Crack generation method and device, electronic equipment and storage medium

Abstract

The invention provides a crack generation method and device, electronic equipment and a storage medium, and relates to the technical field of coal mine hard roof strong mine pressure disaster prevention and control. The method comprises the following steps: arranging drill holes according to the direction of the minimum principal stress of the hard roof; first staged fracturing is conducted in the drill hole according to a preset staged fracturing interval, a parallel crack set perpendicular to the minimum principal stress direction is obtained in combination with mixed fracturing fluid, the mixed fracturing fluid comprises a propping agent, and induced stress exists in the preset staged fracturing interval; second fracturing segmentation is carried out in the middle area of every two adjacent parallel cracks in the parallel crack group, a steering crack between every two adjacent parallel cracks is obtained in combination with fracturing fluid, the steering crack intersects with the extension line of every two adjacent parallel cracks in the crack direction of the steering crack, and a second fracturing segment is obtained; the expansion orientation of the crack is changed based on the induced stress to generate the steering crack, the complexity and connectivity of a crack network are enhanced, and the cracking weakening and caving effects of the hard roof are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of prevention and control of strong mine pressure disasters on hard roofs of coal mines, and in particular to a crack generation method, device, electronic equipment and storage medium. Background Art

[0002] The occurrence conditions of coal seams in my country are complex. The hard roof is easy to induce disasters such as large deformation of high-stress tunnels, impact ground pressure, and strong mine pressure on the working face during coal mining due to its high hardness, large thickness, good integrity and strong bearing capacity. Conventional blasting and roof caving methods have problems such as small coverage area, large engineering volume, high cost, and easy production of toxic and harmful gases. Therefore, related technologies have developed hydraulic fracturing technology for hard roofs of coal mines as a safe, green and economical means of preventing and controlling strong mine pressure disasters. This technology uses a drill to drill directly from the tunnel to the target rock layer for segmented hydraulic fracturing, destroying the integrity of the rock mass, achieving stress transfer or reduction, and protecting the tunnel and working face support structures and operators.

[0003] In the related technology, the hydraulic fracturing technology for the hard roof of coal mines underground releases the energy accumulated in the rock formation by pressing cracks in the intact rock formation. However, due to the constraint of ground stress, the cracks in the deep rock mass generally expand perpendicular to the direction of the minimum principal stress. The local auxiliary measures around the borehole, such as mechanical and jet cutting, have a short depth of cutting the guide seam, generally less than 1m. It is difficult to effectively control the direction of crack expansion in the deep rock mass. After the cracks expand along the guide seam, they turn to expand in a plane perpendicular to the direction of the minimum principal stress. The generated cracks are mostly parallel, and it is difficult to form a three-dimensional seam network that is staggered horizontally and vertically. In addition, the borehole used for fracturing the rock formation of the coal mine roof is an upward hole. After the fracturing is completed, the fracturing fluid is returned in large quantities under the action of gravity. The high-pressure water cannot play a normal supporting role. The cracks tend to close under the action of ground stress, resulting in a weak stress shadow effect and a limited degree of crack weakening of the hard roof. Summary of the invention

[0004] The present disclosure provides a crack generation method, device, electronic device and storage medium to solve the problems in the related art. By arranging drill holes according to the minimum principal stress direction of the hard roof, and performing the first staged fracturing according to the preset staged fracturing spacing, a parallel crack group perpendicular to the minimum principal stress direction is formed, and then the expansion direction of the crack is changed based on the induced stress shadow effect in the preset staged fracturing spacing, and a turning crack is induced in the middle area of ​​adjacent parallel cracks, so as to further realize the complexity of the crack network and enhance the connectivity, and effectively improve the fracturing weakening and collapse effect of the hard roof.

[0005] A first aspect of the present disclosure provides a crack generation method, comprising:

[0006] Arrange the drill holes according to the direction of the minimum principal stress of the hard roof;

[0007] Performing a first staged fracturing in the borehole according to a preset staged fracturing spacing, combining with a mixed fracturing fluid to obtain a parallel fracture group, wherein the mixed fracturing fluid includes a proppant, and the parallel fracture group includes a plurality of parallel fractures parallel to each other, the fracture directions of the parallel fractures are perpendicular to the direction of the minimum principal stress, and there is an induced stress within the preset staged fracturing spacing;

[0008] The second fracturing segment is carried out in the middle area of ​​every two adjacent parallel fractures in the parallel fracture group, and combined with the fracturing fluid, a diverted fracture between every two adjacent parallel fractures is obtained, and the diverted fracture intersects with the extension line of every two adjacent parallel fractures along the fracture direction of the diverted fracture.

[0009] In some embodiments, the method includes: arranging the boreholes according to the direction of the minimum principal stress among the three-dimensional ground stress of the hard roof;

[0010] Determine the minimum principal stress in the rigid roof and the direction of the minimum principal stress;

[0011] According to the direction of the minimum principal stress, the drilling trajectory is determined, and the drilling holes are arranged according to the drilling trajectory, and the drilling holes are parallel to the direction of the minimum principal stress.

[0012] In some embodiments, determining the minimum principal stress of the rigid roof and the direction of the minimum principal stress includes:

[0013] Through the hydraulic fracturing ground stress measurement method, the magnitude and direction of the three-dimensional ground stress are determined respectively;

[0014] Compare the magnitude of each geostress in the three-dimensional geostress, determine the geostress with the smallest geostress as the minimum principal stress, and take the direction of the geostress with the smallest geostress as the direction of the minimum principal stress.

[0015] In some embodiments, before performing a first staged fracturing in a borehole according to a preset staged fracturing spacing and combining a mixed fracturing fluid to obtain a parallel fracture set, the method includes:

[0016] According to the induced stress algorithm, the preset segmented fracturing spacing is determined, and the superimposed induced stress between adjacent parallel cracks corresponding to the preset segmented fracturing spacing is greater than the second principal stress, and the second principal stress is the ground stress greater than the minimum principal stress among the three-dimensional ground stresses.

[0017] In some embodiments, a second fracturing stage is performed in the middle region of every two adjacent parallel fractures in the parallel fracture group, and a fracturing fluid is combined to obtain a diverted fracture between every two adjacent parallel fractures, including:

[0018] According to the staged backward fracturing sequence, the second fracturing stage is sequentially performed in the middle area of ​​every two adjacent parallel fractures in the parallel fracture group, and combined with the fracturing fluid, a diverted fracture between every two adjacent parallel fractures is obtained.

[0019] In some embodiments, according to the staged retreat fracturing sequence, the second fracturing stage is sequentially performed in the middle region of every two adjacent parallel fractures in the parallel fracture group, and combined with the fracturing fluid to obtain a diverted fracture between every two adjacent parallel fractures, including:

[0020] Performing a second fracturing segmentation in the middle region of the first parallel fracture and the second parallel fracture in the parallel fracture group, combining with the fracturing fluid, to obtain a diverting fracture between the first parallel fracture and the second parallel fracture, wherein the first parallel fracture is adjacent to the second parallel fracture;

[0021] A second fracturing segment is performed in the middle region of the second parallel fracture and the third parallel fracture in the parallel fracture group, and a diverting fracture between the second parallel fracture and the third parallel fracture is obtained by combining the fracturing fluid, and the second parallel fracture is adjacent to the third parallel fracture.

[0022] In some embodiments, a second fracturing stage is performed in the middle region of every two adjacent parallel fractures in the parallel fracture group, and a fracturing fluid is combined to obtain a diverted fracture between every two adjacent parallel fractures. Thereafter, the method includes:

[0023] The diverting cracks are connected with every two adjacent parallel cracks to obtain a staggered crack group, which can be used to cause the hard roof to collapse.

[0024] A second aspect of the present disclosure provides a crack generating device, comprising:

[0025] A drilling arrangement unit is used to arrange drilling holes according to the direction of the minimum principal stress of the hard top plate;

[0026] A first staged fracturing unit is used to perform a first staged fracturing in a borehole according to a preset staged fracturing spacing, and to obtain a parallel fracture group in combination with a mixed fracturing fluid, wherein the mixed fracturing fluid includes a proppant, and the parallel fracture group includes a plurality of parallel fractures parallel to each other, wherein the fracture directions of the parallel fractures are perpendicular to the direction of the minimum principal stress, and there is an induced stress within the preset staged fracturing spacing;

[0027] The second staged fracturing unit is used to perform the second fracturing segmentation in the middle area of ​​every two adjacent parallel fractures in the parallel fracture group, and combine with the fracturing fluid to obtain a diverted fracture between every two adjacent parallel fractures, and the diverted fracture intersects with the extension line of every two adjacent parallel fractures along the fracture direction of the diverted fracture.

[0028] A third aspect of the present disclosure provides an electronic device, including:

[0029] A processor and a memory, the memory is used to store a computer program, and the processor is used to call and run the computer program stored in the memory to execute the steps of the method described in the embodiment of the first aspect of the present disclosure.

[0030] The fourth aspect embodiment of the present disclosure proposes a non-transitory computer-readable storage medium storing computer instructions, characterized in that the computer instructions are used to enable a computer to execute the steps of the method described in the first aspect embodiment of the present disclosure.

[0031] In summary, according to the crack generation method provided by the present invention, a borehole is arranged according to the direction of the minimum principal stress of the hard roof; a first segmented fracturing is performed in the borehole according to a preset segmented fracturing spacing, and a parallel crack group is obtained in combination with a mixed fracturing fluid, wherein the mixed fracturing fluid includes a proppant, and the parallel crack group includes a plurality of parallel cracks parallel to each other, the crack directions of the parallel cracks are perpendicular to the direction of the minimum principal stress, and there is an induced stress within the preset segmented fracturing spacing; a second fracturing segment is performed in the middle area of ​​every two adjacent parallel cracks in the parallel crack group, and a fracturing fluid is combined to obtain a diverted crack between every two adjacent parallel cracks, wherein the diverted crack extends along the crack direction of the diverted crack and intersects with the extension line of every two adjacent parallel cracks, thereby generating a diverted crack with a different direction from the parallel crack based on the induced stress within the preset fracturing spacing, changing the expansion orientation of the crack, further realizing the complexity and connectivity enhancement of the crack network, and effectively improving the fracturing weakening and collapse effect of the hard roof.

[0032] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings herein are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the description are used to explain the principles of the present disclosure, and do not constitute improper limitations on the present disclosure.

[0034] Figure 1 A schematic flow chart of a crack generation method provided for an application example of the present disclosure;

[0035] Figure 2 A schematic flow chart of a crack generation method provided for an application example of the present disclosure;

[0036] Figure 3 A schematic diagram of measuring a geostress field using a hydraulic fracturing geostress measurement method provided for an application example of the present disclosure;

[0037] Figure 4 A schematic diagram of determining induced stress provided for an example of application of the present disclosure;

[0038] Figure 5 A schematic diagram of a fracturing sequence for creating a diverting fracture using the stress shadow effect provided for an application example of the present disclosure;

[0039] Figure 6 A schematic diagram of a crack generating device provided for an application example of the present disclosure;

[0040] Figure 7 A schematic diagram of the composition of an electronic device provided for an application example of the present disclosure. DETAILED DESCRIPTION

[0041] Embodiments of the present disclosure are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present disclosure, and should not be construed as limiting the present disclosure.

[0042] my country's coal seam occurrence conditions are complex, and hard roofs are widely distributed in various mining areas. They are hard, thick, well-integrated, and have strong bearing capacity. With the increase in the depth and intensity of coal mining, hard roof hanging tops frequently cause disasters, such as large deformation of high-stress tunnels, impact ground pressure, and strong mine pressure on the working face. Conventional blasting and roof caving covers a small area, requires a large amount of work, is costly, and is prone to produce toxic and harmful gases such as carbon monoxide.

[0043] In response to the problem of disaster prevention and control caused by hard roof, relevant technologies have developed hydraulic fracturing technology for hard roof of coal mines, which is a safe, green and economical technology for preventing and controlling strong mine pressure disasters. The hydraulic fracturing technology for hard roof of coal mines mainly uses a drill to drill directly from the tunnel to the target rock layer, and conducts segmented hydraulic fracturing in the formed borehole. Pressing cracks in the intact rock layer destroys the integrity of the rock mass, causing the rock layer to collapse in time, achieving stress transfer or reduction, releasing the accumulated energy of the rock layer, and protecting the tunnel and working face support structure and operators. Hydraulic fracturing forms large-scale cracks in the rock layer. Due to the presence of high-pressure water in the cracks, the rocks on both sides of the cracks are compressed, and additional stress is generated, which is called the stress shadow effect. The stress shadow of hydraulic fracturing will cause the size and direction of the surrounding rock stress to change, and the minimum horizontal stress in the area perpendicular to the crack surface will increase. The existence of the stress shadow effect will affect the expansion direction and shape of adjacent cracks.

[0044] However, due to the constraint of geostress, deep rock cracks generally expand perpendicular to the direction of the minimum principal stress. Local auxiliary measures around the borehole, such as mechanical and jet cutting, have a short depth of cutting guide seams, generally less than 1m. It is difficult to effectively control the expansion direction of cracks in deep rock mass. After expanding along the guide seams, the cracks turn to expand in a plane perpendicular to the direction of the minimum principal stress. Most hydraulic fracture groups are parallel, and it is difficult to form a three-dimensional fracture network that is staggered horizontally and vertically.

[0045] In addition, the drilling holes used for fracturing the roof strata of coal mines are upward holes, which are drilled upward in the tunnel to the high roof. After the fracturing is completed, the fracturing fluid is returned in large quantities under the action of gravity, and the high-pressure water cannot play a normal supporting role. In addition, the cracks opened by fracturing also tend to close under the squeezing effect of ground stress. Therefore, the additional stress generated by fracturing cracks in coal mines is difficult to maintain, and the stress shadow effect is not strong.

[0046] In view of the problems of the above-mentioned related technologies, the crack generation method disclosed in the present invention is used to change the stress field around the first compression crack by utilizing induced stress, thereby controlling the expansion direction of the subsequent compression crack, thereby promoting the formation of a criss-crossing three-dimensional crack network in the hard roof, improving the connectivity and complexity of the crack network in the hard roof, and effectively destroying the integrity of the hard roof, causing it to collapse in time and release the accumulated elastic energy.

[0047] A crack generation method, device, electronic device and medium proposed in the present disclosure are described in detail below with reference to the accompanying drawings.

[0048] Figure 1 A schematic diagram of a crack generation method provided by an embodiment of the present disclosure. Figure 1 As shown, the method comprises the following steps:

[0049] Step 101: Arrange the drill holes according to the direction of the minimum principal stress of the rigid top plate.

[0050] In the embodiments of the present disclosure, when drilling holes in a hard roof area, the direction of the minimum principal stress needs to be considered, because the generation and expansion of cracks always tend to proceed along the minimum principal stress plane.

[0051] The present disclosure may utilize geostress testing technology to determine the direction of minimum principal stress, wherein the geostress testing technology may include hydraulic fracturing, acoustic emission, etc., to accurately measure and determine the direction and magnitude of the minimum principal stress.

[0052] In order to ensure the best drilling and fracturing effect, the axis of the borehole should be as parallel to the direction of the minimum principal stress as possible. In this way, the hydraulic fracture will be more likely to expand along the minimum principal stress plane and form an effective fracture network.

[0053] In addition, in addition to the direction, the present disclosure may also consider drilling parameters such as the diameter, depth, and spacing of the boreholes. These drilling parameters may be set according to specific geological conditions and fracturing requirements, and are not limited in the embodiments of the present disclosure.

[0054] Step 102: Performing a first staged fracturing in the borehole according to a preset staged fracturing spacing, combined with a mixed fracturing fluid, to obtain a parallel fracture group, wherein the mixed fracturing fluid includes a proppant, and the parallel fracture group includes a plurality of parallel fractures parallel to each other, the fracture directions of the parallel fractures are perpendicular to the direction of the minimum principal stress, and there is an induced stress within the preset staged fracturing spacing.

[0055] In an embodiment of the present disclosure, after the borehole is arranged, the present disclosure can perform hydraulic fracturing operations in the borehole, perform the first stage fracturing according to the preset stage fracturing spacing, and inject fracturing fluid into the borehole to cause cracks in the rock and expand. The preset stage fracturing spacing is determined in advance using an induced stress algorithm. Within the preset stage fracturing spacing, due to the fracturing of the rock and the expansion of the cracks, induced stresses will be generated, and these induced stresses can affect the formation and expansion direction of subsequent cracks.

[0056] The first stage of fracturing is carried out in the borehole according to the preset staged fracturing spacing. It is achieved by injecting high-pressure mixed fracturing fluid into the borehole. The high pressure in the mixed fracturing fluid will force the rock to crack and expand. The mixed fracturing fluid includes fracturing fluid and proppant. The proppant enters the crack with the fracturing fluid through the sand mixing skid.

[0057] The proppant can be a material with a certain supporting capacity such as sand and expanded clay to maintain the open state of the fracture.

[0058] The present invention can form a group of parallel cracks in the rock by injecting mixed fracturing fluid. Because the rock is most likely to break in the direction of the minimum principal stress, the direction of these cracks is perpendicular to the direction of the minimum principal stress.

[0059] Step 103: Perform a second fracturing segmentation in the middle area of ​​every two adjacent parallel fractures in the parallel fracture group, and combine with the fracturing fluid to obtain a diverted fracture between every two adjacent parallel fractures, and the diverted fracture intersects with the extension line of every two adjacent parallel fractures along the fracture direction of the diverted fracture.

[0060] In the embodiment of the present disclosure, in the parallel fracture group, the middle area between every two adjacent parallel fractures is selected as the target area of ​​the second fracturing segment. The specific location of this middle area can be determined according to the actual fracture network expansion.

[0061] By injecting fracturing fluid into the middle area of ​​each two adjacent parallel cracks, new cracks can be forced to form in the rock, which are called diversion cracks. The crack direction of the diversion crack intersects with the extension line of each two adjacent parallel cracks, thereby increasing the complexity of the crack network. In order to have a low cost and less impact on the environment, the fracturing fluid in the present disclosure can be clean water.

[0062] In the present disclosure, after obtaining the diverted crack, the present disclosure can also connect the diverted crack with its two adjacent parallel cracks, so as to obtain a complex and staggered group of cracks, so as to utilize the staggered group of cracks to cause the hard roof to collapse.

[0063] In summary, the crack generation method provided by the embodiment of the present disclosure is to arrange boreholes according to the direction of the minimum principal stress of the hard roof; perform the first segmented fracturing in the borehole according to the preset segmented fracturing spacing, and combine with a mixed fracturing fluid to obtain a parallel crack group, the mixed fracturing fluid includes a proppant, the parallel crack group includes a plurality of parallel cracks parallel to each other, the crack directions of the parallel cracks are perpendicular to the minimum principal stress direction, and there is induced stress within the preset segmented fracturing spacing; perform the second fracturing segmentation in the middle area of ​​every two adjacent parallel cracks in the parallel crack group, and combine with the fracturing fluid to obtain a steering crack between every two adjacent parallel cracks, the steering crack extends the crack direction of the steering crack and intersects with the extension line of every two adjacent parallel cracks, so as to realize the generation of steering cracks with different directions from the parallel cracks based on the induced stress in the preset fracturing spacing, change the expansion direction of the cracks, further realize the complexity and connectivity enhancement of the crack network, and effectively improve the fracturing weakening and collapse effect of the hard roof.

[0064] Figure 2 A schematic flow chart of a crack generation method provided in an embodiment of the present disclosure. Figure 2 based on Figure 1 In the embodiment shown, step 101, step 102 and step 103 are further defined. Figure 2 In the embodiment shown, step 101 includes step 201 and step 202, step 103 includes step 204, and step 103 includes step 205. Figure 2 As shown, the method includes the following steps.

[0065] Step 201: Determine the minimum principal stress of the rigid top plate and the direction of the minimum principal stress.

[0066] In the embodiments of the present disclosure, the magnitude and direction of the three-dimensional geostress can be determined respectively by measuring the geostress in hydraulic fracturing. The magnitude of each geostress in the three-dimensional geostress is compared, the geostress with the smallest geostress is determined as the minimum principal stress, and the direction of the geostress with the smallest geostress is taken as the direction of the minimum principal stress.

[0067] Specifically, the present invention can drill a test hole in the tunnel toward the hard roof, use a hydraulic fracturing geostress measurement method (a small-aperture hydraulic fracturing geostress measurement device) to measure the geostress of the roof rock layer, and obtain the size and orientation of the three-dimensional geostress.

[0068] The three-dimensional geostress may specifically include vertical stress, maximum horizontal stress and minimum horizontal stress.

[0069] like Figure 3 As shown, the present disclosure provides a schematic diagram of measuring the ground stress field using a hydraulic fracturing ground stress measurement method. Figure 3 The present invention can drill a test hole in the rock mass to be tested, and use a packer to isolate a test section in the hole for pressure testing. Fracturing fluid (such as high-pressure fluid) is injected into the test section through the drill hole. As the pressure increases, cracks will appear on the borehole wall and the surrounding rock mass. The pressure when the cracks are generated is recorded. This pressure is related to the magnitude of the ground stress, and the maximum horizontal stress value of the test section (i.e., reference Figure 3 σ1) and the minimum horizontal stress value (i.e., reference Figure 3 σ2), the vertical stress can be obtained by artificial estimation. After obtaining the three-dimensional geostress, the present disclosure can determine the direction of the three-dimensional geostress according to the direction of the crack in the test section.

[0070] After obtaining the magnitude and direction of the three-dimensional geostress (vertical stress, maximum horizontal stress and minimum horizontal stress), the present disclosure can first compare the magnitude of each geostress in the three-dimensional geostress, select the geostress with the smallest geostress as the minimum principal geostress, and use the magnitude and direction of the geostress as the magnitude and direction of the minimum principal geostress.

[0071] Step 202: Determine a drilling trajectory according to the direction of the minimum principal stress, and arrange the drilling according to the drilling trajectory, and the drilling is parallel to the direction of the minimum principal stress.

[0072] In the embodiments of the present disclosure, the present disclosure can arrange a drilling site in the tunnel, that is, arrange one or more drilling sites at appropriate locations of the underground tunnel (or tunnel). The drilling site is an area for placing a drilling rig and performing drilling operations.

[0073] After that, a directional drill is used to drill a roof directional hole from the tunnel to the target layer. A directional drill is a drilling device that can accurately control the drilling trajectory. It is used to drill a roof directional hole from the tunnel to the target layer (i.e. the rock layer that needs to be detected or mined). The roof refers to the rock layer at the top of the tunnel. Directional drilling refers to drilling according to the drilling trajectory, that is, arranging the holes.

[0074] After the borehole enters the target layer, its trajectory is changed to be parallel to the direction of the minimum principal stress. That is, after the borehole enters the target layer, the present invention can adjust the parameters of the drilling rig as needed to change the drilling trajectory of the borehole and finally make it parallel to the direction of the minimum principal stress in the rock formation, thereby ensuring that the hydraulic fractures formed under the in situ stress field conditions are perpendicular to the borehole axis, thereby enabling the induced stresses generated by adjacent fractures to be superimposed and strengthened.

[0075] Step 203: Performing a first staged fracturing in the borehole according to a preset staged fracturing spacing, combined with a mixed fracturing fluid, to obtain a parallel fracture group, wherein the mixed fracturing fluid includes a proppant, and the parallel fracture group includes a plurality of parallel fractures parallel to each other, wherein the fracture directions of the parallel fractures are perpendicular to the direction of the minimum principal stress, and there is an induced stress within the preset staged fracturing spacing.

[0076] In the embodiments of the present disclosure, a large-flow fracturing pump group can be used to perform segmented sealing fracturing in the borehole (i.e., the first segmented fracturing), and the proppant enters the cracks along with the fracturing fluid (i.e., the mixed fracturing fluid) through the sand mixing skid, filling the fracturing cracks and keeping the cracks open, forming adjacent parallel or nearly parallel parallel fracture groups.

[0077] It should be noted that the parallel cracks in the parallel crack group in the present disclosure may also be approximately parallel to each other, that is, the angle between adjacent parallel cracks is less than or equal to a preset parallel threshold.

[0078] Among them, the present disclosure performs the first staged fracturing in the borehole according to the preset staged fracturing spacing, combines with the mixed fracturing fluid, and obtains a parallel fracture group. Before that, it also includes: determining the preset staged fracturing spacing according to the induced stress algorithm, the superimposed induced stress between adjacent parallel fractures corresponding to the preset staged fracturing spacing is greater than the second principal stress, and the second principal stress is the geostress greater than the minimum principal stress among the three-dimensional geostresses. The second principal stress can specifically be the geostress in the middle after the three-dimensional geostresses are sorted according to their size, that is, the geostress that is less than the maximum geostress and greater than the minimum geostress.

[0079] Specifically, the segmented fracturing spacing of the parallel fracture group can be predetermined based on the induced stress calculation formula (i.e., induced stress algorithm), the principle of which is that the superimposed induced stress formed by the opening of the cracks on both sides exceeds the second principal stress. The generation of induced stress leads to a decrease in the difference between the second principal stress and the third principal stress (the third principal stress is the largest in-situ stress among the three-dimensional in-situ stresses), and even causes the direction of the principal stress to reverse, and the direction of the expansion of the surrounding new cracks will change, and will no longer be parallel to the expansion of the original cracks.

[0080] Among them, refer to Figure 4 The schematic diagram of induced stress determination is shown in Figure 1. The induced stress algorithm can be expressed as follows:

[0081]

[0082] Among them, Δσ x is the change in the minimum horizontal principal stress, perpendicular to the hydraulic fracture. y is the change of the maximum horizontal principal stress, parallel to the hydraulic fracture; p is the water pressure in the fracture; L is the fracture height; r, r1 and r2 are the lengths from the target point to the midpoint and end of the fracture, respectively; θ, θ1 and θ2 are the angles between the corresponding connecting lines and the fracture.

[0083] The present disclosure ensures that the superimposed induced stress formed between two adjacent parallel cracks exceeds the second principal stress through the above formula.

[0084] Step 204: According to the staged backward fracturing sequence, the second fracturing stage is sequentially performed in the middle area of ​​every two adjacent parallel fractures in the parallel fracture group, and combined with the fracturing fluid, a diverting fracture between every two adjacent parallel fractures is obtained.

[0085] In the embodiments of the present disclosure, Figure 5 The schematic diagram of the fracturing sequence for making a diverted fracture using the stress shadow effect is shown, and σ3 is the minimum principal stress. The present disclosure can arrange new fracturing segments (i.e., the second fracturing segment) in the middle area of ​​two adjacent fractures in accordance with the staged retreat fracturing process (staged retreat fracturing sequence), and use clean water as the fracturing fluid. The new fractures formed will be diverted at a large angle under the superimposed induced stress field formed by the parallel fractures on both sides, that is, diverted fractures (diverted communication fractures).

[0086] Reference Figure 5 In (4), since the present disclosure adopts a segmented backward fracturing sequence, the present disclosure can form a redirected crack between each adjacent parallel crack in sequence according to the fracturing sequence. That is, the second fracturing segmentation is performed in the middle area of ​​the first parallel crack and the second parallel crack in the parallel crack group, and combined with the fracturing fluid, a redirected crack between the first parallel crack and the second parallel crack is obtained, and the first parallel crack is adjacent to the second parallel crack; the second fracturing segmentation is performed in the middle area of ​​the second parallel crack and the third parallel crack in the parallel crack group, and combined with the fracturing fluid, a redirected crack between the second parallel crack and the third parallel crack is obtained, and the second parallel crack is adjacent to the third parallel crack. Until the fracturing section of the current borehole is completely completed, the drilling and fracturing of the next borehole are carried out.

[0087] Step 205: Connect the diverting cracks with every two adjacent parallel cracks to obtain a staggered crack group, so as to utilize the staggered crack group to cause the hard roof to collapse.

[0088] In the embodiments of the present disclosure, after a turning crack is obtained between every two adjacent parallel cracks, the turning crack can be connected with the two adjacent parallel cracks to form a crisscrossing crack group.

[0089] In summary, the present invention can use hydraulic fracturing to measure the size and orientation of ground stress, follow the principle of directional drilling trajectory parallel to the minimum principal stress, and add proppant to the fracturing fluid to fill the initial cracks, thereby enhancing the induced stress field of two adjacent parallel cracks and improving the degree of diversion and expansion of new cracks. At the same time, through the quantitative design basis of the fracturing sequence and the segmented fracturing spacing, the induced stress is used to create diverted cracks, and the diverted cracks are connected with the parallel cracks to create a criss-crossed three-dimensional crack network, which increases the connectivity and complexity of the crack network and improves the cracking and weakening effect of the hard roof of the coal mine.

[0090] In order to implement the crack generation method provided by the embodiment of the present disclosure, the embodiment of the present disclosure also provides a crack generation device, such as Figure 6 As shown, the crack generating device 600 comprises:

[0091] A drilling arrangement unit 610 is used to arrange drilling holes according to the direction of the minimum principal stress of the hard top plate;

[0092] The first staged fracturing unit 620 is used to perform the first staged fracturing in the borehole according to the preset staged fracturing spacing, and obtain a parallel fracture group in combination with a mixed fracturing fluid, wherein the mixed fracturing fluid includes a proppant, and the parallel fracture group includes a plurality of parallel fractures parallel to each other, the fracture directions of the parallel fractures are perpendicular to the minimum principal stress direction, and there is an induced stress within the preset staged fracturing spacing;

[0093] The second staged fracturing unit 630 is used to perform the second fracturing segmentation in the middle area of ​​every two adjacent parallel fractures in the parallel fracture group, and combine with the fracturing fluid to obtain a diverted fracture between every two adjacent parallel fractures, and the diverted fracture intersects with the extension line of every two adjacent parallel fractures along the fracture direction of the diverted fracture.

[0094] In some embodiments, the device 600 also includes: a stress determination unit, which is used to determine the minimum principal stress of the hard top plate and the direction of the minimum principal stress before arranging the drill holes according to the direction of the minimum principal stress among the three-dimensional ground stress of the hard top plate; determine the drilling trajectory according to the direction of the minimum principal stress, so as to arrange the drill holes according to the drilling trajectory, and the drill holes are parallel to the direction of the minimum principal stress.

[0095] In some embodiments, the stress determination unit is used to: determine the magnitude and direction of the three-dimensional geostress respectively by hydraulic fracturing geostress measurement; compare the magnitude of each geostress in the three-dimensional geostress, determine the geostress with the smallest geostress as the minimum principal stress, and use the direction of the geostress with the smallest geostress as the direction of the minimum principal stress.

[0096] In some embodiments, the first staged fracturing unit 620 is used to: perform a first staged fracturing in a borehole according to a preset staged fracturing spacing, and obtain a parallel fracture group in combination with a mixed fracturing fluid. Prior to this, the preset staged fracturing spacing is determined according to an induced stress algorithm, and the superimposed induced stress between adjacent parallel fractures corresponding to the preset staged fracturing spacing is greater than the second principal stress, and the second principal stress is the geostress greater than the minimum principal stress among the three-dimensional geostresses.

[0097] In some embodiments, the second staged fracturing unit 630 is used to: perform a second fracturing segment in the middle area of ​​every two adjacent parallel fractures in the parallel fracture group according to the staged backward fracturing sequence, and combine the fracturing fluid to obtain a redirected fracture between every two adjacent parallel fractures.

[0098] In some embodiments, the second segmented fracturing unit 630 is used to: perform a second fracturing segmentation in the middle area of ​​the first parallel fracture and the second parallel fracture in the parallel fracture group, and combine the fracturing fluid to obtain a redirected fracture between the first parallel fracture and the second parallel fracture, and the first parallel fracture is adjacent to the second parallel fracture; perform a second fracturing segmentation in the middle area of ​​the second parallel fracture and the third parallel fracture in the parallel fracture group, and combine the fracturing fluid to obtain a redirected fracture between the second parallel fracture and the third parallel fracture, and the second parallel fracture is adjacent to the third parallel fracture.

[0099] In some embodiments, the second segmented fracturing unit 630 is used to: perform a second fracturing segment in the middle area of ​​every two adjacent parallel fractures in the parallel fracture group, combine the fracturing fluid to obtain a diverted fracture between every two adjacent parallel fractures, and then connect the diverted fracture with every two adjacent parallel fractures to obtain a staggered fracture group, so as to utilize the staggered fracture group to cause the hard roof to collapse.

[0100] Those skilled in the art should understand that Figure 6 The functions of each unit in the crack generating device 600 shown can be understood by referring to the related description of the crack generating method mentioned above. Figure 6 The functions of each unit in the crack generation device 600 shown can be implemented by a program running on a processor, or by a specific logic circuit. It should be noted that: the crack generation device 600 provided in the above embodiment is only illustrated by the division of the above program units when performing crack generation. In actual applications, the above processing can be assigned to different program units as needed, that is, the internal structure of the system is divided into different program units to complete all or part of the processing described above. In addition, the crack generation device 600 provided in the above embodiment and the crack generation method embodiment belong to the same concept. The specific implementation process is detailed in the method embodiment and will not be repeated here.

[0101] Based on the hardware implementation of the program unit in the crack generation device 600 of the present disclosure, and in order to implement the crack generation method provided by the embodiment of the present disclosure, the present disclosure also provides an electronic device 700. Figure 7 As shown, Figure 7 A schematic diagram of the composition of an electronic device provided in an embodiment of the present disclosure, the electronic device 700 includes: a processor 701 and a memory 702, the memory 702 is used to store computer programs, the processor 701 is used to call and run the computer program stored in the memory 702, and execute the steps of the crack generation method provided in the embodiment of the present disclosure.

[0102] In practical application, such as Figure 7 As shown, the various components in the electronic device 700 are coupled together through the bus module 703. It can be understood that the bus module 703 is used to realize the connection and communication between these components. In addition to the data bus, the bus module 703 also includes a power bus, a control bus and a status signal bus. However, for the sake of clarity, Figure 7 Various buses are labeled as bus module 703.

[0103] The embodiment of the present disclosure also provides a non-transitory computer-readable storage medium storing computer instructions. When the computer instructions are executed by a computer, the steps of the crack generation method provided by the embodiment of the present disclosure are implemented.

[0104] In some embodiments, the computer-readable storage medium may be a magnetic random access memory (FRAM), a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a flash memory, a magnetic surface memory, an optical disk, or a compact disc read-only memory (CD-ROM) or other memory; it may also be various devices including one or any combination of the above memories.

[0105] In some embodiments, computer instructions may be in the form of programs, software, software modules, scripts or codes, written in any form of programming language (including compiled or interpreted languages, or declarative or procedural languages), and may be deployed in any form, including being deployed as independent programs or being deployed as modules, components, subroutines or other units suitable for use in a computing environment. As an example, computer instructions may, but not necessarily correspond to files in a file system, may be stored as part of a file storing other programs or data, for example, in one or more scripts stored in a Hypertext Markup Language (HTML) document, in a single file dedicated to the program in question, or in multiple collaborative files (e.g., files storing one or more modules, subroutines or code portions). As an example, computer instructions may be deployed to be executed on one computing device, or on multiple computing devices located at one location, or on multiple computing devices distributed at multiple locations and interconnected by a communication network.

[0106] It should be noted that the terms "first", "second", etc. in the specification and claims of the present disclosure and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present disclosure described herein can be implemented in an order other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0107] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0108] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0109] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, apparatus or device (such as a computer-based system, a system including a processing module, or other system that can fetch instructions from an instruction execution system, apparatus or device and execute instructions), or used in combination with these instruction execution systems, apparatuses or devices.

[0110] It should be understood that the various parts of the embodiments of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0111] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0112] In addition, each functional unit in each embodiment of the present invention may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium. The above-mentioned storage medium may be a read-only memory, a disk or an optical disk, etc.

[0113] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A crack generation method, characterized in that: The method comprises: Arranging the drill holes according to the direction of the minimum principal stress of the hard top plate; Performing a first staged fracturing in the borehole according to a preset staged fracturing spacing, combining with a mixed fracturing fluid to obtain a parallel fracture group, wherein the mixed fracturing fluid includes a proppant, the parallel fracture group includes a plurality of parallel fractures parallel to each other, the fracture directions of the parallel fractures are perpendicular to the direction of the minimum principal stress, and there is an induced stress within the preset staged fracturing spacing; A second fracturing segment is performed in the middle region of every two adjacent parallel fractures in the parallel fracture group, and combined with the fracturing fluid, a diverted fracture between the every two adjacent parallel fractures is obtained, and the diverted fracture intersects with the extension line of the every two adjacent parallel fractures along the fracture direction of the diverted fracture.

2. The method according to claim 1, characterized in that Before arranging the boreholes according to the direction of the minimum principal stress among the three-dimensional geostress of the hard top plate, the method comprises: determining a minimum principal stress of the rigid top plate and a direction of the minimum principal stress; According to the direction of the minimum principal stress, a drilling trajectory is determined to arrange the drill holes according to the drilling trajectory, and the drill holes are parallel to the direction of the minimum principal stress.

3. The method according to claim 2, characterized in that Determining the minimum principal stress of the hard top plate and the direction of the minimum principal stress includes: Through the hydraulic fracturing ground stress measurement method, the magnitude and direction of the three-dimensional ground stress are determined respectively; The magnitude of each geostress in the three-dimensional geostress is compared, the geostress with the smallest geostress is determined as the minimum principal stress, and the direction of the geostress with the smallest geostress is used as the direction of the minimum principal stress.

4. The method according to claim 1, characterized in that: Before performing the first staged fracturing in the borehole according to the preset staged fracturing spacing and combining with the mixed fracturing fluid to obtain a parallel fracture group, the method includes: According to the induced stress algorithm, the preset segmented fracturing spacing is determined, and the superimposed induced stress between adjacent parallel cracks corresponding to the preset segmented fracturing spacing is greater than the second principal stress, and the second principal stress is the ground stress greater than the minimum principal stress among the three-dimensional ground stresses.

5. The method according to claim 1, characterized in that The second fracturing segment is performed in the middle area of ​​each two adjacent parallel fractures in the parallel fracture group, and combined with the fracturing fluid to obtain the diverted fracture between each two adjacent parallel fractures, including: According to the staged backward fracturing sequence, the second fracturing stage is sequentially performed in the middle area of ​​every two adjacent parallel fractures in the parallel fracture group, and combined with the fracturing fluid, a turning fracture between every two adjacent parallel fractures is obtained.

6. The method according to claim 5, characterized in that The method of performing the second fracturing segmentation in the middle region of each two adjacent parallel fractures in the parallel fracture group according to the staged backward fracturing sequence, and combining the fracturing fluid to obtain the diverted fractures between each two adjacent parallel fractures, comprises: Performing a second fracturing segmentation in the middle region of the first parallel fracture and the second parallel fracture in the parallel fracture group, combining with a fracturing fluid, to obtain a diverting fracture between the first parallel fracture and the second parallel fracture, wherein the first parallel fracture is adjacent to the second parallel fracture; A second fracturing segment is performed in the middle region of the second parallel fracture and the third parallel fracture in the parallel fracture group, and combined with the fracturing fluid, a redirected fracture between the second parallel fracture and the third parallel fracture is obtained, and the second parallel fracture is adjacent to the third parallel fracture.

7. The method according to any one of claims 1 to 6, characterized in that The second fracturing segment is performed in the middle area of ​​each two adjacent parallel fractures in the parallel fracture group, and a fracturing fluid is combined to obtain a diverting fracture between each two adjacent parallel fractures. After that, the method comprises: The diverting cracks are connected with every two adjacent parallel cracks to obtain a staggered crack group, so as to utilize the staggered crack group to cause the hard roof to collapse.

8. A crack generating device, characterized in that: The device comprises: A drilling arrangement unit, used for arranging drilling holes according to the direction of the minimum principal stress of the hard top plate; A first staged fracturing unit, used for performing a first staged fracturing in the borehole according to a preset staged fracturing spacing, combining with a mixed fracturing fluid to obtain a parallel fracture group, wherein the mixed fracturing fluid includes a proppant, the parallel fracture group includes a plurality of parallel fractures parallel to each other, the fracture directions of the parallel fractures are perpendicular to the direction of the minimum principal stress, and the preset staged fracturing spacing has an induced stress; The second segmented fracturing unit is used to perform a second fracturing segment in the middle area of ​​every two adjacent parallel fractures in the parallel fracture group, and combine with the fracturing fluid to obtain a diverted fracture between the every two adjacent parallel fractures, and the diverted fracture intersects with the extension line of the every two adjacent parallel fractures along the fracture direction of the diverted fracture.

9. An electronic device, characterized in that: include: A processor and a memory, the memory being used to store a computer program, the processor being used to call and run the computer program stored in the memory to execute the steps of the method according to any one of claims 1 to 7.

10. A non-transitory computer-readable storage medium storing computer instructions, characterized in that: The computer instructions are used to cause the computer to execute the steps of the method according to any one of claims 1 to 7.

Images