CN-122014215-A - Method for determining fracturing height and evaluating fracturing effect of rock burst mine composite key layer

CN122014215ACN 122014215 ACN122014215 ACN 122014215ACN-122014215-A

Abstract

The invention discloses a method for determining the fracturing height and evaluating the effect of a composite key layer of a rock burst mine, which comprises the steps of S1, determining a target layer position of the composite key layer, S2, preliminarily determining a fracturing height range based on numerical simulation by combining a crack balance expansion criterion and a microseismic distribution cooperative criterion, S3, carrying out indoor fracturing and acoustic emission experiments by preparing a sample with similar proportion through large-diameter directional drilling coring, finely calibrating and determining the optimal fracturing height according to crack penetrability and acoustic emission energy balance criterion, S4, carrying out on-site fracturing, adopting multi-angle transient electromagnetic detection, and quantitatively evaluating the fracturing effect according to multi-circle layer apparent resistivity amplitude reduction indexes. According to the invention, through multi-scale fusion and multi-source information verification, the accurate optimization of the fracturing height and the reliable evaluation of the fracturing effect are realized, and the pertinence and the effectiveness of deep mine rock burst prevention are obviously improved.

Inventors

ZHAO WENGE
LIU LEI
ZHANG YACHAO
WU XUEMING
WEI HUAZHEN
YU SHUI
LI KE
YAN BIN
ZHANG MING
ZHANG JIE

Assignees

陕西煤业股份有限公司
陕西彬长矿业集团有限公司
陕西彬长小庄矿业有限公司
中煤科工西安研究院(集团)有限公司

Dates

Publication Date: 20260512
Application Date: 20260202

Claims (9)

1. The method for determining the fracturing height and evaluating the fracturing effect of the rock burst mine composite key layer is characterized by comprising the following steps of: Step1, judging the adjacent thick and hard stratum layer at the top of the working surface meeting the single-layer thickness of more than or equal to 10m and the uniaxial compressive strength of more than or equal to 60MPa as a composite key layer target layer to be fractured according to the column-shaped distribution characteristics of coal and rock and the stratum mechanical parameters of the coal and rock at the position of the working surface; step 2, establishing a hydraulic fracturing numerical model comprising a coal bed, a coal bed top plate, a coal bed bottom plate, a composite key layer and an overlying rock layer according to the coal rock column distribution characteristics and geological conditions determined in the step 1, and primarily determining a fracturing height range H a ~H b according to a preset fracture balance expansion criterion and a microseismic distribution cooperative criterion based on the geometric form of a fracture in a simulation result and the spatial distribution of a microseismic event; Step 3, obtaining a core of the composite key layer through on-site large-diameter directional drilling, processing and preparing a standard sample containing a simulated composite key layer structure based on a similar proportion principle, carrying out hydraulic fracturing experiments of different fracturing height schemes by adjusting the positions of simulated fracturing holes in the sample, synchronously monitoring acoustic emission signals, wherein the fracturing heights in the different fracturing height schemes are all within the range of H a ~H b , and then determining an optimal fracturing height H Excellent (excellent) from the experiments according to a fracture penetrability criterion and an acoustic emission energy balance criterion; and 4, carrying out on-site hydraulic fracturing construction at the optimal fracturing height H Excellent (excellent) , respectively adopting a multi-angle transient electromagnetic detection system to detect a fracturing influence area before and after the fracturing construction, and quantitatively evaluating the fracturing transformation effect according to a preset multi-circle layer apparent resistivity amplitude reduction index by comparing and analyzing apparent resistivity data before and after the fracturing.
2. The method for determining the fracturing height and evaluating the fracturing effect of the rock burst mine complex key layer according to claim 1, wherein the rule of the crack equilibrium and expansion in the step S2 is as follows: When the crack is expanded to an upper interface or a lower interface of the composite key layer, the minimum distance H 1 between the crack expansion range and the other interface is less than or equal to 1m; The crack is expanded to the lengths L 1 、L 2 of the upper and lower layers of the composite key layer, the difference value is in the range of 5m, both L 1 and L 2 are more than or equal to 20m, the maximum width D 1 of the crack expansion is more than or equal to 45m, and the crack expansion height H 2 ≥1.1(h 1 +h 2 ),h 1 ,h 2 is the thickness of the upper and lower layers of the composite key layer respectively.
3. The method for determining the fracturing height and evaluating the fracturing effect of the composite key layer of the rock burst mine according to claim 1, wherein the microseism distribution cooperation criterion in the step S2 is that microseism sources are widely distributed in upper and lower strata of the composite key layer, and local sources are located in the upper and lower strata area of the composite key layer.
4. The method for determining the fracturing height and evaluating the fracturing effect of the rock burst mine composite key layer according to claim 1, wherein the fracture penetrability criterion in the step S3 is that the upper and lower layering interfaces of the fracture penetrating through the composite key layer sample are confirmed through a tracer, and the rock sample shows obvious penetrability damage characteristics.
5. The method for determining the fracturing height and evaluating the fracturing effect of the rock burst mine composite key layer according to claim 1, wherein the acoustic emission energy balance criterion in the step S3 is that the difference of the acoustic emission event energy release rates of unit volume is not more than 5% in an upper layer and a lower layer of the composite key layer.
6. The method for determining the fracturing height and evaluating the fracturing height of a composite key layer of a rock burst mine according to claim 1, wherein in the step S3, the inner diameter of the large-diameter directional drilling hole is not less than 200 mm, and the length of the coring section in the composite key layer is not less than 40 m.
7. The method for determining the fracturing height and evaluating the fracturing height of the composite key layer of the rock burst mine according to claim 1, wherein in the step S3, the standard sample is 150mm×150mm, and the height ratio of the simulated composite key layer portion in the sample is consistent with the thickness ratio of the upper and lower layers of the actual composite key layer.
8. The method for determining the fracturing height and evaluating the fracturing height of the composite key layer of the rock burst mine according to claim 1, wherein in the step S4, at least 3 groups of field transient electromagnetic detection are performed before and after fracturing, the detection methods before and after fracturing are consistent, and the combined detection of 9 different angles of 0.0 °, 22.5 °, 45.0 °, 67.5 °, 90.0 °, 112.5 °, 135.0 °, 157.5 ° and 180.0 ° is performed, wherein the detection direction is 0.0 ° towards the goaf side and the direction parallel to the horizontal direction of the adjacent goaf, and the detection direction is 90.0 ° with the direction parallel to the vertical direction of the roadway.
9. The method for determining the fracturing height and evaluating the effect of the composite key layer of the rock burst mine according to any one of claims 1 to 8, wherein the multi-turn layer visual resistivity reduction index in the step S4 comprises a) the height X of a region with the visual resistivity reduction exceeding 50% in the vertical direction is more than or equal to 0.9 (h 1 +h 2 ) after fracturing, wherein h 1 、h 2 is the thickness of an upper layer and a lower layer of the composite key layer respectively, b) the height Y of a region with the visual resistivity reduction exceeding 30% in the vertical direction is more than or equal to 1.1 (h1+h2) after fracturing, the difference of the covering lengths L ' 1 、L' 2 of the region on the upper layer and the lower layer of the composite key layer in the horizontal direction is in the range of 5m, and both L ' 1 and L ' 2 are more than or equal to 20m.

Description

Method for determining fracturing height and evaluating fracturing effect of rock burst mine composite key layer Technical Field The invention belongs to the technical field of mine safety and rock stratum control, and particularly relates to a method for determining the fracturing height and evaluating the fracturing effect of a rock burst mine composite key layer. Background With the development of coal resource exploitation in China to deep, a composite key layer consisting of multiple layers of thick hard rock layers is frequently formed on a coal seam roof. The rock stratum has the characteristics of high strength, large thickness, layer reason development and the like, is not easy to naturally collapse under the influence of mining, is easy to form a large-area suspended roof, accumulates a large amount of elastic energy, and further induces mine dynamic disasters such as rock burst and the like. At present, underground long-distance directional staged fracturing is a main control means for pressure relief regulation of a middle-low key layer at the top of a coal seam, if the fracturing height is set too high, the structural transformation effect on the key layer is insufficient, and if the fracturing height is set too low, the fracturing crack is easy to expand downwards to a mined coal seam, so that the safe production of a working face is influenced. However, when implementing fracturing for the composite key layer, the existing method simplifies the composite key layer into a single hard rock stratum, and the complex influence of the rock stratum thickness, lithology and interface of the composite rock stratum on a crack propagation path is not fully considered, so that the prediction distortion of the crack propagation behavior under the influence of hydraulic fracturing of the key layer is caused. Disclosure of Invention The invention aims to overcome the defects of the prior art, and provides a method for determining the fracturing height of a composite key layer of a rock burst mine and evaluating the fracturing effect, which comprises the steps of numerical simulation primary selection, indoor experimental fine correction and on-site detection verification, the accurate optimization of the fracturing height and the quantitative evaluation of the fracturing effect are realized, so that the scientificity, the reliability and the effectiveness of rock burst prevention and control engineering are improved. Therefore, the method for determining the fracturing height and evaluating the fracturing effect of the rock burst mine composite key layer provided by the invention comprises the following steps: Step1, judging the adjacent thick and hard stratum layer at the top of the working surface meeting the single-layer thickness of more than or equal to 10m and the uniaxial compressive strength of more than or equal to 60MPa as a composite key layer target layer to be fractured according to the column-shaped distribution characteristics of coal and rock and the stratum mechanical parameters of the coal and rock at the position of the working surface; step 2, establishing a hydraulic fracturing numerical model comprising a coal bed, a coal bed top plate, a coal bed bottom plate, a composite key layer and an overlying rock layer according to the coal rock column distribution characteristics and geological conditions determined in the step 1, and primarily determining a fracturing height range H a~Hb according to a preset fracture balance expansion criterion and a microseismic distribution cooperative criterion based on the geometric form of a fracture in a simulation result and the spatial distribution of a microseismic event; Step 3, obtaining a core of the composite key layer through on-site large-diameter directional drilling, processing and preparing a standard sample containing a simulated composite key layer structure based on a similar proportion principle, carrying out hydraulic fracturing experiments of different fracturing height schemes by adjusting the positions of simulated fracturing holes in the sample, synchronously monitoring acoustic emission signals, wherein the fracturing heights in the different fracturing height schemes are all within the range of H a~Hb, and then determining an optimal fracturing height H Excellent (excellent) from the experiments according to a fracture penetrability criterion and an acoustic emission energy balance criterion; and 4, carrying out on-site hydraulic fracturing construction at the optimal fracturing height H Excellent (excellent) , respectively adopting a multi-angle transient electromagnetic detection system to detect a fracturing influence area before and after the fracturing construction, and quantitatively evaluating the fracturing transformation effect according to a preset multi-circle layer apparent resistivity amplitude reduction index by comparing and analyzing apparent resistivity data before and after the fracturing. In order to ensure