A supercritical CO2 phase change energy-generating rock fracture test method

Abstract

The present invention discloses a supercritical CO2 phase change energy-gathering fracturing rock test method, which comprises the following steps: preparing a rock fixed with a strain assembly and a velocity sensor, placing a fracturing tube into a fracturing hole of the rock, and fixing the fracturing tube; turning on the strain assembly and the velocity sensor, detonating the fracturing tube, and collecting and recording data in real time during the test by the strain assembly and the velocity sensor; measuring the point cloud data of the cross-sectional morphology of the broken rock by a three-dimensional laser scanner after the rock is broken, and obtaining its three-dimensional morphology; and calculating and fitting the energy-gathering degree of supercritical CO2 phase change fracturing according to the data collected by the strain assembly and the velocity sensor. The present invention can ascertain the vibration degree and strain difference generated around the rock under the energy-gathering effect, as well as the rock damage morphology, and provide guidance for the efficient use of CO2 rock breaking technology in practical applications.

Description

Technical Field

[0001] The invention relates to the technical field of rock fracturing, and in particular to a supercritical CO2 phase change energy-generating rock fracturing test method. Background Art

[0002] Supercritical CO2 phase change rock fracturing is a physical rock breaking technology. By heating the liquid supercritical CO2 in the fracturing tube, it undergoes a phase change, rapidly expands in volume, and rapidly increases in pressure. Finally, it releases energy by destroying the shear sheet, thereby destroying the rock. Although the energy released by the fracturing tube is much smaller than that of explosives, it can still provide a large amount of energy to destroy the rock. This technology is a new method for rock breaking. The current theory lags behind practice, which leads to the inability to efficiently use this technology in practice. Further experiments are needed to conduct theoretical research.

[0003] There are still two problems in the application of this rock breaking technology in the existing technology: First, in the supercritical CO2 phase change fracturing, energy is released through the release holes evenly and symmetrically arranged on the release head of the fracturing tube. Due to this characteristic, the energy release has a focusing effect. The degree of vibration and strain difference generated around the rock under this focusing effect have not been explored, and the rock damage morphology under this effect is not very clear. Second, in the process of rock breaking, the fracturing tube is placed in the drill hole, and when the energy in the tube is released, a huge recoil force will be generated in the hole, causing the fracturing tube to fly out, affecting the collection results of the test data and posing a safety hazard. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a supercritical CO2 phase change energy-generating rock cracking test method, which solves the problem of lack of theoretical guidance in the practical application of CO2 rock breaking technology.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is:

[0006] In a first aspect, a supercritical CO2 phase change energy-generating fracture rock test method is provided, which comprises the following steps:

[0007] S1, preparing a rock with a strain assembly and a velocity sensor fixed thereon, placing a fracturing tube into a fracturing hole of the rock, and fixing the fracturing tube;

[0008] S2, turning on the strain assembly and the velocity sensor, detonating the fracture tube, and during the test, the strain assembly and the velocity sensor collect and record data in real time;

[0009] S3, after the rock is crushed, a 3D laser scanner is used to measure the point cloud data of the cross-section of the crushed rock to obtain its 3D morphology;

[0010] S4. Calculate and fit the energy accumulation degree of supercritical CO2 phase change cracking based on the data collected by the strain component and velocity sensor.

[0011] Furthermore, step S1 includes the following steps:

[0012] S1.1. Prepare test rocks with crack-causing holes, pour the materials needed to prepare the rocks into a mold, and bury several strain components and velocity sensors in different positions of the rocks in advance;

[0013] S1.2, connect the signal wires of several strain components and speed sensors with the control module, and assemble the data acquisition component;

[0014] S1.3. Lift the protective steel cylinder and surround the rock;

[0015] S1.4. Use shearing pieces to assemble the fracturing tube, fill it with CO2 and place it into the fracturing hole, and use sand to fill the gap between the fracturing tube and the fracturing hole;

[0016] S1.5. A clamp for clamping the fracturing pipe is sleeved on the upper part of the fracturing pipe, and the clamp is connected to the protective steel cylinder through an iron chain; the control module controls the tightening device on the iron chain to open to adjust the tightness of the iron chain so that the fracturing pipe is fixed in the center of the fracturing hole.

[0017] Further, step S2 includes the following steps:

[0018] S2.1. Connect the detonation wire to the two electrodes of the filling head of the fracturing tube;

[0019] S2.2, the control module controls the data acquisition component to start, and the data acquisition component transmits the electrical signal of the collected data to the control module in real time;

[0020] S2.3, connect the detonator and the detonating wire, turn on the detonator and charge it to the detonation voltage, release the voltage to stimulate the cracking tube to complete the detonation;

[0021] S2.4. Stop data collection.

[0022] Furthermore, in step S1.1, the arrangement of several strain components and velocity sensors includes the following steps:

[0023] S1.1.1. Fix the strain components on the front, side and top surfaces of the rock respectively; the strain components on the front and side surfaces of the rock are evenly arranged along the vertical center axis of the surface, and collect strain data in the c direction and z direction respectively;

[0024] S1.1.2. The strain components on the top surface of the rock are evenly arranged along half of the two central axes and half of the diagonal lines of the surface, and strain data in the z direction, c direction, and d direction are collected respectively;

[0025] S1.1.3. Evenly arrange the velocity sensors along the other half of the two central axes and the other half of the diagonal lines of the top surface of the rock, and collect vibration velocity data in the z direction, c direction, and d direction respectively.

[0026] Furthermore, the strain components are respectively arranged on the front, side and top surfaces of the rock. In step S4, the step of calculating and fitting the energy accumulation degree of supercritical CO2 phase change cracking is:

[0027] S4.1. Record the peak strains ε1, ε2, …, ε collected by the top surface strain component i , record the peak vibration speed v1, v2,…, v collected by the speed sensor i ;

[0028] The peak strain value collected by the front strain component is recorded as ε c(1) ,ε c(2) ,…,ε c(i) ; Record the peak strain of the lateral strain component as ε z(1) ,ε z(2) ,…,ε z(i) ;

[0029] Where i is the i-th strain component or the i-th velocity sensor, ε i is the strain data collected for the i-th strain component on the top surface, ε z(i) is the strain data collected from the i-th strain component on the side, ε c(i) The strain data collected for the ith strain component on the front side;

[0030] S4.2. Calculate the peak stresses at the corresponding measuring points on the top, front and side surfaces respectively;

[0031]

[0032] Among them, σ i is the stress collected for the i-th strain component on the top surface, σ z(i) is the stress collected for the i-th strain component on the side, σ c(i) The stress collected for the i-th strain component on the front side; E m is the elastic modulus of rock;υ is the Poisson's ratio of rock;

[0033] S4.3、The different measuring points (σ i , r i ) into the formula P x =σ i r i α Perform fitting and obtain P zx , P cx , P dx Fitting function curve and mathematical expression;

[0034] Among them, P x is the calculated value of burst pressure; P zx is the calculated value of burst pressure in z direction, P cx is the calculated value of the burst pressure in the c direction, P dx is the calculated value of the burst pressure in the d direction; r i is the ratio of the distance from the corresponding measuring point to the center of the fracture hole to the radius of the fracture hole; α is the attenuation index of the stress wave in the rock;

[0035] S4.4, let r i =1, the stress on the crack hole wall is obtained as:

[0036] σ zx =P zx ; σ cx =P cx ; σ dx =P dx ;

[0037] Among them, σ zx is the stress in the z direction of the hole wall, σ cx is the stress in the c direction of the hole wall, σ dx is the stress in the hole wall in the d direction;

[0038] S4.5. Calculate the expansion factor of the released load in each direction.

[0039]

[0040] Where d0 is the thickness of the shear plate; D is the clamping diameter of the shear plate; σ s is the shear strength of the shear plate; k z represents the expansion factor in the z direction, k c is the expansion coefficient in the c direction, k d is the expansion coefficient in the d direction;

[0041] S4.6. By fitting the stresses in different directions into ellipses, we can get the stress distribution expression around the hole wall:

[0042]

[0043] Among them, x and y represent the variables of the horizontal and vertical coordinates respectively; k is the degree of energy concentration.

[0044] From this, we can get the degree of energy accumulation in supercritical CO2 phase change cracking, that is, the k value, also known as the unevenness coefficient, which means the ratio of the load in the main energy accumulation direction to the load in the first energy accumulation direction. When k is 1, the stress distribution expression is the equation of a circle, which means that the load distribution is uniform and there is no change along the hole. The larger the k, the more uneven the load distribution, the greater the force in the main energy accumulation direction, and the more obvious the energy accumulation.

[0045] In a second aspect, a pipe-flying prevention device for fixing a fracturing pipe is provided, the pipe-flying prevention device comprising a protective steel cylinder surrounding the rock and a clamping device sleeved on the outside of the fracturing pipe, the clamping device being connected to the protective steel cylinder by at least two iron chains;

[0046] A tensioner is provided on each iron chain, and the tensioner includes a box body and a brake assembly fixed inside the box body for limiting the rotation of the driving gear. A motor is fixedly connected to the inside of the box body, and the output shaft of the motor is fixedly connected to the central axis of the driving gear; winding gears are meshed on both sides of the driving gear, and the winding gears and the winch for winding the iron chain are fixed on the same rotating shaft, and the rotating shaft is rotatably connected to the box body through a bearing; the motor, brake assembly, data acquisition assembly and clamp are all electrically connected to the control module.

[0047] Further, it is characterized in that the brake assembly includes a first oil cylinder fixedly connected to the inner wall of the box body, the end of the telescopic rod of the first oil cylinder is fixedly connected to an arc-shaped brake plate, the brake plate is provided with an arc-shaped cavity inside, a brake sprocket disc slidably connected to the cavity wall is installed in the cavity, the meshing teeth of the brake sprocket disc extend from the opening of the cavity, and when the telescopic rod is extended to the extreme position, the meshing teeth of the brake sprocket disc mesh with the driving gear;

[0048] The two ends of the brake sprocket are tightly connected with buffer components, and the two buffer components are both in contact with the side wall of the cavity.

[0049] Furthermore, it is characterized in that the buffer component is a high-strength spring, and the elastic modulus of the spring is:

[0050]

[0051] Wherein, π is the circumference of a circle; r is the radius of the fracturing tube; R1 is the radius of the capstan; n is the number of chains; R3 is the radius of the driving gear; δ is the deformation of the spring; β is the angle between the chain and the fracturing tube; and cos(·) is the cosine function.

[0052] Furthermore, the first oil cylinder is electrically connected to the control module, and a torque sensor for transmitting the collected torque signal to the control module is arranged on the central axis of the driving gear. When M=2TR2, the control module controls the first oil cylinder to start;

[0053] Among them, M is the torque data collected by the torque sensor; T is the preset tension value of the chain; R2 is the radius of the rotating shaft.

[0054] Furthermore, the clamp comprises a sleeve-shaped second oil cylinder and at least two pistons arranged in an annular manner along the inner wall curved surface of the second oil cylinder, and the ends of the pistons are fixedly connected with arc-shaped rubber pads; connecting plates equal in number to the iron chains are fixedly connected in an annular manner along the outer wall curved surface of the second oil cylinder, one end of the iron chain is fixed on the connecting plate, and the other end is fixed on the protective steel cylinder;

[0055] The outer wall of the second oil cylinder is provided with a medium inlet and a medium outlet which are connected to the inner cavity of the second oil cylinder; the medium inlet is connected to the external third oil cylinder;

[0056] The third oil cylinder is electrically connected to the control module. The outer wall of the second oil cylinder is provided with a pressure sensor for transmitting the collected pressure signal to the control module. When the control module controls the third oil cylinder to stop delivering the medium to the second oil cylinder;

[0057] Among them, Q is the radial pressure collected by the pressure sensor; μ is the friction coefficient between the rubber pad and the fracturing tube; L is the height of the clamp; r is the radius of the fracturing tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a schematic diagram of the supercritical CO2 phase change energy-generating rock cracking test system;

[0059] Figure 2 is a schematic diagram of the internal structure of the tightener;

[0060] Figure 3 is a schematic diagram of the structure of the brake assembly;

[0061] Figure 4 It is a structural schematic diagram of the clamp;

[0062] Figure 5 is a cross-sectional schematic diagram of a clamp;

[0063] Figure 6 is a schematic diagram of a box body of a tightener;

[0064] Figure 7 The schematic diagram of the arrangement of strain components on the front and side of the rock;

[0065] Figure 8 It is a schematic diagram of the arrangement of strain components and velocity sensors on the top surface of the rock;

[0066] Fig. 9 The stress distribution diagram of the crack hole wall in three directions;

[0067] Fig.10 Schematic diagram of stress ellipse fitting curve when k = 1, 1.5, 2, and 2.5;

[0068] Fig.11Flow chart of the experimental method for supercritical CO2 phase change energy-generating fracture rock test.

[0069] Among them, 1. protective steel cylinder; 2. fixing ring; 3. rock; 31. fracturing hole; 4. tightener; 41. capstan; 42. rotating shaft; 43. motor; 44. chain; 45. winding gear; 46. torque sensor; 47. driving gear; 48. brake assembly; 481. first oil cylinder; 482. telescopic rod; 483. brake sprocket; 484. buffer assembly; 485. brake plate; 49. box body; 6. clamp; 61. rubber pad; 62. second oil cylinder; 63. medium inlet; 64. medium outlet; 65. pressure sensor; 66. connecting piece; 67. notch; 68. piston; 7. fracturing tube; 8. strain assembly; 9. speed sensor. DETAILED DESCRIPTION

[0070] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0071] like Fig.11 As shown, the supercritical CO2 phase change energy-generating rock cracking test method of this scheme includes the following steps:

[0072] S1, preparing a rock 3 with a strain assembly 8 and a velocity sensor 9 fixed thereon, placing a fracturing tube 7 into a fracturing hole 31 of the rock 3, and fixing the fracturing tube 7;

[0073] S2, turning on the strain assembly 8 and the speed sensor 9, detonating the fracturing tube 7, and during the test, the strain assembly 8 and the speed sensor 9 collect and record data in real time;

[0074] S3, after the rock 3 is crushed, the point cloud data of the cross-section of the crushed rock 3 is measured by a three-dimensional laser scanner to obtain its three-dimensional morphology;

[0075] S4. Calculate and fit the energy accumulation degree of supercritical CO2 phase change cracking based on the data collected by the strain assembly 8 and the velocity sensor 9.

[0076] The strain assembly 8 and velocity sensor 9 in the present invention can collect the vibration velocity, strain, pressure change characteristics and crack expansion law at different positions during the fracture process of rock 3 under supercritical CO2 phase change fracturing, so as to explore the vibration degree and strain difference generated around rock 3 under the energy gathering effect, as well as the failure form of rock 3, and provide guidance for the efficient use of CO2 rock breaking technology in practical applications.

[0077] Step S1 further comprises the following steps:

[0078] S1.1, prepare a test rock 3 with a fracture hole 31, pour the materials required for preparing the rock 3 into a mold, and bury a number of strain components 8 and velocity sensors 9 in different positions of the rock 3 in advance;

[0079] S1.2, connect the signal wires of several strain components 8 and speed sensors 9 to the control module, and assemble the data acquisition component;

[0080] S1.3, hoist the protective steel cylinder 1 and surround the rock 3;

[0081] S1.4, assemble the fracturing tube 7 with shearing pieces, fill it with CO2 and put it into the fracturing hole 31, and fill the gap between the fracturing tube 7 and the fracturing hole 31 with sand;

[0082] S1.5. A clamp 6 for clamping the fracturing tube 7 is sleeved on the upper part of the fracturing tube 7, and the clamp 6 is connected to the protective steel cylinder 1 through an iron chain 44; the control module controls the tightening device 4 on the iron chain 44 to open to adjust the tightness of the iron chain 44 so that the fracturing tube 7 is centered and fixed in the fracturing hole 31.

[0083] It is also possible to use an original rock specimen as the test rock 3, drill a hole on the top of the rock 3, and fix a number of strain components 8 and velocity sensors 9 at different positions of the rock 3; when selecting the original rock specimen, the protective steel cylinder 1 should be hoisted first to surround the test rock 3, and then the strain component 8 should be pasted and the sensor should be installed to avoid collision damage to the strain component 8 and the sensor when the measuring equipment is installed first and then the protective steel cylinder is hoisted.

[0084] Step S2 comprises the further steps of:

[0085] S2.1. Connect the detonation wire to the two electrodes of the filling head of the fracturing tube 7;

[0086] S2.2, the control module controls the data acquisition component to start, and the data acquisition component transmits the electrical signal of the collected data to the control module in real time;

[0087] S2.3, after the test personnel have evacuated to the safe area, connect the detonator and the detonating wire, turn on the detonator and charge it to the detonation voltage, release the voltage to stimulate the fracture tube 7 to complete the detonation;

[0088] S2.4. Stop data collection.

[0089] In step S1.1, the arrangement of several strain components 8 and velocity sensors 9 includes the following steps:

[0090] S1.1.1. Fix the strain components 8 to the front, side, and top surfaces of the rock 3 respectively; the strain components 8 on the front and side surfaces of the rock 3 are evenly arranged along the vertical central axes of their respective surfaces to collect strain data in the c direction and the z direction; the strain component 8 is formed by combining three strip-shaped strain gauges in a "one" shape, where two strain gauges are perpendicular, and the middle strain gauge forms a 45° angle with the other two strain gauges.

[0091] S1.1.2. The strain components 8 on the top surface of the rock 3 are evenly arranged along half of the two central axes and half of the diagonal of its surface to collect strain data in the z direction, c direction, and d direction respectively.

[0092] S1.1.3. Arrange the velocity sensors 9 evenly along the other halves of the two central axes and half of the diagonal of the top surface of the rock 3 to collect vibration velocity data in the z direction, c direction, and d direction respectively.

[0093] The fracturing tube 7 releases a supercritical CO2 jet impact through the destruction of the bottom shear slice to fracture the rock wall of the fracture hole 31, causing damage to the rock 3 and generating an energy concentration effect (i.e., the energy concentration effect) in the jet direction. To test the energy concentration effect, the direction perpendicular to the side jet is defined as the main energy concentration direction, i.e., the z direction, the direction perpendicular to the front is the first energy concentration direction, i.e., the c direction, and the direction forming a 45-degree angle with the z direction and the c direction is the second energy concentration direction, i.e., the d direction. (Note: The first energy concentration direction and the second energy concentration direction should not be understood as the "first and second" energy concentration directions in terms of time sequence. The purpose of numbering is to distinguish the two secondary energy concentration directions and should be understood as the "first and second" energy concentration directions.)

[0094] Among them, the front and top surfaces refer to Figure 7 the front and top surfaces with reference to the perspective of the rock 3, and the side surface refers to the surface adjacent to the front and top surfaces. By arranging the strain components 8 and velocity sensors 9 in three directions on the top surface, the stress distribution in different directions can be obtained in the same test, and the strain, pressure, and vibration velocity characteristics of one main energy concentration direction and two secondary energy concentration directions can be obtained at one time, reducing the test error.

[0095] The strain components 8 are respectively arranged on the front, side, and top surfaces of the rock 3. In step S4, the steps for calculating and fitting the energy concentration degree of supercritical CO2 phase change fracturing are as follows:

[0096] S4.1. Record the peak strains ε1, ε2, …, ε i collected by the strain components 8 on the top surface, and record the peak vibration velocities v1, v2, …, v i collected by the velocity sensors 9;

[0097] Record the strain peak collected by the strain components 8 on the front as εc(1) ,ε c(2) ,…,ε c(i) ; Record the peak strain of the side strain component 8 as ε z(1) ,ε z(2) ,…,ε z(i) ;

[0098] Where i is the i-th strain component or the i-th velocity sensor, ε i is the strain data collected for the i-th strain component on the top surface, ε z(i) is the strain data collected from the i-th strain component on the side, ε c(i) The strain data collected for the ith strain component on the front side;

[0099] The data collected by the data acquisition component in the present invention and used for calculation are all data before the rock 3 is broken. The propagation speed of the stress wave is very fast, and the destruction of the rock 3 lags behind the propagation of the stress wave. Therefore, the stress wave and the strain and vibration speed data can be monitored before the rock 3 is broken and used for calculation.

[0100] S4.2. Calculate the peak stresses at the corresponding measuring points on the top, front and side surfaces respectively;

[0101]

[0102] Among them, σ i is the stress collected for the i-th strain component on the top surface, σ z(i) is the stress collected for the i-th strain component on the side, σ c(i) The stress collected for the i-th strain component on the front side; E m is the elastic modulus of rock;υ is the Poisson's ratio of rock;

[0103] S4.3、The (σ i , r i ) into the formula P x =σ i r i α Perform fitting and obtain P zx , P cx , P dx Fitting function curve and mathematical expression;

[0104] Among them, P x is the calculated value of burst pressure; P zx is the calculated value of burst pressure in z direction, P cx is the calculated value of the burst pressure in the c direction, P dx is the calculated value of the burst pressure in the d direction; r iis the ratio of the distance from the corresponding measuring point to the center of the fracture hole to the radius of the fracture hole; α is the attenuation index of the stress wave in the rock;

[0105] Specifically, refer to Figure 7 and Figure 8 , P can be obtained by substituting the data collected by the strain component 8 parallel to the z direction on the top surface zx The fitting function curve is used to obtain the bursting pressure in the main energy gathering direction; the data collected by the strain component 8 parallel to the c direction on the top surface can be substituted into the curve to obtain P cx The fitting function curve is obtained, that is, the bursting pressure in the first energy gathering direction is obtained; the data collected by the strain component 8 parallel to the d direction on the top surface is substituted into the formula to obtain P dx The fitting function curve is used to obtain the blasting pressure in the second energy gathering direction.

[0106] Similarly, the data collected by the side strain component 8 (σ z(i) , r i ) and the data collected by the front strain component 8 (σ c(i) , r i ) into the above formula, we can also find P zx and P cx The fitting function curve and expression can be used to further analyze the difference between the stress distribution on the side and front surface and the stress distribution on the top surface, or to perform three-dimensional analysis. i It refers to the ratio of the vertical distance from the corresponding measuring point to the top surface to the radius of the crack hole.

[0107] S4.4, let r i =1, the stress on the wall of the crack hole (31) is obtained as:

[0108] σ zx =P zx ; σ cx =P cx ; σ dx =P dx ;

[0109] Among them, σ zx is the stress in the z direction of the hole wall, σ cx is the stress in the c direction of the hole wall, σ dx is the stress in the hole wall in the d direction;

[0110] According to the symmetry of the fracture hole 31 and the fracture tube 7, the peak stress distribution around the wall of the fracture hole 31 can be obtained, as shown in Fig. 9 shown.

[0111] S4.5. Calculate the expansion factor of the released load in each direction.

[0112]

[0113] Where d0 is the thickness of the shear plate; D is the clamping diameter of the shear plate; σ s is the shear strength of the shear plate; k z represents the expansion factor in the z direction, k c is the expansion coefficient in the c direction, k d is the expansion coefficient in the d direction.

[0114] The physical meaning of the expansion coefficient is the value P obtained from the experiment. x Compared with the value P( The ratio of the theoretical stress at the time of shear failure to the stress at which the shear plate is broken). The rock 3 will deform when subjected to external stress, and the expansion coefficient describes the relationship between the stress in the rock 3 and the stress applied to the rock 3.

[0115] The expansion coefficient is one of the important parameters describing the inelastic deformation behavior of rock 3, which can help researchers understand the deformation characteristics of rock 3 when subjected to stress, and help researchers better understand the behavior of rock 3 when subjected to stress.

[0116] S4.6. By fitting the stresses in different directions into ellipses, we can get the stress distribution expression around the hole wall:

[0117]

[0118] Among them, x and y represent the variables of the horizontal and vertical coordinates respectively; k is the degree of energy concentration. Fig.10 The coordinate system shown is based on Figure 8 The center point of the mesoscopic fissure is the origin, the main energy-gathering direction, i.e., the z direction, is the x-axis, and the first energy-gathering direction, i.e., the c direction, is the y-axis.

[0119] The k value is also called the non-uniformity coefficient, which means the ratio of the load in the main energy focusing direction to the load in the first energy focusing direction. When k is 1, the stress distribution expression is the equation of a circle, which means that the load distribution is uniform and there is no change along the hole. The larger the k, the more uneven the load distribution, the greater the force in the main energy focusing direction, and the more obvious the energy focusing. Fig.10 .

[0120] For the vibration velocity peaks v1, v2, ..., v i , also divided into different directions, substitute (v i , r i )According to v i =v0r i α After fitting, we can get the specific values ​​of v0 and α. Let r i =1, the initial vibration velocity v of the hole wall in the z, c, and d directions can be obtained zx 、vcx and v dx . Further, the initial vibration velocity of the hole wall is substituted into p ix =v ix ρC p , the initial pressure on the hole wall can be calculated.

[0121] Where ρ is the density of rock, C p is the longitudinal wave velocity in the rock. The above formula can also be used to obtain the initial pressure p of the hole wall in different directions zx ,p cx ,p dx Similarly, according to the symmetry, the degree of energy concentration in the energy concentration effect under supercritical CO2 can be obtained by ellipse fitting, that is, the pressure non-uniformity coefficient around the pore wall. By combining the non-uniformity coefficient under strain and the non-uniformity coefficient under vibration velocity, the degree of energy concentration of the pore wall under supercritical CO2 is finally obtained.

[0122] The initial pressure of the fracturing tube 7 can be adjusted by changing the thickness of the shear plate, the uncoupling coefficient between the fracturing tube 7 and the fracturing hole 31 can be adjusted by changing the aperture of the fracturing hole 31, the ratio of the radius of the fracturing tube 7 to the radius of the fracturing hole 31 can be adjusted, and the type of rock 3 can be changed. According to the above method, the degree of uneven load distribution under different parameters can be obtained.

[0123] In a second aspect, a pipe flying prevention device for fixing a cracked pipe is provided, such as Figure 1 As shown, the anti-flying pipe device includes a sleeve-shaped protective steel cylinder 1 surrounding the rock 3, and a clamp 6 sleeved on the outside of the fracturing pipe 7, and the clamp 6 is connected to the protective steel cylinder 1 through at least two iron chains 44.

[0124] refer to Figure 2 and Figure 6 Each iron chain 44 is provided with a tightener 4, which includes a box body 49 and a brake assembly 48 fixed inside the box body 49 for limiting the rotation of the driving gear 47. The box body 49 is fixedly connected with a motor 43, and the output shaft of the motor 43 is fixedly connected with the central axis of the driving gear 47; both sides of the driving gear 47 are meshed with a winding gear 45, and the winding gear 45 and the winch 41 for winding the iron chain 44 are fixed on the same rotating shaft 42, and the rotating shaft 42 is rotatably connected with the box body 49 through a bearing; the motor 43, the brake assembly 48, the data acquisition assembly and the clamp 6 are all electrically connected to the control module. The tightener 4 can tighten the iron chain 44, thereby pulling the fracture tube 7 to prevent its displacement due to force and affect the test results or the flight of the tube to form a safety hazard.

[0125] The principle of the tightener 4 is as follows: the control module turns on the motor 43, and the motor 43 drives the driving gear 47 to rotate in one direction (clockwise for example), thereby driving the two winding gears 45 meshing therewith to rotate counterclockwise, and driving the capstan 41 to rotate counterclockwise, thereby tightening the iron chain 4. After the tightening is completed, the control module controls the brake assembly 48 to cooperate with the driving gear 47 to limit its rotation, thereby limiting the rotation of the winding gear 45 and the capstan 41, and preventing the iron chain 44 from reversing and falling off.

[0126] Before blasting, a fracturing hole needs to be opened on the rock 3, and then the fracturing tube 7 is inserted into the fracturing hole for blasting. The energy of the fracturing tube 7 is released for a certain period of time, and the impact force generated in the early stage of blasting is sufficient to make the fracturing tube 7 fly out. In order to avoid blasting failure caused by premature tube flight, in actual blasting work, the gap between the fracturing hole and the fracturing tube 7 is filled with sand or the like, and the fracturing tube 7 is fixed by friction. The fracturing tube 7 will fly out after the rock 3 is completely broken.

[0127] However, during the test, the data acquisition components are fixed at different positions of the rock 3, and the displacement of the fracturing tube 7 caused by the shock wave will obviously affect the collection of test data, and thus affect the test results. The test conditions are different from the actual blasting conditions. The opening depth of the fracturing hole 31 in the test is limited, and the friction generated is small, which makes the traditional sand filling fixation method unreliable and unable to prevent the displacement of the fracturing tube 7. When the rock 3 breaks, the sand filling fixation layer is also destroyed, and the fracturing tube 7 can no longer be fixed. In this case, this fixing method is not suitable for this test device. Therefore, this solution additionally sets up a protective device for fixing the fracturing tube 7, which can prevent the fracturing tube 7 from being displaced during the test and thus affecting the test results.

[0128] In one embodiment of this solution, reference Figure 3 The brake assembly 48 includes a first oil cylinder 481 fixedly connected to the inner wall of the box body 49, and an arc-shaped brake plate 485 is fixedly connected to the end of the telescopic rod 482 of the first oil cylinder 481. The brake plate 485 has an arc-shaped cavity inside, and a brake toothed disc 483 slidably connected to the cavity wall is installed in the cavity. The meshing teeth of the brake toothed disc 483 extend from the opening of the cavity, and when the telescopic rod 482 is extended to the limit position, the meshing teeth of the brake toothed disc 483 mesh with the driving gear 47. The two ends of the brake toothed disc 483 are tightly connected with buffer assemblies 484, and the two buffer assemblies 484 are both in contact with the side wall of the cavity.

[0129] When in use, the first oil cylinder 481 controls the extension and retraction of the telescopic rod 482 to enable the brake plate 485 to move up and down, so that the brake toothed disc 483 is engaged or separated with the driving gear 47, and the driving gear 47 can be prevented from rotating when the two are engaged. Specifically, the brake toothed disc 483 includes a fixed plate and meshing teeth fixedly connected to the fixed plate, and the meshing teeth extend out of the cavity. The fixed plate is located in the cavity and is slidably connected to the cavity wall. Since the fixed plate is not fixed to the cavity wall, the size of the fixed plate needs to be larger than the opening of the cavity to prevent the brake toothed disc 483 from being separated from the cavity.

[0130] When the brake toothed disc 483 is meshed with the driving gear 47, the buffer pad 484 prevents the brake toothed disc 483 from sliding along the cavity, thereby stopping the driving gear 47 from rotating and braking the winch 41. In addition, when the fracturing tube 7 explodes, the pulling force of the iron chain 44 on the fracturing tube 7 is converted into a clockwise torque of the winding gear 45, and is also transmitted to the brake toothed disc 483.

[0131] At this time, if the tension on the iron chain caused by the explosion moment is greater than the preset tension value, the brake sprocket 483 will be allowed to produce a smaller rotation under the action of the buffer component 484, causing the winch 41 to rotate a certain amount to buffer the limiting tension on the iron chain 44, thereby protecting the brake component 48 from being damaged.

[0132] Preferably, the buffer assembly 484 is a high-strength spring, and the elastic modulus of the spring is:

[0133]

[0134] Wherein, π is the circumference of a circle; r is the radius of the fracturing tube; R1 is the radius of the capstan; n is the number of chains; R3 is the radius of the driving gear; δ is the deformation of the spring; β is the angle between the chain and the fracturing tube; and cos(·) is the cosine function.

[0135] Since the CO2 in the fracturing tube 7 is released by destroying the bottom shearing piece to form a supercritical CO2 jet to impact the borehole rock wall, the rock is destroyed. The difference of the shearing piece of the fracturing tube 7 will affect the impact force during blasting, thereby affecting the preset tension value on the iron chain 44. During the test process, it is often necessary to use the selection of the shearing piece as a variable to conduct multiple groups of tests with different shearing pieces. Therefore, springs with different elastic moduli can be matched according to different shearing pieces to obtain the most suitable buffering effect. The deformation of the spring is preferably about 0 to 5 mm.

[0136] The first oil cylinder 481 is electrically connected to the control module. A torque sensor 46 for transmitting the collected torque signal to the control module is provided on the central axis of the driving gear 47. When M=2TR2, the control module controls the first oil cylinder 481 to start.

[0137] Among them, M is the torque data collected by the torque sensor; T is the preset tension value of the chain; R2 is the radius of the rotating shaft.

[0138] The torque sensor 46 can monitor the limiting tension on the iron chain 44 to prevent the fracturing tube 7 from flying out after the fracturing tube 7 releases energy. The tension on the iron chain 44 can be calculated from the data M collected by the torque sensor 46. When the tension reaches a preset value, the first oil cylinder 481 can be activated to drive the brake sprocket 483 to move upward to mesh with the driving gear 47.

[0139] refer to Figure 4 and Figure 5 The clamp 6 includes a sleeve-shaped second oil cylinder 62 and at least two pistons 68 arranged in an annular manner along the inner wall curved surface of the second oil cylinder 62, and the end of the piston 68 is fixedly connected to an arc-shaped rubber pad 61; along the outer wall curved surface of the second oil cylinder 62, a connecting piece 66 equal to the number of the iron chain 44 is fixedly connected in an annular manner, one end of the iron chain 44 is fixed to the connecting piece 66, and the other end is fixed to the protective steel cylinder 1;

[0140] The outer wall of the second oil cylinder 62 is provided with a medium inlet 63 and a medium outlet 64 which are connected to the inner cavity of the second oil cylinder 62; the medium inlet 63 is connected to the third oil cylinder outside. The hydraulic oil medium is injected into the second oil cylinder 62 through the medium inlet 63, and the hydraulic oil pushes the piston 68 to move radially. The rubber pad 61 connected to the piston 68 will also move radially and press the fracturing tube 7 in the middle, forming a clamping effect on the fracturing tube 7 to limit the upward movement of the fracturing tube 7. The notch 67 is when the piston 68 is extended, driving the rubber pad 61 away from the second oil cylinder 62, thereby forming a gap between the second oil cylinder 62 and the rubber pad 61.

[0141] When the present invention is implemented, it is preferred that the third oil cylinder is electrically connected to the control module, and the outer wall of the second oil cylinder 62 is provided with a pressure sensor 65 for transmitting the collected pressure signal to the control module. When , the control module controls the third oil cylinder to stop delivering the medium to the second oil cylinder 62. Further, Q can take 1.5 to 2 times the radial pressure as the design value, that is, when or When the control module controls the third oil cylinder to stop delivering the medium to the second oil cylinder 62 .

[0142] Among them, Q is the radial pressure collected by the pressure sensor; μ is the friction coefficient between the rubber pad and the fracturing tube; L is the height of the clamp; r is the radius of the fracturing tube.

[0143] In order to prevent the impact force generated after the fracturing tube 7 explodes from causing the fracturing tube 7 to fly out, the injection of hydraulic oil can be stopped only when the radial pressure Q monitored by the pressure sensor 65 satisfies the above formula. Therefore, the clamp 6 can more accurately control the limiting force on the fracturing tube 7 and ensure that the fracturing tube 7 will not be flushed out when it explodes.

[0144] Preferably, the top of the protective steel cylinder 1 is evenly fixed with fixing rings 2 in a ring shape equal to the number of iron chains 44, and lock buckles are welded at both ends of the iron chains 44. The iron chains 44 are connected to the protective steel cylinder 1 through the fixing rings 2 and the lock buckles. The protective steel cylinder 1 can not only prevent gravel from splashing around during the test, but also provide a reaction force through its own weight to prevent the flying pipe. The protective steel cylinder 1 can be fixed to the ground by anchor bolts and the like. The iron chains 44 can be straightened and tightened by the tightener 4. The number of iron chains 44 can be four, each of which is connected in the same way. The iron chains 44 in each direction are tightened by the tightener 4, and the fracturing tube 7 is centered in the fracturing hole 31 by cooperatively adjusting the tightening degree of the iron chains 44 in four directions.

[0145] The protective steel cylinder 1 is made of steel plate. In one embodiment, the diameter of the protective steel cylinder 1 is 2000 mm, the height is 1000 mm, and the thickness is 10 mm. The fixing ring 2 is made of a steel bar with a diameter of 12 mm and is connected to the protective steel cylinder 1 by welding. The lock buckle is a nut-type lock buckle, and two sections of the opening are provided with threads. After the lock buckle is closed, the two ends of the opening can be tightly fixed and connected by rotating the nut.

[0146] The iron chain 44 can be made of high-strength manganese steel with high tensile strength. A single ring of the iron chain 44 is an elliptical ring formed by bending a steel bar with a diameter of 10 mm. The span of the elliptical minor axis is 7 mm, the major axis is 15 mm, and the length of a single iron chain is 1500 mm. The rock 3 is a rock collected by in-situ cutting or a rock model cast by similar materials, with a length, width and height of 1000 mm. The diameter of the fracture hole 31 is 100 mm and the depth is 500 mm.

[0147] In summary, the present invention can ascertain the vibration degree and strain difference generated around the rock 3 under the energy gathering effect, as well as the failure form of the rock 3, provide guidance for the efficient use of CO2 rock breaking technology in practical applications, and can tighten the fracturing tube 7 through the tightener 4 and the clamp 6 to prevent the fracturing tube 7 from being displaced by the shock wave during the test, thereby affecting the test results or causing safety hazards to the flying tube.

Claims

1. A supercritical CO 2 Phase change energy-induced fracture rock test method, Features: The following steps are involved: S1, preparing a rock (3) having a strain assembly (8) and a velocity sensor (9) fixed thereto, placing a fracturing tube (7) into a fracturing hole (31) of the rock (3), and fixing the fracturing tube (7); S2, turning on the strain component (8) and the speed sensor (9), detonating the fracturing tube (7), and during the test, the strain component (8) and the speed sensor (9) collect and record data in real time; S3, after the rock (3) is crushed, a three-dimensional laser scanner is used to measure point cloud data of the cross-sectional morphology of the crushed rock (3) to obtain its three-dimensional morphology; S4, calculating and fitting the supercritical CO according to the data collected by the strain component (8) and the speed sensor (9). 2 The degree of energy accumulation of phase transformation cracking; Step S1 further comprises the following steps: S1.

1. Prepare a test rock (3) with a crack-causing hole (31), pour the material required for preparing the rock (3) into a mold, and bury a plurality of strain components (8) and velocity sensors (9) in different positions of the rock (3) in advance; S1.2, connecting a plurality of strain components (8) and a speed sensor (9) with signal wires of a control module to assemble a data acquisition component; S1.3, hoist the protective steel cylinder (1) and surround the rock (3); S1.

4. Use shear plates to assemble the fracture tube (7) and fill it with CO. 2 Then, the fracturing tube (7) is placed in the fracturing hole (31), and the gap between the fracturing tube (7) and the fracturing hole (31) is filled with sand particles; S1.

5. A clamp (6) for clamping the fracturing tube (7) is sleeved on the upper part of the fracturing tube (7), and the clamp (6) is connected to the protective steel cylinder (1) via an iron chain (44); the control module controls the tightening device (4) on the iron chain (44) to open, so as to adjust the tightness of the iron chain (44) so ​​that the fracturing tube (7) is fixed in the center of the fracturing hole (31); Step S2 includes the following steps: S2.

1. Connect the detonation wire to the two electrodes of the filling head of the fracturing tube (7); S2.2, the control module controls the data acquisition component to start, and the data acquisition component transmits the electrical signal of the collected data to the control module in real time; S2.3, connect the detonator and the detonating wire, turn on the detonator and charge it to the detonation voltage, release the voltage to stimulate the cracking tube (7) to complete the detonation; S2.4, stop data collection; In step S1.1, the arrangement of a plurality of strain components (8) and a velocity sensor (9) comprises the following steps: S1.1.

1. Fix the strain assembly (8) on the front, side and top surfaces of the rock (3) respectively; the strain assemblies (8) on the front and side surfaces of the rock (3) are evenly arranged along the vertical center axis of the surface, and the strain data in the c direction and the z direction are collected respectively; define the direction perpendicular to the side jet as the main energy focusing direction, i.e., the z direction, the direction perpendicular to the front as the first energy focusing direction, i.e., the c direction, and the direction at an angle of 45 degrees to the z direction and the c direction as the second energy focusing direction, i.e., the d direction; S1.1.2, the strain components (8) on the top surface of the rock (3) are evenly arranged along half of the two central axes and half of the diagonal lines of the surface, and the strain data in the z direction, c direction, and d direction are collected respectively; S1.1.3, evenly arrange the velocity sensors (9) along the other half of the two central axes and the other half of the diagonal lines of the top surface of the rock (3), and collect vibration velocity data in the z direction, c direction, and d direction respectively; In step S4, the supercritical CO 2 The steps of energy accumulation of phase change cracking are: S4.

1. Record the peak strain collected by the top surface strain component (8) , record the peak vibration velocity collected by the velocity sensor (9) ; The peak strain value collected by the front strain component (8) is ; Record the peak strain of the side strain component (8) as ; in, i For the i strain component or i A speed sensor, For the top i The strain data collected by each strain component, For the side i The strain data collected by each strain component, For the positive i Strain data collected by each strain component; S4.

2. Calculate the peak stresses at the corresponding measuring points on the top, front and side surfaces respectively; ； ； ； in, For the top i The stress collected by each strain component, For the side i The stress collected by each strain component, For the positive i The stress collected by each strain component; is the elastic modulus of rock; is the Poisson's ratio of the rock; S4.3、Different measuring points Substitute into the formula Perform fitting and obtain , , Fitting function curve and mathematical expression; in, is the calculated value of burst pressure; is the calculated value of burst pressure in z direction, is the calculated value of the burst pressure in direction c, is the calculated value of bursting pressure in direction d; is the ratio of the distance from the corresponding measuring point to the center of the fissure to the radius of the fissure; is the attenuation index of stress wave in rock; S4.

4. Order =1, the stress on the wall of crack hole (31) is obtained as: ； ； ； in, is the stress in the z direction of the hole wall, is the stress in the c direction of the hole wall, is the stress in the hole wall in the d direction; S4.

5. Calculate the expansion factor of the released load in each direction. ； ； ； in, is the shear sheet thickness; is the shear piece clamping diameter; is the shear strength of the shear sheet; represents the expansion coefficient in the z direction, is the expansion coefficient in the c direction, is the expansion coefficient in the d direction; S4.

6. By fitting the stresses in different directions into ellipses, we can get the stress distribution expression around the hole wall: ； Among them, x and y represent the variables of horizontal and vertical coordinates respectively; k The degree of energy concentration.

2. The supercritical CO according to claim 1 2 Phase change energy-induced fracture rock test method, It is characterized in that In step S1, fixing the fracturing pipe (7) is achieved by an anti-flying pipe device, the anti-flying pipe device comprising a protective steel cylinder (1) surrounding the rock (3) and a clamp (6) sleeved on the outside of the fracturing pipe (7), the clamp (6) being connected to the protective steel cylinder (1) by at least two iron chains (44); Each iron chain (44) is provided with a tensioner (4), the tensioner (4) comprising a box body (49) and a brake assembly (48) fixed inside the box body (49) and used to limit the rotation of the driving gear (47); a motor (43) is fixedly connected inside the box body (49), and the output shaft of the motor (43) is fixedly connected to the central axis of the driving gear (47); winding gears (45) are meshed on both sides of the driving gear (47); the winding gears (45) and a winch (41) for winding the iron chain (44) are fixed on the same rotating shaft (42), and the rotating shaft (42) is rotatably connected to the box body (49) via a bearing; the motor (43), the brake assembly (48), the data acquisition assembly and the clamp (6) are all electrically connected to the control module.

3. The supercritical CO according to claim 2 2 Phase change energy-induced fracture rock test method, It is characterized in that The brake assembly (48) comprises a first oil cylinder (481) fixedly connected to the inner wall of the box body (49); an arc-shaped brake plate (485) is fixedly connected to the end of the telescopic rod (482) of the first oil cylinder (481); an arc-shaped cavity is provided inside the brake plate (485); a brake toothed disc (483) slidably connected to the cavity wall is installed in the cavity; meshing teeth of the brake toothed disc (483) extend from the opening of the cavity; and when the telescopic rod (482) is extended to the limit position, the meshing teeth of the brake toothed disc (483) mesh with the driving gear (47); The two ends of the brake toothed disc (483) are tightly connected to buffer components (484), and the two buffer components (484) are both in contact with the side wall of the cavity.

4. The supercritical CO according to claim 3 2 Phase change energy-induced fracture rock test method, It is characterized in that The buffer component (484) is a high-strength spring, and the elastic modulus of the spring is: ； in, is pi; r is the radius of the fracture tube; R 1 is the radius of the capstan; n is the number of chains; R 3 is the radius of the driving gear; is the deformation of the spring; β is the angle between the iron chain and the cracking tube; cos(·) is the cosine function.

5. The supercritical CO2 phase change energy-generating rock cracking test method according to claim 3, It is characterized in that The first oil cylinder (481) is electrically connected to the control module. The central axis of the driving gear (47) is provided with a torque sensor (46) for transmitting the collected torque signal to the control module. When the control module controls the first oil cylinder (481) to start; in, M The torque data collected by the torque sensor; T is the preset tension value of the chain; R 2 is the radius of the axis of rotation.

6. The supercritical CO2 phase change energy-generating rock fracture test method according to claim 2, It is characterized in that The clamp (6) comprises a sleeve-shaped second oil cylinder (62) and at least two pistons (68) arranged in an annular shape along the inner wall curved surface of the second oil cylinder (62), and the ends of the pistons (68) are fixedly connected to arc-shaped rubber pads (61); connecting pieces (66) equal in number to the iron chains (44) are fixedly connected in an annular shape along the outer wall curved surface of the second oil cylinder (62), one end of the iron chain (44) is fixed to the connecting piece (66), and the other end is fixed to the protective steel cylinder (1); The outer wall of the second oil cylinder (62) is provided with a medium inlet (63) and a medium outlet (64) which are in communication with the internal cavity of the second oil cylinder (62); the medium inlet (63) is connected to an external third oil cylinder; The third oil cylinder is electrically connected to the control module. The outer wall of the second oil cylinder (62) is provided with a pressure sensor (65) for transmitting the collected pressure signal to the control module. When the control module controls the third oil cylinder to stop conveying the medium to the second oil cylinder (62); in, Q The radial pressure collected by the pressure sensor; μ is the friction coefficient between the rubber pad and the crack-causing tube; L is the height of the clamp; r is the radius of the fracture tube.

Images