Method for analyzing rock breaking pressure of one-time fracturing tube

Abstract

The application provides a one-off fracturing tube rock breaking pressure analysis method, relates to the rock breaking technical field, and constructs a prediction model of a hole wall pressure value of the one-off fracturing tube, so that the corresponding relationship between the peak pressure value in the tube and the hole wall pressure value is represented, the hole wall pressure value in actual engineering application is conveniently predicted, and the actual engineering application has guiding significance.

Description

Technical Field

[0001] This application relates to the field of rock breaking technology, and more specifically, to a method for analyzing rock breaking pressure in a single-use fracturing tube. Background Technology

[0002] Carbon dioxide phase change rock breaking technology is an important non-traditional physical rock breaking technology, and an effective supplement to explosive blasting technology. Carbon dioxide phase change induced high-pressure gas rock breaking utilizes liquid carbon dioxide as a medium, encapsulated with an activator (also known as a heating agent) within a sealed fracturing tube. Electricity is applied to the activator to generate high temperatures, causing the liquid carbon dioxide to instantly vaporize and expand, producing high-pressure gas. This high-pressure gas acts on the surrounding rock mass, causing it to fracture and achieving the rock-breaking effect.

[0003] The structure and mechanism of action of fracturing tubes directly affect the explosive power and effect. Currently, the first-generation fracturing tubes are the most researched and used. These tubes release pressure at their ends, and the main body is recyclable and reusable. With technological advancements, second-generation fracturing tubes have emerged. These tubes achieve sidewall pressure relief through structural design changes and are designed for single use; hence, they are also called disposable fracturing tubes. Currently, research on second-generation fracturing tubes is limited. However, due to differences in structure and pressure release between the first and second generation tubes, research findings based on the first generation cannot be applied to the second generation, resulting in significant limitations in their practical engineering applications. Summary of the Invention

[0004] The purpose of this application is to address the shortcomings of the prior art by providing a method for analyzing rock-breaking pressure in a single-stage fracturing tube. By constructing a predictive model of the borehole wall pressure value of the single-stage fracturing tube, the method characterizes the correspondence between the peak pressure value inside the tube and the borehole wall pressure value, facilitating the prediction of borehole wall pressure values ​​in actual engineering projects and providing guidance for practical engineering applications.

[0005] To achieve the above objectives, the technical solutions adopted in the embodiments of this application are as follows:

[0006] One aspect of this application provides a method for analyzing rock-breaking pressure in a single fracturing tube, the method comprising:

[0007] The peak pressure inside the single-use fracturing tube and the borehole wall pressure of the single-use fracturing tube were obtained by rock-breaking test of the single-use fracturing tube.

[0008] Based on the peak pressure inside the tube and the pressure on the borehole wall, a prediction model for the borehole wall pressure is constructed using a pre-defined pressure amplification model based on the gas impact on the borehole wall generated by a one-time fracture tube phase change. The prediction model is used to characterize the correspondence between the peak pressure inside the tube and the pressure on the borehole wall.

[0009] Optionally, when there is a gap between the single-use fracturing tube and the borehole wall, a prediction model for the borehole wall pressure value is constructed based on the peak pressure value inside the tube and the borehole wall pressure value, using a preset pressure amplification model of the gas impacting the borehole wall caused by the phase change of the single-use fracturing tube. This model includes:

[0010] Based on the peak pressure value inside the pipe, the gas pressure value at the gas-rock interface is determined by the principle of isentropic expansion.

[0011] Based on the gas pressure value and the borehole wall pressure value, a prediction model for the borehole wall pressure value is constructed using a pre-defined pressure amplification model of the gas impacting the borehole wall generated by a single-stage fracturing tube phase change.

[0012] Optionally, the gas pressure at the gas-rock interface can be determined based on the peak pressure within the pipe using the principle of isentropic expansion, including:

[0013] The gas pressure at the gas-rock interface is determined based on the peak pressure inside the tube, the volume inside the single-use fracturing tube, and the effective volume of the borehole.

[0014] Optionally, the borehole is a cylindrical borehole, and the effective volume of the borehole is: V1=π(R1-t0) 2 l1, where V1 is the effective volume of the borehole, π is pi, R1 is the radius of the borehole, l1 is the length of the borehole, and t0 is the thickness of the single-shot fracture tube.

[0015] Optionally, the gas pressure value at the gas-rock interface can be determined based on the peak pressure value inside the tube, the volume inside the single-use fracturing tube, and the effective volume of the borehole, including:

[0016] p1 is the gas pressure at the gas-rock interface, p0 is the peak pressure inside the tube, l0 is the length of the single-stage fracturing tube, R0 is the inner radius of the single-stage fracturing tube, and γ is the isentropic exponent.

[0017] Optionally, the prediction model for the orifice wall pressure is as follows:

[0018] p2 is the pressure value at the borehole wall, and n is the preset pressure amplification model.

[0019] Optionally, the method also includes:

[0020] The preset pressure amplification model is determined based on the adiabatic index, initial density, and peak pressure of the gas explosion products in the primary fracturing tube, as well as the density, wave velocity, and gas pressure values ​​of the rock.

[0021] Optionally, the method also includes:

[0022] The actual test pressure amplification factor is determined based on the ratio of the borehole wall pressure value to the gas pressure value obtained from the rock-breaking test of the single-use fracturing tube.

[0023] The theoretical pressure amplification factor matching the rock-breaking test of the one-time fracturing tube is determined based on the preset pressure amplification model.

[0024] The correction factor is determined based on the actual test pressure amplification factor and the theoretical pressure amplification factor, and the preset pressure amplification model is corrected based on the correction factor.

[0025] Optionally, the peak pressure inside the disposable fracturing tube and the borehole wall pressure of the disposable fracturing tube can be obtained through rock-breaking tests, including:

[0026] Construct a physical model of the rock mass, which includes blast holes;

[0027] Multiple first pressure sensors are installed in the rock mass of the physical model, and the multiple first pressure sensors are distributed in a ring around the periphery of the borehole.

[0028] A disposable fracturing tube is inserted into the borehole, and there is a gap between the disposable fracturing tube and the inner wall of the borehole;

[0029] A second pressure sensor is installed at the end of the disposable fracturing tube;

[0030] The phase change rock breaking of the single-stage fracturing tube is controlled by obtaining the borehole wall pressure value through the first pressure sensor and the peak pressure inside the tube through the second pressure sensor.

[0031] Optionally, the method also includes:

[0032] Obtain the actual peak pressure value inside the pipe during a single rock-breaking operation;

[0033] The actual peak pressure value inside the pipe is input into the prediction model of the orifice wall pressure value to obtain the predicted orifice wall pressure value corresponding to the actual peak pressure value inside the pipe.

[0034] The beneficial effects of this application include:

[0035] This application provides a method for analyzing rock-breaking pressure in a single-stage fracturing tube. By constructing a predictive model of the borehole wall pressure value of the single-stage fracturing tube, it characterizes the correspondence between the peak pressure value inside the tube and the borehole wall pressure value, which facilitates the prediction of the borehole wall pressure value in practical engineering applications and has guiding significance for practical engineering applications. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the structure of a disposable fracturing tube provided in an embodiment of this application;

[0038] Figure 2 One of the flowcharts for the one-time rock-breaking pressure analysis method for fracturing tubes provided in the embodiments of this application;

[0039] Figure 3 The second flowchart of the one-time fracturing tube rock-breaking pressure analysis method provided in the embodiments of this application;

[0040] Figure 4 The third flowchart of the one-time fracturing tube rock-breaking pressure analysis method provided in the embodiments of this application;

[0041] Figure 5 This is one of the structural schematic diagrams of a one-time fracturing tube rock-breaking test provided in the embodiments of this application;

[0042] Figure 6 This is the second schematic diagram of the structure of the one-time fracturing tube rock-breaking test provided in the embodiments of this application;

[0043] Figure 7 A single-factor statistical relationship diagram of pipe pressure and filling pressure provided for embodiments of this application;

[0044] Figure 8 A single-factor statistical relationship diagram between pipe pressure and filling amount is provided for embodiments of this application;

[0045] Figure 9 Pressure-time curves inside the single-use rupture tubes corresponding to test numbers 1-4 provided in the embodiments of this application;

[0046] Figure 10 The borehole wall pressure-time curves corresponding to test numbers 1-4 provided in the embodiments of this application.

[0047] Icons: 10-Disposable fracturing tube; 11-Tube sidewall; 12-Activator; 13-Liquid carbon dioxide; 20-Physical model rock mass; 21-Breakhole; 22-Breakhole wall; 23-Gap; 30-First pressure sensor. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. It should be noted that, in the absence of conflict, the various features in the embodiments of this application can be combined with each other, and the combined embodiments are still within the protection scope of this application.

[0049] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0050] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0051] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0052] As the first-generation fracturing tube (also known as Cardox tube) is increasingly used in various engineering projects, its shortcomings have become apparent: although it is reusable, repeated use can easily lead to bending or even breakage; its weight makes transportation, installation, and retrieval costly and inefficient; and its end-release characteristic increases the risk of "flying tube" accidents, posing a safety hazard. To address these problems, such as… Figure 1 As shown, a second-generation fracturing tube has emerged, comprising a tube body and activator 12 and liquid carbon dioxide 13 filled within the tube body. The activator 12 and liquid carbon dioxide 13 are separated. Because the second-generation fracturing tube does not have the end pressure relief hole of the first-generation tube, and the thickness of the tube body sidewall 11 is thinner than that of the first-generation tube, the second-generation fracturing tube changes the way it releases pressure at the end, instead releasing pressure laterally. The pressure acts more evenly on the borehole wall 22 of the borehole 21 where the fracturing tube is located, effectively reducing accidents such as borehole punching and "flying tube" that occurred with the first-generation fracturing tube. Furthermore, the second-generation fracturing tube is for single use only and does not require recycling; therefore, it is also called a disposable fracturing tube 10. It also does not require mechanical installation into the borehole, making operation convenient and construction efficiency high.

[0053] Currently, research on liquid carbon dioxide 13-phase change fracturing technology is mostly focused on the early first-generation fracturing tubes, with less research on second-generation fracturing tubes. Therefore, this affects the application of second-generation fracturing tubes in practical engineering.

[0054] In view of this, one aspect of the embodiments of this application provides a method for analyzing the rock-breaking pressure of a single-use fracturing tube 10 (i.e., a second-generation fracturing tube). This method constructs a predictive model for the borehole wall pressure value of the single-use fracturing tube 10, thereby characterizing the correspondence between the peak pressure value inside the tube and the borehole wall pressure value. This facilitates the prediction of borehole wall pressure values ​​in practical engineering applications and has guiding significance for practical engineering applications, such as... Figure 2 As shown, the method includes:

[0055] S100: Obtain the peak pressure inside the disposable fracturing tube 10 and the borehole wall pressure of the borehole 21 where the disposable fracturing tube 10 is located through a rock-breaking test of the disposable fracturing tube 10.

[0056] To construct a predictive model for the borehole wall pressure value of the one-time fracturing tube 10, a rock-breaking test of the one-time fracturing tube 10 can be conducted, and the test data can be obtained. Considering the lateral pressure relief method of the one-time fracturing tube 10, its entire process is as follows: the activator 12 inside the fracturing tube is excited by the current to undergo a chemical reaction, which releases a large amount of heat, causing the surrounding liquid carbon dioxide 13 to change phase. The volume of carbon dioxide inside the fracturing tube expands rapidly, breaks through the side wall of the fracturing tube, and the pressure is released from the side of the fracturing tube, and then acts on the borehole wall 22 of the borehole 21. Therefore, when obtaining the rock-breaking test data, the peak pressure value inside the one-time fracturing tube 10 and the borehole wall pressure value of the borehole 21 where the one-time fracturing tube 10 is located can be obtained, which is convenient for constructing a predictive model for the borehole wall pressure value.

[0057] S200: Based on the peak pressure value inside the pipe and the pressure value on the borehole wall, and based on the preset pressure amplification model of the gas impacting the borehole wall 22 of the blast hole 21 generated by the phase change of the blasting pipe 10, a prediction model for the borehole wall pressure value is constructed. The prediction model is used to characterize the correspondence between the peak pressure value inside the pipe and the pressure value on the borehole wall.

[0058] Given that the shock wave generates transmitted and reflected waves in the second medium when it travels from the first medium, the high-pressure gas released from the side of the fracturing tube will act on the borehole wall 22 of the borehole 21, increasing the pressure. Therefore, after obtaining the test data (peak pressure inside the tube and borehole wall pressure) through S100, a predictive model for the borehole wall pressure can be constructed based on the test data (peak pressure inside the tube and borehole wall pressure) and a preset pressure amplification model. This predictive model characterizes the correspondence between the peak pressure inside the tube and the borehole wall pressure. Thus, in practical engineering applications, the actual peak pressure inside the tube can be input into the predictive model to obtain the corresponding predicted borehole wall pressure, thereby guiding the application of the disposable fracturing tube 10 in practical engineering.

[0059] It should be understood that in order to construct an accurate predictive model of the borehole wall pressure, multiple experiments can be conducted, thus obtaining multiple sets of experimental data, which can then be used to construct the predictive model.

[0060] Optionally, when the disposable fracturing tube 10 is installed in the borehole 21, the disposable fracturing tube 10 and the borehole wall 22 of the borehole 21 can be air-decoupled charges, that is, there is a gap 23 between the disposable fracturing tube 10 and the inner wall of the borehole 21. In this case, the carbon dioxide in the disposable fracturing tube expands rapidly to form a high-pressure gas. After breaking through the side wall of the disposable fracturing tube, it will first impact the air in the gap 23, and then impact the borehole wall 22 of the borehole 21. Therefore, when constructing the prediction model of the borehole wall pressure value through the aforementioned S200, as... Figure 3 As shown, it may include:

[0061] S210: Based on the peak pressure value inside the pipe, the gas pressure value at the gas-rock interface is determined by the principle of isentropic expansion.

[0062] Since the high-pressure gas undergoes isentropic expansion within the gap 23 after breaking through the sidewall of the fractured pipe, the peak pressure inside the pipe obtained from the experiment can be used as a basis to determine the peak pressure of the high-pressure gas at the interface between the gas and the inner wall of the borehole 21 before it enters the inner wall of the borehole 21, i.e., the gas pressure at the gas-rock interface. Therefore, when constructing a prediction model for the borehole wall pressure based on this model, it can better fit the actual engineering situation and improve the prediction accuracy of the borehole wall pressure prediction model.

[0063] S220: Based on the gas pressure value and the borehole wall pressure value, and using the preset pressure amplification model of the gas impacting the borehole wall 22 of the blast hole 21 generated by the phase change of the one-time fracturing tube 10, a prediction model for the borehole wall pressure value is constructed.

[0064] After obtaining the gas pressure value at the gas-rock interface via S210, a prediction model for the borehole wall pressure value can be constructed based on the gas pressure value at the gas-rock interface and the borehole wall pressure value, using a preset pressure amplification model. As mentioned earlier, this model can better reflect actual engineering conditions and improve the prediction accuracy of the borehole wall pressure value prediction model.

[0065] Optionally, when determining the gas pressure value at the gas-rock interface via S210, it can be done in the following way: based on the isentropic expansion process that occurs within the gap 23 after the high-pressure gas breaks through the sidewall of the fracturing tube, the gas pressure value at the gas-rock interface can be determined based on the peak pressure value inside the tube obtained from the experiment, the volume inside the single-use fracturing tube 10 in the experiment, and the effective volume of the borehole 21 of the test model. Specifically, the gas pressure value at the gas-rock interface can be determined according to the following equation:

[0066]

[0067] Where p1 is the gas pressure value at the gas-rock interface, V1 is the effective volume of borehole 21, p0 is the peak pressure value inside the tube, V0 is the volume inside the single-use fracturing tube 10, and γ is the isentropic exponent.

[0068] Optionally, borehole 21 is a cylindrical borehole; therefore, the effective volume of borehole 21 can be determined according to the following equation:

[0069] V1 = π(R1 - t0) 2 l1,

[0070] Where V1 is the effective volume of borehole 21, π is pi, R1 is the radius of borehole 21, l1 is the length of borehole 21, and t0 is the thickness of the one-time fracturing tube 10.

[0071] Therefore, when determining the effective volume of borehole 21, the thickness of the sidewall of the single-use fracturing tube 10 can be fully considered and removed to obtain the effective volume of borehole 21, which helps to improve the accuracy of the prediction model construction.

[0072] Optionally, the gas pressure value at the gas-rock interface can be determined specifically according to the following equation:

[0073]

[0074] Where p1 is the gas pressure value at the gas-rock interface, p0 is the peak pressure value inside the tube, l0 is the length of the one-time fracturing tube 10, R0 is the inner radius of the one-time fracturing tube 10, and γ is the isentropic exponent.

[0075] Optionally, based on the equation for determining the gas pressure value at the gas-rock interface, and combined with a pre-defined pressure amplification model, the prediction model for the borehole wall pressure value is as follows:

[0076]

[0077] Where p2 is the orifice wall pressure value, and n is the preset pressure amplification model.

[0078] Based on this prediction model, it can be applied to the actual rock-breaking project of the one-time fracturing tube 10. When the actual rock-breaking project is determined, the corresponding l0, l1, n, R0, R1, t0 and γ can be determined. Therefore, by obtaining the actual peak pressure value inside the one-time fracturing tube 10 for rock breaking, and then inputting the actual peak pressure value inside the tube into the prediction model of the borehole wall pressure value, the predicted borehole wall pressure value corresponding to the actual peak pressure value inside the tube can be obtained.

[0079] Optionally, a preset pressure amplification model can be preset, but it should be considered that the preset pressure amplification model should take into account factors such as the adiabatic index, initial density, and peak pressure inside the pipe of the gas explosion products, as well as the density, wave velocity, and gas pressure of the rock. Therefore, the preset pressure amplification model can be determined based on the adiabatic index, initial density, and peak pressure inside the pipe of the gas explosion products in the primary fracturing pipe, as well as the density, wave velocity, and gas pressure of the rock.

[0080] Specifically, the preset pressure amplification model can be determined according to the following equation:

[0081]

[0082] Wherein, s can be determined according to the following equation:

[0083]

[0084] in,

[0085] Wherein, I1 can be determined according to the following equation:

[0086]

[0087] in, k is the adiabatic index of the gas explosion product (high-pressure gas), which can be taken as k = 1.295 in the experiment. ρ is the density of the rock, and c is the wave velocity of the rock. The measured ρ of the physical model rock mass 20 in the experiment is 2380 kg / m³. 3 c = 4999 m / s, ρ0 is the initial density of the gas explosion products, which can be taken as ρ0 = 1100 kg / m³ in the experiment. 3 p0 is the initial pressure of the gas explosion products, i.e., the peak pressure value inside the pipe, and p1 is the gas pressure value at the gas-rock interface.

[0088]

[0089] in,

[0090]

[0091] Where T = 2B 2 +4A.

[0092] Optionally, based on the equation for determining the gas pressure value at the gas-rock interface and the equation for determining the preset pressure amplification model, the prediction model for the borehole wall pressure value is as follows:

[0093]

[0094] Therefore, the above prediction model fully considers factors such as the geometric parameters of the one-time fracture tube 10 and the borehole 21, and the rock wave impedance.

[0095] Optionally, to accurately predict the borehole wall pressure, the pre-set pressure amplification model can be modified using a rock-breaking test of the single-pass fracturing tube 10 during the determination process. Specifically, for example... Figure 4 As shown, the method also includes:

[0096] S300: Determine the actual test pressure amplification factor based on the ratio of the borehole wall pressure value to the gas pressure value obtained from the rock-breaking test of the one-time fracturing tube 10.

[0097] Test data can be obtained first through a rock-breaking test of the single-pass fracturing tube 10, such as the borehole wall pressure value and gas pressure value in the test. As mentioned earlier, the gas pressure value can be determined based on the peak pressure value inside the tube in the test. The actual test pressure amplification factor can be determined by calculating the ratio of the borehole wall pressure value and the gas pressure value.

[0098] S400: Determine the theoretical pressure amplification factor that matches the rock-breaking test of the one-time fracturing tube 10 based on the preset pressure amplification model.

[0099] Then, based on the preset pressure amplification model, the theoretical pressure amplification factor matching the rock-breaking test of the one-time fracturing tube 10 is directly calculated.

[0100] S500: Determine the correction factor based on the actual test pressure amplification factor and the theoretical pressure amplification factor, and correct the preset pressure amplification model based on the correction factor.

[0101] Then, by comparing the actual experimental pressure amplification factor with the theoretical pressure amplification factor, the difference between the two is determined, and a correction factor is determined based on this difference. The preset pressure amplification model is then corrected based on this correction factor. Of course, a threshold can be set. For example, if the difference between the actual experimental pressure amplification factor and the theoretical pressure amplification factor is less than the threshold, the preset pressure amplification model may not need to be corrected. However, if the difference exceeds the threshold, a correction factor can be generated, and the preset pressure amplification model can then be corrected based on the correction factor.

[0102] Optionally, when obtaining the peak pressure value inside the single-use fracturing tube 10 and the borehole wall pressure value of the borehole 21 where the single-use fracturing tube 10 is located through a rock-breaking test, a physical model rock mass 20 can be constructed, and a phase change rock-breaking test of the single-use fracturing tube 10 can be performed on it to obtain the required parameters in the test. Specifically, these include:

[0103] S110: Construct a physical model rock mass 20, wherein the physical model rock mass 20 has blast holes 21.

[0104] like Figure 5 As shown, a physical model rock mass 20 can be constructed, and boreholes 21 can be drilled on the physical model rock mass 20. This application does not limit the shape of the physical model rock mass 20; for example, it can be... Figure 5 The cylindrical shape can also be a cube, cuboid, or other shapes.

[0105] S120: Multiple first pressure sensors 30 are arranged in a ring around the blast hole 21 within the physical model rock mass 20.

[0106] Given that the lateral rupture location of the single-use fracturing tube 10 is not fixed and has a randomness, in order to obtain a more accurate borehole wall pressure value, such as Figure 6 As shown, multiple first pressure sensors 30 can be installed in the rock mass 20 of the physical model. The multiple first pressure sensors 30 are arranged in a ring around the circumference of the borehole 21. Thus, the borehole wall pressure value can be detected through the multiple first pressure sensors 30 around the circumference of the borehole 21.

[0107] Of course, this application does not limit the number of the first pressure sensor 30, for example Figure 6 As shown, there can be 8 circles spaced 45 degrees apart, or 6 circles spaced 60 degrees apart, etc.

[0108] In addition, the multiple first pressure sensors 30 can be arranged in a ring or in multiple layers along the length of the borehole 21 to obtain more accurate test data.

[0109] Since the first pressure sensor 30 needs to detect the pressure value of the borehole wall, it can be installed close to the inner wall of the borehole 21, for example... Figure 6 As shown, the first pressure sensor 30 is located on the inner wall of the borehole 21.

[0110] S130: A disposable fracturing tube 10 is inserted into the borehole 21, and there is a gap 23 between the disposable fracturing tube 10 and the inner wall of the borehole 21.

[0111] like Figure 5 As shown, a disposable fracturing tube 10 can be inserted into the borehole 21, and a gap 23 exists between the disposable fracturing tube 10 and the inner wall of the borehole 21, achieving decoupled charging of the disposable fracturing tube 10 and the borehole 21. It should be understood that the order of steps S130 and S120 is not important, and this application does not limit them.

[0112] S140: A second pressure sensor is provided at the end of the disposable rupture tube 10.

[0113] Given the lateral pressure relief method of the disposable fracturing tube 10, in order to accurately obtain the peak pressure value inside the tube, a second pressure sensor can be installed at the end of the disposable fracturing tube 10 to monitor the pressure changes inside the disposable fracturing tube 10.

[0114] S150: Control the phase change rock breaking of the one-time fracturing tube 10 to obtain the borehole wall pressure value through the first pressure sensor 30 and the peak pressure inside the tube through the second pressure sensor.

[0115] Then, the activator 12 inside the fracturing tube is excited by the current to undergo a chemical reaction, which releases a large amount of heat and causes the surrounding liquid carbon dioxide 13 to change phase. The volume of carbon dioxide inside the fracturing tube expands rapidly, breaks through the side wall of the fracturing tube, and releases pressure from the side of the fracturing tube. Then it acts on the hole wall 22 of the borehole 21 to achieve rock breaking. During this process, the hole wall pressure value can be obtained through the first pressure sensor 30 and the peak pressure inside the tube can be obtained through the second pressure sensor. Then, the data obtained by the first pressure sensor 30 and the second pressure sensor can be sent to the host computer connected to their respective signals through a data line or wireless transmission. The host computer receives and summarizes the data.

[0116] To facilitate a better understanding of this application, the following will provide illustrative descriptions based on specific examples.

[0117] First, a physical model of rock mass 20 can be constructed: a cylindrical template is erected, and pressure monitoring holes 22 are reserved on the side wall. The concrete test model is then poured as a whole. After the concrete has initially set, the specimen enters the curing period. After seven days of water curing, the template is removed, and natural curing begins. The total curing period is greater than 28 days. The cylindrical specimen, serving as the physical model rock mass 20, has a diameter of 1000mm and a height of 1000mm. Figure 5 As shown. After the model curing was completed, a hole was drilled in the middle of the model rock mass as blast hole 21, with a diameter of 108 mm, to simulate a fracture hole.

[0118] The experiment used a disposable fracturing tube 10 (externally inflated), with dimensions of 89 mm in diameter, 4 mm in wall thickness, and 700 mm in length. A second pressure sensor was placed inside the fracturing tube at its top, and multiple first pressure sensors 30 were placed on the sidewalls of the physical model rock mass 20. High-speed dynamic data acquisition was performed using a multi-channel data acquisition system, set to automatic triggering. When the first and second pressure sensors detected a certain pressure value, the system automatically triggered and recorded the time-pressure signal at a sampling frequency of 200,000 Hz.

[0119] Six rock-breaking tests were conducted, with liquid carbon dioxide 13 filling amounts ranging from 0.4 kg to 2.95 kg. The charge between the disposable fracturing tube 10 and the inner wall of the borehole 21 was air-decoupled, meaning a certain gap was left unfilled. Based on the ratio of the borehole 21 diameter (excluding the wall thickness of the disposable fracturing tube 10) to the inner diameter of the disposable fracturing tube 10, the radial decoupling coefficient was calculated to be 1.23.

[0120] Table 1. Parameters and Results of the Physical Simulation Experiment

[0121]

[0122]

[0123] The experimental parameters and results are shown in Table 1 above. Figure 8 This is a single-factor statistical graph showing the relationship between the pipe pressure y (MPa) and the filling amount x1 (kg). Figure 7 The single-factor statistical relationship between the pipe pressure y (MPa) and the filling pressure x2 (MPa) is shown in the figure. The fitted relationship is as follows:

[0124]

[0125] y = 46.614x² - 118.643 (R) 2 =0.77)

[0126] It is evident that the correlation between the pipe pressure and the filling pressure is greater than that between the filling volume and the pressure inside the pipe. This is mainly because the state of carbon dioxide changes under different physical environments. Ideally, at the same filling pressure, the weight of carbon dioxide filled is the same. However, in reality, the difference in ambient temperature between the filling pipeline and the disposable fracture tube 10 will significantly affect the filling volume. For example, in experiment 1-2, under a filling pressure of 6 MPa, the filling volume was only 0.3 kg, significantly less than the filling volumes of other groups. These were removed as outliers during the fitting statistics.

[0127] Taking experiments numbered 1-4 as an example: Figure 9 The figures show the pressure-time curves monitored in the pipes for tests 1-4. It can be seen that the peak pressure in the pipes for tests 1-4 was 82.84 MPa. Figure 10 The pressure-time curves of the borehole wall monitored in tests 1-4 show that the peak value of the borehole wall pressure is 79.46 MPa.

[0128] Therefore, based on the peak pressure value inside the pipe obtained from the experiment and the equation for determining the gas pressure value at the gas-rock interface, the corresponding gas pressure value at the gas-rock interface can be obtained.

[0129] Then, by using the rock-breaking test of the single-use fracturing tube 10 to obtain the borehole wall pressure value (peak value) and gas pressure value, the actual test pressure amplification factor corresponding to tests 1-4 was determined to be 2.63 by calculating the ratio of the borehole wall pressure value to the gas pressure value.

[0130] Based on the aforementioned equation for determining the preset pressure amplification model, the theoretical pressure amplification factor for tests 1-4 can be directly calculated to be 2.66. Since the two values ​​are close and within the threshold, no correction is necessary.

[0131] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for analyzing rock-breaking pressure in a single fracturing tube, characterized in that, The method includes: The peak pressure inside the disposable fracturing tube and the borehole wall pressure of the hole where the disposable fracturing tube is located were obtained by rock breaking test of the disposable fracturing tube. Based on the peak pressure value inside the tube and the pressure value on the borehole wall, a prediction model for the borehole wall pressure value is constructed based on a preset pressure amplification model of the gas generated by the phase change of the one-time fracturing tube impacting the borehole wall. The prediction model is used to characterize the correspondence between the peak pressure value inside the tube and the pressure value on the borehole wall. When a gap exists between the disposable fracturing tube and the borehole wall, the step of constructing a prediction model for the borehole wall pressure value based on the peak pressure value inside the tube and the borehole wall pressure value, and based on a preset pressure amplification model of the gas generated by the phase change of the disposable fracturing tube impacting the borehole wall, includes: Based on the peak pressure value inside the pipe, the gas pressure value at the gas-rock interface is determined by the principle of isentropic expansion. Based on the gas pressure value and the borehole wall pressure value, a prediction model for the borehole wall pressure value is constructed using a preset pressure amplification model based on the gas impacting the borehole wall when the gas generated by the one-time fracturing tube phase change impacts the borehole wall. The step of determining the gas pressure value at the gas-rock interface based on the peak pressure value inside the pipe using the isentropic expansion principle includes: The gas pressure value at the gas-rock interface is determined based on the peak pressure value inside the tube, the volume inside the one-time fracturing tube, and the effective volume of the borehole. The determination of the gas pressure value at the gas-rock interface based on the peak pressure value inside the pipe, the volume inside the disposable fracturing pipe, and the effective volume of the borehole includes: , The gas pressure value at the gas-rock interface. The peak pressure value inside the pipe. The length of the disposable fracturing tube, Let be the inner radius of the disposable fracturing tube. It is the isentropic exponent. The length of the borehole is given. The radius of the borehole is given. The thickness of the disposable fracturing tube; The prediction model for the orifice wall pressure value is as follows: , The pressure value of the orifice wall. This refers to the preset pressure amplification model.

2. The method as described in claim 1, characterized in that, The borehole is a cylindrical borehole, and the effective volume of the borehole is: ,in, The effective volume of the borehole is... Pi is the mathematical constant of a circle.

3. The method as described in claim 2, characterized in that, The method further includes: The preset pressure amplification model is determined based on the adiabatic index, initial density, and peak pressure of the gas explosion products in the primary fracturing tube, as well as the density, wave velocity, and gas pressure value of the rock.

4. The method as described in claim 3, characterized in that, The method further includes: The actual test pressure amplification factor is determined based on the ratio of the borehole wall pressure value to the gas pressure value obtained from the rock-breaking test of the disposable fracturing tube. The theoretical pressure amplification factor matching the rock-breaking test of the one-time fracturing tube is determined according to the preset pressure amplification model. A correction factor is determined based on the actual experimental pressure amplification factor and the theoretical pressure amplification factor, and the preset pressure amplification model is corrected based on the correction factor.

5. The method as described in claim 2, characterized in that, The process of obtaining the peak pressure value inside the disposable fracturing tube and the borehole wall pressure value of the borehole where the disposable fracturing tube is located through rock-breaking tests includes: Construct a physical model rock mass, wherein the physical model rock mass has blast holes; Multiple first pressure sensors are arranged in a ring around the periphery of the borehole within the rock mass of the physical model. The disposable fracturing tube is inserted into the borehole, and there is a gap between the disposable fracturing tube and the inner wall of the borehole; A second pressure sensor is provided at the end of the disposable fracturing tube; The one-time fracturing tube phase change rock breaking is controlled to obtain the borehole wall pressure value through the first pressure sensor and the peak pressure inside the tube through the second pressure sensor.

6. The method as described in claim 1, characterized in that, The method further includes: Obtain the actual peak pressure value inside the single-stage rock-breaking tube; The actual peak pressure value inside the pipe is input into the prediction model of the orifice wall pressure value to obtain the predicted orifice wall pressure value corresponding to the actual peak pressure value inside the pipe.

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