Crack generation methods, apparatus, electronic devices and storage media

Abstract

This disclosure provides a method, apparatus, electronic device, and storage medium for crack generation, relating to the field of prevention and control of strong mine pressure disasters in hard roof coal mines. The method includes: arranging boreholes according to the direction of the minimum principal stress of the hard roof; performing first-stage fracturing within the boreholes according to a preset segmented fracturing interval, combined with a mixed fracturing fluid to obtain a group of parallel cracks perpendicular to the direction of the minimum principal stress; the mixed fracturing fluid includes a proppant, and induced stress is present within the preset segmented fracturing interval; performing a second-stage fracturing segment in the middle region of every two adjacent parallel cracks in the parallel crack group, combined with fracturing fluid to obtain a turning crack between every two adjacent parallel cracks; the turning crack intersects the extension line of every two adjacent parallel cracks along its crack direction, thereby generating turning cracks based on the change in crack propagation orientation caused by induced stress, enhancing the complexity and connectivity of the crack network, and improving the fracturing weakening and collapse effect of the hard roof.

Description

Technical Field

[0001] This disclosure relates to the field of prevention and control of strong mine pressure disasters in hard roof coal mines, and in particular to a method, apparatus, electronic device and storage medium for crack generation. Background Technology

[0002] my country's coal seams have complex occurrence conditions. Hard roofs, due to their high hardness, thickness, good integrity, and strong load-bearing capacity, are prone to inducing disasters such as large deformations in high-stress roadways, rock bursts, and strong mine pressure manifestations during coal mining. Conventional blasting roof caving methods suffer from problems such as small coverage area, large engineering workload, high cost, and the potential generation of toxic and harmful gases. Therefore, hydraulic fracturing technology for hard roofs in coal mines has been developed as a safe, green, and economical means of preventing strong mine pressure disasters. This technology involves drilling directly from the roadway roof to the target rock strata using a drilling rig to perform segmented hydraulic fracturing, disrupting the integrity of the rock mass, achieving stress transfer or reduction, and protecting the roadway and working face support structures and workers.

[0003] Hydraulic fracturing technology for hard roofs in coal mines releases accumulated energy by creating fractures in intact rock strata. However, due to the constraint of geostress, deep rock fractures generally extend perpendicular to the direction of the minimum principal stress. Local auxiliary measures around the borehole, such as mechanical and jet fracturing, result in short guide cuts, typically less than 1 meter deep. This makes it difficult to effectively control the direction of fracture propagation in deep rock masses. After extending along the guide cuts, the fractures turn to extend in a plane perpendicular to the direction of the minimum principal stress, resulting in mostly parallel fractures that are difficult to form a three-dimensional network of cross-sectional and longitudinal fractures. Furthermore, the boreholes used for fracturing coal mine roof strata are upward-facing boreholes. After fracturing, a large amount of fracturing fluid is flushed back under gravity, and the high-pressure water cannot provide normal support. The fractures tend to close under geostress, resulting in a weak stress shadow effect and limited weakening of the hard roof. Summary of the Invention

[0004] This disclosure provides a method, apparatus, electronic device, and storage medium for crack generation to solve problems in related technologies. By drilling holes according to the minimum principal stress direction of a hard top plate and performing first-stage fracturing according to a preset segmented fracturing spacing, a group of parallel cracks perpendicular to the minimum principal stress direction is formed. Subsequently, the induced stress shadowing effect in the preset segmented fracturing spacing changes the direction of crack propagation, inducing the formation of turning cracks in the middle region of adjacent parallel cracks. This further increases the complexity and connectivity of the crack network, effectively improving the cracking weakening and collapse effect of the hard top plate.

[0005] A first aspect of this disclosure provides a method for generating cracks, comprising:

[0006] Drill holes are laid out according to the direction of the minimum principal stress of the rigid top plate;

[0007] The first stage of fracturing is carried out in the borehole according to the preset stage fracturing spacing. Combined with the mixed fracturing fluid, a parallel fracture group is obtained. The mixed fracturing fluid includes proppant. The parallel fracture group includes multiple parallel fractures that are parallel to each other. The fracture direction of the parallel fractures is perpendicular to the direction of the minimum principal stress. There is induced stress within the preset stage fracturing spacing.

[0008] In the parallel fracture group, a second fracturing segment is performed in the middle region of every two adjacent parallel fractures. Combined with fracturing fluid, a turning fracture is obtained between every two adjacent parallel fractures. The turning fracture intersects the extension line of every two adjacent parallel fractures along the fracture direction of the turning fracture.

[0009] In some embodiments, boreholes are drilled according to the direction of the minimum principal stress in the triaxial geostress of the rigid top plate, prior to which the method includes:

[0010] Determine the minimum principal stress and direction of the minimum principal stress in a rigid top plate;

[0011] The drilling trajectory is determined based on the direction of the minimum principal stress, and the boreholes are laid out according to the drilling trajectory, with the boreholes parallel to the direction of the minimum principal stress.

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

[0013] The magnitude and direction of the triaxial stress were determined by measuring the stress in the ground using water pressure fracturing.

[0014] By comparing the magnitude of each geostress in the three-dimensional geostress, 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.

[0015] In some embodiments, a first stage of fracturing is performed within the borehole according to a preset staged fracturing interval, combined with a mixed fracturing fluid, to obtain a parallel fracture group. Prior to this, the method includes:

[0016] Based on the induced stress algorithm, the preset segmented fracturing spacing is determined. The superimposed induced stress between adjacent parallel fractures corresponding to the preset segmented fracturing spacing is greater than the second principal stress. The second principal stress is the geostress among the three-dimensional geostresses that is greater than the minimum principal stress.

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

[0018] Based on the segmented retreat fracturing sequence, a second fracturing segment is performed in the middle region of every two adjacent parallel fractures in the parallel fracture group. Combined with fracturing fluid, a turning fracture is obtained between every two adjacent parallel fractures.

[0019] In some embodiments, according to the segmented retreat fracturing sequence, a second fracturing segment is sequentially performed in the middle region of every two adjacent parallel fractures in the parallel fracture group. Combined with fracturing fluid, a turning fracture is obtained between every two adjacent parallel fractures, including:

[0020] In the middle region of the first and second parallel fractures in the parallel fracture group, a second fracturing segment is performed. Combined with fracturing fluid, a turning fracture is obtained between the first and second parallel fractures, with the first parallel fracture adjacent to the second parallel fracture.

[0021] A second fracturing segment is performed in the middle region of the second and third parallel fractures in the parallel fracture group. Combined with fracturing fluid, a turning fracture is obtained between the second and third parallel fractures, with the second and third parallel fractures adjacent to each other.

[0022] In some embodiments, a second fracturing segment is performed in the middle region of every two adjacent parallel fractures in a group of parallel fractures, and fracturing fluid is used to obtain a turning fracture between every two adjacent parallel fractures. The method then includes:

[0023] Connecting the turning cracks with every two adjacent parallel cracks creates staggered crack groups, which can be used to cause the rigid roof to collapse.

[0024] A second aspect of this disclosure provides a crack generation apparatus, comprising:

[0025] The drilling layout unit is used to lay out the drill holes according to the direction of the minimum principal stress of the hard top plate;

[0026] The first segmented fracturing unit is used to perform first segmented fracturing in the borehole according to the preset segmented fracturing spacing. Combined with mixed fracturing fluid, it obtains a parallel fracture group. The mixed fracturing fluid includes proppant. The parallel fracture group includes multiple parallel fractures that are parallel to each other. The fracture direction of the parallel fractures is perpendicular to the direction of the minimum principal stress. There is induced stress within the preset segmented fracturing spacing.

[0027] The second segmented fracturing unit is used to perform a second fracturing segmentation in the middle region of every two adjacent parallel fractures in the parallel fracture group. Combined with fracturing fluid, a turning fracture is obtained between every two adjacent parallel fractures. The turning fracture intersects the extension line of every two adjacent parallel fractures along the fracture direction of the turning fracture.

[0028] A third aspect of this disclosure provides an electronic device comprising:

[0029] A processor and a memory, the memory being used to store a computer program, the processor being used to invoke and run the computer program stored in the memory to perform the steps of the method as described in the first aspect of the present disclosure.

[0030] A fourth aspect of this disclosure provides a non-transitory computer-readable storage medium storing computer instructions, characterized in that the computer instructions are used to cause a computer to perform the steps of the method described in the first aspect of this disclosure.

[0031] In summary, according to the fracture generation method provided in this disclosure, boreholes are laid out according to the direction of the minimum principal stress of the hard top plate; a first-stage fracturing is performed in the boreholes according to a preset segmented fracturing interval, combined with a mixed fracturing fluid, to obtain a parallel fracture group. The mixed fracturing fluid includes proppant, and the parallel fracture group includes multiple parallel fractures. The fracture direction of the parallel fractures is perpendicular to the direction of the minimum principal stress, and induced stress exists within the preset segmented fracturing interval; a second fracturing segment is performed in the middle region of every two adjacent parallel fractures in the parallel fracture group, combined with fracturing fluid, to obtain a turning fracture between every two adjacent parallel fractures. The turning fracture intersects the extension line of every two adjacent parallel fractures along the fracture direction of the turning fracture, thereby realizing the generation of turning fractures with different directions from the parallel fractures based on induced stress within the preset fracturing interval. This changes the direction of fracture propagation, further complicates the fracture network and enhances its connectivity, effectively improving the fracturing weakening and collapse effect of the hard top plate.

[0032] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0033] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure, and are not intended to unduly limit this disclosure.

[0034] Figure 1 A flowchart illustrating a crack generation method provided as an application example of this disclosure;

[0035] Figure 2 A flowchart illustrating a crack generation method provided as an application example of this disclosure;

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

[0037] Figure 4 A schematic diagram illustrating the determination of induced stress as an application example of this disclosure;

[0038] Figure 5 A schematic diagram illustrating a fracturing sequence for creating directional cracks using the stress shadowing effect, as an application example of this disclosure;

[0039] Figure 6 A schematic diagram of a crack generation device provided as an application example of this disclosure;

[0040] Figure 7 A schematic diagram of the composition of an electronic device provided as an application example of this disclosure. Detailed Implementation

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

[0042] my country's coal seams have complex occurrence conditions, with hard roofs widely distributed across various mining areas. These hard roofs are characterized by high hardness, large thickness, good integrity, and strong load-bearing capacity. With increasing coal mining depth and intensity, the overhang of hard roofs frequently triggers disasters such as large deformations in high-stress roadways, rock bursts, and strong mine pressure manifestations at the working face. Conventional blasting roof caving methods have limited coverage areas, large engineering workloads, and high costs, and also easily generate toxic and harmful gases such as carbon monoxide.

[0043] To address the challenge of preventing and controlling disasters induced by hard roofs in coal mines, hydraulic fracturing technology for hard roofs has been developed. This technology is a safe, green, and economical method for preventing and controlling strong mine pressure disasters. Hydraulic fracturing technology for hard roofs in underground coal mines primarily involves drilling directly from the roadway to the target rock strata, and then performing segmented hydraulic fracturing within the formed borehole. This process creates cracks in intact rock strata, disrupting the rock mass's integrity and prompting timely collapse of the strata. This achieves stress transfer or reduction, releases accumulated energy in the rock strata, and protects the roadway, working face support structures, and workers. Hydraulic fracturing creates large-scale cracks in the rock strata. The presence of high-pressure water within the cracks causes compression of the rock on both sides of the cracks, generating additional stress, known as the stress shadow effect. The stress shadow effect of hydraulic fracturing alters the magnitude and direction of the surrounding rock stress, with the minimum horizontal stress increasing in the area perpendicular to the crack surface. The presence of the stress shadow effect also influences the propagation direction and morphology of adjacent cracks.

[0044] However, due to the constraint of geostress, deep rock fractures generally extend perpendicular to the direction of the minimum principal stress. Local auxiliary measures around the borehole, such as mechanical and jet cutting, result in short guide cuts, typically less than 1 meter deep. This makes it difficult to effectively control the direction of fracture propagation in deep rock masses. After extending along the guide cuts, the fractures turn and propagate in a plane perpendicular to the direction of the minimum principal stress. Hydraulic fracture clusters are mostly parallel and rarely form a three-dimensional network of intersecting fractures.

[0045] Furthermore, the drilling used for fracturing the roof strata in coal mines is upward-drilling, extending upwards through the roadway to a high position in the roof. After fracturing, a large amount of fracturing fluid is flushed back under gravity, and the high-pressure water cannot provide normal support. Additionally, the fractures opened by fracturing tend to close under the pressure of ground stress. Therefore, the additional stress generated by fracturing fractures in underground coal mines is difficult to maintain, and the stress shadowing effect is weak.

[0046] To address the problems of the aforementioned related technologies, the crack generation method disclosed herein utilizes induced stress to alter the stress field around the pre-pressed crack, thereby controlling the propagation direction of the post-pressed crack. This promotes the formation of a crisscrossing three-dimensional crack network in the rigid roof, enhancing the connectivity and complexity of the crack network in the rigid roof, effectively disrupting the integrity of the rigid roof, and prompting it to collapse in a timely manner, releasing the accumulated elastic energy.

[0047] The following describes in detail, with reference to the accompanying drawings, a method, apparatus, electronic device, and medium for generating cracks as proposed in this disclosure.

[0048] Figure 1 This is a schematic flowchart illustrating a crack generation method provided in an embodiment of this disclosure. Figure 1 As shown, the method includes the following steps:

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

[0050] In embodiments of this disclosure, when drilling in a hard top plate region, the direction of the minimum principal stress needs to be considered, because crack generation and propagation always tend to occur along the plane of the minimum principal stress.

[0051] This disclosure allows for the use of geostress testing techniques to determine the direction of the minimum principal stress. These techniques may include hydraulic fracturing, acoustic emission, and other methods to accurately measure and determine the direction and magnitude of the minimum principal stress.

[0052] To ensure optimal borehole fracturing results, the borehole axis should be as parallel as possible to the direction of the minimum principal stress. This will make it easier for hydraulic fractures to propagate along the plane of minimum principal stress, forming an effective fracture network.

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

[0054] Step 102: Perform the first stage of fracturing in the borehole according to the preset stage fracturing spacing, and combine with the mixed fracturing fluid to obtain a parallel fracture group. The mixed fracturing fluid includes proppant. The parallel fracture group includes multiple parallel fractures that are parallel to each other. The fracture direction of the parallel fractures is perpendicular to the direction of the minimum principal stress. There is induced stress within the preset stage fracturing spacing.

[0055] In the embodiments of this disclosure, after the borehole layout is completed, hydraulic fracturing operations can be performed within the borehole. The first stage of fracturing is performed according to a preset fracturing interval. Fracturing fluid is injected into the borehole to induce and propagate fractures in the rock. The preset fracturing interval is determined in advance using an induced stress algorithm. Within the preset fracturing interval, induced stress is generated due to rock fracturing and fracture propagation. This induced stress can influence the formation and propagation direction of subsequent fractures.

[0056] The first stage of fracturing is carried out inside the borehole according to the preset segmented fracturing intervals. This is specifically achieved by injecting high-pressure mixed fracturing fluid into the borehole. The high pressure in the mixed fracturing fluid forces the rock to form and propagate fractures. The mixed fracturing fluid includes fracturing fluid and proppant. The proppant is introduced into the fracture along with the fracturing fluid via a proppant skid.

[0057] The proppant can be a material with a certain supporting capacity, such as sand or ceramsite, to maintain the open state of the crack.

[0058] This disclosure describes a method for creating a series of parallel fractures in rock by injecting a mixed fracturing fluid. Since rock is most prone to fracture in the direction of the minimum principal stress, these fractures are oriented perpendicular to that direction.

[0059] Step 103: Perform a second fracturing segmentation in the middle region of every two adjacent parallel fractures in the parallel fracture group. Combined with fracturing fluid, a turning fracture is obtained between every two adjacent parallel fractures. The turning fracture intersects the extension line of every two adjacent parallel fractures along the fracture direction of the turning fracture.

[0060] In embodiments of this disclosure, within a group of parallel fractures, the central region between every two adjacent parallel fractures is selected as the target region for the second fracturing segment. The specific location of this central region can be determined based on the actual fracture network expansion.

[0061] By injecting fracturing fluid into the mid-region of every two adjacent parallel fractures, new fractures, known as diverting fractures, can be forced into the rock. The direction of these diverting fractures intersects the extensions of every two adjacent parallel fractures, thus increasing the complexity of the fracture network. To achieve a lower cost and less environmental impact, clean water can be used as the fracturing fluid in this disclosure.

[0062] In this disclosure, after obtaining the turning crack, the turning crack can also be connected with two adjacent parallel cracks to obtain a complex set of interlaced cracks, which can be used to cause the rigid roof to collapse.

[0063] In summary, the crack generation method provided in this disclosure involves: arranging boreholes according to the direction of the minimum principal stress in a hard top plate; performing first-stage fracturing within the boreholes according to a preset fracturing interval; combining this with a mixed fracturing fluid to obtain a parallel crack group, the mixed fracturing fluid including proppant; the parallel crack group comprising multiple parallel cracks, the crack direction of which is perpendicular to the direction of the minimum principal stress; and induced stress within the preset fracturing interval. A second fracturing segment is then performed in the middle region of every two adjacent parallel cracks within the parallel crack group, combining this with fracturing fluid to obtain a turning crack between every two adjacent parallel cracks. This turning crack intersects the extension line of every two adjacent parallel cracks along its crack direction, thereby generating turning cracks with directions different from the parallel cracks within the preset fracturing interval based on induced stress. This changes the crack propagation orientation, further increasing the complexity and connectivity of the crack network, and effectively improving the fracturing weakening and collapse effect of the hard top plate.

[0064] Figure 2 This is a schematic flowchart of a crack generation method provided in an embodiment of the present disclosure. Figure 2 based on Figure 1 The illustrated embodiment further defines steps 101, 102, and 103. Figure 2 In the illustrated embodiment, step 101 includes steps 201 and 202, step 103 includes step 204, and step 205 is included after step 103. Figure 2 As shown, the method includes the following steps.

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

[0066] In the embodiments of this disclosure, the magnitude and direction of the three-dimensional geostress can be determined by water pressure fracturing geostress measurement; 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, this disclosure allows for the drilling of test boreholes into the hard roof of the tunnel, and the use of a water-pressure fracturing stress measurement method (small-diameter water-pressure fracturing stress measurement device) to measure the stress in the roof strata and obtain the magnitude and orientation of the three-dimensional stress.

[0068] Specifically, triaxial geostress can include vertical stress, maximum horizontal stress, and minimum horizontal stress.

[0069] like Figure 3 As shown, this disclosure provides a schematic diagram of a specific method for measuring the geostress field using hydraulic fracturing geostress measurement. (Refer to...) Figure 3 This disclosure allows for drilling a test borehole in the rock mass to be tested, and sealing a test section within the borehole using a packer for pressure testing. Fracturing fluid (e.g., high-pressure fluid) is injected into the test section through the borehole. As the pressure increases, cracks will appear in the borehole wall and the surrounding rock mass. The pressure at which the cracks occur is recorded; this pressure is related to the magnitude of the in-situ stress, and the maximum horizontal stress value of the test section (i.e., reference stress) is determined. Figure 3 σ1) and minimum horizontal stress value (i.e., reference) Figure 3 The vertical stress (σ2) can be estimated manually. After obtaining the triaxial stress, this disclosure can determine the direction of the triaxial stress based on the direction of the crack in the test section.

[0070] After obtaining the magnitude and direction of the triaxial geostress (vertical stress, maximum horizontal stress, and minimum horizontal stress), this disclosure can first compare the magnitude of each geostress in the triaxial geostress, select the geostress with the smallest geostress as the minimum principal geostress, and take the magnitude and direction of this geostress as the magnitude and direction of the minimum principal geostress.

[0071] Step 202: Determine the drilling trajectory based on the direction of the minimum principal stress, and lay out the boreholes according to the drilling trajectory, with the boreholes parallel to the direction of the minimum principal stress.

[0072] In embodiments of this disclosure, drilling sites can be deployed within tunnels, that is, one or more drilling sites can be deployed at suitable locations in underground tunnels (or tunnels). A drilling site is an area used to house drilling rigs and conduct drilling operations.

[0073] Then, a directional drilling rig is used to drill directional boreholes into the target layer from inside the tunnel. A directional drilling rig is a drilling device that can precisely control the drilling trajectory. It is used to drill directional boreholes into the target layer (i.e., the rock layer that needs to be explored or mined) from inside the tunnel. The roof refers to the rock layer at the top of the tunnel. Directional drilling means drilling according to the drilling trajectory, that is, laying out the boreholes.

[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 parameters of the drilling rig can be adjusted as needed to change the borehole trajectory and eventually make it parallel to the direction of the minimum principal stress in the rock layer. This ensures that the hydraulic fractures formed under the in-situ stress field conditions are all perpendicular to the borehole axis, thereby allowing the induced stress generated by adjacent fractures to be superimposed and strengthened.

[0075] Step 203: Perform the first stage of fracturing in the borehole according to the preset stage fracturing spacing, and combine with the mixed fracturing fluid to obtain a parallel fracture group. The mixed fracturing fluid includes proppant. The parallel fracture group includes multiple parallel fractures that are parallel to each other. The fracture direction of the parallel fractures is perpendicular to the direction of the minimum principal stress. There is induced stress within the preset stage fracturing spacing.

[0076] In the embodiments of this disclosure, a high-flow-rate fracturing pump set can be used to perform segmented fracturing in the borehole (i.e., first-segment fracturing). The proppant enters the fracture interior through the sand-mixing skid along with the fracturing fluid (i.e., mixed fracturing fluid), filling the fracturing fracture and keeping the fracture open, forming a group of adjacent parallel or nearly parallel fractures.

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

[0078] This disclosure involves performing first-stage fracturing within the borehole according to a preset segmented fracturing spacing, combined with mixed fracturing fluid, to obtain a group of parallel fractures. Prior to this, the process includes: determining the preset segmented fracturing spacing based on an induced stress algorithm; the superimposed induced stress between adjacent parallel fractures corresponding to the preset segmented fracturing spacing is greater than the second principal stress, which is the geostress among the three-dimensional geostresses that is greater than the minimum principal stress. Specifically, the second principal stress can be the geostress that ranks in the middle after being sorted by magnitude among the three-dimensional geostresses, i.e., the geostress that is less than the maximum geostress and greater than the minimum geostress.

[0079] Specifically, the spacing between segments of parallel fracture groups can be predetermined based on the induced stress calculation formula (i.e., the induced stress algorithm). The principle is that the superimposed induced stress formed by the opening of fractures on both sides exceeds the second principal stress. The generation of induced stress reduces the difference between the second principal stress and the third principal stress (the third principal stress is the largest of the three-dimensional geostresses), and may even cause the principal stress direction to reverse. The direction of the propagation of new fractures in the surrounding area will change, and they will no longer propagate parallel to the original fracture propagation.

[0080] Among them, reference Figure 4 The diagram shown illustrates the determination of induced stress. The algorithm for induced stress can be represented by the following formula:

[0081]

[0082] Where, Δσ x Δσ represents the change in minimum horizontal principal stress, perpendicular to the hydraulic fracture. y denoted as the change in maximum horizontal principal stress, parallel to the hydraulic fracture; p is the water pressure inside 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 lines and the fracture.

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

[0084] Step 204: According to the segmented retreat fracturing sequence, the second fracturing segment is carried out in the middle region of every two adjacent parallel fractures in the parallel fracture group. Combined with fracturing fluid, the turning fracture between every two adjacent parallel fractures is obtained.

[0085] In embodiments of this disclosure, such as Figure 5 The diagram shows a fracturing sequence for creating directional fractures using the stress shadow effect, where σ3 is the minimum principal stress. This disclosure allows for the sequential arrangement of new fracturing segments (i.e., the second fracturing segment) in the middle region of two adjacent fractures, based on a segmented retreat fracturing process (segmented retreat fracturing sequence). Using water as the fracturing fluid, the newly formed fracture undergoes a large-angle deflection under the superimposed induced stress field created by the parallel fractures on both sides, thus forming a directional fracture (directional connecting fracture).

[0086] Reference Figure 5 In section (4), since this disclosure adopts a segmented retreat fracturing sequence, it can sequentially form directional fractures between each adjacent parallel fracture according to the fracturing sequence. That is, a second fracturing segment is performed in the middle region of the first and second parallel fractures in the parallel fracture group, and with the fracturing fluid, a directional fracture is obtained between the first and second parallel fractures, with the first parallel fracture adjacent to the second parallel fracture; a second fracturing segment is performed in the middle region of the second and third parallel fractures in the parallel fracture group, and with the fracturing fluid, a directional fracture is obtained between the second and third parallel fractures, with the second parallel fracture adjacent to the third parallel fracture. Until the entire fracturing segment of this borehole is completed, drilling and fracturing of the next borehole are carried out.

[0087] Step 205: Connect the turning cracks with every two adjacent parallel cracks to obtain staggered crack groups, which are used to cause the rigid roof to collapse.

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

[0089] In summary, this disclosure utilizes hydraulic fracturing to measure the magnitude and orientation of in-situ stress, adheres to the principle of directional drilling trajectories parallel to the minimum principal stress, and adds proppant to the fracturing fluid to fill the initial fractures, thereby enhancing the induced stress field between two adjacent parallel fractures and increasing the degree of new fracture directional propagation. Simultaneously, through a quantitative design basis for fracturing sequence and segmented fracturing spacing, directional fractures are created using induced stress, and these directional fractures are connected to parallel fractures to create a crisscrossing three-dimensional fracture network. This increases the connectivity and complexity of the fracture network, improving the fracturing and weakening effect on the hard roof of coal mines.

[0090] To implement the crack generation method provided in this disclosure, this disclosure also provides a crack generation apparatus, such as... Figure 6 As shown, the crack generation device 600 includes:

[0091] The drilling layout unit 610 is used to lay out the drill holes according to the direction of the minimum principal stress of the hard top plate.

[0092] The first segmented fracturing unit 620 is used to perform first segmented fracturing in the borehole according to the preset segmented fracturing spacing, and combined with the mixed fracturing fluid to obtain a parallel fracture group. The mixed fracturing fluid includes proppant, and the parallel fracture group includes multiple parallel fractures that are parallel to each other. The fracture direction of the parallel fractures is perpendicular to the direction of the minimum principal stress, and there is induced stress within the preset segmented fracturing spacing.

[0093] The second segmented fracturing unit 630 is used to perform a second fracturing segmentation in the middle region of every two adjacent parallel fractures in the parallel fracture group. Combined with fracturing fluid, a turning fracture is obtained between every two adjacent parallel fractures. The turning fracture intersects the extension line of every two adjacent parallel fractures along the fracture direction of the turning fracture.

[0094] In some embodiments, the apparatus 600 further includes: a stress determination unit, configured to determine the minimum principal stress of the rigid top plate and the direction of the minimum principal stress before drilling holes according to the direction of the minimum principal stress in the triaxial geostress of the rigid top plate; and to determine the drilling trajectory according to the direction of the minimum principal stress so as to lay the drilling holes according to the drilling trajectory, wherein the drilling 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 by means of 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 take the direction of the geostress with the smallest geostress as the direction of the minimum principal stress.

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

[0097] In some embodiments, the second segmented fracturing unit 630 is used to: perform a second fracturing segmentation in the middle region of every two adjacent parallel fractures in the parallel fracture group according to the segmented retreating fracturing sequence, and combine fracturing fluid to obtain a turning fracture between every two adjacent parallel fractures.

[0098] In some embodiments, the second segmented fracturing unit 630 is configured to: perform a second fracturing segmentation in the middle region of the first parallel fracture and the second parallel fracture in the parallel fracture group, and combine with fracturing fluid to obtain a turning fracture between the first parallel fracture and the second parallel fracture, wherein the first parallel fracture is adjacent to the second parallel fracture; and perform a second fracturing segmentation in the middle region of the second parallel fracture and the third parallel fracture in the parallel fracture group, and combine with fracturing fluid to obtain a turning fracture between the second parallel fracture and the third parallel fracture, wherein 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 segmentation in the middle region of every two adjacent parallel fractures in the parallel fracture group, combine fracturing fluid to obtain a turning fracture between every two adjacent parallel fractures, and then connect the turning fracture with every two adjacent parallel fractures to obtain an interlaced fracture group, so as to use the interlaced 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 generation device 600 shown can be understood by referring to the relevant description of the crack generation method described above. Figure 6 The functions of each unit in the crack generation device 600 shown can be implemented through a program running on a processor or through specific logic circuits. It should be noted that the crack generation device 600 provided in the above embodiment is only illustrated by the division of the program units described above. In practical applications, the above processing can be assigned to different program units as needed, that is, the internal structure of the system can be divided into different program units to complete all or part of the processing described above. Furthermore, the crack generation device 600 and the crack generation method embodiment provided in the above 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 units in the crack generation apparatus 600 of this disclosure, and in order to implement the crack generation method provided in the embodiments of this disclosure, this disclosure also provides an electronic device 700. For example... Figure 7 As shown, Figure 7 The electronic device 700 provided in the embodiments of this disclosure includes a processor 701 and a memory 702. The memory 702 is used to store computer programs, and the processor 701 is used to call and run the computer programs stored in the memory 702 to perform the steps of the crack generation method provided in the embodiments of this disclosure.

[0102] In practical applications, such as Figure 7 As shown, the various components in electronic device 700 are coupled together via bus module 703. It can be understood that bus module 703 is used to implement communication between these components. In addition to a data bus, bus module 703 also includes a power bus, a control bus, and a status signal bus. However, for clarity, in... Figure 7 The general labels all buses as bus module 703.

[0103] This disclosure also provides a non-transitory computer-readable storage medium storing computer instructions, which, when executed by a computer, implement the steps of the crack generation method provided in this disclosure.

[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 disc, or a compact disc read-only memory (CD-ROM), etc.; or it may be a device that includes one or any combination of the above-mentioned memories.

[0105] In some embodiments, computer instructions may take the form of programs, software, software modules, scripts, or code, written in any type of programming language (including compiled or interpreted languages, or declarative or procedural languages), and may be deployed in any form, including as standalone programs or 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, and may be stored as part of a file containing other programs or data, for example, in one or more scripts within a Hyper Text Markup Language (HTML) document, in a single file dedicated to the program in question, or in multiple co-located files (e.g., files storing one or more modules, subroutines, or code portions). As an example, computer instructions may be deployed to execute on a single computing device, or on multiple computing devices located in one location, or on multiple computing devices distributed across multiple locations and interconnected via a communication network.

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

[0107] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0108] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0109] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, 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 and execute instructions from, an instruction execution system, apparatus or device).

[0110] It should be understood that various parts of the embodiments of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0111] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

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

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

Claims

1. A method for generating cracks, characterized in that, The method includes: Drill holes are laid out according to the direction of the minimum principal stress of the rigid top plate; The first stage of fracturing is performed in the borehole according to the preset stage fracturing interval. Combined with the mixed fracturing fluid, a parallel fracture group is obtained. The mixed fracturing fluid includes proppant. The parallel fracture group includes multiple parallel fractures that are parallel to each other. The fracture direction of the parallel fractures is perpendicular to the direction of the minimum principal stress. Induced stress is present within the preset stage fracturing interval. In the parallel fracture group, a second fracturing segment is performed in the middle region of every two adjacent parallel fractures. Combined with fracturing fluid, a turning fracture is obtained between every two adjacent parallel fractures. The turning fracture intersects the extension line of every two adjacent parallel fractures along the fracture direction of the turning fracture. Among these, boreholes are laid out according to the direction of the minimum principal stress in the triaxial geostress of the hard top plate, and the preceding steps include: Determine the minimum principal stress of the rigid top plate and the direction of the minimum principal stress; The drilling trajectory is determined according to the direction of the minimum principal stress, and the boreholes are laid out according to the drilling trajectory, wherein the boreholes are parallel to the direction of the minimum principal stress; Specifically, the first stage of fracturing is performed within the borehole according to a preset fracturing interval, combined with mixed fracturing fluid, to obtain a parallel fracture group, which includes the following: According to the induced stress algorithm, the preset segmented fracturing spacing is determined. The superimposed induced stress between adjacent parallel fractures corresponding to the preset segmented fracturing spacing is greater than the second principal stress. The second principal stress is the geostress among the three-dimensional geostresses that is less than the maximum principal stress and greater than the minimum principal stress. The induced stress algorithm is expressed by the following formula: in, The change in minimum principal stress is perpendicular to the hydraulic fracture. The change in maximum principal stress is parallel to the hydraulic fracture; p is the water pressure inside the fracture; L is the fracture height; r, and These are the lengths from the target point to the midpoint and end of the crack, respectively. , and The angle between the corresponding line and the crack; Specifically, the second fracturing segmentation is performed in the middle region of every two adjacent parallel fractures in the parallel fracture group, and a turning fracture is obtained between every two adjacent parallel fractures by combining fracturing fluid, followed by: The diverting cracks are connected to each pair of adjacent parallel cracks to form an interlaced crack group, which is used to cause the rigid roof to collapse.

2. The method according to claim 1, characterized in that, Determining the minimum principal stress of the rigid top plate and the direction of the minimum principal stress includes: The magnitude and direction of the triaxial stress were determined by measuring the stress in the ground using water pressure fracturing. By comparing the magnitude of each of the three geostresses, the geostress with the smallest magnitude is determined as the minimum principal stress, and the direction of the geostress with the smallest magnitude is taken as the direction of the minimum principal stress.

3. The method according to claim 1, characterized in that, The second fracturing segmentation is performed in the middle region of every two adjacent parallel fractures in the parallel fracture group. Combined with fracturing fluid, a turning fracture is obtained between every two adjacent parallel fractures, including: According to the segmented retreat fracturing sequence, the second fracturing segment is performed in the middle region of every two adjacent parallel fractures in the parallel fracture group. Combined with fracturing fluid, a turning fracture is obtained between every two adjacent parallel fractures.

4. The method according to claim 3, characterized in that According to the segmented retreat fracturing sequence, a second fracturing segment is sequentially performed in the middle region of every two adjacent parallel fractures in the parallel fracture group. Combined with fracturing fluid, a turning fracture is obtained between every two adjacent parallel fractures, including: A second fracturing segment is performed in the middle region of the first and second parallel fractures in the parallel fracture group. Combined with fracturing fluid, a turning fracture is obtained between the first and second parallel fractures, with the first parallel fracture being adjacent to the second parallel fracture. A second fracturing segment is performed in the middle region of the second and third parallel fractures in the parallel fracture group. Combined with fracturing fluid, a turning fracture is obtained between the second and third parallel fractures, with the second parallel fracture adjacent to the third parallel fracture.

5. A crack generation device, characterized in that, The device includes: The drilling layout unit is used to lay out the drill holes according to the direction of the minimum principal stress of the hard top plate; The first segmented fracturing unit is used to perform first segmented fracturing in the borehole according to a preset segmented fracturing interval, and to combine with a mixed fracturing fluid to obtain a parallel fracture group. The mixed fracturing fluid includes a proppant, and the parallel fracture group includes multiple parallel fractures that are parallel to each other. The fracture direction of the parallel fractures is perpendicular to the direction of the minimum principal stress, and there is induced stress within the preset segmented fracturing interval. The second segmented fracturing unit is used to perform a second fracturing segmentation in the middle region of every two adjacent parallel fractures in the parallel fracture group, and in combination with fracturing fluid, to obtain a turning fracture between every two adjacent parallel fractures. The turning fracture intersects the extension line of every two adjacent parallel fractures along the fracture direction of the turning fracture. Among these, boreholes are laid out according to the direction of the minimum principal stress in the triaxial geostress of the hard top plate, and the preceding steps include: Determine the minimum principal stress of the rigid top plate and the direction of the minimum principal stress; The drilling trajectory is determined according to the direction of the minimum principal stress, and the boreholes are laid out according to the drilling trajectory, wherein the boreholes are parallel to the direction of the minimum principal stress; Specifically, the first stage of fracturing is performed within the borehole according to a preset fracturing interval, combined with mixed fracturing fluid, to obtain a parallel fracture group, which includes the following: According to the induced stress algorithm, the preset segmented fracturing spacing is determined. The superimposed induced stress between adjacent parallel fractures corresponding to the preset segmented fracturing spacing is greater than the second principal stress. The second principal stress is the geostress among the three-dimensional geostresses that is less than the maximum principal stress and greater than the minimum principal stress. The induced stress algorithm is expressed by the following formula: in, The change in minimum principal stress is perpendicular to the hydraulic fracture. The change in maximum principal stress is parallel to the hydraulic fracture; p is the water pressure inside the fracture; L is the fracture height; r, and These are the lengths from the target point to the midpoint and end of the crack, respectively. , and The angle between the corresponding line and the crack; Specifically, the second fracturing segmentation is performed in the middle region of every two adjacent parallel fractures in the parallel fracture group, and a turning fracture is obtained between every two adjacent parallel fractures by combining fracturing fluid, followed by: The diverting cracks are connected to each pair of adjacent parallel cracks to form an interlaced crack group, which is used to cause the rigid roof to collapse.

6. An electronic device, characterized in that, include: A processor and a memory for storing a computer program, the processor for calling and running the computer program stored in the memory to perform the steps of the method as described in any one of claims 1 to 4.

7. A non-transitory computer-readable storage medium storing computer instructions, characterized in that, The computer instructions are used to cause the computer to perform the steps of the method as described in any one of claims 1 to 4.

Images