Volume fracturing sand-carrying fluid evaluation method and equipment based on friction coefficient

Abstract

The invention relates to the technical field of petroleum and natural gas exploitation, in particular to a volume fracturing sand-carrying fluid evaluation method and equipment based on friction coefficient, and the method comprises the following steps: manufacturing a plurality of standard samples for testing by adopting a dry standard cylindrical core; testing the standard sample through a friction experiment instrument to obtain a friction coefficient of a control group; quartz sand with different mesh numbers is selected as a proppant, and is matched with different types of fracturing fluids to prepare a plurality of sand-carrying fluids; filling a group of standard samples with various sand-carrying fluids to obtain test samples, and testing the test samples through a friction experiment instrument to obtain friction coefficients of the test samples; calculating the friction coefficient reduction amplitude of each group of standard samples based on the friction coefficient of the control group and the friction coefficient of the test sample; and comparing the normalized friction coefficient reduction amplitude with a sand-carrying fluid evaluation grade to obtain an evaluation grade corresponding to the sand-carrying fluid. According to the method, the performance of the sand-carrying fluid is rapidly and accurately evaluated, the evaluation process is simplified, and the evaluation efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of oil and natural gas exploitation, and in particular to a friction coefficient-based volume fracturing sand-carrying fluid evaluation method and equipment. Background Art

[0002] In the field of oil and gas exploration and development, the development of low-permeability and ultra-low-permeability reservoirs has always been the focus of technical challenges. Due to the low permeability and limited natural production capacity of such reservoirs, it is difficult to meet the needs of efficient exploitation. Therefore, improving the permeability of the reservoir and increasing oil and gas production have become the key. Hydraulic fracturing technology, as an effective means of reservoir transformation, is widely used in the development of such reservoirs. Hydraulic fracturing technology injects fracturing fluid into the formation through high-pressure pumping to form a fracture network, thereby increasing the flow channel of oil and gas and improving the permeability of the reservoir. In the fracturing process, the sand-carrying fluid, as a key material, is composed of fracturing fluid and proppant, and its performance directly affects the opening, expansion and support effect of the fracture. The ideal sand-carrying fluid should have good sand-carrying capacity, low friction characteristics, and good fracture filling and support performance to ensure the formation and long-term stability of the fracture network.

[0003] However, the traditional sand-carrying fluid optimization method often relies on complex laboratory tests and field tests, which is not only time-consuming and labor-intensive, but also costly. In addition, factors such as the rock mechanical properties, ground stress state, and natural fracture development of different reservoirs will have a significant impact on the fracturing effect, making the optimization of sand-carrying fluid more complicated. Summary of the invention

[0004] The purpose of the present invention is to provide a method and device for evaluating volume fracturing sand-carrying fluid based on friction coefficient in order to solve at least one of the above technical problems.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0006] A method for evaluating volume fracturing sand-carrying fluid based on friction coefficient comprises the following steps:

[0007] A plurality of standard specimens for testing are prepared using dry standard cylindrical cores;

[0008] The friction coefficient of the control group is obtained by testing the standard sample using a friction tester;

[0009] Select quartz sand with different mesh sizes as proppant, and mix with different types of fracturing fluids to obtain a variety of sand-carrying fluids;

[0010] Filling a group of standard samples with various sand-carrying fluids to obtain test samples, and testing the test samples using the friction tester to obtain the friction coefficient of the test samples;

[0011] Calculating the reduction of the friction coefficient of each group of standard samples based on the friction coefficient of the control group and the friction coefficient of the test sample;

[0012] The reduction range of the normalized friction coefficient after normalization is compared with the evaluation grade of the sand-carrying fluid to obtain the evaluation grade corresponding to the sand-carrying fluid.

[0013] Furthermore, the process of making the standard sample is: cutting the dry standard cylindrical core into small cylinders with a thickness of two centimeters, and grinding the sample surface flat with 80-mesh sandpaper.

[0014] Furthermore, the cylindrical core adopts a reservoir core.

[0015] Furthermore, the standard for testing the friction coefficient of the friction tester is: applying a normal stress of 600N to the sample through the loading motor on the testing machine, applying a horizontal shear stress by controlling the displacement sensor, and the shear speed is 0.001mm / s.

[0016] Furthermore, the calculation formula for the reduction of the friction coefficient is as follows:

[0017] Δμ=μ0-μ1

[0018] Where Δμ is the reduction of friction coefficient, μ0 is the friction coefficient of the control group, and μ1 is the friction coefficient of the test sample.

[0019] Furthermore, the normalized processing formula for the reduction of the friction coefficient is as follows:

[0020]

[0021] Where μd is the reduction of normalized friction coefficient, Δμ is the reduction of friction coefficient, and μ0 is the friction coefficient of the control group.

[0022] Furthermore, the sand-carrying fluid evaluation level specifically includes:

[0023] Level 1: The reduction of normalized friction coefficient is > 0.3, indicating that the sand-carrying fluid has excellent effect;

[0024] Level 2: 0.1≤normalized friction coefficient reduction≤0.3; indicating that the sand-carrying fluid has a better effect;

[0025] Level 3: The reduction in normalized friction coefficient is less than 0.1, indicating that the sand-carrying fluid has a poor effect.

[0026] Furthermore, the greater the decrease in the normalized friction coefficient indicates that natural fractures and large-scale artificial fractures are more easily activated.

[0027] An electronic device comprises a processor, a memory and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, any of the friction coefficient-based volume fracturing sand-carrying fluid evaluation methods as described above is implemented.

[0028] A computer-readable storage medium storing a computer program, wherein the computer-readable storage medium implements any of the friction coefficient-based volume fracturing sand-carrying fluid evaluation methods described above when the computer program is executed by a processor.

[0029] The beneficial effects of the present invention are:

[0030] The present invention provides a fast and simple method for optimizing volume fracturing sand-carrying fluid based on friction coefficient. The method can accurately evaluate the ability of different sand-carrying fluids to activate natural fractures and artificial fractures during fracturing by measuring and calculating the reduction of the friction coefficient of rock samples by the sand-carrying fluid and its normalized value. The present invention not only simplifies the performance evaluation process of the sand-carrying fluid, but also improves the accuracy and reliability of the evaluation results, provides a scientific basis for the optimization of hydraulic fracturing technology in the development of unconventional oil and gas resources, and significantly improves the reservoir transformation effect and oil and gas production. The present invention is suitable for volume fracturing operations in reservoirs of different lithologies, including unconventional resource fields such as shale gas, coalbed methane, tight oil and gas, and hot dry rock. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a flow chart of a method for evaluating a volume fracturing sand-carrying fluid based on a friction coefficient according to an embodiment of the present invention;

[0032] Figure 2 It is a schematic diagram of determining the friction coefficient according to one embodiment of the present invention. DETAILED DESCRIPTION

[0033] The content of the present invention will now be discussed with reference to exemplary embodiments. It should be understood that the embodiments discussed are only to enable those skilled in the art to better understand and thus implement the content of the present invention, rather than implying any limitation on the scope of the present invention.

[0034] As used herein, the term “including” and variations thereof are to be interpreted as open-ended terms meaning “including, but not limited to.” The term “based on” is to be interpreted as “based, at least in part, on.” The terms “one embodiment” and “an embodiment” are to be interpreted as “at least one embodiment.”

[0035] Embodiment 1

[0036] Figure 1 The following is a flow chart of a method for evaluating a volume fracturing sand-carrying fluid based on a friction coefficient according to an embodiment of the present invention. Figure 1As shown, according to one embodiment of the present invention, a method for evaluating volume fracturing sand-carrying fluid based on friction coefficient comprises the following steps:

[0037] Step S102: using dry standard cylindrical cores to make a plurality of standard samples for testing;

[0038] Step S104: testing the standard sample by a friction tester to obtain the friction coefficient of the control group;

[0039] Step S106: selecting quartz sands of different mesh sizes as proppants, and mixing with different types of fracturing fluids to obtain a variety of sand-carrying fluids;

[0040] Step S108: Filling a group of standard samples with various sand-carrying fluids to obtain test samples, and testing the test samples using a friction tester to obtain the friction coefficient of the test samples;

[0041] Step S110: calculating the reduction range of the friction coefficient of each group of standard samples based on the friction coefficient of the control group and the friction coefficient of the test sample;

[0042] Step S112: Compare the reduction amplitude of the friction coefficient after normalization with the evaluation grade of the sand-carrying fluid to obtain the evaluation grade corresponding to the sand-carrying fluid.

[0043] In this embodiment, firstly, a dry standard cylindrical core sample is made by step S102, and these samples are used as the basis for testing to ensure the consistency and repeatability of the experiment. Subsequently, in step S104, the standard sample not filled with sand-carrying fluid is tested by a friction tester to obtain the friction coefficient of the control group, and this value is used as the basis for subsequent comparison. Then, in step S106, according to actual needs, quartz sand of different meshes is selected as a proppant, and configured with a variety of fracturing fluids to form a diversified sand-carrying fluid combination. In step S108, these sand-carrying fluids are filled into a group of standard samples to form test samples, and the friction tester is used again to test and obtain the friction coefficient of the test sample. Through step S110, the reduction range of the friction coefficient between the test sample and the control group is calculated. This indicator directly reflects the effect of the sand-carrying fluid in reducing friction. Finally, in step S112, the reduction range of the friction coefficient is normalized and compared with the preset sand-carrying fluid evaluation level, so as to quickly and accurately obtain the performance evaluation level of each sand-carrying fluid.

[0044] The friction coefficient-based volume fracturing sand-carrying fluid evaluation method of the present invention realizes a rapid and accurate evaluation of the sand-carrying fluid performance through the preparation of standardized samples, the precise measurement of the friction coefficient and the scientific comparison of evaluation levels; the method not only simplifies the evaluation process and improves the evaluation efficiency, but also ensures the objectivity and accuracy of the evaluation results through quantitative analysis, which is of great significance for optimizing the sand-carrying fluid formula, improving the efficiency of volume fracturing operations and reducing costs.

[0045] According to an embodiment of the present invention, the process of making the standard sample in step S102 is: cutting the dry standard cylindrical core into small cylinders with a thickness of two centimeters, and grinding the surface of the sample flat with 80-mesh sandpaper.

[0046] Preferably, the core column adopts a reservoir core.

[0047] In this embodiment, the production process of the standard sample is carefully designed to ensure the accuracy and repeatability of the experimental results. First, a dry standard cylindrical core is selected as the starting material, especially a reservoir core, because it is closer to the rock environment in the actual fracturing operation and can more truly reflect the effect of the sand-carrying fluid in actual application. Then, a professional cutting tool is used to cut the core into a small cylinder with a thickness of two centimeters. This size selection is intended to balance the operability of the experiment and the representativeness of the results. Subsequently, the sample surface is carefully polished with 80-mesh sandpaper to remove surface unevenness and tiny protrusions, ensure the smoothness of the sample surface, and thus reduce the measurement error caused by surface roughness. This processing process not only improves the quality of the sample, but also lays a solid foundation for the subsequent friction coefficient test. Through such a standardized production process, we can obtain standard samples with consistency and reliability, which provides a strong guarantee for accurately evaluating the lubrication performance of the sand-carrying fluid.

[0048] The standardized sample preparation process adopted by the present invention ensures the high quality and consistency of the sample through fine cutting and grinding processes; this preparation method not only improves the accuracy and reliability of the experimental data, but also provides a solid foundation for the subsequent accurate measurement of the friction coefficient and the scientific evaluation of the sand-carrying fluid performance; the reservoir core is selected as the sample material, which further enhances the practicality and application value of the experimental results. The present invention significantly improves the efficiency and accuracy of sand-carrying fluid evaluation work, and provides strong support for technological progress in the field of oil exploration and development.

[0049] According to one embodiment of the present invention, in step S104 and step S108, the standard for testing the friction coefficient of the friction tester is: applying a normal stress of 600N to the sample through the loading motor on the testing machine, applying horizontal shear stress by controlling the displacement sensor, and the shear rate is 0.001mm / s.

[0050] In this embodiment, in step S104 and step S108, the friction coefficient test process of the friction tester is precisely set to ensure the accuracy and repeatability of the experimental results. Specifically, first, the loading motor on the test machine applies a normal stress of 600N to the sample. The selection of this stress value is based on the simulation of the pressure that the rock material may withstand in the actual fracturing operation, aiming to make the experimental conditions closer to the actual situation. Subsequently, the horizontal shear stress is accurately applied by controlling the displacement sensor, and the shear rate is set to 0.001mm / s. This slow and stable shear rate helps to capture subtle changes in the friction process, thereby more accurately measuring the friction coefficient. During the entire test process, the friction tester will record the friction behavior of the sample under the action of normal stress and horizontal shear stress in real time, and obtain the friction coefficient of the sample by calculation. This test standard not only ensures the stability and controllability of the experimental conditions, but also improves the accuracy and reliability of the measurement results, providing a solid foundation for the subsequent evaluation of the performance of the sand-carrying fluid.

[0051] During the tangential loading process, due to the uneven surface profile, there will be a certain residual shear strength at the interface. According to Coulomb's law, the tangential stress can be expressed as:

[0052] τ=C+μσ (1)

[0053] Among them, τ is the tangential stress; C is the residual shear strength; μ is the interface friction coefficient; σ is the normal stress.

[0054] Divide both sides of the above equation by σ, and the apparent friction coefficient μ output by the experiment is a It can be expressed as:

[0055]

[0056] Figure 2 FIG. 1 is a schematic diagram for determining the friction coefficient according to an embodiment of the present invention; Figure 2 As shown in the figure, the highest value of the hard and brittle joint surface curve is the apparent friction coefficient, and the average value of the curve that tends to stabilize after the apparent friction coefficient is the final friction coefficient. The same is true for the soft plastic joint surface. The friction tester tests the standard sample and the test sample to obtain the friction coefficient of the control group and the friction coefficient of the test sample.

[0057] In this embodiment, the friction coefficient testing process of the friction tester is carefully designed and controlled to ensure the accuracy and reliability of the experimental data. A constant 600N normal stress is applied to the sample by a loading motor, simulating the pressure environment that the rock may be subjected to in actual fracturing operations. Subsequently, a displacement sensor is used to accurately control the application of horizontal shear stress, and shearing is performed at an extremely low shear rate (0.001mm / s) to capture subtle changes in the friction process. This test method has a unified test standard and accurate measurement results. By comparing the friction coefficients of the standard sample (control group) and the test sample (after filling with sand-carrying fluid), the influence of the sand-carrying fluid on the friction coefficient can be quantitatively evaluated.

[0058] The present invention realizes accurate measurement of the friction behavior of rock materials in fracturing operations by precisely controlling experimental conditions and introducing scientific calculation models. This test method not only improves the accuracy and reliability of measurement results, but also provides strong support for the scientific evaluation of sand-carrying fluid performance. By comparing the changes in the friction coefficient of samples after being treated with different sand-carrying fluids, the effect of the sand-carrying fluid can be intuitively judged, which provides an important basis for optimizing the sand-carrying fluid formula and improving the efficiency of fracturing operations. At the same time, the test method also has the advantages of simple operation, stable results, strong repeatability, etc., and is suitable for large-scale experimental research and industrial applications.

[0059] According to one embodiment of the present invention, the calculation formula for the reduction of the friction coefficient is as follows:

[0060] Δμ=μ0-μ1 (3)

[0061] Where Δμ is the reduction of friction coefficient, μ0 is the friction coefficient of the control group, and μ1 is the friction coefficient of the test sample.

[0062] The normalized formula for the reduction of the friction coefficient is as follows:

[0063]

[0064] In the formula, μ d is the normalized reduction in friction coefficient, Δμ is the reduction in friction coefficient, and μ0 is the friction coefficient of the control group.

[0065] The greater the decrease in the normalized friction coefficient, the easier it is for natural fractures and large-scale artificial fractures to be activated.

[0066] Table 1 Optimum selection of sand-carrying fluid

[0067] μd Effect <0.1 Difference 0.1～0.3 better >0.3 Excellent

[0068] Table 1 is a preferred table of sand-carrying fluid. As shown in Table 1, preferably, the evaluation level of the sand-carrying fluid specifically includes:

[0069] Level 1: The reduction of normalized friction coefficient is > 0.3, indicating that the sand-carrying fluid has excellent effect;

[0070] Level 2: 0.1≤normalized friction coefficient reduction≤0.3; indicating that the sand-carrying fluid has a better effect;

[0071] Level 3: The reduction in normalized friction coefficient is <0.1, indicating that the sand-carrying fluid has a poor effect.

[0072] In this embodiment, the friction coefficients of the control group (i.e., the sample without sand-carrying fluid) and the test sample (the sample with sand-carrying fluid) were measured through precise friction experiments, and the reduction amplitude of the friction coefficient Δμ was calculated accordingly; this step aims to quantify the improvement effect of the sand-carrying fluid on the friction behavior of the rock material surface. Subsequently, in order to more intuitively compare the performance of different sand-carrying fluids, the reduction amplitude of the friction coefficient was normalized to obtain μ d , thus eliminating the influence of the difference in friction coefficient of the control group on the evaluation results; the reduction of friction coefficient after normalization can directly reflect the ability of sand-carrying fluid to reduce friction and activate natural fractures and large-scale artificial fractures. In Table 1, three evaluation levels of sand-carrying fluid effect are set according to different ranges of normalized friction coefficient reduction, providing a clear standard for the optimization of sand-carrying fluid.

[0073] The present invention provides a scientific and accurate method for evaluating the performance of sand-carrying fluid by quantitatively calculating the reduction of friction coefficient and performing normalization processing; the method not only simplifies the process of sand-carrying fluid optimization, but also improves the objectivity and reliability of the evaluation results; the reduction of friction coefficient after normalization processing directly reflects the ability of sand-carrying fluid in reducing rock surface friction and activating cracks, and provides strong technical support for the selection of sand-carrying fluid in oil and gas field fracturing operations. By applying the method of the present invention, sand-carrying fluid with excellent effect can be selected, effectively improving the efficiency and economy of fracturing operations.

[0074] Embodiment 2

[0075] According to one embodiment of the present invention, a method for evaluating volume fracturing sand-carrying fluid based on friction coefficient comprises the following steps:

[0076] Step 1: Cut the dry standard cylindrical core into small cylinders with a thickness of two centimeters. The core column can be a reservoir core. Grind the surface of the sample with 80-grit sandpaper and put it into the friction tester;

[0077] Step 2: Apply a normal stress of 600N to the sample through the loading motor on the testing machine, and apply horizontal shear stress by controlling the displacement sensor. The shear rate is 0.001mm / s. Under this condition, the friction coefficient of the sample is tested, and the friction coefficient μ0 at this time is used as the control group.

[0078] During the tangential loading process, due to the uneven surface profile, there will be a certain residual shear strength at the interface. According to Cou1omb's law, the tangential stress can be expressed as:

[0079] τ=C+μσ (1)

[0080] Among them, τ is the tangential stress; C is the residual shear strength; μ is the interface friction coefficient; σ is the normal stress.

[0081] Divide both sides of the above equation by σ, and the apparent friction coefficient μ output by the experiment is a It can be expressed as:

[0082]

[0083] Step 3: Select quartz sand of different mesh sizes as proppant, and mix with different types of fracturing fluids to prepare a variety of sand-carrying fluids.

[0084] Step 4: Prepare multiple groups of small core columns from step 1, and repeat the operation of step 2 to serve as the control group for each group of sand-carrying fluid.

[0085] Step 5: After each group completes the control group test, fill the sand-carrying liquid in step 3 between the samples, and then repeat the operation of step 2 to obtain the friction coefficient μ1 of multiple groups of samples under different sand-carrying liquids.

[0086] Step 6: After adding the sand-carrying fluid, the friction coefficient of the sample will be greatly reduced. The greater the reduction in the friction coefficient, the easier it is for natural fractures and large-scale artificial fractures to be activated. The calculation formula for the reduction in the friction coefficient is as follows:

[0087] Δμ=μ0-μ1 (3)

[0088] Where Δμ is the reduction of the friction coefficient, μ0 is the friction coefficient of the control group, and μ1 is the friction coefficient obtained in step 5.

[0089] Step 7: Normalize the friction coefficient reduction Δμ in step 6, and the formula is as follows:

[0090]

[0091] In the formula, μ d is the normalized reduction in friction coefficient, Δμ is the reduction in friction coefficient, and μ0 is the friction coefficient of the control group.

[0092] Step 8: After adding the sand-carrying fluid, the friction coefficient of the sample will be greatly reduced. The greater the reduction in the friction coefficient, the easier it is for natural cracks and large-scale artificial cracks to be activated. Therefore, the sand-carrying fluid sample with the largest reduction in friction coefficient has the best crack-making effect, and the sand-carrying fluid is optimized.

[0093] Step 9: Create a sand-carrying fluid optimization table.

[0094] Table 1 Optimum selection of sand-carrying fluid

[0095] μd Effect <0.1 Difference 0.1～0.3 better >0.3 Excellent

[0096] Unconventional reservoirs include shale gas, coalbed methane or tight oil and gas reservoirs or hot dry rock resources in unconventional oil and gas reservoirs, as well as low permeability or ultra-low permeability reservoirs.

[0097] The present invention is a method for optimizing volume fracturing sand-carrying fluid based on friction coefficient, so the optimization is performed according to the activation ability of different sand-carrying fluids on fractures. It is applicable to unconventional oil and gas resources such as shale gas, coalbed methane, tight oil and gas, hot dry rock, and low permeability and ultra-low permeability reservoirs.

[0098] Embodiment 3

[0099] According to one embodiment of the present invention, an electronic device includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, any method for evaluating volumetric fracturing sand-carrying fluid based on friction coefficient in the present invention is implemented.

[0100] According to one embodiment of the present invention, a computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, any method for evaluating a volumetric fracturing sand-carrying fluid based on a friction coefficient in the present invention is implemented.

[0101] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described devices and media can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0102] The present invention realizes rapid and accurate evaluation of sand-carrying fluid performance through the preparation of standardized samples, precise measurement of friction coefficient and scientific comparison of evaluation levels; it not only simplifies the evaluation process and improves the evaluation efficiency, but also ensures the objectivity and accuracy of the evaluation results through quantitative analysis, which is of great significance for optimizing the sand-carrying fluid formula, improving the efficiency of volume fracturing operations and reducing costs.

[0103] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in the present application.

[0104] It should be understood that the size of the serial numbers of each step in the content of the invention and the embodiments of the present invention does not absolutely mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

Claims

1. A method for evaluating volume fracturing sand-carrying fluid based on friction coefficient, characterized in that: The following steps are involved: A plurality of standard specimens for testing are prepared using dry standard cylindrical cores; The friction coefficient of the control group is obtained by testing the standard sample using a friction tester; Select quartz sand with different mesh sizes as proppant, and mix with different types of fracturing fluids to obtain a variety of sand-carrying fluids; Filling a group of standard samples with various sand-carrying fluids to obtain test samples, and testing the test samples using the friction tester to obtain the friction coefficient of the test samples; Calculating the reduction of the friction coefficient of each group of standard samples based on the friction coefficient of the control group and the friction coefficient of the test sample; The reduction range of the normalized friction coefficient after normalization is compared with the evaluation grade of the sand-carrying fluid to obtain the evaluation grade corresponding to the sand-carrying fluid.

2. The method for evaluating volume fracturing sand-carrying fluid based on friction coefficient according to claim 1, characterized in that: The process of making the standard sample is as follows: cut the dry standard cylindrical core into small cylinders with a thickness of two centimeters, and grind the surface of the sample flat with 80-mesh sandpaper.

3. The method for evaluating volume fracturing sand-carrying fluid based on friction coefficient according to claim 2, characterized in that: The cylindrical core adopts the reservoir core.

4. The method for evaluating volume fracturing sand-carrying fluid based on friction coefficient according to claim 1, characterized in that: The standard for testing the friction coefficient of the friction tester is: a normal stress of 600N is applied to the sample through the loading motor on the test machine, and a horizontal shear stress is applied by controlling the displacement sensor, and the shear rate is 0.001mm / s.

5. The method for evaluating volume fracturing sand-carrying fluid based on friction coefficient according to claim 1, characterized in that: The calculation formula for the reduction of the friction coefficient is as follows: Δμ=μ0-μ1 Where Δμ is the reduction of friction coefficient, μ0 is the friction coefficient of the control group, and μ1 is the friction coefficient of the test sample.

6. The method for evaluating volume fracturing sand-carrying fluid based on friction coefficient according to claim 1, characterized in that: The normalized formula for the reduction of the friction coefficient is as follows: Where μd is the reduction of normalized friction coefficient, Δμ is the reduction of friction coefficient, and μ0 is the friction coefficient of the control group.

7. The method for evaluating volume fracturing sand-carrying fluid based on friction coefficient according to claim 1, characterized in that: The sand-carrying fluid evaluation grades specifically include: Level 1: The reduction of normalized friction coefficient is > 0.3, indicating that the sand-carrying fluid has excellent effect; Level 2: 0.1≤normalized friction coefficient reduction≤0.3; indicating that the sand-carrying fluid has a better effect; Level 3: The reduction in normalized friction coefficient is <0.1, indicating that the sand-carrying fluid has a poor effect.

8. The method for evaluating volume fracturing sand-carrying fluid based on friction coefficient according to claim 1, characterized in that: The greater the decrease in the normalized friction coefficient, the easier it is for natural fractures and large-scale artificial fractures to be activated.

9. An electronic device, characterized in that: The invention comprises a processor, a memory and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, the friction coefficient-based volume fracturing sand-carrying fluid evaluation method according to any one of claims 1 to 8 is implemented.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the friction coefficient-based volume fracturing sand-carrying fluid evaluation method according to any one of claims 1 to 8 is implemented.

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