A method for ground fracturing isolation and flood elimination in steep coal seam fault zone

Abstract

The present application belongs to the technical field of coal mining safety, and particularly relates to a method for ground fracturing isolation and pressure relief of steeply inclined coal seam fault zone. The method comprises the following steps: S1. obtaining geological parameters of the working face; S2. according to the geological parameters of the working face obtained in S1, arranging an upper and lower inclined shaft from the ground; S3. performing fracturing work in the upper inclined shaft, performing asymmetric directional perforation operation in the fracturing area of the upper inclined shaft, and pumping fracturing fluid into the upper wall rock of the fault through a ground high-pressure pump; S4. performing fracturing work in the lower inclined shaft, performing asymmetric directional perforation operation in the fracturing area of the lower inclined shaft, and pumping fracturing fluid into the lower wall rock of the fault through a ground high-pressure pump, and completing the fracturing process. The present application can solve the problem that, in the existing steeply inclined coal seam fault zone mining, the length of the inclined shaft is unreasonable and the fracturing area cannot completely cover the fault influence zone due to the failure to combine the coal seam inclination and fault type for quantitative design, thereby causing disasters such as rock burst and rock movement.

Description

Technical Field

[0001] This invention belongs to the field of coal mining safety technology, specifically relating to a method for surface fracturing isolation and erosion mitigation in steeply inclined coal seam fault zones. Background Technology

[0002] Steeply inclined coal seams in my country are mainly distributed in the southwest and northwest mining areas. These coal seams have complex occurrence conditions, and most mining areas are accompanied by fault structures. At the same time, due to the large dip angle of steeply inclined coal seams, the component of the rock strata's self-weight force is significant along the dip of the coal seam, and the fault zone is prone to become a stress concentration zone, which can easily trigger rock bursts, rock strata movement, and even water inrush disasters during mining.

[0003] Existing fault zone control technologies have significant limitations: traditional downhole local fracturing technology requires entry into the mining area, which is difficult to deploy due to the spatial constraints of steeply dipping coal seams, and the fracturing coverage cannot completely encompass the fault-affected zone. Some surface fracturing technologies simply copy the design experience of gently dipping coal seams without considering the influence of the steeply dipping coal seam's dip angle on the fracturing fluid diffusion direction and the stress on the inclined well. They rely solely on manual estimation to determine the length of the inclined well and the location of the intended fracturing area, leading to uncontrolled fracture propagation, failure to cover the core fault-affected zone, and insufficient isolation and shock absorption effects; or excessive fracturing damages normal coal seams, resulting in resource waste.

[0004] Furthermore, in deep, steeply inclined coal seam mining scenarios, ground stress increases significantly, exacerbating the risk of fault activation. Existing technologies, lacking quantitative correlation models between geological and engineering parameters, struggle to dynamically adapt to changes in ground stress, further leading to control failures. In summary, the industry urgently needs a surface fracturing technology based on multiple geological parameters and capable of precise quantitative design to resolve the safety and efficiency contradiction in mining steeply inclined coal seam fault zones. Summary of the Invention

[0005] The purpose of this invention is to provide a method for surface fracturing isolation and shock reduction in steeply inclined coal seam fault zones. This method aims to solve the problem that in existing steeply inclined coal seam fault zone mining, the lack of quantitative design based on coal seam dip angle and fault type leads to unreasonable inclined shaft lengths and the inability of the planned fracturing area to completely cover the fault influence zone, thereby causing disasters such as rock bursts and rock strata movement.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for surface fracturing isolation and scour mitigation in steeply inclined coal seam fault zones includes the following steps: S1. Obtain the geological parameters of the working face, including the upper and lower horizontal elevations of the proposed mining area of ​​the steeply dipping coal seam on the footwall of the fault as b1 and a1, respectively, and the dip angle of the coal seam as α1; the upper and lower horizontal elevations of the proposed mining area of ​​the steeply dipping coal seam on the footwall of the fault as b2 and a2, respectively, and the dip angle of the coal seam as α2; the dip angle of the fault as β; and define the width of the fault influence zone as S. S2. Based on the geological parameters of the working face obtained in S1, drill downwards from the ground to arrange the upper and lower inclined shafts; S3. Carry out fracturing work on the upper inclined well, carry out asymmetric directional perforation operation in the area to be fracturing in the upper inclined well, and pump fracturing fluid into the upper rock layer of the fault through a surface high-pressure pump; S4. Perform fracturing work on the lower plate of the inclined well. Conduct asymmetric directional perforation operations in the area to be fracturing in the lower plate of the inclined well, and pump fracturing fluid into the rock strata of the lower plate of the fault through a surface high-pressure pump to complete the entire fracturing process.

[0007] Compared with the prior art, the present invention has the following advantages: This invention derives quantitative formulas for the length of inclined shafts and the distance beyond which fracturing is to be carried out based on geological parameters, clarifies the matching schemes for normal and reverse faults, avoids problems such as unreasonable inclined shaft size and deviation in fracturing range, enables precise matching of fracturing technology with geological conditions, greatly improves the targeting of construction, and makes mine production safer and more reliable. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly described below.

[0009] Figure 1 This is a schematic diagram of the process for a method of surface fracturing isolation and erosion reduction in a steeply inclined coal seam fault zone according to the present invention.

[0010] Figure 2 This is a schematic diagram of the inclined shaft layout of the normal fault zone in a steeply inclined coal seam, as described in the present invention, a method for surface fracturing and isolation of a fault zone in a steeply inclined coal seam.

[0011] Figure 3 This is a schematic diagram of the inclined shaft layout of the reverse fault zone in a surface fracturing isolation and erosion elimination method for a steeply inclined coal seam fault zone according to the present invention.

[0012] Figure 4 This is a schematic diagram of asymmetric directional perforation in a surface fracturing isolation and flushing method for steeply inclined coal seam fault zones according to the present invention.

[0013] Explanation of the attached diagram labels: 1-Upper hanging wall inclined shaft, 2-Lower hanging wall inclined shaft, 3-Fault, 4-Coal seam. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0015] Example 1 A method for surface fracturing isolation and scour reduction in steeply dipping coal seam fault zones, such as... Figure 1 As shown, it includes the following steps: S1. Obtain the geological parameters of the working face, including the upper and lower horizontal elevations of the proposed mining area of ​​the steeply dipping coal seam 4 on the hanging wall of fault 3 (b1 and a1 respectively) and the dip angle of coal seam 4 (α1); the upper and lower horizontal elevations of the proposed mining area of ​​the steeply dipping coal seam 4 on the footwall of fault 3 (b2 and a2 respectively) and the dip angle of coal seam 4 (α2); the dip angle of fault 3 (β); define the width of the influence zone of fault 3 as S, which is obtained through geological exploration.

[0016] S2. Based on the geological parameters of the working face obtained in S1, arrange the upper inclined shaft 1. For example... Figure 2 and Figure 3 As shown, drilling proceeds downwards from the ground, with the upper inclined shaft 1 positioned above fault 3. The upper inclined shaft 1 is parallel to the dip direction of fault 3, meaning its dip angle is equal to the dip angle β of fault 3. The upper inclined shaft 1 also makes an angle β with the horizontal direction. Let the vertical distance between the upper inclined shaft 1 and fault 3 be L. When fault 3 is a normal fault, the length of the upper inclined shaft 1 is L. 上正 When fault 3 is a reverse fault, the length of the hanging wall inclined shaft 1 is L. 上逆 The calculation formula is as follows: S3. Based on the geological parameters of the working face obtained in S1, arrange the lower inclined shaft 2. For example... Figure 2 and Figure 3 As shown, drilling proceeds downwards from the ground, with the lower inclined shaft 2 positioned below fault 3. The lower inclined shaft 2 is parallel to the dip direction of fault 3, meaning its dip angle is equal to the dip angle β of fault 3. The lower inclined shaft 2 also makes an angle β with the horizontal direction. Let the vertical distance between the lower inclined shaft 2 and fault 3 be D. When fault 3 is a normal fault, the length of the lower inclined shaft 2 is L. 下正 When fault 3 is a reverse fault, the length of the footwall inclined shaft 2 is L. 下逆 The calculation formula is as follows: S4. First, perform fracturing work on the upper inclined shaft 1. For example... Figure 2 and Figure 3As shown, when fault 3 is a normal fault, the lower part of the proposed fracturing zone is level with elevation a1, and the upper part of the proposed fracturing zone extends beyond elevation b1 by a distance ΔL1; when fault 3 is a reverse fault, the upper part of the proposed fracturing zone is level with elevation b1, and the lower part of the proposed fracturing zone extends beyond elevation a1 by a distance ΔL2. The calculation formula is as follows: S5. Asymmetric directional perforation operations were conducted in the planned fracturing area of ​​the upper inclined well 1. The operation process was as follows: First, using surface directional surveying instruments, the spatial relative position of the upper inclined well 1 and the fault plane was accurately obtained; then, the perforating gun was controlled to perforate only within a specific angle range away from fault 3, thereby forming an asymmetric perforation layout on the cross-section of the upper inclined well 1. The main purpose was to guide subsequent fracturing fractures to develop only on the side away from fault 3. Figure 4 As shown, the perforation direction avoids the fault plane and focuses on the simulated fractured surrounding rock zone 120°~180° away from the fault plane.

[0017] S6. In the area to be fractured in the upper inclined well 1, the fracturing fluid is pumped into the upper rock strata of fault 3 using a surface high-pressure pump to form a fracture network in the upper hanging wall, ensuring that the fracturing fluid covers the area to be fractured in the upper inclined well 1.

[0018] S7. Subsequently, fracturing work was carried out on the lower inclined shaft 2. For example... Figure 2 and Figure 3 As shown, when fault 3 is a normal fault, the upper part of the proposed fracturing area is level with elevation b2, and the lower part of the proposed fracturing area extends beyond elevation a2 by a distance ΔL3; when fault 3 is a reverse fault, the lower part of the proposed fracturing area is level with elevation a2, and the upper part of the proposed fracturing area extends beyond elevation b2 by a distance ΔL4. The calculation formula is as follows: S8. Asymmetric directional perforation operations are conducted in the planned fracturing area of ​​the lower inclined well 2. The operation process is as follows: First, using surface directional surveying instruments, the spatial relative position of the lower inclined well 2 and the fault plane is accurately obtained; then, the perforating gun is controlled to perforate only within a specific angle range away from fault 3, thereby forming an asymmetric perforation layout on the cross-section of the lower inclined well 2. The main purpose is to guide subsequent fracturing fractures to develop only on the side away from fault 3. Figure 4 As shown, the perforation direction avoids the fault plane and focuses on the pseudo-fracturing surrounding rock zone 300°~360° away from the fault plane.

[0019] S9. In the area to be fractured in the lower inclined well 2, the fracturing fluid is pumped into the lower rock strata of fault 3 using a surface high-pressure pump to form a fracture network in the lower footing, ensuring that the fracturing fluid covers the area to be fractured in the lower inclined well 2.

[0020] Ultimately, the fracture networks on the lower and upper plates extend longitudinally, overlapping in the spatial stress field to form a complete stress isolation shield enveloping the influence zone of fault 3, thus blocking stress transmission waves. By implementing asymmetric directional perforation and differentiated fracturing, direct penetration and leakage of fracturing fluid into the influence zone of fault 3 can be avoided. Furthermore, through asymmetric directional perforation, fractures develop in a direction away from fault 3. The fracture networks generated by the upper inclined well 1 and lower inclined well 2 produce a shielding effect in the spatial stress field; their thickness covers the width S of the influence zone of fault 3, effectively cutting off stress transmission and thus completing the entire fracturing process.

[0021] Application Example 1 The present invention discloses a method for surface fracturing isolation and scour reduction in a steeply inclined coal seam fault zone. The following description uses a coal mine in Shanxi Province as an example to further illustrate the invention, which is a normal fault.

[0022] ① Obtain basic geological parameters of a coal mine working face in Shanxi Province; among them, b1=1150m, a1=920m, α1=68°, b2=1130m, a2=900m, α2=65°, β=75°, S=35m.

[0023] ② The inclined shaft 1 on the upper plate is parallel to the dip direction of fault 3 and the vertical distance is L=18m.

[0024] ③ The inclined shaft 2 in the lower plate is parallel to the dip direction of fault 3 and the vertical distance D=20m.

[0025] ④ Conduct fracturing work on the upper inclined shaft 1: The horizontal-vertical height difference of the proposed mining area in the upper plate is ΔH1 = b1 - a1 = 1150m - 920m = 230m.

[0026] The distance ΔL1 above the elevation b1 in the upper part of the proposed fracturing area is ΔL1 = S / cosα1 = 35m / cos68° ≈ 93m.

[0027] Upper inclined shaft 1, length L 上正 =ΔH1 / sinβ+ΔL1=230 / sin75°+93m≈331m.

[0028] The planned fracturing zone of the upper inclined shaft 1 ranges from 920m to 1233m.

[0029] ⑥ In the area to be fractured in the upper inclined well 1, the fracturing fluid is pumped into the upper rock strata of fault 3 using a surface high-pressure pump.

[0030] ⑦ Conduct fracturing work on the lower inclined shaft 2: The horizontal-vertical height difference of the proposed mining area in the lower section is ΔH2 = b2 - a2 = 1130m - 900m = 230m.

[0031] The distance ΔL3 from the lower part of the proposed fracturing zone above elevation a2 is ΔL3 = S / cosα2 = 35m / cos65° ≈ 83m.

[0032] Lower inclined shaft 2, length L 下正 =ΔH2 / sinβ+ΔL3=230m / sin75°+83m≈321m.

[0033] The planned fracturing zone of the lower inclined shaft 2 is 807m~1130m.

[0034] ⑧. Conduct asymmetric directional perforation operations in the planned fracturing area of ​​the lower inclined well 2.

[0035] ⑨ In the planned fracturing area of ​​the lower inclined well 2, the fracturing fluid is pumped into the lower rock layer of fault 3 by a surface high-pressure pump, thereby completing the entire fracturing process.

[0036] Application Example 2 The present invention discloses a method for surface fracturing isolation and scour elimination in a steeply inclined coal seam fault zone. The following description uses a coal mine in Shanxi Province as an example to further illustrate the invention, which is a reverse fault.

[0037] ① Obtain basic geological parameters of a coal mine working face in Shanxi Province; among them, b1=1120m, a1=900m, α1=66°, b2=1100m, a2=880m, α2=70°, β=72°, S=32m.

[0038] ② The inclined shaft 1 on the upper plate is parallel to the dip direction of fault 3 and the vertical distance is L=18m.

[0039] ③ The inclined shaft 2 in the lower plate is parallel to the dip direction of fault 3 and the vertical distance D=20m.

[0040] ④ Conduct fracturing work on the upper inclined shaft 1: The horizontal-vertical height difference of the proposed mining area in the upper plate is ΔH1 = b1 - a1 = 1120m - 900m = 220m.

[0041] The distance ΔL2 from the lower part of the proposed fracturing zone on the upper plate to the elevation a1 is ΔL2 = S / cosα1 = 32m / cos66° ≈ 79m.

[0042] Upper inclined shaft 1, length L 上逆 =ΔH1 / sinβ+ΔL2=220m / sin72°+79m≈310m.

[0043] The planned fracturing zone of the upper inclined shaft 1 ranges from 821m to 1120m.

[0044] ⑤ Conduct asymmetric directional perforation operations in the planned fracturing area of ​​the upper inclined well 1.

[0045] ⑥ In the area to be fractured in the upper inclined well 1, the fracturing fluid is pumped into the upper rock strata of fault 3 using a surface high-pressure pump.

[0046] ⑦ Conduct fracturing work on the lower inclined shaft 2: The horizontal-vertical height difference of the proposed mining area in the lower section is ΔH2 = b2 - a2 = 1100m - 880m = 220m.

[0047] The distance ΔL4 above the elevation b2 in the upper part of the proposed fracturing area of ​​the lower plate is ΔL4 = S / cosα2 = 32m / cos70° ≈ 94m.

[0048] Lower inclined shaft 2, length L 下逆 =ΔH2 / sinβ+ΔL4 =220m / sin72°+94m≈325m.

[0049] The planned fracturing zone of the lower inclined shaft 2 is 880m~1194m.

[0050] ⑧. Conduct asymmetric directional perforation operations in the planned fracturing area of ​​the lower inclined well 2.

[0051] ⑨ In the planned fracturing area of ​​the lower inclined well 2, the fracturing fluid is pumped into the lower rock layer of fault 3 by a surface high-pressure pump, thereby completing the entire fracturing process.

[0052] The present embodiment has now been described in detail with reference to the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the present invention. Of course, the above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the content of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention and should be protected by the present invention.

Claims

1. A method for surface fracturing isolation and scour reduction in steeply inclined coal seam fault zones, characterized in that, Includes the following steps: S1. Obtain the geological parameters of the working face, including the upper and lower horizontal elevations of the proposed mining area of ​​the steeply dipping coal seam on the footwall of the fault as b1 and a1, respectively, and the dip angle of the coal seam as α1; the upper and lower horizontal elevations of the proposed mining area of ​​the steeply dipping coal seam on the footwall of the fault as b2 and a2, respectively, and the dip angle of the coal seam as α2; the dip angle of the fault as β; and define the width of the fault influence zone as S. S2. Based on the geological parameters of the working face obtained in S1, drill downwards from the ground to arrange the upper and lower inclined shafts; The specific operation for setting up the upper inclined shaft is as follows: Drilling proceeds downwards from the ground, with the upper inclined shaft positioned above the fault and parallel to the fault's dip direction; When the fault is a normal fault, the length of the inclined shaft in the hanging wall is L. 上正 , ; When the fault is a reverse fault, the length of the inclined shaft in the hanging wall is L. 上逆 , ; The specific operation for setting up the lower inclined shaft is as follows: Drilling proceeds downwards from the ground, with the lower inclined shaft positioned below the fault and parallel to the fault's dip direction; When the fault is a normal fault, the length of the inclined shaft in the footwall is L. 下正 , ; When the fault is a reverse fault, the length of the footwall inclined shaft is L. 下逆 , ; S3. Carry out fracturing work on the hanging wall of the inclined well. Perform asymmetric directional perforation in the area to be fracturing in the hanging wall of the inclined well. The perforation direction is 120°~180° away from the fault plane. The fracturing fluid is pumped into the hanging wall of the fault through a surface high-pressure pump. S4. Perform fracturing work on the lower plate of the inclined well. In the area to be fracturing in the lower plate of the inclined well, perform asymmetric directional perforation operations. The perforation direction is 300°~360° away from the fault plane. The fracturing fluid is pumped into the rock strata on the lower plate of the fault through a surface high-pressure pump to complete the entire fracturing process.

2. The method for surface fracturing isolation and scour reduction in a steeply inclined coal seam fault zone according to claim 1, characterized in that, The specific operation of fracturing the upper inclined well described in step S3 is as follows: When the fault is a normal fault, the lower part of the simulated fracturing zone is level with the lower elevation a1, and the upper part of the simulated fracturing zone extends beyond the upper elevation b1 by a distance ΔL1. ; When the fault is a reverse fault, the upper part of the simulated fracturing zone is level with the upper elevation b1, and the lower part of the simulated fracturing zone extends beyond the lower elevation a1 by a distance ΔL2. .

3. The method for surface fracturing isolation and scour reduction in a steeply inclined coal seam fault zone according to claim 1, characterized in that, The specific operation of fracturing the lower side of the inclined well as described in step S4 is as follows: When the fault is a normal fault, the upper part of the simulated fracturing zone is level with the upper elevation b2, and the lower part of the simulated fracturing zone extends beyond the lower elevation a2 by a distance ΔL3. ; When the fault is a reverse fault, the lower part of the simulated fracturing zone is level with the lower elevation a2, and the upper part of the simulated fracturing zone extends beyond the upper elevation b2 by a distance ΔL4. .

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