A method for evaluating the shape memory plugging performance of one-way shape memory polymers

Abstract

The present invention provides a method for evaluating the shape memory plugging performance of a one-way shape memory polymer. The present invention evaluates the shape memory performance of shape memory polymer plugging particles by testing the change in particle size before and after shape fixation. Simultaneously, testing the compressive strength of particles prepared under different conditions can also evaluate their plugging performance. The recovery rate and fixation rate are then accurately calculated. Finally, the shape memory plugging performance of the shape memory polymer plugging material is comprehensively evaluated using shape memory plugging performance evaluation indicators. The evaluation method of the present invention is simple to operate and convenient to calculate. Testing and evaluation can be performed in the laboratory without requiring operators to perform a large amount of complex work. The principle is reliable, the data is accurate, authentic, and effective, and the applicability is wide. It can truly reflect the shape memory plugging situation of the shape memory polymer plugging material, achieve evaluation of its shape memory plugging performance, and provide theoretical support for the subsequent research and development of shape memory polymer plugging materials.

Description

Technical Field

[0001] The invention relates to a method for evaluating the shape memory plugging performance of a unidirectional shape memory polymer, and belongs to the technical field of oil and gas drilling. Background Art

[0002] In oil and gas exploration and development, the fundamental goal of plugging leaks is to seal the leaking layer and ensure the smooth implementation of subsequent oil and gas development work. Traditional inert bridging plugging materials in various shapes (mainly granular, flaky and fibrous) such as hulls, cottonseed shells, calcium carbonate, etc. are widely used on-site due to their low cost. However, they are very rigid and not easy to deform, and they are poorly matched with the crack size, making them prone to "sealing the door" and "re-leakage". Although expandable materials can alleviate the above problems due to their variable volume, their expansion rate is difficult to control, and expansion that is too early or too late will reduce the success rate of plugging. Although delayed expansion plugging materials can slow down their expansion rate, their reduced strength after expansion limits their further application.

[0003] Shape memory materials are an important type of intelligent material that can sense changes in the external environment and adapt their physical parameters. Shape memory polymers, after acquiring an initial shape, undergo deformation and shape fixation, and can then return to their original shape under external stimuli such as heat, light, electricity, alternating magnetic fields, and solutions. One-way thermotropic shape memory polymers can return to their original shape above their glass transition temperature. These shape-adjustable, high-strength materials exhibit excellent compatibility with drilling fluids and have been successfully applied in drilling fluid plugging, effectively addressing the aforementioned issues. One-way thermotropic shape memory polymer plugging materials have been extensively researched in drilling fluid plugging, with most being epoxy resin-based shape memory materials. However, their shape memory performance is often measured by the ratio of the difference between the fixed angle and the recovered angle at different temperatures to the fixed angle. This evaluation method is limited, and the particle size, a common indicator used in plugging operations, makes it difficult to accurately reflect the shape memory and plugging performance of the plugging material.

[0004] Therefore, it is necessary to develop a method for evaluating the shape memory performance and plugging performance of shape memory plugging materials that is simple to operate, convenient to calculate, and accurate, so as to truly reflect the shape memory plugging performance of the shape memory plugging materials. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention provides a method for evaluating the shape memory plugging performance of unidirectional shape memory polymers. This method comprehensively evaluates the changes in particle size and compressive strength of the shape memory plugging material before and after shape memory. The method is simple to operate, convenient to calculate, and effective. It can truly reflect the shape memory plugging performance of the shape memory plugging material, effectively evaluating the shape memory plugging performance of the shape memory polymer plugging material and providing technical support for subsequent research on shape memory polymer plugging materials.

[0006] The technical solutions of the present invention are as follows:

[0007] A method for evaluating the shape memory plugging performance of a one-way shape memory polymer comprises the following steps:

[0008] (1) Prepare a shape memory polymer; test the glass transition temperature Tg (in °C) of the material, crush it into particles after drying, place it at Tg+20 °C to release the stress in the particles, and then cool it to room temperature. Measure the particle size of the particles, which is recorded as R 初 (unit: mm);

[0009] (2) According to step (1), make a particle size of R 初 The shape memory polymer particles are compressed by a hot pressing machine at Tg+20℃, and the particle size is measured and recorded as R 固 (unit: mm);

[0010] (3) Prepare shape memory polymer particles according to the method of step (2), and then prepare drilling fluid base slurry containing shape memory polymer particles; use simulated crack plugging test to test the particle size R 初 and R 固 The compressive strength τ1 and τ2 of the shape memory polymer particles at Tg (in MPa) are measured, and the particle size of the blocking layer formed at Tg is measured, which is recorded as R 回 (unit: mm);

[0011] (4) Calculate the shape recovery rate α of the shape memory polymer plugging material using formulas i, ii, and iii 回复率 , shape fixation rate β 固定率 and the pressure multiple γ;

[0012] Shape recovery rate:

[0013] Shape fixity:

[0014] Pressure multiples:

[0015] (5) The shape recovery rate α calculated according to step (4) 回复率 , shape fixation rate β 固定率 The shape memory plugging performance of shape memory polymer plugging materials was evaluated by the pressure bearing multiple γ. The evaluation indicators are as follows:

[0016] When α 回复率 ≤100%, 40%≤β 固定率 , γ≥200%, shape memory plugging performance: excellent;

[0017] When 90%≤α回复率 、30%≤β 固定率 ,γ≥180%, shape memory plugging performance: excellent;

[0018] When 70%≤α 回复率 , 20%≤β 固定率 ,γ≥150%, shape memory plugging performance: good;

[0019] When 50%≤α 回复率 , 10%≤β 固定率 ,γ≥130%, shape memory plugging performance: medium;

[0020] When 0≤α 回复率 , 0≤β 固定率 When γ≥0, shape memory plugging performance: poor.

[0021] According to a specific embodiment of the present invention, preferably, in step (1), the preparation of the shape memory polymer plugging system varies according to the different shape memory polymer synthetic materials, and its glass transition temperature Tg also varies accordingly.

[0022] According to a specific embodiment of the present invention, preferably, in step (1), Tg is obtained by testing the thermal decomposition trend of the synthesized shape memory polymer using a differential scanning calorimeter, and the particle size is measured using a particle size analyzer.

[0023] According to a specific embodiment of the present invention, preferably, in step (2), when a hot pressing machine is used for compression, the compression pressure and time are 20 MPa and 30 min, respectively.

[0024] According to a specific embodiment of the present invention, preferably, in step (3), the fracture model may use fracture models of different sizes to simulate different fractured strata according to actual needs.

[0025] According to a specific embodiment of the present invention, preferably, in step (3), the particle size of the shape memory polymer particles is one-third of the size of the crack model, and the particle size is uniform.

[0026] According to a specific embodiment of the present invention, preferably, in step (3), the drilling fluid base slurry is a bentonite base slurry, which is prepared by selecting evaluation soil for drilling fluid testing and preparing a 4% bentonite base slurry. The specific method is as follows: take 4 parts of bentonite, slowly add it to 100 parts of distilled water, stir for 2 hours, and let it stand for 24 hours to obtain the bentonite base slurry.

[0027] According to a specific embodiment of the present invention, preferably, in step (3), the test sample, i.e., the drilling fluid base slurry containing shape memory polymer particles, is prepared by dispersing the shape memory polymer particles in the base slurry, with a concentration ranging from 5% to 30%, and an optimal concentration of 8% to 25%.

[0028] According to a specific embodiment of the present invention, preferably, in step (3), the test method of the pressure strength τ is as follows: a drilling fluid base slurry containing shape memory polymer particles is placed in a high-temperature, high-pressure dynamic and static leakage tester and transported through a fracture model at a test temperature. When no plugging layer is formed, the outlet leakage is large; as the particles migrate, the leakage gradually decreases until it remains constant; and the pressure of the plugging tester is slowly increased until a large amount of leakage suddenly occurs. The corresponding pressure is the pressure strength τ.

[0029] Beneficial effects:

[0030] (1) The present invention provides a method for evaluating the shape memory plugging performance of a shape memory polymer plugging material. The present invention evaluates the shape memory performance of the shape memory polymer plugging particles by testing the change in particle size before and after the shape is fixed. At the same time, the plugging performance can also be evaluated by testing the compressive strength of the particles prepared under different conditions. Then, the recovery rate and fixation rate are accurately obtained by calculation. Finally, the shape memory plugging performance of the shape memory polymer plugging material is comprehensively evaluated by the shape memory plugging performance evaluation index. The evaluation method of the present invention is simple to operate and convenient to calculate. It can be tested and evaluated in the laboratory without the operator having to perform a lot of complicated work. Its principle is reliable, the data is accurate, true and effective, and it has wide applicability. It can truly reflect the shape memory plugging situation of the shape memory polymer plugging material, realize its shape memory plugging performance evaluation, and provide theoretical support for the subsequent research and development of the shape memory polymer plugging material.

[0031] (2) The present invention uses three indicators, namely, shape recovery rate, shape fixation rate and pressure bearing multiple, to comprehensively evaluate the shape memory plugging performance of shape memory polymer plugging materials. It can fully evaluate the shape memory plugging performance of shape memory polymer plugging materials from multiple angles and ensure the authenticity and validity of the evaluation results. The present invention obtains shape memory plugging performance evaluation indicators through a large number of experimental investigations. The indicator evaluation results are accurate and can intuitively evaluate the shape memory plugging performance of shape memory plugging materials. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to specific examples, but is not limited thereto.

[0033] The raw materials used in the examples are all conventional raw materials and can be obtained commercially; the methods described are all conventional methods and existing technologies unless otherwise specified.

[0034] Example 1

[0035] A method for evaluating the shape memory plugging performance of a shape memory polymer plugging material, comprising the following steps:

[0036] (1) Preparation of shape memory polymer: 100 parts of epoxy resin and 15 parts of 4,4'-diaminodiphenylmethane were mixed at 60°C, poured into a mold, and cured at 80°C for 2 hours, and then cured at 150°C for 2 hours to obtain a shape memory polymer. The glass transition temperature Tg of the material was measured to be 80°C. The material was crushed into particles, then placed at 100°C to release the stress in the particles, and then cooled to room temperature. The particle size of the particles was measured to be 0.32 mm, recorded as R 初 ;

[0037] (2) According to step (1), make a particle size of R 初 The shape memory polymer particles were compressed by a hot pressing machine at 100°C and 20 MPa for 30 min, and the particle size was measured to be 0.18 mm, which was recorded as R 固 ;

[0038] (3) Shape memory polymer particles were prepared according to the method of step (2), and then a drilling fluid base slurry containing shape memory polymer particles was prepared, namely: 4 parts of bentonite were slowly added to 100 parts of distilled water and stirred for 2 hours, and then allowed to stand for 24 hours to obtain a bentonite base slurry. Finally, 15 parts of shape memory polymer particles were mixed evenly with 100 parts of bentonite base slurry to obtain a shape memory polymer particle; a high temperature and high pressure displacement experiment was carried out using a steel crack model with a crack width of 1 mm, and the particle sizes of R 初 and R 固 The compressive strength τ1 and τ2 of the shape memory polymer particles at 80°C are tested by placing the drilling fluid base slurry containing the shape memory polymer particles in a high-temperature and high-pressure dynamic and static leakage tester. At the test temperature, the particles migrate through the fracture model. When no plugging layer is formed, the outlet leakage is large; as the particles migrate, the leakage gradually decreases until it remains constant; the pressure of the plugging tester is slowly increased until a large amount of leakage suddenly occurs. The corresponding pressure is the compressive strength, so τ1 and τ2 are 3.1 and 7.8 MPa respectively, and the particle size is measured. 固 The particle size of the shape memory polymer particles forming the plugging layer at 80°C is denoted as R 回 , is 0.31mm;

[0039] (4) Calculate the shape recovery rate α of the shape memory polymer plugging material using formulas i and ii 回复率 , shape fixation rate β 固定率 and the pressure multiple γ;

[0040] Shape recovery rate: Shape fixity:

[0041] Pressure multiples:

[0042] (5) The shape memory plugging performance of the shape memory polymer plugging material is evaluated based on the shape recovery rate α, shape fixation rate β, and pressure bearing multiple γ calculated in step (4). The evaluation indicators are as follows:

[0043] When α recovery rate ≤ 100%, 40% ≤ β fixation rate, γ ≥ 200%, shape memory plugging performance: excellent;

[0044] When 90%≤α recovery rate, 30%≤β fixation rate, γ≥180%, shape memory plugging performance: excellent;

[0045] When 70%≤α recovery rate, 20%≤β fixation rate, γ≥150%, shape memory plugging performance: good;

[0046] When 50%≤α recovery rate, 10%≤β fixation rate, γ≥130%, shape memory plugging performance: medium;

[0047] When 0≤α recovery rate, 0≤β fixation rate, and γ≥0, shape memory plugging performance: poor.

[0048] It can be seen from the above calculation results and evaluation indicators that the shape memory polymer plugging material involved in this embodiment has excellent shape memory plugging performance.

[0049] Example 2

[0050] A method for evaluating the shape memory plugging performance of a shape memory polymer plugging material, comprising the following steps:

[0051] (1) Preparation of shape memory polymer: 100 parts of epoxy resin and 20 parts of 4,4'-diaminodiphenylmethane were mixed at 60°C, poured into a mold, and cured at 80°C for 2 hours, and then cured at 150°C for 2 hours to obtain a shape memory polymer. The glass transition temperature Tg of the material was measured to be 100°C. The material was crushed into particles, and then placed at 100°C to release the stress in the particles. The particles were then cooled to room temperature. The particle size was measured to be 0.32 mm, recorded as R 初 ;

[0052] (2) According to step (1), make a particle size of R 初 The shape memory polymer particles were compressed by a hot pressing machine at 120°C and 20 MPa for 30 minutes, and the particle size was measured to be 0.25 mm, which was recorded as R 固 .

[0053] (3) Shape memory polymer particles were prepared according to the method of step (2), and then a drilling fluid base slurry containing shape memory polymer particles was prepared, namely: 4 parts of bentonite were slowly added to 100 parts of distilled water and stirred for 2 hours, and then allowed to stand for 24 hours to obtain a bentonite base slurry. Finally, 15 parts of shape memory polymer particles were mixed evenly with 100 parts of bentonite base slurry to obtain a shape memory polymer particle; a high temperature and high pressure displacement experiment was carried out using a steel crack model with a crack width of 1 mm, and the particle sizes of R 初 and R 固 The compressive strength τ1 and τ2 of the shape memory polymer particles at 100°C are tested by placing the drilling fluid base slurry containing the shape memory polymer particles in a high-temperature and high-pressure dynamic and static leakage tester. At the test temperature, the particles migrate through the fracture model. When no plugging layer is formed, the outlet leakage is large; as the particles migrate, the leakage gradually decreases until it remains constant; the pressure of the plugging tester is slowly increased until a large amount of leakage suddenly occurs. The corresponding pressure is the compressive strength, so τ1 and τ2 are 3.3 and 3.4 MPa respectively, and the particle size is measured to be R 固 The particle size of the shape memory polymer particles forming the plugging layer at 100°C is denoted as R 回 , is 0.3mm;

[0054] (4) Calculate the shape recovery rate α of the shape memory polymer plugging material using formulas i and ii 回复率 , shape fixation rate β 固定率 and the pressure multiple γ;

[0055] Shape recovery rate: Shape fixity:

[0056] Pressure multiples:

[0057] (5) The shape recovery rate α calculated according to step (4) 回复率 , shape fixation rate β 固定率 The shape memory plugging performance of shape memory polymer plugging materials was evaluated by the pressure bearing multiple γ. The evaluation indicators are as follows:

[0058] When α recovery rate ≤ 100%, 40% ≤ β fixation rate, γ ≥ 200%, shape memory plugging performance: excellent;

[0059] When 90%≤α recovery rate, 30%≤β fixation rate, γ≥180%, shape memory plugging performance: excellent;

[0060] When 70%≤α recovery rate, 20%≤β fixation rate, γ≥150%, shape memory plugging performance: good;

[0061] When 50%≤α recovery rate, 10%≤β fixation rate, γ≥130%, shape memory plugging performance: medium;

[0062] When 0≤α recovery rate, 0≤β fixation rate, and γ≥0, shape memory plugging performance: poor.

[0063] It can be seen from the above calculation results and evaluation indicators that the shape memory polymer plugging material involved in this embodiment has poor shape memory plugging performance.

Claims

1. A method for evaluating the shape memory plugging performance of a one-way shape memory polymer, comprising: (1) Preparation of shape memory polymers; The glass transition temperature Tg of the material was tested, and after drying, the material was crushed into particles. The particles were then placed at Tg+20°C to release the stress in the particles. The particles were then cooled to room temperature and the particle size was measured and recorded as R. 初 ; (2) According to step (1), make a particle size of R 初 The shape memory polymer particles are compressed by a hot pressing machine at Tg+20℃, and the particle size is measured and recorded as R 固 ; (3) Prepare shape memory polymer particles according to the method of step (2), and then prepare drilling fluid base slurry containing shape memory polymer particles; use simulated crack plugging test to test the particle size R 初 and R 固 The compressive strength τ1 and τ2 of the shape memory polymer particles at Tg are measured, and the particle size of the blocking layer formed at Tg is measured and recorded as R 回 ; Wherein, the drilling fluid base slurry containing shape memory polymer particles is prepared by dispersing the shape memory polymer particles in a bentonite base slurry with a concentration of 4%, and the concentration range is 5%-30%; The test method for the compressive strength τ is as follows: a drilling fluid base slurry containing shape memory polymer particles is added to a high-temperature, high-pressure, dynamic and static leakage tester. Under the test temperature, the particles migrate through a fracture model. When no plugging layer is formed, the outlet leakage is large. As the particles migrate, the leakage gradually decreases until it remains constant. The pressure in the plugging tester is slowly increased until a sudden large amount of leakage occurs. The corresponding pressure is the compressive strength τ. (4) Calculate the shape recovery rate α of the shape memory polymer plugging material using formulas i, ii, and iii 恢复率 , shape fixation rate β 固定率 and the pressure multiple γ; Shape recovery rate: Shape fixity: Pressure multiples: (5) The shape recovery rate α calculated according to step (4) 恢复率 , shape fixation rate β 固定率 The shape memory plugging performance of shape memory polymer plugging materials was evaluated by the pressure bearing multiple γ. The evaluation indicators are as follows: When α 恢复率 ≤100%, 40%≤β 固定率 , γ≥200%, shape memory plugging performance: excellent; When 90%≤α 恢复率 、30%≤β 固定率 , γ≥180%, shape memory plugging performance: excellent; When 70%≤α 恢复率 , 20%≤β 固定率 ,γ≥150%, shape memory plugging performance: good; When 50%≤α 恢复率 , 10%≤β 固定率 ,γ≥130%, shape memory plugging performance: medium; When 0≤α 恢复率 , 0≤β 固定率 When γ≥0, shape memory plugging performance: poor.

2. The method according to claim 1, wherein in step (1), the preparation of the shape memory polymer plugging system varies according to the shape memory polymer synthetic material, and its glass transition temperature Tg also varies accordingly.

3. The method according to claim 1, wherein in step (1), Tg is obtained by testing the thermal decomposition trend of the synthesized shape memory polymer using a differential scanning calorimeter, and the particle size is measured using a particle size analyzer.

4. The method according to claim 1, wherein in step (2), when a hot pressing machine is used for compression, the compression pressure and time are 20 MPa and 30 min, respectively.

5. The method according to claim 1, wherein in step (3), the particle size of the shape memory polymer particles is one-third of the size of the crack model and the particle size is uniform.

6. The method according to claim 1, wherein The preparation process of the bentonite-based slurry is as follows: 4 parts of bentonite are slowly added into 100 parts of distilled water, stirred for 2 hours, and then allowed to stand for 24 hours to obtain the bentonite-based slurry.

7. The method according to claim 1, wherein The concentration of the drilling fluid base slurry containing shape memory polymer particles is 3%-25%.

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