CN112877045A

CN112877045A - Bulk-swelling efficient slug gel plugging agent and preparation method thereof

Info

Publication number: CN112877045A
Application number: CN202110037150.XA
Authority: CN
Inventors: 吕开河; 王晨烨; 白英睿; 孙金声; 郝惠军; 王金堂; 刘凡; 金家锋; 张洁; 刘敬平; 黄贤斌
Original assignee: China University of Petroleum East China
Current assignee: China University of Petroleum East China
Priority date: 2021-01-12
Filing date: 2021-01-12
Publication date: 2021-06-01
Anticipated expiration: 2041-01-12
Also published as: CN112877045B

Abstract

The invention provides a bulk-swelling type high-efficiency slug gel plugging agent and a preparation method thereof. The bulk-swelling type high-efficiency slug gel plugging agent is prepared from the following raw materials in parts by mass: 10-35 parts of polymerization reaction agent, 1-3 parts of cross-linking agent a, 0.02-0.5 part of proper temperature initiator, 0.5-5 parts of water-soluble resin toughening agent, 0.5-5 parts of composite inorganic toughening agent, 2-8 parts of modified starch, 2-10 parts of volume expansion reaction agent and 2-8 parts of rheological regulator; the volume expansion reactant is prepared from the following raw materials by an inverse emulsion polymerization method: water-soluble polymerization monomer, dispersion medium, emulsifier, oil phase initiator and cross-linking agent b. The plugging agent disclosed by the invention has the advantages of underground crosslinking gelling, flexible and adjustable gelling time, strong pressure-bearing capacity after gelling, higher water-swelling property, excellent mechanical strength after water absorption and the like.

Description

Bulk-swelling efficient slug gel plugging agent and preparation method thereof

Technical Field

The invention relates to a swelling type high-efficiency slug gel plugging agent and a preparation method thereof, belonging to the drilling fluid plugging technology in the field of petroleum exploration and development.

Background

The lost circulation is defined as a complex condition in a well in which working fluid (such as drilling fluid, cement slurry, completion fluid or other fluids) in a wellbore flows into a formation in a large amount (including percolating and filtering fluid is not included) under the action of pressure difference during various underground engineering operations such as drilling, cementing, testing or repairing, and is one of the most common technical problems in oil drilling engineering. In lost circulation, the proportion of fissured, karst cave losses is high, and these types of losses are very likely to occur when the drill encounters a fracture zone and unconformity of the formation. If the formation is not so micro-porous as to produce lost circulation, lost circulation accidents may also occur due to improper measures such as increasing the wellbore pressure above the formation fracture pressure.

However, if the corresponding effective measures can be effectively taken in time when the drilling encounters a leakage layer, the leakage degree can be greatly reduced. For a long time, various plugging materials are screened and summarized by research workers in various countries in practice aiming at the problem of drilling fluid loss under different conditions, and the plugging materials frequently used on site at present generally comprise bridging plugging materials, temporary plugging materials, high-water-loss plugging materials, inorganic gel plugging materials and the like. However, the common defects of the materials commonly used at present are as follows: firstly, the self-deformation capability of the plugging materials in the plugging process is poor or the plugging materials basically do not have the deformation capability, if the used plugging materials are slightly larger than the size of the pore cracks of the leak layer or are not matched with the shape of the pore cracks of the leak layer, the plugging materials are difficult to penetrate into the leak layer and only can form accumulation on the surface of the leak layer; and secondly, the common plugging material has poor water-absorbing expansion capacity or no water-absorbing expansion property, and is difficult to stably stay in a leaking layer under the action of external force. Due to the reasons, when the plugging material is used for treating lost circulation, poor plugging effect or repeated loss after successful plugging is easily caused.

The underground cross-linked gel plugging agent can pump a gel solution into a leaking layer at a certain speed by using a pump and a pipe sleeve, the temperature is gradually increased along with the depth of a stratum, a cross-linking reaction of a gel sol is started to generate solidification, and finally a slug gel suitable for a fracture form is formed. Chinese patent document CN106010485A discloses a self-cementing plugging agent and a plugging method, wherein the self-cementing plugging agent comprises the following components in percentage by mass: 25-35% of acrylamide monomer, 0.1-0.5% of cross-linking agent, 0.2-0.5% of sodium carbonate, 20-25% of bentonite, 2-5% of high-molecular polymer, 3-5% of pre-crosslinked gel particles, 30-35% of fine calcium carbonate, 5-8% of fiber and 0.1-0.5% of initiator, and the raw materials are uniformly mixed to obtain the self-cementing plugging agent; the plugging agent utilizes the formation temperature to generate polymerization reaction among molecules to form a rubber plug with certain water absorption expansion performance and compressive strength, thereby plugging a leakage layer. But the temperature application range of the plugging agent is narrow, and the temperature condition and the time range of the self-cementation of the plugging agent are not determined; the gel formed at the formation temperature has poor water-absorbing expansion performance, and the gel plugging agent after gelling has weak elastic toughness and lower pressure-bearing plugging strength.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a bulk-swelling efficient slug gel plugging agent and a preparation method thereof. The components of the plugging agent comprise a swelling reaction agent synthesized by a reverse emulsion polymerization method, and the obtained plugging agent has the advantages of underground crosslinking gelling, flexible and adjustable gelling time, strong pressure bearing capacity after gelling, higher water absorption swelling property, excellent mechanical strength after water absorption and the like.

The technical scheme of the invention is as follows:

the bulk-swelling type efficient slug gel plugging agent is prepared from the following raw materials in parts by mass: 10-35 parts of polymerization reaction agent, 1-3 parts of cross-linking agent a, 0.02-0.5 part of proper temperature initiator, 0.5-5 parts of water-soluble resin toughening agent, 0.5-5 parts of composite inorganic toughening agent, 2-8 parts of modified starch, 2-10 parts of volume expansion reaction agent and 2-8 parts of rheological regulator; the volume expansion reactant is prepared from the following raw materials by an inverse emulsion polymerization method: water-soluble polymerization monomer, dispersion medium, emulsifier, oil phase initiator and cross-linking agent b.

According to the preferable selection of the invention, the bulk-swelling type high-efficiency slug gel plugging agent is prepared from the following raw materials in parts by mass: 25-30 parts of polymerization reaction agent, 1-3 parts of cross-linking agent a, 0.08-0.1 part of proper temperature initiator, 3-5 parts of water-soluble resin toughening agent, 3-5 parts of composite inorganic toughening agent, 4-8 parts of modified starch, 2-6 parts of volume expansion reaction agent and 2-6 parts of rheological control agent.

According to the invention, the polymerization reactant is preferably a combination of three or more of N, N' -methylenebisacrylamide, 2 (methylamino) ethyl methacrylate, N-dimethylbisacrylamide, partially hydrolyzed polyacrylamide, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, itaconic acid, methyl methacrylate, hydroxypropyl acrylate or hydroxyethyl methacrylate. Preferably, the polymerization reactant is a combination of 2 (methylamino) ethyl methacrylate, N-N dimethyl bisacrylamide and itaconic acid, or a combination of 2 (methylamino) ethyl methacrylate, N-N dimethyl bisacrylamide and 2-acrylamido-2-methylpropanesulfonic acid; the mass ratio of the 2 (methylamino) ethyl methacrylate to the N-N dimethyl bisacrylamide to the itaconic acid is 2-6:2-6:1, and the mass ratio of the 2 (methylamino) ethyl methacrylate to the N-N dimethyl bisacrylamide to the 2-acrylamide-2-methylpropanesulfonic acid is 1-3:1-3: 1.

According to the invention, the cross-linking agent a is one or the combination of more than two of inositol, glycerol, 1, 2-propylene glycol, polyethylene glycol, hydroxymethyl acrylamide, poly (epoxy dialkyl glycol), maleic acid, toluene diisocyanate or glutaraldehyde; preferably, the cross-linking agent is one or a combination of two of hydroxymethyl acrylamide and glutaraldehyde.

According to the invention, the moderate temperature initiator is preferably a low temperature initiation system, a medium temperature initiator or a high temperature initiator; the low-temperature initiating system is ammonium persulfate-sodium bisulfite, potassium persulfate-sodium bisulfite or ammonium persulfate-sodium thiosulfate, the medium-temperature initiating agent is azobisisobutyrimidazoline hydrochloride or azobisisopropylimidazoline hydrochloride, and the high-temperature initiating agent is dicumyl peroxide, cumyl peroxide or tert-butyl hydroperoxide.

According to the invention, the water-soluble resin toughening agent is preferably carboxymethyl water-soluble urea-formaldehyde resin, water-soluble epoxy resin, water-soluble acrylic resin or water-soluble phenolic resin. The above raw materials are commercially available or prepared according to the prior art.

According to the invention, the composite inorganic toughening agent is preferably a combination of three or more of sepiolite wool, natural mica powder, hydrophilic fumed silica, ultrafine light calcium carbonate, shell powder, vermiculite, acicular wollastonite fibers, coke particles and calcite particles; the composite inorganic toughening agent simultaneously comprises a fiber material and rigid particles, and the particle size of the rigid particles is less than 200 mu m. Preferably, the composite inorganic toughening agent is composed of sepiolite wool, superfine light calcium carbonate and needle-shaped wollastonite fibers, and the mass ratio of the sepiolite wool, the superfine light calcium carbonate and the needle-shaped wollastonite fibers is 1-3:1: 1. The above raw materials are all commercially available.

According to the invention, the modified starch is preferably one or the combination of more than two of corn acetate, potato acetate, cassava acetate, corn phosphate, potato phosphate or cassava phosphate. The above raw materials are commercially available or prepared according to the prior art.

According to the invention, the preferable rheology regulator is one or the combination of more than two of magnesium lithium silicate, sodium bentonite, organic bentonite, titanium dioxide, diatomite powder, sodium carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, guar gum or xanthan gum.

According to the invention, the volume expansion reactant is preferably prepared from the following raw materials in parts by mass: 100 parts of dispersion medium, 8-15 parts of water-soluble polymeric monomer, 20-50 parts of emulsifier, 0.05-0.2 part of oil phase initiator and 0.2-3 parts of cross-linking agent b. The volume expansion reaction agent is a high water absorption resin material.

Preferably, the volume expansion reactant comprises the following raw materials in parts by mass: 100 parts of dispersion medium, 8-12 parts of water-soluble polymeric monomer, 20-30 parts of emulsifier, 0.05-0.15 part of oil phase initiator and 0.2-1 part of cross-linking agent b.

Preferably, the water-soluble polymeric monomer is one or a combination of two of acrylic acid or 2-acrylamido-methylpropanesulfonic acid; further preferably, the water-soluble polymeric monomer is acrylic acid.

Preferably, the dispersion medium is one or a combination of two or more of petroleum ether, toluene, o-xylene, isoparaffin, cyclohexane, heptane, octane, white oil, and kerosene.

Preferably, the emulsifier is one or a combination of more than two of sorbitan monooleate (span 80), propylene glycol fatty acid ester (EmcolPL 50), sorbitan monostearate (span 60) or diethylene glycol monooleate (Emcol DO-50).

Preferably, the oil phase initiator is one or a combination of two or more of azobisisobutyronitrile, azobisisoheptonitrile, tert-butyl hydroperoxide, tert-butyl peroxybenzoate, dialkyl-mercaptan peroxide, diacyl-tertiary amine peroxide or ammonium persulfate-sodium bicarbonate.

Preferably, the crosslinking agent b is one or a combination of more than two of inositol, glycerol, 1, 2-propylene glycol, polyethylene glycol, hydroxymethyl acrylamide, poly (epoxydialkene glycol), maleic acid, toluene diisocyanate or glutaraldehyde.

Preferably, the preparation method of the volume expansion reactant comprises the following steps:

(1) fully dispersing an emulsifier in a dispersion medium to obtain an oil phase;

(2) dissolving water-soluble polymerized monomer in water, and dripping 15-25% sodium hydroxide aqueous solution at-5-5 deg.C to make the neutralization degree of the water-soluble polymerized monomer 70-80% to obtain polymerized monomer aqueous solution;

(3) slowly dripping a polymerization monomer aqueous solution into the oil phase obtained in the step (1), then adding an oil phase initiator and a cross-linking agent b, fully dissolving, reacting for 4-8h at 40-60 ℃ in an oxygen-free inert atmosphere, and then performing rotary evaporation, filtration, drying, crushing and grinding, and screening with a 100-mesh screen to obtain the bulk swelling reactant.

Further preferably, in the step (2), the mass ratio of the water-soluble polymerized monomer to water is 1:3 to 5.

Preferably, in the step (3), the water is discharged by rotary evaporation, and in the rotary evaporation process, the reaction solution is continuously heated for 2-4h after boiling; the filtration is performed by using a 100-mesh filter screen; the drying temperature is 55-65 ℃, the drying time is 24-36h, and the full drying is taken as a standard.

The preparation method of the bulk-swelling type high-efficiency slug gel plugging agent comprises the following steps:

i. dissolving a polymerization reaction agent in water, adding a cross-linking agent a, and fully and uniformly dispersing to obtain a solution A;

ii. Fully dispersing a water-soluble resin toughening agent and a composite inorganic toughening agent in water to obtain a solution B;

iii, fully dispersing the modified starch in water, and gelatinizing for 40-60min at the temperature of 55-65 ℃ in a stirring, oxygen-free and inert atmosphere to obtain starch gelatinization liquid;

iv, adding the bulk swelling reactant, the solution B, the starch pasting liquid and the rheological regulator into the solution A, fully and uniformly mixing to obtain a bulk swelling type efficient slug gel plugging agent main body, and finally adding a proper temperature initiator according to the requirements of gelling temperature and time, and uniformly mixing; then carrying out polymerization reaction in an oxygen-free inert atmosphere to obtain the bulk-swelling efficient slug gel plugging agent. The obtained plugging agent is in a flowing state, and is favorable for injection into a stratum.

Preferably, in step i, the mass ratio of the polymerization reagent to the water is 1: 3-10; in the step ii, the mass ratio of the water-soluble resin toughening agent to the water is 1: 10-20; in step iii, the mass ratio of the modified starch to the water is 1: 4-8.

Preferably according to the invention, in step iv, a low temperature initiation system is used when the ambient temperature is between 30 and 60 ℃, the low temperature initiation system being between 0.02 and 0.2 parts; when the environmental temperature is 60-90 ℃, a medium-temperature initiator is adopted, and the medium-temperature initiator accounts for 0.02-0.15 part; when the ambient temperature is 90-120 ℃, a high-temperature initiator is adopted, and the high-temperature initiator accounts for 0.05-0.5 part.

Preferably, according to the invention, in step iv, the polymerization temperature is 30 to 120 ℃ and varies according to the isothermal initiator; the polymerization reaction time is 4-8 h.

According to the invention, the plugging agent obtained by the invention is injected into the formation fracture, and the plugging agent continuously undergoes polymerization reaction at the formation temperature until the plugging agent becomes gel, and simultaneously absorbs water to expand, so that the plugging agent stays in the formation fracture to realize a good plugging effect.

The principle of the invention is as follows:

(1) the main body of the swelling type high-efficiency slug gel plugging agent is a gel formed by connecting a plurality of monomers through covalent bonds. Molecular chains are subjected to dehydration condensation reaction under the action of a cross-linking agent, and are cross-linked with each other to form a net structure; in the process, water molecules are contained in the lattice structure to form gel adaptive to leakage channels such as cracks and the like, and the gel has good water absorption performance, so that the underground working fluid is physically blocked, and the purpose of plugging is achieved. The use of proper cross-linking agent not only avoids the problem that the formation of a three-dimensional network space of gel is difficult due to low cross-linking density, but also prevents the phenomena that the three-dimensional network space of the original water molecule is controlled to be too small and difficult to absorb water and expand due to overhigh cross-linking density. The invention selects a specific kind of polymerization reagent and uses a specific kind of cross-linking agent, which is beneficial to improving the comprehensive properties of the obtained gel, such as plugging property, water absorption property, mechanical strength and the like.

(2) The water-soluble resin with hydrophilic groups such as carboxyl, hydroxyl and the like is used as the toughening material, so that good compatibility with the gel matrix can be realized.

(3) The acetate starch and the phosphate starch adopted in the plugging agent respectively contain acetate and phosphate, and both have the effects of reducing the gelatinization temperature of starch in practical application and simultaneously have strong hydrophilic water-locking capacity, so that the underground water absorption and retention capacity of gel can be further improved, and the gel further keeps high expansion factor and is firmly attached to a leakage space. On the other hand, as the modified starch is produced and prepared under the action of enzyme, heating, stirring and the like, the aggregation between the molecular chains of the starch is destroyed originally, the dense arrangement of the starch molecules is destroyed, and water molecules can enter the starch granules more easily.

(4) The hydrophilic groups in the volume expansion reactant are the prime power of the gel capable of absorbing water and expanding, and the neutralization degree of the water-soluble polymerized monomers in the volume expansion reactant directly influences the number of the hydrophilic groups on a molecular chain, so that the water absorption and expansion capacity of the gel is influenced. And when the neutralization degree is low, on one hand, the crosslinking points formed by hydrophilic group carboxyl through hydrogen bonds are increased, so that the volume swelling reactant is highly crosslinked and is not easy to absorb water, and on the other hand, the carboxylate content is reduced, so that the molecular chain anion repulsion is reduced, and the molecular net space structure is not easy to expand, so that the water absorption capacity is reduced. Therefore, the addition of sodium hydroxide neutralizes acrylic acid to a certain extent to increase the water-absorbing expansion capacity of the volume expansion reactant.

(5) The composite inorganic toughening material is preferably rigid particle and fiber material. Wherein the fiber material mainly plays a role of 'lacing wire' in the process of plugging cracks; the fibers flow in the liquid gel in a single-strip or cluster-shaped form, and can be entangled with fine nano rigid particles in the flowing process to finally form clusters of the fibers and the rigid particles, the behavior of the fibers, the fibers and the particles being entangled greatly enhances the toughness and the stability of the gel after being gelatinized, the mechanical strength of the gel in a leaking layer is enhanced, and the gel can still maintain better toughness and is not damaged when bearing larger pressure from formation fluid. The selected rigid particles have good water dispersibility, the preferred particle size is less than 200 mu m, the specific surface area is larger, the surface activity is large, the hydrophilic groups can form the action far greater than the action force between molecules on the interface of the hydrophilic groups, and micro cracks can be well initiated to absorb energy; in addition, due to the rigidity of the particles, the crack deflects when meeting the particles during expansion, and the function of absorbing energy to achieve toughening is achieved; the rigid particles have good compatibility with resin and gel, so that the dispersion capacity and the absorption energy of a gel matrix to pressure-bearing impact and tensile energy are improved, and a good toughness increasing effect is realized.

(6) The initiator selected by the invention is broken by weak base at a certain temperature to generate active groups, thereby promoting the polymerization reaction. The initiator used in the invention has decomposition activation energy in the range of 60-190kJ/mol, and the formation temperature condition can ensure that the initiator decomposes to generate free radicals to adjust the polymerization reaction rate. The invention selects the initiator with specific concentration, and avoids the phenomenon that the water absorption expansion capacity of the gel is weakened due to implosion caused by overhigh concentration of the initiator.

The invention has the following beneficial effects:

(1) the bulk-swelling type high-efficiency slug gel plugging agent has the advantages of self-adaption of the gelling temperature and adjustable gelling time, the gelling temperature range is 30-120 ℃, and the gelling temperature adaption condition is wide. The invention sets three different initiation temperature conditions by simulating the formation temperature, and utilizes the characteristics of the initiator decomposition activation energy, thereby not only avoiding the problems of low free radical collision rate, reduced molecular crosslinking degree and low gel expansion ratio generated by the initiator due to low temperature condition, but also avoiding the problems of increased active center, increased polymerization and crosslinking reaction, reduced space grid for controlling water molecules and small gel water absorption expansion ratio due to high temperature condition.

(2) The conventional bridging plug plugging material or the toughening material in the plugging slurry is easy to gather at the bottom of a crack space under the action of gravitational potential energy and cannot completely cover the crack space, the plugging effect on a vertical crack is particularly poor, and the plugging is realized mainly by stacking the materials, so that the plugging material is damaged under the pumping of a shaft working solution, and the labor and the material resources are greatly consumed. The high-efficiency swelling slug gel plugging agent can stay in a leakage space in the process of injecting into a leakage layer by selecting a rheological agent with a thickening effect, gradually gelatinizes under a specific temperature condition, and fills cracks. The components of the plugging agent are taken as a whole, and the plugging agent has good mechanical properties such as toughness, tensile resistance and the like after being formed into gel and has larger water absorption expansion capacity, so that the crack is further extruded and filled, the matching degree with the size of the crack is high, a channel of working fluid and formation fluid is isolated, and a good plugging effect is realized; meanwhile, the gel after water absorption still has excellent mechanical strength; has wide research prospect and plugging field requirement.

(3) The invention utilizes the inverse emulsion polymerization method to synthesize the volume swelling reactant, has higher polymerization rate compared with the solution polymerization method, and can improve the molecular weight at the same time. The molecular size of the volume swelling reactant resin is related to the molecular weight of the resin; the molecular weight of the resin is increased, so that the molecular size of the resin can be improved; when the resin is in a salt solution, molecular chains of the resin shrink and curl under the influence of the electrostatic shielding effect and the dehydration effect of calcium and magnesium cations, and the molecular size is reduced, so that the influence of metal ions on the water absorption performance of the resin can be reduced by increasing the molecular weight of the volume swelling reactant. The volume expansion reaction agent synthesized by the reverse emulsion polymerization method is beneficial to improving the salt resistance and water absorption performance of the volume expansion reaction agent.

(4) At present, due to the limitation of exploration and development technologies, an empirical evaluation method is often adopted for downhole leaking stoppage, namely, the size of a leaking space is judged according to the leaking rate of working fluid and the position of a sampling leaking position when leaking occurs, a set of leaking stoppage materials with matched sizes is formulated for leaking stoppage, and certain blindness and incompleteness are still achieved even if some leaking stoppage particles with water absorption expansion are adopted. The efficient bulk-expanded slug gel plugging principle of the invention is 'stopping when leaking, gelling when stopping, absorbing water and reinforcing', the crack size does not need to be matched, the time for evaluating the crack size is greatly reduced, the pumping of a leaking layer is simple, the method is beneficial to field construction application, and the method has wide application and research prospects.

Drawings

Fig. 1 is a pressure-bearing leakage-stopping force diagram of the bulk-swelling type high-efficiency slug gel leakage-stopping agent prepared in example 1.

Fig. 2 is a pressure-bearing leakage-stopping force diagram of the bulk-swelling type high-efficiency slug gel leakage-stopping agent prepared in example 2.

Fig. 3 is a pressure-bearing leakage-stopping force diagram of the bulk-swelling high-efficiency slug gel leakage-stopping agent prepared in example 3.

Fig. 4 is a pressure-bearing leakage-stopping force diagram of the gel leakage-stopping agent prepared in comparative example 1.

Fig. 5 is a pressure-bearing leak-stopping force diagram of the gel leak-stopping agent prepared in comparative example 2.

Fig. 6 is a pressure-bearing leakage-stopping force diagram of the gel leakage-stopping agent prepared in comparative example 3.

Fig. 7 is a pressure-bearing leakage-stopping force diagram of the gel leakage-stopping agent prepared in comparative example 4.

Fig. 8 is a pressure-bearing leakage-stopping force diagram of the gel leakage-stopping agent prepared in comparative example 5.

Detailed Description

The present invention is described in detail below with reference to examples, but the present invention is not limited thereto.

The methods described in the examples are conventional methods unless otherwise specified; the reagents used are commercially available without further indication.

Example 1

The bulk-swelling type efficient slug gel plugging agent is prepared from the following raw materials in parts by mass: 25 parts of polymerization reaction agent, 2 parts of cross-linking agent, 0.08 part of proper temperature initiator, 4 parts of water-soluble resin toughening agent, 4 parts of composite inorganic toughening agent, 4 parts of modified starch, 6 parts of volume expansion reaction agent and 4 parts of rheological control agent.

The polymerization reactant is composed of 2 (methylamino) ethyl methacrylate, N-N dimethyl bisacrylamide and itaconic acid, wherein the mass ratio of the 2 (methylamino) ethyl methacrylate to the N-N dimethyl bisacrylamide to the itaconic acid is 4:4: 1.

The cross-linking agent is composed of hydroxymethyl acrylamide and glutaraldehyde, wherein the mass ratio of the hydroxymethyl acrylamide to the glutaraldehyde is 2: 1.

The proper-temperature initiator selects a low-temperature initiation system ammonium persulfate-sodium thiosulfate (the mass ratio of the ammonium persulfate to the sodium thiosulfate is 1:1), and the corresponding polymerization reaction temperature is 45 ℃.

The water-soluble resin toughening agent is carboxymethyl water-soluble urea-formaldehyde resin (sold by Zhengzhou Haohao chemical product Co., Ltd.) and water-soluble acrylic resin (sold by Suzhou Qingtian new material Co., Ltd.), and the mass ratio is 2: 1.

The composite inorganic toughening agent consists of sepiolite wool, superfine light calcium carbonate (with the grain diameter of 50-100nm) and needle-shaped wollastonite fiber. Wherein the mass ratio of the sepiolite fibers, the superfine light calcium carbonate fibers and the needle-shaped wollastonite fibers is 2:1: 1.

The modified starch is corn acetate and corn phosphate, and the mass ratio of the corn acetate to the corn phosphate is 2: 1.

The rheology modifier consists of magnesium lithium silicate and hydroxyethyl cellulose, wherein the mass ratio of the magnesium lithium silicate to the hydroxyethyl cellulose is 1: 1.

The volume expansion reactant is prepared from the following raw materials in parts by mass: 100 parts of dispersion medium, 10 parts of water-soluble polymeric monomer, 25 parts of emulsifier, 0.1 part of oil phase initiator and 0.8 part of cross-linking agent.

Wherein, the water-soluble polymeric monomer is acrylic acid, the dispersion medium is white oil, the emulsifier is sorbitan monostearate (span 60), the oil phase initiator is tert-butyl peroxybenzoate, and the cross-linking agent is inositol.

The preparation process of the volume expansion reactant comprises the following specific steps:

(1) 25 parts of an emulsifier is weighed and dissolved in 100 parts of a dispersion medium in a three-necked flask, and the mixture is sufficiently stirred to be uniform to prepare an oil phase.

(2) 10 parts of water-soluble polymerized monomer is dissolved in deionized water (the mass ratio of the water-soluble polymerized monomer to the deionized water is 1:4), the mixture is placed in an ice water bath (0 ℃), and then a 20 wt% sodium hydroxide aqueous solution is slowly dripped to ensure that the neutralization degree is 75%, so as to obtain a polymerized monomer aqueous solution.

(3) Slowly dripping the aqueous solution of the polymerization monomer into the oil phase in the step (1), weighing 0.1 part of oil phase initiator and 0.8 part of cross-linking agent, respectively adding the initiator and the cross-linking agent into the oil phase, fully stirring and dissolving the initiator and the cross-linking agent by using a magnetic stirrer, connecting a nitrogen bottle, smoothly introducing nitrogen to remove oxygen for a period of time, and sealing. Then at 60 deg.CThe reaction is carried out in a water bath. In the above preparation process, the nitrogen oxygen removal is based on a 500ml three-neck flask and should be 100cm³Nitrogen was passed through at a rate of/min for 10 minutes.

(4) After the reaction was carried out for 4 hours, the solution was transferred to a rotary evaporator, heated to boil and drained. The heating time from boiling should be 3 h.

(5) And after heating, pouring out the supernatant, filtering the lower-layer product by using a 100-mesh filter screen, taking out, transferring to a vacuum drying oven, setting the temperature at 60 ℃, and setting the time at 36h, wherein full drying is taken as a standard. And finally, crushing and grinding the product until the product passes through a 100-mesh screen to obtain the volume swelling reactant.

The preparation process of the bulk-swelling type high-efficiency slug gel plugging agent is as follows:

(1) firstly, dissolving 25 parts of needed polymerization reaction agent in a three-neck flask filled with deionized water (the mass ratio of the polymerization reaction agent to the deionized water is 1:5), adding 2 parts of cross-linking agent, adding magnetons, fully stirring for a period of time at normal temperature by adopting a magnetic stirrer, and fully and uniformly dispersing to obtain a solution A.

(2) Mixing 4 parts of water-soluble resin toughening agent and 4 parts of composite inorganic toughening agent in a beaker filled with deionized water (the mass ratio of the water-soluble resin toughening agent to the deionized water is 1:12), adding magnetons, fully stirring for a period of time by using a magnetic stirrer, and fully and uniformly dispersing to obtain a solution B.

(3) 4 parts of modified starch is weighed by an electronic balance and placed in a three-neck flask filled with deionized water (the mass ratio of the modified starch to the deionized water is 1:6), a magneton is placed in the three-neck flask, and a stirring knob is turned on for stirring. Connecting nitrogen cylinder pipeline, introducing nitrogen gas with stable gas flow for a period of time to remove oxygen in the cylinder, and sealing after deoxygenation. And (3) placing the flask at 60 ℃ for a period of time, fully gelatinizing the modified starch in the flask for 40min to obtain starch gelatinization liquid.

(4) Adding 6 parts of swelling reactant, solution B, starch pasting liquid and 4 parts of rheological regulator which are prepared in advance into the solution A in the flask, adding magnetons, fully stirring by using a magnetic stirrer, and uniformly mixing to obtain a productA main body of the swelling type high-efficiency slug gel plugging agent; then 0.08 part of proper temperature initiator is added, and the mixture is fully stirred and uniformly mixed; communicating a nitrogen bottle with the three-neck flask, introducing nitrogen to remove oxygen, and sealing after the oxygen is removed; and transferring the blend to 45 ℃ for polymerization reaction for 6 hours to obtain a product, namely the bulk-expanding high-efficiency slug gel plugging agent. The plugging agent is injected into and stays in the formation fracture under the corresponding temperature condition for a period of time, and then a good plugging effect can be realized. In the above preparation process, the nitrogen oxygen removal is based on a 500ml three-neck flask and should be 100cm³Nitrogen was passed through at a rate of/min for 10 minutes.

Example 2

The bulk-swelling type efficient slug gel plugging agent is prepared from the following raw materials in parts by mass: 25 parts of polymerization reaction agent, 2 parts of cross-linking agent, 0.1 part of proper temperature initiator, 4 parts of water-soluble resin toughening agent, 4 parts of composite inorganic toughening agent, 4 parts of modified starch, 6 parts of volume expansion reaction agent and 4 parts of rheological control agent.

The polymerization reactant is composed of 2 (methylamino) ethyl methacrylate, N-N dimethyl bisacrylamide and 2-acrylamido-2-methylpropanesulfonic acid, wherein the mass ratio of the 2 (methylamino) ethyl methacrylate to the N-N dimethyl bisacrylamide to the 2-acrylamido-2-methylpropanesulfonic acid is 2:2: 1.

The moderate temperature initiator is selected from the moderate temperature initiator of azodiisopropyl imidazoline hydrochloride, and the corresponding polymerization reaction temperature is 75 ℃.

The water-soluble resin toughening agent is carboxymethyl water-soluble urea-formaldehyde resin and water-soluble acrylic resin, and the mass ratio is 2: 1.

The composite inorganic toughening agent consists of sepiolite wool, superfine light calcium carbonate and needle-shaped wollastonite fiber. Wherein the mass ratio of the sepiolite fibers, the superfine light calcium carbonate fibers and the needle-shaped wollastonite fibers is 2:1: 1.

The raw material composition and the preparation method of the volume expansion reactant are consistent with those of example 1.

(4) Adding 6 parts of a bulk swelling reactant, the solution B, the starch pasting liquid and 4 parts of a rheological regulator which are prepared in advance into the solution A in the flask, adding magnetons, fully stirring by using a magnetic stirrer, and uniformly mixing to obtain a bulk swelling type high-efficiency slug gel plugging agent main body; then 0.1 part of proper temperature initiator is added, and the mixture is fully stirred and uniformly mixed; communicating a nitrogen bottle with the three-neck flask, introducing nitrogen to remove oxygen, and sealing after the oxygen is removed; and transferring the blend to the temperature of 75 ℃ for polymerization reaction for 5 hours to obtain a product, namely the bulk-expanding high-efficiency slug gel plugging agent. The plugging agent is injected into and stays in the formation fracture under the corresponding temperature condition for a period of time, and then a good plugging effect can be realized. The above-mentioned systemIn the preparation process, the nitrogen is deoxidized by 100cm according to the standard of a three-neck flask with 500ml³Nitrogen was passed through at a rate of/min for 10 minutes.

Example 3

The cross-linking agent is glutaraldehyde.

The proper temperature initiator is high temperature initiator tert-butyl hydroperoxide, and the corresponding polymerization temperature is 105 ℃.

(4) Adding 6 parts of a bulk swelling reactant, the solution B, the starch pasting liquid and 4 parts of a rheological regulator which are prepared in advance into the solution A in the flask, adding magnetons, fully stirring by using a magnetic stirrer, and uniformly mixing to obtain a bulk swelling type high-efficiency slug gel plugging agent main body; then 0.08 part of proper temperature initiator is added, and the mixture is fully stirred and uniformly mixed; communicating a nitrogen bottle with the three-neck flask, introducing nitrogen to remove oxygen, and sealing after the oxygen is removed; and transferring the blend to the temperature of 105 ℃ for polymerization reaction for 5 hours to obtain a product, namely the bulk-expanding high-efficiency slug gel plugging agent. The plugging agent is injected into and stays in the formation fracture under the corresponding temperature condition for a period of time, and then a good plugging effect can be realized. In the above preparation process, the nitrogen oxygen removal is based on a 500ml three-neck flask and should be 100cm³Nitrogen was passed through at a rate of/min for 10 minutes.

Comparative example 1

The gel plugging agent is prepared from the following raw materials in parts by mass: 25 parts of polymerization reaction agent, 2 parts of cross-linking agent, 0.08 part of proper temperature initiator, 4 parts of water-soluble resin toughening agent, 4 parts of composite inorganic toughening agent, 4 parts of modified starch, 6 parts of volume expansion reaction agent and 4 parts of rheological control agent.

The polymerization reactant is 2 (methylamino) ethyl methacrylate.

The preparation method of the bulk-swelling type high-efficiency slug gel plugging agent is the same as that of the embodiment 1.

Comparative example 2

The gel plugging agent is prepared from the following raw materials in parts by mass: 25 parts of polymerization reaction agent, 2 parts of cross-linking agent, 0.1 part of proper temperature initiator, 4 parts of water-soluble resin toughening agent, 4 parts of composite inorganic toughening agent, 6 parts of volume expansion reaction agent and 4 parts of rheological control agent.

The preparation process of the plugging agent is as described in example 2, except that: step (3) of starch gelatinization is omitted; no starch pasting liquid is added in the step (4); the other steps and conditions were identical to those of example 2.

Comparative example 3

The gel plugging agent is prepared from the following raw materials in parts by mass: 25 parts of polymerization reaction agent, 2 parts of cross-linking agent, 0.08 part of proper temperature initiator, 4 parts of water-soluble resin toughening agent, 4 parts of inorganic toughening agent, 4 parts of modified starch, 6 parts of volume expansion reaction agent and 4 parts of rheological control agent.

The cross-linking agent is glutaraldehyde.

The inorganic toughening agent is superfine light calcium carbonate.

The preparation process of the gel plugging agent is the same as that of the example 3.

Comparative example 4

The gel plugging agent is prepared from the following raw materials in parts by mass: 25 parts of polymerization reactant, 2 parts of cross-linking agent, 0.08 part of proper temperature initiator, 4 parts of composite inorganic toughening agent, 4 parts of modified starch, 6 parts of volume expansion reactant and 4 parts of rheological regulator.

The preparation process of the plugging agent is as described in example 1, except that: in the step (2), no water-soluble resin toughening agent is added; the other steps and conditions were identical to those of example 1.

Comparative example 5

The gel plugging agent is prepared from the following raw materials in parts by mass: 25 parts of polymerization reagent, 2 parts of cross-linking agent, 0.08 part of proper temperature initiator, 4 parts of water-soluble resin toughening agent, 4 parts of composite inorganic toughening agent, 4 parts of modified starch and 4 parts of rheology modifier.

The preparation process of the gel plugging agent is as described in example 1, except that: in the step (4), no volume expansion reaction agent is added; the other steps and conditions were identical to those of example 1.

Test example 1

The HKY type high-temperature high-pressure leaking stoppage displacement device and the simulated core holder produced by Haian county oil scientific research instruments ltd are adopted to test the pressure-bearing leaking stoppage capability of the leaking stoppage agent, and the method comprises the following specific steps:

(1) the temperature of the heating box is adjusted to be 45 ℃, 75 ℃ and 105 ℃ according to the requirement by simulating the formation temperature for carrying out the experiment.

(2) And (3) finishing assembling the wedge-shaped cracks with the inlet of 20 multiplied by 7mm and the outlet of 20 multiplied by 5mm, filling the wedge-shaped cracks into the core holder, connecting the injection section with the discharge end pipeline, and injecting clear water and increasing confining pressure to 5 MPa.

(3) Filling clear water in the non-stirring intermediate container, closing the water injection communicating valve, opening the plugging agent injection communicating valve, performing hydraulic displacement at a pumping speed of 10.0ml/min, and driving the plugging agent solution into the core holder until the plugging agent solution at the pipeline outlet is leaked out.

(4) And closing the plugging agent injection pipeline and the outlet valve, opening the outlet pipeline after the core holder is heated in the oven for 6 hours, opening the water injection communication valve and a pipeline interface at the front end of the core holder, and performing hydraulic displacement at a pumping rate of 10.0ml/min to remove gel remained at the front end of the core holder until clear water is discharged from the front end pipeline.

(5) And (4) after the residual gel is discharged, assembling a pipeline, opening a discharge end valve, continuously injecting clean water into the core holder at the injection rate of 10.0ml/min for displacement, and recording the pressure change and the maximum breakthrough pressure in real time by using processing software.

Fig. 1-3 are pressure-bearing plugging ability diagrams of the bulk-expansion-type high-efficiency slug gel plugging agent prepared in examples 1-3, and it can be known from the diagrams that the bulk-expansion-type high-efficiency slug gel plugging agent has high pressure-bearing plugging strength, and can realize a maximum plugging pressure of 7MPa for a wedge-shaped crack with a crack length of 20mm, an inlet crack width of 7mm, and an outlet crack width of 5mm, which indicates that the bulk-expansion-type high-efficiency slug gel plugging agent is expanded by self water absorption in the crack, and has high toughness and anti-damage ability. FIGS. 4 to 8 are pressure-bearing leakage-stopping performance diagrams of the gel leakage-stopping agents prepared in comparative examples 1 to 5, respectively, and it can be seen from the diagrams that the gel leakage-stopping agent has poor leakage-stopping effect under the conditions that the gel self-gelling strength cannot be effectively improved, the water-absorbing swelling is realized, and the material toughening is realized, and the gel leakage-stopping agent is easy to be damaged by fluid and has low pressure-bearing leakage-stopping capacity due to low strength in wedge-shaped cracks with the length of 20mm, the width of an inlet crack of 7mm and the width of an outlet crack of 5.

Test example 2

The water-absorbing expansion performance, namely the water-absorbing expansion times, of the gel plugging agent is measured by adopting a discharge volume method. Cutting the gel plugging agent which is not dried after gelling (gelling for 6h at gelling temperature) into 1 × 1 × 1cm³And putting the cubic small blocks with the sizes into a beaker with the temperature of 60 ℃ and sufficient clear water, standing for 36 hours, taking out the cubic small blocks after the cubic small blocks are completely put into the beaker, wiping off redundant water on the surface, and measuring the water absorption expansion times of the gel plugging agent by adopting a discharge volume method. The test results are shown in table 1 below.

TABLE 1 gel Water swelling test results

As can be seen from Table 1, the plugging agent has excellent water-swelling performance which is superior to that of a comparative example due to the combined action of various raw materials; when the swelling-free reactant provides enough hydrophilic groups, the water absorption capacity of the gel plugging agent is in a greatly reduced state.

Test example 3

A WAW-1000C + model electro-hydraulic servo universal testing machine produced by the Jinan New test gold testing machine Limited liability company is adopted to test the tensile strength. Cutting the gel plugging agent which is not dried after gelling (gelling for 6h at the gelling temperature) into cube blocks with the size of 2 multiplied by 5cm, setting the stretching speed to be 50.0mm/min, placing the upper end and the lower end of the gel into a clamp, and measuring and recording the tensile strength and the elongation at break. The tensile strength was calculated using the following formula.

σ＝F/(l·h)

Wherein F is tensile stress, l is gel block width, h is sample strip thickness, and l and h are both 2 cm.

The test results are shown in table 2 below:

TABLE 2 gel toughness test results

As can be seen from Table 2, the raw material components of the invention exert the combined action, so that the obtained plugging agent has excellent mechanical properties after being gelled; the gel presents certain elastic toughness after gelling, the tensile strength of the gel can be greatly improved under the synergistic effect of the resin toughening agent and the composite inorganic toughening agent, the resin toughening agent provides crosslinking sites for a gel polymer molecular chain, the formation of a three-dimensional reticular space is facilitated, the composite inorganic toughening agent provides clusters of fibers and particles to form a rigid framework, the gel toughness is further improved, and the result shows that the elastic toughness of the gel plugging agent is obviously improved under the addition of the toughening material.

Claims

1. The bulk-swelling type efficient slug gel plugging agent is prepared from the following raw materials in parts by mass: 10-35 parts of polymerization reaction agent, 1-3 parts of cross-linking agent a, 0.02-0.5 part of proper temperature initiator, 0.5-5 parts of water-soluble resin toughening agent, 0.5-5 parts of composite inorganic toughening agent, 2-8 parts of modified starch, 2-10 parts of volume expansion reaction agent and 2-8 parts of rheological regulator; the volume expansion reactant is prepared from the following raw materials by an inverse emulsion polymerization method: water-soluble polymerization monomer, dispersion medium, emulsifier, oil phase initiator and cross-linking agent b.

2. The bulk-swelling efficient slug gel plugging agent as claimed in claim 1, which is characterized by comprising the following raw materials in parts by mass: 25-30 parts of polymerization reaction agent, 1-3 parts of cross-linking agent a, 0.08-0.1 part of proper temperature initiator, 3-5 parts of water-soluble resin toughening agent, 3-5 parts of composite inorganic toughening agent, 4-8 parts of modified starch, 2-6 parts of volume expansion reaction agent and 2-6 parts of rheological control agent.

3. The swelling type high-efficiency slug gel plugging agent according to claim 1, characterized by comprising one or more of the following conditions:

a. the polymerization reactant is a combination of three or more than three of N, N' -methylene bisacrylamide, 2 (methylamino) ethyl methacrylate, N-N dimethyl bisacrylamide, partially hydrolyzed polyacrylamide, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, itaconic acid, methyl methacrylate, hydroxypropyl acrylate or hydroxyethyl methacrylate; preferably, the polymerization reactant is a combination of 2 (methylamino) ethyl methacrylate, N-N dimethyl bisacrylamide and itaconic acid, or a combination of 2 (methylamino) ethyl methacrylate, N-N dimethyl bisacrylamide and 2-acrylamido-2-methylpropanesulfonic acid; the mass ratio of the 2 (methylamino) ethyl methacrylate to the N-N dimethyl bisacrylamide to the itaconic acid is 2-6:2-6:1, and the mass ratio of the 2 (methylamino) ethyl methacrylate to the N-N dimethyl bisacrylamide to the 2-acrylamido-2-methylpropanesulfonic acid is 1-3:1-3: 1;

b. the cross-linking agent a is one or the combination of more than two of inositol, glycerol, 1, 2-propylene glycol, polyethylene glycol, hydroxymethyl acrylamide, poly (epoxy dialkyl glycol), maleic acid, toluene diisocyanate or glutaraldehyde; preferably, the cross-linking agent is one or the combination of two of hydroxymethyl acrylamide and glutaraldehyde;

c. the moderate-temperature initiator is a low-temperature initiation system, a medium-temperature initiator or a high-temperature initiator; the low-temperature initiating system is ammonium persulfate-sodium bisulfite, potassium persulfate-sodium bisulfite or ammonium persulfate-sodium thiosulfate, the medium-temperature initiating agent is azobisisobutylimidazoline hydrochloride or azobisisopropylimidazoline hydrochloride, and the high-temperature initiating agent is dicumyl peroxide, cumyl peroxide or tert-butyl hydroperoxide;

d. the water-soluble resin toughening agent is carboxymethyl water-soluble urea-formaldehyde resin, water-soluble epoxy resin, water-soluble acrylic resin or water-soluble phenolic resin;

e. the composite inorganic toughening agent is a combination of three or more than three of sepiolite wool, natural mica powder, hydrophilic fumed silica, superfine light calcium carbonate, shell powder, vermiculite, acicular wollastonite fibers, coke particles and calcite particles; the composite inorganic toughening agent simultaneously comprises a fiber material and rigid particles, and the particle size of the rigid particles is less than 200 mu m; preferably, the composite inorganic toughening agent consists of sepiolite wool, superfine light calcium carbonate and needle-shaped wollastonite fibers, and the mass ratio of the sepiolite wool to the superfine light calcium carbonate to the needle-shaped wollastonite fibers is 1-3:1: 1;

f. the modified starch is one or the combination of more than two of corn acetate, potato acetate, cassava acetate, corn phosphate, potato phosphate or cassava phosphate;

g. the rheological control agent is one or more of lithium magnesium silicate, sodium bentonite, organic bentonite, titanium dioxide, diatomite powder, sodium carboxymethylcellulose, hydroxyethyl cellulose, methylcellulose, guar gum or xanthan gum.

4. The bulk-swelling efficient slug gel plugging agent as claimed in claim 1, wherein the bulk-swelling reactant is prepared from the following raw materials in parts by mass: 100 parts of dispersion medium, 8-15 parts of water-soluble polymeric monomer, 20-50 parts of emulsifier, 0.05-0.2 part of oil phase initiator and 0.2-3 parts of cross-linking agent b.

5. The bulk-swelling efficient slug gel plugging agent as claimed in claim 4, wherein the bulk-swelling reactant is prepared from the following raw materials in parts by mass: 100 parts of dispersion medium, 8-12 parts of water-soluble polymeric monomer, 20-30 parts of emulsifier, 0.05-0.15 part of oil phase initiator and 0.2-1 part of cross-linking agent b.

6. The swelling type high-efficiency slug gel plugging agent according to claim 4, characterized by comprising one or more of the following conditions:

a. the water-soluble polymerized monomer is one or the combination of two of acrylic acid or 2-acrylamide-methyl propanesulfonic acid; further preferably, the water-soluble polymeric monomer is acrylic acid;

b. the dispersion medium is one or the combination of more than two of petroleum ether, toluene, o-xylene, isoparaffin, cyclohexane, heptane, octane, white oil or kerosene;

c. the emulsifier is one or the combination of more than two of sorbitan monooleate (span 80), propylene glycol fatty acid ester (EmcolPL 50), sorbitan monostearate (span 60) or diethylene glycol monooleate (Emcol DO-50);

d. the oil phase initiator is one or the combination of more than two of azodiisobutyronitrile, azodiisoheptonitrile, tert-butyl hydroperoxide, tert-butyl peroxybenzoate, dialkyl-mercaptan peroxide, diacyl-tertiary amine peroxide or ammonium persulfate-sodium bicarbonate;

e. the cross-linking agent b is one or the combination of more than two of inositol, glycerol, 1, 2-propylene glycol, polyethylene glycol, hydroxymethyl acrylamide, poly (epoxy dialkyl glycol), maleic acid, toluene diisocyanate or glutaraldehyde.

7. The bulk-swelling efficient slug gel plugging agent as claimed in claim 4, wherein the preparation method of the bulk-swelling reactant comprises the steps of:

8. The swelling type high-efficiency slug gel plugging agent according to claim 7, characterized by comprising one or more of the following conditions:

a. in the step (2), the mass ratio of the water-soluble polymerized monomer to water is 1: 3-5;

b. in the step (3), the rotary evaporation is carried out to discharge water, and in the rotary evaporation process, the reaction solution is continuously heated for 2-4 hours after boiling; the filtration is performed by using a 100-mesh filter screen; the drying temperature is 55-65 ℃, the drying time is 24-36h, and the full drying is taken as a standard.

9. The preparation method of the swelling type high-efficiency slug gel plugging agent as claimed in any one of claims 1 to 8, comprising the steps of:

iv, adding the bulk swelling reactant, the solution B, the starch pasting liquid and the rheological regulator into the solution A, fully and uniformly mixing to obtain a bulk swelling type efficient slug gel plugging agent main body, and finally adding a proper temperature initiator according to the requirements of gelling temperature and time, and uniformly mixing; then carrying out polymerization reaction in an oxygen-free inert atmosphere to obtain the bulk-swelling efficient slug gel plugging agent.

10. The preparation method of the swelling type high-efficiency slug gel plugging agent according to claim 9, characterized by comprising one or more of the following conditions:

a. in the step i, the mass ratio of the polymerization reactant to the water is 1: 3-10; in the step ii, the mass ratio of the water-soluble resin toughening agent to the water is 1: 10-20; in the step iii, the mass ratio of the modified starch to the water is 1: 4-8;

b. in the step iv, a low-temperature initiation system is adopted when the ambient temperature is 30-60 ℃, and the low-temperature initiation system is 0.02-0.2 part; when the environmental temperature is 60-90 ℃, a medium-temperature initiator is adopted, and the medium-temperature initiator accounts for 0.02-0.15 part; when the ambient temperature is 90-120 ℃, a high-temperature initiator is adopted, and the high-temperature initiator accounts for 0.05-0.5 part;

c. in the step iv, the polymerization reaction temperature is 30-120 ℃, and the polymerization reaction temperature is different according to different proper temperature initiators; the polymerization reaction time is 4-8 h.