Polyglycolic acid modified material as well as preparation method and application thereof

Abstract

The invention relates to the field of polyglycolic acid modification and application, and discloses a polyglycolic acid modified material composition with temporary plugging and pressurizing performance, which comprises the following components in parts by weight: 60-90 parts of polyglycolic acid A, 6-31 parts of imbibition agent B, 0.1-1.2 parts of accelerant C and 2-10 parts of dispersing agent D, wherein the weight-average molecular weight of the polyglycolic acid A is 50-150 thousand g / mol. The polyglycolic acid modified material composition has the advantages of high impact strength, high compression strength, compression resistance higher than 30 MPa and pressure bearing time longer than 4 hours under the medium and low temperature oil reservoir geology (less than or equal to 65 DEG C) condition, achieves the purpose and effect of temporary plugging of new turnaround fracturing seams, accelerates degradation after 6 hours under the medium and low temperature oil reservoir condition after being injected into the stratum seams along with fracturing fluid, and has the advantages of low cost and high efficiency. And moreover, complete degradation can be realized within 72 hours, residues after degradation are less than 5%, blockage removal is not needed, no damage is caused to a stratum, and the productivity of an oil well can be obviously improved.

Description

Technical Field

[0001] This invention relates to the field of polyglycolic acid modification and application, specifically to a polyglycolic acid modified material and its application as a temporary plugging agent in oil and gas fields. Background Technology

[0002] With increasing global attention to plastic pollution, "reduction, recycling, reuse, and degradability" have become key measures for plastic pollution control. Among these, biodegradable plastics, as alternatives to plastic products, have gradually become a focus of attention, especially in the replacement of single-use plastics, where biodegradable plastics are highly anticipated. Currently, the polymers used on a large scale in biodegradable plastics are mainly polylactic acid (PLA) and polybutylene terephthalate (PBAT). PLA monomers are mainly derived from bio-based starch, while PBAT monomers are mainly derived from petroleum. However, as single-use plastics, PBAT and PLA still exhibit slow degradation rates in soil and seawater environments, failing to meet the requirements for rapid degradation. Polyglycolic acid (PGA) is the simplest aliphatic polyester in terms of structure. Researchers have prepared high-molecular-weight PGA using ring-opening polymerization of glycolide and used it as a biodegradable surgical suture. In 2010, a breakthrough was achieved in the technology of producing PGA from coal-based syngas, making the large-scale production of PGA from methyl glycolate a feasible process. This technology can significantly reduce the production cost of PGA, providing a strong guarantee for its industrialization. While PGA has good degradability, its degradation under medium- and low-temperature reservoir conditions is still relatively slow, failing to meet the requirements of on-site oilfield construction. Therefore, appropriately modifying the degradation performance of PGA has become crucial for its widespread application in oilfields.

[0003] Currently, the use of temporary plugging and reversible fracturing technology in oilfields is one of the important measures to improve oil well productivity. The key to this technology is creating new fractures, and the most important aspect of creating new fractures is selecting suitable temporary plugging materials to temporarily seal old formation fractures. After the new fractures are fracturing, the temporary plugging material automatically and completely degrades, releasing the old fractures and thus improving oil well productivity. PGA has been used to some extent as a temporary plugging material in high-temperature reservoirs both domestically and internationally, but its application in medium- and low-temperature reservoirs is limited, mainly because its slow degradation does not meet the requirements of on-site oilfield operations. Therefore, regulating the degradation performance of PGA materials to accelerate the degradation rate at medium and low temperatures and further expand its application in medium- and low-temperature reservoirs (≤65℃) will have a positive effect on improving oil recovery and increasing production efficiency in oilfields. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem of slow degradation of PGA in low-temperature reservoirs under existing technology, and to provide a polyglycolic acid modified material composition with temporary plugging and pressurization properties.

[0005] To achieve the above objectives, the first aspect of the present invention provides a polyglycolic acid modified material composition with temporary plugging and pressurization properties, characterized in that the composition comprises: 60-90 parts by weight of polyglycolic acid A, 6.8-31 parts by weight of permeabilizer B, 0.1-1.2 parts by weight of accelerator C, and 2-10 parts by weight of dispersant D; wherein the weight-average molecular weight of polyglycolic acid A is 50,000-150,000 g / mol.

[0006] A second aspect of the present invention provides a method for preparing a polyglycolic acid modified material, characterized in that the method comprises:

[0007] (1) Mix the above composition;

[0008] (2) The mixed materials are extruded and granulated to obtain polyglycolic acid modified material.

[0009] A third aspect of the present invention provides the application of a polyglycolic acid modified material prepared using the above-described composition and / or the above-described method as a temporary plugging agent in an oilfield.

[0010] Through the above technical solution, the present invention can achieve at least the following beneficial effects:

[0011] (1) The polyglycolic acid modified material composition of the present invention has high impact resistance and high compressive strength under medium and low temperature reservoir geological conditions (≤65℃), with a compressive strength higher than 30MPa and a pressure bearing time greater than 4 hours, thereby achieving the purpose and effect of temporarily plugging the new fractures in the diversion fracturing.

[0012] (2) The polyglycolic acid modified material composition of the present invention degrades rapidly after being injected into the formation fracture with fracturing fluid under medium and low temperature reservoir conditions for 6 hours, and can be completely degraded within 72 hours. The residue after degradation is less than 5%, no unblocking is required, and it does not damage the formation, which can significantly improve the oil well productivity. Detailed Implementation

[0013] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0014] The first aspect of this invention provides a polyglycolic acid modified material composition with temporary plugging and pressurization properties, characterized in that the composition comprises: 60-90 parts by weight of polyglycolic acid A, 6-31 parts by weight of percolator B, 0.1-1.2 parts by weight of accelerator C, and 2-10 parts by weight of dispersant D (based on a total composition of 100 parts by weight); wherein the weight-average molecular weight of polyglycolic acid A is 50,000-150,000 g / mol. In this invention, A, B, C, and D are merely designations to distinguish the components and have no special meaning.

[0015] In this invention, preferably, the composition comprises: 70-85 parts by weight of polyglycolic acid A, 10-25 parts by weight of permeabilizer B, 0.3-0.8 parts by weight of accelerator C, and 3-8 parts by weight of dispersant D; wherein the weight-average molecular weight of polyglycolic acid A is 60,000-120,000 g / mol.

[0016] In this invention, the structure of polyglycolic acid A is as follows:

[0017]

[0018] In this invention, the permeabilizer B is a substance that enhances the water permeability and diffusion of polyglycolic acid A, and is preferably selected from hydrophilic polymers.

[0019] The accelerator C can be a substance that can decompose into free radicals upon heating, and is preferably selected from organic peroxides.

[0020] The dispersant D can be a substance that has the functions of dispersing polyglycolic acid modified materials and helping water molecules penetrate into the interior of polyglycolic acid modified materials, preferably selected from anionic surfactants.

[0021] The present invention, through the synergistic effect of permeabilizer B, accelerator C and dispersant D, produces a polyglycolic acid modified material composition with temporary plugging and pressurization properties, which can achieve the purposes of temporary plugging and pressurization, directional fracturing and rapid degradation, and meet the field construction requirements of medium and low temperature reservoirs.

[0022] In this invention, preferably, the hydrophilic polymer is selected from at least one of starch, carboxymethyl cellulose, chitosan, gelatin, polyethylene glycol, polyoxyethylene, and polyacrylamide, and more preferably from at least one of starch, chitosan, gelatin, polyethylene glycol, polyoxyethylene, and polyacrylamide.

[0023] In this invention, preferably, the organic peroxide is selected from at least one of diisopropyl peroxide, benzoyl peroxide, tert-butyl peroxide, dicumyl peroxide, and methyl ethyl ketone peroxide, and more preferably at least one of diisopropyl peroxide, benzoyl peroxide, and tert-butyl peroxide.

[0024] In this invention, preferably, the anionic surfactant is selected from at least one of dodecyl sulfonate, dodecylbenzene sulfonate and dodecyl sulfate, and more preferably from at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate and sodium dodecylbenzene sulfonate.

[0025] A second aspect of the present invention provides a method for preparing a polyglycolic acid modified material, characterized in that the method comprises:

[0026] (1) Mix the above composition;

[0027] (2) The mixed materials are extruded and granulated to obtain polyglycolic acid modified materials.

[0028] In this invention, the mixing time is 5-10 minutes, and preferably, a high-speed mixer is used for mixing.

[0029] In this invention, the extrusion can be performed using a commonly used extruder, such as a twin-screw extruder.

[0030] In this invention, preferably, the extrusion temperature is 200-230°C, and the material extrusion time is 2-5 minutes. In a preferred embodiment of this invention, the material extrusion time can be the time the material stays in the base.

[0031] In this invention, the granulation is not particularly limited, as long as the material extruded by the extruder can be processed into particles of the corresponding particle size.

[0032] A third aspect of the present invention provides the application of a polyglycolic acid modified material prepared using the above-described composition and / or the above-described method as a temporary plugging agent in an oilfield.

[0033] In this invention, there are no special requirements for the particle size of the polyglycolic acid modified material, as long as it can meet the requirements of oilfield reservoir conditions and fracturing operations. For example, after the polyglycolic acid modified material is processed by an impact mill (model FC100), the median particle size (D50) is 10-1000μm.

[0034] The present invention will be described in detail below through examples. Unless otherwise specified in the following examples and comparative examples, conditions were performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available products. All molecular weights listed below are weight-average molecular weights.

[0035] The polyglycolic acid raw material is a commercially available injection-molding grade product from Inner Mongolia Pujing Chemical Technology Co., Ltd.

[0036] Carboxymethyl cellulose is from Shanghai Guanchuang Biotechnology Co., Ltd., with a purity of 98%.

[0037] The starch is from Shanghai Jizhi Biochemical Technology Co., Ltd., with a purity of 98%.

[0038] Chitosan was produced by Shenzhen Zhenqiang Biotechnology Co., Ltd., with a purity of 95%.

[0039] The gelatin is from Xi'an Longmao Biotechnology Co., Ltd., and has a purity of 99%.

[0040] The polyethylene glycol is from Nantong Runfeng Petrochemical Co., Ltd., with a molecular weight of 2000.

[0041] Benzoyl peroxide was supplied by Shanghai Aladdin Reagent Co., Ltd., with a purity of 99%.

[0042] Diisopropyl peroxide dicarbonate was supplied by Shanghai Aladdin Reagent Co., Ltd., with a purity of 99%.

[0043] The tert-butyl peroxide was supplied by Shanghai Aladdin Reagent Co., Ltd., with a purity of 99%.

[0044] The dicumyl peroxide was supplied by Shanghai Aladdin Reagent Co., Ltd., with a purity of 99%.

[0045] The methyl ethyl ketone peroxide was supplied by Shanghai Aladdin Reagent Co., Ltd., with a purity of 99%.

[0046] Sodium dodecylbenzenesulfonate is supplied by Jiangsu Qingting Chemical Co., Ltd., with a purity of 90%.

[0047] Sodium dodecyl sulfonate was supplied by Hubei Hanwei Chemical Co., Ltd., with a purity of 99%.

[0048] Sodium dodecyl sulfate was supplied by Hubei Hanwei Chemical Co., Ltd., with a purity of 99%.

[0049] Examples 1-18

[0050] (1) Polyglycolic acid A, permeation agent B, accelerator C and dispersant D are added to a high-speed mixer and mixed for a mixing time of t. 混合 ;

[0051] (2) The above mixture is injected into a twin-screw extruder for melt blending modification. The residence time of the mixture in the extruder is t. 停留 The extruder temperature is T;

[0052] (3) After the extruded strip material is rapidly cooled by water at 15°C, it is fed into a granulator for granulation. After drying at 50°C for about 5.5 hours, polyglycolic acid modified granules are obtained.

[0053] The specific reaction parameters, raw material selection and dosage are shown in Table 1.

[0054] Comparative Example 1

[0055] Temporary plugging agent particles were prepared according to the preparation method of Example 1, except that the amount of absorbent B added was 33g.

[0056] Comparative Example 2

[0057] Temporary plugging agent particles were prepared according to the preparation method of Example 1, except that the molecular weight of polyglycolic acid was 30,000 g / mol.

[0058] Comparative Example 3

[0059] Temporary plugging agent particles were prepared according to the preparation method of Example 1, except that accelerator C was not added.

[0060] Comparative Example 4

[0061] Temporary plugging agent particles were prepared according to the preparation method of Example 1, except that polylactic acid with a weight average molecular weight of 120,000 was used instead of polyglycolic acid A with a weight average molecular weight of 120,000.

[0062] Table 1

[0063]

[0064] Continued from Table 1

[0065]

[0066]

[0067] Continued from Table 1

[0068]

[0069] Test case

[0070] The polyglycolic acid modified materials prepared in the examples and comparative examples were tested for pressure bearing capacity and pressure bearing time on a core flow test device according to the following steps:

[0071] 1.0g of 20-40 mesh quartz sand was packed into a stainless steel wedge core and compacted. Then, 2.0g of temporary plugging agent particles were added and compacted again. The core was then placed in a core holder and placed in a core flow device at a set temperature. Ring pressure was applied (initial ring pressure > 3MPa), and proppant was injected at a flow rate of 2.0mL / min (the ring pressure was always kept 2-3MPa higher than the injection pressure as the injection pressure increased). The injection flow rate was gradually reduced as the injection pressure increased (1.0mL / min at 10MPa, 0.5mL / min at 15MPa, and 0.1mL / min at 20MPa). The pressure at which the pressure no longer increased at a flow rate of 0.1mL / min was the temporary plugging pressure. Timing was started from this point until the pressure dropped rapidly, and this was recorded as the pressure bearing time at that pressure.

[0072] Residue test after 72h degradation: Weigh about 2.0g of temporary plugging agent particles and record the mass as m1. Put them into a hydrothermal reactor containing 50mL of pure water, and then place them in an oven at a certain temperature. After 72h, take them out, filter and dry them, and weigh the mass of the residual material and record it as m2. Residue content = (m2 / m1)×100%.

[0073] The test temperature and test results are shown in Table 2.

[0074] Table 2

[0075]

[0076]

[0077] A comparison of Examples 1 and 6, 8, and 10 shows that when the amounts of dispersant D, accelerator C, and permeabilizer B are below the preferred range, the resulting polyglycolic acid modified material composition, although having a temporary plugging pressure higher than 40 MPa under reservoir geological conditions at 50°C, shows that after being injected into the formation fractures with fracturing fluid, the residue after 6 hours at 50°C and then degraded for 72 hours increases from 3.5% by weight in Example 1 to 4.8-4.9% by weight. A comparison of Examples 1 and 7, 9, and 11 shows that when the amounts of dispersant D, accelerator C, and permeabilizer B are below the preferred range, the resulting polyglycolic acid modified material composition, although having a temporary plugging pressure higher than 40 MPa under reservoir geological conditions at 50°C, shows that after being injected into the formation fractures with fracturing fluid, the residue after 6 hours at 50°C and then degraded for 72 hours increases from 3.5% by weight in Example 1 to 4.8-4.9% by weight. When the dosage is higher than the preferred range, the resulting polyglycolic acid modified material composition, although the residue after 72 hours of degradation is less than 3.5% by weight, shows that the temporary plugging pressure is reduced from 45.5 MPa in Example 1 to below 37 MPa. Examples 12-14 show that when the dosage or molecular weight of polyglycolic acid A is not within the preferred range, it also leads to a corresponding decrease in temporary plugging pressure or degradation capacity. Examples 5 and 15-17 show that when the selection of substances in the composition is not within the preferred range, it also leads to a corresponding decrease in temporary plugging pressure or degradation capacity. However, the polyglycolic acid modified material compositions prepared in Examples 1-17 all achieved a compressive strength higher than 30 MPa and a pressure-bearing time greater than 4 hours under medium-low temperature reservoir geological conditions (≤65℃). Furthermore, after being injected into the formation fractures with fracturing fluid, under medium-low temperature reservoir conditions, the residue after degradation within 72 hours is less than 5% after 6 hours of degradation.

[0078] 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 inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A composition for use in polyglycolic acid modified materials with temporary pressure boosting properties, characterized in that, The composition comprises: polyglycolic acid A, permeabilizer B, accelerator C, and dispersant D, wherein the content of polyglycolic acid A is 60-90 parts by weight, the content of permeabilizer B is 6-31 parts by weight, the content of accelerator C is 0.1-1.2 parts by weight, and the content of dispersant D is 2-10 parts by weight; wherein the weight average molecular weight of polyglycolic acid A is 50,000-150,000 g / mol.

2. The composition according to claim 1, wherein, The content of polyglycolic acid A is 70-85 parts by weight; And / or, the content of permeabilizer B is 10-25 parts by weight; And / or, the content of accelerator C is 0.3-0.8 parts by weight; And / or, the content of dispersant D is 3-8 parts by weight; And / or, the weight-average molecular weight of the polyglycolic acid A is 60,000 to 120,000 g / mol.

3. The composition according to claim 1 or 2, wherein, The permeating agent B is selected from hydrophilic polymers; And / or, the accelerator C is selected from organic peroxides; And / or, the dispersant D is selected from anionic surfactants.

4. The composition according to claim 3, wherein, The hydrophilic polymer is selected from at least one of starch, carboxymethyl cellulose, chitosan, gelatin, polyethylene glycol, polyoxyethylene, and polyacrylamide, preferably at least one of starch, chitosan, gelatin, polyethylene glycol, polyoxyethylene, and polyacrylamide.

5. The composition according to claim 3, wherein, The organic peroxide is selected from at least one of diisopropyl peroxide, benzoyl peroxide, tert-butyl peroxide, diisopropylbenzene peroxide, and methyl ethyl ketone peroxide, preferably at least one of diisopropyl peroxide, benzoyl peroxide, and tert-butyl peroxide.

6. The composition according to claim 3, wherein, The anionic surfactant is selected from at least one of dodecyl sulfonate, dodecylbenzene sulfonate and dodecyl sulfate, preferably at least one of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate and sodium dodecyl sulfate.

7. A method for preparing a polyglycolic acid modified material, characterized in that, The method includes: (1) Mixing the composition according to any one of claims 1-6; (2) The mixed materials are extruded and granulated to obtain polyglycolic acid modified materials.

8. The preparation method according to claim 7, wherein, The mixing time is 5-10 minutes; Preferably, the extrusion temperature is 200-230℃, and the material extrusion time is 2-5 minutes.

9. The polyglycolic acid modified material prepared by the method of claim 7 or 8.

10. The use of the composition according to any one of claims 1-6 and / or the polyglycolic acid modified material according to claim 9 as a temporary plugging agent in oil fields.

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