CN113249101B - Preparation method of water-soluble composite temporary plugging agent for diversion fracturing - Google Patents

Preparation method of water-soluble composite temporary plugging agent for diversion fracturing Download PDF

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CN113249101B
CN113249101B CN202110551188.9A CN202110551188A CN113249101B CN 113249101 B CN113249101 B CN 113249101B CN 202110551188 A CN202110551188 A CN 202110551188A CN 113249101 B CN113249101 B CN 113249101B
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plga
peg
temporary plugging
plugging agent
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CN113249101A (en
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李乃旭
李美娟
周建成
邢舒雅
刘珺
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Southeast University
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    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
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Abstract

The invention disclosesA preparation method of a water-soluble composite temporary plugging agent for diversion fracturing belongs to the technical field of oilfield chemistry, and the temporary plugging agent mainly comprises the raw materials of Lactide (LA), Glycolide (GA) and polyethylene glycol (PEG) in a mass fraction ratio of 5:1: 1-5: 1:1.5, wherein the molecular weight M of the PEG isnIn the range of 1500-4000. Firstly, synthesizing a PLGA-PEG-PLGA prepolymer by the existing method, on the basis, firstly, adopting diisocyanate chain extenders comprising one or two of 2, 4-Toluene Diisocyanate (TDI), 4' -diphenylmethane diisocyanate (MDI) and Hexamethylene Diisocyanate (HDI), carrying out chain extension on the prepolymer to obtain a high polymer, wherein the molar ratio of the chain extender to the prepolymer is 1: 1-2: 1, and then, mixing the high polymer with polytrimethylene carbonate (PTMC) and nano silicon dioxide (SiO)2) Mixing the mixture to obtain SiO2a/PLGA-PEG-PLGA/PTMC composite material, PLGA-PEG-PLGA high polymer: 80-85 parts of PTMC: 5 to 8 parts of SiO2: 6-8 parts of the material serving as a water-soluble temporary plugging agent has better temporary plugging performance.

Description

Preparation method of water-soluble composite temporary plugging agent for diversion fracturing
Technical Field
The invention belongs to the technical field of oilfield chemistry, and particularly relates to a preparation method of a water-soluble composite temporary plugging agent for diversion fracturing.
Background
In recent years, as the development of oil and gas fields enters the middle and later stages, the exploitation of high-permeability reservoirs is almost exhausted, and the tight gas sandstone becomes the first key point of oil and gas exploitation in China. Due to the reasons of serious formation heterogeneity, large interlayer permeability difference and the like, the physical properties of a high-permeability reservoir can only be improved by the conventional production increasing measures, and the physical properties of a low-permeability reservoir are still poor. The formation property is not uniform, which easily causes the injected water to permeate into the inside of the oil well of the pore canal, and seriously affects the quality of oil exploitation. In order to improve the overall efficiency of petroleum engineering, a high-rise permeable layer must be reasonably plugged, and the water seepage effect of an oil well is reduced as much as possible. The chemical temporary plugging agent is used as the most main water plugging method and has very important function in the application in the field of petroleum engineering. The chemical temporary plugging agent can be classified into a cross-linked polymer type, a fiber type, an inorganic salt type and a complex type according to the composition.
The crosslinked polymer temporary plugging agent is also called polymer gel temporary plugging agent, namely, the polymer is subjected to crosslinking reaction under the action of the crosslinking agent, the polymer is a skeleton in a gel structure, and the crosslinking agent is a bridging agent for gathering polymer molecules together. According to the viscosity change, the temporary plugging agent can be divided into two main stages in the construction process: a crosslinking reaction stage and a degradation reaction stage, namely a gelation stage and a gel breaking stage. At present, the practical application of the temporary plugging agent on site is limited to a certain extent, the gelling and gel breaking time is long, and the temporary plugging agent is difficult to operate under the conditions of high temperature and high pressure.
The fiber for diverting the temporary plugging application is mainly plant fiber and modified products thereof. Typical materials include polyester fibers, polylactic acid fibers and polypropylene fibers. During the reconstruction of oil and gas well construction, the fibers are first softened in a carrier liquid and injected into the reservoir together with the carrier liquid. The long and short fibers are intertwined with each other in the pore throats or internal cracks to form a three-dimensional network structure, i.e., a "filter cake (screen)" structure, thereby producing a plugging effect. At present, the fiber temporary plugging agent has some defects in construction application, such as limited pressure bearing capacity; the application range is narrow, and the method cannot be used for large-opening cracks; and the heat resistance and the chemical stability are poor, and the particles are easy to agglomerate to block pipelines, so that the application is limited to a certain extent.
Most of the inorganic salt temporary plugging agents are granular temporary plugging agents, and common materials comprise calcium carbonate, sodium chloride, benzoic acid and the like. The inorganic salt particle temporary plugging agent has the advantages of easy regulation and control of particle size, low breakage rate, high plugging strength, easy plugging removal, small damage to stratum, easy acquisition of raw materials and low cost, but is not suitable for plugging large-opening cracks due to small particle size, generally has large injection amount and incomplete plugging removal, and has certain limitation in the current application.
The composite temporary plugging agent is prepared by mixing two or more materials, so that the materials play a synergistic effect, for example, an inorganic substance and a polymer material are compounded, the mechanical property and the chemical property of a single temporary plugging agent material can be greatly improved, the application range of the composite temporary plugging agent is expanded, the composite temporary plugging agent can be used for various oil and gas reservoirs, is a temporary plugging agent with a better practical application effect in the current construction process, and is an important research direction of the temporary plugging agent in the future.
Polylactic acid, also known as polylactide, is a non-toxic, completely biodegradable, green polymeric material as a thermoplastic aliphatic polyester, the final degradation product of which is CO2And H2And O, no pollution to the environment is caused. Compared with other traditional high polymer materials such as PE, PP and PVC, polylactic acid has many outstanding advantages such as good biocompatibility, processability and the like, so that the polylactic acid is more and more valued by people today, but the polylactic acid has the defects of brittleness, poor impact resistance, poor thermal stability and the like, so that the application range of the polylactic acid in the current market is greatly limited.
Disclosure of Invention
The technical problem is as follows: the invention provides a preparation method of a water-soluble composite temporary plugging agent for diversion fracturing, which improves the thermal stability and mechanical property of the temporary plugging agent.
The technical scheme is as follows: in order to solve the technical problems, the preparation method of the water-soluble composite material temporary plugging agent for the diversion fracturing comprises the following steps:
1) lactide, glycolide and polyethylene glycol form a p-PLGA-PEG-PLGA triblock prepolymer;
2) adopting a chain extender to carry out chain extension on the PLGA-PEG-PLGA triblock prepolymer to obtain a PLGA-PEG-PLGA high polymer;
3) the water-soluble temporary plugging agent for the diverting fracturing is prepared by using PLGA-PEG-PLGA high polymer as a blending raw material.
Further, the structure of the PPLGA-PEG-PLGA triblock prepolymer is as follows:
Figure BDA0003075473510000021
for omitting intermediate chain segments
Figure BDA0003075473510000022
Replacing; the chain extensionThe agent is as follows: O-N-R-N-C-O
The PLGA-PEG-PLGA high polymer has the following structure:
Figure BDA0003075473510000023
wherein x, y, z and n are polymerization degrees, and x: 34-90, y: 21-35, z: 5-9, n: 5 to 6, number average molecular weight M of high polymern：30000～40000g/mol。
Further, in the step 1), the mass ratio of the lactide to the glycolide to the polyethylene glycol is 5:1: 1-5: 1: 1.5.
Further, in the step 3), the blended raw materials comprise the following components in percentage by mass: 80-85% of PLGA-PEG-PLGA high polymer, 5-8% of polytrimethylene carbonate, 6-9% of nano reinforced material, 3% of plasticizer, 0.5% of antioxidant and 0.5% of lubricant.
Further, the nano reinforcing material is SiO2The plasticizer is polyethylene glycol, and the antioxidant is tetra [ beta- (3, 5-di-tert-butyl, 4-hydroxyphenyl) propionic acid]Pentaerythritol tetraester alcohol; the lubricant is ethylene bis stearamide.
Further, adding stannous octoate with the total mass fraction of 0.8 wt% into the flask in the step 1), vacuumizing, and filling N into the flask2Protecting, heating to 100-110 ℃, stirring until the materials are completely dissolved, heating to 140-150 ℃, reacting for 18-24 h in a molten state to obtain the PPLGA-PEG-PLGA triblock prepolymer, adding dichloromethane until the oligomer is just dissolved, adding glacial ethyl ether to separate out oily liquid, removing supernatant, and drying the oily liquid in a constant-temperature drying oven overnight to obtain pure and dry PPLGA-PEG-PLGA triblock prepolymer, wherein the reaction equation is shown as follows:
Figure BDA0003075473510000031
further, in the step 2), the PPLGA-PEG-PLGA triblock prepolymer and the chain extender are in a molar ratio of 1: 1E to EAdding the mixture into a three-neck flask in a ratio of 1:2, vacuumizing, and filling N2Protecting, heating to 120-140 ℃, stirring and reacting for 30-60 min, adding dichloromethane to dissolve the product, adding anhydrous methanol to separate out oily liquid or precipitate, and drying in a vacuum drying oven to obtain PLGA-PEG-PLGA high polymer, wherein the reaction equation is as follows:
Figure BDA0003075473510000032
further, in the step 3), the blended raw materials are added into a double-screw extruder, and physical melt blending is carried out at the temperature of 180-200 ℃, and extrusion granulation is carried out to obtain the temporary plugging agent particles with the particle size of 0.2-7 mm.
The invention principle is as follows: the invention firstly adopts copolymerization modification, adopts polyethylene glycol (PEG) as a macromolecular initiator, and adds stannous octoate (Sn (Oct)2) Under the catalytic action of (3), Lactide (LA) and Glycolide (GA) undergo ring-opening polymerization to form a PLGA-PEG-PLGA triblock prepolymer. The GA copolymerization modification can reduce the crystallinity of polylactic acid, improve the toughness and mechanical property and accelerate the degradation rate; the PEG copolymerization modification can improve the hydrophilicity, flexibility and impact resistance of the polymer. And then, chain extension is carried out on the PLGA-PEG-PLGA triblock prepolymer by a diisocyanate chain extender, the molecular weight is improved, a net-shaped structure is formed among PLA chain segments through chemical bonds, the movement of the molecular chain segments is restrained, the thermal stability and the mechanical property of the material are improved, and the PLGA-PEG-PLGA triblock polymer is obtained. Finally, the nano-reinforcing material is prepared by mixing the nano-reinforcing material with polytrimethylene carbonate (PTMC) and nano-reinforcing material (SiO)2) The Plasticizer (PEG) and the like are subjected to toughening, plasticizing and heat-resistant blending modification to obtain the water-soluble temporary blocking material, so that the toughness, the impact resistance and the heat resistance of the composite material are improved, and in addition, the PTMC material has good hydrophilicity, can accelerate the hydrolysis speed of the composite material and simultaneously ensures the balance of the toughness and the rigidity. The volume grow after this temporary plugging agent absorbs water and swells, can form the shutoff effect to the crack, and this temporary plugging agent is different from current water-soluble temporary plugging agent: (1) the blockage removal does not need to add a gel breaker, and the gel breaker can be dissolved in water at 90 ℃ by self to realize complete blockage removal; (2) the anti-pressure performance is good,the temporary plugging function can be realized under the high-temperature and high-pressure stratum environment.
Has the advantages that: compared with the prior art, the invention has the advantages that:
(1) the composite temporary plugging agent is one of composite temporary plugging agents, is a modification research on polylactic acid materials, can be completely degraded after being used on the premise of realizing a good temporary plugging effect, can be suitable for a high-temperature and high-pressure stratum environment, and has the advantage of wide application range; LA, GA and PEG are used as main raw materials of the temporary plugging agent, and the three materials are environment-friendly materials and have no pollution to the environment after being degraded;
(2) diisocyanate is used as a chain extender, so that the molecular weight of the polymer is increased, the oligomer is changed into a high polymer, and the thermal stability and the mechanical property of the temporary plugging agent are improved;
(3) by high polymer and poly trimethylene carbonate (PTMC), nano reinforced material (SiO)2) The Plasticizer (PEG) and the like are subjected to toughening, plasticizing and heat-resistant blending modification, so that the ductility, impact resistance and heat resistance of the temporary plugging material are improved, the polytrimethylene carbonate material has good hydrophilicity, the hydrolysis speed of the temporary plugging material can be accelerated, and in addition, the dissolution temperature and dissolution speed can be regulated and controlled by regulating the proportion of each blending component;
(4) the temporary plugging agent has a plugging removal mechanism different from that of the existing water-soluble temporary plugging agent, and can realize complete plugging removal only under the action of certain temperature and water without adding a plugging removal agent;
(5) compared with the existing water-soluble temporary plugging agent, the temporary plugging agent has the advantages of stronger bearing capacity and better heat resistance, has wider application range and can be applied to low-permeability oil and gas reservoirs with high temperature and high pressure.
Drawings
FIG. 1 is an infrared spectrum of a water-soluble PLGA-PEG-PLGA prepolymer and a high polymer synthesized in example 2;
fig. 2 is a diagram of a sample of the finally synthesized particles of the temporary plugging agent in example 2.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
A temporary plugging agent of water-soluble composite material for steering fracturing is mainly based on a triblock copolymer composed of Lactide (LA), Glycolide (GA) and polyethylene glycol (PEG), and a chain extender is adopted to carry out chain extension on a PLGA-PEG-PLGA triblock prepolymer to obtain a high polymer, wherein the structural formula of the main components is as follows:
PPLGA-PEG-PLGA triblock prepolymer:
Figure BDA0003075473510000051
because the structural formula of the PLGA-PEG-PLGA prepolymer is longer, the middle chain segment is omitted
Figure BDA0003075473510000052
Instead.
Chain extender: O-N-R-N-C-O
PLGA-PEG-PLGA high Polymer:
Figure BDA0003075473510000053
wherein x, y, z and n are polymerization degrees, and x: 34-90, y: 21-35, z: 5-9, n: 5 to 6, number average molecular weight M of high polymern：30000～40000g/mol。
The temporary plugging agent is prepared from the raw materials of LA, GA and PEG in a mass ratio of 5:1: 1-5: 1: 1.5. The final blending raw materials comprise the following components in percentage by mass: 80-85% of high polymer, 5-8% of polytrimethylene carbonate and nano reinforced material (SiO)2)6 to 9 percent of plasticizer polyethylene glycol 3 percent of antioxidant 1010 (tetra [ beta- (3, 5-di-tert-butyl, 4-hydroxyphenyl) propionic acid)]Pentaerythritol alcohol) 0.5%, lubricant EBS (ethylene bis stearamide) 0.5%.
A synthetic method of a water-soluble composite temporary plugging agent for diversion fracturing comprises the following steps:
(1) adding 5 parts of lactide, 1 part of glycolide and 1-1.5 parts of polyethylene glycol into a three-neck flask;
(2) adding stannous octoate (Sn (Oct) with the total mass fraction of 0.8 wt% into the flask in the step (1)2) Making catalyst, vacuumizing, and filling N2Protecting, heating to 100-110 ℃, stirring until the materials are completely dissolved, heating to 140-150 ℃, reacting for 18-24 h in a molten state to obtain the PPLGA-PEG-PLGA triblock prepolymer, adding a small amount of dichloromethane until the oligomer is just dissolved, adding glacial ethyl ether to separate out oily liquid, removing supernatant, and drying the oily liquid in a constant-temperature drying oven overnight to obtain pure and dry PPLGA-PEG-PLGA triblock prepolymer, wherein the reaction equation is as follows:
Figure BDA0003075473510000061
(3) adding the reaction product obtained in the step (2) and a chain extender into a three-neck flask according to the molar ratio of 1: 1-1: 2, vacuumizing, and then filling N2Protecting, heating to 120-140 ℃, stirring and reacting for 30-60 min, adding dichloromethane to dissolve the product, adding anhydrous methanol to separate out oily liquid or precipitate, and drying in a vacuum drying oven to obtain PLGA-PEG-PLGA high polymer, wherein the reaction equation is as follows:
Figure BDA0003075473510000062
(4) adding 80-85 parts of PLGA-PEG-PLGA high polymer obtained in the step (3), 5-8 parts of polytrimethylene carbonate (PTMC) and nano reinforcing material (SiO) into a double-screw extruder2) 6-8 parts of Plasticizer (PEG), 3 parts of small amount of antioxidant 10100.5 parts and 0.5 part of lubricant EBS, and carrying out physical melt blending at 180-200 ℃, extruding and granulating to obtain temporary plugging agent particles with the particle size of 0.2-7 mm.
Example 1
The synthetic method of the water-soluble composite temporary plugging agent for diversion fracturing in the embodiment comprises the following steps:
(1) adding 5 parts of lactide, 1 part of glycolide and 1 part of polyethylene glycol (PEG-1500) into a three-neck flask;
(2) adding stannous octoate (Sn (Oct) with the total mass fraction of 0.8 wt% into the flask in the step (1)2) Making catalyst, vacuumizing, and filling N2Protecting, heating to 100 ℃, stirring until the materials are completely dissolved, heating to 150 ℃, reacting for 18h in a molten state to obtain a PPLGA-PEG-PLGA triblock prepolymer, adding a small amount of dichloromethane until the oligomer is just dissolved, adding glacial ethyl ether to separate out oily liquid, removing supernatant, and then placing the oily liquid in a constant-temperature drying oven to dry overnight to obtain pure and dry PPLGA-PEG-PLGA triblock prepolymer;
(3) adding the reaction product obtained in the step (2) and a chain extender 2, 4-Toluene Diisocyanate (TDI) into a three-neck flask according to the molar ratio of hydroxyl (-OH) to isocyanate (-NCO) of 1:1, vacuumizing, and filling N2Protecting, heating to 120 ℃, stirring and reacting for 60min, adding dichloromethane to dissolve the product, adding anhydrous methanol to separate out oily liquid or precipitate, and drying in a vacuum drying oven to obtain PLGA-PEG-PLGA high polymer;
(4) adding 80 parts of PLGA-PEG-PLGA high polymer obtained in the step (3), 8 parts of polytrimethylene carbonate (PTMC) and nano reinforcing material (SiO) into a double-screw extruder2)8 parts of Plasticizer (PEG), 3 parts of Plasticizer (PEG), 0.5 part of very small antioxidant and 0.5 part of lubricant, and the mixture is subjected to physical melt blending at 180 ℃ and extrusion granulation to obtain temporary plugging agent particles with the particle size of 0.2-7 mm.
Example 2
Synthetic method of water-soluble composite temporary plugging agent for diversion fracturing
Preparing materials: weighing the main raw materials according to the following table
Name of raw materials Code Dosage of
Lactide GA 5 portions of
Glycolide LA 1 part of
Polyethylene glycol PEG-2000 1.2 parts of
The specific operation steps are as follows: distilling polyethylene glycol at 130 deg.C under reduced pressure for 3 hr to remove water, adding 5 parts of lactide, 1 part of glycolide, 1.2 parts of polyethylene glycol ((PEG-2000)), and 0.8 wt% catalyst stannous octoate (Sn (Oct)2) Vacuum pumping and N filling2Repeating the steps for 3 times to ensure that the reaction environment is anhydrous and anaerobic, heating to 110 ℃ to completely melt the materials, stirring for 1h, continuing heating to 140 ℃, reacting for 22h, cooling, adding a small amount of dichloromethane to dissolve the materials, adding glacial ethyl ether to separate out oily liquid, removing supernatant, and placing in a drying oven at 40 ℃ overnight to obtain the PLGA-PEG-PLGA triblock oligomer. Adding chain extender 4, 4' -diphenylmethane diisocyanate (MDI) into PLGA-PEG-PLGA prepolymer, wherein the molar ratio of the prepolymer to the MDI is 1:1.5, vacuumizing and filling N before reaction2Protecting, heating to 130 ℃, stirring and reacting for 45min, adding dichloromethane to dissolve the product, adding anhydrous methanol to separate out oily liquid or precipitate, and drying in a vacuum drying oven to obtain the PLGA-PEG-PLGA high polymer. Adding 85 parts of PLGA-PEG-PLGA high polymer, 5 parts of polytrimethylene carbonate (PTMC) and nano reinforcing material (SiO) into a double-screw extruder2)6 parts of Plasticizer (PEG), 3 parts of Plasticizer (PEG), 10100.5 parts of antioxidant with extremely small amount and 0.5 part of lubricant EBS, and the temporary plugging agent particles with the particle size of 0.2-7mm are obtained by physical melt blending, extrusion and granulation at 190 ℃.
Example 3
Synthetic method of water-soluble composite temporary plugging agent for diversion fracturing
The specific operation steps are as follows: distilling polyethylene glycol at 130 deg.C under reduced pressure for 3 hr to remove water, adding 5 parts of lactide, 1 part of glycolide, 1.5 parts of polyethylene glycol (PEG-4000), 0.8 wt% catalyst stannous octoate (Sn (Oct)2) Vacuum pumping and N filling2Repeating the steps for 3 times to ensure that the reaction environment is anhydrous and anaerobic, heating to 105 ℃ to completely melt the materials, stirring for 1h, continuing heating to 140 ℃, reacting for 24h, cooling, adding a small amount of dichloromethane to dissolve the materials, adding glacial ethyl ether to separate out oily liquid, removing supernatant, and placing in a drying oven at 40 ℃ overnight to obtain the PLGA-PEG-PLGA triblock oligomer. Adding chain extender 4, 4' -diphenylmethane diisocyanate (MDI) and Hexamethylene Diisocyanate (HDI) into PLGA-PEG-PLGA prepolymer, wherein the molar ratio of MDI to HDI is 1:1, the molar ratio of the prepolymer to the chain extender (MDI, HDI) is 1:2, vacuumizing and filling N before reaction2Protecting, heating to 140 ℃, stirring and reacting for 30min, adding dichloromethane to dissolve the product, adding anhydrous methanol to separate out oily liquid or precipitate, and drying in a vacuum drying oven to obtain the PLGA-PEG-PLGA high polymer. Adding 83 parts of PLGA-PEG-PLGA high polymer, 6 parts of polytrimethylene carbonate (PTMC) and nano reinforcing material (SiO) into a double-screw extruder2)7 parts of Plasticizer (PEG), 3 parts of Plasticizer (PEG), 0.5 part of very small antioxidant and 0.5 part of lubricant, and the mixture is subjected to physical melt blending at the temperature of 200 ℃ and extruded and granulated to obtain temporary plugging agent particles with the particle size of 0.2-7 mm.
Water-soluble SiO2Characterization of the/PLGA-PEG-PLGA/PTMC composite material temporary plugging agent:
the infrared spectrum of the water-soluble composite material temporary plugging agent synthesized in the example is shown in FIG. 1. As can be seen, the peak positions of the PPLGA-PEG-PLGA triblock prepolymer and the high polymer are substantially the same. 3430cm-1Absorption of OHPeak at 2920cm-1Is represented by-CH3-CH and-CH2Stretching vibration peak of 1760cm-1An absorption peak of 1380cm at C ═ O-1Is represented by-CH31180cm of bending vibration peak of-1And 1090cm-1Is located at 1605cm of the stretching vibration peak of C-O-C-1The peak is the stretching vibration peak of N-C ═ O in the amide, which indicates that the isocyanate group is successfully introduced.
Water-soluble SiO synthesized in this example2A graph of a particle sample of the/PLGA-PEG-PLGA/PTMC composite temporary blocking agent is shown in FIG. 2.
Water-soluble SiO2And (3) determining the temporary plugging strength of the temporary plugging agent of the/PLGA-PEG-PLGA/PTMC composite material.
The temporary plugging performance of the temporary plugging agent is represented by breakthrough pressure and permeability, and the higher the breakthrough pressure is, the higher the pressure which can be borne by the temporary plugging agent is; after breakthrough, the permeability is not changed obviously, which indicates that the temporary plugging effect of the temporary plugging agent is obvious and the stratum can be plugged continuously. The experimental result of the temporary plugging performance test shows that the water plugging rate of the temporary plugging agent is 99%, and in addition, in the displacement process, the breakthrough pressure of the temporary plugging agent is 53.5MPa, which shows that the temporary plugging agent has higher temporary plugging strength.
Water-soluble SiO2Determination of deblocking performance of/PLGA-PEG-PLGA/PTMC composite material temporary blocking agent
The good and bad degradation performance of the temporary plugging agent relates to whether the temporary plugging agent can effectively plug cracks and realize self-plugging removal. If the temporary plugging agent has poor degradability, and after the fracturing construction is finished, the temporary plugging agent cannot be degraded quickly, the temporary plugging agent is filled between the proppants for a long time to prevent oil and gas from normally permeating, and although the fracturing purpose can be achieved, the yield of oil and gas fields cannot be increased, but the yield is influenced. Weighing 3g of the temporary plugging agent, placing the temporary plugging agent in a reagent bottle, adding simulated formation water and a very small amount of hydrochloric acid to adjust the pH value to about 5, stirring the mixture in an oil bath kettle at 90 ℃, completely dissolving the temporary plugging agent within 7 days, and observing whether the solution in the reagent bottle is uniform and has no solid phase, which indicates that the temporary plugging agent has good plugging removal performance.
The above is an embodiment of the present invention. The embodiments and specific parameters in the embodiments are only for the purpose of clearly illustrating the verification process of the invention and are not intended to limit the scope of the invention, which is defined by the claims, and all equivalent structural changes made by using the contents of the specification and the drawings of the present invention should be covered by the scope of the present invention.

Claims (5)

1. A preparation method of a water-soluble composite material temporary plugging agent for diversion fracturing is characterized in that,
1) preparing a PLGA-PEG-PLGA triblock prepolymer by lactide, glycolide and polyethylene glycol;
2) adopting a chain extender to carry out chain extension on the PLGA-PEG-PLGA triblock prepolymer to obtain a PLGA-PEG-PLGA high polymer;
3) the water-soluble temporary plugging agent for the diverting fracturing is prepared by taking PLGA-PEG-PLGA high polymer as a blending raw material;
the structure of the PPLGA-PEG-PLGA triblock prepolymer is as follows:
Figure FDA0003458545930000011
for omitting intermediate chain segments
Figure FDA0003458545930000012
Replacing; the chain extender comprises: O-N-R-N-C-O
The PLGA-PEG-PLGA high polymer has the following structure:
Figure FDA0003458545930000013
wherein x, y, z and n are polymerization degrees, and x: 34-90, y: 21-35, z: 5-9, n: 5 to 6, number average molecular weight M of high polymern：30000～40000g/mol；
The blended raw materials comprise the following components in percentage by mass: 80 to 85 percent of PLGA-PEG-PLGA high polymer and polytrimethylene carbon5-8% of acid ester, 6-9% of nano reinforcing material, 3% of plasticizer, 0.5% of antioxidant and 0.5% of lubricant; the nano reinforced material is SiO2The plasticizer is polyethylene glycol, and the antioxidant is tetra [ beta- (3, 5-di-tert-butyl, 4-hydroxyphenyl) propionic acid]Pentaerythritol tetraester alcohol; the lubricant is ethylene bis stearamide.
2. The preparation method of the water-soluble composite temporary plugging agent for diversion fracturing as claimed in claim 1, wherein in step 1), the mass ratio of lactide, glycolide and polyethylene glycol is 5:1: 1-5: 1: 1.5.
3. The preparation method of the water-soluble composite material temporary plugging agent for diversion fracturing as claimed in claim 1, wherein stannous octoate with total mass fraction of 0.8 wt% is added into the flask in the step 1), and N is filled after vacuum pumping2Protecting, heating to 100-110 ℃, stirring until the materials are completely dissolved, heating to 140-150 ℃, reacting for 18-24 h in a molten state to obtain the PPLGA-PEG-PLGA triblock prepolymer, adding dichloromethane until the oligomer is just dissolved, adding glacial ethyl ether to separate out oily liquid, removing supernatant, and drying the oily liquid in a constant-temperature drying oven overnight to obtain pure and dry PPLGA-PEG-PLGA triblock prepolymer, wherein the reaction equation is shown as follows:
Figure FDA0003458545930000021
4. the preparation method of the water-soluble composite material temporary plugging agent for diversion fracturing as claimed in claim 1, wherein the PPLGA-PEG-PLGA triblock prepolymer and the chain extender in the step 2) are added into a three-neck flask according to a molar ratio of 1: 1-1: 2, and N is filled after vacuum pumping2Protecting, heating to 120-140 ℃, stirring and reacting for 30-60 min, adding dichloromethane to dissolve the product, adding absolute methanol to separate out oily liquid or precipitate, and drying in a vacuum drying ovenDrying to obtain PLGA-PEG-PLGA high polymer, wherein the reaction equation is as follows:
Figure FDA0003458545930000022
5. the preparation method of the temporary plugging agent for the water-soluble composite material for diversion fracturing as claimed in claim 1, wherein in step 3), the blended raw materials are added into a twin-screw extruder, and physical melt blending and extrusion granulation are carried out at 180-200 ℃ to obtain temporary plugging agent particles with the particle size of 0.2-7 mm.
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