First composite material and second composite material containing the same

Abstract

The application provides a first composite material and a second composite material containing the same. The first composite material is prepared from a first ethylene-propylene-lactide copolymer and ammonium polyphosphate, can be directly extruded into a pull rod, and after cooling, is wound into a cylindrical wire with good heat resistance. The second composite material has a skin-core structure, the first composite material is used as a core layer material, and a second ethylene-propylene-lactide copolymer is used as a skin layer material. Temporary blocking particles obtained by physically cutting the second composite material in a direction perpendicular to the cylindrical axis have excellent low-temperature degradation and dissolution performance, good dissolution effect in a water-deficient environment, and high blocking strength.

Description

Technical Field

[0001] This invention belongs to the field of natural gas production enhancement technology, and particularly relates to a first composite material and a second composite material containing the same. Background Technology

[0002] Currently, temporary plugging and redirection fracturing technology has become an important technical approach for increasing oil and gas production. This technology involves adding a temporary plugging agent to the working fluid or sand-mixing truck during fracturing operations to temporarily seal existing or sand-filled fractures. Changes in fracturing pressure and fracture propagation pressure force the fluid to redirect, thus creating new fractures. By temporarily plugging sand-filled fractures, the orientation of the repeated fracturing fractures deviates from the original fractures, thereby connecting reservoirs with low or no utilization. Temporary plugging and redirection fracturing technology not only produces increased oil and gas production but can also, to some extent, change the direction of water drive and improve the utilization rate of injected water.

[0003] Common temporary plugging agents can be classified into dissolving and degrading temporary plugging agents based on their failure mechanism. Dissolving temporary plugging agents dissolve in water under specific conditions, forming a solution that renders the plugging ineffective. The dissolution effect of these agents is significantly affected by water salinity, water volume, and water temperature. Furthermore, dissolution is not the same as degradation, which can easily cause environmental pollution. Degrading temporary plugging agents, on the other hand, undergo chain breaking in specific aquatic environments, degrading into smaller molecules that eventually dissolve in water, thus rendering the plugging ineffective. Typical degrading temporary plugging agents include polyglycolic acid and polylactic acid. Most degrading temporary plugging agents can be decomposed by microorganisms into non-toxic and harmless substances such as carbon dioxide and water. These agents are increasingly favored due to their excellent degradation adaptability (the degradation effect is relatively less affected by water salinity) and environmentally friendly characteristics.

[0004] However, the temporary plugging agents widely used in medium-temperature oil and gas fields with well temperatures ranging from 60°C to 90°C are mostly dissolving temporary plugging agents (common examples include polyacrylamide and water-soluble polyacrylic acid). Their dissolution process requires a large water environment or a specific mineralization environment (some temporary plugging agents cannot dissolve under high mineralization). However, the actual situation downhole is extremely complex. In some cases, the temporary plugging agent may not be able to come into contact with a large water environment or the surrounding water body may have a high mineralization, which may result in the temporary plugging agent failing to dissolve, causing well blockage and other accidents.

[0005] During the application of temporary plugging agents, a precise survey of the fractures to be plugged is required, followed by selection of an appropriate particle size based on the fracture width. However, fracture widths often vary, complicating particle size selection and potentially leading to waste. Furthermore, achieving high-strength plugging often necessitates the combined use of rigid and flexible plugging agents, such as injecting them sequentially downhole. This method further complicates the process, increases costs, and, since the flexible plugging materials used are typically solvent-based, they can easily cause well blockage accidents when used in gas well fracturing.

[0006] Therefore, there is a need to find a high-strength temporary plugging agent that is easy to apply, highly adaptable to cracks, has low requirements for downhole water quality, and is environmentally friendly. Summary of the Invention

[0007] A first aspect of the present invention provides a first composite material comprising a first ethylene lactide copolymer and ammonium polyphosphate.

[0008] According to a specific embodiment of the present invention, the mass ratio of the first ethylene lactide copolymer to ammonium polyphosphate is (2 to 4):1.

[0009] According to one specific embodiment of the present invention, the first glycolide-lactide copolymer is obtained by copolymerizing glycolide and lactide in a molar ratio of 85:15; and / or

[0010] The weight-average molecular weight of the first ethylene-lactide copolymer is greater than 50,000;

[0011] Preferably, the weight-average molecular weight of the first ethylene lactide copolymer is 50,000 to 100,000.

[0012] According to one specific embodiment of the present invention, the degree of polymerization of the ammonium polyphosphate is 1000 to 1200.

[0013] A second aspect of the present invention provides a method for preparing the composite material as described in the first aspect of the present invention, comprising the following steps:

[0014] 1) The first ethylene-lactide copolymer and ammonium polyphosphate are mixed and granulated to obtain an intermediate material;

[0015] 2) The intermediate material is extruded into strips, cooled, and then wound up to obtain the first composite material.

[0016] According to a specific embodiment of the present invention, in step 1), the granulation is performed using a twin-screw granulator;

[0017] Preferably, the granulation conditions are melt extrusion granulation at 170°C to 190°C; and / or

[0018] The screw speed of the twin-screw granulator is 200 r / min; and / or

[0019] The intermediate material is cylindrical particles with an average diameter of 3 mm and an average height of 3 mm.

[0020] According to a specific embodiment of the present invention, in step 2), the extrusion strip is performed using a 3D printing filament machine;

[0021] Preferably, the intermediate material is extruded into strands at 175°C to 190°C; and / or

[0022] The filament diameter of the 3D printing filament machine is set to 1mm to 2mm; and / or

[0023] The screw speed of the 3D printing filament machine is 80 r / min;

[0024] Preferably, the intermediate material is cooled to room temperature (25°C) after being extruded into strips before being wound up.

[0025] A third aspect of the present invention provides a second composite material having a core-skin structure; the core layer of the core-skin structure is made of a first composite material; and the skin layer of the core-skin structure is made of a second glycolide copolymer.

[0026] The first composite material is the first composite material described in the first aspect of the present invention or the first composite material prepared by the method described in the second aspect of the present invention.

[0027] According to one specific embodiment of the present invention, the second glycolide-lactide copolymer is obtained by copolymerizing glycolide and lactide in a molar ratio of (30 to 70):(70 to 30); and / or

[0028] The weight-average molecular weight of the second ethylene glycol copolymer is 30,000 to 50,000.

[0029] Preferably, the second glycolide copolymer is obtained by copolymerizing glycolide and lactide in a molar ratio of 50:50.

[0030] According to a specific embodiment of the present invention, the second composite material is a cylindrical composite material having the core-skin structure;

[0031] Preferably, the core layer in the core-skin structure is a cylinder with a diameter of 1 mm to 2 mm; and / or

[0032] The thickness of the skin layer in the core-skin structure is 0.5 mm to 1 mm.

[0033] A fourth aspect of the present invention provides a method for preparing a second composite material as described in a third aspect of the present invention, comprising the following steps:

[0034] The second ethylene lactide copolymer is coated on the surface of the core layer, drawn, and cooled to obtain the second composite material.

[0035] According to one specific embodiment of the present invention, the coating and traction are achieved by an electric wire extruder;

[0036] Preferably, the temperature of the feed hopper of the wire extruder is 110°C to 130°C; and / or

[0037] The rotational speed of the screw of the wire extruder shall not exceed 400 r / min; and / or the traction speed shall not exceed 200 r / min;

[0038] Preferably, the temperature of the feed hopper of the wire extruder is 120°C to 130°C; and / or

[0039] The cooling is cooling to room temperature (25°C); and / or

[0040] The traction speed of the wire extruder is 60 r / min.

[0041] According to a specific embodiment of the present invention, the second composite material is granulated along a direction perpendicular to the cylindrical axis to obtain temporary plugging particles;

[0042] Preferably, the temporary plugging particles are cylindrical with a diameter of 2 mm to 4 mm; and / or their height is 3 mm to 5 mm.

[0043] Preferably, the diameter of the temporary plugging particles is 2.5 mm to 4 mm.

[0044] The application of any one of the first composite material according to the first aspect of the present invention, the first composite material prepared by the method according to the second aspect of the present invention, the second composite material according to the third aspect of the present invention, and the second composite material prepared by the method according to the fourth aspect of the present invention in the field of natural gas production enhancement technology, particularly in the application of temporary plugging and diversion fracturing. Beneficial effects of the present invention:

[0045] To address the problems of poor fracture adaptability, high requirements for downhole water quality, environmental pollution, and complex construction associated with existing temporary plugging agents, this invention provides a first composite material and a second composite material containing the same. The first composite material is prepared from a first ethylene-lactide copolymer and ammonium polyphosphate. The specific copolymerization molar ratio of ethylene-lactide and lactide in the first ethylene-lactide copolymer and the addition of ammonium polyphosphate allow the first composite material to be directly extruded into strands, cooled, and then wound into a heat-resistant cylindrical wire. The second composite material has a core-skin structure, with the first composite material as the core layer and the second ethylene-lactide copolymer as the skin layer. The temporary plugging particles obtained by physically granulating the second composite material along a direction perpendicular to the cylindrical axis have superior properties. The temporary plugging particles exhibit excellent low-temperature degradation and dissolution properties, good dissolution effect under water-deficient conditions, and high plugging strength: the standard solubility and water-deficient solubility of the particles at 60℃ are 80.3% to 96.5% and 71.5% to 90.7%, respectively; the standard solubility and water-deficient solubility at 90℃ are 96.4% to 99.6% and 91.3% to 99.2%, respectively; the plugging strength for 1mm wide fractures is 40 to 50 MPa, and the plugging strength for 2mm wide fractures is 33 to 45 MPa, achieving effective plugging in temporary plugging and diverting fracturing. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the temporary plugging particle skin-core structure of the second composite material provided by the present invention, wherein 1-skin layer, 2-core layer.

[0047] Figure 2 This is a top view of the temporary plugging particles made of the second composite material provided by the present invention.

[0048] Figure 3 This is a cross-sectional view of the temporary plugging particles made of the second composite material provided by the present invention, wherein h is the height of the temporary plugging particle, d2 is the diameter of the temporary plugging particle, d1 is the diameter of the core layer of the temporary plugging particle, and δ is the thickness of the skin layer of the temporary plugging particle. Detailed Implementation

[0049] The present invention will be further described below with reference to the embodiments. However, the embodiments of the present invention are merely illustrative examples and should not be construed as limiting the present invention under any circumstances.

[0050] The 3D printing filament machine used in this invention was purchased from Guangzhou Sanhuiying Machinery Equipment Co., Ltd., model LXSJ45;

[0051] The wire extrusion machine used in this invention was purchased from Dongguan Maoxingsheng Machinery Equipment Co., Ltd., model MXS50.

[0052] Example 1

[0053] The first ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, formed by copolymerizing ethylene-lactide and lactide in a molar ratio of 85:15, with a weight-average molecular weight of 100,000, purchased from Jinan Daigang Bioengineering Co., Ltd., with the brand name LG1585-10.

[0054] The ammonium polyphosphate used in this embodiment was purchased from Dongguan Xingyuan Chemical Co., Ltd., with a degree of polymerization of 1000 to 1200, and the model was XYL1000.

[0055] The second ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average molecular weight of 30,000, an average diameter of 3 mm, and an average height of 3 mm, which is copolymerized from ethylene-lactide and lactide in a molar ratio of 70:30. It was purchased from Jinan Daigang Bioengineering Co., Ltd. and its brand name is LG3070-3.

[0056] Preparation of the first composite material:

[0057] 1) The first ethylene lactide copolymer and ammonium polyphosphate were mixed at a mass ratio of 2:1 and melt-extruded and granulated in a twin-screw granulator at a screw speed of 200 r / min and at 170°C to obtain an intermediate material, which is a cylindrical particle with an average diameter of 3 mm and an average height of 3 mm.

[0058] 2) Set the filament diameter of the 3D printing filament machine to 2mm, and then extrude the intermediate material obtained in step 1) in the 3D printing filament machine at a screw speed of 80r / min and 175℃. After cooling to room temperature (25℃), it is wound up to obtain a cylindrical first composite material with a diameter of 2mm.

[0059] Preparation of the second composite material and temporary plugging particles:

[0060] The second ethylene lactide copolymer was fed into the hopper of an electric wire extruder with a set heating temperature of 125°C as a sheath material. At the same time, the cylindrical first composite material prepared in this embodiment was passed through the wire hole of the electric wire extruder as a core material. The extruder was pulled at a speed of 60 r / min, and the screw speed of the electric wire extruder was controlled at 50 r / min to control the thickness of the sheath to 1 mm. The extruder was cooled to room temperature (25°C) to obtain a second composite material with a core diameter of 2 mm and a sheath thickness of 1 mm.

[0061] The obtained second composite material was pelletized using a pelletizer in a direction perpendicular to the cylindrical axis at a specification of 3 mm, resulting in cylindrical temporary plugging particles of the second composite material with a core diameter of 2 mm and a skin thickness of 1 mm, and a diameter of 4 mm and a height of 3 mm.

[0062] Example 2

[0063] The first ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, which is copolymerized from ethylene-lactide and lactide in a molar ratio of 85:15. It was purchased from Jinan Daigang Bioengineering Co., Ltd. and its brand name is LG1585-8.

[0064] The ammonium polyphosphate used in this embodiment was purchased from Dongguan Xingyuan Chemical Co., Ltd., with a degree of polymerization of 1000 to 1200, and the model was XYL1000.

[0065] The second ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, which is copolymerized from ethylene-lactide and lactide in a molar ratio of 60:40. It was purchased from Jinan Daigang Bioengineering Co., Ltd. and its brand name is LG4060-5.

[0066] Preparation of the first composite material:

[0067] 1) The first ethylene lactide copolymer and ammonium polyphosphate were mixed at a mass ratio of 2:1 and melt-extruded and granulated at 190°C in a twin-screw granulator at a screw speed of 200 r / min to obtain an intermediate material, which is a cylindrical particle with an average diameter of 3 mm and an average height of 3 mm.

[0068] 2) Set the filament diameter of the 3D printing filament machine to 2mm, and then extrude the intermediate material obtained in step 1) in the 3D printing filament machine at a screw speed of 80r / min and 190℃. After cooling to room temperature (25℃), it is wound up to obtain a cylindrical first composite material with a diameter of 2mm.

[0069] Preparation of the second composite material and temporary plugging particles:

[0070] The second ethylene lactide copolymer was fed into the hopper of an electric wire extruder with a set heating temperature of 130°C as a sheath material. At the same time, the cylindrical first composite material prepared in this embodiment was passed through the wire hole of the electric wire extruder as a core material. The extruder was pulled at a speed of 60 m / min, and the screw speed of the electric wire extruder was controlled at 23 r / min to control the thickness of the sheath to be 0.5 mm. The extruder was cooled to room temperature (25°C) to obtain a second composite material with a core diameter of 2 mm and a sheath thickness of 0.5 mm.

[0071] The obtained second composite material was pelletized using a pelletizer in a direction perpendicular to the cylindrical axis at a specification of 3 mm, resulting in cylindrical temporary plugging particles of the second composite material with a core diameter of 2 mm and a skin thickness of 0.5 mm, and a diameter and height of 3 mm.

[0072] Example 3

[0073] The first ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, which is copolymerized from ethylene-lactide and lactide in a molar ratio of 85:15. It was purchased from Jinan Daigang Bioengineering Co., Ltd. and its brand name is LG1585-8.

[0074] The ammonium polyphosphate used in this embodiment was purchased from Dongguan Xingyuan Chemical Co., Ltd., with a degree of polymerization of 1000 to 1200, and the model was XYL1000.

[0075] The second ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, which is copolymerized from ethylene-lactide and lactide in a molar ratio of 60:40. It was purchased from Jinan Daigang Bioengineering Co., Ltd. and its brand name is LG4060-5.

[0076] Preparation of the first composite material:

[0077] 1) The first ethylene lactide copolymer and ammonium polyphosphate were mixed at a mass ratio of 4:1 and melt-extruded and granulated at 180°C in a twin-screw granulator at a screw speed of 200 r / min to obtain an intermediate material, which is a cylindrical particle with an average diameter of 3 mm and an average height of 3 mm.

[0078] 2) Set the filament diameter of the 3D printing filament machine to 1mm, and then extrude the intermediate material obtained in step 1) in the 3D printing filament machine at a screw speed of 80r / min and 180℃. After cooling to room temperature (25℃), it is wound up to obtain a cylindrical first composite material with a diameter of 1mm.

[0079] Preparation of the second composite material and temporary plugging particles:

[0080] The second ethylene lactide copolymer was fed into the hopper of an electric wire extruder with a set heating temperature of 130°C as a sheath material. At the same time, the cylindrical first composite material prepared in this embodiment was passed through the wire hole of the electric wire extruder as a core material. The extruder was pulled at a speed of 60 m / min, and the screw speed of the electric wire extruder was controlled at 30 r / min to control the thickness of the sheath to be 1 mm. After cooling to room temperature, a second composite material with a core diameter of 1 mm and a sheath thickness of 1 mm was obtained.

[0081] The obtained second composite material was pelletized in a direction perpendicular to the cylindrical axis using a pelletizer with a diameter of 3 mm, resulting in cylindrical temporary plugging particles of the second composite material with a core diameter of 1 mm and a skin thickness of 1 mm. The particles had a diameter of 3 mm and a height of 3 mm.

[0082] Example 4

[0083] The first ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, which is copolymerized from ethylene-lactide and lactide in a molar ratio of 85:15. It was purchased from Jinan Daigang Bioengineering Co., Ltd. and its brand name is LG1585-5.

[0084] The ammonium polyphosphate used in this embodiment was purchased from Dongguan Xingyuan Chemical Co., Ltd., with a degree of polymerization of 1000 to 1200, and the model was XYL1000.

[0085] The second ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, which is copolymerized from ethylene-lactide and lactide in a molar ratio of 50:50. It was purchased from Jinan Daigang Bioengineering Co., Ltd. and its brand name is LG5050-5.

[0086] Preparation of the first composite material:

[0087] 1) The first ethylene lactide copolymer and ammonium polyphosphate were mixed at a mass ratio of 4:1 and melt-extruded and granulated at 180°C in a twin-screw granulator at a screw speed of 200 r / min to obtain an intermediate material, which is a cylindrical particle with an average diameter of 3 mm and an average height of 3 mm.

[0088] 2) Set the filament diameter of the 3D printing filament machine to 1.5mm, and then extrude the intermediate material obtained in step 1) in the 3D printing filament machine at a screw speed of 80r / min and 180℃. After cooling to room temperature (25℃), it is wound up to obtain a cylindrical first composite material with a diameter of 1.5mm.

[0089] Preparation of the second composite material and temporary plugging particles:

[0090] The second ethylene lactide copolymer was fed into the hopper of an electric wire extruder with a set heating temperature of 120°C as a sheath material. At the same time, the cylindrical first composite material prepared in this embodiment was passed through the wire hole of the electric wire extruder as a core material. The extruder was pulled at a speed of 60 m / min, and the screw speed of the electric wire extruder was controlled at 40 r / min to control the thickness of the sheath to 1 mm. The extruder was cooled to room temperature at 40 r / min to obtain a second composite material with a core diameter of 1.5 mm and a sheath thickness of 1 mm.

[0091] The obtained second composite material was pelletized using a pelletizer in a direction perpendicular to the cylindrical axis at a specification of 3 mm, resulting in cylindrical temporary plugging particles of the second composite material with a core diameter of 1.5 mm and a skin thickness of 1 mm. The particles had a diameter of 3.5 mm and a height of 3 mm.

[0092] Example 5

[0093] The first ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, which is copolymerized from ethylene-lactide and lactide in a molar ratio of 85:15. It was purchased from Jinan Daigang Bioengineering Co., Ltd. and its brand name is LG1585-8.

[0094] The ammonium polyphosphate used in this embodiment was purchased from Dongguan Xingyuan Chemical Co., Ltd., with a degree of polymerization of 1000 to 1200, and the model was XYL1000.

[0095] The second ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, which is copolymerized from ethylene-lactide and lactide in a molar ratio of 40:60. It was purchased from Jinan Daigang Bioengineering Co., Ltd. and its brand name is LG6040-5.

[0096] Preparation of the first composite material:

[0097] 1) The first ethylene lactide copolymer and ammonium polyphosphate were mixed at a mass ratio of 4:1 and melt-extruded and granulated in a twin-screw granulator at a screw speed of 200 r / min and at 175°C to obtain an intermediate material, which is a cylindrical particle with an average diameter of 3 mm and an average height of 3 mm.

[0098] 2) Set the filament diameter of the 3D printing filament machine to 1.5mm, and then extrude the intermediate material obtained in step 1) in the 3D printing filament machine at a screw speed of 80r / min and 180℃. After cooling to room temperature (25℃), it is wound up to obtain a cylindrical first composite material with a diameter of 1.5mm.

[0099] Preparation of the second composite material and temporary plugging particles:

[0100] The second ethylene lactide copolymer was fed into the hopper of an electric wire extruder with a set heating temperature of 130°C as a sheath material. At the same time, the cylindrical first composite material prepared in this embodiment was passed through the wire hole of the electric wire extruder as a core material. The extruder was pulled at a speed of 60 m / min, and the screw speed of the electric wire extruder was controlled at 40 r / min to control the thickness of the sheath to 1 mm. The extruder was cooled to room temperature (25°C) to obtain a second composite material with a core diameter of 1.5 mm and a sheath thickness of 1 mm.

[0101] The obtained second composite material was pelletized using a pelletizer in a direction perpendicular to the cylindrical axis at a specification of 3 mm, resulting in cylindrical temporary plugging particles of the second composite material with a core diameter of 1.5 mm and a skin thickness of 1 mm. The particles had a diameter of 3.5 mm and a height of 3 mm.

[0102] Example 6

[0103] The first ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, which is copolymerized from ethylene-lactide and lactide in a molar ratio of 85:15. It was purchased from Jinan Daigang Bioengineering Co., Ltd. and its brand name is LG1585-8.

[0104] The ammonium polyphosphate used in this embodiment was purchased from Dongguan Xingyuan Chemical Co., Ltd., with a degree of polymerization of 1000 to 1200, and the model was XYL1000.

[0105] The second ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, which is copolymerized from ethylene-lactide and lactide in a molar ratio of 50:50. It was purchased from Jinan Daigang Bioengineering Co., Ltd. and its brand name is LG5050-5.

[0106] Preparation of the first composite material:

[0107] 1) The first ethylene lactide copolymer and ammonium polyphosphate were mixed at a mass ratio of 4:1 and melt-extruded and granulated in a twin-screw granulator at a screw speed of 200 r / min and at 175°C to obtain an intermediate material, which is a cylindrical particle with an average diameter of 3 mm and an average height of 3 mm.

[0108] 2) Set the filament diameter of the 3D printing filament machine to 1.5mm, and then extrude the intermediate material obtained in step 1) in the 3D printing filament machine at a screw speed of 80r / min and 175℃. After cooling to room temperature (25℃), it is wound up to obtain a cylindrical first composite material with a diameter of 1.5mm.

[0109] Preparation of the second composite material and temporary plugging particles:

[0110] The second ethylene lactide copolymer was fed into the hopper of an electric wire extruder with a set heating temperature of 120°C as a sheath material. At the same time, the cylindrical first composite material prepared in this embodiment was passed through the wire hole of the electric wire extruder as a core material. The extruder was pulled at a speed of 60 m / min, and the screw speed of the electric wire extruder was controlled at 30.5 r / min to control the thickness of the sheath to 0.8 mm. The extruder was cooled to room temperature (25°C) to obtain a second composite material with a core diameter of 1.5 mm and a sheath thickness of 0.8 mm.

[0111] The obtained second composite material was pelletized using a pelletizer in a direction perpendicular to the cylindrical axis at a specification of 3 mm, resulting in cylindrical temporary plugging particles of the second composite material with a core diameter of 1.5 mm and a skin thickness of 0.8 mm, and a diameter of 3.1 mm and a height of 3 mm.

[0112] Example 7

[0113] The first ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, which is copolymerized from ethylene-lactide and lactide in a molar ratio of 85:15. It was purchased from Jinan Daigang Bioengineering Co., Ltd. and its brand name is LG1585-8.

[0114] The ammonium polyphosphate used in this embodiment was purchased from Dongguan Xingyuan Chemical Co., Ltd., with a degree of polymerization of 1000 to 1200, and the model was XYL1000.

[0115] The second ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, which is copolymerized from ethylene-lactide and lactide in a molar ratio of 50:50. It was purchased from Jinan Daigang Bioengineering Co., Ltd. and its brand name is LG5050-5.

[0116] Preparation of the first composite material:

[0117] 1) The first ethylene lactide copolymer and ammonium polyphosphate were mixed at a mass ratio of 3:1 and melt-extruded and granulated at 175°C in a twin-screw granulator at a screw speed of 200 r / min to obtain an intermediate material, which is a cylindrical particle with an average diameter of 3 mm and an average height of 3 mm.

[0118] 2) Set the filament diameter of the 3D printing filament machine to 1.5mm, and then extrude the intermediate material obtained in step 1) in the 3D printing filament machine at a screw speed of 80r / min and 175℃. After cooling to room temperature (25℃), it is wound up to obtain a cylindrical first composite material with a diameter of 1.5mm.

[0119] Preparation of the second composite material and temporary plugging particles:

[0120] The second ethylene lactide copolymer was fed into the hopper of an electric wire extruder with a set heating temperature of 120°C as a sheath material. At the same time, the cylindrical first composite material prepared in this embodiment was passed through the wire hole of the electric wire extruder as a core material. The extruder was pulled at a speed of 60 m / min, and the screw speed of the electric wire extruder was controlled at 30.5 r / min to control the thickness of the sheath to 0.8 mm. The extruder was cooled to room temperature (25°C) to obtain a second composite material with a core diameter of 1.5 mm and a sheath thickness of 0.8 mm.

[0121] The obtained second composite material was pelletized using a pelletizer in a direction perpendicular to the cylindrical axis at a specification of 3 mm, resulting in cylindrical temporary plugging particles of the second composite material with a core diameter of 1.5 mm and a skin thickness of 0.8 mm, and a diameter of 3.1 mm and a height of 3 mm.

[0122] Example 8

[0123] The first ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, which is copolymerized from ethylene-lactide and lactide in a molar ratio of 85:15. It was purchased from Jinan Daigang Bioengineering Co., Ltd. and its brand name is LG1585-8.

[0124] The ammonium polyphosphate used in this embodiment was purchased from Dongguan Xingyuan Chemical Co., Ltd., with a degree of polymerization of 1000 to 1200, and the model was XYL1000.

[0125] The second ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, which is copolymerized from ethylene-lactide and lactide in a molar ratio of 50:50. It was purchased from Jinan Daigang Bioengineering Co., Ltd. and its brand name is LG5050-5.

[0126] Preparation of the first composite material:

[0127] 1) The first ethylene lactide copolymer and ammonium polyphosphate were mixed at a mass ratio of 4:1 and melt-extruded and granulated in a twin-screw granulator at a screw speed of 200 r / min and at 175°C to obtain an intermediate material, which is a cylindrical particle with an average diameter of 3 mm and an average height of 3 mm.

[0128] 2) Set the filament diameter of the 3D printing filament machine to 1.5mm, and then extrude the intermediate material obtained in step 1) in the 3D printing filament machine at a screw speed of 80r / min and 175℃. After cooling to room temperature (25℃), it is wound up to obtain a cylindrical first composite material with a diameter of 1.5mm.

[0129] Preparation of the second composite material and temporary plugging particles:

[0130] The second ethylene lactide copolymer was fed into the hopper of an electric wire extruder with a set heating temperature of 120°C as a sheath material. At the same time, the cylindrical first composite material prepared in this embodiment was passed through the wire hole of the electric wire extruder as a core material. The extruder was pulled at a speed of 60 m / min, and the screw speed of the electric wire extruder was controlled at 30.5 r / min to control the thickness of the sheath to 0.8 mm. The extruder was cooled to room temperature (25°C) to obtain a second composite material with a core diameter of 1.5 mm and a sheath thickness of 0.8 mm.

[0131] The obtained second composite material was pelletized using a pelletizer in a direction perpendicular to the cylindrical axis at a specification of 5 mm, resulting in cylindrical temporary plugging particles of the second composite material with a core diameter of 1.5 mm and a skin thickness of 0.8 mm, and a diameter of 3.1 mm and a height of 5 mm.

[0132] Example 9

[0133] The first ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, formed by copolymerizing ethylene-lactide and lactide in a molar ratio of 85:15, with a weight-average molecular weight of 100,000, purchased from Jinan Daigang Bioengineering Co., Ltd., with the brand name LG1585-10.

[0134] The ammonium polyphosphate used in this embodiment was purchased from Dongguan Xingyuan Chemical Co., Ltd., with a degree of polymerization of 1000 to 1200, and the model was XYL1000.

[0135] The second ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, which is copolymerized from ethylene-lactide and lactide in a molar ratio of 50:50. It was purchased from Jinan Daigang Bioengineering Co., Ltd. and its brand name is LG5050-5.

[0136] Preparation of the first composite material:

[0137] 1) The first ethylene lactide copolymer and ammonium polyphosphate were mixed at a mass ratio of 4:1 and melt-extruded and granulated in a twin-screw granulator at a screw speed of 200 r / min and at 175°C to obtain an intermediate material, which is a cylindrical particle with an average diameter of 3 mm and an average height of 3 mm.

[0138] 2) Set the filament diameter of the 3D printing filament machine to 1.5mm, and then extrude the intermediate material obtained in step 1) in the 3D printing filament machine at a screw speed of 80r / min and 175℃. After cooling to room temperature (25℃), it is wound up to obtain a cylindrical first composite material with a diameter of 1.5mm.

[0139] Preparation of the second composite material and temporary plugging particles:

[0140] The second ethylene lactide copolymer was fed into the hopper of an electric wire extruder with a set heating temperature of 120°C as a sheath material. At the same time, the cylindrical first composite material prepared in this embodiment was passed through the wire hole of the electric wire extruder as a core material. The extruder was pulled at a speed of 60 m / min, and the screw speed of the electric wire extruder was controlled at 17.5 r / min to control the thickness of the sheath to 0.5 mm. The extruder was cooled to room temperature (25°C) to obtain a second composite material with a core diameter of 1.5 mm and a sheath thickness of 0.5 mm.

[0141] The obtained second composite material was pelletized using a pelletizer in a direction perpendicular to the cylindrical axis at a specification of 3 mm, resulting in cylindrical temporary plugging particles of the second composite material with a core diameter of 1.5 mm and a skin thickness of 0.5 mm, and a diameter of 2.5 mm and a height of 3 mm.

[0142] Example 10

[0143] The first ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, which is copolymerized from ethylene-lactide and lactide in a molar ratio of 85:15. It was purchased from Jinan Daigang Bioengineering Co., Ltd. and its brand name is LG1585-8.

[0144] The ammonium polyphosphate used in this embodiment was purchased from Dongguan Xingyuan Chemical Co., Ltd., with a degree of polymerization of 1000 to 1200, and the model was XYL1000.

[0145] The second ethylene-lactide copolymer used in this embodiment is a regular cylindrical particle with an average diameter of 3 mm and an average height of 3 mm, which is copolymerized from ethylene-lactide and lactide in a molar ratio of 30:70. It was purchased from Jinan Daigang Bioengineering Co., Ltd. and its brand name is LG7030-5.

[0146] Preparation of the first composite material:

[0147] 1) The first ethylene lactide copolymer and ammonium polyphosphate were mixed at a mass ratio of 4:1 and melt-extruded and granulated in a twin-screw granulator at a screw speed of 200 r / min and at 175°C to obtain an intermediate material, which is a cylindrical particle with an average diameter of 3 mm and an average height of 3 mm.

[0148] 2) Set the filament diameter of the 3D printing filament machine to 1.5mm, and then extrude the intermediate material obtained in step 1) in the 3D printing filament machine at a screw speed of 80r / min and 175℃. After cooling to room temperature (25℃), it is wound up to obtain a cylindrical first composite material with a diameter of 1.5mm.

[0149] Preparation of the second composite material and temporary plugging particles:

[0150] The second ethylene lactide copolymer was fed into the hopper of an electric wire extruder with a set heating temperature of 120°C as a sheath material. At the same time, the cylindrical first composite material prepared in this embodiment was passed through the wire hole of the electric wire extruder as a core material. The extruder was pulled at a speed of 60 m / min, and the screw speed of the electric wire extruder was controlled at 30.5 r / min to control the thickness of the sheath to 0.8 mm. The extruder was cooled to room temperature (25°C) to obtain a second composite material with a core diameter of 1.5 mm and a sheath thickness of 0.8 mm.

[0151] The obtained second composite material was pelletized using a pelletizer in a direction perpendicular to the cylindrical axis at a specification of 3 mm, resulting in cylindrical temporary plugging particles of the second composite material with a core diameter of 1.5 mm and a skin thickness of 0.8 mm, and a diameter of 3.1 mm and a height of 3 mm.

[0152] Comparative Example 1

[0153] The first copolymer of ethylene-lactide used in this comparative example: regular cylindrical particles with an average diameter of 3 mm and an average height of 3 mm, formed by copolymerizing ethylene-lactide and lactide in a molar ratio of 90:10, with a weight-average molecular weight of 100,000, were purchased from Jinan Daigang Bioengineering Co., Ltd., with the brand name LG1090-10.

[0154] The ammonium polyphosphate used in this comparative example was purchased from Dongguan Xingyuan Chemical Co., Ltd., with a degree of polymerization of 1000 to 1200 and a model number of XYL1000.

[0155] The second ethylene-lactide copolymer used in this comparative example: regular cylindrical particles with an average diameter of 3 mm and an average height of 3 mm, formed by copolymerizing ethylene-lactide and lactide in a molar ratio of 50:50, with a weight-average molecular weight of 50,000, were purchased from Jinan Daigang Bioengineering Co., Ltd., with the brand name LG5050-5.

[0156] Preparation of the first composite material:

[0157] 1) The first ethylene lactide copolymer and ammonium polyphosphate were mixed at a mass ratio of 4:1 and melt-extruded and granulated in a twin-screw granulator at a screw speed of 200 r / min and at 190°C to obtain an intermediate material, which is a cylindrical particle with an average diameter of 3 mm and an average height of 3 mm.

[0158] 2) Set the filament diameter of the 3D printing filament machine to 1.5mm, and then extrude the intermediate material obtained in step 1) in the 3D printing filament machine at a screw speed of 80r / min and 190℃. After cooling to room temperature (25℃), it is wound up to obtain a cylindrical first composite material with a diameter of 1.5mm.

[0159] Preparation of the second composite material and temporary plugging particles:

[0160] The second ethylene lactide copolymer was fed into the hopper of an electric wire extruder with a set heating temperature of 120°C as a sheath material. At the same time, the cylindrical first composite material prepared in this comparative example was passed through the wire hole of the electric wire extruder as a core material. The extruder was pulled at a speed of 60 m / min, and the screw speed of the electric wire extruder was controlled at 30.4 r / min to control the thickness of the sheath to 0.8 mm. After cooling to room temperature (25°C), a second composite material with a core diameter of 1.5 mm and a sheath thickness of 0.8 mm was obtained.

[0161] The obtained second composite material was pelletized using a pelletizer in a direction perpendicular to the cylindrical axis at a specification of 5 mm, resulting in cylindrical temporary plugging particles of the second composite material with a core diameter of 1.5 mm and a skin thickness of 0.8 mm, and a diameter of 3.1 mm and a height of 5 mm.

[0162] Comparative Example 2

[0163] The first copolymer of ethylene-lactide used in this comparative example: regular cylindrical particles with an average diameter of 3 mm and an average height of 3 mm, formed by copolymerizing ethylene-lactide and lactide in a molar ratio of 80:20, with a weight-average molecular weight of 100,000, were purchased from Jinan Daigang Bioengineering Co., Ltd., with the brand name LG2080-10.

[0164] The ammonium polyphosphate used in this comparative example was purchased from Dongguan Xingyuan Chemical Co., Ltd., with a degree of polymerization of 1000 to 1200 and a model number of XYL1000.

[0165] The second ethylene-lactide copolymer used in this comparative example: regular cylindrical particles with an average diameter of 3 mm and an average height of 3 mm, formed by copolymerizing ethylene-lactide and lactide in a molar ratio of 50:50, with a weight-average molecular weight of 50,000, were purchased from Jinan Daigang Bioengineering Co., Ltd., with the brand name LG5050-5.

[0166] Preparation of the first composite material:

[0167] 1) The first ethylene lactide copolymer and ammonium polyphosphate were mixed at a mass ratio of 4:1 and melt-extruded and granulated in a twin-screw granulator at a screw speed of 200 r / min and at 175°C to obtain an intermediate material, which is a cylindrical particle with an average diameter of 3 mm and an average height of 3 mm.

[0168] 2) Set the filament diameter of the 3D printing filament machine to 1.5mm, and then extrude the intermediate material obtained in step 1) in the 3D printing filament machine at a screw speed of 80r / min and 190℃. After cooling to room temperature (25℃), it is wound up to obtain a cylindrical first composite material with a diameter of 1.5mm.

[0169] Preparation of the second composite material and temporary plugging particles:

[0170] The second ethylene lactide copolymer was fed into the hopper of an electric wire extruder with a set heating temperature of 110°C as a skin material. At the same time, the cylindrical first composite material prepared in this comparative example was passed through the wire extruder's threading hole as a core material. The extruder was pulled at a speed of 60 m / min, while the screw speed of the electric wire extruder was controlled at 30.5 r / min. However, because the core material was not heat-resistant, it could not form effective traction, and the second composite material with a skin-core structure could not be obtained, nor could temporary plugging particles be obtained.

[0171] Comparative Example 3

[0172] The first copolymer of ethylene-lactide used in this comparative example: regular cylindrical particles with an average diameter of 3 mm and an average height of 3 mm, formed by copolymerizing ethylene-lactide and lactide in a molar ratio of 85:15, with a weight-average molecular weight of 80,000, were purchased from Jinan Daigang Bioengineering Co., Ltd., with the brand name LG1585-8.

[0173] The nucleating agent used in this comparative example was TMC-300, purchased from Shanxi Provincial Chemical Research Institute Co., Ltd.

[0174] The second ethylene-lactide copolymer used in this comparative example: regular cylindrical particles with an average diameter of 3 mm and an average height of 3 mm, formed by copolymerizing ethylene-lactide and lactide in a molar ratio of 50:50, with a weight-average molecular weight of 50,000, were purchased from Jinan Daigang Bioengineering Co., Ltd., with the brand name LG5050-5.

[0175] Preparation of the first composite material:

[0176] 1) The first ethylene lactide copolymer and the nucleating agent were mixed at a mass ratio of 99:1 and melt-extruded and granulated in a twin-screw granulator at a screw speed of 200 r / min and at 175°C to obtain an intermediate material, which is a cylindrical particle with an average diameter of 3 mm and an average height of 3 mm.

[0177] 2) Set the filament diameter of the 3D printing filament machine to 1.5mm, and then extrude the intermediate material obtained in step 1) in the 3D printing filament machine at a screw speed of 80r / min and 175℃. After cooling to room temperature (25℃), it is wound up to obtain a cylindrical first composite material with a diameter of 1.5mm.

[0178] Preparation of the second composite material and temporary plugging particles:

[0179] The second ethylene lactide copolymer was fed into the hopper of an electric wire extruder with a set heating temperature of 120°C as a sheath material. At the same time, the cylindrical first composite material prepared in this comparative example was passed through the wire hole of the electric wire extruder as a core material. The extruder was pulled at a speed of 60 m / min, and the screw speed of the electric wire extruder was controlled at 30.5 r / min to control the thickness of the sheath to 0.8 mm. After cooling to room temperature (25°C), a second composite material with a core diameter of 1.5 mm and a sheath thickness of 0.8 mm was obtained.

[0180] The obtained second composite material was pelletized using a pelletizer in a direction perpendicular to the cylindrical axis at a specification of 3 mm, resulting in cylindrical temporary plugging particles of the second composite material with a core diameter of 1.5 mm and a skin thickness of 0.8 mm, and a diameter of 3.1 mm and a height of 3 mm.

[0181] Comparative Example 4

[0182] The first copolymer of ethylene-lactide used in this comparative example: regular cylindrical particles with an average diameter of 3 mm and an average height of 3 mm, formed by copolymerizing ethylene-lactide and lactide in a molar ratio of 85:15, with a weight-average molecular weight of 80,000, were purchased from Jinan Daigang Bioengineering Co., Ltd., with the brand name LG1585-8.

[0183] The ammonium polyphosphate used in this comparative example was purchased from Dongguan Xingyuan Chemical Co., Ltd., with a degree of polymerization of 20 to 100 and a model of XYL70.

[0184] The second ethylene-lactide copolymer used in this comparative example: regular cylindrical particles with an average diameter of 3 mm and an average height of 3 mm, formed by copolymerizing ethylene-lactide and lactide in a molar ratio of 50:50, with a weight-average molecular weight of 50,000, were purchased from Jinan Daigang Bioengineering Co., Ltd., with the brand name LG5050-5.

[0185] Preparation of the first composite material:

[0186] 1) The first ethylene lactide copolymer and ammonium polyphosphate were mixed at a mass ratio of 4:1 and melt-extruded and granulated in a twin-screw granulator at a screw speed of 200 r / min and at 175°C to obtain an intermediate material, which is a cylindrical particle with an average diameter of 3 mm and an average height of 3 mm.

[0187] 2) Set the filament diameter of the 3D printing filament machine to 1.5mm, and then extrude the intermediate material obtained in step 1) in the 3D printing filament machine at a screw speed of 80r / min and 175℃. After cooling to room temperature (25℃), it is wound up to obtain a cylindrical first composite material with a diameter of 1.5mm. However, the first composite material is prone to breakage during the winding process.

[0188] Preparation of the second composite material and temporary plugging particles:

[0189] The second ethylene lactide copolymer was fed into the hopper of an electric wire extruder with a set heating temperature of 120°C as a sheath material. At the same time, the cylindrical first composite material prepared in this comparative example was passed through the wire hole of the electric wire extruder as a core material. The extruder was pulled at a speed of 60 m / min, and the screw speed of the electric wire extruder was controlled at 30.5 r / min to control the thickness of the sheath to 0.8 mm. After cooling to room temperature (25°C), a second composite material with a core diameter of 1.5 mm and a sheath thickness of 0.8 mm was obtained.

[0190] The obtained second composite material was pelletized using a pelletizer in a direction perpendicular to the cylindrical axis at a specification of 3 mm, resulting in cylindrical temporary plugging particles of the second composite material with a core diameter of 1.5 mm and a skin thickness of 0.8 mm, and a diameter of 3.1 mm and a height of 3 mm.

[0191] Comparative Example 5

[0192] The first copolymer of ethylene-lactide used in this comparative example: regular cylindrical particles with an average diameter of 3 mm and an average height of 3 mm, formed by copolymerizing ethylene-lactide and lactide in a molar ratio of 85:15, with a weight-average molecular weight of 80,000, were purchased from Jinan Daigang Bioengineering Co., Ltd., with the brand name LG1585-8.

[0193] The second ethylene-lactide copolymer used in this comparative example: regular cylindrical particles with an average diameter of 3 mm and an average height of 3 mm, formed by copolymerizing ethylene-lactide and lactide in a molar ratio of 50:50, with a weight-average molecular weight of 50,000, were purchased from Jinan Daigang Bioengineering Co., Ltd., with the brand name LG5050-5.

[0194] Preparation of the first composite material:

[0195] 1) Set the filament diameter of the 3D printing filament machine to 1.5 mm, and then extrude the first ethylene lactide copolymer in the 3D printing filament machine at a screw speed of 80 r / min and 175°C. After cooling to room temperature (25°C), it is wound up to obtain a cylindrical first composite material with a diameter of 1.5 mm.

[0196] Preparation of the second composite material and temporary plugging particles:

[0197] The second ethylene lactide copolymer was fed into the hopper of an electric wire extruder with a set heating temperature of 120°C as a skin material. At the same time, the cylindrical first composite material prepared in this comparative example was passed through the wire extruder hole as a core material. However, because the core material was not heat-resistant (possibly because a crystalline core material was not obtained), it could not form effective traction, and the second composite material with a skin-core structure could not be obtained, nor could temporary plugging particles be obtained.

[0198] Comparative Example 6

[0199] The first copolymer of ethylene-lactide used in this comparative example: regular cylindrical particles with an average diameter of 3 mm and an average height of 3 mm, formed by copolymerizing ethylene-lactide and lactide in a molar ratio of 85:15, with a weight-average molecular weight of 80,000, were purchased from Jinan Daigang Bioengineering Co., Ltd., with the brand name LG1585-8.

[0200] The second ethylene-lactide copolymer used in this comparative example: regular cylindrical particles with an average diameter of 3 mm and an average height of 3 mm, formed by copolymerizing ethylene-lactide and lactide in a molar ratio of 50:50, with a weight-average molecular weight of 50,000, were purchased from Jinan Daigang Bioengineering Co., Ltd., with the brand name LG5050-5.

[0201] Preparation of temporary plugging particles:

[0202] The first ethylene-lactide copolymer particles and the second ethylene-lactide copolymer particles are mixed evenly in a glass beaker at a mass ratio of 1:1 to obtain temporary plugging particles.

[0203] Comparative Example 7

[0204] The soluble acrylic resin irregular particles used in this comparative example: with a particle size of 5 to 80 mesh, were purchased from Shandong Nengju Chemical Co., Ltd., and the grade was GPAA-R-5.

[0205] The copolymer-grade polyacrylamide irregular particles used in this comparative example: with a particle size of 5 to 80 mesh, were purchased from Shanghai Zhenzhun Biotechnology Co., Ltd., brand name AML5-80;

[0206] Preparation of temporary plugging particles:

[0207] Take soluble acrylic resin irregular particles and copolymer grade polyacrylamide irregular particles and mix them evenly in a glass beaker at a mass ratio of 1:1 to obtain temporary plugging particles.

[0208] Comparative Example 8

[0209] The polylactic acid irregular particles used in this comparative example: with a particle size of 5 to 80 mesh, were purchased from Zhejiang Hisun Biomaterials Co., Ltd., with the grade LA221-5-80.

[0210] Irregular polylactic acid particles were used directly as temporary plugging particles.

[0211] The structure of the second composite material and the temporarily plugging particles obtained by pelletizing it

[0212] The second composite materials prepared in Examples 1 to 10 and Comparative Examples 1, 3, and 4 have a core-skin structure. The temporary plugging particles are obtained by physically cutting the second composite material in a direction perpendicular to the cylinder axis, and also have the same core-skin structure as the second composite material. Figure 1 A schematic diagram of the core-skin structure of the temporarily plugging particles. Figure 2 A top view of the temporarily blocked particles. Figure 3 This is a cross-sectional view of the temporarily plugging particles. Figures 1 to 3 In the diagram, 1 represents the cortex and 2 represents the core. Figure 3 In this context, h represents the height of the temporary plugging particle, d2 represents the diameter of the temporary plugging particle, d1 represents the diameter of the core layer in the skin-core structure of the temporary plugging particle, and δ represents the thickness of the skin layer in the skin-core structure of the temporary plugging particle. Combined with... Figures 1 to 3 As can be seen, the temporarily plugging particles are cylindrical, and a skin layer of a certain thickness wraps around the core layer, which is also cylindrical, to form a skin-core structure.

[0213] Performance evaluation of temporary plugging particles

[0214] 1. Determination of the sealing strength of temporary plugging particles

[0215] The DV-IV type temporary plugging agent pressure-bearing capacity evaluation instrument produced by Jiangsu Huaan Scientific Instruments Co., Ltd. was used to determine the plugging strength of the temporary plugging particles prepared in Examples 1 to 10 and Comparative Examples 1 to 8, according to standard Q / SH CG0152-2021, to evaluate the pressure-bearing capacity of the temporary plugging particles. The organic boron crosslinking agent used in this experiment was purchased from Dongying Shipuri Petroleum Engineering Technology Co., Ltd., model "Guar gum fracturing fluid crosslinking agent 60℃", conforming to standard Q / SHCG0128.

[0216] The specific measurement steps are as follows:

[0217] i. Preparation of guar gum base solution: Measure 1000mL of distilled water and pour it into the sample cup of the Wu Yin mixer, then add 4.0g of hydroxypropyl guar gum; then set the Wu Yin mixer to the "low speed" setting, adjust the voltage to 55V, stir for 5min and pour into a beaker; then add 3.0g of sodium carbonate to the sample cup of the Wu Yin mixer, then pour the solution into a wide-mouth bottle, cover it, and place it in a 30℃ water bath for 4h to obtain the guar gum base solution. The mass of the guar gum base solution is 100%. The guar gum base solution contains 0.4wt% hydroxypropyl guar gum, 0.3wt% sodium carbonate and the balance water.

[0218] ii. Preparation of gel containing temporarily blocking particles: Weigh 1000 mL of the guar gum base solution prepared in step i into a beaker using a graduated cylinder, and then add the gel at 200 kg / m³. 3 Add 200g of temporary plugging particles to 1000mL of guar gum base solution, mix and stir evenly, then add 0.5wt% of an organoboron crosslinking agent based on the mass of hydroxypropyl guar gum in the guar gum base solution, and react at room temperature to form a gel containing temporary plugging particles.

[0219] iii. Set the outlet width of the wedge-shaped steel core fracture plate to 1 mm, insert the core holder, connect the holder to the intermediate container, and heat the core holder to 60°C. Then, place the gel containing the temporary plugging agent into the 1000 mL intermediate container. Open the connecting valve of the intermediate container, start the horizontal flow pump, set the pump flow rate to 40 mL / min, and the pressure limit to 5 MPa. Conduct a displacement experiment, observe and record the pressure rise after temporary plugging. If the pressure rise after temporary plugging reaches 5 MPa and remains stable for 1 hour or more, the pressure-bearing capacity of the temporary plugging particles in sealing a 1 mm wide crack is considered qualified.

[0220] iv. Based on the displacement experiment conducted in step iii, increase the displacement of the advection pump. Gradually increase the displacement within the range of 40 mL / min to 100 mL / min (specifically, starting from a displacement of 40 mL / min, increase the displacement by 10 mL / min every 10 min to 100 mL / min) to conduct the displacement experiment. Within the rated maximum pressure range of the advection pump, observe and record the rise in displacement pressure after temporary plugging. When the pressure rises to a certain value, the pressure drops rapidly. The maximum pressure at this point is the plugging strength of the temporary plugging particles under the condition that the crack width is 1 mm.

[0221] v. Set the outlet width of the wedge-shaped steel core fracture plate to 2mm. Perform the displacement test according to the same operation as in step iii. Observe and record the pressure rise after temporary plugging. When the pressure rise after temporary plugging reaches 5MPa and remains stable for 1 hour or more, the pressure bearing capacity of the temporary plugging particles to seal the 2mm wide crack is considered to be qualified.

[0222] Based on the displacement experiment conducted in step v, the sealing strength of the temporary plugging particles was determined under the condition that the crack width was 2 mm, following the same procedure as in step iv.

[0223] Following the above method, the plugging strength of the temporary plugging particles prepared in Examples 1 to 10 and Comparative Examples 1 to 8 was measured when they plugged cracks with widths of 1 mm and 2 mm. The specific results are shown in Table 1. In the table, " / " indicates that the test could not be conducted or that no temporary plugging particles were prepared for the test.

[0224] Table 1. Pressure-bearing capacity of temporary plugging particles

[0225]

[0226]

[0227] As can be seen from the data in Table 1, the temporary plugging particles made of the second composite material prepared in Examples 1 to 10 have a sealing strength of 40 to 50 MPa for 1 mm wide cracks and a sealing strength of 33 to 45 MPa for 2 mm wide cracks, showing good sealing effects. Among them, the temporary plugging particles made of the second composite material prepared in Example 6 have a sealing strength of 50 MPa for 1 mm wide cracks and a sealing strength of 44 MPa for 2 mm wide cracks, showing the best sealing effect, which proves that the temporary plugging particles made of the second composite material prepared in Examples 1 to 10 have excellent sealing and pressure-bearing performance. The sealing strength of the temporary plugging particles prepared in Comparative Examples 4, 6, 7, and 8 for 1 mm wide cracks was 16 MPa, 25 MPa, 12 MPa, and 26 MPa, respectively. The sealing strength of the temporary plugging particles prepared in Comparative Examples 4, 6, and 8 for 2 mm wide cracks was 11 MPa, 12 MPa, and 14 MPa, respectively. Because the gel containing the temporary plugging particles prepared in Comparative Example 7 was too thin and leaked directly, the 2 mm crack plate could not be pressurized during the experiment. Therefore, it was impossible to determine its sealing strength for 2 mm wide cracks. It can be seen that the sealing strength of Comparative Examples 4, 6, 7, and 8 was significantly low, and their pressure-bearing capacity was poor or even almost non-existent. From the preparation steps and processes, in Comparative Example 4, the core material in the second composite material was prepared from a first composite material obtained by combining ammonium polyphosphate with a polymerization degree of 20 to 100 and a copolymer of first ethylene lactide. The low polymerization degree of the ammonium polyphosphate caused the first composite material to break easily during winding. Comparative Example 6 did not prepare the plugging particles of the second composite material according to the method provided by this invention; instead, it simply physically mixed the first and second ethylene lactide copolymers to obtain the plugging particles. Comparative Example 7 also did not use the method provided by this invention; instead, it simply physically mixed soluble acrylic resin irregular particles and copolymer-grade polyacrylamide irregular particles to obtain the plugging particles. Comparative Example 8 directly used polylactic acid irregular particles as plugging particles. The above demonstrates that the polymerization degree of the ammonium polyphosphate used in preparing the first composite material affects its strength; the polymerization degree of the ammonium polyphosphate, the steps in preparing the first and second composite materials, and the types of raw materials used all affect the compressive strength of the resulting plugging particles.In both Comparative Examples 2 and 5, the first composite material was not heat-resistant and could not be processed to obtain the second composite material, thus failing to produce temporary plugging particles. From the raw materials used and the preparation process, the copolymer molar ratio of glycolide and lactide in the first glycolide-lactide copolymer used in Comparative Example 2 differed from that in Examples 1 to 10. The first composite material prepared in Comparative Example 5 did not contain ammonium polyphosphate, and the first composite material was not prepared according to the preparation method provided by this invention. The inventors believe that the first composite material prepared in Comparative Example 5 may not have reached a crystalline state, thus affecting its heat resistance. Comparative Examples 2 and 5 demonstrate that ammonium polyphosphate is beneficial for enhancing the heat resistance of the first composite material. The copolymer molar ratio of glycolide and lactide in the first glycolide-lactide copolymer and the preparation steps all affect the performance of the first composite material, thereby affecting the preparation of the second composite material using the first composite material as the core material, and ultimately affecting the preparation of the temporary plugging particles.

[0228] 2. Determination of the dissolution rate of temporarily plugging particles

[0229] The standard solubility and water-deficient solubility of the temporary plugging particles prepared in Examples 1 to 10 and Comparative Examples 1 to 8 were determined at different temperatures. The experimental procedures are as follows:

[0230] A. Determination of the standard solubility of temporarily blocked particles at different temperatures

[0231] (1) Set the temperature of the constant temperature drying oven to 105℃, dry the filter paper used in the experiment to constant weight, and record it as m1 (accurate to 0.0001g);

[0232] (2) Weigh 2g (accurate to 0.0001g) of temporary plugging particles using an electronic balance and record it as m2; add the weighed temporary plugging particles into a wide-mouth bottle containing 200mL of distilled water and stir evenly; place the wide-mouth bottle containing the temporary plugging particles and distilled water into an oven with the temperature set to the experimental temperature, keep it at a constant temperature for 72h, and then stop heating.

[0233] (3) Open the wide-mouth bottle, filter the mixture in the wide-mouth bottle with rapid qualitative filter paper, rinse the filter residue with 100mL of distilled water, and then place the filter paper and filter residue in an oven at 105℃ to dry to constant weight, and record it as m3;

[0234] (4) Calculate the standard solubility of the temporarily plugging particles;

[0235] The experimental temperatures in step (2) are 60℃ and 90℃.

[0236] Following steps (1), (2), (3), and (4), the standard solubility of the temporary plugging particles prepared in Examples 1 to 10 and Comparative Examples 1 to 8 was determined. During the standard solubility determination of each type of temporary plugging particle, the oven temperature in step (2) was set to 60°C and 90°C, and the standard solubility of each temporary plugging agent at 60°C and 90°C was obtained. The specific results are shown in Table 2.

[0237] B. Determination of water-deficient solubility of temporary plugging particles at different temperatures

[0238] ① Set the temperature of the constant temperature drying oven to 105℃, dry the experimental filter paper to constant weight, and record it as m1' (accurate to 0.0001g);

[0239] ② Weigh 20g (accurate to 0.0001g) of temporary plugging particles using an electronic balance, and record it as m2'. Add the weighed temporary plugging particles to a wide-mouth bottle containing 20mL of distilled water and stir well. Place the wide-mouth bottle containing the temporary plugging particles and distilled water into an oven set to the experimental temperature. After maintaining the temperature for 72h, stop heating.

[0240] ③ Open the wide-mouth bottle, filter the mixture in the wide-mouth bottle with rapid qualitative filter paper, rinse the filter residue with 100mL of distilled water, and then place the filter paper and filter residue in an oven at 105℃ to dry to constant weight, and record it as m3'.

[0241] ④According to Calculate the water-deficient solubility rate of the temporary plugging particles; the experimental temperatures in step ② are 60℃ and 90℃.

[0242] Following steps ①, ②, ③, and ④, the water-deficient solubility of the temporary plugging particles prepared in Examples 1 to 10 and Comparative Examples 1 to 8 was determined. During the water-deficient solubility determination of each type of temporary plugging particle, the oven temperature in step ② was set to 60℃ and 90℃. The water-deficient solubility of each temporary plugging agent at 60℃ and 90℃ was obtained. Specific results are shown in Table 2, where " / " indicates that the determination could not be performed or that no temporary plugging particles were prepared for determination.

[0243] Table 2. Standard solubility and water-deficient solubility of temporarily plugging particles at different temperatures

[0244]

[0245] The data in Table 2 show that the standard solubility and water-deficient solubility of the temporary plugging particles made of the second composite material prepared in Examples 1 to 10 at 60°C were 80.3% to 96.5% and 71.5% to 90.7%, respectively; and at 90°C, the standard solubility and water-deficient solubility were 96.4% to 99.6% and 91.3% to 99.2%, respectively. This indicates that the temporary plugging agents prepared in Examples 1 to 10 have excellent solubility at 60 to 90°C and maintain a high solubility even under water-deficient conditions. The copolymer molar ratio of lactide and lactide in the first lactide-lactide copolymer used in the temporary plugging particles prepared in Comparative Example 1 is different from that used in Examples 1 to 10. As a result, the standard solubility and water-deficient solubility of the temporary plugging particles prepared in Comparative Example 1 at 60°C were 65.8% and 52.2%, respectively; and at 90°C, the standard solubility and water-deficient solubility were 89.3% and 81.7%, respectively, indicating that the solubility performance was inferior to that of the temporary plugging particles made of the second composite material prepared in Examples 1 to 10. Comparative Example 3 prepared temporary plugging particles containing a first composite material prepared using a commercially available nucleating agent and a first ethylene-lactide copolymer, without the addition of ammonium polyphosphate. Both its standard solubility and water-deficient solubility were lower than those of the temporary plugging particles made of the second composite material prepared in Examples 1 to 10, indicating that ammonium polyphosphate is beneficial in enhancing the solubility of the second composite material temporary plugging particles. Comparative Example 6 directly prepared temporary plugging particles by simple physical mixing of the first and second ethylene-lactide copolymers. At the same temperature, its standard solubility and water-deficient solubility were lower than those of the temporary plugging particles prepared in Examples 1 to 10. Comparative Example 7... Although the temporary plugging particles prepared by simple physical mixing of soluble acrylic resin irregular particles and copolymer-grade polyacrylamide irregular particles have a high standard solubility at 90℃, their standard solubility at 60℃ is only 20.4%, and they only swell but do not dissolve under water-deficient conditions, with water-deficient solubility at both 60℃ and 90℃ being 0, which cannot meet the complex formation conditions in practical applications. The temporary plugging particles in Comparative Example 8 are polylactic acid irregular particles, which do not dissolve at 60℃, and their standard solubility and water-deficient solubility at 90℃ are only 37.5% and 26.8%, respectively, indicating significantly poor solubility.

[0246] Based on the plugging strength data shown in Table 1 and the solubility data shown in Table 2, it can be seen that the temporary plugging particles made of the second composite material prepared in Examples 1 to 10 not only have good plugging pressure-bearing capacity, but also high solubility and excellent solubility even under water-deficient conditions. They can effectively plug fractures with a width of 1 mm to 2 mm, have strong adaptability to fractures, low requirements for downhole water quality, and do not pollute the environment, thus meeting the requirements of current temporary plugging and diversion fracturing technology for plugging agents. Although the temporary plugging particles prepared in Comparative Examples 1 and 3 have high plugging strength for 1 mm and 2 mm fractures, their solubility is poor, and their requirements for downhole water quality are high in practical applications. Although the temporary plugging particles prepared in Comparative Examples 4 and 6 have good solubility, their plugging pressure-bearing capacity is poor, and they cannot effectively plug fractures. The plugging agents in Comparative Examples 7 and 8 have poor plugging pressure-bearing capacity and solubility, and cannot meet the requirements of temporary plugging and diversion fracturing technology for plugging agents. The processes in Comparative Examples 2 and 5 cannot produce the second composite material and temporary plugging particles. This study explains that the copolymerization molar ratio of glycolide and lactide in the first glycolide-lactide copolymer, the ammonium polyphosphate and its degree of polymerization, and the methods and steps for preparing the first and second composite materials all affect the performance of the final temporary plugging particles and whether temporary plugging particles made of the second composite material can be prepared.

[0247] While the present invention has been described with reference to specific embodiments, those skilled in the art will understand that various changes can be made without departing from the true spirit and scope of the invention. Furthermore, numerous modifications can be made to the subject, spirit, and scope of the invention to suit specific situations, materials, material compositions, and methods. All such modifications are included within the scope of the claims of the present invention.

Claims

1. A cylindrical composite material, characterized in that, The cylindrical composite material has a core-skin structure; The core layer is made of a first composite material comprising a first ethylene lactide copolymer and ammonium polyphosphate. The material of the skin layer is a second-phase copolymer of ethylene lactide; The mass ratio of the first ethylene glycol copolymer to ammonium polyphosphate is (2 to 4):1; The first glycolide-lactide copolymer was obtained by copolymerizing glycolide and lactide in a molar ratio of 85:15; The weight-average molecular weight of the first ethylene-lactide copolymer is greater than 50,000; The degree of polymerization of the ammonium polyphosphate is 1000 to 1200; The second glycolide-lactide copolymer was obtained by copolymerizing glycolide and lactide in a molar ratio of (30 to 70):(70 to 30); The weight-average molecular weight of the second ethylene glycol copolymer is 30,000 to 50,000. The core layer is a cylinder with a diameter of 1 mm to 2 mm; The thickness of the skin layer is 0.5 mm to 1 mm.

2. The cylindrical composite material according to claim 1, characterized in that, The weight-average molecular weight of the first ethylene lactide copolymer is 50,000 to 100,000.

3. The cylindrical composite material according to claim 1, characterized in that, The method for preparing the first composite material includes the following steps: 1) The first ethylene-lactide copolymer and ammonium polyphosphate are mixed and granulated to obtain an intermediate material; 2) The intermediate material is extruded into strips, cooled, and then wound up to obtain the first composite material.

4. The cylindrical composite material according to claim 3, characterized in that, In step 1), the granulation is performed using a twin-screw granulator.

5. The cylindrical composite material according to claim 3, characterized in that, The granulation conditions are melt extrusion granulation at 170°C to 190°C.

6. The cylindrical composite material according to claim 3, characterized in that, In step 2), the extrusion strip is produced using a 3D printing filament machine.

7. The cylindrical composite material according to claim 3, characterized in that, The intermediate material is extruded into strands at a temperature of 175°C to 190°C.

8. The cylindrical composite material according to claim 1, characterized in that, The second glycolide-lactide copolymer is obtained by copolymerizing glycolide and lactide in a molar ratio of 50:

50.

9. A method for preparing a cylindrical composite material as described in any one of claims 1 to 8, comprising the following steps: The second ethylene lactide copolymer is coated on the surface of the core layer, drawn, and cooled to obtain the cylindrical composite material.

10. The method according to claim 9, characterized in that, The coating and traction are achieved by an electric wire extruder.

11. The method according to claim 10, characterized in that, The temperature of the feed hopper of the wire extruder is 110°C to 130°C; and / or The cooling temperature is to cool to room temperature.

12. The method according to claim 9, characterized in that, The cylindrical composite material is granulated along a direction perpendicular to the cylinder axis to obtain temporary plugging particles.

13. The method according to claim 12, characterized in that, The temporary plugging particles are cylindrical with a diameter of 2 mm to 4 mm; and / or a height of 3 mm to 5 mm.

14. The method according to claim 13, characterized in that, The diameter of the temporarily plugging particles is 2.5 mm to 4 mm.

15. The application of the cylindrical composite material according to any one of claims 1 to 8 or the cylindrical composite material prepared by the method according to any one of claims 9 to 14 in the field of natural gas production enhancement technology.

16. The application according to claim 15, characterized in that, The application is the use of the cylindrical composite material in temporary plugging and diverting fracturing.

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