Clean temporary plugging agent for fracture temporary plugging and preparation method thereof

Abstract

The invention relates to the technical field of plugging materials, and provides a clean temporary plugging agent for fracture temporary plugging and a preparation method thereof. The clean temporary plugging agent for fracturing temporary plugging is prepared from the following raw material components: polycaprolactone, polylactic acid, polyglycolic acid, poly (butylene succinate), triglycidyl isocyanurate and silicon dioxide. The silicon dioxide comprises silicon dioxide A and silicon dioxide B; the silicon dioxide A is epoxy siloxane modified silicon dioxide, and the silicon dioxide B is unmodified silicon dioxide. Through the technical scheme, the problem of low strength of the clean temporary plugging agent in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of plugging materials, and in particular to a clean temporary plugging agent for temporary fracturing plugging and a preparation method thereof. Background Art

[0002] Temporary plugging agents are an indispensable and important material in fracturing operations. According to different materials, they can be divided into granular temporary plugging agents, fiber temporary plugging agents and gel temporary plugging agents. Among them, the particle size of granular temporary plugging agents has various specifications. The appropriate particles can be selected according to the pore size of the formation and the width of the crack. Temporary plugging is mainly achieved by forming a bridge in the crack. It has high strength and stability and can withstand greater pressure; fiber temporary plugging agents can be interwoven to form a three-dimensional network structure, which increases the sealing of the temporary plugging. It has good flexibility, can adapt to the deformation of the crack, and can reduce damage to the formation to a certain extent. The gel-type temporary plugging agent can adjust its viscosity and gel time according to needs. It has a good sealing effect on cracks and has good temperature resistance and salt resistance.

[0003] With the increasing global emphasis on environmental protection, higher requirements are being placed on temporary plugging agents. They must not only provide excellent temporary plugging performance but also be environmentally friendly and self-cleaning, minimizing formation damage. Against this backdrop, clean temporary plugging agents are becoming an inevitable trend. Clean temporary plugging agents can effectively seal under high pressure differentials and self-degrade over time, significantly reducing formation contamination and residue damage, providing strong support for efficient, green development.

[0004] Chinese invention patent publication number CN112795373A discloses a soluble temporary plugging agent, temporary plugging balls, and their preparation methods for fracturing suitable for different temperatures. By introducing nano-silica, which has surface defects and numerous unpaired atoms, the agent physically or chemically bonds with a polymer, thereby enhancing its strength. The temporary plugging agent is not only adaptable to different temperatures but also biodegradable. However, the nano-silica easily agglomerates, limiting its strength. Summary of the Invention

[0005] The present invention provides a clean temporary plugging agent for temporary plugging of fracturing and a preparation method thereof, which solves the problem of low strength of the clean temporary plugging agent in the related art.

[0006] The technical solutions of the present invention are as follows: A clean temporary plugging agent for temporary plugging of fracturing, comprising the following raw materials: polycaprolactone, polylactic acid, polyglycolic acid, polybutylene succinate, triglycidyl isocyanurate and silica; the silica comprises silica A and silica B; the silica A is epoxysiloxane-modified silica, and the silica B is unmodified silica.

[0007] As a further technical solution, the raw materials of the epoxysiloxane-modified silica include epoxysiloxane and silica in a mass ratio of 1 to 10:100.

[0008] The epoxysiloxane in the present invention can be any one or more conventional epoxy-containing siloxanes in the art, for example, it can be one or more of 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, preferably 3-glycidyloxypropyltrimethoxysilane.

[0009] The preparation method of the epoxysiloxane-modified silica in the present invention can be any conventional siloxane modification method in the art, preferably: A1. Mixing epoxysiloxane and a solvent to obtain a mixed solution; A2. The mixed liquid is mixed with silicon dioxide, modified, and dried to obtain epoxysiloxane-modified silicon dioxide.

[0010] In the present invention, the solvent in step A1 is preferably anhydrous ethanol.

[0011] The polycaprolactone in the present invention may be any one or more conventional polycaprolactones in the art, for example, BASF PCL D809, Swedish Perstorp PCL 6800, Swedish Perstorp PCL 6500, etc., preferably BASF PCLD809.

[0012] The polylactic acid in the present invention can be any one or more conventional polylactic acids in the art, for example, U.S. NatureWorks PLA 4043D, U.S. NatureWorks PLA 2003D, Anhui Fengyuan PLA FY201, Anhui Fengyuan PLA FY602, Anhui Fengyuan PLA FY601, Anhui Fengyuan PLA FY604, etc., preferably Anhui Fengyuan PLA FY201.

[0013] The polybutylene succinate in the present invention may be any one or more conventional polybutylene succinates in the art, such as BASF PBS E1200, PBS Japan Showa Denko 3001MD, PBS Japan Showa Denko 5001MD, etc., preferably BASF PBS E1200.

[0014] As a further technical solution, the silica particle size in the silica A of the present invention can be of any size, for example, it can be nano-scale silica, micron-scale silica, etc., preferably nano-scale silica, and the particle size can be, for example, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, etc., preferably 20 nm.

[0015] As a further technical solution, the silica particle size in the silica B of the present invention can be of any size, for example, it can be nano-scale silica, micron-scale silica, etc., preferably micron-scale silica, and the particle size can be, for example, 10 μm, 20 μm, 25 μm, 30 μm, 40 μm, 50 μm, 55 μm, 70 μm, 75 μm, 80 μm, 100 μm, etc., preferably 30 μm.

[0016] In the present invention, the silica particle size in silica A is limited to 20 nm, and the silica particle size in silica B is limited to 30 μm, which further improves the strength of the cleaning temporary blocking agent.

[0017] As a further technical solution, the mass ratio of silica A and silica B in the present invention can be any ratio, preferably a mass ratio of 1 to 3:1, for example, 1:1, 1.2:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.3:1, 2.5:1, 2.6:1, 2.7:1, 2.9:1, 3:1, etc.

[0018] As a further technical solution, the silicon dioxide is silicon dioxide A composite with silicon dioxide B.

[0019] In the present invention, the silica A composite silica B is silica A coated with silica B, forming particles similar to a core-shell structure. The surface of silica A coated on the outer layer of silica B is rich in organic functional groups introduced by a silane coupling agent, which can undergo chemical bonding and physical adsorption, significantly improving the compatibility and dispersibility of the particles with the material, avoiding the problem of particle agglomeration in the matrix, and further improving the strength of the cleaning temporary plugging agent.

[0020] As a further technical solution, the method for preparing silicon dioxide comprises the following steps: mixing silicon dioxide A and silicon dioxide B, and then ball milling to obtain silicon dioxide.

[0021] In the present invention, silica A and silica B are first mixed, and then the mixed mixture is ball-milled. During the ball-milling process, silica A is coated on the surface of silica B through the action of mechanical force, which effectively improves the dispersion state of silica and maximizes the reinforcing effect of silica.

[0022] As a further technical solution, the ball milling speed can be any speed, preferably 300~500rpm, for example, it can be 300rpm, 320rpm, 350rpm, 370rpm, 400rpm, 420rpm, 450rpm, 500rpm, etc., preferably 300rpm, 500rpm.

[0023] As a further technical solution, the ball milling time can be any time, preferably 4 to 8 hours, for example, it can be 4h, 4.5h, 5h, 5.3h, 5.5h, 6h, 6.5h, 6.7h, 6.9h, 7h, 7.2h, 7.5h, 8h, etc., preferably 4h or 8h.

[0024] As a further technical solution, the ball-to-material ratio of the ball mill is 1~2:1.

[0025] As a further technical solution, the mass ratio of the polycaprolactone, polylactic acid, polyglycolic acid, polybutylene succinate, triglycidyl isocyanurate and silicon dioxide is 40:22:15:5:15:1 to 3, for example, 40:22:15:5:15:1, 40:22:15:5:15:1.1, 40:22:15:5:15:1.2, 40:22:15:5:15: 1.3, 40:22:15:5:15:1.5, 40:22:15:5:15:1.7, 40:22:15:5:15:1.8, 40:22:15:5:15:2, 40:22:15:5:15:2.3, 40:22:15:5:15:2.5, 40:22:15:5:15:2.8, 40:22:15:5:15:3, etc.

[0026] The present invention also provides a method for preparing a clean temporary plugging agent for temporary plugging of fracturing, which comprises the following steps: S1. Mixing polycaprolactone, polylactic acid, polyglycolic acid, and polybutylene succinate, and melting the mixture to obtain a melt; S2, continuing to mix the melt with triglycidyl isocyanurate and silicon dioxide to obtain a mixture; S3, cooling the mixture and forming it into a shape to obtain a clean temporary plugging agent for temporary plugging of fracturing.

[0027] In the process of preparing the temporary plugging agent, the present invention first mixes the polymers, melts them, and then mixes the melt with triglycidyl isocyanurate and silica. Triglycidyl isocyanurate, a multifunctional crosslinking agent, chemically reacts with the active groups in the polymer to form a crosslinked network between the polymer chains, thereby enhancing the cohesion and stability of the polymer system and ensuring the mechanical strength of the temporary plugging agent. In addition, silica is used for reinforcement, and the epoxy groups on the surface of silica A interact with the active groups in the polymer to bear part of the external load, making the temporary plugging agent less likely to deform or break when subjected to formation pressure, thus ensuring the reliability of the temporary plugging effect.

[0028] The present invention also proposes the use of the clean temporary plugging agent for temporary plugging of fracturing or the clean temporary plugging agent for temporary plugging of fracturing prepared by the preparation method in fracturing.

[0029] The working principle and beneficial effects of the present invention are: 1. The present invention uses biodegradable polymers, including polycaprolactone, polylactic acid, polyglycolic acid and polybutylene succinate, as basic materials, and triglycidyl isocyanurate as a cross-linking agent, which can undergo a cross-linking reaction with the polymer to enhance the structural stability of the temporary plugging agent, thereby providing a clean temporary plugging agent for fracturing temporary plugging.

[0030] 2. The present invention utilizes a combination of silica A and silica B, where silica A is epoxysiloxane-modified silica and silica B is unmodified silica, to enhance the strength of the cleaning temporary plugging agent. When silica A is used exclusively as silica, the system viscosity is too high due to the reaction of the epoxy groups, resulting in uneven silica dispersion. When silica B is used exclusively as silica, the silica easily agglomerates, also leading to uneven silica dispersion and ultimately resulting in low strength of the cleaning temporary plugging agent. Therefore, the present invention achieves the effect of enhancing the strength of the cleaning temporary plugging agent by combining epoxysiloxane-modified silica with unmodified silica. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0032] The parameters of the raw materials in the following examples and comparative examples are as follows: The particle size of nano-silica is 20 nm; The particle size of micronized silica is 30 μm; The model of polycaprolactone is BASF PCL D809; The model of polylactic acid is Anhui Fengyuan PLA FY201; The model of polyglycolic acid is PGA-05, which was purchased from Shandong Zengyi Biotechnology Co., Ltd. The model of polybutylene succinate is BASF PBS E1200.

[0033] Example 1 S0, after the mass ratio of 1: 5 3-glycidyl ether oxypropyl trimethoxy silane and anhydrous ethanol is made into a solution, set aside; according to the mass ratio of 3-glycidyl ether oxypropyl trimethoxy silane and nano-silica is 1: 100, 10 parts of nano-silica are mixed with the above solution, modified, and dried to obtain epoxysiloxane-modified silica; S1, after mixing 22 parts of polylactic acid, 15 parts of polyglycolic acid, 40 parts of polycaprolactone, and 5 parts of polybutylene succinate, heating until melted to obtain a melt; S2. Add 15 parts of triglycidyl isocyanurate and 3 parts of silica (composed of epoxysiloxane-modified silica and nano-silica in a mass ratio of 1:1) to the above-mentioned molten liquid, mix them evenly, carry out polymerization reaction for 60 minutes, cool and shape them, and obtain a temporary plugging agent.

[0034] Example 2 S0, after the mass ratio of 1: 5 3-glycidyl ether oxypropyl trimethoxy silane and anhydrous ethanol is made into a solution, set aside; according to the mass ratio of 3-glycidyl ether oxypropyl trimethoxy silane and nano-silica is 1: 100, 10 parts of nano-silica are mixed with the above solution, modified, and dried to obtain epoxysiloxane-modified silica; S1, after mixing 22 parts of polylactic acid, 15 parts of polyglycolic acid, 40 parts of polycaprolactone, and 5 parts of polybutylene succinate, heating until melted to obtain a melt; S2. Add 15 parts of triglycidyl isocyanurate and 2 parts of silica (composed of epoxysiloxane-modified silica and nano-silica in a mass ratio of 3:1) to the above-mentioned molten liquid, mix them evenly, carry out polymerization reaction for 50 minutes, cool and shape them, and obtain a temporary plugging agent.

[0035] Example 3 S0, after the mass ratio of 1: 5 3-glycidyl ether oxypropyl trimethoxy silane and anhydrous ethanol is made into a solution, set aside; according to the mass ratio of 3-glycidyl ether oxypropyl trimethoxy silane and nano-silica is 1: 100, 10 parts of nano-silica are mixed with the above solution, modified, and dried to obtain epoxysiloxane-modified silica; S1, after mixing 22 parts of polylactic acid, 15 parts of polyglycolic acid, 40 parts of polycaprolactone, and 5 parts of polybutylene succinate, heating until melted to obtain a melt; S2. Add 15 parts of triglycidyl isocyanurate and 3 parts of silica (composed of epoxysiloxane-modified silica and micronized silica in a mass ratio of 1:1) to the above-mentioned molten liquid, mix well, carry out polymerization reaction for 60 minutes, cool and shape, and obtain a temporary plugging agent.

[0036] Example 4 S0, after the mass ratio of 3-glycidyloxypropyl trimethoxysilane and anhydrous ethanol is made into a solution of 1:5, set aside; according to the mass ratio of 3-glycidyloxypropyl trimethoxysilane and micron silica is 1:100, 10 parts of micron silica are mixed with the above solution, modified, and dried to obtain epoxysiloxane-modified silica; S1, after mixing 22 parts of polylactic acid, 15 parts of polyglycolic acid, 40 parts of polycaprolactone, and 5 parts of polybutylene succinate, heating until melted to obtain a melt; S2. Add 15 parts of triglycidyl isocyanurate and 3 parts of silica (composed of epoxysiloxane-modified silica and nano-silica in a mass ratio of 1:1) to the above-mentioned molten liquid, mix them evenly, carry out polymerization reaction for 60 minutes, cool and shape them, and obtain a temporary plugging agent.

[0037] Example 5 S0, after the mass ratio of 3-glycidyloxypropyl trimethoxysilane and anhydrous ethanol is made into a solution of 1:5, set aside; according to the mass ratio of 3-glycidyloxypropyl trimethoxysilane and micron silica is 1:100, 10 parts of micron silica are mixed with the above solution, modified, and dried to obtain epoxysiloxane-modified silica; S1, after mixing 22 parts of polylactic acid, 15 parts of polyglycolic acid, 40 parts of polycaprolactone, and 5 parts of polybutylene succinate, heating until melted to obtain a melt; S2. Add 15 parts of triglycidyl isocyanurate and 3 parts of silica (composed of epoxysiloxane-modified silica and micronized silica in a mass ratio of 1:1) to the above-mentioned molten liquid, mix well, carry out polymerization reaction for 60 minutes, cool and shape, and obtain a temporary plugging agent.

[0038] Example 6 S0, after 3-glycidyloxypropyltrimethoxysilane and anhydrous ethanol in a mass ratio of 1:5 are made into a solution, and the mixture is set aside; according to a mass ratio of 3-glycidyloxypropyltrimethoxysilane and nano-silica of 1:100, 10 parts of nano-silica are mixed with the above solution, modified, and dried to obtain epoxysiloxane-modified silica; after epoxysiloxane-modified silica and micronized silica are mixed in a mass ratio of 1:1, ball-milling is carried out at 400rpm for 5h to obtain silica; S1, after mixing 22 parts of polylactic acid, 15 parts of polyglycolic acid, 40 parts of polycaprolactone, and 5 parts of polybutylene succinate, heating until melted to obtain a melt; S2. Add 15 parts of triglycidyl isocyanurate and 3 parts of silicon dioxide to the above molten liquid, mix them evenly, carry out polymerization reaction for 60 minutes, cool and shape them, and obtain a temporary plugging agent.

[0039] Comparative Example 1 S0, after the mass ratio of 1: 5 3-glycidyl ether oxypropyl trimethoxy silane and anhydrous ethanol is made into a solution, set aside; according to the mass ratio of 3-glycidyl ether oxypropyl trimethoxy silane and nano-silica is 1: 100, 10 parts of nano-silica are mixed with the above solution, modified, and dried to obtain epoxysiloxane-modified silica; S1, after mixing 22 parts of polylactic acid, 15 parts of polyglycolic acid, 40 parts of polycaprolactone, and 5 parts of polybutylene succinate, heating until melted to obtain a melt; S2. Add 15 parts of triglycidyl isocyanurate and 3 parts of epoxysiloxane-modified silica to the above molten liquid, mix them evenly, carry out polymerization reaction for 60 minutes, cool and shape them, and obtain a temporary plugging agent.

[0040] Comparative Example 2 S1, after mixing 22 parts of polylactic acid, 15 parts of polyglycolic acid, 40 parts of polycaprolactone, and 5 parts of polybutylene succinate, heating until melted to obtain a melt; S2. Add 15 parts of triglycidyl isocyanurate and 3 parts of nano-silicon dioxide to the above molten liquid, mix them evenly, carry out polymerization reaction for 60 minutes, cool and shape them, and obtain a temporary plugging agent.

[0041] The temporary plugging agents obtained in Examples 1 to 6 and Comparative Examples 1 to 2 were crushed into 40-60 meshes and then subjected to a breakthrough pressure test to characterize the strength of the temporary plugging agents.

[0042] A temporary plugging agent was used to artificially plug a core with a width of 25 mm, a length of 38 mm, and a crack width of 2.0 mm. The test temperature was 50°C, and a sudden drop in the pumping pressure (a drop of more than 30%) was used as the basis for determining core breakthrough. The highest pressure was the breakthrough pressure. The displacement was 5 L / min, the temporary plugging agent concentration was 5 wt%, and the breakthrough pressure was recorded in Table 1.

[0043] Table 1 Breakthrough pressure test results of temporary plugging agent

[0044] As can be seen from Table 1, the breakthrough pressure of the temporary plugging agent provided by the present invention is above 63 MPa, indicating that the combination of epoxysiloxane-modified silica and unmodified silica improves the strength of the temporary plugging agent.

[0045] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Clean temporary plugging agent for fracturing temporary plugging, characterized in that: The raw materials include the following components: polycaprolactone, polylactic acid, polyglycolic acid, polybutylene succinate, triglycidyl isocyanurate and silicon dioxide; the silicon dioxide includes silicon dioxide A and silicon dioxide B; the silicon dioxide A is epoxysiloxane-modified silicon dioxide, and the silicon dioxide B is unmodified silicon dioxide.

2. The clean temporary plugging agent for fracturing temporary plugging according to claim 1, characterized in that: The silicon dioxide in the silicon dioxide A is nano-scale silicon dioxide; the silicon dioxide in the silicon dioxide B is micron-scale silicon dioxide.

3. The clean temporary plugging agent for fracturing temporary plugging according to claim 1, characterized in that: The mass ratio of the silicon dioxide A to the silicon dioxide B is 1-3:

1.

4. The clean temporary plugging agent for temporary plugging of fracturing according to claim 2, characterized in that: The silicon dioxide is silicon dioxide A composite silicon dioxide B.

5. The clean temporary plugging agent for temporary plugging of fracturing according to claim 4, characterized in that: The method for preparing silicon dioxide comprises the following steps: mixing silicon dioxide A and silicon dioxide B, and then ball milling to obtain silicon dioxide.

6. The clean temporary plugging agent for temporary plugging of fracturing according to claim 5, characterized in that: The ball milling speed is 300-500 rpm, the time is 4-8 hours, and the ball-to-material ratio is 1-2:

1.

7. The clean temporary plugging agent for temporary plugging of fracturing according to claim 2, characterized in that: The particle size of the nano-scale silicon dioxide is 20 nm; the particle size of the micro-scale silicon dioxide is 30 μm.

8. The clean temporary plugging agent for fracturing temporary plugging according to claim 1, characterized in that: The mass ratio of the polycaprolactone, polylactic acid, polyglycolic acid, polybutylene succinate, triglycidyl isocyanurate and silicon dioxide is 40:22:15:5:15:1-3.

9. A method for preparing a clean temporary plugging agent for temporary plugging of fracturing, for preparing the clean temporary plugging agent for temporary plugging of fracturing according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Mixing polycaprolactone, polylactic acid, polyglycolic acid, and polybutylene succinate, and melting the mixture to obtain a melt; S2, continuing to mix the melt with triglycidyl isocyanurate and silicon dioxide to obtain a mixture; S3, cooling the mixture and forming it into a shape to obtain a clean temporary plugging agent for temporary plugging of fracturing.

10. Use of the clean temporary plugging agent for temporary plugging of fracturing according to any one of 1 to 8 or the clean temporary plugging agent for temporary plugging of fracturing prepared by the preparation method according to claim 9 in fracturing.

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