Bidirectional double-row water injection softening drill hole arrangement method suitable for weakly cemented stratum

Abstract

The invention relates to the technical field of coal mining, in particular to a bidirectional double-row water injection softening drill hole arrangement method suitable for a weakly cemented stratum. The method comprises the following steps: (1) determining the position of the weakly cemented formation; (2) acquiring actual acquisition data of the weakly cemented formation, and determining fracturing parameters of a hydraulic fracturing drill hole according to the actual acquisition data; (3) according to the fracturing parameters, numerical simulation is carried out according to the position of the weakly cemented formation, and a two-way double-row hydraulic fracturing drilling track is arranged; and (4) two-way double-row water injection softening drill holes are formed according to the hydrofracture drill hole track, and water injection operation is conducted on the weakly cemented stratum in sequence. According to the method, the two-way double-row water injection softening drill holes are formed according to the hydraulic fracturing drill hole track, water injection operation is conducted on the weakly cemented stratum in sequence, water injection is uniform through the two-way double-row arrangement mode, and softening and caving of roof rocks are facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of coal mining, and in particular to a two-way double-row water injection softening drilling hole arrangement method suitable for weakly cemented strata. Background Art

[0002] The Jurassic and Cretaceous strata are of relatively late diagenesis, and their properties have some unique characteristics, such as weak cementation, easy weathering, and easy mud and sandification when exposed to water. Due to the relatively hard and complete structure of the overburden, it is difficult to grasp the law of mine pressure in the initial mining stage of the working face. The intuitive manifestation is that the initial pressure step is too large, and the timing of the pressure from the hard roof is difficult to predict, resulting in strong mine pressure on the working face, significantly increasing the risk of impact, and easily causing impact-type dynamic disasters.

[0003] In the process of coal mining, roof control is a crucial link to ensure the safe recovery of the working face. Traditional roof control methods often rely on means such as blasting or mechanical cutting, which have certain limitations and shortcomings. In view of the characteristics of weakly cemented strata, the use of water injection softening technology can effectively achieve the stress release of the roof. For example, the patent "A method for controlling the step distance of collapse by hydraulic softening and cutting" (CN114483036A) proposes a new technical solution, that is, softening the rock strata by water injection and reducing the rock strength to achieve the purpose of controlling the step distance of the roof collapse. Although the above patent provides an effective roof control method, the following technical problems still exist in actual application: under certain formation conditions, unidirectional water injection may not be able to evenly soften the entire target layer, resulting in uneven softening effect and affecting the control accuracy of the collapse step distance.

[0004] In order to improve the control accuracy of the collapse step, the drilling arrangement can be carried out in a targeted manner. Although the traditional drilling arrangement methods, such as the right-angle arrangement method and the parallel arrangement method, can control the pressure of the hard roof overlying the coal seam in the high-stress area to a certain extent, they each have their own limitations. The right-angle arrangement method is not ideal for improving the stability of the coal seam due to the insufficient density of the drilling holes; and the parallel arrangement method is inefficient due to its high demand for manpower and material resources and a long construction period. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes a method for arranging two-way double-row water injection and softening drilling holes suitable for weakly cemented strata. By arranging two-way double-row water injection holes in the target layer, the water injection efficiency and the uniformity of the softening effect are improved, so as to more accurately control the collapse step distance. By optimizing the water injection parameters and the drilling arrangement, the impact on the surrounding environment is reduced, such as controlling the water injection volume and water injection pressure to reduce the impact on the groundwater level and ground subsidence. At the same time, the water injection parameters can be adjusted according to the characteristics of the stratum to make it suitable for a wider range of stratum conditions.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A two-way double-row water injection softening drilling arrangement method applicable to weakly cemented formations, the method comprising:

[0008] (1) Determine the location of the weakly cemented strata;

[0009] (2) obtaining actual acquisition data of the weakly cemented formation, and determining the fracturing parameters of the hydraulic fracturing borehole according to the actual acquisition data, wherein the fracturing parameters include the radial fracturing pressure of the hydraulic fracturing through the layer, the amount of fracturing fluid, and the water injection wetting radius;

[0010] (3) performing numerical simulation according to the location of the weakly cemented formation and arranging a bidirectional and double-row hydraulic fracturing drilling trajectory;

[0011] (4) Arranging bidirectional double-row water injection softening boreholes according to the hydraulic fracturing drilling trajectory, and performing water injection operations on the weakly cemented formation in turn.

[0012] Furthermore, in step (2), the actual collected data includes geological related parameters and physical and mechanical parameters, specifically including: vertical stress q0, lateral stress coefficient λ c , tensile strength R of layered coal ti , Pipe radius γ g , Pipeline length h g , fracturing hole radius γ k , Coal seam volume within the fracturing influence range v 体 , water absorption coefficient λ, length of the seepage part of the borehole l, injection time t, rock bulk density γ, rock water absorption rate n, injection flow rate Q, and uneven coefficient K.

[0013] Furthermore, in step (2), the radial fracturing pressure of the cross-layer hydraulic fracturing is determined by the following formula:

[0014] p H =(1+λ c )q0+2(1-λ c )q0cos 2θ+min{R ti}

[0015] i=1,2;…,m

[0016] Among them, p H Indicates the radial fracture initiation pressure of hydraulic fracturing, unit: MPa; q 0、 R ti Respectively represent the vertical stress and the tensile strength of the i-th layer of coal, in MPa; λ crepresents the lateral stress coefficient; θ represents the elevation angle between the bedding plane and the axis of the borehole, in degrees; i represents the number of coal layers passed through by the borehole; and m represents the maximum number of coal layers passed through by the borehole.

[0017] Furthermore, in step (2), the amount of the fracturing fluid is determined by the following formula:

[0018] v c =v g +v k +v 水

[0019]

[0020] v 水 =0.02v 体 λ2λ3

[0021] Among them, v c 、v g 、v k Respectively represent the total water consumption, the water required for filling the pipe and the water required for fracturing holes, in units of m 3 ; γ g 、h g , γ k They represent pipeline radius, pipeline length, and fracturing hole radius, respectively, in m; v 水 、v 体 Respectively represent the amount of fracturing fluid and the volume of coal seam within the fracturing influence range, unit: m 3 ; λ2 represents the water absorption coefficient of the bottom rock layer; λ3 represents the water absorption coefficient when the coal seam is dense and hard.

[0022] Furthermore, in step (2), the water injection wetting radius is determined by the following formula:

[0023]

[0024] Wherein, R is the water injection wetting radius, in m; l is the length of the seepage part of the borehole, in m; t is the water injection time, in min; γ is the rock bulk density, in t / m; n is the rock water absorption rate, in %; Q is the water injection flow rate, in t / min; K is the non-uniformity coefficient, which is 0.08 to 0.2.

[0025] Furthermore, in step (3), numerical simulation design is performed according to the location of the weakly cemented stratum, and the software used is Flac 3D, COMSOL, XSite or ABAQUS.

[0026] Furthermore, in step (3), the method for arranging the bidirectional and dual-row hydraulic fracturing drilling trajectory specifically includes:

[0027] According to the lithology column chart, high-position hydraulic fracturing boreholes and low-position hydraulic fracturing boreholes are designed on the cutting side; the bottom of the high-position hydraulic fracturing borehole completely exceeds a basic top rock layer of the head rock of the comprehensive excavation rock tunnel on the cutting side, and the bottom of the low-position hydraulic fracturing borehole completely exceeds a direct top rock layer of the head rock of the comprehensive excavation rock tunnel on the cutting side by more than 2 to 3 meters. When there is no direct top rock layer, the bottom of the low-position hydraulic fracturing borehole completely exceeds the coal seam by more than 2 to 3 meters; and the elevation angle between the designed bedding plane and the borehole axis is greater than the internal friction angle of the rock, and the designed borehole spacing is greater than the water injection wetting radius. The high-position hydraulic fracturing boreholes and the low-position hydraulic fracturing boreholes cover the hard rock layer range above the direct top rock layer, the basic top rock layer, the direct top rock layer, and the basic top rock layer;

[0028] A single layer of hydraulic fracturing boreholes is set on the side of the belt drift, that is, belt drift boreholes are set; the borehole diameter of the belt drift boreholes is 75-80mm, the borehole length of the belt drift boreholes exceeds a basic top rock layer in the head rock of the comprehensive excavation rock tunnel by 2-5m, and the elevation angle between the bedding plane and the borehole axis is greater than the internal friction angle of the rock by 1-3°.

[0029] Furthermore, in step (4), it is determined that the water injection operation specifically includes: after the drilling construction, the AB glue sealing process is used to seal the hole, the sealing length is 3 to 3.5 m, and after the hole is sealed, a valve is installed at the hole mouth, and then a high-pressure water pump is connected to control the fracturing pressure to be greater than the radial fracturing pressure of the through-layer hydraulic fracturing, and the amount of fracturing fluid is greater than the total amount of water, to ensure that the borehole is full of water and has a certain outward diffusion pressure. The water injection operation time is 10 to 12 days.

[0030] Furthermore, the method further comprises step (5): setting up a tunnel displacement monitoring station according to the arrangement positions of the bidirectional double-row water injection softening boreholes to analyze and evaluate the fracturing pressure relief effect.

[0031] Further, step (5) specifically includes: according to the hydraulic fracturing drilling trajectory, a set of tunnel displacement monitoring stations is constructed every 30 to 35 meters from the drilling position, and a total of 10 to 12 sets are arranged.

[0032] Beneficial effects of the present invention:

[0033] (1) The method provided by the present invention is used to determine key parameters such as the water injection wetting radius, fracturing pressure, and fracturing fluid volume in the thick hard coal seam overlying the mined coal seam. By designing two-way double-row water injection softening boreholes at different heights for coordinated fracturing, the hydraulic fracturing borehole trajectory is arranged according to the fracturing parameters of the hydraulic fracturing borehole, which effectively weakens the strength structure of the thick hard rock layer on the roof of the weakly cemented stratum, reduces the initial pressure step distance and the working face pressure strength, and effectively achieves the purpose of regulating the pressure step distance of the hard roof and the working face pressure peak value.

[0034] (2) The method provided by the present invention is suitable for controlling the pressure of the hard roof overlying the coal seam in the high stress area of ​​the weakly cemented stratum. The hydraulic fracturing parameters such as the water injection wetting radius, the fracturing pressure, and the amount of fracturing fluid are determined by using the actual collected data and numerical simulation software. According to the hydraulic fracturing drilling trajectory, a two-way double-row water injection softening drill hole is arranged, and the weakly cemented stratum is injected with water in turn. The two-way double-row arrangement method injects water evenly, which is beneficial to the softening and falling of the roof rock.

[0035] (2) The method provided by the present invention optimizes the spacing between drill holes and effectively controls the number of drill holes by staggered arrangement of high and low-level water injection softening drill holes at the opening of the mining face. This not only improves the stability of the coal seam, but also significantly reduces the construction cost and time, ensuring the safety and efficient mining of the working face. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] 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.

[0037] Figure 1 A flow chart of a method for arranging bidirectional and double-row water injection softening drilling holes suitable for weakly cemented formations according to an embodiment of the technical solution of the present invention is shown.

[0038] Figure 2 A contour map of pore water pressure distribution in a water-injected softened roof according to an embodiment of the technical solution of the present invention is shown.

[0039] Figure 3 The vertical stress influence zone of the inclined section of the bidirectional double-row water injection borehole according to one embodiment of the technical solution of the present invention is shown.

[0040] Figure 4 A plan view of a drilling arrangement according to an embodiment of the technical solution of the present invention is shown.

[0041] Figure 5 A cross-sectional view of the drilling arrangement of a belt chute according to an embodiment of the technical solution of the present invention is shown.

[0042] Figure 6 This is the tunnel deformation data diagram of the measuring point.

[0043] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0044] Here, exemplary embodiments will be described in detail, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are only examples of devices and methods consistent with some aspects of the present disclosure.

[0045] The terms "first", "second", etc. in 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, for example, be implemented in an order other than those illustrated or described herein.

[0046] 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.

[0047] Multiple includes two or more.

[0048] 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.

[0049] Embodiment 1: A bidirectional double-row water injection softening drilling arrangement method applicable to weakly cemented strata, particularly applicable to the bidirectional double-row water injection softening drilling pressure relief scheme design in the field of coal seam roof pressure relief engineering when the working face length is greater than 100m. The bidirectional double-row arrangement of drilling holes realizes uniform water injection, which is beneficial to the softening and caving of the roof rock, thereby improving the regional pressure relief effect.

[0050] The method comprises:

[0051] (1) determining the location of the weakly cemented stratum; specifically, determining the location of the weakly cemented stratum based on geological survey data and mining data; the mining data include lithology column chart, rock density, porosity, water content, elastic modulus, compressive strength, tensile strength, cohesion, internal friction angle and Poisson's ratio;

[0052] (2) obtaining actual acquisition data of the weakly cemented formation, and determining the fracturing parameters of the hydraulic fracturing borehole according to the actual acquisition data, wherein the fracturing parameters include the radial fracturing pressure of the hydraulic fracturing through the layer, the amount of fracturing fluid, and the water injection wetting radius;

[0053] (3) performing numerical simulation according to the location of the weakly cemented formation and arranging a bidirectional and double-row hydraulic fracturing drilling trajectory;

[0054] (4) Arranging bidirectional double-row water injection softening boreholes according to the hydraulic fracturing drilling trajectory, and performing water injection operations on the weakly cemented formation in turn.

[0055] In step (2) of this embodiment, the actual collected data includes geological related parameters and physical and mechanical parameters, specifically including: vertical stress q0, lateral stress coefficient λ c , tensile strength R of layered coal ti , Pipe radius γ g , Pipeline length h g , fracturing hole radius γ k , Coal seam volume within the fracturing influence range v 体 , water absorption coefficient λ, length of the seepage part of the borehole l, injection time t, rock bulk density γ, rock water absorption rate n, injection flow rate Q, and uneven coefficient K.

[0056] In step (2) of this embodiment, the radial fracturing pressure of the cross-layer hydraulic fracturing is determined by the following formula:

[0057] p H =(1+λ c )q0+2(1-λ c )q0cos 2θ+min{R ti}

[0058] i=1,2;…,m

[0059] Among them, p H Indicates the radial fracture initiation pressure of hydraulic fracturing, unit: MPa; q0, R ti Respectively represent the vertical stress and the tensile strength of the i-th layer of coal, in MPa; λ c represents the lateral stress coefficient; θ represents the angle, unit is °; i represents the number of coal layers passed by the borehole; m represents the maximum number of coal layers passed by the borehole.

[0060] In step (2) of this embodiment, the amount of the fracturing fluid is determined by the following formula:

[0061] v c =v g +v k +v 水

[0062]

[0063] v 水 =0.02v 体 λ2λ3

[0064] Among them, v c 、v g 、v k Respectively represent the total water consumption, the water required for filling the pipe and the water required for fracturing holes, in units of m 3 ; γ g 、h g , γ k They represent pipeline radius, pipeline length, and fracturing hole radius, respectively, in m; v 水 、v 体 Respectively represent the amount of fracturing fluid and the volume of coal seam within the fracturing influence range, unit: m 3 ; λ2 represents the water absorption coefficient of the bottom rock layer; λ3 represents the water absorption coefficient when the coal seam is dense and hard.

[0065] In step (2) of this embodiment, the water injection wetting radius is determined by the following formula:

[0066]

[0067] Wherein, R is the water injection wetting radius, in m; l is the length of the seepage part of the borehole, in m; t is the water injection time, in min; γ is the rock bulk density, in t / m; n is the rock water absorption rate, in %; Q is the water injection flow rate, in t / min; K is the non-uniformity coefficient, which is 0.08 to 0.2.

[0068] In step (3) of this embodiment, numerical simulation design is performed according to the location of the weakly cemented formation, and the numerical fracturing software used is Flac 3D, COMSOL, XSite or ABAQUS.

[0069] The fracturing numerical software was used to simulate and analyze the diffusion radius of single-hole water injection softening. The injection pressure was 1MPa, the initial pore water pressure of the top plate was 0.1MPa, and the pore water pressure diffusion process was as follows: Figure 2 As shown in the figure, the softening range of roof water injection is 1m from the injection hole. According to the softening range of roof water injection, the hydraulic fracturing drilling trajectory is confirmed for simulation analysis, such as Figure 3 shown.

[0070] In step (3), the method for arranging the bidirectional and dual-row hydraulic fracturing drilling trajectory specifically includes:

[0071] Design high-position hydraulic fracturing boreholes and low-position hydraulic fracturing boreholes on the cut-eye side according to the lithology columnar diagram; the bottom of the high-position hydraulic fracturing borehole completely exceeds a basic top rock layer of the head rock of the comprehensive excavation rock tunnel on the cut-eye side, and the bottom of the low-position hydraulic fracturing borehole completely exceeds a direct top rock layer of the head rock of the comprehensive excavation rock tunnel on the cut-eye side by more than 2 to 3 meters. When there is no direct top rock layer, the bottom of the low-position hydraulic fracturing borehole completely exceeds the coal seam by more than 2 to 3 meters, and the elevation angle between the designed bedding plane and the borehole axis is greater than the internal friction angle of the rock, the designed borehole diameter is greater than the water injection wetting radius, and the high-position hydraulic fracturing borehole and the low-position hydraulic fracturing borehole cover the hard rock layer range of the direct top rock layer, the basic top rock layer, and the direct top rock layer and the basic top rock layer;

[0072] A single layer of hydraulic fracturing boreholes is set on the side of the belt drift, that is, belt drift boreholes are set; the borehole diameter of the belt drift boreholes is 75-80mm, the borehole length of the belt drift boreholes exceeds a basic top rock layer in the head rock of the comprehensive excavation rock tunnel by 2-5m, and the elevation angle between the bedding plane and the borehole axis is greater than the internal friction angle of the rock by 1-3°.

[0073] Specifically, in this embodiment, the roof of the weakly cemented stratum is softened by water injection in a bidirectional double-row arrangement according to the range of water injection softening of the roof, such as Figure 4 As shown. 12 low-level boreholes and 15 high-level boreholes are arranged on the roof of the working face cutting eye and the belt chute to weaken the roof within 30m in front of the cutting eye and 48m above the top. Seven boreholes with a spacing of 7m are arranged on the roof of the belt chute side to soften the roof 45m above the coal seam and 12m in horizontal distance. The design form of high and low-level boreholes covers the hard rock range of the direct roof, basic roof and the top thereof. Low-level borehole Ⅰ(01), low-level borehole Ⅱ(02), low-level borehole Ⅲ(03), low-level borehole Ⅳ(04), low-level borehole Ⅴ(05), low-level borehole VI(06), low-level borehole VII(07), low-level borehole VIII(08), low-level borehole IX(09), low-level borehole X(10), low-level borehole

[0074] The borehole diameters of Ⅺ(11) and low-position boreholes Ⅻ(12) are both 75-80 mm. The borehole length is designed to exceed one of the direct top rock layers by 2-5 m according to the hardness of the rock facing the comprehensive excavation rock tunnel. The elevation angle should be 1-3° greater than the rock internal friction angle. The horizontal distance between low-position borehole Ⅰ(01) and the track drift (along the empty side) is 6-7 m. The continuous borehole spacing between low-position borehole Ⅱ(02) and low-position borehole Ⅻ(12) is determined according to the wetting range (wetting radius) of the water injection hole, and the horizontal distance is 20-22 m.

[0075] High-position drilling hole Ⅰ(13), high-position drilling hole Ⅱ(14), high-position drilling hole Ⅲ(15), high-position drilling hole

[0076] The diameters of the boreholes IV (16), high-position borehole V (17), high-position borehole VI (18), high-position borehole VII (19), high-position borehole VIII (20), high-position borehole IX (21), high-position borehole X (22), high-position borehole XI (23), high-position borehole XII (24), high-position borehole XIII (25), high-position borehole XIV (26), and high-position borehole XV (27) are all 75 to 80 mm, and the borehole length is set according to the hardness of the rock at the head of the comprehensive excavation rock tunnel. The length exceeds one of the basic top rock layers by 2 to 5 meters. The elevation angle should be greater than the rock internal friction angle by 1 to 3 degrees. The high-position borehole I (1) is located in the track slot (along the air side). The spacing between the continuous boreholes from high-position borehole II (14) to high-position borehole XIV (26) is determined according to the wetting range (wetting radius) of the water injection hole. The horizontal distance is 20 to 22 meters. The horizontal distance between high-position borehole XV (27) and high-position borehole XIV (26) is 9 to 10 meters.

[0077] like Figure 5 As shown, a single layer of hydraulic fracturing holes is set on the side of the belt drift. The diameters of the boreholes of the belt chute I (28), II (29), III (30), IV (31), V (32), VI (33) and VII (34) are all 75 to 80 mm. The borehole length is designed to exceed one of the basic top rock layers by 2 to 5 m according to the hardness of the rock at the head of the comprehensive excavation rock tunnel. The elevation angle should be 1 to 3 degrees greater than the internal friction angle of the rock. The hole spacing is determined according to the wetting range (wetting radius) of the water injection hole. The horizontal distance between the belt chute borehole I (28) and the cut eye is 7 to 8 m. Six boreholes with a spacing of 7 to 8 m are arranged in sequence from the belt chute borehole I (28), from the belt chute borehole II (29) to the belt chute borehole VII (34).

[0078] In step (4) of this embodiment, it is determined that the water injection operation specifically includes: after the drilling construction, the AB glue sealing process is used to seal the hole, the sealing length is 3 to 3.5 m, and a valve is installed at the hole mouth after sealing, and then a high-pressure water pump is connected. The designed fracturing pressure is greater than the radial fracturing pressure of the through-layer hydraulic fracturing, and the amount of fracturing fluid is greater than the total amount of water, ensuring that the borehole is full of water and has a certain outward diffusion pressure. The water injection operation time is 10 to 12 days.

[0079] In this embodiment, the method further comprises step (5): setting up a tunnel displacement monitoring station according to the arrangement positions of the bidirectional double-row water injection softening boreholes to analyze and evaluate the fracturing pressure relief effect.

[0080] Step (5) specifically includes: according to the hydraulic fracturing drilling trajectory, a set of tunnel displacement monitoring stations is constructed every 30 to 35 meters from the drilling position, with a total of 10 to 12 sets. The tunnel displacement change and the collapse of the old mountain are monitored, and the effect of fracturing pressure relief is analyzed by comparing the tunnel bottom heave, roof subsidence and the amount of movement of the two sides of the non-fracturing pressure relief section and the fracturing pressure relief section. The effect is as follows: Figure 6 As shown in the figure, the maximum support pressure value is 43.85MPa, the minimum is 18.9MPa, and the average is 31.9MPa. When the working face was first pressed, there was no large-scale water leakage from the roof, indicating that the softening area of ​​the roof water injection was controllable and no leakage occurred during the water injection.

[0081] The bidirectional double-row water injection softening drilling arrangement method provided by the present invention is suitable for weakly cemented strata. A drilling site is arranged in the adjacent working face tunnels of the target treatment area to carry out hydraulic fracturing drilling trajectory and construction. The roof is cut off and the roof surrounding rock is weakened in time through hydraulic fracturing to relieve pressure, reduce the cantilever length of the isolated triangle plates on both sides of the working face, cut off the transmission of mining stress to the air intake tunnel direction, make the roof of the goaf collapse in time and fully, improve the utilization rate of drilling holes, be safe and efficient, and have wide practicality.

[0082] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0083] In addition, those skilled in the art will understand that, although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments also means being within the scope of protection of the present invention and forming different embodiments. For example, in the above embodiments, those skilled in the art can use them in combination according to the known technical solutions and the technical problems to be solved by this application.

[0084] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this patent can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A two-way double-row water injection softening drilling arrangement method suitable for weakly cemented formations, characterized in that: The method comprises: (1) Determine the location of the weakly cemented strata; (2) obtaining actual acquisition data of the weakly cemented formation, and determining the fracturing parameters of the hydraulic fracturing borehole according to the actual acquisition data, wherein the fracturing parameters include the radial fracturing pressure of the hydraulic fracturing through the layer, the amount of fracturing fluid, and the water injection wetting radius; (3) performing numerical simulation according to the location of the weakly cemented formation and arranging a bidirectional and double-row hydraulic fracturing drilling trajectory; (4) Arranging bidirectional double-row water injection softening boreholes according to the hydraulic fracturing drilling trajectory, and performing water injection operations on the weakly cemented formation in turn.

2. The method for arranging two-way double-row water injection and softening drilling holes for weakly cemented formations according to claim 1 is characterized in that: In step (2), the actual collected data includes geological related parameters and physical and mechanical parameters, specifically including: vertical stress q0, lateral stress coefficient λ c , tensile strength R of layered coal ti , Pipe radius γ g , Pipeline length h g , fracturing hole radius γ k , Coal seam volume within the fracturing influence range v 体 , water absorption coefficient λ, length of the seepage part of the borehole l, injection time t, rock bulk density γ, rock water absorption rate n, injection flow rate Q, and uneven coefficient K.

3. The method for arranging two-way double-row water injection and softening drilling holes for weakly cemented formations according to claim 2 is characterized in that: In step (2), the radial fracturing pressure of the cross-layer hydraulic fracturing is determined by the following formula: p H =(1+λ c )q0+2(1-λ c )q0cos 2θ+min{R ti } i=1,2;…,m Among them, p H Indicates the radial fracture initiation pressure of hydraulic fracturing, unit: MPa; q0, R ti Respectively represent the vertical stress and the tensile strength of the i-th layer of coal, in MPa; λ c represents the lateral stress coefficient; θ represents the elevation angle between the bedding plane and the axis of the borehole, in degrees; i represents the number of coal layers passed through by the borehole; and m represents the maximum number of coal layers passed through by the borehole.

4. The method for arranging two-way double-row water injection and softening drilling holes for weakly cemented formations according to claim 2 is characterized in that: In step (2), the amount of the fracturing fluid is determined by the following formula: v c =v g +v k +v 水 v 水 =0.02v 体 λ2λ3 Among them, v c 、v g 、v k Respectively represent the total water consumption, the water required for filling the pipe and the water required for fracturing holes, in units of m 3 ;v 水 、v 体 Respectively represent the amount of fracturing fluid and the volume of coal seam within the fracturing influence range, unit: m 3 ; γ g 、h g , γ k They represent the pipeline radius, pipeline length, and fracturing hole radius, respectively, in meters; λ2 represents the water absorption coefficient of the bottom rock layer; λ3 represents the water absorption coefficient when the coal seam is dense and hard.

5. The method for arranging two-way double-row water injection and softening drilling holes for weakly cemented formations according to claim 2 is characterized in that: In step (2), the water injection wetting radius is determined by the following formula: Wherein, R is the water injection wetting radius, in m; l is the length of the seepage part of the borehole, in m; t is the water injection time, in min; γ is the rock bulk density, in t / m; n is the rock water absorption rate, in %; Q is the water injection flow rate, in t / min; K is the non-uniformity coefficient, which is 0.08 to 0.

2.

6. The method for arranging two-way double-row water injection and softening drilling holes for weakly cemented formations according to claim 1 is characterized in that: In step (3), numerical simulation design is performed according to the location of the weakly cemented stratum, and the software used is Flac3D, COMSOL, XSite or ABAQUS.

7. The method for arranging two-way double-row water injection and softening drilling holes for weakly cemented formations according to claim 1 is characterized in that: In step (3), the method for arranging the bidirectional and dual-row hydraulic fracturing drilling trajectory specifically includes: Design high-position hydraulic fracturing boreholes and low-position hydraulic fracturing boreholes on the cut-eye side according to the lithology columnar diagram; the bottom of the high-position hydraulic fracturing borehole completely exceeds a basic top rock layer of the head rock of the comprehensive excavation rock tunnel on the cut-eye side, and the bottom of the low-position hydraulic fracturing borehole completely exceeds a direct top rock layer of the head rock of the comprehensive excavation rock tunnel on the cut-eye side by more than 2 to 3 meters. When there is no direct top rock layer, the bottom of the low-position hydraulic fracturing borehole completely exceeds the coal seam by more than 2 to 3 meters, and the elevation angle between the designed bedding plane and the borehole axis is greater than the internal friction angle of the rock, the designed borehole spacing is greater than the water injection wetting radius, and the high-position hydraulic fracturing boreholes and the low-position hydraulic fracturing boreholes cover the hard rock layer range above the direct top rock layer, the basic top rock layer, the direct top rock layer, and the basic top rock layer; A single layer of hydraulic fracturing boreholes is set on the side of the belt drift, that is, belt drift boreholes are set; the borehole diameter of the belt drift boreholes is 75-80mm, the borehole length of the belt drift boreholes exceeds a basic top rock layer in the head rock of the comprehensive excavation rock tunnel by 2-5m, and the elevation angle between the bedding plane and the borehole axis is greater than the internal friction angle of the rock by 1-3°.

8. The method for arranging two-way double-row water injection and softening drilling holes for weakly cemented formations according to claim 1 is characterized in that: In step (4), it is determined that the water injection operation specifically includes: after the drilling construction, the AB glue sealing process is used to seal the hole, the sealing length is 3 to 3.5 m, and after the hole is sealed, a valve is installed at the hole mouth, and then a high-pressure water pump is connected to control the fracturing pressure to be greater than the radial fracturing pressure of the through-layer hydraulic fracturing, the amount of fracturing fluid is greater than the total amount of water, and the water injection operation time is 10 to 12 days.

9. The method for arranging two-way double-row water injection and softening drilling holes for weakly cemented formations according to claim 1, characterized in that: The method further comprises step (5): setting up a tunnel displacement monitoring station according to the arrangement positions of the bidirectional double-row water injection softening boreholes to analyze and evaluate the fracturing pressure relief effect.

10. The method for arranging two-way double-row water injection and softening drilling holes for weakly cemented formations according to claim 9, characterized in that: Step (5) specifically includes: according to the hydraulic fracturing drilling trajectory, one set of tunnel displacement monitoring stations is constructed and arranged every 30 to 35 meters from the drilling position, with a total of 10 to 12 sets.

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