Intelligent perforation temporary plugging material and preparation method thereof

Abstract

The application discloses a kind of intelligent perforation temporary plugging material and preparation method thereof.Intelligent perforation temporary plugging material includes the following mass percentage components: shear thickening fluid 17-24%, liquid temporary plugging agent 70-80%, isolating agent 3-6%;The shear thickening fluid includes the following mass percentage components: polyethylene glycol 46-73%, nano silicon dioxide 27-54%;The liquid temporary plugging agent includes the following mass percentage components: beta cyclodextrin 12-33%, fatty alcohol 2.5-18%, alkali metal salt 0.4-0.8%, cellulose 0.6-2.4%, and the balance is solvent.The intelligent perforation temporary plugging material provided by the application is liquid at normal times, solidifies and blocks when passing through perforation, can effectively block different positions and different shape perforations, and the temporary plugging material returns to the ground with flowback fluid when flowback, without residue in reservoir, suitable for various unconventional and low-permeability fracturing temporary plugging operations.

Description

Technical Field

[0001] This invention relates to the field of oil and gas extraction technology, and in particular to a smart borehole plugging material and its preparation method. Background Technology

[0002] Temporary plugging technology is an important technique for the efficient development of unconventional oil and gas reservoirs. In this technology, temporary plugging utilizes a plugging agent to effectively seal the perforation and fractures, followed by redirected fracturing to create one or more new fractures. This allows the fractures to expand, ultimately forming a new fracture network and achieving a larger fracture-induced volume. Currently, over 95% of the materials used for temporary plugging of fractures / perforations in major oilfields are plugging balls. Conventional perforations, due to the inherent perforation principle of the perforating projectile, tend to be irregular. As the fracturing proppant erodes the perforation, this irregularity in shape intensifies. Using plugging balls alone is insufficient to seal irregular perforations; multiple sizes of plugging particles are needed in conjunction with the plugging balls for sealing. However, the sealing effect on irregular perforations is still not ideal. Furthermore, the high density of plugging balls results in lower sealing efficiency for upper perforations. To address the various shortcomings of conventional temporary plugging balls, a knotted temporary plugging ball with a knot and tail fin structure has been developed domestically. Its tail fin forms a hydration layer upon contact with liquid, easily dispersing and expanding, improving the suspension of the plugging agent in the liquid and facilitating the sealing of upper boreholes. The knot can elastically deform, adaptively sealing irregular boreholes. Knotted temporary plugging balls are gradually gaining application due to their high efficiency in sealing boreholes. However, in field applications, the tail fin is prone to entanglement during the transport of the plugging agent from the wellhead to the bottom of the well, leading to plugging failure. Although this problem can be avoided by placing the knot inside the spherical shell, the presence of the shell reduces the high suspension of the knot, lowers the sealing efficiency of upper boreholes, and the degradation effect of the shell also affects the effective sealing of the knot. Therefore, there is a need for a temporary plugging material that can effectively seal boreholes of different locations and shapes. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides an intelligent temporary plugging material for blast holes and its preparation method. This invention employs a shear-thickening fluid blended with a liquid plugging agent. The high shear thickening of the liquid through the blast hole seals irregular blast holes, while the liquid plugging agent solidifies at formation temperatures, increasing the sealing strength. This results in an intelligent temporary plugging material capable of effectively sealing blast holes of different locations and shapes.

[0004] Firstly, the present invention provides an intelligent blast hole plugging material, which is achieved by the following technical solution.

[0005] A smart borehole plugging material comprises the following components by mass percentage: 17-24% shear-thickening fluid, 70-80% liquid plugging agent, and 3-6% release agent; The shear-thickening fluid comprises the following components by mass percentage: polyethylene glycol 46-73%, nano-silica 27-54%; The liquid temporary plugging agent comprises the following components by mass percentage: 12-33% β-cyclodextrin, 2.5-18% fatty alcohol, 0.4-0.8% alkali metal salt, 0.6-2.4% cellulose, with the balance being solvent.

[0006] Furthermore, the polyethylene glycol is selected from one or a combination of polyethylene glycol 200, polyethylene glycol 400, and polyethylene glycol 600.

[0007] Furthermore, the nano-silica is selected from gel-processed nano-silica with a particle size of 50-100 nm.

[0008] Furthermore, the fatty alcohol has 4-12 carbon atoms. Specifically, fatty alcohols include n-butanol, n-heptanol, n-octanol, n-nonanol, n-decanol, and lauryl alcohol.

[0009] Furthermore, the alkali metal salt is selected from one or a combination of lithium chloride, sodium chloride, and sodium carbonate.

[0010] Furthermore, the cellulose is selected from one or a combination of several of methylcellulose, carboxymethylcellulose, carboxyethylcellulose, and carboxypropylmethylcellulose.

[0011] Furthermore, the solvent is selected from one or a combination of several of methylformamide, dimethylformamide, and dimethylacetamide.

[0012] Furthermore, the separating agent is selected from one or a combination of several of polyvinylpyrrolidone, hyaluronic acid, dextran, and chitosan.

[0013] Secondly, the present invention provides a method for preparing a smart borehole plugging material, which is achieved by the following technical solution.

[0014] A method for preparing the above-mentioned intelligent borehole plugging material includes the following steps: S1. Slowly and evenly add nano-silica to polyethylene glycol, continuously stirring and ultrasonically dispersing it during the process. After the nano-silica is added, heat the mixture to defoam, and obtain solution A. S2. Add alkali metal salt, fatty alcohol, β-cyclodextrin and cellulose to the solvent in sequence, and stir until homogeneous to obtain solution B; S3. Slowly add the release agent to solution A and stir until homogeneous. Then, under high-speed stirring, slowly add the mixture dropwise to solution B to obtain the intelligent borehole plugging material.

[0015] Furthermore, in step S1, the temperature for heating and defoaming is 50-90℃.

[0016] Furthermore, in step S3, the stirring speed of the high-speed stirrer is 800-1800 rpm.

[0017] This application has the following beneficial effects: The intelligent borehole plugging material of this invention is a blend of shear-thickening fluid and liquid plugging agent. The shear-thickening fluid is a low-viscosity liquid under normal conditions. When the shear stress gradually increases, it exhibits shear thinning. When the critical shear stress is reached, the viscosity increases sharply, and it becomes solid. When the shear stress decreases, it slowly returns to a liquid state. The liquid plugging agent is a low-viscosity liquid at room temperature. When the temperature rises to a certain range, the viscosity increases sharply and solidifies. When the temperature continues to rise to another range, it returns to a low-viscosity, flowable state. However, because a large amount of low-temperature fluid enters the reservoir during fracturing operations and the temperature changes significantly, the solidification time of this liquid-solid phase change plugging agent is difficult to control, making it unsuitable for borehole plugging.

[0018] The shear-thickening fluid in the intelligent borehole plugging material of this invention generates high shear stress upon passing through the borehole. The fluid instantly solidifies and adaptively plugs irregular boreholes. The liquid plugging agent mixed with it gradually solidifies under the reservoir's heating of the fluid, enhancing the strength of the plugging body. The isolating agent separates the two fluids, preventing them from dissolving and affecting their respective functions. After fracturing operations are completed, the fluid stops impacting the borehole, and the shear-thickening fluid gradually returns to a liquid state. Once no new fluid is injected, the reservoir temperature stops decreasing and begins to rise, and the liquid plugging agent also returns to a liquid state. During flowback, the liquid plugging material returns to the surface with the flowback fluid, leaving no residue in the reservoir. The intelligent borehole plugging material of this invention is normally liquid, solidifying and plugging upon passing through the borehole. It can effectively plug boreholes of different locations and shapes, and is suitable for various unconventional and low-permeability fracturing plugging operations. Detailed Implementation

[0019] The present invention will be further described below with reference to the embodiments.

[0020] The nano-silica used in the following embodiments of the present invention is Jiangsu Xianfeng Nano XFF31; The polyvinylpyrrolidone used in the following embodiments of the present invention is Shandong Maina polyvinylpyrrolidone K12; The hyaluronic acid used in the following embodiments of the present invention is Wuhan Lanabai hyaluronic acid with a molecular weight of 100,000; The dextran used in the following embodiments of the present invention is Qingdao Taihai Rui Biotechnology hard dextran; The chitosan used in the following embodiments of the present invention is Zhejiang Jin Ke water-soluble chitosan hydrochloride with a molecular weight of 10,000; The methylcellulose used in the following embodiments of the present invention is Wuhan Jiyesheng methylcellulose with a molecular weight of 100,000; The carboxymethyl cellulose used in the following embodiments of the present invention is Wuhan Jiyesheng carboxymethyl cellulose with a molecular weight of 100,000; The carboxyethyl cellulose used in the following embodiments of the present invention is Wuhan Jiyesheng carboxyethyl cellulose with a molecular weight of 100,000; The carboxypropyl methylcellulose used in the following embodiments of the present invention is selected from Wuhan Jiyesheng carboxypropyl methylcellulose with a molecular weight of 100,000.

[0021] Example 1

[0022] A method for preparing a smart borehole plugging material includes the following steps: 9.18 kg of 100 nm nano-silica was slowly and evenly added to 7.82 kg of polyethylene glycol 200. During the process, stirring and ultrasonic vibration were continuously performed to disperse the mixture. After the nano-silica was added, the mixture was placed in a vacuum drying oven and heated to defoam, resulting in solution A.

[0023] 0.64 kg lithium chloride, 14.4 kg butanol, 26.4 kg β-cyclodextrin, and 1.92 kg methylcellulose were added sequentially to 36.64 kg dimethylformamide and stirred until homogeneous to obtain solution B.

[0024] 3 kg of polyvinylpyrrolidone was slowly added to solution A and stirred until homogeneous. Then, the mixture was slowly added dropwise to solution B under high-speed stirring to obtain a smart blast hole temporary sealing material.

[0025] Example 2

[0026] A method for preparing a smart borehole plugging material includes the following steps: 8 kg of 80 nm nano-silica was slowly and evenly added to 12 kg of polyethylene glycol 400. During the process, stirring and ultrasonic vibration were continuously performed to disperse the nano-silica. After the nano-silica was added, the mixture was placed in a vacuum drying oven and heated to defoam, resulting in solution A.

[0027] 0.532 kg of sodium chloride, 9.88 kg of heptanol, 19.76 kg of β-cyclodextrin, and 1.368 kg of carboxymethyl cellulose were added sequentially to 44.46 kg of dimethylacetamide and stirred until homogeneous to obtain solution B.

[0028] 4 kg of hyaluronic acid was slowly added to solution A and stirred until homogeneous. Then, the mixture was slowly added dropwise to solution B under high-speed stirring to obtain a smart borehole plugging material.

[0029] Example 3

[0030] A method for preparing a smart borehole plugging material includes the following steps: 7.48 kg of 70 nm nano-silica was slowly and evenly added to 14.52 kg of polyethylene glycol 600. During the process, stirring and ultrasonic vibration were continuously performed to disperse the mixture. After the nano-silica was added, the mixture was placed in a vacuum drying oven and heated to defoam, resulting in solution A.

[0031] 0.438 kg sodium carbonate, 5.84 kg decanol, 13.87 kg β-cyclodextrin, and 0.876 kg carboxyethyl cellulose were added sequentially to 51.976 kg methylformamide and stirred until homogeneous to obtain solution B.

[0032] 5 kg of dextran was slowly added to solution A and stirred until homogeneous. Then, the mixture was slowly added dropwise to solution B under high-speed stirring to obtain a smart blast hole plugging material.

[0033] Example 4

[0034] A method for preparing a smart borehole plugging material includes the following steps: 6.48 kg of 50 nm nano-silica was slowly and evenly added to 10 kg of polyethylene glycol 200 and 7.52 kg of polyethylene glycol 600. During the process, stirring and ultrasonic vibration dispersion were continuously carried out. After the nano-silica was added, the mixture was placed in a vacuum drying oven and heated to defoam, resulting in solution A.

[0035] 0.14 kg of lithium chloride, 0.14 kg of sodium chloride, 1.75 kg of lauryl alcohol, 8.4 kg of β-cyclodextrin, and 0.42 kg of carboxypropyl methylcellulose were added sequentially to 50 kg of dimethylformamide and 9.15 kg of methylformamide, and stirred until homogeneous to obtain solution B.

[0036] 6 kg of chitosan was slowly added to solution A and stirred until homogeneous. Then, the mixture was slowly added dropwise to solution B under high-speed stirring to obtain a smart blast hole plugging material.

[0037] Comparative Example 1 9.18 kg of 100 nm nano-silica was slowly and evenly added to 7.82 kg of polyethylene glycol 200. During the process, stirring and ultrasonic vibration were continuously performed to disperse the mixture. After the nano-silica was added, the mixture was placed in a vacuum drying oven and heated to defoam, resulting in solution A.

[0038] 0.64 kg lithium chloride, 14.4 kg butanol, 26.4 kg β-cyclodextrin, and 1.92 kg methylcellulose were added sequentially to 36.64 kg dimethylformamide and stirred until homogeneous to obtain solution B.

[0039] Solution A was slowly added dropwise to solution B under high-speed stirring to obtain a temporary plugging material for blast holes.

[0040] Comparative Example 2 0.8 kg lithium chloride, 18 kg butanol, 33 kg β-cyclodextrin, and 2.4 kg methylcellulose were added sequentially to 45.8 kg dimethylformamide and stirred evenly to obtain a temporary plugging material for blast holes.

[0041] Comparative Example 3 46 kg of 100 nm nano-silica was slowly and evenly added to 54 kg of polyethylene glycol 200. During the process, stirring and ultrasonic vibration were continuously performed to disperse the mixture. After the nano-silica was added, the mixture was placed in a vacuum drying oven and heated to defoam, thus obtaining a temporary plugging material for the blast hole.

[0042] Performance testing The performance of the borehole plugging materials prepared in Examples 1-4 and Comparative Examples 1-3 was evaluated using a large-scale, high-pressure borehole plugging device (see Wang Bo, Gu Xiaolong, Li Wenxia, ​​et al. Experimental study on the plugging law of irregular boreholes with strong erosion [J]. Journal of Xi'an Petroleum University (Natural Science Edition), 2023, 38(6): 46-53). The device includes a pumping system, a temporary plugging material injection system, a heating system, a data acquisition system, and a real casing containing the borehole. The maximum pumping discharge rate can reach 0.5 m. 3 The pumping speed was 30 MPa, and the evaluation results are shown in the table below:

[0043] The data in the table show that under different sealing pressures, Examples 1-4 can achieve complete and effective sealing. Comparative Example 1 did not use a release agent. After the two fluids were mixed, the effective components interacted, causing shear thickening and liquid-solid phase change failure, and thus could not solidify and seal. Comparative Example 2 only used a liquid-solid phase change temporary plugging agent, and its solidification process was relatively slow, so it could not effectively seal the borehole. Comparative Example 3 only used a shear thickening fluid, which could effectively seal at a lower sealing pressure, but as the sealing pressure increased, the strength of the solidified sealing body was insufficient, and the fluid broke through the seal, causing sealing failure.

[0044] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A smart borehole plugging material, characterized in that: It includes the following components by mass percentage: shear thickening fluid 17-24%, liquid plugging agent 70-80%, and release agent 3-6%; The shear-thickening fluid comprises the following components by mass percentage: polyethylene glycol 46-73%, nano-silica 27-54%; The liquid temporary plugging agent comprises the following components by mass percentage: 12-33% β-cyclodextrin, 2.5-18% fatty alcohol, 0.4-0.8% alkali metal salt, 0.6-2.4% cellulose, with the balance being solvent; the fatty alcohol has 4-12 carbon atoms; the alkali metal salt is selected from one or a combination of lithium chloride, sodium chloride, and sodium carbonate; the cellulose is selected from one or a combination of methylcellulose, carboxymethylcellulose, carboxyethylcellulose, and carboxypropylmethylcellulose; and the solvent is selected from one or a combination of methylformamide, dimethylformamide, and dimethylacetamide.

2. The intelligent borehole plugging material according to claim 1, characterized in that: The polyethylene glycol is selected from one or a combination of polyethylene glycol 200, polyethylene glycol 400, and polyethylene glycol 600.

3. The intelligent borehole plugging material according to claim 1, characterized in that: The nano-silica is selected from gel-processed nano-silica with a particle size of 50-100 nm.

4. The intelligent borehole plugging material according to claim 1, characterized in that: The separating agent is selected from one or a combination of several of the following: polyvinylpyrrolidone, hyaluronic acid, dextran, and chitosan.

5. A method for preparing the intelligent borehole plugging material according to any one of claims 1-4, characterized in that: Includes the following steps: S1. Slowly and evenly add nano-silica to polyethylene glycol, continuously stirring and ultrasonically dispersing it during the process. After the nano-silica is added, heat the mixture to defoam, and obtain solution A. S2. Add alkali metal salt, fatty alcohol, β-cyclodextrin and cellulose to the solvent in sequence, and stir until homogeneous to obtain solution B; S3. Slowly add the release agent to solution A and stir until homogeneous. Then, under high-speed stirring, slowly add the mixture dropwise to solution B to obtain the intelligent borehole plugging material.

6. The preparation method according to claim 5, characterized in that: In step S1, the temperature for heating and defoaming is 50-90℃.

7. The preparation method according to claim 5, characterized in that: In step S3, the stirring speed of the high-speed stirrer is 800-1800 rpm.

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