Environment-friendly temporary plugging agent composition for oilfield fracturing as well as preparation method and application of environment-friendly temporary plugging agent composition

Abstract

The invention relates to the field of petroleum engineering and chemical engineering, and discloses an environment-friendly temporary plugging agent composition for oil field fracturing, a preparation method of the environment-friendly temporary plugging agent composition and application of the environment-friendly temporary plugging agent composition in low-temperature oil reservoir fracturing. The composition contains polyglycolic acid A, a main emulsifier B, a co-emulsifier C, a thickening agent D and water, the median particle size D50 of the polyglycolic acid A is 20 to 100 microns; the weight ratio of the polyglycolic acid A to the thickening agent D is (2-10): 1. The polyglycolic acid A and the thickening agent D in a specific weight ratio are good in stability, can enter a low-temperature oil reservoir stratum under the combined action of the emulsifier, can effectively block original gaps, can realize automatic degradation and no recovery within a certain time without plug removal, and can also improve the crude oil recovery rate at the same time.

Description

Technical Field

[0001] The invention belongs to the field of petroleum engineering and chemical industry, and specifically relates to an environmentally friendly temporary plugging agent composition for oil field fracturing, a preparation method thereof, and an application thereof in low-temperature reservoir fracturing. Background Art

[0002] At present, in the process of oil field development, the use of hydraulic fracturing technology has become one of the main technical measures for reservoir transformation. The implementation of hydraulic fracturing technology can create more formation cracks in the oil reservoir, thereby achieving the purpose of increasing the production capacity of a single well. This technology has been widely used worldwide. However, with the extension of the water injection development cycle and the deepening of the heterogeneity of the reservoir formation, the crude oil in the oil leakage area formed by the initial fracturing operation is continuously produced, and the saturation is continuously reduced, resulting in a year-on-year decline in the production of a single well. However, there is still a large amount of residual oil in the unfractured area. In order to effectively solve this problem, the current oil field mainly adopts temporary plugging to repeated fracturing technology. The key to the temporary plugging to repeated fracturing technology is to create more new cracks, and the most important thing to create new cracks is to choose a suitable temporary plugging agent. Therefore, the fracturing temporary plugging agent is the technical key to temporary plugging to repeated fracturing.

[0003] According to the different raw materials of temporary plugging materials, temporary plugging agents for oilfield fracturing can be divided into inert inorganic solid temporary plugging agents and inert organic resin temporary plugging agents; according to the different ways of unblocking temporary plugging materials after fracturing construction, they can be divided into acid-soluble fracturing temporary plugging agents, oil-soluble fracturing temporary plugging agents and water-soluble fracturing temporary plugging agents. It is not difficult to see that all the above types of fracturing temporary plugging agents require subsequent unblocking processes to release the original formation gaps, and the unblocking process is complicated and costly, which can easily cause a series of problems such as reservoir damage and incomplete unblocking, which seriously restricts the application and promotion of fracturing temporary plugging technology. Therefore, it is urgent to develop an environmentally friendly temporary plugging agent product for fracturing that is suitable for low-temperature oil reservoirs and does not require unblocking and can be self-degraded to support the technical development in the field of oilfield fracturing. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem that the existing temporary plugging agent for fracturing needs to be subsequently unblocked in low-temperature oil reservoirs, and to provide an environmentally friendly temporary plugging agent composition for oil field fracturing and a preparation method and application thereof. The composition of the present invention comprises polyglycolic acid A and thickener D in a specific weight ratio, has good stability, enters the low-temperature oil reservoir formation under the joint action of an emulsifier, can effectively block the original gaps, and can be automatically degraded within a certain period of time without unblocking, and does not need to be recycled.

[0005] In order to achieve the above-mentioned object, the first aspect of the present invention provides an environmentally friendly temporary plugging agent composition for oilfield fracturing, characterized in that the composition contains polyglycolic acid A, a primary emulsifier B, a co-emulsifier C, a thickener D and water;

[0006] The median particle size D50 of the polyglycolic acid A is 20 - 100 μm;

[0007] The weight ratio of the polyglycolic acid A to the thickener D is 2 - 10:1.

[0008] The second aspect of the present invention provides a preparation method of an environment-friendly temporary plugging agent composition for oilfield fracturing, which is characterized in that the preparation method comprises the following steps:

[0009] (1) Add the thickener D into water, carry out the first stirring to obtain a mixed solution I;

[0010] (2) Add the main emulsifier B into the above-mentioned mixed solution II, carry out the second stirring to obtain a mixed emulsion II;

[0011] (3) Add the co-emulsifier C into the above-mentioned mixed emulsion II, carry out the third stirring to obtain a mixed emulsion III;

[0012] (4) Add the polyglycolic acid A into the above-mentioned mixed emulsion III, carry out the fourth stirring to obtain the environment-friendly temporary plugging agent composition for fracturing;

[0013] The median particle size D50 of the polyglycolic acid A is 20 - 100 μm;

[0014] The weight ratio of the polyglycolic acid A to the thickener D is 2 - 10:1.

[0015] The third aspect of the present invention provides an environment-friendly temporary plugging agent composition for oilfield fracturing prepared by the above method.

[0016] The fourth aspect of the present invention provides an application of the above environment-friendly temporary plugging agent composition for oilfield fracturing in low-temperature reservoir fracturing operations.

[0017] Through the above technical solutions, the environment-friendly temporary plugging agent composition for oilfield fracturing provided by the present invention, its preparation method and application obtain the following beneficial effects:

[0018] In the present invention, the polyglycolic acid A and the thickener D with a specific weight ratio produce a synergistic effect. The polyglycolic acid A is uniformly and effectively dispersed in the three-dimensional network structure formed by the interweaving of the macromolecules of the thickener D, reducing the free movement space of the particles, increasing the viscosity of the system, and having good system stability.

[0019] Furthermore, the polyglycolic acid A is a high-molecular material with good biodegradability, which produces a synergistic effect with other components in the environment-friendly temporary plugging agent composition, enabling the composition to have good degradation performance under low-temperature reservoir conditions, undergoing complete degradation within 72 hours, with the residue after degradation being less than 5%, and no plugging removal is required. It can enter the reservoir together with the subsequent injected water, having little impact on the environment. Detailed implementation mode

[0020] The endpoints and any values within the ranges disclosed herein are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0021] The first aspect of the present invention provides an environmentally friendly temporary plugging agent composition for oilfield fracturing, which is characterized by containing polyglycolic acid A, main emulsifier B, co-emulsifier C, thickener D and water;

[0022] The median particle size D50 of the polyglycolic acid A is 20 - 100 μm;

[0023] The weight ratio of the polyglycolic acid A to the thickener D is 2 - 10:1.

[0024] In the present invention, the polyglycolic acid A with a specific weight ratio and the thickener D produce a synergistic effect, enabling the polyglycolic acid A to be uniformly and effectively dispersed in the three-dimensional network structure formed by the interweaving of the macromolecules of the thickener D, reducing the space for free movement of the particles, increasing the viscosity of the system, and preventing agglomeration and adhesion between the particles.

[0025] In the present invention, the water is common oilfield water or formation water in the art, and the present invention does not make special limitations thereto.

[0026] In the present invention, a laser particle size analyzer is used to detect the median particle size D50 of the polyglycolic acid A, and the method for preparing the particle size of the polyglycolic acid A is a conventional method in the art, and the polyglycolic acid A can meet the requirements within this particle size range.

[0027] According to the present invention, relative to 100 parts by weight of water, the content of the polyglycolic acid A is 1 - 10 parts by weight, the content of the main emulsifier B is 0.1 - 3 parts by weight, the content of the co-emulsifier C is 0.1 - 1 part by weight, and the content of the thickener D is 0.5 - 2 parts by weight.

[0028] In the present invention, the composition with the above specific content has good stability. In the oil reservoir, when used as a temporary plugging agent, each component of the composition is an environmentally friendly material and can be almost completely degraded under low-temperature oil reservoir conditions, reducing the harm to the oil reservoir formation.

[0029] Furthermore, in the present invention, the low-temperature oil reservoir refers to an oil reservoir with a temperature less than or equal to 60 °C.

[0030] According to the present invention, relative to 100 parts by weight of water, the content of glycolic acid A is 2-8 parts by weight, the content of main emulsifier B is 0.8-2 parts by weight, the content of co-emulsifier C is 0.2-0.7 parts by weight, and the content of thickener D is 0.8-1.5 parts by weight.

[0031] According to the present invention, the weight ratio of polyglycolic acid A to thickener D is 3-9:1.

[0032] According to the present invention, the median particle size D50 of polyglycolic acid A is 20-80 μm.

[0033] Furthermore, the number average molecular weight of polyglycolic acid A is 50,000-150,000, preferably 50,000-100,000.

[0034] According to the present invention, the main emulsifier B is an anionic emulsifier.

[0035] Furthermore, the main emulsifier B is selected from at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate.

[0036] According to the present invention, the co-emulsifier C is a non-ionic emulsifier.

[0037] Furthermore, the co-emulsifier C is selected from at least one of span 20, span 40, span 60, span 80, tween 20, tween 40, tween 60, and tween 80, preferably at least one of span 40, span 60, span 80, tween 40, tween 60, and tween 80.

[0038] According to the present invention, the thickener D is a cellulose derivative.

[0039] Furthermore, the thickener D is selected from at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl cellulose.

[0040] The second aspect of the present invention provides a preparation method of an environmentally friendly temporary plugging agent composition for oilfield fracturing, characterized in that the preparation method includes the following steps:

[0041] (1) Add the thickener D to water and conduct the first stirring to obtain a mixed solution I;

[0042] (2) Add the main emulsifier B to the above-mentioned mixed solution I and conduct the second stirring to obtain a mixed emulsion II;

[0043] (3) Add the co-emulsifier C to the above-mentioned mixed emulsion II and conduct the third stirring to obtain a mixed emulsion III;

[0044] (4) Add polyglycolic acid A to the above-mentioned mixed emulsion III, and perform the fourth stirring to obtain the environmentally friendly temporary plugging agent composition for oilfield fracturing;

[0045] The median particle size D50 of the polyglycolic acid A is 20 - 100 μm;

[0046] The weight ratio of the polyglycolic acid A to the thickener D is 2 - 10:1.

[0047] In the present invention, a specific feeding sequence can give full play to the advantages of each component, make the composition system more stable, the obtained composition can meet the compressive strength requirements in low-temperature reservoirs, and can be completely degraded subsequently without polluting the environment.

[0048] The types and dosages of the raw materials of the oilfield fracturing temporary plugging agent composition prepared in the second aspect of the present invention are exactly the same as those of the raw materials described in the first aspect of the present invention. To avoid repetition, the present invention will not elaborate further in this second aspect, and those skilled in the art should not understand it as a limitation of the present invention.

[0049] According to the present invention, the first stirring time is 60 - 150 min, and the temperature is 20 - 60 °C; more preferably, the first stirring time is 90 - 120 min, and the temperature is 30 - 50 °C.

[0050] According to the present invention, the second stirring time is 10 - 30 min, and the temperature is 20 - 60 °C; more preferably, the second stirring time is 15 - 25 min, and the temperature is 30 - 50 °C.

[0051] According to the present invention, the third stirring time is 10 - 30 min, and the temperature is 20 - 60 °C; more preferably, the third stirring time is 15 - 25 min, and the temperature is 30 - 50 °C.

[0052] According to the present invention, the fourth stirring time is 10 - 30 min, and the temperature is 20 - 60 °C; more preferably, the fourth stirring time is 10 - 20 min, and the temperature is 30 - 50 °C.

[0053] In the present invention, specific stirring time and temperature will improve the orderly connection of the process sections, enhance the suspension stability and the compatibility with the on-site water sample, and meet the on-site construction requirements.

[0054] According to a particularly preferred embodiment of the present invention, the oilfield fracturing temporary plugging agent composition is prepared according to the following steps:

[0055] Step 1, weigh 0.8 - 1.5 parts by weight of the micro-crosslinked polymer D, add it to 100 parts by weight of water, and after fully stirring at 30 - 45 °C for 90 - 120 min, obtain the mixed solution I;

[0056] Step 2: Weigh 0.8 - 1.8 parts by weight of main emulsifier B and add it to the above - mentioned mixed solution I. After fully stirring at 30 - 45 °C for 15 - 25 min, a mixed emulsion II is obtained.

[0057] Step 3: Weigh 0.2 - 0.6 parts by weight of co - emulsifier C and add it to the above - mentioned mixed emulsion II. After fully stirring at 30 - 45 °C for 15 - 25 min, a mixed emulsion III is obtained.

[0058] Step 4: Weigh 2 - 7 parts by weight of polyglycolic acid A and add it to the mixed emulsion III obtained in Step 3. After fully stirring at 30 - 45 °C for 10 - 20 min, an environmentally friendly temporary plugging agent composition for fracturing is obtained.

[0059] The third aspect of the present invention provides an environmentally friendly temporary plugging agent composition for oil - field fracturing prepared by the above - mentioned method.

[0060] The fourth aspect of the present invention provides an application of the above - mentioned environmentally friendly temporary plugging agent composition for oil - field fracturing in low - temperature reservoir fracturing operations.

[0061] The present invention will be described in detail below through examples. The present invention will be described in detail below through examples.

[0062] The performance test of the temporary plugging agent composition adopts the following standards:

[0063] Suspension stability: The temporary plugging agent prepared according to the preparation method of the oil - well fracturing temporary plugging agent composition of the present invention is transferred to a test tube and sealed, and the number of days when obvious stratification appears is observed.

[0064] Surface tension: The surface tension of the polymer solution is measured by using a DCAT - 21 type surface tension meter of Dataphysics Company, Germany, and the measurement temperature is 25 °C.

[0065] The test temperature is 55 °C.

[0066] System viscosity: The apparent viscosity of the polymer solution is measured by using a DV - III type viscometer of Brookfield Company, USA, and the measurement temperature is 55 °C.

[0067] Temporary plugging pressure bearing: Through the fracturing temporary plugging physical model device, the temporary plugging pressure - bearing value can be directly read.

[0068] Residue content: It is calculated by the mass change before and after degradation at 55 °C. The mass before degradation is (M1), and the mass after degradation is (M2). The calculation formula is: (M2 / M1)×100% is the residue content.

[0069] Crude oil recovery rate: Artificial cores (length 30 mm, diameter 2.5 mm) were used. After the cores were evacuated, they were saturated with simulated crude oil, and the amount of saturated oil was m1. Then, water flooding was carried out until the water cut reached 98%. Then, 10 ml of the temporary plugging agent composition was injected. After temporary plugging and fracturing, displacement was continued until the water cut reached 98%. The oil production was m2, and the crude oil recovery rate = (m2 / m1) × 100%.

[0070] Polyglycolic acid A

[0071] A1: The median particle size D50 is 72 μm, and the number average molecular weight is 50,000;

[0072] A2: The median particle size D50 is 35 μm, and the number average molecular weight is 100,000;

[0073] A3: The median particle size D50 is 58 μm, and the number average molecular weight is 80,000;

[0074] A4: The median particle size D50 is 20 μm, and the number average molecular weight is 100,000;

[0075] A5: The median particle size D50 is 85 μm, and the number average molecular weight is 50,000;

[0076] A6: The median particle size D50 is 66 μm, and the number average molecular weight is 80,000;

[0077] A7: The median particle size D50 is 82 μm, and the number average molecular weight is 150,000.

[0078] A8: The median particle size D50 is 150 μm, and the number average molecular weight is 120,000;

[0079] Main emulsifier B:

[0080] B1: Sodium dodecyl sulfonate, purity > 98%, purchased from Shanghai Hansi Chemical Co., Ltd.;

[0081] B2: Sodium dodecyl sulfate, purity > 95%, purchased from Jinan Century Tongda Chemical Co., Ltd.;

[0082] B3: Sodium dodecyl benzene sulfonate, purity > 95%, purchased from Jiangsu Qingting Chemical Co., Ltd.

[0083] Co-emulsifier:

[0084] C1: Span 80, purity > 95%, purchased from Shanghai Hansi Chemical Co., Ltd.;

[0085] C2: Tween 60, purity > 95%, purchased from Shanghai Hansi Chemical Co., Ltd.;

[0086] C3: Span 40, purity > 95%, purchased from Shanghai Hansi Chemical Co., Ltd.

[0087] C4: Tween 80, purity > 95%, purchased from Shanghai Hansi Chemical Co., Ltd.

[0088] Thickener D:

[0089] Thickener D1: Hydroxypropyl methylcellulose, purity > 99%, purchased from Hubei Dahao Chemical Co., Ltd.;

[0090] Thickener D2: Carboxymethyl cellulose, purity > 99%, purchased from Hubei Dahao Chemical Co., Ltd.;

[0091] Thickener D3: Hydroxyethyl cellulose, purity > 99%, purchased from Hubei Dahao Chemical Co., Ltd.

[0092] Example 1

[0093] Step 1: Weigh 0.8 parts by weight of thickener D1 and add it to 100 parts by weight of water. After stirring well at 45 °C for 90 min, a mixed solution I is obtained;

[0094] Step 2: Weigh 1.8 parts by weight of main emulsifier B1 and add it to the above mixed solution I. After stirring well at 45 °C for 30 min, a mixed emulsion II is obtained;

[0095] Step 3: Weigh 0.6 parts by weight of co-emulsifier C1 and add it to the above mixed emulsion II. After stirring well at 45 °C for 25 min, a mixed emulsion III is obtained;

[0096] Step 4: Weigh 7 parts by weight of polyglycolic acid A1 and add it to the above mixed emulsion III. After stirring well at 45 °C for 20 min, the environmentally friendly temporary plugging agent composition for fracturing is obtained.

[0097] Example 2

[0098] Step 1: Weigh 1 part by weight of thickener D2 and add it to 100 parts by weight of water. After stirring well at 20 °C for 120 min, a mixed solution I is obtained;

[0099] Step 2: Weigh 0.8 parts by weight of main emulsifier B2 and add it to the above mixed solution I. After stirring well at 20 °C for 25 min, a mixed emulsion II is obtained;

[0100] Step 3: Weigh 0.3 parts by weight of co-emulsifier C2 and add it to the above mixed emulsion II. After stirring well at 20 °C for 22 min, a mixed emulsion III is obtained;

[0101] Step 4: Weigh 3.5 parts by weight of polyglycolic acid A2 and add it to the above mixed emulsion III. After stirring well at 20 °C for 15 min, the environmentally friendly temporary plugging agent composition for fracturing is obtained.

[0102] Example 3

[0103] Step 1: Weigh 1.4 parts by weight of thickener D3 and add it to 100 parts by weight of water. After fully stirring at 37 °C for 115 min, a mixed solution I is obtained;

[0104] Step 2: Weigh 1.5 parts by weight of main emulsifier B3 and add it to the above-mentioned mixed solution I. After fully stirring at 37 °C for 10 min, a mixed emulsion II is obtained;

[0105] Step 3: Weigh 0.5 parts by weight of co-emulsifier C3 and add it to the above-mentioned mixed emulsion II. After fully stirring at 37 °C for 25 min, a mixed emulsion III is obtained;

[0106] Step 4: Weigh 4.2 parts by weight of polyglycolic acid A3 and add it to the above-mentioned mixed emulsion III. After fully stirring at 37 °C for 18 min, the environmentally friendly temporary plugging agent composition for fracturing is obtained.

[0107] Example 4

[0108] Step 1: Weigh 0.5 parts by weight of thickener D1 and add it to 100 parts by weight of water. After fully stirring at 55 °C for 60 min, a mixed solution I is obtained;

[0109] Step 2: Weigh 0.1 parts by weight of main emulsifier B2 and add it to the above-mentioned mixed solution I. After fully stirring at 55 °C for 15 min, a mixed emulsion II is obtained;

[0110] Step 3: Weigh 1 parts by weight of co-emulsifier C1 and add it to the above-mentioned mixed emulsion II. After fully stirring at 55 °C for 25 min, a mixed emulsion III is obtained;

[0111] Step 4: Weigh 5 parts by weight of polyglycolic acid A4 and add it to the above-mentioned mixed emulsion III. After fully stirring at 55 °C for 15 min, the environmentally friendly temporary plugging agent composition for fracturing is obtained.

[0112] Example 5

[0113] Step 1: Weigh 2 parts by weight of thickener D1 and add it to 100 parts by weight of water. After fully stirring at 50 °C for 150 min, a mixed solution I is obtained;

[0114] Step 2: Weigh 3 parts by weight of main emulsifier B1 and add it to the above-mentioned mixed solution I. After fully stirring at 50 °C for 18 min, a mixed emulsion II is obtained;

[0115] Step 3: Weigh 0.8 parts by weight of co-emulsifier C4 and add it to the above-mentioned mixed emulsion II. After fully stirring at 50 °C for 20 min, a mixed emulsion III is obtained;

[0116] Step 4: Weigh 10 parts by weight of polyglycolic acid A5 and add it to the above-mentioned mixed emulsion III. After stirring thoroughly at 50°C for 30 min, the environmentally friendly temporary plugging agent composition for fracturing is obtained.

[0117] Example 6

[0118] Step 1: Weigh 0.9 part by weight of thickener D3 and add it to 100 parts by weight of water. After stirring thoroughly at 60°C for 120 min, the mixed solution I is obtained.

[0119] Step 2: Weigh 2.2 parts by weight of main emulsifier B3 and add it to the above-mentioned mixed solution I. After stirring thoroughly at 60°C for 27 min, the mixed emulsion II is obtained.

[0120] Step 3: Weigh 0.1 part by weight of co-emulsifier C3 and add it to the above-mentioned mixed emulsion II. After stirring thoroughly at 60°C for 18 min, the mixed emulsion III is obtained.

[0121] Step 4: Weigh 1.8 parts by weight of polyglycolic acid A6 and add it to the above-mentioned mixed emulsion III. After stirring thoroughly at 60°C for 10 min, the environmentally friendly temporary plugging agent composition for fracturing is obtained.

[0122] Example 7

[0123] Implement according to the method of Example 1, and use polyglycolic acid A7 to replace polyglycolic acid A1.

[0124] Comparative Example 1

[0125] Implement according to the method of Example 1. Compared with Example 1, adjust the addition amount of thickener D1 to 0.2 part by weight.

[0126] Comparative Example 2

[0127] Implement according to the method of Example 1. Compared with Example 1, use polyglycolic acid A8 to replace polyglycolic acid A1.

[0128] Comparative Example 3

[0129] Compared with Example 1, adjust the feeding order in the preparation method, and add polyglycolic acid A1, main emulsifier B1, co-emulsifier C1 and thickener D1 simultaneously.

[0130] For the specific dosage of each component, see Table 1.

[0131] Table 1

[0132]

[0133] In a low-temperature reservoir at 55°C, the suspension stability, surface tension, temporary plugging pressure bearing, temporary plugging rate, residue rate, and crude oil recovery rate of the composition were tested. The test data of the temporary plugging agent composition are shown in Table 2.

[0134] Table 2

[0135]

[0136] It can be seen from Table 1 and Table 2 that compared with Example 1, the weight ratio of polyglycolic acid A to thickener D changes in Comparative Example 1; compared with Example 1, the particle size of polyglycolic acid A changes in Comparative Example 2; compared with Example 1, the feeding order during preparation changes in Comparative Example 3; the composition in Example 1 has high suspension stability, low surface tension, high system viscosity, and a more stable combination; the temporary plugging performance and degradation performance are also higher. The temporary plugging agent composition prepared by the present invention has good stability, degradation performance, and crude oil recovery rate.

[0137] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. An environmentally friendly temporary plugging agent composition for oilfield fracturing, characterized in that, The composition contains polyglycolic acid A, main emulsifier B, co-emulsifier C, thickener D and water; The median particle size D50 of the polyglycolic acid A is 20 - 100 μm; The weight ratio of the polyglycolic acid A to the thickener D is 2 - 10:

1.

2. The composition according to claim 1, wherein, Relative to 100 parts by weight of water, the content of the polyglycolic acid A is 1 - 10 parts by weight, the content of the main emulsifier B is 0.1 - 3 parts by weight, the content of the co-emulsifier C is 0.1 - 1 part by weight, and the content of the thickener D is 0.5 - 2 parts by weight; Preferably, relative to 100 parts by weight of water, the content of the polyglycolic acid A is 2 - 8 parts by weight, the content of the main emulsifier B is 0.8 - 2 parts by weight, the content of the co-emulsifier C is 0.2 - 0.7 part by weight, and the content of the thickener D is 0.8 - 1.5 parts by weight.

3. The composition according to claim 1 or 2, wherein, The weight ratio of the polyglycolic acid A to the thickener D is 3 - 9:1; Preferably, the median particle size D50 of the polyglycolic acid A is 20 - 80 μm; Preferably, the number-average molecular weight of the polyglycolic acid A is 50,000 - 150,000, preferably 50,000 - 100,000.

4. The composition according to any one of claims 1-3, wherein, The main emulsifier B is an anionic emulsifier; Preferably, the main emulsifier B is selected from at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate; Preferably, the co-emulsifier C is a non-ionic emulsifier; Preferably, the co-emulsifier C is selected from at least one of span 20, span 40, span 60, span 80, tween 20, tween 40, tween 60 and tween 80, preferably at least one of span 40, span 60, span 80, tween 40, tween 60 and tween 80; Preferably, the thickener D is a cellulose derivative; Preferably, the thickener D is selected from at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose and hydroxyethyl cellulose.

5. A preparation method of an environment-friendly temporary plugging agent composition for oilfield fracturing, characterized in that, The preparation method comprises the following steps: (1) Add the thickener D to water and carry out the first stirring to obtain a mixed solution I; (2) Add the main emulsifier B to the above-mentioned mixed solution I and carry out the second stirring to obtain a mixed emulsion II; (3) Add the co-emulsifier C to the above-mentioned mixed emulsion II and carry out the third stirring to obtain a mixed emulsion III; (4) Add the polyglycolic acid A to the above-mentioned mixed emulsion III and carry out the fourth stirring to obtain the environmentally friendly temporary plugging agent composition for oilfield fracturing; The median particle size D50 of the polyglycolic acid A is 20 - 100 μm; The weight ratio of the polyglycolic acid A to the thickener D is 2 - 10:

1.

6. The preparation method according to claim 5, wherein, Relative to 100 parts by weight of water, the content of the polyglycolic acid A is 1 - 10 parts by weight, the content of the main emulsifier B is 0.1 - 3 parts by weight, the content of the co-emulsifier C is 0.1 - 1 part by weight, and the content of the thickener D is 0.5 - 2 parts by weight; Preferably, relative to 100 parts by weight of water, the content of the polyglycolic acid A is 2 - 8 parts by weight, the content of the main emulsifier B is 0.8 - 2 parts by weight, the content of the co-emulsifier C is 0.2 - 0.7 part by weight, and the content of the thickener D is 0.8 - 1.5 parts by weight.

7. The preparation method according to claim 5 or 6, wherein The weight ratio of the polyglycolic acid A to the thickener D is 3 - 9:1; Preferably, the median particle size D50 of the polyglycolic acid A is 20 - 80 μm; Preferably, the number-average molecular weight of the polyglycolic acid A is 50,000 - 150,000, preferably 50,000 - 100,000.

8. The preparation method according to any one of claims 5-7, wherein, The main emulsifier B is an anionic emulsifier; Preferably, the main emulsifier B is selected from at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate; Preferably, the co-emulsifier C is a non-ionic emulsifier; Preferably, the co-emulsifier C is selected from at least one of Span 20, Span 40, Span 60, Span 80, Tween 20, Tween 40, Tween 60, and Tween 80, preferably at least one of Span 40, Span 60, Span 80, Tween 40, Tween 60, and Tween 80; Preferably, the thickener D is a cellulose derivative; Preferably, the thickener D is selected from at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl cellulose.

9. The preparation method according to any one of claims 5-8, wherein, The first stirring time is 60 - 150 min, and the temperature is 20 - 60 °C; more preferably, the first stirring time is 90 - 120 min, and the temperature is 30 - 50 °C; Preferably, the second stirring time is 10 - 30 min, and the temperature is 20 - 60 °C; more preferably, the second stirring time is 15 - 25 min, and the temperature is 30 - 50 °C; Preferably, the third stirring time is 10 - 30 min, and the temperature is 20 - 60 °C; more preferably, the third stirring time is 15 - 25 min, and the temperature is 30 - 50 °C; Preferably, the fourth stirring time is 10 - 30 min, and the temperature is 20 - 60 °C; more preferably, the fourth stirring time is 10 - 20 min, and the temperature is 30 - 50 °C.

10. An environmentally friendly temporary plugging agent composition for fracturing prepared by the preparation method according to claims 5 - 9.

11. Application of the environmentally friendly temporary plugging agent composition for fracturing according to any one of claims 1 - 4 and 10 in low-temperature reservoir fracturing operations.

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