Low-temperature temporary plugging agent for fracturing and preparation method thereof

Abstract

The invention relates to the technical field of plugging materials, and provides a low-temperature temporary plugging agent for fracturing and a preparation method thereof. The low-temperature temporary plugging agent for fracturing 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 nano silicon dioxide; the silicon dioxide B is nano silicon dioxide composite micron silicon dioxide. Through the technical scheme, the problem of low strength of the low-temperature temporary plugging agent in related technologies is solved.

Description

Technical Field

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

[0002] Temporary plugging agents are substances that provide a temporary plugging effect. Based on their solubility characteristics, they can be divided into water-soluble and oil-soluble types. Based on their physical state, they can be categorized into high-viscosity liquids and solid spheres. Solid spheres are the most commonly used, including plastic, nylon, fiber, and rubber balls.

[0003] Currently, efficient and environmentally friendly extraction technologies remain a core pursuit in the oil and gas resource extraction industry. As exploration continues in-depth, numerous low-temperature reservoirs are in urgent need of development. However, conventional temporary plugging agents struggle to achieve both temporary plugging and unblocking effects within the appropriate timeframe at low temperatures, effectively increasing reservoir permeability and creating an ideal fracture network. Consequently, low-temperature temporary plugging agents have emerged as a necessity.

[0004] Chinese invention patent publication number CN112795373A discloses a soluble temporary plugging agent, temporary plugging balls, and their preparation methods for fracturing applications at various temperatures. By introducing nano-silica, the material utilizes its surface defects and numerous unpaired atoms to physically or chemically bond with a polymer, thereby enhancing the temporary plugging agent's strength. However, the nano-silica's tendency to agglomerate limits its ability to enhance the temporary plugging agent's strength. Summary of the Invention

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

[0006] The technical solutions of the present invention are as follows: A low-temperature temporary plugging agent for fracturing, the raw materials of which 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 nano-silicon dioxide; the silicon dioxide B is nano-silicon dioxide composite micron silicon dioxide.

[0007] 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.

[0008] 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.

[0009] 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.

[0010] As a further technical solution, the mass ratio of nano-silicon dioxide to micron-silicon dioxide in the silicon dioxide B is 0.1~1:9, for example, it can be 0.1:9, 0.15:9, 0.2:9, 0.22:9, 0.25:9, 0.27:9, 0.3:9, 0.34:9, 0.35:9, 0.38:9, 0.4:9, 0.5:9, 0.6:9, 0.7:9, 0.8:9, 0.9:9, 1:9, etc., preferably 1:9.

[0011] The mass ratio of silica A to silica B in the present invention can be any ratio, preferably 1:1 to 9, for example, 1:1, 1:2, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, etc., more preferably 1:9.

[0012] As a further technical solution, the preparation method of silicon dioxide B comprises the following steps: mixing nano-silicon dioxide and micro-silicon dioxide, and then ball milling to obtain silicon dioxide B.

[0013] In the present invention, nanosilica and micronized silica are first mixed. Nanosilica, due to its extremely small particle size, large specific surface area, and high surface energy, is prone to agglomeration, making it difficult to maximize its reinforcing effect. Micronized silica, on the other hand, has a relatively large particle size and good dispersion stability. Therefore, the mixed silica mixture is then ball-milled. During the ball-milling process, the mechanical force gradually and evenly disperses the nanosilica particles and coats the surface of the micronized silica, effectively improving the dispersion of the nanosilica and maximizing the reinforcing effect of the silica.

[0014] As a further technical solution, the ball mill has a rotation speed of 400 rpm to 600 rpm, for example, 400 rpm, 420 rpm, 450 rpm, 460 rpm, 490 rpm, 500 rpm, 530 rpm, 550 rpm, 580 rpm, 600 rpm, etc., preferably 400 rpm or 600 rpm.

[0015] As a further technical solution, the ball milling time is 3 to 5 hours, for example, it can be 3 hours, 3.5 hours, 3.7 hours, 4 hours, 4.1 hours, 4.2 hours, 4.5 hours, 4.6 hours, 4.7 hours, 4.9 hours, 5 hours, etc., preferably 5 hours.

[0016] As a further technical solution, the silicon dioxide A and silicon dioxide B are each independently modified with 2-(4-hydroxyphenyl)ethanol or hexacosyl alcohol, preferably with hexacosyl alcohol.

[0017] As a further technical solution, the modification is specifically as follows: after dissolving 2-(4-hydroxyphenyl)ethanol or hexacosyl alcohol in acetone, adding silicon dioxide A and / or silicon dioxide B for modification, and drying.

[0018] As a further technical solution, the mass ratio of the silicon dioxide A and / or silicon dioxide B to 2-(4-hydroxyphenyl)ethanol or hexacosyl alcohol is 100:1~5.

[0019] In the present invention, 2-(4-hydroxyphenyl)ethanol or hexacosyl alcohol is used to modify silicon dioxide A and / or silicon dioxide B, thereby further improving the strength of the temporary plugging agent.

[0020] The particle size of silicon dioxide A in the present invention can be any nanometer-scale particle size, preferably 20 nm.

[0021] The particle size of the nano-silicon dioxide in the silicon dioxide B of the present invention can be any nanometer-scale particle size, preferably 20 nm; The particle size of the micron silicon dioxide in silicon dioxide B can be any micron-sized particle size, preferably 30 μm.

[0022] 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.

[0023] The present invention also proposes a method for preparing a low-temperature temporary plugging agent for 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 to obtain a mixture; S3. After cooling the mixture, add silicon dioxide, mix evenly, and shape to obtain a low-temperature temporary plugging agent.

[0024] In the process of preparing the temporary plugging agent of the present invention, high molecular polymers are first mixed and melted, and then the melt is further mixed with triglycidyl isocyanurate. Triglycidyl isocyanurate, as a multifunctional cross-linking agent, can chemically react with active groups in the high molecular polymer to form a cross-linked network structure between polymer molecular chains, thereby enhancing the cohesion and stability of the polymer system and ensuring the mechanical strength of the temporary plugging agent. After cooling, silicon dioxide is added for reinforcement and to bear part of the external load, so that the temporary plugging agent is not easily deformed or broken when subjected to formation pressure, thereby ensuring the reliability of the temporary plugging effect.

[0025] As a further technical solution, step S3 specifically comprises: after cooling the mixture, first adding silicon dioxide B and mixing evenly, then adding silicon dioxide A and continuing to mix evenly, forming, and obtaining a low-temperature temporary plugging agent.

[0026] In the process of adding silicon dioxide, the silicon dioxide B with a larger particle size is added first, and then the silicon dioxide A with a smaller particle size is added, thereby further improving the strength of the low-temperature temporary plugging agent.

[0027] The present invention also proposes the use of the low-temperature temporary plugging agent for fracturing or the low-temperature temporary plugging agent prepared by the preparation method in fracturing.

[0028] The working principle and beneficial effects of the present invention are: The present invention provides a low-temperature temporary plugging agent suitable for use at temperatures between 30 and 50°C. It utilizes biodegradable polymers, including polycaprolactone, polylactic acid, polyglycolic acid, and polybutylene succinate, as base materials. Triglycidyl isocyanurate serves as a crosslinking agent, which crosslinks with the polymers to enhance the temporary plugging agent's structural stability. Furthermore, the combination of nanosilica and nanosilica composite microsilica provides better dispersibility and forms a strong supporting framework. While nanosilica is prone to agglomeration, it can fill tiny pores. Therefore, the combination of the two not only increases the material's density but also, to a certain extent, avoids the problem of nanosilica agglomeration, ultimately enhancing the temporary plugging agent's strength. DETAILED DESCRIPTION

[0029] 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.

[0030] 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.

[0031] Example 1 S0, after mixing nano-silica and micro-silica in a mass ratio of 1:9, the mixture was ball-milled at a ball-to-material ratio of 2:1 and 600 rpm for 5 h to obtain nano-silica composite micro-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 to the above molten liquid and mix evenly. Carry out polymerization reaction for 40 minutes. Cool to 90°C and add 3 parts of silica (composed of nano-silica and nano-silica composite micro-silica in a mass ratio of 1:9) while stirring. After mixing evenly, cool and shape to obtain a temporary plugging agent.

[0032] Example 2 S0, after mixing nano-silica and micro-silica in a mass ratio of 1:9, ball milling was performed at 400 rpm for 5 h at a ball-to-material ratio of 2:1 to obtain nano-silica composite micro-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 to the above molten liquid and mix evenly. Carry out polymerization reaction for 50 minutes. Cool to 100°C, add 2 parts of silica (composed of nano-silica and nano-silica composite micro-silica in a mass ratio of 1:1) while stirring, mix evenly, cool and shape to obtain a temporary plugging agent.

[0033] Example 3 S0, after mixing nano-silica and micro-silica in a mass ratio of 1:9, the mixture was ball-milled at a ball-to-material ratio of 2:1 and 600 rpm for 5 h to obtain nano-silica composite micro-silica; Dissolve 5 parts of hexacosanol in 130 parts of acetone, add 100 parts of nano-silica composite micro-silica for modification, and dry to obtain silica B; 5 parts of hexacosanol were dissolved in 130 parts of acetone, and 100 parts of nano-silicon dioxide were added for modification, and dried to obtain silicon dioxide A; 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 to the above molten liquid and mix evenly. Carry out polymerization reaction for 40 minutes. Cool to 90°C and add 3 parts of silica (composed of silica A and silica B with a mass ratio of 1:9) while stirring. After mixing evenly, cool and shape to obtain a temporary plugging agent.

[0034] Example 4 The only difference from Example 3 is that hexacosyl alcohol is replaced by an equal amount of 2-(4-hydroxyphenyl)ethanol.

[0035] Example 5 S0, after mixing nano-silica and micro-silica in a mass ratio of 1:9, the mixture was ball-milled at a ball-to-material ratio of 2:1 and 600 rpm for 5 h to obtain nano-silica composite micro-silica; Dissolve 5 parts of hexacosanol in 130 parts of acetone, add 100 parts of nano-silica composite micro-silica for modification, and dry to obtain silica B; 5 parts of hexacosanol were dissolved in 130 parts of acetone, and 100 parts of nano-silicon dioxide were added for modification, and dried to obtain silicon dioxide A; 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 to the above molten liquid and mix evenly. Perform polymerization reaction for 40 minutes. Cool to 90°C, add 2.7 parts of silicon dioxide B while stirring and mix evenly. Then add 0.3 parts of silicon dioxide A and mix evenly. Cool and shape to obtain a temporary plugging agent.

[0036] Example 6 S0, after mixing nano-silica and micro-silica in a mass ratio of 1:9, the mixture was ball-milled at a ball-to-material ratio of 2:1 and 600 rpm for 5 h to obtain nano-silica composite micro-silica; Dissolve 5 parts of hexacosanol in 130 parts of acetone, add 100 parts of nano-silica composite micro-silica for modification, and dry to obtain silica B; 5 parts of hexacosanol were dissolved in 130 parts of acetone, and 100 parts of nano-silicon dioxide were added for modification, and dried to obtain silicon dioxide A; 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 to the above molten liquid and mix evenly. Carry out polymerization reaction for 40 minutes. Cool to 90°C, add 0.3 parts of silicon dioxide A while stirring and mix evenly. Then add 2.7 parts of silicon dioxide B and mix evenly. Cool and shape to obtain a temporary plugging agent.

[0037] Comparative Example 1 S0, after mixing nano-silica and micro-silica in a mass ratio of 1:9, the mixture was ball-milled at a ball-to-material ratio of 2:1 and 600 rpm for 5 h to obtain nano-silica composite micro-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 to the above molten liquid and mix evenly. Carry out polymerization reaction for 40 minutes. Cool to 90°C, add 3 parts of nano-silica composite micro-silica while stirring, mix evenly, cool and shape to obtain a temporary plugging agent.

[0038] 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 to the above molten liquid and mix evenly. Carry out polymerization reaction for 40 minutes. Cool to 90°C, add 3 parts of nano-silicon dioxide while stirring, mix evenly, cool and shape to obtain a temporary plugging agent.

[0039] Comparative Example 3 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 to the above molten liquid and mix evenly. Perform polymerization reaction for 40 minutes. Cool to 90°C, add 0.57 parts of nano-silicon dioxide and 2.43 parts of micron-silicon dioxide while stirring. After mixing evenly, cool and shape to obtain a temporary plugging agent.

[0040] The temporary plugging agents obtained in Examples 1 to 6 and Comparative Examples 1 to 3 were crushed into 40-60 meshes and then subjected to a breakthrough pressure test to characterize the strength of the temporary plugging agents.

[0041] 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.

[0042] Table 1 Breakthrough pressure test results of temporary plugging agent

[0043] As can be seen from Table 1, the breakthrough pressure of the temporary plugging agent provided by the present invention is above 58.4 MPa, indicating that the combined use of nano-silica and nano-silica composite micro-silica improves the strength of the temporary plugging agent.

[0044] 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. A low-temperature temporary plugging agent for fracturing, 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 nano silicon dioxide; the silicon dioxide B is nano silicon dioxide composite micro silicon dioxide.

2. A low-temperature temporary plugging agent for fracturing according to claim 1, characterized in that: The mass ratio of nano-silicon dioxide to micro-silicon dioxide in the silicon dioxide B is 0.1-1:

9.

3. The low-temperature temporary plugging agent for fracturing according to claim 1, characterized in that: The mass ratio of the silicon dioxide A to the silicon dioxide B is 1:1-9.

4. A low-temperature temporary plugging agent for fracturing according to claim 1, characterized in that: The preparation method of silicon dioxide B comprises the following steps: mixing nano silicon dioxide and micro silicon dioxide, and then ball milling to obtain silicon dioxide B.

5. A low-temperature temporary plugging agent for fracturing according to claim 4, characterized in that: The ball milling speed is 400 rpm to 600 rpm, and the ball milling time is 3 to 5 hours.

6. The low-temperature temporary plugging agent for fracturing according to claim 1, characterized in that: The silica A and silica B are each independently modified with 2-(4-hydroxyphenyl)ethanol or hexacosyl alcohol.

7. The low-temperature temporary plugging agent for fracturing according to claim 1, characterized in that: The particle size of the silicon dioxide A is 20 nm; The particle size of the nano-silicon dioxide in the silicon dioxide B is 20 nm; The particle size of the micron silicon dioxide in the silicon dioxide B is 30 μm.

8. A method for preparing a low-temperature temporary plugging agent for fracturing, for preparing the low-temperature temporary plugging agent for fracturing according to any one of claims 1 to 7, 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 to obtain a mixture; S3. After cooling the mixture, add silicon dioxide, mix evenly, and shape to obtain a low-temperature temporary plugging agent.

9. The method for preparing a low-temperature temporary plugging agent for fracturing according to claim 8, characterized in that: Step S3 specifically comprises: after cooling the mixture, first adding silicon dioxide B and mixing evenly, then adding silicon dioxide A and continuing to mix evenly, forming, and obtaining a low-temperature temporary plugging agent.

10. Use of the low-temperature temporary plugging agent for fracturing according to any one of 1 to 7 or the low-temperature temporary plugging agent prepared by the preparation method according to any one of claims 8 to 9 in fracturing.

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