Epoxy silicon-based composite resin for oil and gas field plugging and preparation method thereof

Abstract

The invention relates to the technical field of oil and gas field plugging materials, and discloses epoxy silicon-based composite resin for oil and gas field plugging and a preparation method thereof. The composite resin comprises the following components in parts by mass: 100 parts of mixed epoxy resin, 5-50 parts of octa-epoxy polyhedral oligomeric silsesquioxane, 80-120 parts of a curing agent, 5-25 parts of a diluent, 0.1-3 parts of a curing accelerator and 0.5-3 parts of a coupling agent, the mixed epoxy resin is a mixture of bisphenol A epoxy resin and alicyclic epoxy resin, and the alicyclic epoxy resin accounts for 10-60% of the mass of the mixed epoxy resin. According to the composite resin disclosed by the invention, an organic-inorganic hybrid system is introduced, the curing reaction shrinkage rate of a plugging system is reduced, and the composite resin has excellent heat resistance, mechanical property and plugging property.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field plugging materials, and in particular to an epoxy silicon-based composite resin for oil and gas field plugging and a preparation method thereof. Background Art

[0002] As oilfield development deepens, casing leakage becomes more and more serious, becoming one of the main factors restricting stable production and efficient development of oilfields. Long-term plugging of oil, gas and water wells is an important means to improve the development effect of oil and gas fields. However, the existing plugging system has problems such as single performance, poor adaptability and low success rate, which cannot meet the production needs of oilfields.

[0003] Existing cement granular system plugging agents have problems such as low pressure bearing, short effective period, and poor sealing performance outside the pipe. After cement solidifies, the volume shrinks, making it difficult to form a dense solid body, the strength of cement solidified material is low (<8MPa), and the storage effective period is short. In addition, cement is a granular system with poor fluidity, making it difficult to seal the micro gaps in the pipe external channel.

[0004] The resin plugging agent is formulated as a pure liquid phase, insoluble in water and oil, and has a good plugging effect on reservoirs, especially microcracks and microchannels, and is suitable for plugging various leaks. Epoxy resin plugging agents have the advantages of high temperature resistance, impact resistance, high compressive strength, high single plugging rate, and long storage validity period. However, the general epoxy resin plugging volume shrinks to varying degrees during curing, and its volume shrinkage rate is about 5%-10%. During the plugging process, it is easy to produce plugging cracks or interface damage after gelation, thereby reducing the plugging rate.

[0005] Some research on composite plugging materials has been conducted at home and abroad. The patent CN1011517021A applied by Japan DIC Corporation in China discloses a composite resin (ABC) and a curing agent (E), wherein the composite resin is obtained by chemically bonding the neutralized acid-based polymer fragment and the polysiloxane fragment, and then bonding with the condensation product of alkyltrialkoxysilane through Si-O bonds. The obtained resin has an organic siloxane content of up to 46%-50%, and has excellent weather resistance and solvent resistance. However, the hardness measured after coating is only 1-2H. On the one hand, the reason is that the increase in silicon content makes the amount of hard monomers in acrylic resin only 20-27%. On the other hand, during the film formation process, the organic siloxane has a low surface energy and will migrate to the surface of the coating. A large amount of siloxane will cause the destruction of the network structure and affect the performance of the coating.

[0006] Chinese invention patent application CN106833244B grafts organosiloxane and inorganic silica sol on the basis of water-based acrylic resin. The Si-O-Si structure in the organosiloxane has high bond energy and low surface energy, which improves the hardness and water resistance of the hybrid resin. After the carbonyl group in the water-based acrylic resin is neutralized, the hydrophilicity is on the outside during the self-emulsification process in water, wrapping the organosiloxane and inorganic silica sol, preventing the reaction between water and inorganic silica sol, so that the resin can be stored for a long time and the viscosity will not increase. However, the surface energy of organosiloxane is low, which is quite different from the surface energy of the substrate. It is difficult to form a film on unpolished metal, plastic and glass, or shrinkage occurs during the coating process, resulting in uneven thickness and cracks of the coating, affecting the adhesion between the coating and the substrate. In addition, the low cross-linking density of the polymer molecular chain will make the density of the coating poor, resulting in poor impact resistance of the coating.

[0007] Chinese invention patent CN111218264A discloses a resin plugging agent, which is composed of 100 parts of epoxy resin, 10-25 parts of diluent, 2.4-3.0 parts of cross-linking agent, 5-20 parts of toughening agent and 5-20 parts of reinforcing agent, wherein the cross-linking agent is mainly an epoxy ring-opening anionic polymerization imidazole catalyst, the toughening agent is a commonly used toughening agent for plastics, phthalates or nitrile rubber, and the reinforcing agent is an inorganic filler commonly used in epoxy resin. The prepared resin plugging agent has a compressive strength greater than 6MPa and has good plugging effect and stability. However, the compressive strength is relatively low, and the use of inorganic fillers increases the unevenness of the system. The inorganic fillers are easy to agglomerate in fine cracks, reducing the plugging effect.

[0008] Chinese invention patent CN115651616A discloses a high-toughness resin plugging agent and a preparation method, the composition and preparation method of which are as follows: 90-100 parts of resin base liquid and 5-20 parts of diluent are mixed and stirred to obtain a first mixture, 5-20 parts of toughening agent and 5-30 parts of curing agent are mixed into a second mixture, and the two mixtures are mixed and stirred to obtain a resin plugging agent. The resin, curing agent, diluent, and toughening agent are commonly used materials in epoxy resin formulas, and the prepared high-toughness resin plugging agent has good fluidity, toughness, and high strength. However, in the formula system, the general epoxy resin formula has a curing shrinkage problem, which may have a negative impact on the plugging effect.

[0009] For most polymerization reactions, volume shrinkage will occur more or less as the polymerization proceeds. The main reason is that the distance between liquid monomer molecules is the van der Waals distance, while the distance between structural units in the polymer is the covalent bond distance. However, the van der Waals distance is greater than the covalent bond distance, so when the liquid monomer becomes a polymer, the volume shrinks. Adding inorganic fillers to the plugging agent can effectively reduce the shrinkage caused by curing, but there are problems with the dispersion of inorganic fillers in the resin matrix and the penetration of fine cracks. In order to better solve the dispersion problem of inorganic fillers in the organic matrix, introducing an organic-inorganic hybrid system is a better way. The organic-inorganic nanomaterial POSS has a unique molecular structure, and its molecular core is an inorganic silicon oxygen cage structure with good mechanical properties. It may reduce the shrinkage rate of the epoxy resin system and improve the heat resistance. In previous studies, POSS fillers were mostly added to epoxy resin in the form of inorganic powder, with poor dispersion effect, and the superior performance of the organic-inorganic hybrid system was not fully utilized. Summary of the invention

[0010] In order to overcome the shortcomings of the existing epoxy plugging system, such as large curing shrinkage, poor heat resistance and low strength, the present invention provides an epoxy-silicon-based composite resin for oil and gas field plugging with low shrinkage, high temperature resistance and high strength and a preparation method thereof. The technical scheme is as follows: An epoxy silicon-based composite resin for plugging oil and gas fields comprises the following components and their mass parts: 100 parts of mixed epoxy resin, 5-50 parts of octaepoxy cage-type silsesquioxane, 80-120 parts of curing agent, 5-25 parts of diluent, 0.1-3 parts of curing accelerator and 0.5-3 parts of coupling agent.

[0011] Furthermore, the mixed epoxy resin is a mixture of bisphenol A epoxy resin and alicyclic epoxy resin, wherein the alicyclic epoxy resin accounts for 10%-60% of the mass of the mixed epoxy resin.

[0012] Furthermore, the bisphenol A epoxy resin is a liquid bisphenol A epoxy resin, including E-44 type and E-51 type.

[0013] Furthermore, the alicyclic epoxy resin is an epoxy resin containing one or more alicyclic epoxy groups, including 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, namely CER-170 type; 4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester, namely TDE-85 type, and its structural formula is as follows: ; Further, the octa-epoxy cage silsesquioxane is octa-cyclohexane epoxy cage silsesquioxane or octa-(γ-glycidyloxypropyl) cage silsesquioxane, and its structural formula is as follows: .

[0014] Furthermore, the curing agent is one or a mixture of nadic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride and methylhexahydrophthalic anhydride.

[0015] Furthermore, the diluent is one or a mixture of ethylene glycol diglycidyl ether, butanediol diglycidyl ether and hexanediol diglycidyl ether.

[0016] Furthermore, the curing accelerator is a tertiary amine epoxy-anhydride system curing accelerator, including one of benzyldimethylamine, bicyclic amidine, 2,4,6-tris(dimethylaminotoluene)phenol and triethanolamine.

[0017] Furthermore, the coupling agent is a silane coupling agent, which is γ-glycidyloxypropyltrimethoxysilane or 3-aminopropyltriethoxysilane.

[0018] A method for preparing an epoxy-silicon-based composite resin for oil and gas field plugging comprises the following steps: (1) Synthesis of octaepoxy cage-type silsesquioxane; (2) mixing the octaepoxy cage-type silsesquioxane synthesized in step (1) with the mixed epoxy resin, curing agent and diluent for later use; (3) Before going downhole, add curing accelerator and coupling agent.

[0019] Furthermore, the synthesis steps of the octaepoxy cage-type silsesquioxane in step (1) are as follows: isopropanol, toluene and tetramethylammonium hydroxide aqueous solution are added to a container, a mixed solution of toluene and a silane coupling agent is added dropwise under stirring, refluxed, condensed, stirred and hydrolyzed at room temperature, and then heated to carry out a condensation reaction, after separation, saturated brine is added to wash until neutral, and the solvent is removed by distillation under reduced pressure to obtain the octaepoxy cage-type silsesquioxane.

[0020] Compared with the prior art, the present invention mainly has the following beneficial technical effects: 1. The cage-type half siloxane in the present invention has good compatibility with the epoxy resin system and can be well dispersed in the mixed epoxy resin. A certain solvent can be used in the mixing process because a low-viscosity alicyclic epoxy is used in the system and a diluent is added to increase the solvent removal effect without affecting the performance of the cured product.

[0021] 2. The composite resin of the present invention introduces an organic-inorganic hybrid system to reduce the shrinkage rate of the curing reaction of the plugging system. The shrinkage rate of the epoxy plugging system can be less than 2%, and it has good heat resistance and excellent mechanical properties.

[0022] 3. The curing time of the composite resin of the present invention can be conveniently adjusted according to the dosage of the curing accelerator, and the addition of the coupling agent can increase the bonding force between the plugging resin and the inorganic rock and soil layer, and the plugging performance is excellent. DETAILED DESCRIPTION

[0023] In order to clearly illustrate the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments. Example 1

[0024] A method for preparing an epoxy-silicon-based composite resin for plugging oil and gas fields comprises the following steps: (1) Preparation of octa(γ-glycidyloxypropyl) cage-type silsesquioxane: 50 mL of isopropanol, 50 mL of toluene and 20 g of 2% tetramethylammonium hydroxide aqueous solution were added to a three-necked flask equipped with a stirrer, a dropping funnel and a thermometer. A mixed solution of 50 mL of toluene and 55 g of γ-glycidyloxypropyltrimethoxysilane (i.e., coupling agent KH560) was added dropwise using a constant pressure funnel under stirring for a certain period of time. After the addition was completed, the mixture was refluxed and condensed at room temperature and stirred for hydrolysis for 7 hours. After the hydrolysis was complete, the temperature was raised to 80°C. o C for condensation reaction for 1 hour. After the reaction is completed, the reactant is transferred to a separatory funnel, washed with saturated brine until neutral, heated to 65°C, stirred, and distilled under reduced pressure to remove most of the solvent. The resulting solution contains 50g of octa(γ-glycidyloxypropyl) cage-type silsesquioxane. A small amount of residual solvent is to ensure that the octa(γ-glycidyloxypropyl) cage-type silsesquioxane does not agglomerate, reduce the difficulty of dispersion, and ensure uniform mixing.

[0025] (2) Add 90 g of bisphenol A type epoxy resin E-51, 10 g of alicyclic epoxy resin TDE-85, 120 g of curing agent methyl hexahydrophthalic anhydride, and 5 g of diluent 1,4-butanediol diglycidyl ether to the above solution, mix well at room temperature, and remove the remaining solvent in vacuo to obtain 275 g of liquid resin mixture for use.

[0026] (3) Take 275g of the reserved resin mixture, add 0.1g of curing accelerator and 3g of coupling agent, mix well, remove bubbles by vacuum and pour into the mold or simulated core. The coupling agent is silane coupling agent, which is γ-glycidyloxypropyltrimethoxysilane or 3-aminopropyltriethoxysilane.

[0027] (4) Curing conditions: 80 o C for 4 h, then heated to 120 o C solidified for 1h. Example 2

[0028] (1) Preparation of octacyclohexane epoxy alkylene cage-type silsesquioxane: 50 mL of isopropanol, 50 mL of toluene and 20 g of 2% tetramethylammonium hydroxide aqueous solution were added to a three-necked flask equipped with a stirrer, a dropping funnel and a thermometer. A mixed solution of 50 mL of toluene and 55 g of β-(3,4-epoxycyclohexane)ethyltrimethoxysilane was added dropwise using a constant pressure funnel under stirring for a certain period of time. After the addition was completed, the mixture was refluxed and condensed at room temperature and stirred for hydrolysis for 7 hours. After the hydrolysis was complete, the temperature was raised to 80°C. o C for condensation reaction for 1 hour. After the reaction is completed, the reactant is transferred to a separatory funnel, washed with saturated brine until neutral, heated to 65°C, stirred, and distilled under reduced pressure to remove most of the solvent. The resulting solution contains 50g of octacyclohexane epoxy alkylene oxide cage silsesquioxane. A small amount of residual solvent is to ensure that the octacyclohexane epoxy alkylene oxide cage silsesquioxane does not agglomerate, reduce the difficulty of dispersion, and ensure uniform mixing.

[0029] (2) Add 120 g of bisphenol A epoxy resin E-44, 80 g of alicyclic epoxy resin CER-170, 200 g of curing agent methyltetrahydrophthalic anhydride, and 30 g of diluent ethylene glycol diglycidyl ether, mix well at room temperature, and remove the remaining solvent in vacuo to obtain 480 g of liquid resin mixture for use.

[0030] (3) Take 480g of the reserved resin mixture, add 3g of curing accelerator and 5g of coupling agent, mix well, remove bubbles by vacuum, and pour into a mold or simulated rock core.

[0031] (4) Curing conditions: 80 o C for 4 h, then heated to 120 o C solidified for 1h. Example 3

[0032] (1) Preparation of octa(γ-glycidyloxypropyl) cage-type silsesquioxane: 50 mL of isopropanol, 50 mL of toluene and 20 g of 2% tetramethylammonium hydroxide aqueous solution were added to a three-necked flask equipped with a stirrer, a dropping funnel and a thermometer. A mixed solution of 50 mL of toluene and 55 g of γ-glycidyloxypropyltrimethoxysilane (i.e., coupling agent KH560) was added dropwise using a constant pressure funnel under stirring for a certain period of time. After the addition was completed, the mixture was refluxed and condensed at room temperature and stirred for hydrolysis for 7 hours. After the hydrolysis was complete, the temperature was raised to 80°C. o C for condensation reaction for 1 hour. After the reaction is completed, the reactant is transferred to a separatory funnel, washed with saturated brine until neutral, heated to 65°C, stirred, and distilled under reduced pressure to remove most of the solvent. The resulting solution contains 50g of octa(γ-glycidyloxypropyl) cage-type silsesquioxane. A small amount of residual solvent is to ensure that the octa(γ-glycidyloxypropyl) cage-type silsesquioxane does not agglomerate, reduce the difficulty of dispersion, and ensure uniform mixing.

[0033] (2) Add 500 g of bisphenol A epoxy resin E-44, 500 g of alicyclic epoxy resin TDE-85, 800 g of curing agent nadic anhydride, and 250 g of diluent ethylene glycol diglycidyl ether, mix well at room temperature, and remove the remaining solvent in vacuo to obtain 2100 g of liquid resin mixture for use.

[0034] (3) Take 2100g of the reserved resin mixture, add 30g of curing accelerator and 5g of coupling agent, mix well, remove bubbles by vacuum and pour into the mold or simulated core. The coupling agent is silane coupling agent, which is γ-glycidyloxypropyltrimethoxysilane or 3-aminopropyltriethoxysilane.

[0035] (4) Curing conditions: 80 o C for 4 h, then heated to 120 o C solidified for 1h. Example 4

[0036] (1) Preparation of octacyclohexane epoxy alkylene cage-type silsesquioxane: 50 mL of isopropanol, 50 mL of toluene and 20 g of 2% tetramethylammonium hydroxide aqueous solution were added to a three-necked flask equipped with a stirrer, a dropping funnel and a thermometer. A mixed solution of 50 mL of toluene and 55 g of β-(3,4-epoxycyclohexane)ethyltrimethoxysilane was added dropwise using a constant pressure funnel under stirring for a certain period of time. After the addition was completed, the mixture was refluxed and condensed at room temperature and stirred for hydrolysis for 7 hours. After the hydrolysis was complete, the temperature was raised to 80°C. o C for condensation reaction for 1 hour. After the reaction is completed, the reactant is transferred to a separatory funnel, washed with saturated brine until neutral, heated to 65°C, stirred, and distilled under reduced pressure to remove most of the solvent. The resulting solution contains 50g of octacyclohexane epoxy alkylene oxide cage silsesquioxane. A small amount of residual solvent is to ensure that the octacyclohexane epoxy alkylene oxide cage silsesquioxane does not agglomerate, reduce the difficulty of dispersion, and ensure uniform mixing.

[0037] (2) Add 100 g of bisphenol A epoxy resin E-51, 150 g of alicyclic epoxy resin CER-170, 250 g of curing agent nadic anhydride, and 40 g of diluent 1,4-butanediol diglycidyl ether, mix well at room temperature, and remove the remaining solvent in vacuo to obtain 590 g of liquid resin mixture for use.

[0038] (3) Take 590g of the reserved resin mixture, add 4g of curing accelerator and 4g of coupling agent, mix well, remove bubbles by vacuum and pour into the mold or simulated core. The coupling agent is a silane coupling agent, which is γ-glycidyloxypropyltrimethoxysilane or 3-aminopropyltriethoxysilane.

[0039] (4) Curing conditions: 80 o C for 4 h, then heated to 120o C solidified for 1h.

[0040] The formulations of the above examples are summarized in Table 1, wherein the mixed resins are all 100 parts by mass.

[0041] Table 1 List of formulas of epoxy-silicon-based composite resins for oil and gas field plugging in various embodiments

[0042] In production practice, the type and amount of curing accelerator can be specifically controlled according to the well conditions (including downhole temperature and gel time requirements, etc.) to optimize the plugging process. The curing accelerator can be a tertiary amine epoxy-anhydride system curing accelerator, including one of benzyldimethylamine, bicyclic amidine, 2,4,6-tris (dimethylaminotoluene) phenol and triethanolamine.

[0043] Test Case The epoxy-silicon-based composite resin cured products for oil and gas field plugging prepared in the above Examples 1-4 were tested for curing shrinkage, glass transition temperature, compressive strength and plugging rate. The volume change rate was tested in accordance with "ISO 3521-1997 Determination of the total volume shrinkage of unsaturated polyester and epoxy resin plastics", the glass transition temperature was measured using a differential scanning calorimeter, the compressive strength was measured using "GB / T 1041-2008 Determination of compression properties of plastics", and the plugging rate was calculated based on the change rate of gas permeability before and after the simulated core plugging. The results are shown in Tables 2, 3, 4 and 5.

[0044] Table 2 Curing shrinkage of epoxy-silicon-based composite resin for oil and gas field plugging

[0045] Table 3 Glass transition temperature (T) of epoxy-silicon composite resin for oil and gas field plugging g )

[0046] Table 4 Compressive strength of epoxy-silicon composite resin for oil and gas field plugging

[0047] Table 5 Plugging rate of simulated sand cores of epoxy-silicon-based composite resin for plugging oil and gas fields

[0048] From the test results, it can be seen that when the content of octaepoxy cage silsesquioxane exceeds 20 parts by mass, the curing shrinkage can be reduced to less than 2%, and the glass transition temperature and compressive strength are positively correlated with the content of octaepoxy cage silsesquioxane. Due to the reduction in shrinkage, samples with high content of octaepoxy cage silsesquioxane have a higher plugging rate. Each component in the plugging agent formula will affect the performance of the plugging agent, and comprehensive consideration is required when using it.

Claims

1. An epoxy-silicon-based composite resin for plugging oil and gas fields, characterized in that: The invention comprises the following components and their weight proportions: 100 parts of mixed epoxy resin, 5-50 parts of octaepoxy cage-type silsesquioxane, 80-120 parts of curing agent, 5-25 parts of diluent, 0.1-3 parts of curing accelerator and 0.5-3 parts of coupling agent.

2. The epoxy-silicon-based composite resin for plugging oil and gas fields according to claim 1, characterized in that: The mixed epoxy resin is a mixture of bisphenol A epoxy resin and alicyclic epoxy resin, wherein the alicyclic epoxy resin accounts for 10%-60% of the mass of the mixed epoxy resin.

3. The epoxy-silicon-based composite resin for plugging oil and gas fields according to claim 2, characterized in that: The bisphenol A epoxy resin is a liquid bisphenol A epoxy resin, including E-44 type and E-51 type.

4. The epoxy-silicon-based composite resin for plugging oil and gas fields according to claim 2, characterized in that: The alicyclic epoxy resin is an epoxy resin containing one or more alicyclic epoxy groups, including 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexyl carboxylate, namely CER-170 type; 4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester, namely TDE-85 type, and its structural formula is as follows: 。 5. The epoxy-silicon-based composite resin for plugging oil and gas fields according to claim 1, characterized in that: The octa-epoxy cage silsesquioxane is octa-cyclohexane epoxy cage silsesquioxane or octa-(γ-glycidyloxypropyl) cage silsesquioxane, and its structural formula is as follows:

6. The epoxy-silicon-based composite resin for plugging oil and gas fields according to claim 1, characterized in that: The curing agent is one or a mixture of nadic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride and methylhexahydrophthalic anhydride.

7. The epoxy-silicon-based composite resin for plugging oil and gas fields according to claim 1, characterized in that: The diluent is one or a mixture of ethylene glycol diglycidyl ether, butanediol diglycidyl ether and hexanediol diglycidyl ether.

8. The epoxy-silicon-based composite resin for plugging oil and gas fields according to claim 1, characterized in that: The curing accelerator is a tertiary amine epoxy-anhydride system curing accelerator, including one of benzyldimethylamine, bicyclic amidine, 2,4,6-tris(dimethylaminotoluene)phenol and triethanolamine; the coupling agent is a silane coupling agent, which is γ-glycidyloxypropyltrimethoxysilane or 3-aminopropyltriethoxysilane.

9. A method for preparing an epoxy-silicon-based composite resin for plugging oil and gas fields according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) Synthesis of octaepoxy cage-type silsesquioxane; (2) mixing the octaepoxy cage-type silsesquioxane synthesized in step (1) with the mixed epoxy resin, curing agent and diluent for later use; (3) Before going down the well, add curing accelerator and coupling agent.

10. The method for preparing an epoxy-silicon-based composite resin for plugging oil and gas fields according to claim 9, characterized in that: The synthesis steps of the octaepoxy cage-type silsesquioxane in step (1) are as follows: isopropanol, toluene and tetramethylammonium hydroxide aqueous solution are added to a container, a mixed solution of toluene and a silane coupling agent is added dropwise under stirring, refluxed, condensed, stirred and hydrolyzed at room temperature, and then heated to carry out a condensation reaction, after separation, saturated brine is added to wash until neutral, and the solvent is removed by distillation under reduced pressure to obtain the octaepoxy cage-type silsesquioxane.

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