Multi-dimensional pressure relief method for roof hydraulic fracturing

Abstract

The present invention belongs to the technical field of hydraulic fracturing in coal mines, and relates to a multi-dimensional pressure relief method for roof hydraulic fracturing. It proposes a technical solution for roof directional long-hole segmented hydraulic fracturing combined with conventional shallow-hole segmented hydraulic fracturing, and proposes specific implementation steps. By coordinating the arrangement of directional long-hole drilling with short holes for cutting eyes, short holes for return air chute, and short holes for transport chute, the coverage areas of the two hydraulic fracturing technologies complement each other, cooperate with each other, and do not affect each other. The present invention uses directional long-hole drilling to hydraulically fracture the interior of the working face, which solves the problem that conventional straight-hole drilling cannot cover the interior of the working face on a large scale. Conventional straight-hole drilling is used to form short holes in the tunnel and the cutting eyes to assist in regional weakening of the working face. The two are effectively combined in the spatial position of the drilling holes, thereby achieving full coverage of the working face, which can effectively reduce the periodic pressure step distance and the periodic pressure impact intensity.

Description

Technical Field

[0001] The invention belongs to the technical field of hydraulic fracturing in coal mines, and relates to a multi-dimensional pressure relief method for hydraulic fracturing of a roof. Background Art

[0002] Hydraulic fracturing in underground coal mines has been applied to the weakening, unloading and anti-blowout of thick and hard roofs. It includes conventional shallow-hole hydraulic fracturing and directional long-hole segmented hydraulic fracturing technology. Conventional shallow-hole hydraulic fracturing has a small control range but precise control, which is suitable for cutting and unloading the roof near the auxiliary tunnels of the working face, while directional long-hole segmented hydraulic fracturing has a wide coverage range and is suitable for large-scale and long-distance weakening and unloading of the roof above the working face.

[0003] Due to the limitations of the above-mentioned technologies, existing conventional short-hole hydraulic fracturing technology is generally used for roof cutting and pressure relief near the tunnel. The drilling length is relatively short, generally from the tunnel to the key layer, and the actual fracturing section is within the key layer, resulting in low drilling utilization. Especially when oblique drilling is carried out inside the control working face, the drilling distance is longer, the utilization rate is lower, and the drilling is easy to deviate. The directional long-hole segmented fracturing technology has a flexible hole location, which can realize steering drilling and directional drilling in the key layer. The drilling utilization rate is high and can achieve large-scale fracturing and weakening of the roof. However, fracturing near the tunnel will affect the safety of the tunnel, and the actual roof hanging near the two tunnels will be more serious. Therefore, other technologies are needed to supplement it. In addition, the existing pyrotechnic blasting pressure relief method has low safety and strict management and control, making it unsuitable as a supplementary means.

[0004] Therefore, the present application proposes a technical solution of combining roof directional long-hole segmented hydraulic fracturing with conventional shallow-hole segmented hydraulic fracturing to achieve full coverage of the entire working face. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a multi-dimensional pressure relief method for roof hydraulic fracturing, which combines directional long-hole segmented hydraulic fracturing with conventional shallow-hole segmented hydraulic fracturing to achieve full coverage of the entire working face.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A multi-dimensional pressure relief method for roof hydraulic fracturing, comprising the following steps:

[0008] Step 1: Obtain the working face length L, working face width B, coal seam thickness h, roadway height s, target roof layer thickness k, and the distance g between the target roof layer and the coal seam;

[0009] Step 2: Determine the target roof layer, obtain the Proctor hardness coefficient f of the target roof layer, the rupture pressure P of the target roof layer 破 ;

[0010] Step 3: Calculate the number of drilling sites n for constructing directional long drilling holes, n = L / L1, and round it to the nearest integer. L1 is the drilling length that matches the Proctor hardness coefficient f of the target roof layer. L1 is determined based on the Proctor hardness coefficient f of the target roof layer. When f>10, L1=800m; when 5≤f≤10, L1=600m; when f<5, L1=400m.

[0011] Step 4: In the return air chute of the working face, with the eye cut as the benchmark, a drilling site for constructing a directional long borehole is designed at every interval L1. A directional long borehole facing the eye cut direction is designed in each drilling site, and the number of directional long boreholes in each drilling site is M, and the value of M is determined according to the width B of the working face. When B>300m, M=5, when 300m≤B≤200m, M=4, and when B<200m, M=3. The distance between the directional long borehole and the coal seam is H, H=g+k / 2, and the distance between the directional long boreholes closest to both sides and the transport chute and the return air chute is d, and d=30m. The distance between two adjacent directional long boreholes is e, and e=(B-2d) / (M-1). The distance between the end point of the directional long borehole constructed in the drilling site closest to the eye cut and the eye cut is a, and a=30m.

[0012] Step 5: Use a fracture pressure P greater than the target roof layer 破 The directional long boreholes are hydraulically fractured with a pressure of 1000 s. The fracturing order of the directional long boreholes is: the two directional long boreholes closest to the transport chute and the return air chute - the middle directional long borehole;

[0013] Step 6: constructing short holes with a spacing of b in the cut, where b=4s, and controlling the angle between the short holes and the coal seam to be 60°. The length of the short holes is L2, where L2=arcsin60°*(h-s+g+k);

[0014] Step 7: construct short holes in the transport chute with a spacing of C, where C = 4s + k. The angle between the short holes and the coal seam is controlled to be 60°, and the angle between the short holes and the transport chute is also 60° in the direction of the eye cutting. The length of the short holes is L3.

[0015]

[0016] Step 8: construct short return air chute holes with a spacing of C in the return air chute, control the angle between the short return air chute holes and the coal seam to be 60°, and form a 60° angle with the return air chute in the direction of the eye cutting, and the length of the short return air chute holes is L4;

[0017]

[0018] Step 9: Use a fracture pressure P greater than the target top layer破 The pressure of the cut eye short hole, the return air chute short hole and the transport chute short hole is used to hydraulically fracture the cut eye short hole, and the fracturing order of the cut eye short hole, the return air chute short hole and the transport chute short hole is: cut eye short hole - return air chute short hole - transport chute short hole.

[0019] Furthermore, the method for hydraulic fracturing the directional long borehole in step 5 is:

[0020] Use two packers and a pressure screen to combine and connect the fracturing string, use a directional long hole drilling rig to clamp the fracturing string and push it to the bottom of the directional long hole, and the directional long hole drilling rig is also connected to the fracturing pump group and the water tank, use a fracture pressure greater than the target roof layer P 破 Hydraulic fracturing is carried out with the help of pressure and multi-stage fracturing is carried out by step-by-step retreat.

[0021] Furthermore, the method for hydraulic fracturing the short hole of the cut eye, the short hole of the return air chute and the short hole of the transport chute in step 9 is: using two packers and a pressure screen combination and connecting a fracturing string, using a short hole drill to clamp the fracturing string and push it to the bottom of the short hole of the cut eye, the short hole of the return air chute or the short hole of the transport chute, and the short hole drill is also connected to a fracturing pump group and a water tank, using a pressure greater than the target roof layer fracture pressure P 破 The cut-eye short hole, the return air chute short hole and the transport chute short hole are hydraulically fractured in sequence with a pressure of

[0022] The beneficial effects of the present invention are:

[0023] The present invention adopts directional long drilling to carry out hydraulic fracturing on the interior of the working face. Since the directional long drilling hole is long and the construction hole opening position is less restricted, the steering control can be realized in the hole and the layer control is precise, thereby achieving large-scale coverage of the weakened coal seam roof of the working face, solving the problem that conventional straight drilling holes cannot cover the interior of the working face on a large scale, and the directional long drilling hole adopts segmented hydraulic fracturing to improve the utilization rate of the directional long drilling hole; the present invention also adopts conventional straight drilling holes to form short holes in the tunnel (return air chute and transport chute) and the cutting eye. Since the short holes are denser and more precise, precise cutting top control can be realized to assist in regional weakening of the working face. The two are effectively combined in the spatial position of the drilling hole, thereby achieving full coverage of the working face, and can effectively reduce the periodic pressure step distance and the periodic pressure impact intensity.

[0024] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0026] Figure 1 A three-dimensional schematic diagram of the hydraulic fracturing drilling arrangement of the working face in the present invention;

[0027] Figure 2 It is a plan view of the hydraulic fracturing drilling arrangement of the working face in the present invention;

[0028] Figure 3 Schematic diagram of section II of the hydraulic fracturing drilling arrangement on the working face of the present invention;

[0029] Figure 4 Schematic diagram of the II-II cross-section of the hydraulic fracturing drilling arrangement on the working face in the present invention;

[0030] Figure 5 Schematic diagram of the process of directional long-hole segmented hydraulic fracturing of the working face roof in the present invention;

[0031] Figure 6 This is a schematic diagram of the process of hydraulic fracturing with short boreholes on the top plate of the working face in the present invention.

[0032] Figure numerals: 1-directional long drilling hole; 2-return air chute short hole; 3-eye cutting short hole; 4-transport chute short hole; 5-fracturing string; 6-packer; 7-pressure screen; 8-water tank; 9-fracturing pump group; 10-directional long drilling rig; 11-short hole drilling rig. DETAILED DESCRIPTION

[0033] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0034] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0035] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "back", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0036] See also Figures 1 to 6 , which is a multi-dimensional pressure relief method for roof hydraulic fracturing. The specific implementation steps are as follows:

[0037] Step 1: Obtain the working face length L, working face width B, coal seam thickness h, coal seam inclination α, roadway height s, target roof layer thickness k to be fractured, and the distance g between the target roof layer and the coal seam;

[0038] Step 2: Determine the target roof layer, obtain the Pugh hardness coefficient f of the target roof layer, the rupture pressure P of the target roof layer 破 ;

[0039] Step 3: Calculate the number of drilling sites n for directional long drilling, where n = L / L1, and round it to the nearest integer. L1 is the drilling length that matches the Proctor hardness coefficient f of the target roof layer. L1 is determined based on the Proctor hardness coefficient f of the target roof layer, where L1 = (800 m, f > 10; 600 m, 5 ≤ f ≤ 10; 400 m, f < 5).

[0040] Step 4: In the return air chute of the working face, with the cut eye as the benchmark, design a directional long drilling construction drilling site at every interval of L / n(L1), design a directional long drill hole 1 facing the cut eye direction in each drilling site, the number of directional long drill holes is M, M is determined according to the width of the working face B, M=(5, B>300m; 4, 300m≤B≤200m; 3, B<200m;), the distance between the directional long drill hole 1 and the coal seam is H, H=g+k / 2, the distance between the directional long drill holes 1 on the two sides and the transport chute and the return air chute is d, d=30m, the spacing between the directional long drill holes is e, e=(B-2d) / (M-1), the distance between the end point of the directional long drill hole 1 constructed in the drilling site closest to the cut eye and the cut eye is a, a=30m;

[0041] Step 5: Use a fracture pressure P greater than the target roof layer 破The directional long borehole 1 is fractured with a pressure of , and the order of fracturing the directional long boreholes is: the two directional long boreholes closest to the transport chute and the return air chute - the middle directional long borehole (i.e., fracturing is carried out from both sides toward the middle);

[0042] The fracturing method is as follows: two packers 6 and a pressure screen 7 are combined and connected to a fracturing string 5, and a directional long hole drilling rig 10 is used to clamp the fracturing string 5 and push it to the bottom of the directional long hole 1. The directional long hole drilling rig 10 is connected to a fracturing pump group 9 and a water tank 8, and a fracturing pressure greater than the target roof layer is used. 破 Fracturing is performed with a pressure of 10000 psi and multiple stages of fracturing are performed step by step.

[0043] Step 6: construct a short hole 3 with a spacing of b in the cut, where b = 4s. The angle between the short hole 3 and the coal seam is 60°. The length of the short hole 3 is L2, where L2 = arcsin60°*(h-s+g+k).

[0044] Step 7: construct a short transport channel hole 4 with a spacing of b in the transport channel, C = 4s + k, the angle between the short transport channel hole 4 and the coal seam is 60 degrees, and the angle between the short transport channel hole 4 and the transport channel is 60 degrees in the direction of the eye cutting. The length of the short transport channel hole is L3;

[0045]

[0046] Step 8: Construct short holes 2 of the return air chute with a spacing of b in the return air chute, C = 4s + k, the angle between the short holes 2 and the coal seam is 60 degrees, and the angle between the short holes 2 and the return air chute is 60 degrees in the direction of the cutting eye, and the drilling length is L4;

[0047]

[0048] Step 9: Start fracturing the cut-eye short hole, return air chute short hole and transport chute short hole. The fracturing order of the cut-eye short hole, return air chute short hole and transport chute short hole is: cut-eye short hole - return air chute short hole - transport chute short hole.

[0049] Use two packers 6 and pressure screen 7 to combine and connect the fracturing string 5, use the short hole drill 11 to clamp the fracturing string 5 and push it to the bottom of the hole, and the short hole drill 11 is connected to the fracturing pump group 9 and the water tank 8, use a pressure greater than the target roof layer fracture pressure P 破 fracturing at high pressure.

[0050] This embodiment proposes a technical solution of roof directional long drilling segmented hydraulic fracturing combined with conventional shallow hole segmented hydraulic fracturing, and puts forward specific implementation steps. Through the coordinated arrangement of directional long drilling holes with short holes for cutting eyes, short holes for return air chute and short holes for transport chute, the coverage areas of the two hydraulic fracturing technologies complement each other, cooperate with each other and do not affect each other, thereby achieving full coverage of hydraulic fracturing of the entire working face roof. The operating steps and design methods are highly consistent with the actual situation underground in coal mines, have strong operability, and the drilling design fully considers safety issues.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A multi-dimensional pressure relief method for roof hydraulic fracturing, characterized in that: The following steps are involved: Step 1: Obtain the working face length L, working face width B, coal seam thickness h, roadway height s, target roof layer thickness k, and the distance g between the target roof layer and the coal seam; Step 2: Determine the target roof layer, obtain the Proctor hardness coefficient f of the target roof layer, the rupture pressure P of the target roof layer 破 ; Step 3: Calculate the number of drilling sites n for constructing directional long drilling holes, n = L / L1, and round it to the nearest integer. L1 is the drilling length that matches the Proctor hardness coefficient f of the target roof layer. L1 is determined based on the Proctor hardness coefficient f of the target roof layer. When f>10, L1=800m; when 5≤f≤10, L1=600m; when f<5, L1=400m. Step 4: In the return air chute of the working face, with the eye cut as the benchmark, a drilling site for constructing a directional long borehole is designed at every interval L1. A directional long borehole facing the eye cut direction is designed in each drilling site, and the number of directional long boreholes in each drilling site is M, and the value of M is determined according to the width B of the working face. When B>300m, M=5, when 300m≤B≤200m, M=4, and when B<200m, M=3. The distance between the directional long borehole and the coal seam is H, H=g+k / 2, and the distance between the directional long boreholes closest to both sides and the transport chute and the return air chute is d, and d=30m. The distance between two adjacent directional long boreholes is e, and e=(B-2d) / (M-1). The distance between the end point of the directional long borehole constructed in the drilling site closest to the eye cut and the eye cut is a, and a=30m. Step 5: Use a fracture pressure P greater than the target roof layer 破 The directional long boreholes are hydraulically fractured with a pressure of 1000 s. The fracturing order of the directional long boreholes is: the two directional long boreholes closest to the transport chute and the return air chute - the middle directional long borehole; Step 6: constructing short holes with a spacing of b in the cut, where b=4s, and controlling the angle between the short holes and the coal seam to be 60°. The length of the short holes is L2, where L2=arcsin60°*(h-s+g+k); Step 7: construct short holes in the transport chute with a spacing of C, where C = 4s + k. The angle between the short holes and the coal seam is controlled to be 60°, and the angle between the short holes and the transport chute is also 60° in the direction of the eye cutting. The length of the short holes is L3. Step 8: construct short return air chute holes with a spacing of C in the return air chute, control the angle between the short return air chute holes and the coal seam to be 60°, and form a 60° angle with the return air chute in the direction of the eye cutting, and the length of the short return air chute holes is L4; Step 9: Use a fracture pressure P greater than the target top layer 破 The pressure of the cut eye short hole, the return air chute short hole and the transport chute short hole is used to hydraulically fracture the cut eye short hole, and the fracturing order of the cut eye short hole, the return air chute short hole and the transport chute short hole is: cut eye short hole - return air chute short hole - transport chute short hole.

2. The multi-dimensional pressure relief method for roof hydraulic fracturing according to claim 1, characterized in that: The method for hydraulic fracturing the directional long borehole in step 5 is: Use two packers and a pressure screen to combine and connect the fracturing string, use a directional long hole drilling rig to clamp the fracturing string and push it to the bottom of the directional long hole, and the directional long hole drilling rig is also connected to the fracturing pump group and the water tank, use a fracture pressure greater than the target roof layer P 破 Hydraulic fracturing is carried out with the help of pressure and multi-stage fracturing is carried out by step-by-step retreat.

3. The multi-dimensional pressure relief method for roof hydraulic fracturing according to claim 1, characterized in that: The method for hydraulic fracturing the short hole of the cut eye, the short hole of the return air chute and the short hole of the transport chute in step 9 is as follows: using two packers and a pressure screen combination and connecting the fracturing string, using a short hole drill to clamp the fracturing string and push it to the bottom of the short hole of the cut eye, the short hole of the return air chute or the short hole of the transport chute, and the short hole drill is also connected to a fracturing pump group and a water tank, using a pressure greater than the target roof layer fracture pressure P 破 The cut-eye short hole, the return air chute short hole and the transport chute short hole are hydraulically fractured in sequence with a pressure of

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