CN118656987B - Directional long drilling and coordinated fracturing arrangement method and system for deep coal seam composite roof - Google Patents

Abstract

The present invention discloses a method and system for arranging directional long drilling holes for coordinated fracturing of composite roof of deep coal seam, which relates to the technical field of coal mining, including: determining the location of main key layers and sub-key layers according to actual collected data, combined with microseismic monitoring data and acoustic emission monitoring data; performing numerical simulation according to the location of main key layers and sub-key layers to determine the design layout height, design fracturing duration and design fracturing section length of directional long drilling holes; arranging directional long drilling trajectory according to the design layout height; performing segmented hydraulic fracturing or high-pressure jet fracturing on main key layers and sub-key layers in sequence according to the directional long drilling trajectory, the design fracturing duration and the design fracturing section spacing, to achieve coordinated fracturing. The technical solution of the present invention utilizes the key layer theory combined with microseismic, acoustic emission monitoring data and numerical simulation software to determine the design of key parameters such as drilling layer position, quantity and direction, improve the regional drilling fracturing effect, optimize the fracturing construction process, and save economic costs.

Description

Directional long drilling and coordinated fracturing arrangement method and system for deep coal seam composite roof

Technical Field

The present invention relates to the technical field of coal mining, and in particular to a method and system for arranging directional long drilling holes for coordinated fracturing of composite roofs of deep coal seams, which is particularly suitable for designing directional long drilling hole fracturing schemes in the field of coal seam roof pressure relief engineering, and improves regional fracturing effects.

Background Art

Directional long-hole regional fracturing technology is an engineering operation technology for regional hydraulic fracturing that uses a set of downhole directional long-distance drilling facilities, that is, a kilometer-long directional drilling rig equipped with wired or wireless measurement while drilling technology. It can provide real-time feedback during drilling, adjust and control the direction of the drill bit to achieve high-precision drilling and long-distance stable drilling, and realize the designed fracturing trajectory. The borehole length is usually more than 300m, and the fracturing range can cover the entire working surface area or even wider, which can avoid the shortcomings of conventional hydraulic fracturing in terms of fracturing depth, fracturing layer, and fracturing schedule.

At present, the application of this technology in roof pressure relief and outburst elimination projects mainly refers to the construction experience of gas control projects to design and arrange key parameters such as drilling construction layer and drilling trajectory. It lacks applicability for regional fracturing and pressure relief control projects of composite thick and hard roofs of deep coal seams. Under the conditions of the development of "high-low" composite roofs, the direct breaking of the low-level "cantilever beam" releases energy to act on the underlying coal and rock mass, accompanied by the breaking of the high-level thick and hard rock layer, and even coordinated rotation, which can easily cause impact dynamic disasters of the coal and rock mass within the scope of mining influence.

Summary of the invention

In order to solve the above problems, the technical solution of the present invention proposes a method and system for arranging directional long drilling holes for coordinated fracturing of deep coal seam composite roof, which is suitable for the anti-bumping management of strong ground pressure such as large-area hanging roof and large deformation of tunnels occurring in the process of deep coal seam mining. The key layer theory is combined with microseismic and acoustic emission monitoring data and numerical simulation software to determine the design of key parameters such as drilling layer position, number, and direction, improve the regional drilling and fracturing effect, optimize the fracturing construction process, and save economic costs.

According to a first aspect of the present invention, a method for arranging directional long drilling holes for coordinated fracturing in a deep coal seam composite roof is provided, wherein the method comprises:

Step 1: Determine the location of the main key layer and sub-key layer based on the actual collected data, combined with microseismic monitoring data and acoustic emission monitoring data;

Furthermore, the step 1 specifically includes:

Step 11: determining fracture zone theoretical data according to the actual collected data;

Furthermore, in step 11, the actual collected data are geological parameters and physical and mechanical parameters, including: lithology, layer height h, cumulative mining thickness , ground stress distribution, rock elastic modulus E, bulk density γ, moment of inertia I, and tensile strength σ.

Furthermore, in step 11, the fracture zone theoretical data is determined by the following formula:

When the rock type is hard, the following formula is used:

When the lithology is medium-hard, the following formula is used:

in, and Represents the theoretical data of fracture zone, unit is m; It is the cumulative thickness of the actual collected data.

Step 12: Determine the scope of the fracture zone and the scope of the collapse zone based on the fracture zone theoretical data, combined with the microseismic monitoring data and the acoustic emission monitoring data;

Step 13: Determine whether there is a composite thick hard rock layer in the fracture zone range and the collapse zone range, and the range is at least 100m higher than the coal seam. If not, use the actual collected data as key layer calculation data; if so, determine equivalent calculation data and use it as key layer calculation data;

Furthermore, in step 13, if the maximum height of the fracture zone is less than 100 m, it is determined whether there is a composite thick hard rock layer within the range of 100 m of rock layer overlying the mined coal seam.

Furthermore, in step 13, the equivalent calculation data is determined by the following formula:

The equivalent calculation data include: equivalent floor height , equivalent rock elastic modulus , equivalent bulk density , equivalent moment of inertia , equivalent tensile strength , the calculation formula is as follows:

in, , , They represent the layer height, rock elastic modulus, and bulk density of the i-th layer in the composite rock layer, with the units of m, GPa, and MN/m ^{3 ,} respectively; represents the moment of inertia of the i-th layer in the composite rock layer, which is a geometric quantity; σ _max represents the maximum tensile strength in the composite rock layer, in MPa; i=1,2,......n, n represents the total number of layers; Represents the total layer height of n layers of composite rock.

Step 14: determining the number of key layers according to the key layer calculation data, and determining the breaking distance of each key layer;

Furthermore, in step 14, the key layer is determined by:

Use the following discriminant formula to calculate from the first rock layer above the coal seam upwards, where the composite rock layer is considered as a whole rock layer:

in, Calculate the rock elastic modulus of the m+1th layer in the key layer data; Calculate the height of the m+1th layer in the data for the key layer; Calculate the height of the i-th layer in the data for the key layer; Calculate the bulk density of the i-th layer in the data for the key layer; The density of the m+1th layer in the key layer calculation data; Calculate the rock elastic modulus of the i-th layer in the data for the key layer;

When the discriminant is satisfied, the m+1th rock layer is the key layer 1, and the discrimination is repeated starting from the key layer 1 until the rock layer height is determined to be greater than the height of the fracture zone range and at least 100m higher than the coal seam.

Furthermore, in step 14, if the maximum height of the fracture zone is less than 100 m, it is determined that the rock layer height is at least 100 m higher than the mined coal layer.

Step 15: Determine the locations of the main key layer and the sub-key layer in turn according to the magnitude of the breaking distance.

Further, in step 15, the breaking distance of each key layer is calculated by the following formula:

in, , , m and _k represent the layer height, tensile strength and number of controlled soft rock layers of the kth rock layer in the key layer calculation data, respectively, in units of m and MPa;

is the load borne by the kth rock layer in the key layer calculation data, in MPa;

represents the rock elastic modulus of the kth rock layer, represents the stratified height of the k-th rock layer;

, _, They are the elastic modulus, layer height and bulk density of the jth rock layer in the soft rock layer group controlled by the kth rock layer in the key layer calculation data, and the units are GPa, m, MN/m ³ respectively.

Step 2: Performing numerical simulation according to the locations of the main key layers and sub-key layers to determine the design layout height, design fracturing time and design fracturing section length of the directional long drilling hole;

Furthermore, the step 2 specifically includes:

The fracture propagation behavior of directional long drilling fracturing at different positions of the main key layer and sub-key layer is simulated and analyzed using fracturing numerical software, and the boundary is set according to the ground stress distribution. The designed layout height of the directional long drilling, the designed fracturing time and the designed fracturing section spacing are then confirmed according to the fracture development length.

Furthermore, in step 2, the fracturing numerical software is COMSOL, XSite or ABAQUS.

Furthermore, the determination of the design layout height of the directional long drilling hole, the design fracturing time and the design fracturing section spacing according to the length of the fracture development is specifically as follows:

When the length of the crack development exceeds the height of the key layer in the model, that is, the crack penetrates the key layer to achieve the fracturing effect, the fracturing time is recorded at this time, and the fracturing time at different heights is compared. The shortest time is the design layout height of the directional long drilling, and this time is the designed fracturing time. At this time, the maximum lateral length of the crack expansion is the designed fracturing section spacing.

Step 3: Arranging a directional long drilling trajectory according to the designed arrangement height of the directional long drilling;

Furthermore, the directional long drilling trajectory includes a curved section and a horizontal section.

Furthermore, the step 3 specifically includes:

Step 31: according to the identification of the key rock layer overlying the target working face and according to the numerical simulation results, the horizontal section of the directional long drilling trajectory is arranged at a suitable height of the key layer, wherein the height of the horizontal section is equal to the designed arrangement height;

Step 32: In order to make the horizontal fracturing area cover the entire target working face, directional long drilling construction is carried out in the drilling site in the adjacent working face tunnel. The horizontal position of the drilling site is between 15 and 30 m outside the working face stop line, which serves as the starting position of the directional long drilling trajectory. The direction of the directional long drilling trajectory is arranged to be perpendicular to the working face direction. The fracturing area is the horizontal section, and the horizontal section covers the entire upper part of the target working face, part of the adjacent working face and the tunnel between the working faces.

Furthermore, the horizontal spacing of the directional long boreholes at different heights is 5-10 m, and is advanced into the stop-mining line as the height of the layer is arranged.

Step 4: Perform segmented hydraulic fracturing or high-pressure jet fracturing on the main key layer and sub-key layer in sequence according to the directional long drilling trajectory, the designed fracturing duration, and the designed fracturing segment spacing to achieve coordinated fracturing.

Furthermore, the step 4 also includes:

The main key layer is subjected to staged hydraulic fracturing. After the fracturing is completed, the return water volume of the directional long borehole at the lower position is observed, and different fracturing methods are adopted according to the return water volume and the degree of deformation in the borehole:

If the return water volume is large, the high-pressure jet fracturing is performed, and if the return water volume is small, the segmented hydraulic fracturing is performed.

According to a second aspect of the present invention, a system for arranging directional long drill holes and coordinated fracturing of composite roofs of deep coal seams is provided, the system comprising: a processor and a memory for storing executable instructions; wherein the processor is configured to execute the executable instructions to execute the method for arranging directional long drill holes and coordinated fracturing of composite roofs of deep coal seams as described in any of the above aspects.

According to a third aspect of the present invention, there is provided a computer-readable storage medium, characterized in that a computer program is stored thereon, and when the computer program is executed by a processor, the method for arranging directional long drilling holes for coordinated fracturing of composite roof of deep coal seams as described in any of the above aspects is implemented.

Beneficial effects of the present invention:

1. The method and system for arranging directional long drilling holes for coordinated fracturing of composite roof of deep coal seam of the present invention can be used to quantitatively identify the key strata in the thick hard coal seam overlying the mined coal seam that need to be treated urgently. According to the steps in the present invention, the key design parameters for the construction of directional long drilling holes can be determined. By designing directional long drilling holes of different heights for coordinated fracturing, the strength structure of the thick hard rock layer of the roof can be effectively weakened, so that a large area of suspended roof can collapse in advance and a funnel-shaped gradient stable structure can be formed, thereby reducing the energy release intensity of the dynamic and static load superposition in the key layers overlying the mining area, reducing the high stress of the surrounding rock on the tunnel, and preventing and controlling dynamic disasters in the mining area.

2. Utilizing the deep coal seam composite roof directional long drilling coordinated fracturing arrangement method and system of the present invention, a drilling site is arranged in the adjacent working face tunnel of the target treatment area to carry out directional long drilling trajectory construction, effectively avoiding the impact of engineering disturbance during fracturing construction on equipment and personnel, so that the fracturing area can completely cover the target treatment working face, improve the drilling utilization rate, simple operation, safe and efficient, and has wide practicality.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

FIG1 shows a flow chart of a method for arranging directional long drilling holes for coordinated fracturing of composite roof of deep coal seams according to an embodiment of the technical solution of the present invention.

FIG. 2 shows a schematic diagram of collaborative fracturing layers according to an embodiment of the technical solution of the present invention.

FIG. 3 shows a plan view of a drilling arrangement according to an embodiment of the technical solution of the present invention.

FIG. 4 shows a cross-sectional view of a drilling arrangement according to an embodiment of the technical solution of the present invention.

Figure 5a shows the tunnel condition after the fracturing operation, and Figure 5b shows the tunnel deformation data at a certain measuring point.

The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings.

DETAILED DESCRIPTION

Here, exemplary embodiments will be described in detail, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are only examples of devices and methods consistent with some aspects of the present disclosure.

The terms "first", "second", etc. in the present disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged where appropriate, so that the embodiments of the present disclosure described herein can, for example, be implemented in an order other than those illustrated or described herein.

In addition, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus that includes a series of steps or elements is not necessarily limited to those steps or elements explicitly listed, but may include other steps or elements not explicitly listed or inherent to such process, method, product, or apparatus.

Multiple includes two or more.

It should be understood that the term "and/or" used in this disclosure is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and/or B may represent: A exists alone, A and B exist at the same time, and B exists alone.

The technical solution of the present invention first provides a method for arranging directional long drilling holes for coordinated fracturing of composite roof of deep coal seams, comprising:

Step 101: According to the actual collected data, combined with the microseismic monitoring data and the acoustic emission monitoring data, the location of the main key layer and the sub-key layer is determined (construction of the collaborative fracturing geological model):

According to the geological parameters and physical and mechanical parameters of each rock layer in the working face, theoretical formulas are used for deduction and calculation, and the locations of main and sub-key layers are identified by combining microseismic and acoustic emission monitoring data to establish a collaborative fracturing geological model. The rock layer includes the main key layer and sub-key layer that control the whole or part of the rock movement. The model mainly includes coal seams, main and sub-key layers and other broken soft rock layers.

The geological data and physical and mechanical parameters of the target coal and rock strata to be managed need to be collected, including lithology, layer height h, cumulative mining thickness ∑M, ground stress distribution, and rock elastic modulus E, bulk density γ, moment of inertia I, and tensile strength σ.

The following formula is used to theoretically calculate the height range of the fracture water guide zone:

When the rock type is hard, the following formula is used:

Wherein, H _Li1 and H _Li2 represent the theoretical data of fracture zone, unit is m;

When the lithology is medium-hard, the following formula is used:

After obtaining the theoretical data, reasonable calculation results are selected in combination with microseismic and acoustic emission monitoring data. At this time, the area below the fracture zone to the mined coal seam is the collapse zone range, thereby determining the fracture zone range and collapse zone range respectively.

Among them, microseismic monitoring will collect seismic waves generated by tiny fractures or movements inside the coal rock layer. By analyzing the arrival time, amplitude, frequency and waveform characteristics of these seismic waves, the location, time and intensity of energy events inside the rock mass can be inferred. Acoustic emission monitoring is similar to microseismic monitoring, except that the monitoring object is sound waves. Based on the above data, the active area of energy events in the overlying coal rock layer can be obtained, and these energy events usually occur in special geological structural zones of the coal rock layer, namely the collapse zone and the fracture zone.

Here, when there are two or more rock layers that have not dislocated before breaking, they are composite rock layers. Simple identification can be achieved through observation of borehole columnar stratigraphic diagrams. If there is a weaker rock layer between two or more thick and hard rock layers, and its height is less than half of the sum of the heights of the thick and hard rock layers, or the strength difference between two or more thick and hard rock layers is not large, they can be regarded as composite thick and hard rock layers. Specific identification can be achieved by calculating the maximum shear force on the bedding contact surface and the maximum shear strength of the rock layer when two or more rock layers are broken. When the shear force is less than or equal to the shear strength, it is a composite thick and hard rock layer.

Use the following formula to determine the overlying composite thick hard rock layer:

When there is a composite thick hard rock layer, it is necessary to perform equivalent calculation on the lithology parameters of the composite rock layer to obtain the equivalent layer height. , equivalent rock elastic modulus , equivalent bulk density , equivalent moment of inertia , equivalent tensile strength , the calculation formula is as follows:

in, , , They represent the layer height, rock elastic modulus, and bulk density of the i-th layer in the composite rock layer, with the units of m, GPa, and MN/m ^{3 ,} respectively; represents the moment of inertia of the i-th layer in the composite rock layer, which is a geometric quantity; σ _max represents the maximum tensile strength in the composite rock layer, in MPa; i=1,2,......n, n represents the total number of layers; Represents the total layer height of n layers of composite rock.

Use the following discriminant formula to calculate from the first rock layer above the coal seam upwards, where the composite rock layer is considered as a whole rock layer:

in, Calculate the rock elastic modulus of the m+1th layer in the key layer data; Calculate the height of the m+1th layer in the data for the key layer; Calculate the height of the i-th layer in the data for the key layer; Calculate the bulk density of the i-th layer in the data for the key layer; The density of the m+1th layer in the key layer calculation data; Calculate the rock elastic modulus of the i-th layer in the data for the key layer;

When the discriminant is satisfied, the m+1th rock layer is the key layer 1, and the discrimination is repeated starting from the key layer 1 until the rock layer height is determined to be greater than the height of the fracture zone range and at least 100m higher than the coal seam.

Use the following formula to calculate the breaking distance of each key layer:

in, , , m and _k represent the layer height, tensile strength and number of controlled soft rock layers of the kth rock layer in the key layer calculation data, respectively, in units of m and MPa;

is the load borne by the kth rock layer in the key layer calculation data, in MPa;

represents the rock elastic modulus of the kth rock layer, represents the stratified height of the k-th rock layer;

, _, They are the elastic modulus, layer height and bulk density of the jth rock layer in the soft rock layer group controlled by the kth rock layer in the key layer calculation data, and the units are GPa, m, MN/m ³ respectively.

The above theoretical calculation results can be used to identify the main and sub-key layers in the overlying rock formations on the working face, and combined with other formation data to construct a collaborative fracturing geological model.

Step 102: Numerical simulation is performed based on the locations of the main key layers and sub-key layers to determine the design layout height, design fracturing duration, and design fracturing section length of the directional long borehole (determine the key parameters of the borehole layout):

The fracturing numerical software is used to simulate and analyze the fracture expansion behavior of the boreholes at different locations of the key layer, and the drilling design layout height, fracturing duration, and fracturing section spacing are confirmed according to the fracture expansion situation.

Here, according to the relevant data of the established collaborative fracturing geological model, the numerical model of each key layer is established. At this time, the key layer height of the numerical model should be higher than the layer height in the geological model. The boreholes are arranged at different heights of the key layer to simulate the hydraulic fracturing process. When the maximum vertical length of the fracture development exceeds the key layer height in the model, that is, the fracture penetrates the key layer to achieve the fracturing effect, the fracturing time is recorded at this time, and the fracturing time at different heights is compared. The shortest time is the designed arrangement height of the borehole, and this time is also the designed fracturing time. At this time, the maximum lateral length of the fracture development is the designed fracturing section spacing.

Step 103: Arrange the directional long drilling trajectory (drilling site layout and drilling trajectory layout) according to the designed layout height of the directional long drilling:

The drilling site is arranged in the tunnel adjacent to the working face, with the horizontal position between 15 and 30 m outside the stop-production line of the working face. During construction, the drilling trajectory is arranged in a direction perpendicular to the direction of the working face. The total design trajectory consists of a curved section and a horizontal section. The fracturing area is the horizontal section. The horizontal section covers the entire upper part of the target working face, part of the adjacent working face and the tunnel between the working faces. Based on the identification of the key rock formations overlying the target working face and the results of numerical simulation, the boreholes are arranged at a suitable height. The horizontal spacing of boreholes at different heights is 5 to 10 m, and they advance into the stop-production line as the height of the arranged layer increases.

Step 104: Perform staged hydraulic fracturing or high-pressure jet fracturing on the main key layer and the sub-key layer in sequence according to the directional long drilling trajectory, the designed fracturing duration, and the designed fracturing segment spacing to achieve coordinated fracturing (coordinated fracturing design):

After the drilling construction is completed, the high-level main key layer is first subjected to segmented hydraulic fracturing. The fracturing duration and the spacing between fracturing sections are set according to the numerical simulation results. After the fracturing is completed, the water return of the low-level borehole is observed. If water return occurs, it means that the hydraulic fracture has been connected. Different fracturing methods are used according to the amount of water return and the degree of deformation in the borehole. A large amount of water return and severe borehole deformation indicate that the fracture network between the rock layers is relatively well developed. At this time, high-pressure jet fracturing is used, otherwise segmented hydraulic fracturing is carried out. After the high-level key layer is fracturing, the interaction between hydraulic fractures and primary fractures will weaken the rock structure. When the fracture network is rich to a certain extent, the thick and hard rock layer will break, releasing the accumulated elastic energy in advance. Since the fracturing holes in the high and low key layers are at different levels, with the construction of the fracturing operation, the high and low thick and hard rock layers are gradually broken, and the low-level roof begins to collapse due to the stress caused by the change of the rock structure above and is re-compacted in the goaf, forming a funnel-shaped stable structure, which improves the high stress distribution in the mining area, alleviates the high bearing pressure of the large tunnel, reduces the maintenance cost of the large tunnel, and achieves a coordinated pressure relief and anti-impact effect.

Example

The vertical depth of the working face in a certain mining area from the ground is about 300-460m. The strike length of mining is 1102-1092m, the dip length is 220m, the height of the mined coal seam is 3.8-4.6m, and the average layer height is 4.8m. The coal seam dip angle is 2°～7°, with an average dip angle of 4°. When the coal seam is mined near the stop mining line, a large area of suspended roof appears due to the failure of the roof to fully collapse. The large tunnels near the mining area are significantly deformed under the high support pressure. According to microseismic monitoring and support pressure monitoring, it is found that there is a "high-frequency and high-energy" strong ground pressure, which seriously affects the safe and efficient production of the entire mine. It is necessary to transform the thick hard rock structure on the working face to reduce the engineering impact caused by the strong mine pressure.

Through data analysis, the overlying rock structure of the working face and the lithological parameter data of the corresponding rock layers required in the calculation project were obtained, and the main and sub-key layers were calculated and identified. According to the borehole columnar diagram, it was found that there were multiple thick hard rock layers in the overlying rock layer of the working face, among which the direct top was a 10m high sandstone, which was a sub-key layer. There was a composite thick hard rock layer 45m-80m away from the coal seam, and the specific composition was a sandstone-mudstone-sandstone structure, among which the top sandstone layer was 17m high, the middle mudstone layer was 5m high, and the lower sandstone layer was 13m high. According to the calculation results of the formula, it was determined to be the main key layer. There was also a sandstone with a layer height of 12m between the direct top sub-key layer and the main key layer. According to the calculation results of the formula, it was determined to be a sub-key layer. There was also a thick hard rock layer above the main key layer, but after calculation, its control effect on the rock layer was weaker than that of the composite thick hard rock layer. Finally, according to the above data, a collaborative fracturing geological model as shown in Figure 2 was established. Using numerical simulation software (such as COMSOL, which can provide simulation effect diagrams and curves of the longitudinal length and lateral width of the crack changing with time), the directional long borehole fracturing process is simulated according to the identified different key layers, and the corresponding lithological parameters are input to establish a numerical model. The boundary conditions are set according to the distribution of ground stress, and the directional long boreholes are arranged at different positions of the key layer. When the directional long borehole is arranged at the middle height of the key layer, the fracturing time is the shortest, and the maximum lateral distance of the crack expansion under the fracturing time is obtained. In order to design the fracturing section spacing, the key layer model parameters and the ground stress boundary conditions are changed to obtain the fracturing design height, fracturing time and fracturing section spacing of the three directional long boreholes. Next, the key parameters of directional long drilling are set and constructed. The boreholes are arranged in the adjacent working face, outside the stop-mining line. The direction of the directional long drilling trajectory is perpendicular to the mining direction of the working face. According to the results of numerical simulation, the directional long boreholes are arranged at different heights, numbered H1, H2, and H3 respectively. The horizontal spacing of the boreholes is 5m, and they are advanced gradually into the stop-mining line according to the height of the arranged layer. The directional long drilling trajectory consists of a curved section and a horizontal section, wherein the horizontal section is the fracturing area. Figure 3 shows the plan view of the coordinated fracturing arrangement of directional long drilling holes in the composite roof of a deep coal seam, and Figure 4 shows the cross-sectional view of the coordinated fracturing arrangement of directional long drilling holes in the composite roof of a deep coal seam. First, segmented hydraulic fracturing was carried out on the directional long borehole H3 of the high-position main key layer. The key fracturing parameters such as fracturing duration and fracturing section spacing were set according to the numerical simulation results. After the construction of the high-position main key layer was completed, the water return in the borehole of the low-position sub-key layer was observed. It was found that a large amount of water return occurred in the directional long borehole H2, and the deformation in the hole was serious. The fracturing method was changed to high-pressure jet fracturing. There was only a small amount of water return in the directional long borehole H1, and the hole wall was relatively intact. The segmented hydraulic fracturing construction continued.

After the coordinated fracturing construction was completed, the monitoring data of tunnel deformation, support resistance, etc. showed that compared with the working face without fracturing construction, the main roadway maintained good stability during the mining and finishing process of the working face, with a deformation of less than 100mm, and the frequency of support pressure increased, but the strength decreased by about 15% year-on-year, and the suspended roof of the goaf area gradually collapsed. According to the above steps, the main and sub-key layers of the deep coal seam composite roof were coordinated by fracturing. After the construction, the dangerous structure of the overlying rock strata on the working face was transformed, the strength of the composite thick and hard rock strata was weakened, and the large amount of elastic energy accumulated in the thick and hard rock strata was released in advance, so that the suspended top rock strata in the collapse zone could be gradually broken and collapsed, so that the high stress distribution in the mining area was improved, the high support pressure of the main roadway was relieved, and the maintenance cost of the main roadway was reduced, achieving the coordinated pressure relief and anti-bumping effect.

The effect is shown in Figure 5a-5b. Figure 5a shows the tunnel condition after the fracturing operation, and Figure 5b is a tunnel deformation data diagram at a certain measuring point. As shown in the figure, the surface displacement deformation of the tunnel roof, floor and left and right tunnel walls are all less than 100 mm.

In summary, the present invention proposes a method and system for arranging directional long boreholes for collaborative fracturing in composite roofs of deep coal seams, which is mainly based on the key layer identification theory, through theoretical analysis of the heights of the "upper two zones" of the coal seam, namely the collapse zone and the fracture water conduction zone, combined with microseismic monitoring data to identify the composite situation of the main and sub-key layers and thick hard rock layers, determine the overlying rock layer treatment area, and use numerical simulation software to determine the key parameters of the borehole arrangement, arrange the borehole heights in different thick hard rock layers for collaborative fracturing, start directional drilling from the adjacent working face, so that the directional long borehole can cover the entire target working face, and carry out collaborative fracturing on the overlying main key layer and sub-key layer, so as to achieve the regionalized pressure relief and outburst elimination treatment effect.

It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

Through the description of the above implementation methods, those skilled in the art can clearly understand that the above implementation method can be implemented by means of software plus a necessary general hardware platform, or by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM/RAM, magnetic disk, optical disk), and includes a number of instructions for a terminal (which can be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in each embodiment of the present invention.

The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the purpose of the present invention, which are all within the protection of the present invention.

Claims (9)

1. A method for arranging directional long drilling holes for coordinated fracturing of composite roof of deep coal seams, characterized in that the method comprises: Step 1: Determine the location of the main key layer and sub-key layer based on the actual collected data, combined with microseismic monitoring data and acoustic emission monitoring data; Step 2: Performing numerical simulation according to the locations of the main key layers and sub-key layers to determine the design layout height, design fracturing time and design fracturing section length of the directional long drilling hole; Step 3: Arranging the directional long drilling trajectory according to the designed arrangement height of the directional long drilling; Step 4: performing segmented hydraulic fracturing or high-pressure jet fracturing on the main key layer and sub-key layer in sequence according to the directional long drilling trajectory, the designed fracturing duration and the designed fracturing segment spacing to achieve coordinated fracturing. Wherein, the step 1 specifically includes: Step 11: Determine the fracture zone theoretical data based on the actual collected data, wherein the actual collected data are geological related parameters and physical and mechanical parameters, including: lithology, layer height h, cumulative mining thickness , distribution of ground stress and rock elastic modulus E, bulk density γ, moment of inertia I, and tensile strength σ; Step 12: Determine the scope of the fracture zone and the scope of the collapse zone based on the fracture zone theoretical data, combined with the microseismic monitoring data and the acoustic emission monitoring data; Step 13: Determine whether there is a composite thick hard rock layer in the fracture zone range and the collapse zone range, and the range is at least 100m higher than the coal seam. If not, use the actual collected data as key layer calculation data; if so, determine equivalent calculation data and use it as key layer calculation data; Step 14: determining the number of key layers according to the key layer calculation data, and determining the breaking distance of each key layer; Step 15: Determine the locations of the main key layer and the sub-key layer in turn according to the magnitude of the breaking distance. 2. The method for arranging directional long drilling holes for coordinated fracturing of deep coal seam composite roof according to claim 1, characterized in that in step 11, the theoretical data of the fracture zone is determined by the following formula: When the rock type is hard, the following formula is used: When the lithology is medium-hard, the following formula is used: in, and Represents the theoretical data of fracture zone, unit is m; It is the cumulative thickness of the actual collected data. 3. The method for arranging directional long drilling holes for coordinated fracturing of composite roof of deep coal seams according to claim 1, characterized in that in step 13, the equivalent calculation data is determined by the following formula: The equivalent calculation data include: equivalent floor height , equivalent rock elastic modulus , equivalent bulk density , equivalent moment of inertia , equivalent tensile strength , the calculation formula is as follows: in, , , They represent the layer height, rock elastic modulus, and bulk density of the i-th layer in the composite rock layer, with the units of m, GPa, and MN/m ^{3 ,} respectively; represents the moment of inertia of the i-th layer in the composite rock layer, which is a geometric quantity; σ _max represents the maximum tensile strength in the composite rock layer, in MPa; i=1,2,......n, n represents the total number of layers; Represents the total layer height of n layers of composite rock. 4. The method for arranging directional long drilling holes for coordinated fracturing of deep coal seam composite roof according to claim 1, characterized in that in step 14, the key layer is determined by the following method: Use the following discriminant formula to calculate from the first rock layer above the coal seam upwards, where the composite rock layer is considered as a whole rock layer: in, Calculate the rock elastic modulus of the m+1th layer in the key layer data; Calculate the height of the m+1th layer in the data for the key layer; Calculate the height of the i-th layer in the data for the key layer; Calculate the bulk density of the i-th layer in the data for the key layer; The density of the m+1th layer in the key layer calculation data; Calculate the rock elastic modulus of the i-th layer in the data for the key layer; When the discriminant is satisfied, the m+1th rock layer is the key layer 1, and the discrimination is repeated starting from the key layer 1 until the rock layer height is determined to be greater than the height of the fracture zone range and at least 100m higher than the coal seam. 5. The method for arranging directional long drilling holes for coordinated fracturing of composite roof of deep coal seam according to claim 1, characterized in that in said step 14, the breaking distance of each key layer is calculated by the following formula: in, , , m and _k represent the layer height, tensile strength and number of controlled soft rock layers of the kth rock layer in the key layer calculation data, respectively, in units of m and MPa; is the load borne by the kth rock layer in the key layer calculation data, in MPa; represents the rock elastic modulus of the kth rock layer, represents the stratified height of the k-th rock layer; They are the elastic modulus, layer height and bulk density of the jth rock layer in the soft rock layer group controlled by the kth rock layer in the key layer calculation data, and the units are GPa, m, MN/m ³ respectively. 6. The method for arranging directional long drilling holes for coordinated fracturing of composite roof of deep coal seams according to claim 1, characterized in that said step 2 specifically comprises: The fracture propagation behavior of directional long drilling for fracturing at different positions of the main key layer and sub-key layer is simulated and analyzed by using fracturing numerical software, and the boundary is set according to the distribution of ground stress. Then, the design layout height of directional long drilling, the design fracturing time and the design fracturing section spacing are determined according to the length of fracture development. The method for determining the design layout height of the directional long drilling hole, the design fracturing time and the design fracturing section spacing according to the length of the fracture development is specifically as follows: When the length of the crack development exceeds the height of the key layer in the model, that is, the crack penetrates the key layer to achieve the fracturing effect, the fracturing time is recorded at this time, and the fracturing time at different heights is compared. The shortest time is the design layout height of the directional long drilling, and this time is the designed fracturing time. At this time, the maximum lateral length of the crack expansion is the designed fracturing section spacing. 7. The method for arranging directional long drilling holes for coordinated fracturing of deep coal seam composite roof according to claim 1, characterized in that step 3 specifically comprises: Step 31: according to the identification of the key rock formation overlying the target working face and according to the numerical simulation results, the horizontal section of the directional long drilling trajectory is arranged at the designed arrangement height of the key layer, wherein the directional long drilling trajectory includes a curved section and a horizontal section; Step 32: In order to make the horizontal fracturing area cover the entire target working face, directional long drilling construction is carried out in the drilling site in the adjacent working face tunnel. The horizontal position of the drilling site is between 15 and 30 m outside the working face stop line, which serves as the starting position of the directional long drilling trajectory. The direction of the directional long drilling trajectory is arranged to be perpendicular to the working face direction. The fracturing area is the horizontal section, and the horizontal section covers the entire upper part of the target working face, part of the adjacent working face and the tunnel between the working faces. 8. A system for arranging directional long drill holes and coordinated fracturing of composite roofs of deep coal seams, the system comprising: a processor and a memory for storing executable instructions; characterized in that the processor is configured to execute the executable instructions to execute the method for arranging directional long drill holes and coordinated fracturing of composite roofs of deep coal seams according to any one of claims 1 to 7. 9. A computer-readable storage medium, characterized in that a computer program is stored thereon, and when the computer program is executed by a processor, the method for arranging directional long drilling holes for coordinated fracturing of deep coal seam composite roof according to any one of claims 1 to 7 is implemented.