Deep thick hard rock stratum roof directional long drill hole staged fracturing weakening method and system

Abstract

The invention discloses a deep thick and hard rock stratum roof directional long drill hole staged fracturing weakening method and system, and relates to the technical field of coal mining. The method comprises the following steps: determining a fracturing target horizon according to mining area geological data and to-be-treated working face monitoring data; a drill site construction position is determined, and drilling track parameters are determined in the fracturing target horizon; a fracturing assembly is installed, fracturing construction parameters are determined, and the operation sequence of drilling construction and fracturing construction is determined; and drilling construction is conducted according to the operation sequence, fracturing construction is conducted through the fracturing assembly, and the stability condition of the roadway is monitored in the whole process and before and after. The technical scheme aims at weakening far-field strong stress of a top plate of a thick and hard coal rock stratum overlying a deep coal mine underground roadway, and is particularly suitable for design of a directional long drilling hole fracturing weakening scheme in the field of deep thick and hard rock stratum top plate pressure relief and roadway protection engineering. And the roadway deformation condition under the disturbance influence of advanced high supporting stress and mining strong stress of the working face is improved.

Description

Technical Field

[0001] The invention relates to the technical field of coal mining, and in particular to a method and system for directional long drilling of staged fracturing and weakening of a roof of a deep thick hard rock layer. Background Art

[0002] As the working face is recovered to the final stage, the ground pressure disturbance caused by mining activities will change the stress state of the tunnel surrounding rock. With the high load of the working face's advanced support stress, the large tunnel will produce roof collapse, deformation of the two sides, bottom drum and other adverse phenomena. In severe cases, it will also cause dangerous accidents such as large deformation and even collapse of the tunnel, seriously affecting the safe production and operation of the coal mine. The directional long-hole hydraulic fracturing technology can effectively control this dangerous situation and reduce the cost of tunnel support. The directional long-hole hydraulic fracturing technology is a complete set of underground directional long-distance drilling facilities, that is, using a kilometer-long directional drilling rig equipped with wired or wireless drilling measurement technology, which can provide real-time feedback during drilling, adjust and control the drill bit azimuth to achieve high-precision drilling and long-distance stable drilling, and realize the fracturing design trajectory for regional hydraulic fracturing engineering operation technology. The drilling length is usually more than 300m, and the fracturing range can cover the entire working face area or even wider, which can avoid the shortcomings of conventional hydraulic fracturing in terms of fracturing depth, fracturing layer, and fracturing effect.

[0003] At present, the application of this technology in roof pressure relief and control projects mainly refers to the construction experience of gas control projects to design and arrange key parameters such as drilling construction layer, drilling trajectory, and fracturing duration. It lacks applicability for regional fracturing and pressure relief tunnel protection projects on the roof of deep thick hard coal rock formations. In addition, unlike the coal seams in most gas control projects, the rock formations have greater strength and complex mechanical response characteristics, and have more requirements for the design of fracturing parameters. Summary of the invention

[0004] In order to solve the above problems, the technical solution of the present invention proposes a method and system for directional long drilling segmented fracturing weakening of the roof of deep thick hard rock formations. It is aimed at the far-field strong stress weakening of the roof of thick hard coal rock formations overlying deep underground coal mine tunnels. It is particularly suitable for the design of directional long drilling fracturing weakening schemes in the field of pressure relief and tunnel protection engineering for the roof of deep thick hard rock formations, and improves the deformation of tunnels under the influence of advanced high support stress of the working face and strong stress disturbance caused by mining.

[0005] According to a first aspect of the present invention, a method for weakening the roof of a deep thick hard rock layer by directional long drilling in stages is provided, wherein the method comprises:

[0006] S1: Determine the target layer for fracturing based on the geological data of the mining area and the monitoring data of the working face to be treated;

[0007] S2: Determine the drilling site construction location and determine the drilling trajectory parameters in the fracturing target layer;

[0008] S3: Install the fracturing components, determine the fracturing construction parameters, and determine the operation sequence of drilling construction and fracturing construction;

[0009] S4: According to the drilling trajectory parameters and the fracturing construction parameters, drilling construction is performed at the construction location of the drilling site in accordance with the operation sequence, and fracturing construction is performed through a fracturing assembly, and the stability of the tunnel is monitored throughout the entire process and before and after.

[0010] Furthermore, the S1 specifically includes:

[0011] S11: Collect geological data of the mining area and monitoring data of the working face to be treated;

[0012] S12: Determine the height of the fracture water conduction zone according to the geological data of the mining area and the monitoring data of the working face to be treated;

[0013] S13: According to the height of the fracture water-conducting zone, combined with the microseismic monitoring data and the acoustic emission monitoring data, the range of the upper three zones of the working face to be treated is determined, which are the caving zone, the fracture zone and the curved subsidence zone from bottom to top; wherein the target stratum for fracturing is located in the fracture zone and the curved subsidence zone.

[0014] Furthermore, in S11, the geological data of the mining area and the monitoring data of the working face to be treated include: the drilling column chart of the coal rock strata overlying the working face to be treated, the lithology, hydrogeological conditions, cumulative mining thickness, mining area planning and design data, and the microseismic monitoring data of the working face to be treated, the acoustic emission monitoring data of the working face to be treated, and the tunnel deformation monitoring data.

[0015] Further, in S12, the height of the fracture water conduction zone is determined by the following formula:

[0016] When the rock type is hard, the following formula is used:

[0017]

[0018] When the lithology is medium-hard, the following formula is used:

[0019]

[0020] Among them, H Li1 and H Li2 It represents the theoretical data of the fracture zone, in m; ∑M is the cumulative mining thickness.

[0021] Furthermore, in S13, the distance between each of the target fracturing layers is at least 10 m.

[0022] Furthermore, at least one directional long drill hole is arranged in the fracture zone and the curved subsidence zone.

[0023] Furthermore, the S2 specifically includes:

[0024] S21: Arranging the drilling site construction location in the adjacent working face tunnel of the working face to be treated according to the mining area planning and design data;

[0025] S22: Determine drilling trajectory parameters in the target fracturing layer, including: the number of directional long boreholes, the position of directional long boreholes, the length of the casing section, the length of the deflection section, the length of the stabilizing section, and the range of the inclination angle of the directional long boreholes.

[0026] Furthermore, in S21, the drilling site construction position is arranged near the extension line of the stop-mining line of the working face to be treated.

[0027] Further, in S22, the number and positions of the directional long drilling holes are determined by:

[0028] According to the scope of the upper three zones of the working face to be treated, at least two directional long drill holes are arranged for the thick hard rock strata existing in the upper three zones, among which the low-position directional long drill hole is arranged in the thick hard rock strata more than 10m away from the mined coal seam; the spacing between directional long drill holes is at least 10m, and the drilling trajectory avoids faults, voids, and fold areas and is 2-5m away from the boreholes involved in gas extraction and geological exploration.

[0029] Further, in S22, the length of the sleeve section, the length of the deflection section, and the length of the deflection stabilization section are determined by the following method:

[0030] The drilling trajectory of directional long drilling is divided into three parts, among which:

[0031] The first part is the sleeve section, and the length of the sleeve section ranges from about 9 to 15 meters;

[0032] The second part is the deflection section, which ends when the horizontal projection length of the directional long borehole does not enter the working face to be treated;

[0033] The third part is the inclination stabilizing section, the length of which = the total length of the directional long borehole - the length of the sleeve section - the length of the inclination creating section.

[0034] Furthermore, the total length of the directional long borehole is the length starting from the drilling site in the adjacent working face tunnel, passing through the adjacent working face, the tunnel between the working faces, the working face to be treated and crossing the tunnel on the other side of the working face to be treated.

[0035] Furthermore, in S22, the inclination angle of the directional long drilling hole does not exceed 0.75°.

[0036] Furthermore, in S3, the fracturing components are, from front to back, a deflector, a one-way valve, a first isolation capsule, a first tubular string, a flow interceptor, a second tubular string, a second isolation capsule, a third tubular string, and a safety release; wherein the number of tubular strings between the first isolation capsule and the second isolation capsule is variable.

[0037] Here, the deflector can ensure the smooth advancement of the fracturing assembly. When the fracturing assembly is flowing with water, when the water flows through the pipe string to the isolation capsule, it will absorb water and expand. When it is transmitted to the interceptor, when the water pressure is low, it will continue to flow to the next component. When the water flows to the second isolation capsule, it will absorb water and expand, so that a closed area is formed between the two capsules. When the water flow is transmitted to the one-way valve, it will be blocked, causing the water pressure in the pipe string to increase. At this time, when the water pressure reaches a certain level, the interceptor will discharge water, gradually filling the closed area, and continuously increasing the pressure to achieve the fracturing effect. After the structural improvement, when the fracturing assembly is stuck and cannot be withdrawn, the safety release can be disconnected by reversing the drilling rig, and the previous components can be discarded to preserve the pipe string. The number of pipe strings between the isolation capsules can be increased to adjust the length of the fracturing area to achieve the effect of precise fracturing.

[0038] Furthermore, in S3, the fracturing construction parameters include fracturing section length, fracturing section spacing, fracturing area, and fracturing time.

[0039] Furthermore, the method for determining the fracturing construction parameters includes:

[0040] The fracturing section length is the length between two isolation capsules in the fracturing assembly;

[0041] The spacing between fracturing stages is adjusted by the number of exiting tubing strings, ranging from 15-30m;

[0042] The fracturing area is determined according to the hydrogeological conditions, the drilling trajectory of the directional long borehole and the drilling slag conditions: avoiding faults, cavities, fold areas and mudstone areas, with a drilling distance of more than 15m from the fracture zone, and arranged in the stable inclination section of the directional long borehole, covering the entire working surface to be treated;

[0043] The fracturing time is determined based on the pressure drop curve and the orifice drainage: after the fracturing construction starts, when the pressure drop curve is stable for more than 5 minutes or there are more than 3 pressure drop changes or the pressure indication reaches 70% of the pressure limit of the fracturing string or the orifice drainage is equivalent to the water output of the pump group, the fracturing operation is stopped.

[0044] Here, by comparing and analyzing the hydrogeological data with the directional long drilling trajectory, we can know whether there are special structural areas and other in-service boreholes around the borehole. The slag discharge during drilling refers to the rock slag discharged when the drill bit moves forward during drilling. Through sampling observation and indoor identification, it can be determined whether this is a sandstone area with fracturing conditions, rather than a loose coal or mudstone section.

[0045] Further, the drilling slag condition is determined by the following method:

[0046] Determine the formation inclination of the target layer for fracturing according to the drilling column diagram of the coal and rock layer overlying the working face to be treated, the hydrogeological conditions or the mining area planning and design data;

[0047] The drill rod inclination is fixed to the formation inclination of the target fracturing layer for straight drilling, and the drilling slag discharge during the process is recorded.

[0048] Furthermore, in S3, the operation sequence of the drilling construction and the fracturing construction is:

[0049] The construction is carried out from top to bottom according to the height of the designed position of the directional long drilling hole. After the construction of one directional long drilling hole is completed, a segmented hydraulic fracturing will be started immediately, and then the next directional long drilling hole construction will be carried out; after the overall fracturing of the drilling hole is completed, the low-level directional long drilling hole construction will be carried out until the lowest-level directional long drilling hole construction and fracturing are completed.

[0050] Furthermore, in S4, before and after construction and during fracturing, the displacement changes of the tunnel to be protected, the stress conditions of the top and bottom plates, the anchor cables on both sides, and the overall deformation and damage of the surrounding rock are monitored in real time, and the data changes before and after the overall fracturing construction of each directional long borehole are analyzed. The stability of the tunnel is confirmed based on the tunnel deformation monitoring data, and it is determined whether to adjust the number and position of the directional long boreholes.

[0051] According to a second aspect of the present invention, a system for directional long drilling and segmented fracturing and weakening of the roof of a deep thick hard rock formation is provided, the system comprising: a processor and a memory for storing executable instructions; wherein the processor is configured to execute the executable instructions to perform the method for directional long drilling and segmented fracturing and weakening of the roof of a deep thick hard rock formation as described in any of the above aspects.

[0052] According to a third aspect of the present invention, there is provided a computer-readable storage medium, wherein a computer program is stored thereon, and when the computer program is executed by a processor, the method for directional long drilling segmented fracturing weakening of the top plate of a deep thick hard rock formation as described in any of the above aspects is implemented.

[0053] Beneficial effects of the present invention:

[0054] 1. The directional long-bore hydraulic fracturing segmented weakening method mentioned in the present invention can effectively improve the damage of the strong disturbance stress of mining and the high support pressure of the working face to the main tunnels in the mining area, effectively promote the normal collapse of the thick hard rock layer roof on the working face during the mining process, accelerate the migration of overburden rock, reduce the impact of dynamic pressure manifestation, effectively cut off the stress transmission path of the thick hard rock layer, form a broken rock or crack buffer area, relieve the surrounding rock support pressure of the main tunnels in the mining area, reduce the tunnel maintenance cost, and extend the service life of the main tunnels.

[0055] 2. Using the drilling and fracturing construction arrangement method mentioned in the present invention, the weakening construction of the thick hard rock layer roof can be carried out without affecting the normal recovery of the working face of the target mining area, preventing high-power equipment from running in a cluster, not occupying production time and space, and effectively identifying the fracturing area, so that hydraulic fracturing can achieve better results. Using the drilling trajectory design method mentioned in the present invention, it can be ensured that the drilling rod and the pipe string are not easily stuck when being sent back, thereby improving the utilization rate of the drilling hole.

[0056] 3. The present invention optimizes the structure of commonly used fracturing components, and can adjust the length of the fracturing section according to actual needs. Drilling and fracturing construction are carried out alternately, that is, the "one hole, one fracturing" operation sequence can avoid the inter-hole influence caused by the conventional drilling before fracturing, including hole collapse, water seepage, slow pressure start, and the difficulty in pushing the fracturing component due to the deformation of the hole wall caused by the spatial and temporal disturbance of mining. It optimizes the construction process of conventional long-borehole hydraulic fracturing and improves construction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0058] Figure 1 A flow chart of a method for arranging directional long drilling holes for coordinated fracturing of composite roof of deep coal seam according to an embodiment of the technical solution of the present invention is shown;

[0059] Figure 2 A schematic diagram showing a drilling trajectory design according to an embodiment of the technical solution of the present invention;

[0060] Figure 3 A schematic diagram of the structure of a fracturing assembly according to an embodiment of the technical solution of the present invention is shown;

[0061] Figure 4 A plan view showing the layout of a drilling site and a drilling trajectory design according to an embodiment of the technical solution of the present invention;

[0062] Figure 5 A cross-sectional view showing the overall drilling trajectory and fracturing area design according to one embodiment of the technical solution of the present invention;

[0063] Figure 6 The figure shows the comparison of the displacement changes of the top and bottom plates of the untreated tunnel and the top and bottom plates treated according to the technical solution of the present invention.

[0064] The reference numerals are described as follows:

[0065] 1-directional long drilling sleeve section; 2-directional long drilling deflection section; 3-directional long drilling deflection stabilizing section; 4-deflector; 5-check valve; 6-packing capsule; 7-pipe string; 8-interceptor; 9-safety release. The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0066] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0067] The terms "first", "second", etc. in the specification and claims of the present disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged where appropriate, so that the embodiments of the present disclosure described herein can be implemented in an order other than those illustrated or described herein, for example.

[0068] In addition, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus that includes a series of steps or elements is not necessarily limited to those steps or elements explicitly listed, but may include other steps or elements not explicitly listed or inherent to such process, method, product, or apparatus.

[0069] Multiple includes two or more.

[0070] It should be understood that the term "and / or" used in this disclosure is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone.

[0071] The technical solution of the present invention provides a method and system for weakening the roof of a deep thick hard rock layer by directional long drilling and segmented fracturing. The method for weakening the roof of a thick hard rock layer overlying the working face by directional long drilling and hydraulic fracturing can reduce the influence of ground pressure disturbance and strong advanced support stress on the stability of the large tunnel during the recovery of the working face. Specifically, the relevant geological survey data of the mining area are collected, and a drilling site is set up at the adjacent working face. The main control layer of the disaster is analyzed through the relevant theory of the mining area stress field and the relevant monitoring data of the mining area to establish a fracturing geological model, design the drilling trajectory and number, and use a kilometer-long directional drilling rig to perform precise drilling and drilling, and one hole and one fracturing are carried out in succession. , by optimizing the structure of the fracturing components, the fracturing effect of the fracturing section is improved and the probability of hole collapse is reduced. During the fracturing process, the duration of each fracturing section is adjusted according to the water output of the borehole and the indication of the pumping pressure monitoring meter, and the fracturing section is arranged according to the slag discharge of the borehole. Through hydraulic fracturing, a multi-level honeycomb fracture network area is formed around the sealed volume space in the hole, which is mainly composed of high-pressure fracturing cracks, supplemented by secondary extensions and natural fractures to communicate cracks and fracturing joints, weakening the strength of the rock formation, reducing the impact of high stress disturbance in the mining area on the stress state of the tunnel surrounding rock, achieving a stable and safe production effect of the tunnel during mining, and extending the service life of the large tunnel.

[0072] Specifically, the technical solution of the present invention first provides a method for weakening the top plate of a deep thick hard rock layer by directional long drilling, wherein, Figure 1 As shown, the specific implementation steps are as follows:

[0073] S101: Collect geological data of the mining area and monitoring data of the working face to determine the fracturing layer.

[0074] Before construction begins, relevant geological data of the mining area to be treated are collected, including drill column diagrams of the coal and rock strata overlying the working face, lithology, hydrogeological conditions, cumulative mining thickness, mining area planning and design, as well as data such as microseismic monitoring of the working face, acoustic emission monitoring, and tunnel deformation monitoring.

[0075] According to the lithology of the coal strata in the mining area to be treated and the cumulative mining thickness ∑M in the above collected data, the height range of the upper three zones is calculated, among which the theoretical calculation formula for the height range of the fracture water conduction zone is as follows:

[0076] When the rock type is hard, the following formula is used:

[0077]

[0078] When the lithology is medium-hard, the following formula is used:

[0079]

[0080] Among them, H Li1 and H Li2 It represents the theoretical data of the fracture zone, in units of m; ∑M is the cumulative mining thickness in the actual geological data collected in the mining area.

[0081] After the calculation is completed, the most reasonable fracture zone range in the above two calculation formulas is determined by combining the microseismic monitoring data and the acoustic emission monitoring data, so as to determine the range of the upper three zones of the working face of the mining area to be treated, which are the caving zone, fracture zone and curved subsidence zone from bottom to top.

[0082] By collecting the drilling column data of the coal and rock strata overlying the working face to be treated and the physical and mechanical properties of each rock stratum, multiple thick hard rock strata more than 10m away from the mined coal seam are selected as the target strata for directional long drilling hydraulic fracturing, and the spacing between each target stratum is at least 10m. In order to ensure a better fracturing weakening effect, at least one borehole needs to be arranged within the fracture zone and the curved subsidence zone.

[0083] S102: Determine the drilling site construction location according to the working face to be treated and design drilling trajectory parameters in the target fracturing layer.

[0084] According to the design data of relevant rules of the mining area collected in S101, the drilling site is arranged in the tunnel of the adjacent working face of the working face to be treated, so as to facilitate the transportation of relevant machinery and equipment and the management of construction personnel, and avoid mutual influence with mining construction. The specific location of the drilling site is arranged near the extension line of the stop mining line of the working face to be treated.

[0085] The drilling trajectory parameter design includes: the number of holes, the location of the holes, the length of the sleeve section, the length of the deflection section, the length of the steady-inclination section and the inclination angle of the holes. According to the calculation results of S101, at least two long boreholes are arranged for the thick and hard rock layers in the upper three zones. The low-position boreholes need to be arranged in the thick and hard rock layers more than 10m above the coal seam to be mined, and the borehole spacing is at least 10m. The drilling trajectory should avoid special structural areas and be 2-5m away from other gas extraction, geological exploration and other boreholes. The directional long borehole is divided into three parts, wherein the first part is the directional long borehole sleeve section 1, which is about 15m long, and the blowout prevention device is connected to this section and the borehole mouth is reinforced. The second part is the directional long borehole deflection section 2, which is the key part to ensure that the borehole can reach the target layer. During the drilling operation, the inclination change of each drill rod shall not exceed 0.75°. The third part is the directional long borehole inclination stabilization section 3. According to the formation inclination of the target layer collected in S101, the drill rod inclination is fixed to the inclination for straight drilling, and the drilling slag situation in the process is recorded to keep the borehole in the center of the target layer. In addition, the inclination section must be ended when the horizontal projection length of the borehole has not entered the target working face. The transition between the inclination section and the stable inclination section must be smooth. During drilling and rod withdrawal, multiple flushing and slag removal are performed to ensure a good environment in the hole, and the hole wall is intact and free of debris. The drilling trajectory is horizontal and perpendicular to the mining direction of the working face, starting from the drilling site in the adjacent working face lane, passing through the adjacent working face, the lane between working faces, the target working face and crossing the lane on the other side of the target working face. The overall construction profile is shown in the figure. Figure 2 shown.

[0086] S103: Install fracturing components, design fracturing construction parameters and operation sequence.

[0087] Before the fracturing operation, the fracturing components are assembled and debugged. The components from front to back are the guide bevel 4, the one-way valve 5, the isolation capsule 6, the pipe string 7, the interceptor 8, the pipe string 7, the isolation capsule 6, the pipe string 7, and the safety release 9. Figure 3 As shown, this part is the fracturing assembly required to form the fracturing space and perform fracturing operations. Later, you only need to connect a certain number of pipes and use the drilling rig to deliver the fracturing assembly to the target fracturing area, and connect the fracturing pump group to the end of the pipe on the drilling rig.

[0088] The design of hydraulic fracturing construction parameters includes the length of the fracturing section, the spacing of the fracturing sections, the fracturing area, and the time; the fracturing method is backward staged hydraulic fracturing, and after each fracturing is completed, the drill rig withdraws the pipe string to carry out the next stage of hydraulic fracturing operation; the length of the fracturing section is the length between the two isolation capsules in the fracturing assembly, which should be changed according to the physical and mechanical properties of the target layer rock collected in step (1), and can be adjusted by increasing or decreasing the number of pipe strings. The spacing of the fracturing sections is adjusted by the number of withdrawn pipe strings, which is generally 15-30m. The fracturing area is designed according to the geological data of the target working face collected in S101 and the drilling trajectory and slag discharge conditions in S102, and should avoid special structural areas and mudstone areas. The distance from the fracture zone drilling hole should be more than 15m, and it should be arranged in the stable slope section of the drilling trajectory, which can cover the entire target working face and weaken the thick hard rock layer above the target working face in sections to achieve the pressure relief treatment effect. The fracturing time is adjusted according to the pressure drop curve and orifice drainage recorded by the instrument on the fracturing pump group. After the fracturing construction starts, when the pressure drop curve is stable for a long time of more than 5 minutes or there are more than 3 pressure drop changes or the pressure indication reaches 70% of the pressure limit of the fracturing string or the orifice drainage is equivalent to the water output of the pump group, the fracturing operation is stopped, the pressure relief operation is performed and the fracturing pump group is turned off. When the pressure indication of the pump group instrument reaches zero, the connection between the pump group and the tubing on the drilling rig is disconnected, the tubing is withdrawn, and the second stage of fracturing construction is started. The same fracturing operation is repeated until the construction of the entire fracturing design area of ​​the borehole is completed.

[0089] The drilling construction operation sequence is carried out from top to bottom according to the height of the designed drilling position. After one drilling construction is completed, a segmented hydraulic fracturing will be started immediately. After the overall fracturing of the drilling hole is completed, the low-level drilling construction will be carried out until the lowest drilling construction and fracturing are completed. Through the directional long drilling hydraulic fracturing technology, multiple thick and hard rock layers above the target working face are weakened to reduce their strength and structural stability, forming multiple honeycomb-shaped broken areas and fracture networks, cutting off the transmission path of strong mining stress in the thick and hard rock layers, reducing the impact of far-field dynamic load changes in the mining area on the target protection tunnel, and improving the stability of the target protection tunnel.

[0090] S104: Construction and monitoring of the tunnel stability during the entire process and before and after.

[0091] Before, during and after the construction and during the fracturing, the displacement changes of the tunnel to be protected, the stress conditions of the top and bottom plates, the anchor cables on both sides, and the overall deformation and damage of the surrounding rock are monitored in real time. The data changes before and after the overall fracturing construction of each borehole are analyzed in detail, and whether the number and location of boreholes should be adjusted is determined based on the stability of the tunnel.

[0092] The technical solution of the present invention also provides a system for directional long drilling and segmented fracturing and weakening of the roof of a deep thick hard rock formation, the system comprising: a processor and a memory for storing executable instructions; wherein the processor is configured to execute the executable instructions to execute the method for directional long drilling and segmented fracturing and weakening of the roof of a deep thick hard rock formation as described in any of the above aspects.

[0093] The technical solution of the present invention further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the method for directional long drilling and segmented fracturing weakening of the top plate of a deep thick hard rock layer as described in any of the above aspects is implemented.

[0094] Example

[0095] The 4306 working face of Shaqu No. 2 Coal Mine is the sixth 4# coal working face of the three mining areas. The northeast is the eroded coal-free area, the southeast is the 4307 working face, the northwest is the 4305 goaf, and the southwest is the concentrated tunnel of the three mining areas. The working face has a dip length of 225m to 245m, a strike length of 235m, and an area of ​​55225m2. The stop mining line is close to the concentrated track tunnel and the return air tunnel of the three mining areas. After the mining of the working face is completed, the advance support pressure and the residual support pressure are transmitted to the coal pillar between the working face and the main tunnel, which can easily cause deformation and bottom drum in the main tunnel of the mining area. In order to eliminate the above influences, the technical solution proposed in the present invention is adopted to carry out directional long drilling hydraulic fracturing and segmented weakening and pressure relief construction on the roof of the hard rock stratum overlying the top near the stop mining line of the 4306 working face. The specific steps are as follows:

[0096] The relevant geological data, tunnel displacement and microseismic monitoring data near the 4306 working face in the third mining area were collected, and the thickness of the coal seam mined by the working face was found to be 2.09m. The overlying rock layer contains multiple sandstone layers, which are medium-hard rock layers. The theoretical formula in step 1 was used for calculation, and the location of the area with more energy events and higher energy levels in the microseismic monitoring data was combined. Finally, the water-conducting fracture zone of the working face was found to be 7.25-30.10m. The number and strike angle of the thick hard rock layers in the upper three zones were analyzed through the borehole histograms at different positions of the working face, and the fracture zone and the bending zone were analyzed. Directional long-hole hydraulic fracturing construction is carried out on the three thick and hard rock formations in the sinking zone; secondly, according to step 2, the fracturing drilling site is arranged in the 4307 working face track inclined tunnel that has not been mined yet, with a horizontal distance of 40m from the 4306 stop mining line, close to one side of the concentrated track tunnel; among the three determined fracturing target strata, the 1# drilling fracturing section is located 13m above the coal seam roof, the 2# drilling fracturing section is located 32m above the coal seam roof, and the 3# drilling fracturing section is located 50m above the coal seam roof. The fracturing targets are all rock formations, and the stable inclination sections are located in the middle of the thick and hard rock formations. Figure 4 Design a plan for the drilling site layout and the drilling trajectory of hole 2#, Figure 5 It is the design profile diagram of the overall drilling trajectory and fracturing area; the sealing section of each directional long borehole is 12m long, and the inclination section is about 160m long. They all enter the stable inclination section before the drilling trajectory reaches the 4306 belt lane. Considering that there is a fracture zone borehole below the 1# borehole, it first climbs to 18m above the coal seam roof during the drilling process, and then descends to 13m above the coal seam roof after crossing the fracture zone borehole. A protection zone is set around the fracture zone borehole. The length of the fracturing area is about 110m. The fracturing areas of the remaining boreholes are designed in the stable inclination section with a length of 265m, which can completely cover the entire 4306 working face.

[0097] First, the construction of 3# borehole is carried out. After the construction is completed, the fracturing components are assembled when the rod is withdrawn, and the threads are tightened in the order of step 3. After the rod is withdrawn, it is sent into the borehole by the drilling rig. After it is sent to the fracturing area, the fracturing pump group is connected to the last pipe string on the drilling rig with a high-pressure hose, the pump group is turned on and the changes in the indications of the pressure instrument are observed. When the three situations described in step 3 achieve the fracturing effect, the pump group is turned off. After the pressure indication is 0 and the machine runs stably, 8 pipe strings are pulled out, and the fracturing operation of the next area is carried out. The relevant data is recorded until the fracturing operation of the entire designed fracturing area is completed, the 3# borehole is sealed and the construction of the 2# borehole is started. The above operations are repeated until the construction and fracturing operations of all boreholes are completed.

[0098] According to the content in step 4, the displacement changes of the concentrated track lanes in the three mining areas, the stress conditions of the top and bottom plates, the anchor cables on both sides, and the overall deformation and damage of the surrounding rock were collected before and after fracturing. The data showed that during the construction and fracturing operation, the displacement changes of the concentrated track lanes in the three mining areas increased at a relatively fast rate at the beginning, and then the rising rate began to decrease. In the later period, the daily displacement changes gradually became gentle, all kept within 100mm, and the highest was 94mm. Figure 6 As shown, compared with other working faces that did not use the technical solution of the present invention for weakening management during mining, the deformation of the large tunnel has been improved, and the displacement change has decreased by about 20% year-on-year. In addition, the top and bottom plates and the surrounding rocks on both sides of the track tunnel in the third mining area are relatively stable as a whole during mining, and only small-scale gravel falling and anchor cable deformation occur in individual areas, which reduces the support and maintenance costs, effectively alleviates the impact of high stress disturbance in the mining area on the stress state of the tunnel surrounding rock, achieves a stable production safety effect in the tunnel during mining, and extends the service life of the large tunnel.

[0099] In summary, the present invention proposes a weakening method for directional long-bore hydraulic fracturing of the thick hard rock layer roof on the working face, which can reduce the influence of ground pressure disturbance and strong advanced support stress on the stability of the large tunnel during the recovery of the working face. Specifically, the relevant geological survey data of the mining area are collected, and a drilling site is set up at the adjacent working face. The main control layer of the disaster is analyzed through the relevant theory of the mining area stress field and the relevant monitoring data of the mining area to establish a fracturing geological model, design the drilling trajectory and number, use a kilometer-long directional drilling rig to perform precise drilling and drilling, and perform one hole and one pressure connection operation. By optimizing the structure of the fracturing component Improve the fracturing effect of the fracturing stage and reduce the probability of hole collapse. During the fracturing process, adjust the duration of each fracturing stage according to the water output of the borehole and the indication of the pumping pressure monitoring meter, and arrange the fracturing stages according to the slag discharge of the borehole. Through hydraulic fracturing, a multi-level honeycomb fracture network area is formed around the sealed volume space in the hole, which is mainly composed of high-pressure fracturing cracks, supplemented by secondary extensions and natural fractures to communicate cracks and fracturing joints. This weakens the strength of the rock formation and reduces the impact of high stress disturbances in the mining area on the stress state of the tunnel surrounding rock, so as to achieve a stable and safe production effect in the tunnel during mining and extend the service life of the large tunnel.

[0100] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0101] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0102] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes a number of instructions for a terminal (which can be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in each embodiment of the present invention.

[0103] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A method for weakening the top plate of a deep thick hard rock layer by directional long drilling and staged fracturing, characterized in that: The staged fracturing weakening method comprises: S1: Determine the target layer for fracturing based on the geological data of the mining area and the monitoring data of the working face to be treated; S2: Determine the drilling site construction location and determine the drilling trajectory parameters in the fracturing target layer; S3: Install the fracturing components, determine the fracturing construction parameters, and determine the operation sequence of drilling construction and fracturing construction; S4: According to the drilling trajectory parameters and the fracturing construction parameters, drilling construction is performed at the construction location of the drilling site in accordance with the operation sequence, and fracturing construction is performed through a fracturing assembly, and the stability of the tunnel is monitored throughout the entire process and before and after.

2. The staged fracturing weakening method according to claim 1, characterized in that: The S1 specifically includes: S11: Collect geological data of the mining area and monitoring data of the working face to be treated: drilling column chart, lithology, hydrogeological conditions, cumulative mining thickness, mining area planning and design data of the overlying coal and rock strata on the working face to be treated, microseismic monitoring data of the working face to be treated, acoustic emission monitoring data of the working face to be treated, and tunnel deformation monitoring data; S12: Determine the height of the fracture water conduction zone according to the geological data of the mining area and the monitoring data of the working face to be treated; S13: According to the height of the fracture water-conducting zone, combined with the microseismic monitoring data and the acoustic emission monitoring data, the upper three zones of the working face to be treated are determined, which are the caving zone, the fracture zone and the curved subsidence zone from bottom to top; wherein the target stratum for fracturing is located in the fracture zone and the curved subsidence zone, The spacing between each of the target fracturing layers is at least 10 m, and at least one directional long drill hole is arranged in the fracture zone and the curved subsidence zone.

3. The staged fracturing weakening method according to claim 2, characterized in that: The S2 specifically includes: S21: Arranging the drilling site construction location in the adjacent working face tunnel of the working face to be treated according to the mining area planning and design data; S22: Determine the drilling trajectory parameters in the target fracturing layer, including: the number of directional long drilling holes, the location of directional long drilling holes, the length of the casing section, the length of the deflection section, the length of the stabilizing section, and the range of the inclination angle of the directional long drilling holes, The number and position of the directional long drilling holes are determined by: According to the scope of the upper three zones of the working face to be treated, at least two directional long boreholes are arranged for the thick hard rock layers in the upper three zones, among which the low-position directional long borehole is arranged in the thick hard rock layer more than 10m away from the coal seam to be mined; the spacing between directional long boreholes is at least 10m, and the drilling trajectory avoids faults, cavities, folds and is 2-5m away from the boreholes involved in gas extraction and geological exploration; The length of the sleeve section, the length of the deflection section, and the length of the deflection stabilization section are determined by dividing the drilling trajectory of the directional long drilling hole into three parts, wherein: The first part is the sleeve section, and the length of the sleeve section ranges from about 9 to 15 meters; The second part is the deflection section, which ends when the horizontal projection length of the directional long borehole does not enter the working face to be treated; The third part is the deflection stabilization section, the length of which = the total length of the directional long borehole - the length of the sleeve section - the length of the deflection section; Wherein, the inclination angle variation range of the directional long drilling hole does not exceed 0.75°.

4. The staged fracturing weakening method according to claim 3, characterized in that: In the above S21, the drilling site construction position is arranged near the extension line of the stop mining line of the working face to be treated.

5. The staged fracturing weakening method according to claim 2, characterized in that: In S3, the fracturing components are, from front to back, a deflector, a one-way valve, a first isolation capsule, a first tubular string, a flow interceptor, a second tubular string, a second isolation capsule, a third tubular string, and a safety release; wherein the number of tubular strings between the first isolation capsule and the second isolation capsule is variable.

6. The staged fracturing weakening method according to claim 5, characterized in that: In S3, the fracturing construction parameters include fracturing section length, fracturing section spacing, fracturing area, and fracturing time. Wherein, the method for determining the fracturing construction parameters includes: The fracturing section length is the length between two isolation capsules in the fracturing assembly; The spacing between fracturing stages is adjusted by the number of exiting tubing strings, ranging from 15-30m; The fracturing area is determined according to the hydrogeological conditions, the drilling trajectory of the directional long borehole and the drilling slag conditions: avoiding faults, cavities, fold areas and mudstone areas, with a drilling distance of more than 15m from the fracture zone, and arranged in the stable inclination section of the directional long borehole, covering the entire working surface to be treated; The fracturing time is determined according to the pressure drop curve and the orifice drainage: after the fracturing construction begins, when the pressure drop curve is stable for more than 5 minutes or there are more than 3 pressure drop changes or the pressure reading reaches 70% of the pressure limit of the fracturing string or the orifice drainage is equivalent to the water output of the pump group, the fracturing operation is stopped. The drilling slag condition is determined by: Determine the formation inclination of the target layer for fracturing according to the drilling column diagram of the coal and rock layer overlying the working face to be treated, the hydrogeological conditions or the mining area planning and design data; The drill rod inclination angle is fixed to the formation inclination angle of the target fracturing layer for straight drilling, and the drilling slag discharge during the process is recorded.

7. The staged fracturing weakening method according to claim 1, characterized in that: In S3, the operation sequence of the drilling construction and the fracturing construction is: The construction is carried out from top to bottom according to the height of the designed position of the directional long drilling hole. After the construction of one directional long drilling hole is completed, a segmented hydraulic fracturing will be started immediately, and then the next directional long drilling hole construction will be carried out; after the overall fracturing of the drilling hole is completed, the low-level directional long drilling hole construction will be carried out until the lowest-level directional long drilling hole construction and fracturing are completed.

8. The staged fracturing weakening method according to claim 2, characterized in that: In S4, before and after construction and during fracturing, the displacement changes of the tunnel to be protected, the stress conditions of the top and bottom plates, the anchor cables on both sides, and the overall deformation and damage of the surrounding rock are monitored in real time, and the data changes before and after the overall fracturing construction of each directional long borehole are analyzed. The stability of the tunnel is confirmed based on the tunnel deformation monitoring data, and it is determined whether to adjust the number and position of the directional long boreholes.

9. A directional long-hole staged fracturing weakening system for the top plate of a deep thick hard rock formation, the system comprising: A processor and a memory for storing executable instructions; characterized in that the processor is configured to execute the executable instructions to perform the directional long-hole segmented fracturing weakening method for the top plate of a deep thick hard rock formation according to any one of claims 1 to 8.

10. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed by a processor, the method for directional long drilling staged fracturing and weakening the top plate of a deep thick hard rock layer according to any one of claims 1 to 8 is implemented.

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