Method for controlling speed of surface vibration induced by supercritical CO2 phase change fracturing

Abstract

The invention discloses a speed control method for inducing earth surface vibration through supercritical CO2 phase change fracturing, and relates to the technical field of blasting fracturing, an earth surface particle vibration speed calculation model is established based on the short column cartridge blasting theory, and when CO2 phase change fracturing is used for replacing a traditional blasting method, in the actual blasting process, the real blasting speed can be accurately simulated and estimated. According to the method, the required earth surface particle peak vibration speed is acquired according to a test, the earth surface particle peak vibration speed and the corresponding fracturing parameters are collected and integrated to form a data set, a proper fracturing pipe can be quickly selected according to the required earth surface particle peak vibration speed, and the earth surface vibration speed is controlled by selecting the fracturing pipes under different parameters. And a technical support is provided for a supercritical CO2 phase change fracturing technology.

Description

Technical Field

[0001] The invention relates to the technical field of blasting fracturing, and in particular to a method for controlling the velocity of surface vibration induced by supercritical CO2 phase change fracturing. Background Art

[0002] Critical CO2 phase change fracturing is a new type of non-explosive rock breaking technology. This technology uses a heating pipe to quickly change the liquid CO2 at a certain pressure and temperature into a liquid-gas phase, and the volume expands 600 times instantly, thereby generating a strong physical pressure (above 200MPa). It is often used in foundation pit excavation, coal seam permeability enhancement, tunneling, mining and other projects. In recent years, due to its low disturbance advantage, this technology has gradually been applied to vibration-sensitive areas such as major infrastructure protection facility protection areas and ecological protection areas.

[0003] However, in practical applications, the influence of vibration parameters is not considered, and vibration control cannot be achieved accurately. There are still many problems in the existing technology in the research of induced surface vibration: there is a lack of prediction methods for the surface vibration velocity induced by supercritical CO2 phase change fracturing, and it is impossible to determine the required surface vibration velocity based on the blasting impact distance, which is also the safety distance, and thus it is impossible to determine the relevant parameters of the fracturing pipe, and it is impossible to achieve parameter optimization and vibration control of surface vibration. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for controlling the velocity of surface vibration induced by supercritical CO2 phase change fracturing.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0006] A method for controlling the velocity of ground vibration induced by supercritical CO2 phase change cracking is provided, which comprises the following steps:

[0007] S1: Establish a calculation model for the vibration velocity of surface particles based on the short column charge blasting theory;

[0008]

[0009] Among them, ν p is the longitudinal vibration velocity of the surface particles after supercritical CO2 explosion, ν s is the lateral vibration velocity of the surface particles after supercritical CO2 explosion, P b is the CO2 blasting pressure, β is the supercritical CO2 blasting shock wave attenuation coefficient, G is the rock shear modulus, R is the straight-line distance from the surface particle to the center of the fracturing tube, C p is the propagation speed of P wave after supercritical CO2 explosion, C sis the propagation velocity of the S wave after supercritical CO2 explosion, r is the end radius of the fracturing tube, l is the length of the fracturing tube, z is the longitudinal distance from the surface particle to the center of the fracturing tube, and a is the transverse distance from the surface particle to the center of the fracturing tube;

[0010] S2: Conducting a field monitoring test of the surface vibration velocity induced by supercritical CO2 phase change cracking, collecting the surface particle vibration velocities corresponding to different blasting impact distances in the test, obtaining a first data set, using the first data set to train a surface particle vibration velocity calculation model, and determining the supercritical CO2 blasting shock wave attenuation coefficient;

[0011] S3: collecting the peak vibration velocity and fracture parameters of the surface particles in the field monitoring test of step S2 to obtain a second data set; searching and optimizing the fracture parameters in the second data set according to the peak vibration velocity of the target surface particles to determine the fracture parameter group;

[0012] S4: Input the fracture parameter group and the safety distance into the trained surface particle vibration velocity calculation model to obtain the estimated vibration velocity corresponding to the safety distance. When the estimated vibration velocity is less than the safety threshold, the fracture parameter group is output; otherwise, the second data set is searched and optimized again, and the new fracture parameter group obtained by the optimization is executed again in S4.

[0013] Furthermore, the fracturing parameters include the length, inner diameter, wall thickness, tensile strength of the fracturing tube and the Poisson's ratio, elastic modulus, and density of the rock mass.

[0014] Furthermore, the step S3 is specifically as follows:

[0015] A1: perform data augmentation on the second database to obtain an augmented optimization database;

[0016] A2: Extract several groups of fracture parameters corresponding to the peak vibration velocity of the target surface particles;

[0017] A3: Calculate the cost of the fracturing pipe used in each extracted fracturing parameter group, and select the fracturing parameter group with the lowest fracturing pipe cost as the optimal fracturing parameter.

[0018] Furthermore, the step A1 is specifically as follows:

[0019] A11: Perform linear regression analysis on each fracture parameter and the peak vibration velocity of the surface particle to obtain a regression model of each fracture parameter and the peak vibration velocity of the surface particle;

[0020] A12: Based on the Bayesian model averaging method, the regression models obtained in step A11 are fused to obtain a fused regression equation;

[0021] A13: Determine the value range of each fracture parameter, evenly select values ​​within the value range, and obtain several parameter combinations;

[0022] A14: Bring several parameter combinations into the fusion regression model to obtain the corresponding peak vibration velocity of the surface particles, and integrate them to obtain the optimization database.

[0023] The beneficial effects of the present invention are:

[0024] The present invention establishes a surface particle vibration velocity calculation model based on the short-column charge blasting theory. When using CO2 phase change fracturing to replace the traditional blasting method, it can accurately simulate and estimate the peak vibration velocity of the surface particles required in the actual blasting process, and integrate the peak vibration velocity of the surface particles and the corresponding fracturing parameters according to the test collection to form a data set. It can quickly select a suitable fracturing tube according to the required peak vibration velocity of the surface particles, and realize the control of the surface vibration velocity by selecting the fracturing tube under different parameters. It provides technical support for supercritical CO2 phase change fracturing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a simplified diagram of the Heelan solution calculation for a cylindrical cavity;

[0026] Figure 2 It is a curve diagram showing the relationship between the vibration velocity and the length of the fracture pipe at different positions;

[0027] Figure 3 It is a curve diagram showing the relationship between the vibration velocity and the inner diameter of the fracture pipe at different positions;

[0028] Figure 4 It is a curve diagram showing the relationship between vibration velocity and cracked pipe wall thickness at different positions;

[0029] Figure 5 It is a curve diagram showing the relationship between vibration velocity and tensile strength of cracked pipe at different positions;

[0030] Figure 6 It is the relationship curve between vibration velocity and Poisson's ratio of rock mass at different positions;

[0031] Figure 7 It is the relationship curve between vibration velocity and rock elastic modulus at different positions;

[0032] Figure 8 This is a curve diagram showing the relationship between vibration velocity and rock density at different positions. DETAILED DESCRIPTION

[0033] 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.

[0034] A method for controlling the velocity of ground vibration induced by supercritical CO2 phase change cracking, characterized in that it comprises the following steps:

[0035] S1: Establish a calculation model for the vibration velocity of surface particles based on the short column charge blasting theory;

[0036]

[0037] Among them, ν p is the longitudinal vibration velocity of the surface particles after supercritical CO2 explosion, ν s is the lateral vibration velocity of the surface particles after supercritical CO2 explosion, P b is the CO2 blasting pressure, β is the supercritical CO2 blasting shock wave attenuation coefficient, G is the rock shear modulus, R is the straight-line distance from the surface particle to the center of the fracturing tube, C p is the propagation speed of P wave after supercritical CO2 explosion, C s is the propagation velocity of the S wave after supercritical CO2 explosion, r is the end radius of the fracturing tube, l is the length of the fracturing tube, z is the longitudinal distance from the surface particle to the center of the fracturing tube, and a is the transverse distance from the surface particle to the center of the fracturing tube;

[0038] The derivation principle of the surface particle vibration velocity calculation model is as follows:

[0039] S1.1. Use the punching shear failure formula to calculate the initial peak pressure after the supercritical CO2 phase change:

[0040]

[0041] Where: P0 is the pressure when the energy dissipation plate is destroyed, MPa; d0 is the thickness of the energy dissipation plate, mm; D is the clamping diameter of the energy dissipation plate, mm; σ s It is the shear strength of the material, generally 0.6 to 0.7 times the tensile strength, MPa.

[0042] S1.2. Considering the incident stress amplification effect on the wall of the fracture-causing hole, calculate the incident stress on the hole wall in the case of coupled buried fracture-causing pipe;

[0043]

[0044] Where, P2 is the hole wall pressure, MPa; d gand d t are the diameters of the fracture tube and the fracture hole, m respectively; n is the pressure increase multiple, and in this embodiment, n=6.

[0045] S1.3, introduce the short column charge blasting theory, the cylindrical cavity Heelan solution calculation diagram is as follows Figure 1 As shown, only the lateral impact load on the hole wall is considered to derive the vibration velocity calculation formula at each particle point (a, z) on the surface;

[0046] The displacement (u, v, w) at any point on the surface induced by supercritical CO2 phase change is expressed by the wave equation in cylindrical coordinates:

[0047]

[0048] In the formula, Φ0, Θ0, χ0 are auxiliary wave functions, C p and C s are the propagation velocities of P wave and S wave after supercritical CO2 explosion, which can be expressed as:

[0049]

[0050] Where E is the elastic modulus of rock, μ is the Poisson's ratio of rock, and ρ is the density of rock.

[0051] The stress boundary condition of the crack hole is:

[0052]

[0053] Let P(t) = P b g(t), g(t) is the decay function of CO2 explosion pressure with time.

[0054] After supercritical CO2 blasting, the vertical vibration displacement of each point on the ground surface can be expressed as:

[0055]

[0056] Where V is the volume of the short cylinder, V = πr 2 l; G is the rock shear modulus; u p ,u s They are the displacements caused by the compression wave P wave and the shear wave S wave at time t respectively.

[0057] Assume that the decay function of CO2 explosion pressure over time is P(t)=P b e -βt , β is the attenuation coefficient of supercritical CO2 explosion shock wave; substituting it into equation (6) and taking the derivative with respect to time, we can obtain the attenuation relationship between the vibration velocity of surface particles and distance and time.

[0058]

[0059] l is the length of the short cylinder, P b is the CO2 blasting pressure; the time required for the blasting impact pressure to enter the rock mass is measured in microseconds, so the time factor is considered to be 0, and the attenuation relationship of the vibration velocity of the surface particles with the distance can be simplified, that is, the calculation model of the vibration velocity of the surface particles;

[0060] S2: Conducting a field monitoring test of the surface vibration velocity induced by supercritical CO2 phase change cracking, collecting the blasting impact distance and the peak vibration velocity of the surface particles in the test, obtaining a first data set, and using the first data set to train a surface particle vibration velocity calculation model;

[0061] When implementing it, the following steps are taken:

[0062] S2.1. Use a rock drill to drill a hole in the rock formation to obtain a fracture hole with a diameter of 0.09 m and a depth of 5 m;

[0063] S2.2. Use an ohmmeter to measure the resistance of each fracturing tube. If the measured resistance value is within the normal range, it means that the circuit of each fracturing tube is connected and can be detonated normally; if the measured resistance value is not within the normal range, it means that the circuit is not connected correctly and the fracturing tube cannot be powered normally;

[0064] S2.3. Place the 76-type fracturing tube into the drilled fracturing hole, and fill the gap between the fracturing tube and the fracturing hole with stone powder or sand to prevent the fracturing tube from flying out of the fracturing hole during the fracturing process;

[0065] S2.4. Use QL-PZ03 filling machine to transport the liquid CO2 stored in QL-PZ06 liquid storage tank through the filling hose to the fracturing tube buried in the fracturing hole, so that each fracturing tube is filled with supercritical CO2.

[0066] S2.5. Connect the fracture tubes with normal resistance in series through wires and measure the resistance. If the measured resistance is within the normal range, it means that the fracture tubes can be stimulated normally. Otherwise, check them one by one, measure them repeatedly and replace the fracture tubes that cannot be stimulated normally until the resistance is normal.

[0067] S2.6. Arrange the DH610c magnetoelectric vibration velocity sensor according to the test plan, connect the wires, debug the 5922N dynamic signal tester and related software, and prepare for data collection.

[0068] S2.7. Connect the detonator and perform pre-detonation checks. After all personnel have evacuated to a safe area, rotate the CHA-2000E igniter switch to complete detonation.

[0069] S2.8. Substitute the collected peak vibration velocity data of surface particles at different locations into the surface particle vibration velocity calculation model for regression analysis.

[0070] In this embodiment, the collected data are shown in Table 1;

[0071] Table 1

[0072] Epicenter distance a / m <![CDATA[Vertical peak particle velocity vp / cm·s -1 > 5 2.296 10 0.192 15 0.138 20 0.124 25 0.121 3 5.872 9 0.426 18 0.054 30 0.027 45 0.063 6 1.225 18 0.143 34 0.081 52 0.053 3 5.048 9 0.381 17 0.324 23 0.082 35 0.033

[0073] In Table 1, there are two groups of earthquake source distances of 3m and 9m, which represent the vertical vibration peak velocities measured at two different positions with a radius of 3m or 9m, centered on the fracture pipe;

[0074] The experimental data in Table 1 were solved by nonlinear regression using Matlab programming. In this embodiment, the supercritical CO2 explosion shock wave attenuation coefficient β was 2631.07, and the training was completed.

[0075] S3: collecting the peak vibration velocity and fracture parameters of the surface particles in the field monitoring test of step S2 to obtain a second data set; searching and optimizing the fracture parameters in the second data set according to the peak vibration velocity of the target surface particles to determine the fracture parameter group; specifically:

[0076] A1: Perform data augmentation on the second database to obtain an augmented optimization database; specifically:

[0077] A11: Perform linear regression analysis on each fracture parameter and the peak vibration velocity of the surface particle to obtain a regression model of each fracture parameter and the peak vibration velocity of the surface particle;

[0078] In this embodiment, the methods S2.1-S2.8 are used. The horizontal distances between the ground and the fracturing pipe are 3m, 4m, 5m, 6m, 8m and 10m. The length, inner diameter, wall thickness, tensile strength of the fracturing pipe, Poisson's ratio, elastic modulus, density of the rock mass and the peak vibration velocity of the surface particles are fitted as follows: Figure 2-Figure 8 shown.

[0079] A12: Based on the Bayesian model averaging method, the regression model obtained in step A11 is fused to obtain a fused regression equation; the Bayesian model averaging method fused regression model is an existing technology, so it will not be described in detail.

[0080] A13: Determine the value range of each fracture parameter, evenly select values ​​within the value range, and obtain several parameter combinations;

[0081] A14: Bring several parameter combinations into the fusion regression model to obtain the corresponding peak vibration velocity of the surface particles, and integrate them to obtain the optimization database.

[0082] A2: Extract several groups of fracture parameters corresponding to the peak vibration velocity of the target surface particles;

[0083] Specifically, when the target is subjected to fracturing blasting, a fracturing hole with a depth of 5m is determined, that is, the longitudinal distance z from the surface particle to the center of the fracturing tube is 5m; assuming that the blasting radius is 10m, when the lateral distance a from the surface particle to the center of the fracturing tube is 10, the lateral vibration velocity and the longitudinal vibration velocity are respectively less than or equal to the corresponding safety threshold, and the safety threshold is artificially set according to the actual situation; in the second database, when a=10, the peak vibration velocity of the surface particle is less than the safety threshold and 3 to 5 groups of fracturing parameter groups closest to the safety threshold are retrieved and determined. The specific number of groups is determined according to the actual situation. In this embodiment, the first 3 groups of fracturing parameter groups closest to the safety threshold are taken. When the peak vibration velocity of the surface particle of the fracturing parameter group at a=10 is the same, the same multiple groups of parameter groups are treated as parallel and A3 is executed together, that is, when two groups are tied for the first place, and the second and third groups are not the same, there are 4 groups of fracturing parameter groups executing A3.

[0084] Because the vibration velocities of the surface particles integrated in the second database are all peak velocities at the corresponding positions, when blasting is performed using a determined set of fracturing parameters, the vibration velocity at a safe distance will not exceed the safety specification.

[0085] A3: Calculate the cost of the fracturing pipe used in each fracturing parameter group respectively, and select the fracturing parameter group with the lowest fracturing pipe cost as the optimal fracturing parameter.

[0086] S4: Input the fracture parameter group and the safety distance into the trained surface particle vibration velocity calculation model to obtain the estimated vibration velocity corresponding to the safety distance. When the estimated vibration velocity is less than the safety threshold, the fracture parameter group is output; otherwise, the second data set is searched and optimized again, and the new fracture parameter group obtained by the optimization is executed again in S4. Specifically, the fracture parameter group with an estimated vibration velocity greater than the safety threshold is cleared, and in step A2, the first three fracture parameter groups are re-determined, and A3 is continued until S4 successfully outputs the fracture parameter group.

Claims

1. A method for controlling the velocity of ground vibration induced by supercritical CO2 phase change fracturing, characterized in that: The steps include: S1: Establish a calculation model for the vibration velocity of surface particles based on the short column charge blasting theory; Among them, ν p is the longitudinal vibration velocity of the surface particles after supercritical CO2 explosion, ν s is the lateral vibration velocity of the surface particles after supercritical CO2 explosion, P b is the CO2 blasting pressure, β is the supercritical CO2 blasting shock wave attenuation coefficient, G is the rock shear modulus, R is the straight-line distance from the surface particle to the center of the fracturing tube, C p is the propagation speed of P wave after supercritical CO2 explosion, C s is the propagation velocity of the S wave after supercritical CO2 explosion, r is the end radius of the fracturing tube, l is the length of the fracturing tube, z is the longitudinal distance from the surface particle to the center of the fracturing tube, and a is the transverse distance from the surface particle to the center of the fracturing tube; S2: Conducting a field monitoring test of the surface vibration velocity induced by supercritical CO2 phase change cracking, collecting the surface particle vibration velocities corresponding to different blasting impact distances in the test, obtaining a first data set, using the first data set to train a surface particle vibration velocity calculation model, and determining the supercritical CO2 blasting shock wave attenuation coefficient; S3: collecting the peak vibration velocity and fracture parameters of the surface particles in the field monitoring test of step S2 to obtain a second data set; searching and optimizing the fracture parameters in the second data set according to the peak vibration velocity of the target surface particles to determine the fracture parameter group; S4: Input the fracture parameter group and the safety distance into the trained surface particle vibration velocity calculation model to obtain the estimated vibration velocity corresponding to the safety distance. When the estimated vibration velocity is less than the safety threshold, the fracture parameter group is output; otherwise, the second data set is searched and optimized again, and the new fracture parameter group obtained by the optimization is executed again in S4.

2. The method for controlling the velocity of ground vibration induced by supercritical CO2 phase change fracturing according to claim 1, characterized in that: The fracturing parameters include the length, inner diameter, wall thickness, tensile strength of the fracturing tube and the Poisson's ratio, elastic modulus, and density of the rock mass.

3. The method for controlling the velocity of ground vibration induced by supercritical CO2 phase change fracturing according to claim 1, characterized in that: The step S3 is specifically as follows: A1: perform data augmentation on the second database to obtain an augmented optimization database; A2: Extract several groups of fracture parameters corresponding to the peak vibration velocity of the target surface particles; A3: Calculate the cost of the fracturing pipe used in each extracted fracturing parameter group, and select the fracturing parameter group with the lowest fracturing pipe cost as the optimal fracturing parameter.

4. The method for controlling the velocity of ground vibration induced by supercritical CO2 phase change fracturing according to claim 3 is characterized in that: The step A1 is specifically as follows: A11: Perform linear regression analysis on each fracture parameter and the peak vibration velocity of the surface particle to obtain a regression model of each fracture parameter and the peak vibration velocity of the surface particle; A12: Based on the Bayesian model averaging method, the regression models obtained in step A11 are fused to obtain a fused regression equation; A13: Determine the value range of each fracture parameter, evenly select values ​​within the value range, and obtain several parameter combinations; A14: Bring several parameter combinations into the fusion regression model to obtain the corresponding peak vibration velocity of the surface particles, and integrate them to obtain the optimization database.

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