Thermal expansion material, resin liquid bridge plug and deep shale gas shaft pressure-bearing plugging method

Abstract

The invention provides a thermal expansion material, a resin liquid bridge plug and a deep shale gas shaft pressure-bearing plugging method. The thermal expansion material comprises a combination of any two or three of oxidative polymerization grafted 3-alkylthiophene modified thermal expansion microspheres, glycidyl methacrylate grafted modified thermal expansion microspheres and cinnamyl nitrile and diethyl fumarate cross-linked thermal expansion core-shell microspheres; by taking the total weight of the thermal expansion material as 100%, when the thermal expansion material comprises an oxidative polymerization grafted 3-alkylthiophene modified thermal expansion microsphere, a glycidyl methacrylate grafted modified thermal expansion microsphere and a cinnamyl nitrile and diethyl fumarate cross-linked thermal expansion core-shell microsphere, the contents of the three are respectively 15-55%, 25-75% and 30-65%. The thermal expansion material has good compatibility with resin liquid bridge plugs, can be uniformly dispersed in resin, does not agglomerate or settle, and can effectively inhibit the shrinkage of the resin through heat release expansion after solidification.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of thermal expansion material, resin liquid bridge plug and deep shale gas wellbore pressure containment method, belong to shale gas reservoir development technical field. BACKGROUND

[0002] Deep shale gas reservoir often faces the challenge of wellbore casing severe change, which not only increases the difficulty of exploitation, but also may threaten the integrity of wellbore. In order to solve this problem, the person skilled in the art will generally consider using advanced technology of chemical bridge plug to carry out pressure containment of wellbore. As a kind of efficient and reliable wellbore isolation method, chemical bridge plug is particularly suitable for well section with severe casing change, which can effectively ensure the integrity and safety of wellbore. This kind of chemical bridge plug material is designed uniquely, which fully utilizes the flow characteristics of liquid. During operation, these special liquid materials can flow smoothly through narrow wellbore and accurately reach the fracturing section. Once reaching the predetermined position, these liquids will quickly solidify to form a solid bridge plug, thereby realizing effective plugging and pressure containment of wellbore.

[0003] The existing liquid bridge plug material is mainly resin material and gel material. Among them, the gel material has low strength and cannot meet the plugging length requirement of fracturing, while although the resin material has high mechanical strength, the material will shrink after heat release and solidification, which leads to its inability to effectively bond with the wellbore wall.

[0004] Therefore, it has become a technical problem to be solved in the field to provide a new type of thermal expansion material, resin liquid bridge plug and deep shale gas wellbore pressure containment method. SUMMARY

[0005] In order to solve the above-mentioned shortcomings and deficiencies, the purpose of the present application is to provide a kind of thermal expansion material, resin liquid bridge plug and deep shale gas wellbore pressure containment method. The thermal expansion material provided by the present application has good compatibility with resin liquid bridge plug, can be uniformly dispersed in resin, does not agglomerate and does not settle, and can effectively inhibit the shrinkage of resin through heat release and expansion after solidification.

[0006] In order to achieve the above purpose, on the one hand, the present application provides a kind of thermal expansion material, wherein the thermal expansion material includes any two or three combinations of oxidized polymer grafted 3-alkyl thiophene modified thermal expansion microspheres, glycidyl methacrylate grafted modified thermal expansion microspheres and cinnamaldehyde and fumaric acid diethyl ester crosslinked thermal expansion core-shell microspheres;

[0007] When the heat-expandable material comprises the oxidatively polymerized grafting 3-alkyl thiophene modified heat-expandable microspheres, the glycidyl methacrylate grafting modified heat-expandable microspheres, and the cinnamaldehyde and diethyl fumarate crosslinking heat-expandable core-shell microspheres, the content of the three is 15-55%, 25-75%, and 30-65% respectively based on the total weight of the heat-expandable material being 100%. That is, when the heat-expandable material comprises the combination of the three kinds of microspheres, namely the oxidatively polymerized grafting 3-alkyl thiophene modified heat-expandable microspheres, the glycidyl methacrylate grafting modified heat-expandable microspheres, and the cinnamaldehyde and diethyl fumarate crosslinking heat-expandable core-shell microspheres, the content of the three is 15-55%, 25-75%, and 30-65% respectively based on the total weight of the heat-expandable material being 100%, and the total content of the three is 100%; when the heat-expandable material comprises the combination of any two of the three kinds of microspheres, namely the oxidatively polymerized grafting 3-alkyl thiophene modified heat-expandable microspheres, the glycidyl methacrylate grafting modified heat-expandable microspheres, and the cinnamaldehyde and diethyl fumarate crosslinking heat-expandable core-shell microspheres, the content of the three is 15-55%, 25-75%, and 30-65% respectively based on the total weight of the heat-expandable material being 100%, and the total content of any two of the microspheres is 100%, such as when the heat-expandable material comprises the combination of the oxidatively polymerized grafting 3-alkyl thiophene modified heat-expandable microspheres and the glycidyl methacrylate grafting modified heat-expandable microspheres, the content of the two is 15-55% and 25-75% respectively, and the total content of the two is 100%.

[0008] As a specific embodiment of the above-mentioned heat-expandable material of the present application, the particle size distribution of the oxidatively polymerized grafting 3-alkyl thiophene modified heat-expandable microspheres, the glycidyl methacrylate grafting modified heat-expandable microspheres, and the cinnamaldehyde and diethyl fumarate crosslinking heat-expandable core-shell microspheres is 100-500 μm.

[0009] As a specific embodiment of the above-mentioned heat-expandable material of the present application, the alkyl in the oxidatively polymerized grafting 3-alkyl thiophene modified heat-expandable microspheres comprises a normal alkyl with carbon number of 10-15.

[0010] As a specific embodiment of the above-mentioned heat-expandable material of the present application, the oxidatively polymerized grafting 3-alkyl thiophene modified heat-expandable microspheres is obtained by oxidative polymerization reaction using thiophene ester copolymer grafting modified heat-expandable microspheres and 3-alkyl thiophene as raw materials.

[0011] The mass ratio of the thiophene ester copolymer grafting modified heat-expandable microspheres and 3-alkyl thiophene is 90-110:1, and the oxidative polymerization reaction is carried out at 25-35°C for 0.5-1.5h, preferably 0.5-1h.

[0012] As a specific embodiment of the thermal expansion material described above in the present application, the oxidatively polymerized graft 3-alkyl thiophene modified thermal expansion microspheres are prepared by a preparation method comprising the following specific steps:

[0013] Step 1: the thiophene ester copolymer grafted modified thermal expansion microspheres and 3-alkyl thiophene are added to an organic solvent according to the above target mass ratio and mixed uniformly;

[0014] Step 2: an initiator is added to the mixture obtained in Step 1 to cause the oxidative polymerization of 3-alkyl thiophene to form an oxidized polymer, and the oxidized polymer is introduced onto the thiophene ester copolymer grafted modified thermal expansion microspheres to obtain the oxidatively polymerized graft 3-alkyl thiophene modified thermal expansion microspheres.

[0015] The specific substance and its amount of the organic solvent used in Step 1 of the preparation method of the oxidatively polymerized graft 3-alkyl thiophene modified thermal expansion microspheres described above in the present application are not specifically required, and can be reasonably selected and adjusted according to actual operation needs. For example, in some embodiments of the present application, the organic solvent can be dichloromethane, and its volume is 30 times the total mass of the reactants (thiophene ester copolymer grafted modified thermal expansion microspheres and 3-alkyl thiophene), wherein the units of volume and mass are mL and g, respectively.

[0016] In Step 1 of the preparation method of the oxidatively polymerized graft 3-alkyl thiophene modified thermal expansion microspheres described above in the present application, the uniform mixing can be achieved by sufficient stirring, and the present application does not specifically require the time of stirring, which can be reasonably adjusted as needed, as long as the purpose of uniform mixing can be achieved. For example, in some embodiments of the present application, the time of stirring can be 0.5 h.

[0017] In Step 2 of the preparation method of the oxidatively polymerized graft 3-alkyl thiophene modified thermal expansion microspheres described above in the present application, any initiator that can trigger the oxidative polymerization of 3-alkyl thiophene can be used in the present application. For example, in some embodiments of the present application, the initiator can be ammonium persulfate, and its addition amount is 0.02 wt% (calculated based on the total mass of the reactants).

[0018] Step 2 of the preparation method of the oxidatively polymerized graft 3-alkyl thiophene modified thermal expansion microspheres described above in the present application further comprises: the prepared microspherical particles are sequentially filtered, washed with acetone and dried to remove residual solvents and impurities, etc., to obtain dried modified microspheres, i.e. the oxidatively polymerized graft 3-alkyl thiophene modified thermal expansion microspheres. This graft modification can change the surface properties of the microspheres and increase their compatibility with the resin matrix.

[0019] As a specific embodiment of the above-mentioned thermal expansion material of the present application, wherein the thioether ester copolymer grafted thermal expansion microspheres are obtained by reacting on the surface of the hydroxyl functionalized thermal expansion microspheres with the hydroxyl functionalized thermal expansion microspheres, triethylamine, dimethyl amino pyridine and 2-(thiophene-3-yl)acetyl chloride as raw materials;

[0020] The mass ratio of the hydroxyl functionalized thermal expansion microspheres, triethylamine, dimethyl amino pyridine and 2-(thiophene-3-yl)acetyl chloride is 0.8-1:0.8-1.2:0.01-0.03:1.0-1.2, and the temperature of the reaction is 25-35℃.

[0021] As a specific embodiment of the above-mentioned thermal expansion material of the present application, wherein the thioether ester copolymer grafted thermal expansion microspheres are obtained by reacting on the surface of the hydroxyl functionalized thermal expansion microspheres with the hydroxyl functionalized thermal expansion microspheres, triethylamine, dimethyl amino pyridine and 2-(thiophene-3-yl)acetyl chloride as raw materials;

[0022] Step 1): mixing the hydroxyl functionalized thermal expansion microspheres and the organic solvent in a reaction container;

[0023] Step 2): slowly dropping dimethyl amino pyridine into the reaction container and mixing it uniformly;

[0024] Step 3): adding 2-(thiophene-3-yl)acetyl chloride into the reaction container to react with the hydroxyl functionalized thermal expansion microspheres;

[0025] Step 4): adding triethylamine into the reaction container to continue the reaction, and obtaining the thioether ester copolymer grafted thermal expansion microspheres after the reaction is completed.

[0026] In step 1) of the preparation method of the above-mentioned thioether ester copolymer grafted thermal expansion microspheres, the hydroxyl functionalized thermal expansion microspheres can be used as a template to form the thioether ester copolymer grafted thermal expansion microspheres with specific structure and morphology by reacting on the surface thereof;

[0027] In step 2), dimethyl amino pyridine is slowly dropped into the reaction container and mixed uniformly by stirring, and the dimethyl amino pyridine acts as a base catalyst to participate in the subsequent reaction;

[0028] The present application does not make specific requirements for the mixing time in steps 1) and 2) above, as long as the system can be mixed uniformly. For example, the stirring time in steps 1) and 2) can be 0.1-0.5h and 1-2h, respectively.

[0029] Both the triethylamine in step 4) and the dimethylaminopyridine in step 2) of the preparation method of the thienyl ester copolymer grafted heat-expandable microspheres are basic catalysts participating in the polymerization of monomers, which promotes the formation of the thienyl ester copolymer. Specifically, the ring-opening polymerization of thienyl monomers can be promoted, which helps to improve the reaction rate and control the polymerization.

[0030] The specific substance and the amount of the organic solvent used in step 1) of the preparation method of the thienyl ester copolymer grafted heat-expandable microspheres are not specifically required, and can be reasonably selected and adjusted according to the actual operation needs. For example, in some embodiments of the present application, the organic solvent can be dimethylformamide, and the volume is 30 times the total mass of the reactants (hydroxyl-functionalized heat-expandable microspheres, triethylamine, dimethylaminopyridine and 2-(thien-3-yl)acetyl chloride). The units of volume and mass are mL and g, respectively.

[0031] In step 3) of the preparation method of the thienyl ester copolymer grafted heat-expandable microspheres, the reaction time is 0.1-0.5h.

[0032] In step 4) of the preparation method of the thienyl ester copolymer grafted heat-expandable microspheres, triethylamine is used as a neutralizing agent to neutralize excess acidic substances in the reaction system. In step 4), the reaction time is 0.1-0.5h.

[0033] Step 4) of the preparation method of the thienyl ester copolymer grafted heat-expandable microspheres further comprises: sequentially filtering, washing with acetone, drying and other treatments on the prepared product to obtain the thienyl ester copolymer grafted heat-expandable microspheres.

[0034] Steps 1)-4) of the preparation method of the thienyl ester copolymer grafted heat-expandable microspheres are carried out under stirring. The stirring speed is not specifically required in the present application, and can be reasonably adjusted according to the actual operation needs on site. For example, in some embodiments of the present application, the stirring speed is 10000-15000rpm.

[0035] As a specific embodiment of the heat-expandable material described above, the hydroxyl-functionalized heat-expandable microspheres are obtained by a polymerization reaction using acrylonitrile, methacrylonitrile and 2-hydroxyethyl methacrylate as raw materials.

[0036] Among them, the amount of acrylonitrile, methacrylonitrile and 2-hydroxyethyl methacrylate is 40-60%, 30-40% and 10-20% respectively based on 100% of the total weight of the raw materials, and the polymerization reaction is carried out at 50-60℃ for 2-3h.

[0037] As a specific embodiment of the thermal expansion material of the present application described above, wherein the hydroxyl functionalized thermal expansion microspheres are prepared by a preparation method comprising the following specific steps:

[0038] Step (1): acrylonitrile and 2-hydroxyethyl methacrylate are mixed according to the target ratio, and a suitable organic solvent such as toluene is added to adjust the viscosity and concentration of the reaction system;

[0039] Step (2): methyl methacrylate is added to the mixed solution obtained in step (1) and uniformly dispersed in the mixed solution;

[0040] Step (3): an initiator is added to the mixed solution obtained in step (2) to trigger the polymerization reaction of the monomers, and the monomers are reacted at 50-60℃ for 2-3h, and the hydroxyl functionalized thermal expansion microspheres are obtained after the reaction is completed.

[0041] The present application does not make specific requirements for the amount of organic solvent in step (1) of the preparation method of the above-mentioned hydroxyl functionalized thermal expansion microspheres, and can be reasonably adjusted according to the needs, as long as the viscosity and concentration of the reaction system can be adjusted to the desired target viscosity and concentration. In some specific embodiments of the present application, the ratio of the volume of the organic solvent to the mass of the reactants (a mixture of acrylonitrile and 2-hydroxyethyl methacrylate) is 30:1, wherein the units of mass and volume are g and mL, respectively.

[0042] In step (2) of the preparation method of the above-mentioned hydroxyl functionalized thermal expansion microspheres of the present application, methyl methacrylate is added to the mixed solution obtained in step (1) and uniformly dispersed in the mixed solution by stirring. The present application does not make specific requirements for the stirring speed, which can be reasonably adjusted according to the needs. For example, in some embodiments of the present application, the stirring speed is 2000r / min.

[0043] The present application does not make specific requirements for the specific substance of the initiator used in step (3) of the preparation method of the above-mentioned hydroxyl functionalized thermal expansion microspheres and the amount thereof, and any initiator that can trigger the polymerization reaction of the monomers can be used in the present application. For example, in some specific embodiments of the present application, the initiator is ammonium persulfate.

[0044] The preparation method of the above-mentioned hydroxyl functionalized thermal expansion microspheres of the present application further comprises step (4) after step (3), which is to wash the polymer microspheres obtained after the reaction to remove residual reactants and other impurities, and then dry them to obtain the final product.

[0045] As a specific embodiment of the above-mentioned heat-expandable material of the present application, the glycidyl methacrylate graft-modified heat-expandable microspheres are obtained by grafting glycidyl methacrylate onto the surface of the α-bromoester-modified heat-expandable microspheres using α-bromoester-modified heat-expandable microspheres, glycidyl methacrylate, toluene, CuBr2, N,N,N',N",N"-pentamethyldiethylamine, ethyl 2-bromobutyrate, and ascorbic acid as raw materials;

[0046] The mass ratio of the α-bromoester-modified heat-expandable microspheres, glycidyl methacrylate, toluene, CuBr2, N,N,N',N",N"-pentamethyldiethylamine, ethyl 2-bromobutyrate, and ascorbic acid is 1-1.5:10-13:8-10:0.001-0.003:0.015-0.03:0.08-0.1:0.015-0.018, and the grafting reaction is carried out at 25-35°C for 25-50 min, preferably for 25-30 min.

[0047] As a specific embodiment of the above-mentioned heat-expandable material of the present application, the glycidyl methacrylate graft-modified heat-expandable microspheres are obtained by grafting glycidyl methacrylate onto the surface of the α-bromoester-modified heat-expandable microspheres using α-bromoester-modified heat-expandable microspheres, glycidyl methacrylate, toluene, CuBr2, N,N,N',N",N"-pentamethyldiethylamine, ethyl 2-bromobutyrate, and ascorbic acid as raw materials;

[0048] Step a: mixing CuBr2and N,N,N',N",N"-pentamethyldiethylamine in an organic solvent to prepare a copper catalyst;

[0049] Step b: suspending the α-bromoester-modified heat-expandable microspheres in toluene (solvent), adding glycidyl methacrylate, the copper catalyst, and ethyl 2-bromobutyrate (initiator), and stirring at a temperature of 25-35°C to carry out the grafting reaction. At the same time of the grafting reaction, ascorbic acid is added as a reducing agent to keep the copper catalyst in a reduced state. After 25-50 min of reaction, the glycidyl methacrylate graft-modified heat-expandable microspheres are obtained.

[0050] The present application does not make specific requirements for the organic solvent used in step a of the above-mentioned method for preparing the glycidyl methacrylate graft-modified heat-expandable microspheres, and the amount thereof, etc. They can be reasonably selected and adjusted according to actual operation needs. For example, in some embodiments of the present application, the organic solvent can be acetonitrile, and the volume thereof is 30 times the total mass of all raw materials (i.e., α-bromoester-modified heat-expandable microspheres, glycidyl methacrylate, toluene, CuBr2, N,N,N',N",N"-pentamethyldiethylamine, ethyl 2-bromobutyrate, and ascorbic acid), wherein the units of volume and mass are mL and g, respectively.

[0051] In step a of the preparation method of the glycidyl methacrylate grafted and modified thermal expansion microspheres, CuBr2 is used together with N,N,N',N",N"-pentamethyldiethyl triamine to form a catalytic system of an atom transfer radical polymerization (ATRP) reaction system, wherein the N,N,N',N",N"-pentamethyldiethyl triamine is an auxiliary ligand which can form a complex with the copper catalyst to play a role in stabilizing the active intermediate of the catalyst, and help to improve the efficiency and selectivity of the catalyst. In this system, the role of CuBr2 is to catalyze the ATRP reaction, so that the glycidyl methacrylate can smoothly graft with the active groups on the surface of the α-bromo ester modified thermal expansion microspheres in step b, so as to graft the glycidyl methacrylate onto the surface of the α-bromo ester modified thermal expansion microspheres, which enables the glycidyl methacrylate to be firmly connected to the surface of the α-bromo ester modified thermal expansion microspheres, thereby enhancing the stability and durability of the glycidyl methacrylate grafted and modified thermal expansion microspheres. In step b, ethyl 2-bromobutyrate can be used as an initiator of the ATRP reaction to start the grafting reaction of the glycidyl methacrylate by forming an active species with the copper catalyst.

[0052] Step b of the preparation method of the glycidyl methacrylate grafted and modified thermal expansion microspheres further comprises:

[0053] After the reaction is stopped after 25-50 min, the stirring is stopped, the reaction solution is centrifuged and separated, and the solid product is collected, washed with acetic acid to remove unreacted substances and residual reagents, to obtain the glycidyl methacrylate grafted and modified thermal expansion microspheres.

[0054] As a specific embodiment of the thermal expansion material described above, the α-bromo ester modified thermal expansion microspheres are obtained by reacting 2-bromoisobutyryl bromide with the hydroxyl functional groups on the surface and / or inside of the hydroxyl functional thermal expansion microspheres, using 2-bromoisobutyryl bromide, hydroxyl functional thermal expansion microspheres, triethylamine and 4-(dimethylamino)pyridine as raw materials;

[0055] The mass ratio of 2-bromoisobutyryl bromide, hydroxyl functional thermal expansion microspheres, triethylamine and 4-(dimethylamino)pyridine is 20-25:10-15:10-15:0.01-0.03, and the reaction is carried out at -5 to 0℃ for 2-3h.

[0056] As a specific embodiment of the thermal expansion material described above, the α-bromo ester modified thermal expansion microspheres are obtained by using a preparation method comprising the following specific steps:

[0057] The 2-bromoisobutyryl bromide is added to triethylamine and the reaction is stirred at a temperature of -5 to 0°C; then the hydroxyl-functionalized thermally expandable microspheres and 4-(dimethylamino)pyridine are slowly added and the reaction is continuously stirred for 2-3h to ensure that the reaction is fully carried out, and the α-bromo ester-modified thermally expandable microspheres are obtained after the reaction is completed.

[0058] The method for preparing the α-bromo ester-modified thermally expandable microspheres according to the present application further comprises: after the reaction is completed, the solid microspheres are separated from the solution by centrifugation, and finally the separated microspheres are washed and treated with a drying agent to remove the solvent, thereby obtaining the α-bromo ester-modified thermally expandable microspheres.

[0059] The method for preparing the α-bromo ester-modified thermally expandable microspheres according to the present application needs to be carried out under stirring, and the present application does not make specific requirements for the rotation speed of the stirring, which can be reasonably adjusted according to the actual operation needs. For example, in some embodiments of the present application, the rotation speed of the stirring is 10 rpm.

[0060] In the method for preparing the α-bromo ester-modified thermally expandable microspheres according to the present application, the hydroxyl-functionalized thermally expandable microspheres are the carrier of the reaction, which provides a reaction site on the surface or inside thereof, so as to facilitate the reaction between the α-bromo ester modifier, i.e. 2-bromoisobutyryl bromide, and the microspheres. The triethylamine as the base catalyst can promote the reaction between the α-bromo ester modifier and the hydroxyl functional groups on the surface or inside of the microspheres. In this process, the triethylamine can increase the reaction rate and promote the formation of the product. In addition, the triethylamine can also play the role of a solvent, which helps to dissolve the reactants and promote the reaction. At the same time, the 4-(dimethylamino)pyridine can also act as a base catalyst to further promote the reaction between the α-bromo ester modifier and the hydroxyl functional groups on the surface or inside of the microspheres, thereby helping to increase the reaction rate and promote the formation of the product.

[0061] As a specific embodiment of the thermally expandable material according to the present application, the hydroxyl-functionalized thermally expandable microspheres used for preparing the α-bromo ester-modified thermally expandable microspheres are the same as the hydroxyl-functionalized thermally expandable microspheres used for preparing the thiophene ester copolymer grafted thermally expandable microspheres, which are also obtained by a polymerization reaction using acrylonitrile, methacrylonitrile and 2-hydroxyethyl methacrylate as raw materials.

[0062] Among them, the amounts of acrylonitrile, methacrylonitrile and 2-hydroxyethyl methacrylate are 40-60%, 30-40% and 10-20%, respectively, based on 100% of the total weight of the raw materials, and the polymerization reaction is carried out at 50-60°C for 2-3h.

[0063] As a specific embodiment of the above-mentioned heat-expandable material of the present application, the crosslinked heat-expandable core-shell microspheres of cinnamyl cyanide and diethyl fumarate are prepared by a reaction of raw materials, wherein the raw materials include:

[0064] Continuous phase: sodium chloride, colloidal silica suspension, diethanolamine aqueous solution and gelatin aqueous solution;

[0065] Dispersed phase: acrylonitrile, methacrylonitrile, methacrylic acid, cinnamyl cyanide and diethyl fumarate;

[0066] Foaming agent;

[0067] Crosslinking agent;

[0068] and initiator, and the mass ratio of the above reactants is 90-100:10-15:1-3:30-40:5-8:10-15:15-20:0.1-0.3:0.4-0.8:0.1-0.5:1-3:0.01-0.03;

[0069] Wherein, the reaction conditions include: temperature is 50-70℃, pressure is 0.1-0.5MPa and reaction time is 10-15h.

[0070] As a specific embodiment of the above-mentioned heat-expandable material of the present application, the mass concentration of the colloidal silica suspension is 20-30%, the mass concentration of the diethanolamine aqueous solution is 5-10%, and the mass concentration of the gelatin aqueous solution is 10-15%.

[0071] As a specific embodiment of the above-mentioned heat-expandable material of the present application, the foaming agent includes sodium dodecyl benzene sulfonate and the like, the crosslinking agent includes 1,4-butanediol dimethacrylate and the like, and the initiator includes azobisisobutyronitrile and the like.

[0072] As a specific embodiment of the above-mentioned heat-expandable material of the present application, the crosslinked heat-expandable core-shell microspheres of cinnamyl cyanide and diethyl fumarate are prepared by a method including the following specific steps:

[0073] Step (a): Dissolve sodium chloride in an appropriate amount of water to obtain a salt aqueous solution with a certain concentration; add colloidal silica suspension, diethanolamine aqueous solution and gelatin aqueous solution to the salt aqueous solution, and mix and stir at room temperature to obtain a uniform continuous phase solution, i.e. the above-mentioned continuous phase;

[0074] Step (b): Add acrylonitrile, methacrylonitrile, methacrylic acid, cinnamyl cyanide and diethyl fumarate to the reaction kettle to form a dispersed phase;

[0075] Step (c): adding a foaming agent, a cross-linking agent and an initiator into the dispersed phase, wherein the foaming agent is used to ensure the surface activity of the microspheres, the cross-linking agent is used for cross-linking reaction and the initiator is used to start the free radical polymerization reaction at a certain temperature; under the action of the initiator, the monomers in the dispersed phase undergo polymerization reaction and form cross-linking structure under the action of the cross-linking agent; meanwhile, the gelatin in the continuous phase gradually gels to form the shell structure of the microspheres, and the colloidal silica plays a supporting role in the microspheres, which helps to stabilize the structure of the microspheres; after the microspheres are formed, the reaction is stopped, and the reaction solution is subjected to proper treatment (such as filtration and washing) to remove unreacted substances and by-products; finally, the microspheres are collected and dried to remove residual moisture to obtain the final cross-linked and heat-expandable core-shell microspheres of cinnamyl cyanide and diethyl fumarate.

[0076] The preparation method of the cross-linked and heat-expandable core-shell microspheres of cinnamyl cyanide and diethyl fumarate described above in the present application needs to be carried out under stirring, and the present application does not make specific requirements for the rotation speed of the stirring and the like, which can be reasonably adjusted according to the actual operation needs on site. For example, in some embodiments of the present application, the rotation speed of the stirring is 2000-4000 rpm.

[0077] In the continuous phase used in the preparation method of the cross-linked and heat-expandable core-shell microspheres of cinnamyl cyanide and diethyl fumarate described above in the present application, sodium chloride can adjust the osmotic pressure of the continuous phase, which helps to control the separation of the water phase and the organic phase in the emulsification process and has a certain influence on the formation of the microspheres; the colloidal silica suspension helps to provide a stable dispersed phase and helps to form the emulsion system, making the emulsification process more stable; diethanolamine itself can participate in the cross-linking reaction as a reaction catalyst, thereby affecting the cross-linking degree and properties of the microspheres; the gelatin can form a skeleton structure inside the microspheres, affecting the pore structure and heat expansion performance of the microspheres.

[0078] In the dispersed phase used in the preparation method of the cross-linked and heat-expandable core-shell microspheres of cinnamyl cyanide and diethyl fumarate described above in the present application, acrylonitrile can participate in the cross-linking reaction of the microspheres and copolymerize or cross-link with cinnamyl cyanide and diethyl fumarate, thereby affecting the structure and properties of the microspheres; methacrylonitrile can also participate in the cross-linking reaction of the microspheres, and its introduction can affect the cross-linking degree, thereby affecting the stability and mechanical properties of the microspheres; cinnamyl cyanide and diethyl fumarate are reaction monomer cross-linking agents, which can cross-link with other monomers through chemical reaction, thereby forming a three-dimensional network structure of the microspheres and improving the stability and mechanical strength of the microspheres.

[0079] In the preparation method of the cinnamyl nitrile and diethyl fumarate cross-linked thermal expansion core-shell microspheres described above, the presence of a surfactant / foaming agent, such as sodium dodecyl benzene sulfonate, can improve the stability of the microspheres, reduce the agglomeration and sedimentation of the microspheres, and ensure the dispersibility and stability of the microspheres; the cross-linking agent, such as 1,4-butanediol dimethacrylate, contains two different functional groups, i.e., hydroxyl and methacrylate groups, which makes it can be used as a cross-linking agent or modifier. In the preparation process of the thermal expansion microspheres, the addition of the cross-linking agent can not only ensure that the formed shell polymer has good thermoplasticity at the expansion temperature, but also increase the material strength of the shell polymer in the high-elastic state and viscous flow state, thereby improving the expansion performance and heat resistance of the microspheres; the initiator, such as azobisisobutyronitrile, usually decomposes to generate free radicals at high temperatures. In the preparation of cross-linked thermal expansion microspheres, azobisisobutyronitrile introduces free radicals by initiating polymerization reactions, thereby promoting the progress of cross-linking reactions. This cross-linking reaction usually involves the formation of chemical bonds between two or more monomers, thereby forming a network structure in the microspheres.

[0080] The thermal expansion material provided by the present application includes any two or three of the following: oxidized polymer grafted 3-alkyl thiophene modified thermal expansion microspheres, glycidyl methacrylate grafted modified thermal expansion microspheres, and cinnamyl nitrile and diethyl fumarate cross-linked thermal expansion core-shell microspheres; wherein, for the oxidized polymer grafted 3-alkyl thiophene modified thermal expansion microspheres, due to the modification of the oxidized polymer grafted 3-alkyl thiophene, the thermal expansion microspheres have good chemical stability and thermal stability, and can maintain their structure and properties at high temperatures, providing long-term stable support for the resin.

[0081] The glycidyl methacrylate grafted modified thermal expansion microspheres may have certain elasticity and flexibility, can absorb part of the stress when the resin shrinks, reduce the degree of resin shrinkage, thereby reducing the problems caused by shrinkage. The glycidyl methacrylate grafted modified thermal expansion microspheres may also have good thermal expansion, can rapidly expand and fill the voids in the resin when heated, thereby effectively reducing the internal stress and cracks caused by resin shrinkage.

[0082] For the cinnamyl nitrile and diethyl fumarate cross-linked thermal expansion core-shell microspheres, due to the cross-linking effect of cinnamyl nitrile and diethyl fumarate, the thermal expansion microspheres may have good high-temperature stability, can maintain structural integrity at high temperatures, and provide long-term stable support for the resin. The cross-linked structure also endows the thermal expansion microspheres with good chemical stability, allowing them to remain stable in different chemical environments and not easily dissolve or react.

[0083] The present application does not make specific requirements for the preparation method of the thermal expansion material, and any two or three of the modified thermal expansion microspheres of 3-alkyl thiophene by oxidative polymerization grafting, the thermal expansion microspheres of glycidyl methacrylate by grafting modification, and the thermal expansion core-shell microspheres of cinnamaldehyde and diethyl fumarate by crosslinking can be simply mixed to obtain the thermal expansion material.

[0084] In another aspect, the present application also provides a resin liquid bridge plug, wherein the resin liquid bridge plug comprises the thermal expansion material described above.

[0085] In yet another aspect, the present application also provides a deep shale gas wellbore pressure-bearing plugging method, wherein the deep shale gas wellbore pressure-bearing plugging method utilizes the resin liquid bridge plug described above. The thermal expansion material provided by the present application has good compatibility with the resin liquid bridge plug, can be uniformly dispersed in the resin without agglomeration or sedimentation, and can effectively inhibit the shrinkage of the resin after solidification by heat expansion. The use of the resin liquid bridge plug containing the thermal expansion material for deep shale gas wellbore pressure-bearing plugging can enhance the sealing strength of the wellbore pressure-bearing plugging liquid bridge plug, thereby effectively improving the pressure-bearing capacity of the liquid bridge plug required for deep shale gas wellbore plugging, and can be used for anti-shrinkage of deep shale gas liquid bridge plug temporary plugging, thereby improving the adhesion effect of the liquid bridge plug and the wellbore wall surface.

[0086] Compared with the prior art, the present application can achieve the following beneficial technical effects:

[0087] The thermal expansion material provided by the present application has excellent compatibility and can be uniformly and effectively dispersed in epoxy resin glue. This compatibility ensures that it does not react adversely or separate with the epoxy resin glue during mixing and curing, thereby ensuring the overall performance and stability of the cured material. In addition, good compatibility also means that it can be used with other commonly used additives, aids and fillers, etc. to meet different engineering needs. This makes the thermal expansion material provided by the present application more flexible and convenient in actual application.

[0088] The thermal expansion material provided by the present application has significant thermal expansion properties. Under high temperature conditions, this material can effectively inhibit the shrinkage of the resin, thereby maintaining the volume stability and integrity of the cured material. In addition, the strong thermal expansion properties make the material more adaptable to high temperature environments and pressure changes. Whether it is high temperature fracturing in downhole operations or plugging construction, this material can exhibit excellent anti-shrinkage performance, ensuring the durability and reliability of the plugging effect. By controlling the types and contents of thermal expansion particles, the thermal expansion performance of the material can be further adjusted to meet the needs of different engineering conditions. This adjustability makes the thermal expansion material provided by the present application have a wider range of applications and higher practical value in actual application. DETAILED DESCRIPTION

[0089] It has to be understood that the term "comprising" as well as any of its synonyms such as including, comprising, encompassing etc., when used in the present specification and in the following claims, are taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0090] The ranges disclosed herein are given in their broadest form. They can be narrower, i.e. one or more lower limits and one or more upper limits. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundaries of a particular range. All ranges defined in this way are combinable, i.e. any lower limit can be combined with any upper limit to form a range. For example, where ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 is listed and a maximum range value of 3, 4 and 5 is listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

[0091] In the present application, unless otherwise stated, a numerical range "a-b" indicates a shorthand way of describing a range of combinations of any real number between a and b, wherein a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in the present application, and "0-5" is just a shorthand way of describing these combinations of numbers.

[0092] In the present application, all embodiments and preferred embodiments mentioned in the present application can be combined with each other to form new technical solutions, unless otherwise stated.

[0093] In the present application, all technical features and preferred features mentioned in the present application can be combined with each other to form new technical solutions, unless otherwise stated.

[0094] In the present application, all steps mentioned in the present application can be performed in sequence or randomly, but preferably in sequence, unless otherwise stated. For example, the method comprises steps (a) and (b) indicates that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method further comprises step (c) indicates that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0095] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in combination with the accompanying drawings and examples. The examples described below are part of the examples of the present application, but not all the examples, and are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application. If no specific conditions are indicated in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If no manufacturer of the reagents or instruments is indicated, it is a conventional product that can be obtained by market purchase.

[0096] Example 1

[0097] The present example provides a thermal expansion material, which comprises 50% of oxidatively polymerized grafted 3-alkylthiophene modified thermal expansion microspheres and 50% of glycidyl methacrylate grafted modified thermal expansion microspheres, based on 100% of the total weight of the thermal expansion material, and the average particle sizes of the oxidatively polymerized grafted 3-alkylthiophene modified thermal expansion microspheres and the glycidyl methacrylate grafted modified thermal expansion microspheres are about 250 nm and 150 nm, respectively;

[0098] In the present example, the alkyl group in the oxidatively polymerized grafted 3-alkylthiophene modified thermal expansion microspheres is n-decyl;

[0099] In the present example, the oxidatively polymerized grafted 3-alkylthiophene modified thermal expansion microspheres are prepared by a preparation method comprising the following specific steps:

[0100] Preparation of hydroxyl-functionalized thermal expansion microspheres:

[0101] Step (1): According to the target ratio of 40%, 40% and 20% of acrylonitrile, methacrylonitrile and 2-hydroxyethyl methacrylate, respectively, based on 100% of the total weight of the raw materials, acrylonitrile and 2-hydroxyethyl methacrylate are first mixed, and toluene is added (the volume to mass ratio of toluene to the mixture of acrylonitrile and 2-hydroxyethyl methacrylate is 30:1, wherein the units of volume and mass are mL and g, respectively) to adjust the viscosity and concentration of the reaction system;

[0102] Step (2): After adding methacrylonitrile to the mixed solution obtained in step (1), it is uniformly dispersed in the mixed solution by stirring at a speed of 2000 r / min;

[0103] Step (3): 0.02 wt% (calculated based on the total weight of acrylonitrile, methacrylonitrile and 2-hydroxyethyl methacrylate) of ammonium persulfate initiator was added to the mixed solution obtained in step (2) to trigger the polymerization of monomers, and the monomers were reacted at 50°C for 3h;

[0104] Step (4): After the reaction was completed, the polymer microspheres obtained after the reaction were washed to remove residual reactants and other impurities, and then dried to obtain the final product to obtain the hydroxyl-functionalized heat-expandable microspheres.

[0105] Preparation of thienyl ester copolymer grafted heat-expandable microspheres:

[0106] Step 1): The hydroxyl-functionalized heat-expandable microspheres and dimethylformamide (its volume is 30 times the total mass of the reactants, wherein the units of volume and mass are mL and g, respectively) were mixed in a reaction vessel and mixed uniformly by stirring for 10 min;

[0107] Step 2): Under stirring, dimethylaminopyridine was slowly added dropwise into the reaction vessel, and stirred for 1h at a specified temperature and stirring speed to mix uniformly;

[0108] Step 3): Under stirring, 2-(thiophene-3-yl)acetyl chloride was added to the reaction vessel to react with the hydroxyl-functionalized heat-expandable microspheres for 10 min;

[0109] Step 4): Under stirring, triethylamine was added to the reaction vessel and reacted for 30 min. After the reaction was completed, the product was sequentially filtered, washed with acetone, and dried to obtain the thienyl ester copolymer grafted heat-expandable microspheres;

[0110] wherein the mass ratio of the hydroxyl-functionalized heat-expandable microspheres, triethylamine, dimethylaminopyridine and 2-(thiophene-3-yl)acetyl chloride is 0.8:1:0.01:1.2, and the temperature in steps 1)-4) is controlled at 25°C and the stirring speed is controlled at 10000 rpm.

[0111] Preparation of oxidatively polymerized 3-alkylthiophene grafted heat-expandable microspheres:

[0112] Step 1: Thienyl ester copolymer grafted heat-expandable microspheres and 3-n-decylthiophene were added to dichloromethane (its volume is 30 times the total mass of the reactants, wherein the units of volume and mass are mL and g, respectively) at a mass ratio of 90:1 and mixed uniformly by stirring for 0.5h;

[0113] Step 2: Add 0.02 wt% (calculated based on the total mass of the reactants) of ammonium persulfate initiator to the mixture obtained in Step 1 to allow 3-alkylthiophene to undergo oxidative polymerization at 25°C for 1 hour to form an oxidative polymer. Introduce the oxidative polymer onto the thiophene ester copolymer grafted modified thermal expansion microspheres. The obtained microsphere particles are then filtered, washed with acetone, and dried to remove residual solvents and impurities, resulting in dried modified microspheres, namely the oxidatively polymerized grafted 3-alkylthiophene modified thermal expansion microspheres.

[0114] The glycidyl methacrylate grafted modified thermally expandable microspheres are prepared using a method comprising the following specific steps:

[0115] Preparation of α-bromoester modified thermally expandable microspheres:

[0116] 2-Bromoisobutyryl bromide was added to triethylamine and stirred (10 rpm) at 0°C. Then, hydroxyl-functionalized thermally expandable microspheres [prepared by the same method as steps (1)-(4)) above] and 4-(dimethylamino)pyridine were slowly added and stirred (10 rpm) for 2 h to ensure that the reaction was complete. After the reaction was completed, the solid microspheres were separated from the solution by centrifugation. Finally, the separated microspheres were washed and treated with a desiccant to remove the solvent, and the α-bromoester modified thermally expandable microspheres were obtained.

[0117] The mass ratio of 2-bromoisobutyryl bromide, hydroxyl-functionalized thermally expandable microspheres, triethylamine, and 4-(dimethylamino)pyridine is 20:10:10:0.01.

[0118] Preparation of glycidyl methacrylate grafted modified thermally expandable microspheres:

[0119] Step a: CuBr2 and N,N,N',N”,N”-pentamethyldiethyltriamine were mixed in acetonitrile (the volume of which was 30 times the total mass of the reactants, where the units of volume and mass were mL and g, respectively) to prepare a copper catalyst.

[0120] Step b: The α-bromoester-modified thermally expandable microspheres were suspended in toluene (solvent), and then glycidyl methacrylate, copper catalyst, and ethyl 2-bromobutyrate (initiator) were added. The mixture was stirred at 25°C to carry out the grafting reaction. Ascorbic acid was added as a reducing agent during the grafting reaction to keep the copper catalyst in a reduced state. After the reaction was carried out for 30 min, the stirring was stopped, the reaction solution was centrifuged, the solid product was collected, and the solid product was washed with acetic acid to remove unreacted substances and residual reagents to obtain the glycidyl methacrylate-grafted modified thermally expandable microspheres.

[0121] The mass ratio of the alpha-bromide ester modified thermal expansion microspheres, glycidyl methacrylate, toluene, CuBr2, N,N,N',N",N"-pentamethyldiethyltriamine, ethyl 2-bromobutyrate and ascorbic acid is 1:10:8:0.001:0.02:0.1:0.015.

[0122] Embodiment 2

[0123] The embodiment provides a thermal expansion material, which comprises 50% of oxidized polymer grafted 3-alkyl thiophene modified thermal expansion microspheres and 50% of cinnamyl cyanide and fumaric acid diethyl ester cross-linked thermal expansion core-shell microspheres, and the average particle sizes of the oxidized polymer grafted 3-alkyl thiophene modified thermal expansion microspheres and the cinnamyl cyanide and fumaric acid diethyl ester cross-linked thermal expansion core-shell microspheres are about 250 nm and 300 nm respectively, with the total weight of the thermal expansion material being 100%;

[0124] The preparation method of the oxidized polymer grafted 3-alkyl thiophene modified thermal expansion microspheres is completely same as that in Embodiment 1.

[0125] The cinnamyl cyanide and fumaric acid diethyl ester cross-linked thermal expansion core-shell microspheres are prepared by a preparation method comprising the following specific steps:

[0126] Step (a): sodium chloride is dissolved in an appropriate amount of water to obtain a salt aqueous solution with a certain concentration; colloidal silica suspension (mass concentration of 30%), diethanolamine aqueous solution (mass concentration of 10%) and gelatin aqueous solution (mass concentration of 10%) are added into the salt aqueous solution, and the mixture is fully mixed and stirred at room temperature to obtain a uniform continuous phase solution, namely the continuous phase;

[0127] Step (b): acrylonitrile, methacrylonitrile, methacrylic acid, cinnamyl cyanide and fumaric acid diethyl ester are added into a reaction kettle to form a dispersed phase;

[0128] Step (c): sodium dodecylbenzenesulfonate is added into the dispersed phase to ensure the surface activity of the microspheres, 1,4-butanediol dimethacrylate is added into the dispersed phase to be used for cross-linking reaction, and azobisisobutyronitrile is added into the dispersed phase to start the free radical polymerization reaction at a certain temperature; under the action of azobisisobutyronitrile, the monomers in the dispersed phase are subjected to polymerization reaction and form a cross-linked structure under the action of the cross-linking agent; meanwhile, the gelatin in the continuous phase is gradually gelled to form the shell structure of the microspheres, and the colloidal silica in the microspheres plays a supporting role and helps to stabilize the structure of the microspheres; after the microspheres are formed, the reaction is stopped, and the reaction solution is subjected to appropriate treatment (such as filtration and washing) to remove the unreacted substances and by-products; finally, the microspheres are collected and dried to remove the residual moisture to obtain the final cinnamyl cyanide and fumaric acid diethyl ester cross-linked thermal expansion core-shell microspheres;

[0129] The mass ratio of sodium chloride, colloidal silica suspension, diethanolamine aqueous solution, gelatin aqueous solution, acrylonitrile, methacrylonitrile, methacrylic acid, cinnamaldehyde, diethyl fumarate, sodium dodecylbenzenesulfonate, 1,4-butanediol dimethacrylate and azobisisobutyronitrile is 100:10:1:30:5:10:15:0.1:0.4:0.2:1:0.01;

[0130] The conditions of the polymerization reaction are that the temperature is 60℃, the pressure is 0.3MPa and the reaction time is 10h, and the stirring speed in steps (a)-(c) is 2000rpm.

[0131] Example 3

[0132] The present example provides a thermal expansion material, which comprises 50% of glycidyl methacrylate grafted thermal expansion microspheres and 50% of cinnamaldehyde and diethyl fumarate crosslinked thermal expansion core-shell microspheres, based on the total weight of the thermal expansion material being 100%, and the average particle sizes of the glycidyl methacrylate grafted thermal expansion microspheres and the cinnamaldehyde and diethyl fumarate crosslinked thermal expansion core-shell microspheres are about 150nm and 300nm, respectively;

[0133] The preparation method of the glycidyl methacrylate grafted thermal expansion microspheres is completely the same as that of the glycidyl methacrylate grafted thermal expansion microspheres used in Example 1; and the preparation method of the cinnamaldehyde and diethyl fumarate crosslinked thermal expansion core-shell microspheres is completely the same as that of the cinnamaldehyde and diethyl fumarate crosslinked thermal expansion core-shell microspheres used in Example 2.

[0134] Example 4

[0135] The present example provides a thermal expansion material, which comprises 34% of oxidized polymerization grafted 3-alkyl thiophene modified thermal expansion microspheres, 33% of glycidyl methacrylate grafted thermal expansion microspheres and 33% of cinnamaldehyde and diethyl fumarate crosslinked thermal expansion core-shell microspheres, based on the total weight of the thermal expansion material being 100%, and the average particle sizes of the oxidized polymerization grafted 3-alkyl thiophene modified thermal expansion microspheres, the glycidyl methacrylate grafted thermal expansion microspheres and the cinnamaldehyde and diethyl fumarate crosslinked thermal expansion core-shell microspheres are about 250nm, 150nm and 300nm, respectively;

[0136] The preparation method of the oxidized polymerization grafted 3-alkyl thiophene modified thermal expansion microspheres and the glycidyl methacrylate grafted thermal expansion microspheres is completely the same as that of the oxidized polymerization grafted 3-alkyl thiophene modified thermal expansion microspheres and the glycidyl methacrylate grafted thermal expansion microspheres used in Example 1, respectively; and the preparation method of the cinnamaldehyde and diethyl fumarate crosslinked thermal expansion core-shell microspheres is completely the same as that of the cinnamaldehyde and diethyl fumarate crosslinked thermal expansion core-shell microspheres used in Example 2.

[0137] Example 1-1

[0138] The present embodiment provides a resin-based liquid bridge plug, wherein the resin-based liquid bridge plug comprises an epoxy resin, a polyamide curing agent, and the thermal expansion material provided in Embodiment 1.

[0139] The mass ratio of the epoxy resin and the polyamide curing agent is 1:1, and the amount of the thermal expansion material provided in Embodiment 1 is 5% based on the total weight of the epoxy resin and the polyamide curing agent being 100%.

[0140] Embodiment 2-1

[0141] The present embodiment provides a resin-based liquid bridge plug, wherein the resin-based liquid bridge plug comprises an epoxy resin, a polyamide curing agent, and the thermal expansion material provided in Embodiment 2.

[0142] The mass ratio of the epoxy resin and the polyamide curing agent is 1:1, and the amount of the thermal expansion material provided in Embodiment 2 is 5% based on the total weight of the epoxy resin and the polyamide curing agent being 100%.

[0143] Embodiment 3-1

[0144] The present embodiment provides a resin-based liquid bridge plug, wherein the resin-based liquid bridge plug comprises an epoxy resin, a polyamide curing agent, and the thermal expansion material provided in Embodiment 3.

[0145] The mass ratio of the epoxy resin and the polyamide curing agent is 1:1, and the amount of the thermal expansion material provided in Embodiment 3 is 5% based on the total weight of the epoxy resin and the polyamide curing agent being 100%.

[0146] Embodiment 4-1

[0147] The present embodiment provides a resin-based liquid bridge plug, wherein the resin-based liquid bridge plug comprises an epoxy resin, a polyamide curing agent, and the thermal expansion material provided in Embodiment 4.

[0148] The mass ratio of the epoxy resin and the polyamide curing agent is 1:1, and the amount of the thermal expansion material provided in Embodiment 4 is 5% based on the total weight of the epoxy resin and the polyamide curing agent being 100%.

[0149] Comparative Example 1

[0150] The present comparative example provides a resin-based liquid bridge plug, wherein the resin-based liquid bridge plug comprises an epoxy resin and a polyamide curing agent, and the mass ratio of the two is 1:1.

[0151] Comparative Example 1

[0152] The comparative example provides a resin-based liquid bridge plug, wherein the resin-based liquid bridge plug comprises an epoxy resin, a polyamide curing agent, and the oxidatively polymerized grafted 3-alkyl thiophene modified thermal expansion microspheres provided in Example 1.

[0153] The mass ratio of the epoxy resin and the polyamide curing agent is 1:1, and the amount of the oxidatively polymerized grafted 3-alkyl thiophene modified thermal expansion microspheres is 5% based on the total weight of the epoxy resin and the polyamide curing agent being 100%.

[0154] Comparative Example 2

[0155] The comparative example provides a resin-based liquid bridge plug, wherein the resin-based liquid bridge plug comprises an epoxy resin, a polyamide curing agent, and the glycidyl methacrylate grafted modified thermal expansion microspheres provided in Example 1.

[0156] The mass ratio of the epoxy resin and the polyamide curing agent is 1:1, and the amount of the glycidyl methacrylate grafted modified thermal expansion microspheres is 5% based on the total weight of the epoxy resin and the polyamide curing agent being 100%.

[0157] Comparative Example 3

[0158] The comparative example provides a resin-based liquid bridge plug, wherein the resin-based liquid bridge plug comprises an epoxy resin, a polyamide curing agent, and the cinnamaldehyde and diethyl fumarate crosslinked thermal expansion core-shell microspheres provided in Example 2.

[0159] The mass ratio of the epoxy resin and the polyamide curing agent is 1:1, and the amount of the cinnamaldehyde and diethyl fumarate crosslinked thermal expansion core-shell microspheres is 5% based on the total weight of the epoxy resin and the polyamide curing agent being 100%.

[0160] Test Example 1

[0161] The resin-based liquid bridge plugs provided in Examples 1-1 to 4-1 and Comparative Examples 1 to 3 are respectively evaluated for expansion performance, including:

[0162] The same amount of resin-based liquid bridge plugs are taken and cured under high temperature conditions (100°C, 130°C, and 160°C, respectively), and the volume change rates of the cured resin-based liquid bridge plugs relative to the resin-based liquid bridge plug provided in Comparative Example 1 are tested.

[0163] The volume change rates of the cured resin-based liquid bridge plugs relative to the resin-based liquid bridge plug provided in Comparative Example 1, i.e., the volume expansion rates of the cured resin-based liquid bridge plugs, obtained in this test example are shown in Table 1 below.

[0164] Table 1 Volume expansion rates of the cured resin-based liquid bridge plugs

[0165] Item % Swell at 100°C % Swell at 130°C % Swell at 160°C Example 1 24.5 28.1 31.4 Example 2 18.6 25.7 27.6 Example 3 34.1 39.4 42.9 Example 4 35.3 41.5 45.1 Comparative Example 1 5.4 7.5 8.9 Comparative Example 2 2.1 3.7 5.2 Comparative Example 3 6.4 8.2 10.4

[0166] The resin-based liquid bridge plugs provided by Comparative Examples 1-3 respectively only include one of the oxidatively polymerized grafted 3-alkyl thiophene modified thermally expandable microspheres, the glycidyl methacrylate grafted modified thermally expandable microspheres and the cinnamaldehyde and diethyl fumarate crosslinked thermally expandable core-shell microspheres, while the resin-based liquid bridge plugs provided by Examples 1-4 of the present application respectively combine any two or three of the oxidatively polymerized grafted 3-alkyl thiophene modified thermally expandable microspheres, the glycidyl methacrylate grafted modified thermally expandable microspheres and the cinnamaldehyde and diethyl fumarate crosslinked thermally expandable core-shell microspheres as the thermally expandable material. As can be seen from Table 1 above, compared with the resin-based liquid bridge plugs provided by Comparative Examples 1-3, the resin-based liquid bridge plugs provided by Examples 1-4 of the present application all have higher expansion rates under different high temperature conditions, indicating that the thermally expandable materials contained therein have excellent thermal expansion properties. At the same time, the experimental data in the comparative examples and the comparative examples can also prove that the present application combines any two or three of the oxidatively polymerized grafted 3-alkyl thiophene modified thermally expandable microspheres, the glycidyl methacrylate grafted modified thermally expandable microspheres and the cinnamaldehyde and diethyl fumarate crosslinked thermally expandable core-shell microspheres as the thermally expandable material, and there is a synergistic effect between the combined microspheres, which can significantly improve the thermal expansion properties.

[0167] In addition, the thermally expandable materials provided by the examples of the present application can be well doped in epoxy resin as an effective component in the resin-based liquid bridge plug, which indicates that it has good resin compatibility.

[0168] The above is only a specific embodiment of the present application, which cannot limit the scope of the application. Therefore, the replacement of equivalent components or equivalent changes and modifications made within the scope of the present patent protection should still fall within the scope of the present patent. In addition, the technical features in the present application can be freely combined with each other, between technical features, between technical features and technical inventions, and between technical inventions.

Claims

1. A thermal expansion material, characterized in that, The thermal expansion material includes any two or a combination of three of the following: oxidatively polymerized 3-alkylthiophene-modified thermal expansion microspheres, glycidyl methacrylate-grafted thermal expansion microspheres, and cinnamonitrile and diethyl fumarate-crosslinked thermal expansion core-shell microspheres. Based on the total weight of the thermal expansion material as 100%, when it includes oxidatively polymerized grafted 3-alkylthiophene modified thermal expansion microspheres, glycidyl methacrylate grafted modified thermal expansion microspheres, and cinnamonitrile and diethyl fumarate crosslinked thermal expansion core-shell microspheres, the contents of the three are 15-55%, 25-75%, and 30-65%, respectively.

2. The thermal expansion material according to claim 1, characterized in that, The particle size distributions of the oxidatively polymerized 3-alkylthiophene-modified thermally expandable microspheres, the glycidyl methacrylate-grafted thermally expandable microspheres, and the cinnamonitrile and diethyl fumarate-crosslinked thermally expandable core-shell microspheres were 100-500 μm, respectively.

3. The thermal expansion material according to claim 1, characterized in that, In the oxidatively polymerized grafted 3-alkylthiophene modified thermally expandable microspheres, the alkyl group includes an ortho-alkyl group with 10-15 carbon atoms.

4. The thermal expansion material according to any one of claims 1-3, characterized in that, The oxidatively polymerized 3-alkylthiophene-modified thermally expandable microspheres are obtained by oxidative polymerization reaction using thiophene ester copolymer-grafted modified thermally expandable microspheres and 3-alkylthiophene as raw materials. The mass ratio of the thiophene ester copolymer grafted modified thermal expansion microspheres to 3-alkylthiophene is 90-110:1, and the oxidative polymerization reaction is carried out at 25-35℃ for 0.5-1.5h.

5. The thermal expansion material according to claim 4, characterized in that, The thiophene ester copolymer grafted modified thermal expansion microspheres are obtained by reacting hydroxyl-functionalized thermal expansion microspheres, triethylamine, dimethylaminopyridine, and 2-(thiophene-3-yl)acetyl chloride on the surface of hydroxyl-functionalized thermal expansion microspheres. The mass ratio of hydroxyl-functionalized thermally expandable microspheres, triethylamine, dimethylaminopyridine, and 2-(thiophen-3-yl)acetyl chloride is 0.8-1:0.8-1.2:0.01-0.03:1.0-1.2, and the reaction temperature is 25-35℃.

6. The thermal expansion material according to claim 5, characterized in that, The hydroxyl-functionalized thermally expandable microspheres are obtained by polymerization reaction using acrylonitrile, methacrylonitrile, and 2-hydroxyethyl methacrylate as raw materials. In this process, based on the total weight of the raw materials (100%), the amounts of acrylonitrile, methacrylonitrile, and 2-hydroxyethyl methacrylate are 40-60%, 30-40%, and 10-20%, respectively, and the polymerization reaction is carried out at 50-60°C for 2-3 hours.

7. The thermal expansion material according to claim 1 or 2, characterized in that, The glycidyl methacrylate grafted modified thermal expansion microspheres are obtained by grafting glycidyl methacrylate onto the surface of α-bromoester modified thermal expansion microspheres, glycidyl methacrylate, toluene, CuBr2, N,N,N',N”,N”-pentamethyldiethyltriamine, ethyl 2-bromobutyrate and ascorbic acid as raw materials, and by grafting glycidyl methacrylate onto the surface of α-bromoester modified thermal expansion microspheres through a grafting reaction. The mass ratio of α-bromoester-modified thermally expandable microspheres, glycidyl methacrylate, toluene, CuBr2, N,N,N',N”,N”-pentamethyldiethyltriamine, ethyl 2-bromobutyrate, and ascorbic acid was 1-1.5:10-13:8-10:0.001-0.003:0.015-0.03:0.08-0.1:0.015-0.018, and the grafting reaction was carried out at 25-35℃ for 25-50 min.

8. The thermal expansion material according to claim 7, characterized in that, The α-bromoester modified thermal expansion microspheres are obtained by reacting 2-bromoisobutyryl bromide, hydroxyl-functionalized thermal expansion microspheres, triethylamine and 4-(dimethylamino)pyridine as raw materials with hydroxyl functional groups on the surface and / or inside the hydroxyl functional groups of the thermal expansion microspheres. The mass ratio of 2-bromoisobutyryl bromide, hydroxyl-functionalized thermally expandable microspheres, triethylamine, and 4-(dimethylamino)pyridine is 20-25:10-15:10-15:0.01-0.03, and the reaction is carried out at -5 to 0°C for 2-3 hours.

9. The thermal expansion material according to claim 8, characterized in that, The hydroxyl-functionalized thermally expandable microspheres are obtained by polymerization reaction using acrylonitrile, methacrylonitrile, and 2-hydroxyethyl methacrylate as raw materials. In this process, based on the total weight of the raw materials (100%), the amounts of acrylonitrile, methacrylonitrile, and 2-hydroxyethyl methacrylate are 40-60%, 30-40%, and 10-20%, respectively, and the polymerization reaction is carried out at 50-60°C for 2-3 hours.

10. The thermal expansion material according to claim 1 or 2, characterized in that, The cross-linked thermally expandable core-shell microspheres of cinnamonitrile and diethyl fumarate are prepared by reaction from the following raw materials, wherein the raw materials include: Continuous phase: sodium chloride, colloidal silica suspension, diethanolamine aqueous solution and gelatin aqueous solution; Dispersed phase: Acrylonitrile, methacrylonitrile, methacrylic acid, cinnamonitrile and diethyl fumarate; Foaming agent; Crosslinking agent; And an initiator, wherein the mass ratio of the above reactants is 90-100:10-15:1-3:30-40:5-8:10-15:15-20:0.1-0.3:0.4-0.8:0.1-0.5:1-3:0.01-0.03; The reaction conditions include a temperature of 50-70℃, a pressure of 0.1-0.5MPa, and a reaction time of 10-15h.

11. The thermal expansion material according to claim 10, characterized in that, The colloidal silica suspension has a mass concentration of 20-30%, the diethanolamine aqueous solution has a mass concentration of 5-10%, and the gelatin aqueous solution has a mass concentration of 10-15%.

12. The thermal expansion material according to claim 10, characterized in that, The foaming agent includes sodium dodecylbenzenesulfonate, the crosslinking agent includes 1,4-butanediol dimethacrylate, and the initiator includes azobisisobutyronitrile.

13. A resin-based liquid bridge plug, characterized in that, The resin-based liquid bridge plug comprises the thermally expanding material according to any one of claims 1-12.

14. A method for pressure sealing of deep shale gas wellbores, characterized in that, The deep shale gas wellbore pressure sealing method utilizes the resin-based liquid bridge plug as described in claim 13.