Multi-dimensional pressure relief method for hydraulic fracturing of top plate

Abstract

The invention belongs to the technical field of coal mine underground hydraulic fracturing, relates to a top plate hydraulic fracturing multi-dimensional pressure relief method, provides a technical scheme of combining top plate directional long drill hole staged hydraulic fracturing with conventional shallow hole staged hydraulic fracturing, and provides specific implementation steps. Through the cooperative arrangement of the directional long drill holes, the open-off cut short holes, the air return crossheading short holes and the transportation crossheading short holes, the coverage areas of the two hydraulic fracturing technologies complement each other, cooperate with each other and do not affect each other. The directional long drill holes are used for conducting hydraulic fracturing on the interior of the working face, the problem that conventional straight drill holes cannot cover the interior of the working face in a large range is solved, the conventional straight drill holes are used for forming short holes in the roadway and the open-off cut, regionalization weakening of the working face is assisted, effective combination of the short holes and the short holes is achieved in the drill hole space position, and the working face weakening efficiency is improved. And therefore, full coverage of the working face is realized, and the periodic weighting step pitch and the periodic weighting impact strength can be effectively reduced.

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 weakening, unloading and preventing impacts on thick and hard roof slabs. It includes conventional shallow-hole hydraulic fracturing and directional long-borehole segmented hydraulic fracturing technology. Conventional shallow-hole hydraulic fracturing has a small control range but precise control, which is suitable for roof cutting and unloading near the auxiliary tunnels of the working face. Directional long-borehole segmented hydraulic fracturing has a wide coverage range and is suitable for large-scale and long-distance weakening and unloading of the roof slab above the working face.

[0003] Due to the limitations of the above-mentioned technologies, the existing conventional short-hole hydraulic fracturing technology is generally used for roof cutting and pressure relief near the tunnel. The drilling length is short, generally from the tunnel construction to the key layer, the actual fracturing section is in the key layer, and the drilling utilization rate is low. Especially when the oblique drilling is inside the control working surface, 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 opening position, 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 control, and is not suitable 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-borehole 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, the working face width B, the coal seam thickness h, the tunnel height s, the 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 Pugh 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 used for constructing directional long drilling holes, n = L / L1, and round it to an integer, L1 is the drilling length that matches the Puerto Rico hardness coefficient f of the target roof layer, L1 is taken according to the Puerto Rico 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, taking the eye cutting as the reference, a drilling site for constructing a directional long borehole is designed at a distance of L1 at each interval, and a directional long borehole facing the eye cutting 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, when B<200m, M=3, and the distance between the directional long borehole and the coal seam is H, H=g+k / 2, the distances between the directional long boreholes closest to both sides and the transport chute and the return air chute are 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 cutting and the eye cutting is a, and a=30m;

[0012] Step 5: Use a fracture pressure P greater than the target top layer 破 The directional long boreholes are hydraulically fractured with a pressure of , and 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: construct a short hole with a spacing of b in the eye cutting, where b=4s, and control the angle between the short hole and the coal seam to be 60°. The length of the short hole is L2, where L2=arcsin60°*(h-s+g+k);

[0014] Step 7: constructing short holes of the transport channel with a spacing of C in the transport channel, where C=4s+k, controlling the angle between the short hole of the transport channel and the coal seam to be 60° and forming an angle of 60° with the transport channel in the direction of the eye cutting, and the length of the short hole of the transport channel is L3;

[0015]

[0016] Step 8: construct short return air chute holes with a spacing of C in the return air chute, control the included angle between the short return air chute holes and the coal seam to be 60°, and form an included angle of 60° with the return air chute in the direction of 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 short hole of the cut eye, the short hole of the return air chute and the short hole of the transport chute are hydraulically fractured with a pressure of , and the fracturing sequence of the short hole of the cut eye, the short hole of the return air chute and the short hole of the transport chute is: short hole of the cut eye - short hole of the return air chute - short hole of the transport chute.

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

[0020] Two packers and a pressure-conducting screen are combined and connected to the fracturing string, and the fracturing string is clamped by a directional long-hole drilling rig and pushed to the bottom of the directional long-hole. The directional long-hole drilling rig is also connected to a fracturing pump group and a water tank. A fracturing pressure greater than the target roof layer P is used. 破 Hydraulic fracturing is carried out with pressure of , 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-conducting 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 fracturing pressure greater than the target roof layer 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 inside 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 position control is precise, so that the weakening of the coal seam roof of the working face can be covered on a large scale, which solves the problem that conventional straight drilling holes cannot cover the inside of the working face on a large scale. In addition, the directional long drilling hole adopts segmented hydraulic fracturing to improve the utilization rate of the directional long drilling hole. At the same time, the present invention 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 realizing full coverage of the working face, and can effectively reduce the periodic pressure step distance and the periodic pressure impact strength.

[0024] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can 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 in conjunction with the accompanying drawings, wherein:

[0026] Figure 1 It is a three-dimensional schematic diagram of the arrangement of hydraulic fracturing drilling holes on the working face in the present invention;

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

[0028] Figure 3 It is a schematic diagram of section II of the hydraulic fracturing drilling arrangement of the working face in the present invention;

[0029] Figure 4 It is a schematic diagram of the II-II cross-section of the hydraulic fracturing drilling arrangement of the working face in the present invention;

[0030] Figure 5 It is a process schematic diagram of directional long-hole staged hydraulic fracturing of the top plate of the working face in the present invention;

[0031] Figure 6 It 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 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 only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

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

[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 the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position 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 Figure 1 to Figure 6 , which is a multi-dimensional pressure relief method for roof hydraulic fracturing, and the specific implementation steps are as follows:

[0037] Step 1: Obtain the working face length L, the working face width B, the coal seam thickness h, the coal seam inclination α, the tunnel height s, the 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 construction, n = L / L1, and round it to an integer, L1 is the drilling length that matches the Puerto Rico hardness coefficient f of the target roof layer, L1 is taken according to the Puerto Rico hardness coefficient f of the target roof layer, L1 = (800m, f>10; 600m, 5≤f≤10; 400m, f<5);

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

[0042] The fracturing method is as follows: two packers 6 and a pressure-conducting 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 a 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 top plate layer is used. 破 Fracturing is performed with pressure of 10 ...

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

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

[0045]

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

[0047]

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

[0049] Two packers 6 and pressure screens 7 are combined and connected to the fracturing string 5, and the fracturing string 5 is clamped by a short hole drill 11 and pushed to the bottom of the hole. The short hole drill 11 is connected to the fracturing pump group 9 and the water tank 8. The fracturing pressure P greater than the target top plate layer is used. 破 fracturing at pressure.

[0050] This embodiment proposes a technical solution of combining directional long-hole segmented hydraulic fracturing of the roof with conventional shallow-hole segmented hydraulic fracturing, and proposes specific implementation steps. Through the coordinated arrangement of directional long 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 solution of the present invention rather than to limit it. 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 solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should 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, the working face width B, the coal seam thickness h, the tunnel height s, the 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 Pugh 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 used for constructing directional long drilling holes, n = L / L1, and round it to an integer, L1 is the drilling length that matches the Puerto Rico hardness coefficient f of the target roof layer, L1 is taken according to the Puerto Rico 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, taking the eye cutting as the reference, a drilling site for constructing a directional long borehole is designed at a distance of L1 at each interval, and a directional long borehole facing the eye cutting 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, when B<200m, M=3, and the distance between the directional long borehole and the coal seam is H, H=g+k / 2, the distances between the directional long boreholes closest to both sides and the transport chute and the return air chute are 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 cutting and the eye cutting is a, and a=30m; Step 5: Use a fracture pressure P greater than the target top layer 破 The directional long boreholes are hydraulically fractured with a pressure of , and 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: construct a short hole with a spacing of b in the eye cutting, where b=4s, and control the angle between the short hole and the coal seam to be 60°. The length of the short hole is L2, where L2=arcsin60°*(h-s+g+k); Step 7: constructing short holes of the transport channel with a spacing of C in the transport channel, where C=4s+k, controlling the angle between the short hole of the transport channel and the coal seam to be 60° and forming an angle of 60° with the transport channel in the direction of the eye cutting, and the length of the short hole of the transport channel is L3; Step 8: construct short return air chute holes with a spacing of C in the return air chute, control the included angle between the short return air chute holes and the coal seam to be 60°, and form an included angle of 60° with the return air chute in the direction of 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 short hole of the cut eye, the short hole of the return air chute and the short hole of the transport chute are hydraulically fractured with a pressure of , and the fracturing sequence of the short hole of the cut eye, the short hole of the return air chute and the short hole of the transport chute is: short hole of the cut eye - short hole of the return air chute - short hole of the transport chute.

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: Two packers and a pressure-conducting screen are combined and connected to the fracturing string, and the fracturing string is clamped by a directional long-hole drilling rig and pushed to the bottom of the directional long-hole. The directional long-hole drilling rig is also connected to a fracturing pump group and a water tank. A fracturing pressure greater than the target roof layer P is used. 破 Hydraulic fracturing is carried out with pressure of , 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: using two packers and a pressure-conducting 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 fracture pressure greater than the target roof layer 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

Images