Evaluation method for the sealing and pressure-bearing performance of temperature-sensitive adhesive plugging materials in deep fractured formations

Abstract

The present invention discloses a method for evaluating the pressure-bearing performance of temperature-sensitive adhesive plugging materials for deep fractured formations, which belongs to the field of leakage control technology and includes: using temperature-sensitive adhesive plugging materials to make cylindrical samples according to preset dimensions, the preset dimensions including the diameter and length of the sample; measuring the uniaxial compressive strength of the sample and the strain corresponding to the uniaxial compressive strength; evaluating the pressure-bearing performance of the temperature-sensitive adhesive plugging material based on the uniaxial compressive strength of the sample and the strain corresponding to the uniaxial compressive strength, the greater the quotient of the uniaxial compressive strength and the strain corresponding to the uniaxial compressive strength, the better the pressure-bearing performance of the plugging layer. The present invention provides a method for scientifically evaluating the pressure-bearing performance of temperature-sensitive adhesive plugging materials, which combines stress and strain to systematically quantify the mechanical properties and sealing properties of the material, can accurately reflect the pressure-bearing performance of the material under actual working conditions, and the evaluation results are highly accurate. At the same time, the evaluation parameters are mainly based on the results of the pressure test, and the operation is simple.

Description

Technical Field

[0001] The present invention belongs to the technical field of leakage control and also relates to new material detection and functional testing. Specifically, it is a method for evaluating the sealing and pressure-bearing performance of temperature-sensitive adhesive plugging materials in deep fractured formations. Background Art

[0002] A thermosensitive adhesive plugging material is a plugging material that does not solidify at room temperature. However, when it reaches a certain temperature, it can cross-link with an amine cross-linking agent to form a bulk solid. This facilitates its solidification into a plug at bottomhole temperatures, thereby blocking the leakage path and enhancing the retention capacity of the plugging material in the leakage path. Therefore, it is particularly suitable for the high-temperature and high-pressure environments of deep fractured formations. There are many existing thermosensitive adhesive plugging materials, such as a thermosensitive material disclosed by Wang Weiji et al. (Preparation and properties of thermosensitive poly (NIPAm-co-AA) / nano-SiO2 composite blocking agent for shale gas reservoir [J]. Acta Petrolei Sinica, 2015, 36 (3): 378-384.).

[0003] Temperature-sensitive adhesive plugging materials enhance the pressure-bearing performance of the plugging layer by improving the adhesion between particles and between particles and fracture surfaces. Currently, pressure-bearing plugging tests are generally used to screen temperature-sensitive adhesive plugging materials. However, these tests require the preparation of drilling fluids, fracture models, and the grading of the plugging materials. These procedures are cumbersome, time-consuming, and subject to significant experimental errors. Therefore, a rapid and effective method is urgently needed to evaluate the performance of temperature-sensitive adhesive plugging materials. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a method for evaluating the pressure-bearing performance of temperature-sensitive adhesive plugging materials in deep fractured formations. The present invention uses the uniaxial compressive strength of the plugging layer and the strain corresponding to the uniaxial compressive strength to evaluate the pressure-bearing performance of the plugging layer, which can significantly improve the accuracy of the evaluation.

[0005] In order to achieve the above object, the solution provided by the present invention is as follows:

[0006] A method for evaluating the sealing and pressure-bearing performance of a temperature-sensitive adhesive plugging material in a deep fractured formation comprises the following steps:

[0007] S1. Using a temperature-sensitive adhesive sealing material, a cylindrical specimen is prepared according to preset dimensions, where the preset dimensions include the diameter and length of the specimen.

[0008] S2. Determine the uniaxial compressive strength of the sample and the strain corresponding to the uniaxial compressive strength;

[0009] S3. Evaluate the pressure-bearing performance of the temperature-sensitive adhesive plugging material based on the uniaxial compressive strength of the sample and the strain corresponding to the uniaxial compressive strength. The greater the quotient of the uniaxial compressive strength and the strain corresponding to the uniaxial compressive strength, the better the pressure-bearing performance of the plugging layer.

[0010] In the present invention, the uniaxial compressive strength of the sample is related to its size. When the aspect ratio is very small, the uniaxial compressive strength of the sample is very large. When the aspect ratio is very large, the sample is easily damaged due to elastic instability and uneven stress distribution, which reduces the uniaxial compressive strength of the sample. As a specific embodiment of the present invention, the aspect ratio of the sample is 2 to 3.

[0011] In the present invention, the uniaxial compressive strength can be measured using a measuring device in the prior art, and then a stress-strain curve is plotted. The peak intensity of the curve is the uniaxial compressive strength of the sample.

[0012] As a specific embodiment of the present invention, in step S1, the preset size is a diameter of 50 mm and an aspect ratio of 2; in step S3, the pressure bearing performance of the temperature-sensitive adhesive plugging material is evaluated using an adhesive performance evaluation index, wherein the calculation formula of the adhesive performance evaluation index is as follows:

[0013]

[0014] Where, B is the bonding performance evaluation index, ranging from 0 to 1, the larger the value, the better the performance; б max is the uniaxial compressive strength, i.e., peak strength, MPa; ε is the strain, i.e. the strain corresponding to the peak intensity;

[0015] Furthermore, step S3 also includes determining the pressure-bearing performance grade of the temperature-sensitive adhesive sealing material according to the bonding performance evaluation index and the assessment criteria, wherein the assessment criteria include: 0≤B≤0.2, weak pressure-bearing performance; 0.2<B≤0.4, relatively weak pressure-bearing performance; 0.4<B≤0.6, medium pressure-bearing performance; 0.6<B≤0.8, medium to strong pressure-bearing performance; 0.8<B≤1, strong pressure-bearing performance.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention provides a method for scientifically evaluating the pressure-bearing performance of temperature-sensitive adhesive sealing materials. It combines stress and strain to systematically quantify the mechanical properties and sealing performance of the material, and can accurately reflect the pressure-bearing performance of the material under actual working conditions. The evaluation results are highly accurate. At the same time, the evaluation parameters are mainly based on the results of compression tests, and the operation is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the stress-strain curve of the temperature-sensitive adhesive sealing material with LCC200 as the core;

[0019] Figure 2 This is the stress-strain curve of the temperature-sensitive adhesive sealing material with walnut shell as the core;

[0020] Figure 3 This is the stress-strain curve of the temperature-sensitive adhesive sealing material with porous basalt as the core. DETAILED DESCRIPTION

[0021] The present invention will be further described in detail below with reference to the embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0022] In this example, a warm-press plug modular press was used to press the specimens, and a microcomputer-controlled electronic universal testing machine, model ETM305D, was used to measure the stress-strain data of the specimens. Those skilled in the art will appreciate that the apparatus capable of implementing the present invention is not limited to the aforementioned apparatus. Furthermore, the "cross-sectional area" in this example refers to the maximum cross-sectional area of ​​the cylinder formed using the modular press.

[0023] In the following examples, LCC200 particles are from Chengdu Dedao Industrial Co., Ltd., which is a high-strength inert granular material that does not react with acid and has a mass crushing rate of 4.1% under a pressure of 30.0 MPa; E-12 and E-20 are both thermosetting epoxy resins, of which E-12 is from Xuzhou Huisheng Electronic Materials Co., Ltd. and E-20 is from Sinopec Baling Petrochemical Co., Ltd.; GZD is from Sichuan Southwest Shida Jinniu Petroleum Technology Co., Ltd., which is an acid-soluble filler material with a mesh size of 18 to 24.

[0024] Example 1: S1. A cylindrical sample is prepared using a temperature-sensitive adhesive sealing material, comprising the following steps:

[0025] S11. Preparation of temperature-sensitive adhesive sealing material: LCC200 particles (6-10 mesh) are used as core material, and epoxy resin E-12 is used as thermosetting resin. After washing and drying the core material, the total mass is weighed. Based on the mass of the dried core material, 10 wt% of epoxy resin, 0.1 wt% of dicyandiamide (curing agent), 0.1 wt% of silane coupling agent (interface modifier) ​​and 0.2 wt% of dimethylimidazole (catalyst) are weighed and set aside. Epoxy resin and dichloromethane are mixed and stirred at a mass ratio of 1:3 until completely dissolved, and dicyandiamide is added and stirred continuously to form a homogeneous solution, which is called epoxy resin. The method comprises the following steps: dissolving dimethylimidazole in anhydrous ethanol to prepare a catalytic system, then adding a silane coupling agent (γ-aminopropyltriethoxysilane) and an epoxy resin solution and stirring for 5 minutes to form a mixed liquid; transferring the mixed liquid and the core material particles into the coating machine trough, and adding dichloromethane until the particle layer is completely immersed; starting the coating machine that has been preheated to 50°C and maintaining a uniform rotation speed, and accelerating the evaporation of the solvent through the hot air circulation system; stopping the machine after a uniform coating layer is formed, and transferring the coated particles to a cooling plate to naturally cool to room temperature; finally, gently rubbing the agglomerated particles to obtain a temperature-sensitive adhesive sealing material with uniform particle size.

[0026] S12. Prepare plugging slurry: Based on the total mass of water, weigh 0.1wt% of sodium hydroxide, 0.2wt% of sodium carbonate, 6wt% of bentonite, 0.4wt% of sodium carboxymethyl cellulose (CMC) and 0.4wt% of xanthan gum for later use; dissolve sodium hydroxide and sodium carbonate in water, stir well and slowly add CMC and xanthan gum, then add bentonite to the solution, mix thoroughly until uniform and viscous, let it stand for 10 minutes before use.

[0027] S13. Mix the temperature-sensitive adhesive sealing material prepared in S11 with the plugging slurry configured in S12 in a mass ratio of 1:4, inject the mixture into a warm-press plug module press, and cure it at a temperature of 90°C and a pressure of 1 MPa for 6 hours to obtain a sample.

[0028] The sample was removed from the instrument, cooled to room temperature and its dimensions were measured. The specific dimensions are shown in Table 1.

[0029] S2. Determine the uniaxial compressive strength of the sample and the strain corresponding to the uniaxial compressive strength. This step uses an electronic universal testing machine to perform uniaxial mechanical properties testing on the cured sample. The specific steps are as follows:

[0030] S21. Place the sample in the testing machine fixture, ensuring that the loading direction of the sample is consistent with the pressure axis of the equipment;

[0031] S22, using uniform acceleration loading method, loading rate of 0.5mm / min, gradually apply external pressure until the sample breaks, stop loading, record the column deformation and stress data, and draw the stress-strain curve according to the test data, such as Figure 1 As shown;

[0032] S23. The uniaxial compressive strength of the sample and its corresponding strain were obtained according to the stress-strain curve, see Table 1.

[0033] S3. Evaluate the bonding performance evaluation index of the sealing layer based on the uniaxial compressive strength of the sample and its corresponding strain;

[0034] .

[0035] Example 2: The steps of this example are the same as those of Example 1, except that the samples are different. The sample of this example uses walnut shell particles (6-8 mesh) as the core material and is prepared according to the steps of Example 1.

[0036] The dimensions of the sample in this embodiment are shown in Table 1, and its stress-strain curve is shown in Table 1. Figure 2 The evaluation indicators of uniaxial compressive strength, strain and bonding performance are shown in Table 2.

[0037] Example 3: The steps of this example are the same as those of Example 1, except that the samples are different. The sample of this example uses porous basalt (6-10 mesh) as the core material and epoxy resin E-20 as the thermosetting resin, and is prepared according to the steps of Example 1.

[0038] The dimensions of the sample in this embodiment are shown in Table 1, and its stress-strain curve is shown in Table 1. Figure 3 The evaluation indicators of uniaxial compressive strength, strain and bonding performance are shown in Table 2.

[0039] Table 1 Dimensions of each sample

[0040]

[0041] Table 2 Uniaxial test results and bonding performance evaluation index of each sample

[0042]

[0043] Finally, the bonding performance evaluation index of Example 1 is 0.933, and the pressure-bearing performance is strong; the bonding performance evaluation index of Example 2 is 0.460, and the pressure-bearing performance is medium; the bonding performance evaluation index of Example 2 is 0.889, and the pressure-bearing performance is strong. The three are ranked in descending order of performance as follows: Example 1, Example 3, and Example 2.

[0044] Test Example 1

[0045] In order to verify the accuracy of the bonding performance evaluation index in evaluating pressure bearing performance, a plugging material was prepared using the temperature-sensitive bonding plugging material in the above embodiment, and a pressure-bearing plugging experiment was conducted to measure the actual pressure bearing performance of each material. The specific steps include the following:

[0046] The temperature-sensitive adhesives prepared in Examples 1 to 3 were used as bridging materials and GZD was used as filling materials to prepare plugging formulas. The amount of each substance added in the plugging formula was based on the mass of water in the plugging slurry base. The specific formula is shown in Table 3.

[0047] The formula of plugging slurry base is: water + 4wt% bentonite + 0.2wt% sodium carbonate + 0.1wt% sodium hydroxide + 0.3wt% sodium carboxymethyl cellulose + 0.4wt% xanthan gum. The above addition amount is based on the mass of water.

[0048] Table 3 Composition of each plugging formula

[0049]

[0050] (2) The positive bearing capacity test of the crack sealing layer includes the following steps: placing a variable width crack rock sample with an initial crack width of 5.0~3.0mm (the initial crack inlet width is 5.0mm, and the initial crack outlet width is 3.0mm) into a core holder with a heater, applying a confining pressure of 25MPa, closing the valve downstream of the core holder, pouring the prepared plugging slurry into the kettle upstream of the core holder, turning on the electric mixer in the kettle, and setting the speed to 150r / min; turning on the water pump connected to the kettle, The pressure in the kettle was increased to 1.0 MPa at a rate of 1 mL / min. After stabilizing the pressure for 5 minutes, the heater was turned on and the temperature was set to 90°C. 30 minutes after reaching the set temperature, the valve downstream of the core holder was opened and the initial leakage rate was recorded. The pressure in the kettle was continuously increased at a rate of 1 mL / min. When the pressure in the kettle dropped sharply and did not recover, the fracture sealing layer was considered to be damaged and the experiment was stopped. The peak pressure was recorded as the pressure bearing capacity of the fracture sealing layer, and the final leakage at the peak pressure was recorded as the cumulative leakage. The results of the positive pressure bearing capacity test of the fracture sealing layer for each plugging formulation are shown in Table 4.

[0051] Table 4 Test results of positive pressure bearing capacity of crack sealing layer of various plugging formulas

[0052]

[0053] It can be seen from Table 4 that the pressure-bearing and sealing performance of Formula 1 (using the temperature-sensitive adhesive sealing material of Example 1) is better than that of Formula 3 (using the temperature-sensitive adhesive sealing material of Example 3), and the pressure-bearing and sealing performance of Formula 3 is better than that of Formula 2 (using the temperature-sensitive adhesive sealing material of Example 2). The evaluation results are the same as the evaluation results directly using the bonding performance evaluation index. The relative size of the pressure-bearing and sealing performance of the formula can be determined by the relative size of the bonding performance evaluation index, thereby replacing the pressure-bearing and sealing performance test with the uniaxial compressive performance test.

[0054] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed in the embodiments of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for evaluating the sealing pressure bearing performance of temperature-sensitive adhesive plugging materials in deep fractured formations, characterized in that: include: S1. Using a temperature-sensitive adhesive sealing material, a cylindrical specimen is prepared according to a preset size, wherein the preset size is a diameter of 50 mm and an aspect ratio of 2; S2. measuring the uniaxial compressive strength of the sample and the strain corresponding to the uniaxial compressive strength; S3. Using an adhesive performance evaluation index to evaluate the sealing pressure-bearing performance of the temperature-sensitive adhesive plugging material. The greater the adhesive performance evaluation index, the better the pressure-bearing performance of the plugging layer. The calculation formula of the bonding performance evaluation index is as follows: Where, B is the bonding performance evaluation index; max is the uniaxial compressive strength; ε is the strain.

2. The method for evaluating the sealing pressure bearing performance of a temperature-sensitive adhesive plugging material for deep fractured formations according to claim 1, characterized in that: Step S3 also includes determining the pressure-bearing performance grade of the temperature-sensitive adhesive sealing material based on the bonding performance evaluation index and assessment criteria, wherein the assessment criteria include: 0≤B≤0.2, weak pressure-bearing performance; 0.2<B≤0.4, relatively weak pressure-bearing performance; 0.4<B≤0.6, medium pressure-bearing performance; 0.6<B≤0.8, medium to strong pressure-bearing performance; 0.8<B≤1, strong pressure-bearing performance.

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