Self-degradation temporary plugging composition as well as preparation method and application thereof

Abstract

The invention provides a self-degradation temporary plugging composition as well as a preparation method and application thereof. The self-degradation temporary plugging composition comprises a modified PGA material, bentonite, a surfactant, a clay stabilizer, a hydration stabilizer, a filtrate reducer, a viscosity reducer, a weighting agent and water.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil development, and particularly relates to a self-degradation temporary plugging composition and a preparation method and application thereof. BACKGROUND

[0002] CN201010100584.1 provides a hydrophobic temporary plugging drilling fluid, which comprises mixed heavy calcium, nano calcium carbonate-starch compound, nano emulsion, ethylene glycol and other treatment agents. The mud cake formed by the hydrophobic temporary plugging drilling fluid has compactness and contains a hydrophobic channel, the channel can control the inflow of filtrate, reservoir protection is realized by the difference in water phase and oil phase permeability of the mud cake, a flow channel is provided for oil and gas, and the defect of strong secondary pollution of conventional temporary plugging drilling fluid is overcome. However, the mud cake formed by the hydrophobic temporary plugging drilling fluid has compactness, and after construction in a medium-high permeability reservoir, the reservoir property is affected to a certain extent.

[0003] CN200510041788.1 provides an oil-soluble temporary plugging drilling fluid for protecting low-permeability sandstone gas layer, which comprises an oil-soluble temporary plugging agent with a weight ratio of 2%-5%, a surfactant with a weight ratio of 0.3%-1%, an inhibitor with a weight ratio of 0.2%-1%, a filtrate reducer with a weight ratio of 0.5%-1.0%, and the rest is water and other additives. The oil-soluble temporary plugging drilling fluid can be applied to low-permeability sandstone gas layer, has the characteristics of good temporary plugging effect, strong inhibition, low density, easy control, low filtration loss, good lubricity and simple process. However, after temporary plugging, the oil-soluble temporary plugging drilling fluid needs to be removed by perforation operation to restore the reservoir permeability.

[0004] The article “Application of low-clay hydrophobic temporary plugging drilling fluid system in Well Pai673-P1” (Zheng Chengsheng et al., Journal of Shengli College of China University of Petroleum) mentions a hydrophobic temporary plugging drilling fluid. The hydrophobic temporary plugging drilling fluid comprises 3% bentonite, 0.2% sodium carbonate, 0.2% caustic soda, 1% solid-free tackifier, 0.3% low-viscosity anionic cellulose, 0.05% bactericide, 0.2% potassium polyacrylate, 0.5% anhydrous polyhydric alcohol, 3% liquid lubricant and a certain amount of hydrophobic plugging particles and hydrophobic deformable polymer. In combination with the hydrophobic deformable polymer, the two hydrophobic materials jointly improve the wettability of the mud cake, so that the mud cake formed by the drilling fluid has a hydrophobic and oleophilic channel, the mud cake prevents the water phase from entering the formation during drilling, and after the completion mud cake is separated from the drilling fluid, self-deblocking can be realized under the action of the organic fluid in the formation. The drilling fluid system provided in the article needs to realize deblocking of the temporary plugging agent under negative pressure after temporary plugging, which puts certain demands on the formation conditions, and the application is limited.

[0005] The article 'Ultra-low permeability composite shielding temporary plugging drilling fluid technology' (Yuan Hongshui, Petroleum Chemical Industry Application) relates to a composite shielding temporary plugging drilling fluid. The composite shielding temporary plugging drilling fluid comprises 3%-5% KCl, 0.3%-0.5% NaOH, 0.3% Na2CO3, 1%-3% ZJ-01+0-3% ZJ-VIS-02, and limestone is used for weighting. The drilling fluid system combines ultra-low permeability drilling fluid technology and broad-spectrum shielding temporary plugging technology. By optimizing and matching the reservoir protection additive according to the reservoir pore throat characteristics, the matching temporary plugging is realized by optimizing the solid phase particles. However, the drilling fluid system provided in the article needs to be perforated to unplug the temporary plugging layer after temporary plugging.

[0006] As can be seen from the above, the existing temporary plugging drilling fluid system is difficult to unplug after temporary plugging, and needs to be perforated, acidized or subjected to special conditions such as negative pressure to realize unplug, and some even cause damage to the reservoir, so it is urgent to develop a temporary plugging drilling fluid system which does not need to be perforated, acidized or subjected to special conditions such as negative pressure and does not cause damage to the reservoir. SUMMARY

[0007] In view of the above problems existing in the prior art, the purpose of the present application is to provide a self-degradable temporary plugging composition, a preparation method and application thereof. The self-degradable temporary plugging composition forms an inner mud cake during drilling, can prevent the drilling fluid from causing damage to the reservoir, and can self-degrade after drilling to restore the permeability of the reservoir without the need for measures such as perforation or acidification or special conditions such as negative pressure to remove the plugging.

[0008] To achieve the above purpose, the first aspect of the present application provides a self-degradable temporary plugging composition, comprising a modified PGA material, bentonite, a surfactant, a clay stabilizer, a hydration stabilizer, a fluid loss additive, a viscosity reducer, a weighting agent and water.

[0009] According to the present application, the total mass of the composition is 100%, and the composition comprises 2-5wt% of the modified PGA material, 2-4wt% of the bentonite, 0.3-0.8wt% of the surfactant, 0.2-0.8wt% of the clay stabilizer, 0.1-2wt% of the hydration stabilizer, 0.5-1wt% of the fluid loss additive, 0.3-0.5wt% of the viscosity reducer, 3-4wt% of the weighting agent and the balance of water.

[0010] According to the present application, the modified PGA material is obtained by melt blending of polyglycolic acid and polylactic acid.

[0011] According to the present application, in the modified PGA material, the mass ratio of the polyglycolic acid to the polylactic acid is (3-7):(3-7).

[0012] According to the present invention, the modified PGA material further includes a compatibilizer;

[0013] Preferably, the total mass of the polyglycolic acid and the polylactic acid is 100%, and the amount of the compatibilizer is 1-3 wt%; and / or

[0014] The compatibilizer is maleic anhydride-grafted polyethylene.

[0015] According to the present invention, the surfactant is a sulfonate surfactant; and / or

[0016] The clay stabilizer is selected from inorganic salt clay stabilizers and / or small cationic clay stabilizers; and / or

[0017] The hydration stabilizer is sodium carbonate and / or potassium carbonate; and / or

[0018] The viscosity reducer is lignin sulfonate.

[0019] A second aspect of the present invention provides a method for preparing a composition as described in the first aspect of the present invention, comprising the following steps:

[0020] 1) Mix the hydration stabilizer, bentonite and water, and hydrate the bentonite to obtain hydrated bentonite slurry;

[0021] 2) Adjust the pH of the hydrated bentonite slurry, and then mix it with the surfactant, filtration reducer, clay stabilizer, viscosity reducer, weighting agent and modified PGA material to obtain the composition.

[0022] According to the present invention, in step 2), the pH is 8-9.

[0023] According to the present invention, the modified PGA material is prepared by means of the following method:

[0024] (1) The polyglycolic acid and polylactic acid are dried to obtain a dried mixture;

[0025] (2) The dried mixture is melt-blended to obtain a melt blend;

[0026] (3) The molten blend is shaped and cooled to solidify, thereby obtaining the modified PGA material.

[0027] According to the present invention, in step (1), after the polyglycolic acid and the polylactic acid are mixed, the compatibilizer is added, and then the drying process is performed.

[0028] According to the present invention, in step (1), the moisture content of the dried mixture is less than 0.1 wt%.

[0029] According to the present invention, in step (2), the conditions for melt blending include a temperature of 200-220°C and / or a duration of 15-30 min.

[0030] According to the present invention, in step (3), the forming process temperature is 200-220°C; and / or

[0031] The cooling and curing temperature is 25-50℃.

[0032] The composition according to the first aspect of the present invention or the composition prepared by the method according to the second aspect of the present invention may be used as a drilling fluid.

[0033] The beneficial effects of this invention are:

[0034] To address the difficulty of unblocking existing temporary plugging drilling fluid systems after temporary plugging, which often requires methods such as perforation, acidizing, or special conditions like negative pressure, and can even damage the reservoir in some cases, this invention provides a self-degradable temporary plugging composition, its preparation method, and its application. The self-degradable temporary plugging composition comprises modified PGA material, bentonite, surfactant, clay stabilizer, hydration stabilizer, filtration loss reducer, viscosity reducer, weighting agent, and water. The preparation method of the self-degradable temporary plugging composition is simple, and it can be used as a drilling fluid for self-degradable temporary plugging.

[0035] Compared with the prior art, the present invention has at least the following advantages:

[0036] 1. The modified PGA material in the self-degradable temporary plugging composition exhibits excellent barrier properties, strength, and temperature resistance, with a water vapor permeability of 0.2 g·mm / m. 2 At the same time, the tensile strength reached 115-124MPa and the glass transition temperature reached 170-220℃, which is beneficial to improving the sealing performance of the self-degradable temporary plugging composition when used as a self-degradable temporary plugging liquid.

[0037] 2. The FA sand bed filtration test results of the self-degradable temporary plugging composition as a self-degradable temporary plugging drilling fluid showed that the filtration loss after plugging was 0, and the invasion volume was less than 20%, only 14-17%, which proves that the self-degradable temporary plugging composition provided by the present invention has good plugging performance when used as a drilling fluid.

[0038] 3. The modified PGA material in the self-degradable temporary plugging composition can be completely degraded within 45-90 days of immersion in water. By adjusting the mass ratio of polyglycolic acid and polylactic acid in the modified PGA material, its self-degradation time can be controlled as needed. This allows the self-degradable temporary plugging composition to have a temporary plugging function when used as a drilling fluid. After plugging, there is no need to use perforation, acidizing, negative pressure, or other special conditions to unblock it. The modified PGA material can degrade into harmless water and carbon dioxide after plugging, avoiding potential damage to the reservoir.

[0039] In summary, the self-degradable temporary plugging composition provided by this invention, when used as a drilling fluid, overcomes the shortcomings of existing temporary plugging drilling fluid systems, which are difficult to unplug, require perforation, acidizing, or special conditions such as negative pressure to achieve unplugging, and are prone to reservoir damage. It is suitable for widespread use in drilling scenarios where temporary plugging technology is required. Attached Figure Description

[0040] Figure 1 The experimental structure comparison of the self-degradable temporary plugging drilling fluid prepared in Example 1 and the comparative drilling fluid provided in Comparative Example 1 is shown in the FA sand bed filtration analyzer. In this paper, A corresponds to the test results of the self-degradable temporary plugging drilling fluid prepared in Example 1, and B corresponds to the test results of the comparative drilling fluid provided in Comparative Example 1. Detailed Implementation

[0041] 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.

[0042] One aspect of the present invention provides a self-degradable temporary plugging composition comprising a modified PGA material, bentonite, a surfactant, a clay stabilizer, a hydration stabilizer, a filtration loss reducer, a viscosity reducer, a weighting agent, and water.

[0043] In some embodiments of the present invention, the total mass of the composition is 100%, and the composition comprises 2-5 wt% of the modified PGA material, 2-4 wt% of the bentonite, 0.3-0.8 wt% of the surfactant, 0.2-0.8 wt% of the clay stabilizer, 0.1-2 wt% of the hydration stabilizer, 0.5-1 wt% of the filtration loss reducer, 0.3-0.5 wt% of the viscosity reducer, 3-4 wt% of the weighting agent, and the balance being water.

[0044] In some embodiments of the present invention, the total mass of the composition is 100%, and the composition comprises 2-5 wt% of the modified PGA material, 2-4 wt% of the bentonite, 0.3-0.8 wt% of the surfactant, 0.2-0.8 wt% of the clay stabilizer, 0.5-1.5 wt% of the hydration stabilizer, 0.5-1 wt% of the filtration loss reducer, 0.3-0.5 wt% of the viscosity reducer, 3-4 wt% of the weighting agent, and the balance being water.

[0045] In a preferred embodiment of the present invention, the total mass of the composition is 100%, and the composition comprises 2 wt% of the modified PGA material, 2 wt% of the bentonite, 0.3 wt% of the surfactant, 0.2 wt% of the clay stabilizer, 0.5 wt% of the hydration stabilizer, 0.5 wt% of the filtration loss reducer, 0.3 wt% of the viscosity reducer, 4 wt% of the weighting agent, and the balance being water.

[0046] In a preferred embodiment of the present invention, the total mass of the composition is 100%, and the composition comprises 4 wt% of the modified PGA material, 3 wt% of the bentonite, 0.5 wt% of the surfactant, 0.5 wt% of the clay stabilizer, 1 wt% of the hydration stabilizer, 0.8 wt% of the filtration loss reducer, 0.4 wt% of the viscosity reducer, 3 wt% of the weighting agent, and the balance being water.

[0047] In a preferred embodiment of the present invention, the total mass of the composition is 100%, and the composition comprises 5 wt% of the modified PGA material, 4 wt% of the bentonite, 0.8 wt% of the surfactant, 0.8 wt% of the clay stabilizer, 1.5 wt% of the hydration stabilizer, 1 wt% of the filtration loss reducer, 0.5 wt% of the viscosity reducer, 3 wt% of the weighting agent, and the balance being water.

[0048] In some embodiments of the present invention, the modified PGA material is obtained by compatibilization modification of polyglycolic acid and polylactic acid through melt blending.

[0049] In the modified PGA material, the mass ratio between polyglycolic acid and polylactic acid affects its self-degradation performance. Therefore, it is necessary to limit the mass ratio between polyglycolic acid and polylactic acid in the modified PGA material to control the self-degradation performance of the modified PGA material within a range suitable for drilling fluid applications.

[0050] In some embodiments of the present invention, the mass ratio of polyglycolic acid to polylactic acid in the modified PGA material is (3-7):(3-7).

[0051] In some embodiments of the present invention, the mass ratio of polyglycolic acid to polylactic acid in the modified PGA material is 7:3, 5:5 or 3:7.

[0052] In some embodiments of the present invention, the molecular weight of the polyglycolic acid is 10,000-50,000 Da; and / or the molecular weight of the polylactic acid is 50,000-200,000 Da.

[0053] In addition to controlling the mass ratio of polyglycolic acid and polylactic acid in the modified PGA material, it is also preferable to add a compatibilizer to the modified PGA material to improve the compatibility and mechanical properties of polyglycolic acid and polylactic acid, thereby improving the sealing strength and barrier performance of the modified PGA material.

[0054] In some embodiments of the present invention, the modified PGA material further includes a compatibilizer.

[0055] In some embodiments of the present invention, the total mass of the polyglycolic acid and the polylactic acid is 100%, and the amount of the compatibilizer is 1-3 wt% (e.g., 1 wt%, 2 wt%, or 3 wt%); and / or

[0056] The compatibilizer is maleic anhydride-grafted polyethylene.

[0057] In some embodiments of the present invention, the modified PGA material is a particulate modified PGA material with a particle size of 5-50 mesh (e.g., 5 mesh, 10 mesh, 20 mesh, 30 mesh, 40 mesh or 50 mesh).

[0058] In some embodiments of the present invention, the modified PGA material is a fiber-type modified PGA material with an average diameter of 1 mm and an average length of 6 mm.

[0059] In some embodiments of the present invention, the modified PGA material is a powder-type modified PGA material with a particle size greater than 50 mesh.

[0060] In some embodiments of the present invention, in order to achieve the desired temporary plugging effect, the morphological ratio of the modified PGA material in the composition is adjusted according to the permeability of the target reservoir;

[0061] Preferably, when the target reservoir permeability is >50 mD, the total mass of the modified PGA material in the composition is 100%, wherein the mass percentage of the powdered modified PGA material is 1 wt%.

[0062] When the target reservoir permeability is 10-50 mD, the total mass of the modified PGA material in the composition is 100%, wherein the mass percentage of the powdered modified PGA material is 0.5 wt%.

[0063] When the target reservoir permeability is 1-10 mD, the total mass of the modified PGA material in the composition is 100%, wherein the mass percentage of the powdered modified PGA material is 0.1 wt%.

[0064] More preferably, for crack-type leakage, the mesh size and amount of the granular modified PGA material and the amount of the fibrous modified PGA material in the composition are determined according to the crack development.

[0065] In some embodiments of the present invention, the surfactant is a sulfonate surfactant; and / or

[0066] The clay stabilizer is selected from inorganic salt clay stabilizers and / or small cationic clay stabilizers; and / or

[0067] The hydration stabilizer is sodium carbonate and / or potassium carbonate; and / or

[0068] The viscosity reducer is lignin sulfonate.

[0069] In some embodiments of the present invention, the sulfonate surfactant is an α-olefin sulfonate surfactant, such as sodium α-olefin sulfonate;

[0070] Preferably, in the structure of the sodium α-olefin sulfonate, the number of carbon atoms in the α-olefin is 6-20, such as C6 sodium α-olefin sulfonate, C10 sodium α-olefin sulfonate, or C20 sodium α-olefin sulfonate.

[0071] In some embodiments of the present invention, the inorganic salt clay stabilizer is potassium chloride; and / or

[0072] The small cationic clay stabilizer is at least one of tetraethylammonium chloride, tetrabutylammonium chloride, benzalkonium chloride, and hexamethylammonium chloride.

[0073] In some embodiments of the present invention, the lignin sulfonate is at least one of sodium lignin sulfonate, potassium lignin sulfonate, and calcium lignin sulfonate.

[0074] In some embodiments of the present invention, the filtration reducer is a drilling fluid filtration reducer, such as modified starch and / or low-viscosity carboxymethyl cellulose.

[0075] In some embodiments of the present invention, the weighting agent is barite, hematite or galena, preferably barite.

[0076] The second aspect of the present invention provides a method for preparing a composition as described in the first aspect of the present invention, comprising the following steps:

[0077] 1) Mix the hydration stabilizer, bentonite and water, and hydrate the bentonite to obtain hydrated bentonite slurry;

[0078] 2) Adjust the pH of the hydrated bentonite slurry, and then mix it with the surfactant, filtration reducer, clay stabilizer, viscosity reducer, weighting agent and modified PGA material to obtain the composition.

[0079] In some embodiments of the present invention, in step 1), the hydration stabilizer, the bentonite and water are mixed, stirred at a drilling speed of 1000-1500 r / min, and left to stand for 18-30 h to complete the hydration treatment.

[0080] In some embodiments of the present invention, in step 2), the pH is 8-9, for example 8, 8.5 or 9.

[0081] In some embodiments of the present invention, in step 2), after adjusting the pH of the hydrated bentonite slurry, it is first mixed with a surfactant, a filtration reducer, a clay stabilizer, a viscosity reducer, and a weighting agent, and stirred at a speed of 1000-2000 r / min for 15-20 min. Then, the modified PGA material is added, and the mixture is stirred at a speed of 1000-2000 r / min for 45-60 min to obtain the composition.

[0082] In some embodiments of the present invention, the modified PGA material is prepared by means of:

[0083] (1) The polyglycolic acid and polylactic acid are mixed and then dried to obtain a dried mixture;

[0084] (2) The dried mixture is melt-blended to obtain a melt blend;

[0085] (3) The molten blend is shaped and cooled to solidify, thereby obtaining the modified PGA material.

[0086] In some embodiments of the present invention, in step (1), the polyglycolic acid and the polylactic acid are mixed, the compatibilizer is added, and then the drying process is performed.

[0087] In step (1), the purpose of the drying process is to remove water and other volatile impurities contained in the polyglycolic acid, polylactic acid, and compatibilizer (if added), so as to prevent the polyglycolic acid and / or polylactic acid from generating bubbles or decomposing during the subsequent melt blending process.

[0088] In some embodiments of the present invention, in step (1), the moisture content of the dried mixture is less than 0.1 wt%; and / or

[0089] The drying process is carried out at a temperature of 80-100℃ and / or for a duration of 6-8 hours.

[0090] It should be noted that the drying temperature and duration can be adjusted according to the moisture content of the polyglycolic acid, polylactic acid, and compatibilizer (if added) used, and the moisture content of the dried mixture should be reduced to below 0.1 wt%.

[0091] In some embodiments of the present invention, in step (2), the melt blending conditions include a temperature of 200-220°C; and / or a rotation speed of 60-100 rpm; and / or a duration of 15-30 min. During the preparation of the modified PGA material, the melt blending conditions should be strictly controlled according to the above-defined temperature and duration to avoid thermal degradation of polyglycolic acid and / or polylactic acid due to excessively high temperature or excessively long duration.

[0092] In some embodiments of the invention, the melt blending is preferably carried out in a twin-screw extruder.

[0093] In some embodiments of the present invention, in step (3), the temperature of the molding process is 200-220°C;

[0094] and / or

[0095] The cooling and curing temperature is 25-50℃.

[0096] In some embodiments of the present invention, the molding process is performed by extrusion molding using a twin-screw extruder; or

[0097] The forming process is carried out by calendering using a calendering machine.

[0098] In some embodiments of the present invention, when performing the molding process, the extrusion temperature of the twin-screw extruder is set to 200-220°C; and / or the extrusion speed is set to 10-30 kg / h.

[0099] In some embodiments of the present invention, when performing the forming process, the calendering temperature of the calender is set to 200-220°C; and / or the calendering speed is set to 30-60 kg / h.

[0100] It should be noted that, depending on actual needs, modified PGA materials of the required shape and size can be obtained by means including but not limited to cutting, grinding, etc., such as granular modified PGA materials with a particle size of 5-50 mesh, fiber-type modified PGA materials with an average diameter of 1 mm and an average length of 6 mm, and powder-type modified PGA materials with a particle size greater than 50 mesh.

[0101] The composition according to one of the present inventions or the composition prepared by the method according to another of the present inventions may be used as a drilling fluid.

[0102] The technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0103] Information on some of the raw materials used in Examples 1 to 3 is as follows:

[0104] PGA: Polyglycolic acid, purchased from Wuhan Haishan Technology Co., Ltd., with a molecular weight of 20,000 Da;

[0105] PLA: Polylactic acid, purchased from Wuhan Haishan Technology Co., Ltd., with a molecular weight of 50,000 Da;

[0106] Low-viscosity carboxymethyl cellulose: viscosity <40 mPa.s, purchased from Weifang Lude Chemical Co., Ltd.

[0107] Information on some of the raw materials used in Comparative Examples 1 to 3 is as follows:

[0108] Slurry: Water-based drilling fluid;

[0109] Emulsified asphalt and liquid paraffin: sourced from Western Drilling's Drilling Fluid Branch;

[0110] PLA: Polylactic acid, purchased from Shanghai Lanmeng Environmental Protection Technology Co., Ltd., with a molecular weight of 50,000 Da;

[0111] PVA: Polyvinyl alcohol, purchased from Anhui Wanwei High-Tech Materials Co., Ltd.

[0112] Example 1

[0113] Preparation of modified PGA materials:

[0114] (1) PGA (polyglycolic acid) and PLA (polylactic acid) are mixed in a mass ratio of 7:3 and placed in a vacuum drying oven at 100°C for 8 hours to remove moisture and other impurities, so that the moisture content of PGA and PLA is below 0.1% to obtain a dried mixture.

[0115] (2) Place the dried mixture into a twin-screw extruder and melt mix at 220°C and 100 rpm for 30 minutes to ensure uniform mixing and obtain a melt blend.

[0116] (3) The molten mixture is extruded through a twin-screw extruder at 220°C and 30kg / h for molding, then cooled and solidified at 50°C, and after cutting and screening, granular modified PGA material with an average particle size of 20 mesh is obtained.

[0117] Preparation of self-degradable temporary plugging composition:

[0118] 1) Mix 90.2g water, 2g bentonite and 0.5g sodium carbonate, stir evenly at 1500r / min, seal and let stand for 30h to carry out the hydration treatment of bentonite and obtain hydrated bentonite slurry.

[0119] 2) Add sodium hydroxide to the hydrated bentonite slurry obtained in step 1) to adjust the pH to 9, and then add 0.3g of C10 α-olefin sodium sulfonate, 0.2g of potassium chloride, 0.5g of low-viscosity carboxymethyl cellulose, 4g of barite, and 0.3g of sodium lignosulfonate. Stir at a drilling speed of 2000r / min for 20min. Then add 2g of the granular modified PGA material with an average particle size of 20 mesh prepared in this example, and stir at a speed of 2000r / min for 60min to obtain a self-degradable temporary plugging composition, a self-degradable temporary plugging drilling fluid.

[0120] Example 2

[0121] Preparation of modified PGA materials:

[0122] (1) PGA (polyglycolic acid) and PLA (polylactic acid) are mixed in a mass ratio of 5:5 and placed in a vacuum drying oven at 90°C for 7 hours to remove moisture and other impurities, so that the moisture content of PGA and PLA is below 0.1% to obtain a dried mixture.

[0123] (2) Place the dried mixture into a twin-screw extruder and melt mix at 210°C and 80 rpm for 30 minutes to ensure uniform mixing and obtain a melt blend.

[0124] (3) The molten mixture is extruded through a twin-screw extruder at 210°C and 20kg / h for molding and then cooled and solidified at 35°C. After cutting, the granular modified PGA material with an average particle size of 20 mesh is obtained by screening.

[0125] Preparation of self-degradable temporary plugging composition:

[0126] 1) Mix 86.8g water, 3g bentonite and 1g sodium carbonate, stir evenly at 1200r / min, seal and let stand for 24h to carry out the hydration treatment of bentonite and obtain hydrated bentonite slurry.

[0127] 2) Add sodium hydroxide to the hydrated bentonite slurry obtained in step 1) to adjust the pH to 8.5, then add 0.5g of C10 α-olefin sodium sulfonate, 0.5g of potassium chloride, 0.8g of low-viscosity carboxymethyl cellulose, 3g of barite, and 0.4g of lignin sodium sulfonate. Stir at a drilling speed of 1500r / min for 17min. Then add 4g of the granular modified PGA material with an average particle size of 20 mesh prepared in this example, and stir at a speed of 1500r / min for 50min to obtain a self-degradable temporary plugging composition, a self-degradable temporary plugging drilling fluid.

[0128] Example 3

[0129] Preparation of modified PGA materials:

[0130] (1) PGA (polyglycolic acid) and PLA (polylactic acid) were mixed in a mass ratio of 3:7. Maleic anhydride-grafted polyethylene was added as a compatibilizer at 1 wt% of the total mass of PGA and PLA. The mixture was placed in a vacuum drying oven and vacuum dried at 80°C for 6 hours to remove moisture and other impurities, so that the moisture content of PGA, PLA and maleic anhydride-grafted polyethylene was all below 0.1%, and a dried mixture was obtained.

[0131] (2) Place the dried mixture into a twin-screw extruder and melt mix at 200°C and 60 rpm for 30 minutes to ensure uniform mixing and obtain a melt blend.

[0132] (3) The molten mixture is shaped by a calender at 200°C and 30kg / h, and then cooled and solidified at 25°C. After cutting, the granular modified PGA material with an average particle size of 20 mesh is obtained by screening.

[0133] Preparation of self-degradable temporary plugging composition:

[0134] 1) Mix 83.4g water, 4g bentonite and 1.5g sodium carbonate, stir evenly at 1000r / min, seal and let stand for 18h to carry out the hydration treatment of bentonite and obtain hydrated bentonite slurry.

[0135] 2) Add sodium hydroxide to the hydrated bentonite slurry obtained in step 1) to adjust the pH to 8, and then add 0.8g of C10 α-olefin sodium sulfonate, 0.8g of potassium chloride, 1g of low-viscosity carboxymethyl cellulose, 3g of barite, and 0.5g of lignin sodium sulfonate. Stir at a drilling speed of 1000r / min for 15min. Then add 5g of the granular modified PGA material with an average particle size of 20 mesh prepared in this example and stir at a speed of 1000r / min for 45min to obtain a self-degradable temporary plugging composition, a self-degradable temporary plugging drilling fluid.

[0136] Comparative Example 1

[0137] This comparative example provides a comparative drilling fluid comprising well slurry and ultrafine calcium carbonate with an average particle size of 23 μm, wherein the mass of the well slurry is 100% and the amount of ultrafine calcium carbonate added is 3 wt%.

[0138] Comparative Example 2

[0139] This comparative example provides a comparative drilling fluid comprising well slurry and emulsified bitumen, wherein the mass of well slurry is 100% and the amount of emulsified bitumen added is 5 wt%.

[0140] Comparative Example 3

[0141] This comparative example provides a comparative drilling fluid comprising well slurry and liquid paraffin, wherein the mass of well slurry is 100% and the amount of liquid paraffin added is 5 wt%.

[0142] Comparative Example 4

[0143] This comparative example provides a traditional temporary plugging material, specifically PLA (polylactic acid), purchased from Shanghai Lanmeng Environmental Protection Technology Co., Ltd.

[0144] Comparative Example 5

[0145] This comparative example provides a traditional temporary plugging material, specifically PVA (polyvinyl alcohol), purchased from Anhui Wanwei High-Tech Materials Co., Ltd.

[0146] Experimental Evaluation

[0147] 1. Determination of barrier properties, strength, and temperature resistance of modified PGA materials and traditional temporary plugging materials

[0148] 1-1. Barrier properties

[0149] The water vapor transmission rate was determined according to the following steps:

[0150] ① Prepare standard-sized thin film samples from the modified PGA material;

[0151] ② Mount the thin film sample onto the testing instrument, ensuring a good seal;

[0152] ③ Set the test temperature and humidity conditions to 23℃ and 50% relative humidity;

[0153] ④ Begin the test and record the water vapor transmission rate;

[0154] ⑤ Calculate the transmittance using the instrument software; the unit is g·mm / m. 2 ·day (water vapor).

[0155] 1-2. Strength

[0156] Perform tensile strength testing according to the following steps:

[0157] ① Prepare standard test strip samples from modified PGA materials (or PLA or PVA);

[0158] ② Install the standard test strip sample on the testing machine and select appropriate fixtures;

[0159] ③ Set the stretching speed to 5 mm / min;

[0160] ④ Begin the test, record the tensile force and elongation until the sample breaks;

[0161] ⑤ Calculate the tensile strength using the instrument software; the unit is MPa.

[0162] 1-3. Temperature resistance

[0163] Perform the glass transition temperature determination according to the following steps:

[0164] ① Prepare samples of standard size from the modified PGA material (or PLA or PVA);

[0165] ② Place the sample into the DSC analyzer;

[0166] ③ Set the heating rate to 10℃ / min and the maximum test temperature to 250℃;

[0167] ④ Begin testing and record the endothermic and exothermic peaks of the sample;

[0168] ⑤ Analyze the glass transition temperature of the sample.

[0169] The results are shown in Table 1.

[0170] Table 1. Test results of barrier properties, sealing strength and temperature resistance of temporary plugging materials

[0171]

[0172] As shown in Table 1, traditional temporary plugging materials, such as pure PLA and pure PVA, generally exhibit moderate performance in terms of temperature resistance and strength, with glass transition temperatures around 60℃ and 100℃, respectively, and tensile strengths around 70MPa and 60MPa, respectively. Furthermore, the barrier properties of pure PLA and pure PVA are generally 0.1-10 g·mm / m. 2 The water vapor transmission rate per day. The modified PGA material prepared in this invention exhibits excellent barrier properties, strength, and high-temperature resistance, with a water vapor transmission rate of 0.2 g·mm / m. 2 · Simultaneously, the tensile strength reached 115-124 MPa, and the glass transition temperature reached 170-220℃. 2. Self-degradation properties of modified PGA materials.

[0173] The self-degradation time was determined following these steps:

[0174] ① Prepare samples of the modified PGA material to standard size;

[0175] ② Soak it in distilled water (under normal temperature and pressure conditions);

[0176] ③ Record its weight changes at intervals and observe its shape changes at the same time;

[0177] ④ Plot the curve of mass loss rate over time to obtain the self-degradation time.

[0178] The results are shown in Table 2.

[0179] Table 2. Results of self-degradation performance test

[0180]

[0181] As shown in Table 2, the modified PGA material prepared by this invention can degrade into harmless water and carbon dioxide after unblocking, avoiding potential damage to the reservoir. Furthermore, the self-degradation time of the modified PGA material can be controlled by adjusting the mass ratio between PGA and PLA in the modified PGA material.

[0182] 3. The plugging performance of self-degradable temporary plugging drilling fluid and comparative drilling fluid.

[0183] The self-degradable temporary plugging drilling fluids prepared in Examples 1 to 3 and the comparative drilling fluids provided in Examples 1 to 3 were subjected to FA sand bed filtration loss test (using 20-40 mesh quartz sand) under normal temperature and pressure conditions to measure filtration loss and invasion volume, and to evaluate the plugging performance of the self-degradable temporary plugging drilling fluids and comparative drilling fluids.

[0184] The results are shown in Table 3. Figure 1 .

[0185] Table 3. Experimental Results of FA Sand Bed Filtration Tester

[0186]

[0187] from Figure 1 Tables A and B show the FA sand bed filtration loss test results of the self-degrading temporary plugging drilling fluid provided in Example 1 and the FA sand bed filtration loss test results of the comparative drilling fluid provided in Comparative Example 1, respectively. Table 3 shows that the filtration loss of the self-degrading temporary plugging drilling fluid prepared in Examples 1 to 3 was 0, and the invasion volume was 14-17%, indicating good temporary plugging effect. In contrast, the filtration loss of the comparative drilling fluids provided in Comparative Examples 1 to 3 all reached 500 mL, and the invasion volume all reached 100%, indicating temporary plugging failure. In summary... Figure 1As shown in Table 3, the self-degradable temporary plugging drilling fluid provided by the present invention has good plugging performance and can effectively plug high-permeability formations.

[0188] 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 self-degradable temporary plugging composition, characterized in that, It includes modified PGA materials, bentonite, surfactants, clay stabilizers, hydration stabilizers, filtration loss reducers, viscosity reducers, weighting agents, and water.

2. The composition according to claim 1, characterized in that, The total mass of the composition is 100%, and the composition comprises 2-5 wt% of the modified PGA material, 2-4 wt% of the bentonite, 0.3-0.8 wt% of the surfactant, 0.2-0.8 wt% of the clay stabilizer, 0.1-2 wt% of the hydration stabilizer, 0.5-1 wt% of the filtration loss reducer, 0.3-0.5 wt% of the viscosity reducer, 3-4 wt% of the weighting agent, and the balance being water.

3. The composition according to claim 1 or 2, characterized in that, The modified PGA material is obtained by compatibilization modification of polyglycolic acid and polylactic acid through melt blending.

4. The composition according to claim 3, characterized in that, In the modified PGA material, the mass ratio of polyglycolic acid to polylactic acid is (3-7):(3-7).

5. The composition according to claim 3 or 4, characterized in that, The modified PGA material also includes a compatibilizer; Preferably, the total mass of the polyglycolic acid and the polylactic acid is 100%, and the amount of the compatibilizer is 1-3 wt%; and / or The compatibilizer is maleic anhydride-grafted polyethylene.

6. The composition according to any one of claims 1 to 5, characterized in that, The surfactant is a sulfonate surfactant; and / or The clay stabilizer is selected from inorganic salt clay stabilizers and / or small cationic clay stabilizers; and / or The hydration stabilizer is sodium carbonate and / or potassium carbonate; and / or The viscosity reducer is lignin sulfonate.

7. A method for preparing the composition according to any one of claims 1 to 6, characterized in that, Includes the following steps: 1) Mix the hydration stabilizer, bentonite and water, and hydrate the bentonite to obtain hydrated bentonite slurry; 2) Adjust the pH of the hydrated bentonite slurry, and then mix it with the surfactant, filtration reducer, clay stabilizer, viscosity reducer, weighting agent and modified PGA material to obtain the composition.

8. The method according to claim 7, characterized in that, In step 2), the pH is 8-9.

9. The method according to claim 7 or 8, characterized in that, The modified PGA material was prepared in the following manner: (1) The polyglycolic acid and polylactic acid are mixed and then dried to obtain a dried mixture; (2) The dried mixture is melt-blended to obtain a melt blend; (3) The molten blend is shaped and cooled to solidify, thereby obtaining the modified PGA material.

10. The method according to claim 9, characterized in that, In step (1), the polyglycolic acid and the polylactic acid are mixed, the compatibilizer is added, and then the drying process is performed.

11. The method according to claim 9 or 10, characterized in that, In step (1), the moisture content of the dried mixture is less than 0.1 wt%.

12. The method according to any one of claims 9 to 11, characterized in that, In step (2), the conditions for melt blending include a temperature of 200-220°C and / or a duration of 15-30 min.

13. The method according to any one of claims 9 to 12, characterized in that, In step (3), the forming process temperature is 200-220℃; and / or The cooling and curing temperature is 25-50℃.

14. The use of the composition according to any one of claims 1 to 6 or the composition prepared by the method according to any one of claims 7 to 13 as a drilling fluid.

Images