A hydraulic fracturing pressure relief method for multi-layer thick hard roof of extra-thick coal seam

Abstract

The present disclosure proposes a method for hydraulic fracturing and decompression of multi-layer thick hard roof in an extra-thick coal seam, including: obtaining the rock formation of the multi-layer thick hard roof by using a roof drilling method; evaluating the stability of the multi-layer thick hard roof and identifying the target layer for fracturing in the multi-layer thick hard roof based on a rock mechanics experimental method and a roof peeping method; arranging directional drilling holes in the target layer for fracturing according to the rock formation occurrence; using abrasive jet and staged fracturing in the directional drilling holes to create cracks in the target layer for fracturing; real-time monitoring of the crack extension range of the target layer for fracturing based on a microseismic monitoring method in the hole, and dynamically adjusting the fracturing construction parameters according to the crack extension range. In the method for hydraulic fracturing and decompression of multi-layer thick hard roof in an extra-thick coal seam disclosed in the present disclosure, the rock formation test before fracturing, the determination of the key parameters of the fracturing construction and the monitoring after fracturing are used to ensure a good decompression effect of the multi-layer thick hard roof, and to achieve effective prevention and control of the strong mine pressure disaster of the multi-layer thick hard roof.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mining, and in particular to a method for hydraulic fracturing and pressure relief of multi-layer thick hard roof of an extra-thick coal seam. Background Art

[0002] After mining of extra-thick coal seams, huge goafs are formed, the overburden of the coal seam roof moves violently, and the hard roof is difficult to collapse as it is mined. After a long period of suspended roof, a sudden large-scale collapse can easily lead to strong mine pressure, rock burst, coal and gas outbursts, and cause disasters such as large-scale pressure on the working face support and large deformation of the tunnel. When there are multiple layers of thick and hard roof above the extra-thick coal seam, the mine pressure disaster of the roof is particularly severe. The problem of handling multiple layers of thick and hard roof in extra-thick coal seams and controlling strong mine pressure needs to be solved urgently.

[0003] Conventional hydraulic fracturing methods for treating hard roof in coal mines mainly solve the problem of lateral hanging roof in tunnels. It does not take into account the occurrence of multiple layers of thick hard roof strata and cannot effectively treat multiple layers of thick hard roof at high positions on the working face. There is no mature method for managing the strong mine pressure disasters caused by multiple layers of thick hard roof in extremely thick coal seams. Summary of the invention

[0004] The present disclosure aims to solve one of the technical problems in the related art at least to some extent.

[0005] To this end, the purpose of the present disclosure is to provide a method for hydraulic fracturing and decompression of multi-layer thick hard roof of extra-thick coal seams.

[0006] To achieve the above-mentioned purpose, the present disclosure provides a method for hydraulic fracturing and decompression of multiple layers of thick hard roof in an extra-thick coal seam, comprising: obtaining the stratum occurrence of the multiple layers of thick hard roof by a roof drilling method; evaluating the stability of the multiple layers of thick hard roof and identifying the target layer for fracturing in the multiple layers of thick hard roof based on a rock mechanics experimental method and a roof peeping method; arranging directional drilling holes in the target layer for fracturing according to the stratum occurrence; creating fractures in the target layer for fracturing by abrasive jet and staged fracturing in the directional drilling holes; monitoring the crack extension range of the target layer for fracturing in real time based on an in-hole microseismic monitoring method, and dynamically adjusting the fracturing construction parameters according to the crack extension range.

[0007] Optionally, the method of using the roof drilling method to obtain the rock formation occurrence of the multi-layer thick hard roof includes: arranging a plurality of detection points at intervals along the length direction of the working face tunnel; drilling and coring the multi-layer thick hard roof at the plurality of detection points along the thickness direction of the multi-layer thick hard roof; determining the thickness, inclination and dip of the rock formation in the multi-layer thick hard roof based on the rock formation distribution of the cores obtained by the plurality of drilling and coring, and obtaining the rock formation occurrence of the multi-layer thick hard roof based on the thickness, inclination and dip of the rock formation.

[0008] Optionally, the method of using the roof drilling method to obtain the rock formation status of the multi-layer thick hard roof also includes: in the working face tunnel, arranging a plurality of the detection points at preset intervals along the length direction of the working face tunnel; drilling and coring the multi-layer thick hard roof at the plurality of detection points along the thickness direction of the multi-layer thick hard roof according to a preset coring height, wherein the coring height is a first preset multiple of the mining height; drawing a plurality of roof drilling columnar diagrams according to the rock formation distribution of the plurality of cores, and drawing a rock formation profile of the multi-layer thick hard roof according to the plurality of roof drilling columnar diagrams, and determining the thickness, inclination and dip of the rock formation in the multi-layer thick hard roof according to the rock formation profile.

[0009] Optionally, the method of evaluating the stability of the multi-layer thick hard roof and identifying the fracturing target layer in the multi-layer thick hard roof based on the rock mechanics experimental method and the roof peeking method includes: collecting the in-situ compressive strength, elastic modulus and ground stress of each rock layer in the multi-layer thick hard roof based on the rock mechanics experimental method; selecting a rock layer with a thickness not less than a preset thickness, a compressive strength not less than a preset strength, an elastic modulus not less than a preset modulus and a ground stress not less than a preset stress as a potential fracturing target layer; peeking at the potential fracturing target layer and determining the in-situ fracture development section and the complete dense section of the potential fracturing target layer; and using the complete dense section as the area for arranging the directional drilling in the fracturing target layer.

[0010] Optionally, the rock mechanics experimental method-based method for collecting the in-situ compressive strength, elastic modulus and geostress of each rock layer in the multi-layer thick hard roof includes: using downhole geophysical logging methods to perform lithology detection and geostress testing, and obtaining the natural potential, natural gamma, resistivity and geostress profile curves of each rock layer in the multi-layer thick hard roof based on the lithology detection and the geostress testing; using a surrounding rock in-situ strength tester to test the in-situ compressive strength of each rock layer in the multi-layer thick hard roof; performing uniaxial experiments on the cores obtained by drilling and coring, and determining the elastic modulus of each rock layer in the multi-layer thick hard roof based on the uniaxial experiments.

[0011] Optionally, the method also includes: dividing the multi-layer thick hard roof into a periodic pressure zone roof and a primary mining zone roof; for the periodic pressure zone roof and the primary mining zone roof, arranging directional drilling holes in the fracturing target layer according to the rock formation occurrence includes: drilling multiple sections of directional long holes to the fracturing target layer in the multi-layer thick hard roof in the working face tunnel, and after the directional long holes are drilled from the low-position roof to the fracturing target layer, the directional long holes are arranged along the inclination of the fracturing target layer, and the directional long holes are located at half the thickness of the fracturing target layer; for the primary mining zone roof, arranging directional drilling holes in the fracturing target layer according to the rock formation occurrence also includes: drilling directional short holes through each of the fracturing target layers at different inclination angles at the cutting position.

[0012] Optionally, the use of abrasive jet and staged fracturing in the directional drilling to create seams in the fracturing target layer includes: forming a plurality of slits in the directional drilling hole by an abrasive jet slitting method; dividing the plurality of slits in the directional drilling hole into an odd array and an even array, wherein the plurality of slits in the odd array and the plurality of slits in the even array are distributed at intervals along the direction from the bottom of the directional drilling hole to the orifice; sequentially sealing and hydraulically fracturing the plurality of slits in the odd array along the direction from the bottom of the directional drilling hole to the orifice; and sequentially sealing and hydraulically fracturing the plurality of slits in the even array along the direction from the bottom of the directional drilling hole to the orifice.

[0013] Optionally, the use of abrasive jet and staged fracturing in the directional drilling to create seams in the fracturing target layer also includes: setting a fracturing sequence; wherein, for multiple fracturing target layers in the thickness direction of the multi-layer thick hard top plate, the fracturing sequence is: first fracturing the middle fracturing target layer, and then fracturing the upper and lower fracturing target layers; for multiple directional drill holes in the fracturing target layer, the fracturing sequence is: first fracturing the fracturing target layer in the middle directional drill hole, and then fracturing the fracturing target layer in the directional drill holes on both sides.

[0014] Optionally, the real-time monitoring of the crack extension range of the fracturing target layer based on the in-hole microseismic monitoring method, and dynamically adjusting the fracturing construction parameters according to the crack extension range include: drilling a monitoring hole parallel to the directional drilling hole; arranging a three-component detector in the monitoring hole, and the dwelling position of the detector follows the fracturing position of the directional drilling hole; real-time monitoring of the wellhead pressure at a preset frequency, and obtaining a wellhead pressure curve using a waveform transformation analysis method; marking microseismic visible events in the directional drilling fracturing process in the pressure curve; quantitatively analyzing the distribution of microseismic visible events in different fracturing stages, and conducting real-time evaluation of multi-source data on crack extension effects to invert the crack extension range of the fracturing target layer; dynamically adjusting the segmented distance of the fracturing, the displacement of the fracturing and the duration of the fracturing according to the crack extension range.

[0015] Optionally, the method also includes: evaluating the fracturing effect by using the working face mining field mine pressure manifestation evaluation index and the roof breaking activity energy evaluation index, wherein the working face mining field mine pressure manifestation evaluation index includes: periodic pressure step index, dynamic load coefficient index, safety valve opening rate index and mining height index, and the roof breaking activity energy evaluation index includes: fourth power or above large energy event density index and roof breaking energy index per meter advancement; when the working face mining field mine pressure manifestation evaluation index and the roof breaking activity energy evaluation index do not reach the expected value, increasing the fracturing layer, increasing the fracturing drilling density, and extending the fracturing time; when the working face mining field mine pressure manifestation evaluation index and the roof breaking activity energy evaluation index reach the expected value, reducing the fracturing layer, reducing the fracturing drilling density, and shortening the fracturing time.

[0016] The technical solution provided by the present disclosure may have the following beneficial effects:

[0017] The orientation of directional drilling is determined based on the rock formation of the multi-layer thick hard roof, ensuring the rationality of the arrangement of the pressure relief drilling holes; the stability of the multi-layer thick hard roof is evaluated based on the rock mechanics experimental method and the roof peeping method, and the target layer of fracturing in the multi-layer thick hard roof is identified, ensuring the scientific nature of the target layer of fracturing; the use of abrasive jet and staged fracturing to create cracks ensures the controllability of the crack extension direction, which is conducive to enhancing the degree of fracturing transformation of the multi-layer thick hard roof; based on the microseismic monitoring method in the hole, the crack extension range of the target layer of fracturing is monitored in real time, which improves the monitoring accuracy of the crack distribution, and supports the dynamic adjustment of the fracturing construction parameters, reducing the insufficient and unbalanced degree of fracturing of the multi-layer thick hard roof. As a result, a complete hydraulic fracturing pressure relief method for multi-layer thick hard roof is formed, which uses the rock formation test before fracturing, the determination of the key parameters of fracturing construction and the monitoring after fracturing to ensure the good pressure relief effect of the multi-layer thick hard roof, and realizes the effective prevention and control of the strong mine pressure disaster of the multi-layer thick hard roof.

[0018] Additional aspects and advantages of the present disclosure will be given in part in the following description and in part will be obvious from the following description or learned through practice of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and / or additional aspects and advantages of the present disclosure will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0020] Figure 1 It is a schematic flow chart of a method for hydraulic fracturing and decompression of multi-layer thick hard roof of an extra-thick coal seam proposed in an embodiment of the present disclosure;

[0021] Figure 2 It is a cross-sectional view of a rock layer of a multi-layer thick hard roof in a method for hydraulic fracturing and decompression of a multi-layer thick hard roof in an extra-thick coal seam proposed in an embodiment of the present disclosure;

[0022] Figure 3 This is a structural diagram of drilling directional long holes in a hydraulic fracturing and pressure relief method for multi-layer thick hard roof of an extra-thick coal seam proposed in an embodiment of the present disclosure;

[0023] Figure 4 This is a structural diagram of drilling directional short holes in a method for hydraulic fracturing and pressure relief of multi-layer thick hard roof of an extra-thick coal seam proposed in an embodiment of the present disclosure;

[0024] Figure 5 It is a structural diagram of the slits in the hydraulic fracturing and pressure relief method for multi-layer thick hard roof of an extra-thick coal seam proposed in one embodiment of the present disclosure;

[0025] Figure 6 It is a fracturing structure diagram of directional drilling in a hydraulic fracturing pressure relief method for multi-layer thick hard roof of an extra-thick coal seam proposed in an embodiment of the present disclosure;

[0026] Figure 7 This is a structural diagram of the drilling of monitoring holes in a hydraulic fracturing and pressure relief method for multi-layer thick hard roof of an extra-thick coal seam proposed in an embodiment of the present disclosure;

[0027] Figure 8 It is a flow chart of the evaluation of the hydraulic fracturing pressure relief effect in the method for hydraulic fracturing pressure relief of multi-layer thick hard roof of extra-thick coal seam proposed in one embodiment of the present disclosure;

[0028] As shown in the figure: 1. Fracturing target layer;

[0029] 2. Directional drilling, 21. Directional long hole, 22. Directional short hole;

[0030] 3. Slit, 31, odd number, 32, even number;

[0031] 4. Monitoring hole. DETAILED DESCRIPTION

[0032] Embodiments of the present disclosure are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present disclosure, and are not to be construed as limitations of the present disclosure. On the contrary, the embodiments of the present disclosure include all changes, modifications, and equivalents that fall within the spirit and connotation of the appended claims.

[0033] like Figure 1 As shown, the embodiment of the present disclosure provides a method for hydraulic fracturing and pressure relief of multi-layer thick hard roof of an extra-thick coal seam, comprising:

[0034] S1: The rock formation occurrence of multiple layers of thick hard roof is obtained by roof drilling method;

[0035] S2: Evaluate the stability of multi-layer thick hard roof based on rock mechanics experimental method and roof peeping method and identify the target layer for fracturing in multi-layer thick hard roof 1;

[0036] S3: Arrange directional drilling holes 2 in the target layer 1 for fracturing according to the occurrence of the rock formation;

[0037] S4: using abrasive jet and staged fracturing to create fractures in the fracturing target layer 1 in the directional drilling hole 2;

[0038] S5: Based on the in-hole microseismic monitoring method, the crack extension range of the fracturing target layer 1 is monitored in real time, and the fracturing construction parameters are dynamically adjusted according to the crack extension range.

[0039] It can be understood that the orientation of the directional drilling 2 is determined based on the rock formation occurrence of the multi-layer thick hard roof, which ensures the rationality of the pressure relief drilling arrangement; the stability of the multi-layer thick hard roof is evaluated based on the rock mechanics experimental method and the roof peeping method, and the fracturing target layer 1 in the multi-layer thick hard roof is identified, which ensures the scientific nature of the fracturing target layer 1; the abrasive jet and staged fracturing are used to create cracks, which ensures the controllability of the crack expansion direction, which is conducive to enhancing the degree of fracturing transformation of the multi-layer thick hard roof; based on the in-hole microseismic monitoring method, the crack expansion range of the fracturing target layer 1 is monitored in real time, which improves the monitoring accuracy of the crack distribution, and supports the dynamic adjustment of the fracturing construction parameters, which reduces the insufficient and unbalanced fracturing of the multi-layer thick hard roof.

[0040] Thus, a complete hydraulic fracturing pressure relief method for multi-layer thick hard roof was formed. By utilizing rock formation testing before fracturing, determination of key parameters of fracturing construction and monitoring after fracturing, a better pressure relief effect of multi-layer thick hard roof was ensured, and effective prevention and control of strong mining pressure disasters of multi-layer thick hard roof was achieved.

[0041] In some embodiments, the rock formation occurrence of multiple layers of thick hard roof is obtained by using the roof drilling method, including:

[0042] S11: multiple detection points are arranged at intervals along the length direction of the working face tunnel;

[0043] S12: drilling and coring the multi-layer thick hard top plate at multiple detection points along the thickness direction of the multi-layer thick hard top plate;

[0044] S13: Determine the thickness, dip and inclination of the rock layers in the multi-layer thick hard roof according to the rock layer distribution of the cores obtained by coring multiple holes, and obtain the rock layer occurrence of the multi-layer thick hard roof according to the thickness, dip and inclination of the rock layers.

[0045] It can be understood that drilling and coring are carried out at multiple detection points of the multi-layer thick hard roof plates along the thickness direction of the multi-layer thick hard roof plates, and the thickness, inclination and dip of the rock strata in the multi-layer thick hard roof plates are determined based on the rock strata distribution of the obtained cores, so as to obtain the rock strata occurrence of the multi-layer thick hard roof plates based on the thickness, inclination and dip of the rock strata, and then determine the orientation of the directional drilling hole 2 based on the rock strata occurrence of the multi-layer thick hard roof plates, so as to ensure the rationality of the pressure relief drilling hole arrangement.

[0046] like Figure 2 As shown, in some embodiments, obtaining the rock formation occurrence of multiple layers of thick hard roof using the roof drilling method also includes:

[0047] S111: In the working face tunnel, a plurality of detection points are arranged at preset intervals along the length direction of the working face tunnel;

[0048] S121: drilling and coring the multi-layer thick hard roof plate at a plurality of detection points along the thickness direction of the multi-layer thick hard roof plate according to a preset coring height, wherein the coring height is a first preset multiple of the mining height;

[0049] S131: Draw a plurality of top plate drilling columnar diagrams according to the rock layer distribution of the plurality of cores, draw a rock layer profile diagram of the multi-layer thick hard top plate according to the plurality of top plate drilling columnar diagrams, and determine the thickness, dip and inclination of the rock layer in the multi-layer thick hard top plate according to the rock layer profile diagram.

[0050] It can be understood that multiple detection points are arranged at preset intervals along the length direction of the working face tunnel, and the multiple thick hard roof plates are drilled and cored at multiple detection points along the thickness direction of the multiple thick hard roof plates according to preset coring heights, so as to achieve comprehensive and accurate detection of the multiple thick hard roof plates, and a roof drilling columnar diagram is drawn according to the rock layer distribution of the core, and a rock layer profile of the multiple thick hard roof plates is drawn according to multiple roof drilling columnar diagrams, so that the thickness, inclination and dip of the rock layers in the multiple thick hard roof plates can be determined according to the rock layer profile diagram, and the rock layer occurrence of the multiple thick hard roof plates can be accurately obtained.

[0051] It should be noted that the specific location of the detection point can be set according to actual needs and there is no restriction on this. For example, the preset spacing between adjacent detection points can be 500m, that is, along the length direction of the working face tunnel, a vertical drill hole is drilled into the multi-layer thick hard roof every 500m for coring.

[0052] The coring height can be set according to actual needs and there is no limitation on this. For example, the first preset multiple can range from 8 times to 10 times, that is, coring of multiple layers of thick hard roof plates is carried out at 8 times to 10 times the mining height.

[0053] Among them, by drilling and coring the detection points of the multi-layer thick hard roof, the rock layer structure at the detection point can be obtained according to the rock layer distribution of the core, and by drawing graphics between the rock layer structures of adjacent detection points (drawing connecting lines between the same rock layers, etc.), the thickness, dip and inclination of each rock layer in the multi-layer thick hard roof can be obtained.

[0054] In some embodiments, evaluating the stability of a multi-layer thick hard roof plate and identifying a fracturing target layer 1 in the multi-layer thick hard roof plate based on a rock mechanics experimental method and a roof peeking method includes:

[0055] S21: Collect in-situ compressive strength, elastic modulus and geostress of each rock layer in a multi-layer thick hard roof based on rock mechanics experimental methods;

[0056] S22: selecting a rock formation with a thickness not less than a preset thickness, a compressive strength not less than a preset strength, an elastic modulus not less than a preset modulus, and a ground stress not less than a preset stress as a potential fracturing target layer;

[0057] S23: Peep into the potential target layer for fracturing and determine the fracture development section and complete tight section of the potential target layer for fracturing;

[0058] S24: The complete dense section is used as the area for arranging the directional drilling hole 2 in the fracturing target layer 1.

[0059] It can be understood that the in-situ compressive strength, elastic modulus and geostress of each rock layer in the multi-layer thick hard roof are collected based on the rock mechanics experimental method, and the potential fracturing target layer is selected according to the thickness, compressive strength, elastic modulus and geostress of each rock layer, and the in-situ fracture development section and complete dense section of the potential fracturing target layer are determined based on the roof peeking method, and the complete dense section is used as the area for arranging directional drilling holes 2 in the fracturing target layer 1, thereby realizing the accurate and scientific arrangement of directional drilling holes 2, and then ensuring the safe and efficient pressure relief of the multi-layer thick hard roof.

[0060] It should be noted that the rock formation thickness is obtained in step S1, and the preset thickness can be set according to actual needs without limitation. For example, the preset thickness can be 5 m, that is, a rock formation with a thickness ≥ 5 m can be used as a potential fracturing target layer.

[0061] The in-situ compressive strength can be obtained using downhole geophysical logging methods, and the preset strength can be set according to actual needs without limitation. For example, the preset strength can be 50 MPa, that is, rock formations with a compressive strength ≥ 50 MPa can be used as potential fracturing target layers.

[0062] The elastic modulus can be obtained using an in-situ strength tester for surrounding rock. The preset modulus can be set according to actual needs without limitation. For example, the preset modulus can be 10 GPa, that is, rock formations with an elastic modulus ≥ 10 GPa can be used as potential fracturing target layers.

[0063] The in-situ stress can be obtained by uniaxial test, and the preset stress can be set according to actual needs without restriction. Based on the introduction of preset stress, it can also be understood that the rock layer with high in-situ stress level can be used as a potential fracturing target layer.

[0064] The potential fracturing target layer is divided into a fissure development section and a complete dense section. The fissure development section and the complete dense section can be determined by using the roof peeping method. The specific implementation of the roof peeping method can be set according to actual needs and is not limited to this. For example, a coal mine underground borehole television peeping instrument can be used to peek at the potential fracturing target layer.

[0065] The fracture development section refers to the area where fractures are more obvious in the rock. These fractures may be caused by a variety of factors, including rock properties, tectonic stress, climate change, etc. In the geological process, these factors work together to make the rock weather and cause water dissolution and geological structure changes, which ultimately lead to the formation of cracks.

[0066] The complete dense section refers to the area where the cracks in the rock are not obviously developed and the rock structure is relatively complete and dense. These rocks usually have higher strength and stability.

[0067] In some embodiments, collecting the in-situ compressive strength, elastic modulus and geostress of each rock layer in the multi-layer thick hard roof based on the rock mechanics experimental method includes:

[0068] S211: Use downhole geophysical logging methods to conduct lithology detection and geostress testing, and obtain the natural potential, natural gamma, resistivity and geostress profile curves of each rock layer in the multi-layer thick hard roof based on the lithology detection and geostress testing;

[0069] S212: The in-situ compressive strength of each rock layer in the multi-layer thick hard roof is tested using the surrounding rock in-situ strength tester;

[0070] S213: Performing a uniaxial test on the core obtained by coring the borehole, and determining the elastic modulus of each rock layer in the multi-layer thick hard roof according to the uniaxial test.

[0071] It can be understood that downhole geophysical logging methods are used to carry out lithology detection and geostress testing, and the natural potential, natural gamma, resistivity and geostress profile curves of each rock layer in the multi-layer thick hard roof are obtained based on the lithology detection and geostress testing, so as to comprehensively interpret and screen the lithologically stable layers based on the natural potential, natural gamma, resistivity and geostress profile curves of each rock layer.

[0072] The in-situ strength tester of surrounding rock is used to test the in-situ compressive strength of each rock layer in the multi-layer thick hard roof, so as to accurately screen the potential fracturing target layer in the multi-layer thick hard roof according to the in-situ compressive strength.

[0073] The cores obtained by drilling and coring are subjected to uniaxial experiments, and the elastic modulus of each rock layer in the multi-layer thick hard roof is determined based on the uniaxial experiment, so that the potential fracturing target layer in the multi-layer thick hard roof can be accurately screened out based on the elastic modulus.

[0074] It should be noted that the downhole geophysical logging method is a technology that applies geophysical principles to measure various physical parameters of rock formations along the drilling profile through special instruments, thereby studying geological profiles and solving underground geological problems. The specific implementation method of the downhole geophysical logging method can be set according to actual needs and is not limited to this.

[0075] The surrounding rock in-situ strength tester is a device specially used to measure the in-situ strength of surrounding rock. The surrounding rock in-situ strength tester is mainly used to measure the strength parameters of surrounding rock such as coal rock in the in-situ state, such as compressive strength, tensile strength, elastic modulus, etc. The specific type of the surrounding rock in-situ strength tester can be set according to actual needs and there is no restriction on this.

[0076] The uniaxial test, also known as the unidirectional compression test or uniaxial compression test, is an experimental method that tests the physical and mechanical properties of a sample by applying a unidirectional stress perpendicular to the axis of the sample. The experimental principle is based on the basic principles of material mechanics. By measuring the deformation and stress changes of the sample during the compression process, the mechanical parameters of the material, such as compression strength, elastic modulus, Poisson's ratio, etc., can be calculated. The specific implementation method of the uniaxial test can be set according to actual needs and is not limited to this. For example, the core is processed according to the "International Rock Mechanics Test Standard" for rock mechanics parameters, and a uniaxial experiment is carried out in the laboratory to determine the elastic modulus of rocks in different layers.

[0077] like Figure 3 and Figure 4 As shown, in some embodiments, the method further includes: dividing the multi-layer thick hard roof into a periodic pressure area roof and a primary mining area roof.

[0078] For the top plate of the periodic fracturing area and the top plate of the primary mining area, arranging the directional drilling holes 2 in the fracturing target layer 1 according to the occurrence of the rock formation includes:

[0079] S31: Drill multiple sections of directional long holes 21 into the fracturing target layer 1 in the multi-layer thick hard roof in the working face tunnel, and after the directional long holes 21 are drilled from the low roof to the fracturing target layer 1, the directional long holes 21 are arranged along the inclination of the fracturing target layer 1, and the directional long holes 21 are located at half the thickness of the fracturing target layer 1.

[0080] For the roof of the primary mining area, arranging directional drilling holes 2 in the fracturing target layer 1 according to the occurrence of the rock formation also includes:

[0081] S32: Drilling directional short holes 22 through each fracturing target layer 1 at different inclination angles at the cutting position.

[0082] It can be understood that the multi-layer thick hard roof is divided into the roof of the periodic pressure zone and the roof of the primary mining area. For the roof of the periodic pressure zone, a drilling arrangement scheme combining long drill holes along the bedding direction and long drill holes along the bedding inclination is adopted to ensure that there are no large-area drilling and fracturing blind areas in the rock stratum where the drill holes are located. For the roof of the primary mining area, not only long drill holes along the bedding inclination should be arranged in the fracturing target layer 1, but also short holes that penetrate the layers should be drilled to different fracturing target layers 1 at the opening position of the cutting eye, thereby reducing the difficulty of collapse of the roof of the primary mining area.

[0083] It should be noted that, in the working face tunnel, multiple sections of directional long holes 21 are drilled toward the fracturing target layer 1 in the multi-layer thick hard roof, and after the directional long holes 21 are drilled from the low roof to the fracturing target layer 1, the directional long holes 21 are arranged along the inclination of the fracturing target layer 1, thereby realizing a drilling arrangement scheme combining long holes along the layer strike and long holes along the layer inclination. The specific implementation method of the directional long holes 21 can be set according to actual needs, and there is no limitation to this. For example, the drilling site is arranged in the working face tunnel. , a coal mine full hydraulic tunnel directional drilling rig is used to drill multiple layers of directional long holes 21 into the target layer 1 of the multi-layer thick hard roof fracturing. After the directional long hole 21 enters the target layer 1 of the fracturing from the low roof, it immediately turns to drill along the inclination of the target layer 1 of the fracturing. The inclination angle of the directional long hole 21 along the layer drilling section is approximately the inclination angle of the fracturing target layer 1. The position of the directional long hole 21 in this fracturing is close to the middle position of the fracturing thickness. At the same time, the directional long hole 21 should be arranged in the complete dense section to avoid drilling into the section with crack development. In this way, it is ensured that the directional long hole 21 along the layer drilling section is in the thick hard roof rock layer and in the dense section, creating good fracturing conditions for the next step of the whole layer of thick hard roof staged fracturing.

[0084] The number of layers of the directional long holes 21 is determined according to the number of the fracturing target layers 1, and the number of the through-layer directional short holes 22 is determined according to the length of the working surface and the crack extension range.

[0085] The length of the directional long hole 21 along the layer drilling section can range from 500m to 1000m; the drilling length of the directional short hole 22 can range from 50m to 100m.

[0086] The periodic compression zone is an area formed by the periodic fracture or collapse of the old roof rock layer after the working face advances to a certain stage in coal mining.

[0087] The primary mining area is the initial stage of coal mining, that is, the area from the start of mining from the opening of the cutting eye to before the first large-scale fall of the old roof.

[0088] like Figure 5 and Figure 6 As shown, in some embodiments, using abrasive jet and staged fracturing to create fractures in the fracturing target layer 1 in the directional drilling 2 includes:

[0089] S41: forming a plurality of slits 3 in the directional drill hole 2 by using an abrasive jet slit 3 method;

[0090] S42: Divide the plurality of slits 3 in the directional drilling hole 2 into an odd number group 31 and an even number group 32, wherein the plurality of slits 3 in the odd number group 31 and the plurality of slits 3 in the even number group 32 are distributed at intervals along a direction from the bottom of the directional drilling hole 2 to the hole mouth;

[0091] S43: Sequentially seal the plurality of slits 3 of the hydraulic fracturing odd-numbered array 31 along the direction from the bottom of the directional drilling hole 2 to the hole mouth;

[0092] S44: Separating the plurality of slits 3 of the hydraulic fracturing even array 32 in sequence from the bottom of the directional drilling hole 2 to the hole mouth.

[0093] It can be understood that a plurality of slits 3 are formed in the directional borehole 2 by the abrasive jet slit 3 method, so that the slits 3 are used to induce the hydraulic fractures to expand along the direction of the slits 3, and after the jet slit 3 is completed, the plurality of slits 3 of the hydraulic fracturing odd array 31 are successively sealed along the direction from the bottom of the directional borehole 2 to the hole mouth, and the plurality of slits 3 of the hydraulic fracturing even array 32 are successively sealed along the direction from the bottom of the directional borehole 2 to the hole mouth, so that the hydraulic fracturing of the fracturing target layer 1 is achieved by the backward staged fracturing method, and the odd-even interval fracturing method can also avoid the problem of hydraulic fracturing stress shadow effect interfering with the expansion of adjacent cracks due to too small segment distance.

[0094] It should be noted that the abrasive jet slitting method 3 refers to adding a certain amount of abrasive particles to a pure water jet at a relatively low working pressure, thereby greatly improving the cutting ability of the water jet. The basic principle is to use a high-speed water jet as an energy carrier, increase the water pressure to a high-pressure state through a supercharger, and spray the high-pressure water through a special nozzle at a very high speed. During the spraying process, abrasive particles are mixed into the water jet to form a liquid-solid mixed abrasive water jet. When the abrasive water jet contacts the material to be cut, its kinetic energy is instantly absorbed by the material, resulting in impact, shearing and breaking (cutting) and erosion, thereby achieving slitting 3.

[0095] Isolator hydraulic fracturing uses a surface high-pressure pump group to inject fracturing fluid into a directional borehole 2 at a displacement rate that greatly exceeds the absorption capacity of the formation, thereby creating high pressure in the directional borehole 2 and exceeding the formation closure stress of the fracturing target layer 1 and the tensile strength of the rock, causing the fracturing target layer 1 to rupture and form cracks.

[0096] The method of this embodiment uses abrasive jet and staged fracturing as a joint forming process. First, abrasive jet slitting 3 technology is used to form a slit 3 inside the directional drill hole 2 (the depth of the slit 3 can range from 1m to 2m). High-pressure water jet and abrasive particles are used to impact the rock at high speed to produce a cutting effect to form a slit 3 of a certain size. Quartz sand is generally used as abrasive.

[0097] After the jet cutting 3 is completed, a double-seal single-card packer is used to seal the staged fracturing at the position of the cutting 3. Among them, the staged fracturing spacing should be coordinated with the periodic pressure step distance of the working face, and the staged fracturing spacing range can be 1-1.5 times the periodic pressure step distance.

[0098] During the isolation staged hydraulic fracturing process, the fracturing fluid used in the staged fracturing should be determined according to the lithology of the fracturing target layer 1. High viscosity fracturing fluid (≥10mpa•s) can be used to reduce liquid loss and improve the fracture effect.

[0099] As a further example of the backward odd-even interval segmented fracturing method, the first segment of the odd array 31 is fractured from the bottom of the directional borehole 2, and then the packer is dragged backward to fractur the second segment of the odd array 31, and so on, until all the fracturing segments of the odd array 31 are completed, and then the first segment of the even array 32 is fractured, and the packer is dragged backward to fractur the second segment of the even array 32, and so on, until all the segmented fracturing and seaming are completed.

[0100] In some embodiments, the method of using abrasive jet and staged fracturing to create fractures in the fracturing target layer 1 in the directional drilling 2 further includes: S40: setting a fracturing sequence. For multiple fracturing target layers 1 in the thickness direction of the multi-layer thick hard roof, the fracturing sequence is:

[0101] S401: Fracturing the target layer 1 in the middle of the fracturing;

[0102] S402: Fracturing the upper and lower fracturing target layers 1.

[0103] For multiple directional drill holes 2 in the target layer 1 for fracturing, the fracturing sequence is:

[0104] S4001: Fracturing the target layer 1 in the directional drill hole 2 in the middle;

[0105] S4002: Fracturing the target layer 1 in the directional drill holes 2 on both sides.

[0106] It can be understood that, for multiple fracturing target layers 1 in the thickness direction of the multi-layer thick hard top plate, the fracturing target layer 1 in the middle is firstly fractured, and then the fracturing target layers 1 in the upper and lower parts are fractured, which can avoid the interference of cracks caused by the close distance between the drilling groups, thereby ensuring the efficient and safe seam making of the multi-layer thick hard top plate.

[0107] For multiple directional boreholes 2 in the target fracturing layer 1, the target fracturing layer 1 is firstly fractured in the middle directional borehole 2, and then the target fracturing layer 1 is fractured in the directional boreholes 2 on both sides, which can avoid the interference of cracks caused by the close distance between the borehole groups, thereby ensuring efficient and safe fracturing of the target fracturing layer 1.

[0108] It should be noted that multiple fracturing target layers 1 are distributed in the thickness direction of the multi-layer thick hard top plate, and the adjacent fracturing target layers 1 can be divided into a middle fracturing target layer 1, an upper fracturing target layer 1 and a lower fracturing target layer 1, and the multiple directional drill holes 2 in the fracturing target layer 1 are distributed in the plane direction of the fracturing target layer 1, and the adjacent directional drill holes 2 can be divided into a middle directional drill hole 2 and directional drill holes 2 on both sides.

[0109] like Figure 7 As shown, in some embodiments, real-time monitoring of the crack extension range of the fracturing target layer 1 based on the microseismic monitoring method in the hole and dynamically adjusting the fracturing operation parameters according to the crack extension range include:

[0110] S51: Drilling a monitoring hole 4 parallel to the directional drilling hole 2;

[0111] S52: arranging a three-component geophone in the monitoring hole, and the staying position of the geophone follows the fracturing position of the directional drilling hole 2;

[0112] S53: monitoring the wellhead pressure in real time at a preset frequency, and obtaining a wellhead pressure curve using a waveform transformation analysis method;

[0113] S54: marking visible microseismic events during the fracturing process of directional drilling 2 on the pressure curve;

[0114] S55: Quantitatively analyze the distribution of visible microseismic events at different fracturing stages, and conduct real-time evaluation of multi-source data on the effect of fracture extension to invert the fracture extension range of the fracturing target layer 1;

[0115] S56: Dynamically adjust the segment distance, fracturing volume and fracturing duration according to the crack expansion range.

[0116] It can be understood that a monitoring hole 4 is drilled parallel to the directional drilling hole 2, and a three-component detector is arranged in the monitoring hole to realize microseismic monitoring in the hole by using the three-component detector. At the same time, the wellhead pressure is monitored in real time at a preset frequency to realize high-frequency monitoring of the wellhead pressure. Thus, by using microseismic monitoring in the hole and high-frequency monitoring of the wellhead pressure, a higher monitoring accuracy of the crack distribution can be achieved.

[0117] In addition, the visible microseismic events during the fracturing process of directional drilling 2 are marked in the pressure curve, and the distribution of visible microseismic events in different fracturing stages is quantitatively analyzed, and real-time evaluation of multi-source data on the crack extension effect is carried out to invert the crack extension range of the fracturing target layer 1, and then dynamically adjust the fracturing segment distance, fracturing displacement and fracturing duration according to the crack extension range, thereby reducing the insufficient and unbalanced fracturing of multiple layers of thick hard roof.

[0118] It should be noted that the microseismic monitoring method in the hole is used for real-time monitoring of fracturing cracks. The specific implementation method can be set according to actual needs and is not limited to this. For example, a monitoring hole 4 parallel to the fracturing directional drilling hole 2 is drilled using a directional drilling rig in a coal mine. A three-component detector is lowered into the adjacent monitoring hole 4. The detector is brought into the drilling section along the layer of the borehole by a crawler. The detector moves its docking position as the fracturing section changes, thereby improving the monitoring effect and positioning accuracy.

[0119] Real-time high-frequency monitoring (frequency ≥ 1000 Hz) of the wellhead pressure is performed, wherein the waveform transformation analysis method is used to perform energy analysis on the wellhead pressure curve, and the energy peak characteristics can map the competitive fracturing stage of multiple fractures.

[0120] like Figure 8 As shown, in some embodiments, the method further includes:

[0121] S61: The fracturing effect is evaluated by using the working face mining field pressure manifestation evaluation index and the roof breaking activity energy evaluation index, wherein the working face mining field pressure manifestation evaluation index includes: periodic pressure step index, dynamic load coefficient index, safety valve opening rate index and mining height index, and the roof breaking activity energy evaluation index includes: the density index of large energy events above the fourth power and the roof breaking energy index per meter of advancement;

[0122] S62: When the working face mining area mining pressure manifestation evaluation index and the roof fracture activity energy evaluation index do not reach the expected value, increase the fracturing layer, increase the fracturing drilling density, and extend the fracturing time;

[0123] S63: When the working face mining area mine pressure manifestation evaluation index and the roof fracture activity energy evaluation index reach the expected value, reduce the fracturing layer, reduce the fracturing drilling density, and shorten the fracturing time.

[0124] It can be understood that when the periodic pressure step index, dynamic load coefficient index, safety valve opening rate index and mining height index, as well as the fourth-power or above large energy event density index and the roof breaking energy index per meter of advancement do not reach the expected values, the fracturing layers are increased, the fracturing drilling density is increased, and the fracturing time is extended; when the periodic pressure step index, dynamic load coefficient index, safety valve opening rate index and mining height index, as well as the fourth-power or above large energy event density index and the roof breaking energy index per meter of advancement all reach the expected values, the fracturing layers are reduced, the fracturing drilling density is reduced, and the fracturing time is shortened.

[0125] Therefore, according to the evaluation results of fracturing pressure relief effect, the fracturing parameters can be adjusted by feedback, thereby realizing the comprehensive index fracturing pressure relief effect evaluation process, which can scientifically and effectively evaluate the pressure relief effect of multiple layers of thick hard roof in extra-thick coal seams, and then achieve the optimization of treatment technology effect and economic benefits.

[0126] It should be noted that when the working face mining pressure manifestation evaluation indicators such as the periodic pressure step index, dynamic load coefficient index, safety valve opening rate index, mining height index, and the roof breaking activity energy evaluation indicators such as the fourth power or above large energy event density index and the roof breaking energy index per meter of advancement do not reach the expected values, it indicates that the intensity of governance needs to be improved. Therefore, measures such as increasing the fracturing layer, increasing the fracturing drilling density, and extending the fracturing time are implemented.

[0127] When the working face mining pressure manifestation evaluation indicators such as the periodic pressure step index, dynamic load coefficient index, safety valve opening rate index, mining height index, and the roof breaking activity energy evaluation indicators such as the fourth power or above large energy event density index and the roof breaking energy per meter advancement index all reach the expected values, it indicates that the economic efficiency of governance needs to be improved. Therefore, measures such as reducing the fracturing layer, reducing the fracturing drilling density, and shortening the fracturing time are implemented.

[0128] In the description of the present disclosure, the terms "first", "second", etc. are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. In addition, in the description of the present disclosure, unless otherwise specified, "plurality" means two or more.

[0129] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present disclosure includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present disclosure belong.

[0130] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0131] Although the embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present disclosure. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present disclosure.

Claims

1. A method for hydraulic fracturing and pressure relief of multi-layer thick hard roof of extra-thick coal seam, characterized in that: include: The rock formation occurrence of the multi-layer thick hard roof is obtained by using a roof drilling method; Based on rock mechanics experimental methods and roof peeping methods, the stability of the multi-layer thick hard roof is evaluated and the target layer for fracturing in the multi-layer thick hard roof is identified; Arranging directional drilling in the fracturing target layer according to the occurrence of the rock formation; In the directional drilling, abrasive jet and staged fracturing are used to create fractures in the fracturing target layer; Based on the in-hole microseismic monitoring method, real-time monitoring of the crack extension range of the fracturing target layer is performed, and the fracturing operation parameters are dynamically adjusted according to the crack extension range; The method of using the roof drilling method to obtain the rock formation occurrence of the multi-layer thick hard roof includes: arranging a plurality of detection points at intervals along the length direction of the working face tunnel; drilling and coring the multi-layer thick hard roof at the plurality of detection points along the thickness direction of the multi-layer thick hard roof; determining the thickness, dip and inclination of the rock formation in the multi-layer thick hard roof according to the rock formation distribution of the cores obtained from the plurality of drilling and coring, and obtaining the rock formation occurrence of the multi-layer thick hard roof according to the thickness, dip and inclination of the rock formation; The method of evaluating the stability of the multi-layer thick hard roof plate and identifying the target layer for fracturing in the multi-layer thick hard roof plate based on the rock mechanics experimental method and the roof peeping method includes: collecting the in-situ compressive strength, elastic modulus and ground stress of each rock layer in the multi-layer thick hard roof plate based on the rock mechanics experimental method; selecting a rock layer with a thickness not less than a preset thickness, a compressive strength not less than a preset strength, an elastic modulus not less than a preset modulus and a ground stress not less than a preset stress as a potential target layer for fracturing; peeping at the potential target layer for fracturing, and determining the fissure development section and the complete dense section of the potential target layer for fracturing; and using the complete dense section as the area for arranging the directional drilling in the target layer for fracturing; The rock mechanics experimental method based on which the in-situ compressive strength, elastic modulus and geostress of each rock layer in the multi-layer thick hard roof are collected includes: using downhole geophysical logging methods to perform lithology detection and geostress testing, and obtaining the natural potential, natural gamma, resistivity and geostress profile curve of each rock layer in the multi-layer thick hard roof based on the lithology detection and the geostress testing; using a surrounding rock in-situ strength tester to test the in-situ compressive strength of each rock layer in the multi-layer thick hard roof; performing uniaxial experiments on the cores obtained by coring, and determining the elastic modulus of each rock layer in the multi-layer thick hard roof based on the uniaxial experiments.

2. The method for hydraulic fracturing and pressure relief of multi-layer thick hard roof of extra-thick coal seam according to claim 1, characterized in that: The method of using the roof drilling method to obtain the rock formation occurrence of the multi-layer thick hard roof also includes: In the working face tunnel, a plurality of the detection points are arranged at preset intervals along the length direction of the working face tunnel; Drilling and coring the multi-layer thick hard top plate at a plurality of the detection points along the thickness direction of the multi-layer thick hard top plate according to a preset coring height, wherein the coring height is a mining height of a first preset multiple; A plurality of top plate drilling columnar diagrams are drawn according to the stratum distribution of the plurality of cores, and a stratum profile diagram of the multi-layer thick hard top plate is drawn according to the plurality of top plate drilling columnar diagrams, and the thickness, dip and inclination of the stratum in the multi-layer thick hard top plate are determined according to the stratum profile diagram.

3. The method for hydraulic fracturing and pressure relief of multi-layer thick hard roof of extra-thick coal seam according to claim 1, characterized in that: The method further comprises: Dividing the multi-layer thick hard roof into a periodic pressure area roof and a primary mining area roof; For the roof of the periodic pressure area and the roof of the primary mining area, the directional drilling in the target fracturing layer according to the occurrence of the rock formation includes: drilling multiple sections of directional long holes to the target fracturing layer in the multi-layer thick hard roof in the working face tunnel, and after the directional long holes are drilled from the low roof to the target fracturing layer, the directional long holes are arranged along the inclination of the target fracturing layer, and the directional long holes are located at half the thickness of the target fracturing layer; For the roof of the primary mining area, arranging directional drilling holes in the fracturing target layer according to the occurrence of the rock formation also includes: drilling directional short holes penetrating each of the fracturing target layers at different inclination angles at the cutting position.

4. The method for hydraulic fracturing and pressure relief of multi-layer thick hard roof of extra-thick coal seam according to claim 1, characterized in that: The method of using abrasive jet and staged fracturing in the directional drilling to create fractures in the fracturing target layer comprises: A plurality of slits are formed in the directional drill hole by using an abrasive jet slit method; Dividing the plurality of slits in the directional drilling hole into an odd number group and an even number group, wherein the plurality of slits in the odd number group and the plurality of slits in the even number group are distributed at intervals along the direction from the bottom of the directional drilling hole to the hole mouth; Sequentially sealing and hydraulically fracturing the odd-numbered array of the plurality of slits along the direction from the bottom of the directional drilling hole to the hole mouth; The plurality of slits in the even number array are sequentially sealed and hydraulically fractured along the direction from the bottom of the directional drilling hole to the hole mouth.

5. The method for hydraulic fracturing and pressure relief of multi-layer thick hard roof of extra-thick coal seam according to claim 1, characterized in that: The method of using abrasive jet and staged fracturing in the directional drilling to create fractures in the fracturing target layer also includes: Set the fracturing sequence; Wherein, for the multiple fracturing target layers in the thickness direction of the multi-layer thick hard top plate, the fracturing sequence is: first fracturing the fracturing target layer in the middle, and then fracturing the fracturing target layers in the upper and lower parts; For the multiple directional drill holes in the fracturing target layer, the fracturing sequence is: firstly fracturing the fracturing target layer in the directional drill hole in the middle, and then fracturing the fracturing target layer in the directional drill holes on both sides.

6. The method for hydraulic fracturing and pressure relief of multi-layer thick hard roof of extra-thick coal seam according to claim 1, characterized in that: The method of real-time monitoring the crack extension range of the fracturing target layer based on the microseismic monitoring method in the hole, and dynamically adjusting the fracturing operation parameters according to the crack extension range includes: Drilling a monitoring hole parallel to the directional drilling hole; Arranging a three-component geophone in the monitoring hole, and the staying position of the geophone follows the fracturing position of the directional drilling hole; The wellhead pressure is monitored in real time at a preset frequency, and the wellhead pressure curve is obtained using the waveform transformation analysis method; marking visible microseismic events during the directional drilling and fracturing process in the pressure curve; Quantitatively analyze the distribution of visible microseismic events at different fracturing stages, and conduct real-time evaluation of multi-source data on the effect of fracture extension to invert the fracture extension range of the fracturing target layer; The segment distance of the fracturing, the displacement of the fracturing and the duration of the fracturing are dynamically adjusted according to the extension range of the crack.

7. The method for hydraulic fracturing and pressure relief of multi-layer thick hard roof of extra-thick coal seam according to claim 1, characterized in that: The method further comprises: The fracturing effect is evaluated by using the working face mining field mine pressure manifestation evaluation index and the roof breaking activity energy evaluation index, wherein the working face mining field mine pressure manifestation evaluation index includes: periodic pressure step index, dynamic load coefficient index, safety valve opening rate index and mining height index, and the roof breaking activity energy evaluation index includes: the density index of large energy events of the fourth power or more and the roof breaking energy index per meter of advancement; When the working face mining field mine pressure manifestation evaluation index and the roof fracture activity energy evaluation index do not reach the expected value, increase the fracturing layer, increase the fracturing drilling density, and extend the fracturing time; When the working face mining field mine pressure manifestation evaluation index and the roof fracture activity energy evaluation index reach the expected value, the fracturing layer is reduced, the fracturing drilling density is reduced, and the fracturing time is shortened.

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