) Air was introduced into the second product solution for 27 minutes, 0.125g of an azo initiator (dibenzyl azodicarbonate) was first added, nitrogen was introduced for 32 minutes, the system temperature was raised to 52℃and an aqueous solution prepared beforehand of 63g of an acrylamide monomer (N-isopropylacrylamide), 5.3g of a nucleating agent (allyldisulfide), 8.6g of a temperature stabilizer (4-methylaminothiourea) and 125.2g of deionized water was added dropwise to the second product solution at a rate of 3mL/h over 2.3 hours, the reaction was continued at 52℃for 3.4 hours, the system temperature was then brought to room temperature (23 ℃) and 14g of a phase inversion agent (trideceth (18) ether) was added thereto and stirred at 270r/min for 23 minutes, to obtain a polymer filtrate reducer.

Comparative example 9:

(1) Aqueous phase solution: 108.8g of acrylamide, 23g of 3-benzylmercapto thiocarbonate sulfur-propionic acid, 36g of water-soluble emulsifier (sorbitan monooleate polyoxyethylene ether) and 403g of deionized water are stirred for 20min at 270r/min and uniformly mixed to obtain a water phase solution;

oil phase solution: adding 235g of white oil, 10g of a high molecular emulsifier (Hypermer B246SF, uniqema company) and 26g of an oil-soluble emulsifier (span-80) into a reaction kettle, stirring for 18min at 1800r/min, uniformly mixing to obtain an oil phase solution, and controlling the temperature of the system at 22 ℃ through a water bath;

(2) Adding the aqueous phase solution into the oil phase solution at one time, and stirring and emulsifying for 18min at 1800r/min to obtain water-in-oil emulsion; introducing nitrogen to remove oxygen for 30min, heating to 45 ℃ at 500r/min, dissolving 0.12g of azo diiso Ding Mi hydrochloride in water, adding into a reaction kettle to initiate polymerization, and reacting for 4h; obtaining a first product solution;

(3) Dissolving 27.2g of acrylamide and 5.3g of N' N-methylenebisacrylic acid amine in 111.7g of deionized water, dropwise adding the solution into a polymerization system at a constant speed within 45 minutes, and stopping the reaction after continuing to react for 2.5 hours to obtain a second product solution;

(4) The system was then warmed to room temperature (23 ℃) and 14g of a phase inversion agent (trideceth (18) ether) was added thereto, followed by stirring at 270r/min for 23min, to obtain a polymer filtrate reducer.

The star polymer fluid loss additives obtained in examples 1 to 11 and comparative examples 1 to 9 were subjected to performance tests, respectively, with the following test results:

(1) Testing of viscosity versus molecular mass: testing the viscosity-average molecular weight of the filtrate reducer according to GB/T17514-2017 standard;

(2) Relative molecular mass distribution coefficient PDI test: reference standard GB/T16631-2008 general rules for high performance liquid chromatography; the specific detection method is as follows:

The test conditions were: using Polymer Laboratory PL-GPC 50 gel permeation chromatograph, using PL-aquagel-60, PL-aquagel-40 and PL-aquagel-30 three columns connected in series, with 0.2mol/L mobile phase NaNO ₃ (containing 0.02% w/v NaN) ₃ ) The flow rate is 1mL/min, the temperature of a column incubator is 40 ℃, and the detection period is 15min; PEO with narrow distribution was used as standard (pdi=1.06);

weighing 0.1g of the filtrate reducer samples in the examples and the comparative examples, fixing the volume to a 100mL volumetric flask by using a mobile phase to prepare a sample solution with the volume of about 1g/L, filtering by using a needle filter membrane with the filter pore diameter of 0.2 mu m, and measuring the relative molecular mass distribution coefficient by using a machine;

(3) Testing the filtration loss and the vector reduction rate of the composite brine-based slurry:

preparing composite brine-based slurry: 400mL of distilled water is measured and placed in a cup, 18.0g of sodium chloride, 2.0g of anhydrous calcium chloride and 5.2g of magnesium chloride are added, and 60.0g of sodium bentonite meeting SY/T5490-2016 standard and 3.6g of anhydrous sodium carbonate are added after the distilled water is dissolved; stirring at high speed (11000 r/min) for 20min, stopping at least twice, scraping clay adhered to the container wall, and curing in a sealed container at 25+ -3deg.C for 24h to obtain composite salt water-based slurry;

Base slurry fluid loss measurement: stirring the cured composite brine-based slurry at a high speed for 20min, putting the slurry into a furnace with a set temperature of 220 ℃ for ageing for 16h, cooling to room temperature (25 ℃), stirring at a high speed (11000 r/min) for 5min, measuring the filtration loss according to GB/T16783.1, wherein the filtration loss is 80-110 mL, otherwise, adjusting the addition amount of sodium bentonite;

fluid loss measurement after high temperature aging: adding 12.0g of filtrate reducer sample into the composite brine slurry, stirring at high speed (11000 r/min) for 20min, aging in a furnace with a set temperature of 220 ℃ for 16h, cooling to room temperature (25 ℃), stirring at high speed for 5min, and measuring the filtrate reducer therein according to GB/T16783.1;

the reduction rate of the filtration loss of the composite brine-based slurry is measured according to the formula (1):

（1）

wherein:

f, reducing the filtration loss rate of the composite brine-based slurry,%;

F ₀ -fluid loss of the base stock in milliliters (mL);

F ₁ the fluid loss of the slurry is measured in milliliters (mL).

TABLE 1

Note that: in the table "/" indicates that the performance was not tested

As shown in Table 1, the viscosity-average molecular weight of the star polymer filtrate reducer prepared in the embodiment of the invention is 180-230 ten thousand, the viscosity-average molecular weight is smaller, the relative molecular weight distribution coefficient is narrower, PDI is less than or equal to 1.3, the filtrate loss of the composite brine-based slurry after the filtrate reducer treatment is less than or equal to 15mL at the temperature of 220 ℃, and the filtrate loss reduction rate of the composite brine-based slurry is more than or equal to 85%, so that the filtrate reducer prepared by the invention has the advantages of both hyperbranched structure and star structure, not only has excellent filtrate loss performance, but also has the advantages of narrow molecular weight distribution coefficient, low molecular weight, low solution viscosity, concentrated charge, quick dissolution, temperature resistance, salt resistance, shearing resistance, convenient application and the like.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. The preparation method of the star-shaped polymer filtrate reducer is characterized by comprising the following steps of:

(1) Uniformly mixing a trithio chain transfer agent, a water-soluble emulsifier, an inorganic salt water phase stabilizer, an inorganic peroxy initiator, a metal complexing agent, a molecular weight regulator and an acrylic acid-sulfonate aqueous solution to obtain a water phase solution; mixing oil and oil-soluble emulsifier to obtain oil phase solution;

the acrylic acid-sulfonate aqueous solution is prepared from acrylic acid monomers, sulfonate monomers and alkaline substances through a neutralization reaction;

the sulfonate monomer is at least one of vinyl sulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid or [2- (methacryloyloxy) ethyl ] dimethyl- (3-sulfopropyl) ammonium hydroxide;

When the star polymer filtrate reducer is prepared, the addition amounts of the raw material components in the aqueous phase solution are as follows: 2-2.5% of trithio chain transfer agent, 3-4% of water-soluble emulsifier, 0.8-1.1% of inorganic salt water phase stabilizer, 0.0086-0.0089% of inorganic peroxy initiator, 0.0065-0.0071% of metal complexing agent, 0.0095-0.011% of molecular weight regulator and 28-29% of acrylic acid-sulfonate aqueous solution;

(2) Adding the aqueous phase solution into the oil phase solution, emulsifying to obtain water-in-oil emulsion, adding a reducing agent aqueous solution into the water-in-oil emulsion, and reacting to obtain a first product solution;

(3) Sequentially adding an organic peroxy initiator and an aqueous solution containing an acrylamide monomer and a branching agent into the first product solution, and reacting to obtain a second product solution;

the branching agent is at least one of 16-hydroxy hexadecanoic acid, butyl p-hydroxybenzoate, 4' -hydroxybutyrylaniline, 4-hydroxy-1-naphthalene sulfonic acid sodium salt or 11-hydroxy undecyl phosphoric acid;

when the star polymer filtrate reducer is prepared, the addition amounts of the raw material components in the second product solution are as follows: 0.0085-0.0087% of organic peroxide initiator, 7-8% of acrylamide monomer, 2-3% of branching agent and 7-8% of water;

(4) Sequentially adding an azo initiator and an aqueous solution containing an acrylamide monomer, a nucleating agent and a temperature stabilizer into the second product solution, adding a phase inversion agent after reaction, and uniformly mixing to obtain the star polymer filtrate reducer;

the nucleating agent is at least one of diallyl disulfide, 1, 5-hexadiene, allyl disulfide, diallyl carbonate or diallyl amine;

the temperature stabilizer is at least one of N-phenylthiourea, thiosemicarbazide, 4-methyl thiosemicarbazide or benzyl mercaptan;

when the star polymer filtrate reducer is prepared, the addition amount of each raw material component in the step (4) is as follows: 0.012-0.013% of azo initiator, 6-7% of acrylamide monomer, 0.5-0.7% of nucleating agent, 0.8-1.1% of temperature stabilizer, 5.6-15.6% of water and 1.3-1.5% of phase inversion agent.

2. The method of claim 1, wherein in step (1):

the preparation method of the acrylic acid-sulfonate aqueous solution comprises the following steps: uniformly mixing an acrylic monomer, a sulfonate monomer and water, adding an alkaline substance for neutralization reaction, and obtaining an acrylic acid-sulfonate aqueous solution after the neutralization reaction;

when the acrylic acid-sulfonate aqueous solution is prepared, the addition amounts of the raw material components are as follows: 35-38% of acrylic acid monomer, 15-17% of sulfonate monomer, 18-20% of alkaline substance and 25-32% of water; and/or

The temperature of the neutralization reaction is 10-15 ℃.

3. The preparation method according to claim 1 or 2, wherein in step (1):

the acrylic monomer is at least one of acrylic acid, methacrylic acid, 2-bromoacrylic acid, 2-furan acrylic acid, 2-propyl acrylic acid or 2-ethyl acrylic acid;

the alkaline substance is at least one of sodium hydroxide, potassium hydroxide or ammonia water.

4. The method of claim 1, wherein in step (1):

the trithio chain transfer agent is at least one of dimethyl trithiocarbonate, bis (carboxymethyl) trithiocarbonate, cyanomethyl dodecyl trithiocarbonate, S-dibenzyl trithiocarbonate, 2-cyano-2-propyl dodecyl trithiocarbonate or 2- (dodecyl trithiocarbonate group) -2-methylpropanoic acid;

the water-soluble emulsifier is at least one of polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate or polyoxyethylene sorbitan monooleate;

the inorganic salt water phase stabilizer is at least one of ammonium sulfate, sodium acetate and ammonium chloride;

The inorganic peroxy initiator is at least one of lithium peroxide, potassium persulfate or zinc peroxide;

the metal complexing agent is at least one of diethylenetriamine pentamethylene phosphonic acid, ethylenediamine tetraacetic acid or nitrilotriacetic acid;

the molecular weight regulator is at least one of sodium propionate, sodium succinate or sodium salicylate;

the oil is at least one of white oil, kerosene or rapeseed oil; and/or

The oil-soluble emulsifier is at least one of sorbitan monopalmitate, sorbitan monolaurate, sorbitan oleate or sorbitan oleate triester.

5. The method of claim 1, wherein in step (1):

when the star polymer filtrate reducer is prepared, the addition amounts of the raw material components in the oil phase solution are as follows: 23-24% of oil and 3-4% of oil-soluble emulsifier.

6. The method of claim 1, wherein in step (2):

the reducing agent in the reducing agent aqueous solution is at least one of sodium chlorite, cuprous sulfide, potassium metabisulfite and sodium thiosulfate;

when the star polymer filtrate reducer is prepared, the addition amount of the aqueous solution of the reducer is 0.012-0.014%; and/or

The mass concentration of the reducer aqueous solution is 0.8-1.1%; the adding speed of the aqueous solution of the reducing agent is 3-5 mL/h, and the adding time is 1.8-2 h.

7. The method of claim 1, wherein in step (3):

the organic peroxy initiator is at least one of tert-butyl peroxybenzoate, cumene peroxide or diisopropylbenzene peroxide;

the acrylamide monomer is at least one of acrylamide, methacrylamide, N-isopropyl acrylamide, N-tertiary butyl acrylamide or N- (trityl) methacrylamide.

8. The method of claim 1, wherein in step (4):

the azo initiator is at least one of diisopropyl azodicarboxylate, dibenzyl azodicarboxylate, di-2-methoxyethyl azodicarboxylate or bis (4-chlorobenzyl) azodicarboxylate;

the phase inversion agent is at least one of trideceth (18) ether, polyethylene glycol (12) trideceth, hexaethylene glycol dodecyl ether or decaethylene glycol monoldodecyl ether.

9. The method of manufacturing according to claim 1, characterized in that:

in the step (1), the method further comprises the step of adjusting the pH of the aqueous phase solution to 7.9-8.0 by adopting the alkaline substance;

In the step (2), the reaction temperature is 25-30 ℃, and the reaction time is 1.8-2 h;

in the step (3), the reaction temperature is 35-40 ℃, and the reaction time is 2-2.5 h;

in the step (4), the reaction temperature is 50-55 ℃, and the reaction time is 2-2.5 h; and/or

The reaction is carried out under the condition of nitrogen, and the nitrogen introducing time is 30-35 min.

10. A star polymer fluid loss additive prepared by the method of any one of claims 1 to 9.