A comprehensive numerical model and microseismic data-driven high-position rock layer fracturing anti-impact effect evaluation method

Abstract

The application discloses a kind of high position stratum fracturing anti-scouring effect evaluation methods driven by comprehensive numerical model and microseismic data, 1, microseismic monitoring system is installed in the region to be evaluated;2, the numerical model of the region to be evaluated is established;3, traverse the numerical model of the region to be evaluated, obtain the coordinates of model unit body;4, import the microseismic coordinates and energy generated by fracturing;5, traverse the unit body of entire model and all microseismic, form the cumulative deformation energy of the unit body;6, calculate the damage parameter value of model unit body;7, obtain the parameters of unit body, and according to the damage parameter value of each unit body, unit body parameter weakening is carried out, to realize water injection weakening stratum;8, if the damage parameter value of unit body is greater than 0.5, the unit body is assigned as null model, to realize fracturing deterioration stratum, otherwise, no processing is carried out;9, working face excavation is carried out and balanced, the stress distribution in front of working face under no fracturing state is compared, and fracturing effect is evaluated.

Description

Technical Field

[0001] This invention relates to a method for evaluating the effectiveness of hydraulic fracturing and erosion prevention in high-altitude rock formations, driven by a comprehensive numerical model and microseismic data. Background Technology

[0002] Rockburst is a mining dynamic phenomenon caused by the sudden release of elastic energy accumulated in coal and rock masses, resulting in massive destruction. Its instantaneous explosiveness poses a serious threat to mine safety. In recent years, with the rapid development of computer technology and numerical simulation technology, numerical simulation has become an irreplaceable method for modern engineering analysis and theoretical research on high-stress potential areas during working face mining.

[0003] On the one hand, general numerical simulation results are too general to reflect specific stress concentration areas during mining operations, while areas of microseismic accumulation often highlight the potential for stress concentration. On the other hand, hydraulic fracturing can weaken the formation through water injection and deteriorate the formation through fracturing, reducing the overall static load level of the coal seam below the fracturing zone. However, fracturing high-level rock formations is an irreversible process, making it impossible to compare its anti-scour effect in actual field operations. Therefore, a solution is urgently needed to address these issues. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a method for evaluating the anti-scour effect of high-level rock strata fracturing driven by a comprehensive numerical model and microseismic data. By analyzing the stress distribution of the surrounding rock during the mining process after fracturing, and comparing it with the stress distribution of the surrounding rock during mining without fracturing, the anti-scour effect of high-level rock strata fracturing is assessed.

[0005] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution:

[0006] A method for evaluating the effectiveness of hydraulic fracturing and scour prevention in high-lying rock formations, driven by a comprehensive numerical model and microseismic data, includes the following steps:

[0007] Step 1: Install a microseismic monitoring system in the area to be evaluated, including ground-mounted acquisition and recording equipment and underground probes. Use the microseismic monitoring system to acquire the seismic waveform signals induced by fracturing and solve for the source parameters.

[0008] Step 2: Establish a numerical model of the area to be evaluated based on the actual coal-bearing characteristics and mining conditions;

[0009] Step 3: Traverse the numerical model of the region to be evaluated and obtain the coordinates of the model unit cells;

[0010] Step 4: Import the microseismic coordinates and energy generated by fracturing;

[0011] Step 5: Traverse all the unit cells and microseismic events of the entire model. Using the center of the model unit cell as the center point and the ellipsoid as the region statistical window, determine whether the microseismic event is within the statistical window of the unit cell. If the microseismic event is within the statistical window of the unit cell, then accumulate the deformation energy in the region to form the cumulative deformation energy of the unit cell.

[0012] Step 6: Traverse the entire model and calculate the damage parameter values ​​of the model unit.

[0013] Step 7: Traverse the entire model, obtain the parameters of the unit cells, and weaken the unit cell parameters according to the damage parameter values ​​of each unit cell to achieve water injection to weaken the formation.

[0014] Step 8: Traverse the entire model. If the damage parameter value of a unit is greater than 0.5, assign the unit to the null model to realize the fracturing and deterioration of the formation; otherwise, do not process it.

[0015] Step 9: Excavate the working face and perform balancing calculations. Compare the stress distribution in front of the working face under the non-fracturing state to evaluate the fracturing effect.

[0016] Preferably, in step 1, the microseismic monitoring system calculates the coordinates and energy magnitude of the microseismic events based on the seismic signals fed back from each receiving channel.

[0017] Preferably, step 2 specifically includes the following steps:

[0018] a) Establish a numerical model based on the actual coal seam characteristics and mining conditions, determine the model size, and construct the lithology and parameters of the coal seam and its roof and floor.

[0019] b) Set the displacement boundary conditions for the model;

[0020] c) Set the stress boundary conditions for the model;

[0021] d) Initial stress equilibrium.

[0022] Preferably, in step 5, the radius of the ellipsoid statistical window in the x-axis and y-axis directions is θ, and the radius in the z-axis direction is δ, where δ is greater than θ.

[0023] Preferably, θ is 20m and δ is 50m.

[0024] Preferably, the cumulative deformation energy of the unit cell is calculated using the following formula:

[0025]

[0026] In the formula, ε Ei N is the cumulative deformation energy of unit i; i E represents the number of microseisms within the statistical window of element i ellipsoid; ijLet be the energy of the j-th microseismic event within the statistical window of unit i ellipsoid.

[0027] Preferably, the damage parameter value of the unit cell is calculated using the following formula:

[0028]

[0029]

[0030] In the formula, D i ε represents the damage parameter value of unit i; F The average cumulative deformation energy; max{ε Ei} represents the maximum cumulative deformation energy in the entire model; D C is the damage parameter value corresponding to the fully damaged state; exp is an exponential function with the natural constant e as the base.

[0031] Preferably, in step 7, the cohesion, tensile strength, and internal friction angle parameters of the unit are weakened.

[0032] Preferably, in step 7, the formation is weakened by water injection using the following formula:

[0033] C i =C i0 (1-D i )

[0034] σ it =σ it0 (1-D i )

[0035]

[0036] In the formula, C i C represents the cohesion of unit i after weakening; i0 σ represents the cohesion of unit i before weakening; it σ represents the tensile strength of element i after weakening; it0 The tensile strength of unit i before weakening; The internal friction angle of unit i after weakening; The internal friction angle of unit i before weakening.

[0037] Preferably, FLAC is used. 3D The finite difference method is used to evaluate the effectiveness of hydraulic fracturing and erosion prevention in high-altitude rock formations driven by a comprehensive numerical model and microseismic data.

[0038] The beneficial effects of this invention are:

[0039] This invention employs a numerical simulation method to calculate the damage parameters of the coal and rock mass through microseismic events generated during fracturing. Based on these damage parameters, the parameters of the coal and rock mass are weakened, and a null unit model is assigned to generate fractures. This achieves the effects of hydraulic fracturing to weaken and deteriorate the formation, thereby analyzing the stress distribution of the surrounding rock during mining after fracturing. By comparing the stress distribution of the surrounding rock during mining without fracturing, the anti-scour effect of fracturing high-level rock formations is evaluated. The method is scientific, reliable, practical, and widely applicable. Attached Figure Description

[0040] Figure 1 This is a flowchart of a method for evaluating the anti-scour effect of high-level rock strata fracturing driven by a comprehensive numerical model and microseismic data, according to the present invention.

[0041] Figure 2 This is a schematic diagram of the numerical model in an embodiment of the present invention;

[0042] Figure 3 This is a schematic diagram showing the distribution of micro-vibrations generated during fracturing of the 401106 working face in an embodiment of the present invention;

[0043] Figure 4 This is a simulation result of the excavation of the 401106 working face in the absence of hydraulic fracturing in the embodiment of the present invention;

[0044] Figure 5 This is a simulation result of the excavation after the working face 401106 was under fracturing conditions in the embodiment of the present invention. Detailed Implementation

[0045] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0046] A comprehensive numerical model and microseismic data-driven method for evaluating the effectiveness of hydraulic fracturing and erosion control in high-lying rock formations, such as... Figure 1 As shown, it includes the following steps:

[0047] Step 1: Install a microseismic monitoring system in the area to be evaluated, including ground-based acquisition and recording equipment and underground probes. Use the microseismic monitoring system to acquire the seismic waveform signals induced by fracturing and solve for the source parameters, such as the coordinates and energy magnitude of the microseismic events.

[0048] Step 2: Establish a numerical model for the area to be evaluated based on the actual coal-bearing characteristics and mining conditions, and optimize the model, including:

[0049] a) Establish a numerical model based on the actual coal seam characteristics and mining conditions, determine the model size, and construct the lithology and parameters of the coal seam and its roof and floor.

[0050] b) Set the displacement boundary conditions for the model;

[0051] c) Set the stress boundary conditions for the model;

[0052] d) Initial stress balancing is required upon first use.

[0053] Step 3: Traverse the numerical model of the region to be evaluated and obtain the coordinates of the model unit cells.

[0054] Step 4: Import the microseismic coordinates and energy generated by fracturing.

[0055] Step 5: Traverse all the unit cells and microseismic events of the entire model. Using the center of the unit cell as the center point and the ellipsoid as the regional statistical window, determine whether the microseismic event is within the statistical window of the unit cell. If the microseismic event is within the statistical window of the unit cell, then accumulate the deformation energy in the region to form the cumulative deformation energy of the unit cell.

[0056] In this statistical window, the radii of the ellipsoid along the x-axis and y-axis are both θ, and the radius along the z-axis is δ, where δ is greater than θ. Preferably, θ is 20m and δ is 50m.

[0057] Preferably, the cumulative deformation energy of the unit cell is calculated using the following formula:

[0058]

[0059] In the formula, ε Ei N is the cumulative deformation energy of unit i; i E represents the number of microseisms within the statistical window of element i ellipsoid; ij Let be the energy of the j-th microseismic event within the statistical window of unit i ellipsoid.

[0060] Step 6: Traverse the entire model and calculate the damage parameter values ​​of the model elements. Preferably, the damage parameter values ​​of the elements are calculated using the following formula:

[0061]

[0062]

[0063] In the formula, D i ε represents the damage parameter value of unit i; F The average cumulative deformation energy; max{ε Ei} represents the maximum cumulative deformation energy in the entire model; D C is the damage parameter value corresponding to the fully damaged state; exp is an exponential function with the natural constant e as the base.

[0064] To facilitate the management and retrieval of the acquired data, three matrices can be established: the model coordinate matrix Mat_mod_coord(n_zone,4), the source parameter matrix Mat_seic_coord(n_seic,4), and the damage parameter matrix Mat_dam(n_zone,1). Specifically: the first three columns of the model coordinate matrix Mat_mod_coord() store the coordinates of the model elements, and the fourth column stores the cumulative deformation energy of the model elements; the first three columns of the source parameter matrix Mat_seic_coord() store the coordinates of the microseisms, and the fourth column stores the energy of the microseisms; the damage parameter matrix Mat_dam() stores the damage parameter values ​​of the model elements; where n_zone represents the number of model elements, and n_seic represents the number of microseisms.

[0065] Then: the coordinates of the obtained model element can be stored in the first three columns of the model coordinate matrix Mat_mod_coord(); the microseismic coordinates and energy generated by the imported fracturing can be stored in the source parameter matrix Mat_seic_coord(); the cumulative deformation energy of the element can be stored in the fourth column of the model coordinate matrix Mat_mod_coord(); and the damage parameter values ​​of the element can be stored in the damage parameter matrix Mat_dam().

[0066] Step 7: Traverse the entire model, obtain the parameters of the unit cells, and weaken the unit cell parameters according to the damage parameter values ​​of each unit cell to achieve formation weakening through water injection. For example, the cohesion, tensile strength and internal friction angle parameters of the unit cells can be weakened.

[0067] Preferably, in step 7, the formation is weakened by water injection using the following formula:

[0068] C i =C i0 (1-D i )

[0069] σ it =σ it0 (1-D i )

[0070]

[0071] In the formula, C i C represents the cohesion of unit i after weakening; i0 σ represents the cohesion of unit i before weakening; it σ represents the tensile strength of element i after weakening; it0 The tensile strength of unit i before weakening; The internal friction angle of unit i after weakening; The internal friction angle of unit i before weakening.

[0072] Step 8: Traverse the entire model. If the damage parameter value of a unit is greater than 0.5, assign the unit to the null model to realize the fracturing and deterioration of the formation; otherwise, do not process it.

[0073] Step 9: Excavate the working face and perform balancing calculations to stabilize the stress distribution in the surrounding rock. Compare the stress distribution in front of the working face under the unfracturing state to evaluate the fracturing effect: If the advance support pressure in front of the working face after fracturing is lower than the advance support pressure of the working face under the unfracturing state, it indicates that the fracturing has a pressure relief effect and the fracturing effect is good.

[0074] This invention calculates damage parameters of coal and rock masses through microseismic analysis and evaluates the anti-scour effect of hydraulic fracturing by weakening formation parameters and generating random fractures to achieve water injection weakening and fracturing degradation effects. FLAC can be used to perform this method. 3D The finite difference method is used to evaluate the effectiveness of fracturing and scour prevention in high-altitude rock formations driven by a comprehensive numerical model and microseismic data. The following is a further introduction with specific examples.

[0075] The present invention was used to evaluate the fracturing and anti-scour effect of the 401106 working face in a mine in Hujiahe. The specific steps are as follows:

[0076] (1) A microseismic monitoring network is formed by using the above-ground acquisition and recording equipment and the probe installed underground in the coal mine. The vibration waves released by the mine earthquake during the working face production and roadway excavation are collected in real time at a sampling frequency of 500Hz. The mine earthquake signals fed back by each receiving channel are recorded in real time through the ground receiving unit, and the coordinates and energy of the microseismic waves are solved.

[0077] (2) A numerical model was established based on the actual coal seam characteristics and mining conditions of Hujiahe. The model size was determined to be 800m × 800m × 350m (length × width × height), with a total of 973,261 unit cells. The lithology and parameters of the coal seam and its roof and floor are shown in Table 1. The model is as follows: Figure 2 As shown.

[0078] Table 1 Mechanical parameters of coal and rock strata

[0079]

[0080] (3) Set the displacement boundary conditions of the model: First, apply horizontal constraints to each boundary of the model, that is, the horizontal displacement of the four boundaries is 0; then fix the bottom boundary of the model, that is, the horizontal and vertical displacement of the bottom boundary is 0; finally set the top of the model as a free boundary.

[0081] (4) Set the stress boundary conditions of the model: Calculate the equivalent load to be applied to the top of the model according to the formula σ=γH, where σ is the equivalent load in Pa; γ is the unit weight of the overburden, which is taken as 25kN / m³ in this case. 3 H represents the depth of the top boundary of the model, which is 550m above the Earth's surface. Therefore, in this invention, the numerical simulation applies an equivalent load of 13.75MPa to the top of the model; the gravitational acceleration is assumed to be 9.8m / s². 2 .

[0082] (5) Use the model solve command to achieve initial stress balance.

[0083] (6) The specific steps for evaluating the fracturing effect of the 401106 working face are as follows:

[0084] ① Use the matrix function to establish three matrices: the model coordinate matrix Mat_mod_coord(973261,4), the source parameter matrix Mat_seic_coord(1826,4), and the damage parameter matrix Mat_dam(973261,1). The first three columns of the model coordinate matrix Mat_mod_coord() store the coordinates of the model element, and the fourth column stores the cumulative deformation energy of the model element. The first three columns of the source parameter matrix Mat_seic_coord() store the coordinates of the microseismic generated by the fracturing, and the fourth column stores the energy of the microseismic. The damage parameter matrix Mat_dam() stores the damage parameter values ​​of the model element.

[0085] ② Traverse the entire model, use zone.pos() to get the coordinates of the model unit, and store them in the first three columns of the model coordinate matrix Mat_mod_coord().

[0086] ③ Import the microseismic coordinates and energy generated by fracturing before the 401106 working face is extracted using the `table` function and store them in the source parameter matrix `Mat_seic_coord()`. A total of 1826 microseismic events were generated during the fracturing process. The distribution diagram of the microseismic events generated during the 401106 working face extraction is shown below. Figure 3 As shown.

[0087] ④ Traverse all the unit cells and microseisms of the entire model. Using the center of the model unit cell as the center point and the ellipsoid as the region statistical window, determine whether the microseismic event is within the statistical window of the unit cell. If the microseismic event is within the statistical window of the unit cell, accumulate the deformation energy in the region to form the cumulative deformation energy of the unit cell, and store it in the fourth column of the model coordinate matrix Mat_mod_coord().

[0088] ⑤ Traverse the entire model and use the formula Calculate the damage parameter values ​​of the model unit and store them in the damage parameter matrix Mat_dam().

[0089] ⑥ Traverse the entire model, use the function zone.prop() to obtain the parameters of the unit cell, and weaken it according to the damage parameter value of each unit cell to realize water injection to weaken the formation;

[0090] ⑦ Traverse the entire model. If the damage parameter value of a unit is greater than 0.5, assign the unit to the null model to realize the fracturing and deterioration of the formation; otherwise, do not process it.

[0091] ⑧ Excavate the 401106 working face, then use the model cycle command to perform model balancing calculations, correct the numerical simulation results of the 401106 working face, and optimize its stress distribution. The simulation results of the 401106 working face before and after correction are as follows: Figure 4 and Figure 5 As shown, the stress distribution of the surrounding rock with and without fracturing is compared; by Figure 5 It can be seen that there is a clear pressure relief area after fracturing, and the advance support pressure in front of the 401106 working face has been reduced, indicating that this fracturing has a good effect on anti-impact.

[0092] This invention employs a numerical simulation method to calculate the damage parameters of the coal and rock mass through microseismic events generated during fracturing. Based on these damage parameters, the parameters of the coal and rock mass are weakened, and a null model is assigned to generate fractures. This achieves the effects of hydraulic fracturing and water injection to weaken and deteriorate the formation. The method then analyzes the stress distribution of the surrounding rock during mining after fracturing and evaluates the anti-scour effect of fracturing high-level rock formations by comparing the stress distribution with that of the surrounding rock without fracturing. The method is scientific, reliable, practical, and widely applicable.

[0093] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for evaluating the effectiveness of hydraulic fracturing and erosion prevention in high-lying rock formations driven by a comprehensive numerical model and microseismic data, characterized in that, The steps include the following: Step 1: Install a microseismic monitoring system in the area to be evaluated, including ground-mounted acquisition and recording equipment and underground probes. Use the microseismic monitoring system to acquire the seismic waveform signals induced by fracturing and solve for the source parameters. Step 2: Establish a numerical model of the area to be evaluated based on the actual coal-bearing characteristics and mining conditions; Step 3: Traverse the numerical model of the region to be evaluated and obtain the coordinates of the model unit cells; Step 4: Import the microseismic coordinates and energy generated by fracturing; Step 5: Traverse all the unit cells and microseismic events of the entire model. Using the center of the model unit cell as the center point and the ellipsoid as the region statistical window, determine whether the microseismic event is within the statistical window of the unit cell. If the microseismic event is within the statistical window of the unit cell, then accumulate the deformation energy in the region to form the cumulative deformation energy of the unit cell. Step 6: Traverse the entire model and calculate the damage parameter values ​​of the model unit. Step 7: Traverse the entire model, obtain the parameters of the unit cells, and weaken the unit cell parameters according to the damage parameter values ​​of each unit cell to achieve water injection to weaken the formation. Step 8: Traverse the entire model. If the damage parameter value of a unit is greater than 0.5, assign the unit to the null model to realize the fracturing and deterioration of the formation; otherwise, do not process it. Step 9: Excavate the working face and perform balancing calculations. Compare the stress distribution in front of the working face under the non-fracturing state to evaluate the fracturing effect.

2. The method for evaluating the effectiveness of high-altitude rock strata fracturing and erosion prevention driven by a comprehensive numerical model and microseismic data as described in claim 1, is characterized in that... In step 1, the microseismic monitoring system calculates the coordinates and energy magnitude of the microseismic events based on the seismic signals fed back from each receiving channel.

3. The method for evaluating the effectiveness of high-level rock strata fracturing and erosion prevention driven by a comprehensive numerical model and microseismic data as described in claim 1, is characterized in that... Step 2 specifically includes the following steps: a) Establish a numerical model based on the actual coal seam characteristics and mining conditions, determine the model size, and construct the lithology and parameters of the coal seam and its roof and floor. b) Set the displacement boundary conditions for the model; c) Set the stress boundary conditions for the model; d) Initial stress equilibrium.

4. The method for evaluating the anti-scour effect of high-altitude rock strata fracturing driven by a comprehensive numerical model and microseismic data as described in claim 3, is characterized in that... In step 5, the radius of the ellipsoid statistical window in the x-axis and y-axis directions is θ, and the radius in the z-axis direction is δ, where δ is greater than θ.

5. The method for evaluating the effectiveness of high-level rock strata fracturing and erosion prevention driven by a comprehensive numerical model and microseismic data as described in claim 4, is characterized in that... θ is 20m and δ is 50m.

6. The method for evaluating the anti-scour effect of high-altitude rock strata fracturing driven by a comprehensive numerical model and microseismic data as described in claim 4, is characterized in that... The cumulative deformation energy of a unit cell is calculated using the following formula: In the formula, ε Ei N is the cumulative deformation energy of unit i; i E represents the number of microseisms within the statistical window of element i ellipsoid; ij Let be the energy of the j-th microseismic event within the statistical window of unit i ellipsoid.

7. The method for evaluating the effectiveness of high-level rock strata fracturing and erosion prevention driven by a comprehensive numerical model and microseismic data as described in claim 6, is characterized in that... The damage parameter value of the unit cell is calculated using the following formula: In the formula, D i Here is the damage parameter value for unit i; ε F This represents the average cumulative deformation energy. max{ε Ei } represents the maximum cumulative deformation energy in the entire model; D C is the damage parameter value corresponding to the fully damaged state; exp is an exponential function with the natural constant e as the base.

8. The method for evaluating the anti-scour effect of high-level rock strata fracturing driven by a comprehensive numerical model and microseismic data as described in claim 7, is characterized in that... In step 7, the cohesion, tensile strength, and internal friction angle parameters of the unit are weakened.

9. The method for evaluating the effectiveness of high-altitude rock strata fracturing and erosion prevention driven by a comprehensive numerical model and microseismic data as described in claim 8, is characterized in that... In step 7, water injection is used to weaken the formation: C i =C i0 (1-D i ) s it =s it0 (1-D i ) In the formula, C i C represents the cohesion of unit i after weakening; i0 σ represents the cohesion of unit i before weakening; it σ represents the tensile strength of unit i after weakening; it0 The tensile strength of unit i before weakening; The internal friction angle of unit i after weakening; The internal friction angle of unit i before weakening.

10. A method for evaluating the effectiveness of high-altitude rock strata fracturing and erosion control driven by a comprehensive numerical model and microseismic data, as described in any one of claims 1-9, is characterized in that... Using FLAC 3D The finite difference method is used to evaluate the effectiveness of hydraulic fracturing and erosion prevention in high-altitude rock formations driven by a comprehensive numerical model and microseismic data.

Images