A medium-low temperature self-degradation pod type hole temporary plugging agent, a preparation method and application thereof

Abstract

The application belongs to the technical field of oil field chemicals, and particularly relates to a low-temperature self-degradable pod-shaped perforation temporary plugging agent and a preparation method and application thereof. The low-temperature self-degradable pod-shaped perforation temporary plugging agent comprises: a core of a knot structure, which is made of the low-temperature polyvinyl alcohol water-soluble fiber provided by the application; and a shell, which is made of any one or a combination of two or more of polyvinyl alcohol, starch, cellulose acetate or solid paraffin. The low-temperature self-degradable pod-shaped perforation temporary plugging agent provided by the application has the characteristics of full degradability, can be used for plugging perforations in a reservoir at 20-90 DEG C, has excellent plugging pressure, is dissolved in water without residues, and can reduce damage to the formation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil field chemicals, and particularly relates to a medium-low temperature self-degradable pod-shaped perforation temporary plugging agent and a preparation method and application thereof. BACKGROUND

[0002] Horizontal well volume fracturing technology is an effective means for economic development of unconventional oil and gas, and forming a complex fracture network and improving the complexity of fractures are the key to obtaining industrial oil and gas flow in shale reservoirs. About 90% of shale gas reservoirs in the United States and more than 95% of shale gas reservoirs in China use fine staged fracturing reconstruction technology, but microseismic monitoring technology, production profile testing technology and tracer testing technology show that about 1 / 3 of the perforation clusters are not fully reconstructed due to stress differences, casing deformation and other factors, which seriously affects the single well production.

[0003] The reservoir temperature of some oilfields in China is 20-90℃, and the most commonly used oil and gas well reservoir is 30℃ and 80℃. In recent years, the oil field has made certain effect on the temporary plugging agent used for temporary plugging construction, but the type of temporary plugging agent used is less, and the breakthrough pressure is low. Although the foreign products have excellent performance and good temporary plugging effect, the cost is too high, and they cannot be used on a large scale in oil fields. For example, Slic Frac is a patented technology of THRU TUBING SOLUTIONS company in the United States, which can be selectively pumped into unmodified formations with fracturing fluid, effectively improving the reservoir reconstruction volume, reducing the interference between wells caused by uneven reconstruction, reducing the demand for bridge plug usage in fracturing, saving operation time and cost, and suitable for fracturing reconstruction of newly drilled wells, casing deformation wells and repeated fracturing wells. Due to technical protection and other reasons, this technology has not been introduced into China, and there is no similar authorized patent or technology in China. The conventional temporary plugging agent product mainly uses powder, granule, fiber or spherical body compound, and realizes it through different combinations, addition and other ways. There are many temporary plugging combination ways and addition, which are mainly based on experience, and the plugging efficiency is low, which cannot meet the plugging requirements of different perforation shapes.

[0004] Therefore, a domestic medium-low temperature self-degradable pod-shaped perforation temporary plugging agent is needed to meet the 20-90℃ reservoir diversion fracturing needs of the oil field, which needs to have excellent plugging pressure, low residue content after dissolution, easy flowback and reduce formation damage. SUMMARY

[0005] In order to effectively improve the reservoir reconstruction volume and solve the technical problems that the perforation clusters are not fully reconstructed due to stress differences, casing deformation and other factors, which seriously affect the single well production, the application provides a medium-low temperature self-degradable pod-shaped perforation temporary plugging agent and a preparation method and application thereof. The medium-low temperature self-degradable pod-shaped perforation temporary plugging agent provided by the application can solve the problems of few types of temporary plugging agents and low breakthrough pressure in the 20-90℃ medium-low reservoir diversion fracturing of the oil field.

[0006] The technical solutions provided by the present application are as follows:

[0007] A low-temperature self-degradable pod-shaped hole temporary plugging agent, comprising an inner core knot and an outer shell, the inner core knot comprises the following components by weight: 65-75 parts by weight of polyvinyl alcohol, 0.01-1 parts by weight of inorganic nucleating agent, 0.01-1 parts by weight of nucleating dispersant, 0.01-3 parts by weight of antioxidant, 20-30 parts by weight of hydrolysis-resistant stabilizer.

[0008] The above technical solution has the characteristics of full biodegradability and can be used to prepare a hole temporary plugging agent for a reservoir at 20-90℃, which can have excellent plugging pressure, dissolve in water without residue, and reduce damage to the formation.

[0009] Specifically, the molecular weight of polyvinyl alcohol in the inner core knot is 5-300 million daltons, the polymerization degree is 1000-3000, the alcoholysis degree is 70%-99%, and the fineness is 20-200 mesh powder.

[0010] Specifically, the inorganic nucleating agent in the inner core knot is one or more of nano-titanium dioxide, nano-silicon dioxide, nano-calcium carbonate or nano-graphene oxide.

[0011] Specifically, the nucleating dispersant in the inner core knot is NP-10.

[0012] Specifically, the antioxidant in the inner core knot is tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid] pentaerythritol ester.

[0013] The hydrolysis-resistant stabilizer in the inner core knot has the following corresponding formulations for reservoir plugging at different temperatures of 20-40℃, 40-50℃, 60-70℃ and 80-90℃:

[0014] The hydrolysis-resistant stabilizer for reservoir plugging at 20-40℃ is a compounded plasticizer of stearic acid, stearic acid emulsifier AE-96 and polyethylene glycol-400, and preferably the weight ratio of the three is 1:1:1.

[0015] The hydrolysis-resistant stabilizer for reservoir plugging at 40-50℃ is a compounded plasticizer of glycerol and citric acid, and preferably the weight ratio of the two is 70:30.

[0016] The hydrolysis-resistant stabilizer for reservoir plugging at 60-70℃ is a compounded plasticizer of pentaerythritol and boric acid, and preferably the weight ratio of the two is 80:20.

[0017] The hydrolysis-resistant stabilizer for reservoir plugging at 80-90℃ is a compounded plasticizer of mannitol, glutaraldehyde and urea, and preferably the weight ratio of the three is 70:20:10.

[0018] Specifically, the outer shell material is any one or a combination of two or more of polyvinyl alcohol, starch, cellulose acetate, or solid paraffin. Such materials can also self-degrade at 20-90°C, disintegrating into microparticles that dissolve in water.

[0019] Specifically, the diameter of the core knot is 10-25mm; the length of the rope ends at both ends of the knot is 30-80mm; the outer diameter of the outer shell is 20-35mm; and the wall thickness of the outer shell is 1-3mm.

[0020] Preferably, the material of the core knot is a medium-low temperature polyvinyl alcohol water-soluble fiber prepared by melt spinning from 65-75 parts by weight of polyvinyl alcohol, 0.01-1 parts by weight of inorganic nucleating agent, 0.01-1 parts by weight of nucleating dispersant, 0.01-3 parts by weight of antioxidant, and 20-30 parts by weight of anti-hydrolysis stabilizer.

[0021] The present invention also provides a method for preparing the above-mentioned medium- and low-temperature polyvinyl alcohol water-soluble fiber, comprising the following steps: according to the formula, 65-75 parts by weight of polyvinyl alcohol, 0.01-1 parts by weight of inorganic nucleating agent, 0.01-1 parts by weight of nucleating dispersant, 0.01-3 parts by weight of antioxidant, and 20-30 parts by weight of anti-hydrolysis stabilizer are added to a twin-screw extruder and fully melted. The melt is then processed by a spinning assembly and ejected from a spinneret. It is melt-spun into filaments, which are then cooled by blowing air to obtain polyvinyl alcohol nascent fibers. The polyvinyl alcohol nascent fibers are then sequentially stretched, shaped, and dried to obtain the medium- and low-temperature polyvinyl alcohol water-soluble fiber.

[0022] Specifically:

[0023] The temperatures of each zone of the screw are: 40-60℃ in the feeding zone, 150-200℃ in the melting zone, 150-200℃ in the compression zone, and 150-200℃ in the metering zone.

[0024] The spinneret temperature is 180℃~200℃;

[0025] The filaments produced by melt spinning are 150D;

[0026] The temperature of the cooling air is 30–70°C;

[0027] The fibers are stretched 3.5-4 times at 100-130℃;

[0028] The fibers are relaxed and heat-set in an oven at 100-160℃.

[0029] The fiber drying temperature is 70-100℃.

[0030] This invention also provides a method for preparing a medium- and low-temperature self-degrading pod-shaped blast hole plugging agent, comprising the following steps:

[0031] 1) two half edges of the shell are prepared by injection molding;

[0032] 2) according to the amount of the formula, the polyvinyl alcohol, inorganic nucleating agent, nucleating dispersant, antioxidant, anti-hydrolysis stabilizer is melt spun into 150D filament, and a low-temperature polyvinyl alcohol water-soluble fiber is prepared, then the fiber is twisted into 1200D fine line, then the fine line is knitted into a rope with different strands according to 12, 16, 24, 36 strands respectively, then the obtained rope with different strands is knitted into a knot-shaped rope knot structure, and then the rope heads at both ends of the knot are scattered;

[0033] 3) the inner core is assembled into the two half edges of the shell, and the two half edges are fixedly connected into a whole shell, preferably by clamping or threaded connection, etc., to obtain the low-temperature self-degradable pod-shaped perforation temporary plugging agent.

[0034] Through the above scheme, the low-temperature self-degradable pod-shaped perforation temporary plugging agent can be conveniently prepared.

[0035] The application also provides an application of the low-temperature self-degradable pod-shaped perforation temporary plugging agent as a perforation temporary plugging agent for oil and gas well fracturing.

[0036] Specifically, as a perforation temporary plugging agent for a 20-90℃ reservoir.

[0037] The low-temperature self-degradable pod-shaped perforation temporary plugging agent provided by the application can meet the requirements of 20-90℃ low-temperature reservoirs, reduce the demand for bridge plug usage in fracturing, save operation time and cost, and is suitable for fracturing reconstruction of newly drilled wells, casing change wells and repeated fracturing wells.

[0038] Compared with the prior art, the application has the following advantages:

[0039] 1. The low-temperature self-degradable pod-shaped perforation temporary plugging agent provided by the application has the characteristics of complete degradability, can be used for plugging perforations in a 20-90℃ reservoir, has excellent plugging pressure, is dissolved in water without residue, and reduces damage to the formation.

[0040] 2. The temporary plugging agent provided by the application can withstand a pressure of 70MPa for more than 2h, has a dissolution rate of 100%, and has a use temperature of 20-90℃.

[0041] 3. The controllable degradable temporary plugging agent prepared by the application has a simple preparation method, is easy to operate, has low cost, and has good economic popularization value. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is the degradation curve of the temporary plugging agent A in a 30℃ water solution.

[0043] Figure 2 This is the degradation curve of temporary plugging agent B in an aqueous solution at 50°C.

[0044] Figure 3 This is the degradation curve of temporary plugging agent C in an aqueous solution at 70℃.

[0045] Figure 4 This is the degradation curve of temporary plugging agent D in an aqueous solution at 90℃.

[0046] Figure 5 It is a construction curve diagram. Detailed Implementation

[0047] The principles and features of the present invention are described below. The embodiments given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0048] Example 1

[0049] This embodiment provides a low-temperature, self-degrading pod-shaped temporary plugging agent A for fracturing, the preparation method of which includes the following steps:

[0050] 1) A low-temperature self-degrading pod-shaped blast hole plugging agent polyvinyl alcohol shell with a diameter of 35 mm and a wall thickness of 2 mm was prepared by injection molding.

[0051] 2) Low-temperature polyvinyl alcohol water-soluble fiber melt spinning raw material: 75 parts polyvinyl alcohol powder; 25 parts plasticizer, 0.05 parts inorganic nucleating agent, 0.15 parts nucleating dispersant, and 0.15 parts antioxidant. The compound plasticizer is a compound plasticizer with stearic acid, stearic acid emulsifier AE-96, and polyethylene glycol-400 in a weight ratio of 1:1:1; 3) The prepared low-temperature polyvinyl alcohol water-soluble fiber melt spinning raw material is melt-spun into 150D filaments and twisted into 1200D fine yarn. Then, the fine yarn is braided into ropes with 12, 16, 24, and 36 strands. The ropes of different sizes are then mixed and braided into a knot-like structure. The ends of the rope are untied. The rope diameter is 20mm, and the length of the double-winged ends formed by untiing is about 40mm.

[0052] 4) Assemble the core into the outer shell and fasten the two halves of the outer shell together to obtain the pod-shaped blast hole plugging agent.

[0053] In step 2), the parameters of the polyvinyl alcohol powder are 40 mesh; the inorganic nucleating agent is nano titanium dioxide; the nucleating dispersant is NP-10; and the antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0054] In step 3):

[0055] The temperature settings for each zone of the screw are: 50℃ for the feeding zone, 170℃ for the melting zone, 180℃ for the compression zone, and 190℃ for the metering zone.

[0056] The spinneret temperature is 200℃;

[0057] The temperature of the cooling air is 70℃;

[0058] The fiber is stretched 120 times at 120°C;

[0059] The fibers are subjected to relaxation heat setting in an oven at 120°C;

[0060] The fiber drying temperature is 90℃;

[0061] 12, 16, 24, and 36 strands are braided into a rope in a ratio of 1:1:1:1.

[0062] Example 2

[0063] This embodiment provides a low-temperature, self-degrading pod-shaped borehole plugging agent B for fracturing, the preparation method of which includes the following steps:

[0064] 1) A low-temperature self-degrading pod-shaped blast hole plugging agent polyvinyl alcohol shell with a diameter of 35 mm and a wall thickness of 2 mm was prepared by injection molding.

[0065] 2) Low-temperature polyvinyl alcohol water-soluble fiber melt spinning raw material: 70 parts polyvinyl alcohol powder; 30 parts plasticizer, 0.1 parts inorganic nucleating agent, 0.3 parts nucleating dispersant, and 0.5 parts antioxidant. The compound plasticizer is a compound plasticizer containing glycerol and citric acid in a weight ratio of 70:30; 3) The prepared low-temperature polyvinyl alcohol water-soluble fiber melt spinning raw material is melt-spun into 150D filaments and twisted into 1200D fine yarn. Then, the fine yarn is braided into ropes with 12, 16, 24, and 36 strands. The ropes of different sizes are then mixed and braided into a knot-like structure. The rope ends at both ends of the knot are untied, and the knot diameter is 20mm. The length of the double-winged yarn ends formed by untiing is about 40mm.

[0066] 4) Assemble the core into the outer shell and fasten the two halves of the outer shell together to obtain the pod-shaped blast hole plugging agent.

[0067] The selection of other reagents and process parameters in each step are the same as in Example 1.

[0068] Example 3

[0069] This embodiment provides a low-temperature, self-degrading pod-shaped perforation plugging agent C for fracturing, the preparation method of which includes the following steps:

[0070] 1) A low-temperature self-degrading pod-shaped blast hole plugging agent polyvinyl alcohol shell with a diameter of 35 mm and a wall thickness of 2 mm was prepared by injection molding.

[0071] 2) Raw material for melt spinning of low-temperature polyvinyl alcohol water-soluble fiber filaments: 70 parts polyvinyl alcohol powder; 30 parts plasticizer; 0.3 parts inorganic nucleating agent; 0.6 parts nucleating dispersant; 1 part antioxidant. The compound plasticizer is a compound plasticizer with a weight ratio of pentaerythritol and boric acid of 80:20.

[0072] 3) The prepared low-temperature polyvinyl alcohol water-soluble fiber raw material is melt-spun into 150D fine filaments and twisted into 1200D fine thread. Then the fine thread is braided into ropes with 12, 16, 24 and 36 strands. The ropes of different sizes are then mixed and braided into a knot-like structure. The rope ends at both ends of the knot are untied. The knot diameter is 20mm, and the length of the double-winged thread ends formed by untiing is about 40mm.

[0073] 4) Assemble the core into the outer shell and fasten the two halves of the outer shell together to obtain the pod-shaped blast hole plugging agent.

[0074] The selection of other reagents and process parameters in each step are the same as in Example 1.

[0075] Example 4

[0076] This embodiment provides a low-temperature, self-degrading pod-shaped temporary plugging agent D for fracturing, the preparation method of which includes the following steps:

[0077] 1) A low-temperature self-degrading pod-shaped blast hole plugging agent polyvinyl alcohol shell with a diameter of 35 mm and a wall thickness of 2 mm was prepared by injection molding.

[0078] 2) Raw material for melt spinning of low-temperature polyvinyl alcohol water-soluble fiber filaments: 65 parts polyvinyl alcohol powder; 35 parts plasticizer; 0.5 parts inorganic nucleating agent; 1 part nucleating dispersant; 2 parts antioxidant. Among them, the compound plasticizer is a compound plasticizer with a weight ratio of mannitol, glutaraldehyde and urea of ​​70:20:10.

[0079] 3) The prepared low-temperature polyvinyl alcohol water-soluble fiber raw material is melt-spun into 150D fine filaments and twisted into 1200D fine thread. Then the fine thread is braided into ropes with 12, 16, 24 and 36 strands. The ropes of different sizes are then mixed and braided into a knot-like structure. The rope ends at both ends of the knot are untied. The knot diameter is 20mm, and the length of the double-winged thread ends formed by untiing is about 40mm.

[0080] 4) Assemble the core into the outer shell and fasten the two halves of the outer shell together to obtain the pod-shaped blast hole plugging agent.

[0081] The selection of other reagents and process parameters in each step are the same as in Example 1.

[0082] Example 5

[0083] In this embodiment, the low-temperature self-degrading pod-shaped temporary plugging agent prepared in the above embodiments was tested according to SY / T5108-2006 "Performance Indicators and Recommended Test Methods for Fracturing Proppants". The compressive strength test results are as follows:

[0084] 1. Temporary plugging agent A with an outer shell diameter of 35mm, an outer shell wall thickness of 2mm, an inner core diameter of 20mm, and a 40mm long double-wing wire end formed by breaking it up can withstand a pressure of 70MPa at 30℃ for 2.5 hours.

[0085] 2. Temporary plugging agent B with an outer shell diameter of 35mm, an outer shell wall thickness of 2mm, an inner core diameter of 20mm, and a 40mm long double-wing wire end formed by breaking up the shell can withstand a pressure of 70MPa at 50℃ for 3 hours.

[0086] 3. The temporary plugging agent C with an outer shell diameter of 35mm, an outer shell wall thickness of 2mm, an inner core diameter of 20mm, and a broken-up double-wing wire end length of 40mm can withstand a pressure of 70MPa at 70℃ for 3 hours.

[0087] 4. Temporary plugging agent D with an outer shell diameter of 35mm, an outer shell wall thickness of 2mm, an inner core diameter of 20mm, and a 40mm long double-wing wire end formed by breaking up the material can withstand a pressure of 70MPa at 90℃ for 2.5 hours.

[0088] Dissolution time: e.g. Figures 1-4 The figures show the dissolution curves of the temporary plugging agents obtained in Examples 1-4 at different temperatures. It can be seen that the temporary plugging agents with an outer shell diameter of 35 mm, an outer shell wall thickness of 2 mm, an inner core diameter of 20 mm, and a 40 mm long double-winged wire head formed by dispersing can meet the requirement of natural degradation under simulated conditions for 24 to 96 hours after losing mechanical strength at the reservoir temperature.

[0089] Application examples

[0090] On December 22, 2021, a shale gas well, XX, underwent fracturing using a pod-type biodegradable temporary plugging agent. Figure 5 This is a construction curve diagram. The calculated horizontal force difference of the well is 7.5 MPa. 59 35mm temporary plugging agents were used during construction. Slickwater volumetric fracturing was performed, and 0.2% linear gel working fluid was used to temporarily plug the fractured fracture system. A 13.5m... 3During a 10.0-minute fracturing operation at a flow rate of / min, the surface fracturing pressure increased from 25.3 MPa to 47.8 MPa, a pressure increase of 22.5 MPa, far exceeding the stress difference between the two horizontal axes, resulting in multi-branch fractures. Post-fracturing fracture monitoring results showed the formation of one main fracture and two branch fractures. Recently, this well achieved a high-yield gas flow of nearly one million cubic meters per day with no obstruction after fracturing, demonstrating a significant improvement in production. This demonstrates that the pod-shaped biodegradable temporary plugging agent provided by this invention possesses excellent plugging performance.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A self-degradable pod-shaped temporary plugging agent for blast holes, comprising a core knot and a shell, characterized in that, The core knot comprises the following components in parts by weight: 65-75 parts polyvinyl alcohol, 0.01-1 parts inorganic nucleating agent, 0.01-1 parts nucleating dispersant, 0.01-3 parts antioxidant, and 20-30 parts hydrolysis stabilizer.

2. The self-degrading pod-shaped temporary plugging agent according to claim 1, characterized in that: The polyvinyl alcohol in the core knot has a molecular weight of 50,000-300,000 Daltons, a degree of polymerization of 1,000-3,000, a degree of alcoholysis of 70%-99%, and a fineness of 20-200 mesh.

3. The self-degrading pod-shaped temporary plugging agent according to claim 1, characterized in that: The inorganic nucleating agent in the core knot is one or more composites of nano-titanium dioxide, nano-silicon dioxide, nano-calcium carbonate, or nano-graphene oxide. The nucleating dispersant in the kernel knot is NP-10.

4. The self-degrading pod-shaped temporary plugging agent according to claim 1, characterized in that: The antioxidant in the core knot is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid].

5. The self-degrading pod-shaped temporary plugging agent according to claim 1, characterized in that, The formulations of the hydrolysis-resistant stabilizer in the core knot for reservoir plugging at different temperatures (20-40℃, 40-50℃, 60-70℃, and 80-90℃) are as follows: The hydrolysis-resistant stabilizer corresponding to reservoir plugging at 20-40℃ is a compound plasticizer consisting of stearic acid, stearic acid emulsifier AE-96, and polyethylene glycol-400; The hydrolysis-resistant stabilizer corresponding to reservoir plugging at 40-50℃ is a compound plasticizer of glycerol and citric acid; The hydrolysis-resistant stabilizer corresponding to reservoir plugging at 60-70℃ is a compound plasticizer of pentaerythritol and boric acid; The hydrolysis-resistant stabilizer corresponding to reservoir plugging at 80-90℃ is a compound plasticizer of mannitol, glutaraldehyde, and urea.

6. The self-degrading pod-type temporary plugging agent according to claim 1, characterized in that: The core knot is made of polyvinyl alcohol water-soluble fiber prepared by melt spinning from 65-75 parts by weight of polyvinyl alcohol, 0.01-1 parts by weight of inorganic nucleating agent, 0.01-1 parts by weight of nucleating dispersant, 0.01-3 parts by weight of antioxidant, and 20-30 parts by weight of anti-hydrolysis stabilizer. The outer shell material is any one or a combination of two or more of polyvinyl alcohol, starch, cellulose acetate, or solid paraffin.

7. The self-degrading pod-type temporary plugging agent according to any one of claims 1-6, characterized in that: The diameter of the core knot is 10-25mm; the length of the rope ends at both ends of the knot is 30-80mm; the outer diameter of the outer shell is 20-35mm; and the wall thickness of the outer shell is 1-3mm.

8. A method for preparing polyvinyl alcohol water-soluble fiber, characterized in that, The process includes the following steps: According to the formula, 65-75 parts by weight of polyvinyl alcohol, 0.01-1 parts by weight of inorganic nucleating agent, 0.01-1 parts by weight of nucleating dispersant, 0.01-3 parts by weight of antioxidant, and 20-30 parts by weight of anti-hydrolysis stabilizer are added to a twin-screw extruder and fully melted. The melt is then processed by a spinning assembly and ejected from a spinneret. It is melt-spun into filaments, which are then cooled by blowing air to obtain polyvinyl alcohol nascent fibers. The polyvinyl alcohol nascent fibers are then sequentially stretched, shaped, and dried to obtain the polyvinyl alcohol water-soluble fiber.

9. The method for preparing polyvinyl alcohol water-soluble fiber according to claim 8, characterized in that: The temperatures of each zone of the screw are: 40-60℃ in the feeding zone, 150-200℃ in the melting zone, 150-200℃ in the compression zone, and 150-200℃ in the metering zone. The spinneret temperature is 180℃~200℃; The filaments produced by melt spinning are 150D; The temperature of the cooling air is 30–70°C; The fibers are stretched 3.5-4 times at 100-130℃; The fibers are relaxed and heat-set in an oven at 100-160℃. The fiber drying temperature is 70-100℃.

10. A method for preparing a self-degradable pod-shaped blast hole plugging agent according to any one of claims 1 to 7, characterized in that, Includes the following steps: 1) The two halves of the outer shell are prepared by injection molding; 2) According to the formula, the polyvinyl alcohol, inorganic nucleating agent, nucleating dispersant, antioxidant, and hydrolysis stabilizer are melt-spun into 150D fine filaments and prepared into polyvinyl alcohol water-soluble fibers. Then, the fibers are twisted into 1200D fine threads. The fine threads are then braided into ropes with different numbers of strands (12, 16, 24, and 36 strands). The ropes with different numbers of strands are then braided into knot-like structures. Finally, the ends of the ropes at both ends of the knots are untied. 3) Assemble the core into the two halves of the outer shell, and fix the two halves together to form the entire shell by means of snap-fit ​​or threaded connection, to obtain the self-degradable pod-shaped blast hole plugging agent.

11. The application of the self-degradable pod-shaped perforation plugging agent according to any one of claims 1 to 7 in the fracturing and extraction process of oil and gas wells, characterized in that: As a temporary plugging agent for blast holes in reservoirs with temperatures ranging from 20 to 90°C.

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