A coal mine underground long borehole staged fracturing method for promoting balanced crack propagation

Abstract

The application discloses a coal mine underground long borehole staged fracturing method for promoting balanced expansion of cracks, which comprises the following steps: designing construction parameters of one or more directional long boreholes in a laid layer position; constructing one or more directional long boreholes in the laid layer position; cementing a borehole after lowering a casing string with a soluble hole section; constructing a ground through well and a coal mine underground roadway through well, lowering a tubing into the ground through well; laying a high-pressure fluid conveying pipeline in the coal mine underground; determining a balanced expansion coefficient F according to collected reservoir parameters and designed construction parameters; determining a fracturing construction mode according to the determined balanced expansion coefficient F; stopping pumping after completing the fracturing construction, and releasing and spraying at a borehole opening of the coal mine underground long borehole; and completing fracturing construction operations of all directional long boreholes in the laid layer position. The application realizes multi-stage fracturing of the underground long borehole by relying on ground fracturing construction equipment, can significantly improve fracturing effect, promotes balanced expansion of cracks around the borehole, and guarantees gas extraction effect in the later period.

Description

Technical Field

[0001] This invention relates to the field of coal mine gas extraction, and to a method for underground fracturing in coal mines, specifically a method for segmented fracturing of long boreholes in coal mines to promote the balanced propagation of fractures. Background Technology

[0002] Coal seams in my country are generally low-permeability, making gas extraction difficult. Hydraulic fracturing is often necessary to enhance permeability and improve gas extraction efficiency. Engineering practice shows that segmented fracturing of long boreholes in coal mines is an effective measure for enhancing coal seam permeability and regional gas extraction. However, due to the limited working space in coal mines, existing fracturing operations suffer from low flow rates, low sand ratios, and ineffective fracture support. To improve fracturing efficiency, a combined surface and underground fracturing technology has been proposed. This technology connects the surface to the underground mine roadways through a connecting shaft, and fracturing fluid delivery pipelines are laid within the roadways to introduce surface fracturing fluid into the underground mine. Relying on mature surface fracturing equipment, high-flow-rate fracturing operations are achieved through long boreholes in the underground mine. For this combined surface and underground fracturing operation model, segmented fracturing is the key to its success. Existing fracturing construction technology mainly uses tubing or coiled tubing to send the tool string into long boreholes in coal mines. The segmented fracturing construction of long boreholes is achieved through mechanical isolation. Its drawbacks are: small working space in coal mines, relatively complex process flow, frequent personnel operation, and high labor intensity for workers.

[0003] To address the above problems, this invention improves the construction process and proposes a segmented fracturing method for long underground boreholes in coal mines that promotes uniform crack propagation. This method enables segmented fracturing operations of long directional boreholes in coal mines, reduces construction steps, and improves construction efficiency. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for segmented fracturing of long boreholes in coal mines that promotes uniform fracture propagation, thereby solving the technical problems of complex construction processes and low construction efficiency in existing technologies for segmented fracturing of long directional boreholes in coal mines.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A staged fracturing method for long boreholes in coal mines that promotes uniform fracture propagation includes the following steps:

[0007] Step 1: Collect reservoir parameters of the target mining area, determine the layout of directional long boreholes based on the collected reservoir parameters, and complete the construction parameter design for one or more directional long boreholes within the layout layout.

[0008] Step 2: Construct one or more directional long boreholes within the determined layout layer;

[0009] Step 3: Insert a casing string with a soluble perforated section into the directional long borehole, and then cement the hole to solidify it.

[0010] Step 4: Connect the surface well to the underground roadway of the coal mine. After cementing the surface well with casing, run the tubing into the surface well.

[0011] Step 5: Lay high-pressure fluid transport pipelines underground in the coal mine. The high-pressure fluid transport pipelines are respectively connected to the oil pipe openings in the surface penetrating well and the four-way connectors at the openings of the directional long boreholes.

[0012] Step 6: Construct a fracturing numerical simulation model using numerical simulation software. Then, based on the collected reservoir parameters and designed construction parameters, calculate the simulated fracture propagation length at each soluble perforation sub-section or the simulated total fracturing fluid volume at each soluble perforation sub-section, thereby determining the equilibrium propagation coefficient F. Based on the determined equilibrium propagation coefficient F, determine the fracturing construction method:

[0013] If F≤0.8, it is considered that the fractures in multiple perforation sections can expand evenly, and the entire hole is subjected to one-time fracturing operation.

[0014] If F > 0.8, it is considered that the fractures in some of the multiple perforation sections cannot be effectively extended, and temporary plugging and segmented fracturing construction should be carried out.

[0015] Step 7: After the fracturing operation is completed, stop the pump and release the blowout at the opening of the long borehole in the coal mine.

[0016] Step 8: Repeat steps 3 to 7 until the fracturing operation of all directional long boreholes within the layout layer is completed.

[0017] The present invention also has the following technical features:

[0018] Specifically, the soluble perforated section mentioned in step 2 includes a section body, on which a plurality of soluble perforations capable of dissolving in acid are equally spaced along the circumference, and the diameter of the soluble perforations is 10-20 mm.

[0019] Furthermore, the soluble perforated section described in step 3 is located at the perforation position, and adjacent soluble perforated sections are connected by a sleeve.

[0020] Furthermore, the numerical simulation software includes Abaqus and Kinetix.

[0021] Furthermore, the reservoir parameters include coal seam rock mechanics parameters, roof rock mechanics parameters, and geostress parameters, and the construction parameters include fracturing operation displacement and short-section spacing between adjacent soluble pores.

[0022] Furthermore, the equalization expansion coefficient F mentioned in step 6 is determined by the following formula:

[0023] or

[0024] In the formula,

[0025] F is the equilibrium expansion coefficient;

[0026] L i Let be the simulated crack propagation length at the location of the i-th soluble pore nodule, in meters, where i is a positive integer and i = 1...N;

[0027] Q i This is the simulated total amount of fracturing fluid entering the i-th soluble perforation sub-section, in m³. 3 ;

[0028] N represents the number of soluble perforated subsections.

[0029] Furthermore, step 6, which describes the implementation of a single-stage fracturing operation for the entire borehole, specifically includes:

[0030] Step 6.1: Inject pre-acid solution into the directional long borehole and let the well sit for 24–36 hours; the injection volume of pre-acid solution is determined by the following formula:

[0031] V sy =H s ×0.25×π×d tn 2

[0032] In the formula,

[0033] V sy This refers to the injection volume of pre-acid solution, in cubic meters (m³). 3 ;

[0034] H s The length of the horizontal section of a directional long borehole is expressed in meters (m).

[0035] d tn The inner diameter of the casing for directional long boreholes, in meters (m).

[0036] Step 6.2: Inject fracturing fluid from the surface using the designed fracturing operation displacement. The injection volume of fracturing fluid is determined by the following formula:

[0037] V yl = N×(200~300)

[0038] In the formula,

[0039] V yl This refers to the injection volume of fracturing fluid, measured in meters (m). 3 ;

[0040] N represents the number of soluble perforated subsections.

[0041] Furthermore, step 6, which describes the implementation of temporary plugging staged fracturing, specifically includes:

[0042] Step 6.1: Inject pre-acid solution into the directional long borehole and let the well sit for 24–36 hours; the injection volume of pre-acid solution is determined by the following formula:

[0043] V sy =H s ×0.25×π×d tn 2

[0044] In the formula,

[0045] V sy This refers to the injection volume of pre-acid solution, in cubic meters (m³). 3 ;

[0046] H s The length of the horizontal section of a directional long borehole is expressed in meters (m).

[0047] d tn The inner diameter of the casing for directional long boreholes, in meters (m).

[0048] Step 6.2: Using the designed fracturing operation displacement, inject fracturing fluid from the surface to perform the first fracturing operation of the entire borehole. The injection volume of fracturing fluid is 200-300 m³. 3 ;

[0049] Step 6.3: Inject rope knot temporary sealant to temporarily seal the opened pressure crack opening;

[0050] Among them, the amount N of knot-stopping agent added at one time s The total number of pores N of a single soluble pore section p The relationship between them satisfies the following equation:

[0051] N s = (1.2~1.5)×N p

[0052] in,

[0053] N s This refers to the number of temporary knot sealants added at one time.

[0054] N p The number of pores on a single soluble pore section;

[0055] Step 6.4: Inject fracturing fluid from the surface to perform a second fracturing operation. The injection volume of fracturing fluid is 200–300 m³. 3 ;

[0056] Step 6.5: Repeat steps 6.3 to 6.4 until the temporary plugging and segmented fracturing construction of all fracturing sections is completed.

[0057] Compared with the prior art, the beneficial effects of the present invention are:

[0058] (1) The method of the present invention relies on ground fracturing construction equipment to realize multi-stage fracturing of long boreholes in coal mines, which can significantly improve the fracturing effect and effectively support the fractures after fracturing. The method of the present invention introduces a fracture uniform expansion coefficient. The uniform expansion coefficient calculated based on numerical simulation results is used to determine whether the fracturing construction process is to perform full-hole fracturing or temporary plugging segmented fracturing. This can ensure that the fractures of all fracturing segments after long borehole fracturing construction are uniformly expanded, thereby achieving uniform gas extraction.

[0059] (2) The present invention uses a soluble perforated short section for solidification and injects acid solution to corrode and open the perforation hole, thereby reducing the perforation process.

[0060] (3) The present invention adopts a coal mine underground temporary plugging agent addition system to realize the addition of temporary plugging agent. Compared with the direct addition of temporary plugging agent on the ground, it can avoid the long-distance movement of temporary plugging agent in the fracturing fluid delivery pipeline and ensure the reliability of temporary plugging agent addition. Attached Figure Description

[0061] The accompanying drawings are provided to further understand the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof.

[0062] Figure 1 This is a flowchart of the well-ground combined fracturing operation method of the present invention;

[0063] Figure 2 A schematic diagram of a soluble perforated short section structure with 60-degree and 120-degree phase perforations;

[0064] Figure 3 Schematic diagram of a soluble perforated short section with a 60-degree spiral perforation.

[0065] Figure 4 This is a schematic diagram of a sleeve string structure with a soluble perforated section.

[0066] The labels in the diagram represent:

[0067] 1-Short section body; 2-Soluble perforation; 3-Sheath.

[0068] The specific content of the present invention will be further explained in detail below with reference to the accompanying drawings and specific embodiments. Detailed Implementation

[0069] The embodiments described below are only some embodiments of the present invention, not all embodiments, and do not limit the present invention in any way. Any technical solutions using the present embodiments, including simple changes to the present embodiments, are within the scope of protection of the present invention.

[0070] Unless otherwise specified, the construction equipment used in this invention are all existing equipment.

[0071] The following explains the technical terms used in this solution:

[0072] Directional long borehole: refers to a borehole with a main hole depth of more than 200 meters, covering a working face of the mine and the roadways on both sides.

[0073] Coal seam roof strata: refers to the collective term for several rock strata within a certain distance range above the coal seam.

[0074] Spacing between adjacent soluble perforated short sections: In a sleeve string with soluble perforated short sections, the soluble perforated short sections are connected by coaxially arranged sleeves with the same diameter as the soluble perforated short sections. The length of the sleeve connecting two adjacent soluble perforated short sections is called the spacing between adjacent soluble perforated short sections.

[0075] One-time fracturing of the entire borehole: The entire borehole is treated as the object of fracturing operation. Fracturing fluid is injected at once to achieve one-time fracturing operation of multiple fracturing sections in the entire borehole.

[0076] The technical concept of this invention is as follows: One or more directional long boreholes are drilled underground in a coal mine, and casing strings with soluble perforated sections are installed and cemented to solidify the boreholes. Then, a connecting shaft is constructed on the surface to connect with the roadway, and a high-pressure transmission pipeline is laid underground and connected to the borehole's four-way junction. A fracture uniform propagation coefficient is introduced, and based on the uniform propagation coefficient calculated from numerical simulation results, the fracturing process is determined to be either full-bore fracturing or temporary plugging segmented fracturing, ensuring uniform fracture propagation in all fracturing segments after the long borehole fracturing operation. After fracturing, blowout and gas extraction are carried out. Only when the fractures around the borehole propagate uniformly can the gas extraction around the borehole be more uniform; otherwise, uneven gas extraction around the borehole due to different fracture propagation lengths will result in gaps in gas extraction, thus posing a safety hazard to subsequent coal mining activities.

[0077] Example 1

[0078] Following the above technical solution, such as Figure 1 As shown, this embodiment provides a method for staged fracturing of long boreholes in coal mines to promote uniform fracture propagation, including the following steps:

[0079] Step 1: Collect reservoir parameters of the target mining area, determine the layout of directional long boreholes based on the collected reservoir parameters, and complete the construction parameter design for multiple directional long boreholes within the layout layout; including determining the perforation location, perforation size and number; the reservoir parameters include coal seam rock mechanics parameters, roof rock mechanics parameters, and in-situ stress parameters; the construction parameters include fracturing operation displacement, short-section spacing between adjacent soluble perforations, etc.

[0080] Step 2: Drill a long directional borehole within the determined layout layer;

[0081] Step 3: Insert a casing string with a soluble perforated section into the directional long borehole, and then cement the hole to solidify it.

[0082] The casing string used in this embodiment includes, from bottom to top, a guide shoe, a first casing group, a first soluble perforated section, a second casing group, a second soluble perforated section, a third casing group... the Nth soluble perforated section, the N+1th casing group, until the borehole. Each casing group contains 6 to 15 casings, and the length of a single casing is 3 meters. The outer diameter of the soluble perforated section is the same as that of the casing, and its length is 1 to 1.5 meters. Roller-type centralizers are installed at intervals outside the casing string to ensure that the casing can be centered in the directional long borehole and to reduce the pushing resistance applied to the casing by the directional long borehole. The soluble perforated section is set at the perforation position, and adjacent soluble perforated sections are connected by casings. One soluble perforated section is set at each preset perforation position.

[0083] like Figure 2 As shown, the soluble perforated section includes a section body, on which a plurality of soluble perforations capable of dissolving in acid are equally spaced along the circumference. The diameter of the soluble perforations is 10-20 mm, and the soluble perforated section is connected to the connected sleeve by a thread.

[0084] Dissolvable perforation subs with different perforation patterns can be selected according to the application of directional long drilling:

[0085] If the directional long borehole is a gas drainage borehole, and the horizontal section of the directional long borehole is located in the coal seam, then the soluble perforation short section should use a 60-degree spiral perforation pattern. Figure 3 As shown;

[0086] If the directional long borehole is a gas drainage borehole, and the horizontal section of the directional long borehole is in the roof strata adjacent to the coal seam, then the soluble perforation short section should use a 90-degree or 120-degree phase directional layout, such as... Figure 2 As shown; using 90-degree or 120-degree phase orientation holes means that two rows of holes are symmetrically set at the bottom of the casing, and the included angle between the two rows of holes on the casing cross section is 90 degrees or 120 degrees.

[0087] If the directional long borehole is a rockburst control borehole for hard roof type, then the soluble hole short section adopts a 60-degree spiral hole layout.

[0088] Cement grout is injected from inside the casing. Once the designed amount of cement grout is reached, conventional mud is used to replace the cement at the borehole opening. The cement grout is then returned through the annulus, the borehole opening is sealed, and the cement grout is allowed to solidify.

[0089] When the final depth of a long borehole is less than or equal to 500m, the cement slurry should be allowed to set for no less than 48 hours; when the final depth of a long borehole is greater than 500m, the cement slurry should be allowed to set for no less than 72 hours.

[0090] Step 4: Connect the surface well to the underground roadway of the coal mine. After cementing the surface well with casing, run the tubing into the surface well.

[0091] Step 5: Lay a high-pressure fluid transport pipeline underground in the coal mine. The high-pressure fluid transport pipeline is connected to the oil pipe opening in the surface well and the four-way connector of the directional long borehole. The surface well can be an existing cable hole or hydrological observation hole in the coal mine. The surface well can be a vertical well, a directional well, or other well types.

[0092] Step 6: Using existing numerical simulation software, such as Abaqus or Kinetix, construct a fracturing numerical simulation model that fully couples the shaft and the formation. The numerical simulation model includes a two-dimensional model and a three-dimensional model.

[0093] Then, based on the collected reservoir parameters and the designed construction parameters, the simulated value of the fracture propagation length at each soluble perforation sub-section or the simulated value of the total fracturing fluid volume at each soluble perforation sub-section is calculated, thereby determining the equilibrium propagation coefficient F. If the established numerical simulation model is a two-dimensional model, the equilibrium propagation coefficient is evaluated by comparing the simulated value of the fracture propagation length; if the established numerical simulation model is a three-dimensional model, the equilibrium propagation coefficient F is evaluated by comparing the simulated value of the total fracturing fluid volume entering the soluble perforation sub-section.

[0094] The fracturing construction method is determined based on the established equilibrium expansion coefficient F:

[0095] The equilibrium expansion coefficient F is determined by the following formula:

[0096] or

[0097] In the formula,

[0098] F is the equilibrium expansion coefficient;

[0099] L iThe value of the crack propagation length at the location of the i-th soluble pore section is given in meters (m), where i is a positive integer and i = 1...N; obtained from software numerical simulation results.

[0100] Q i This is the simulated total amount of fracturing fluid entering the i-th soluble perforation sub-section, in m³. 3 This was obtained based on the results of software numerical simulation.

[0101] N represents the number of soluble perforated subsections, which is the number of soluble perforated subsections inserted into the hole in step 3, and is equal to the number of fracturing stages.

[0102] If F≤0.8, it is considered that the fractures in multiple perforation sections can expand evenly, and the entire hole is subjected to one-time fracturing operation.

[0103] The specific steps include:

[0104] Step 6.1: Inject pre-acid solution into the directional long borehole and let the well sit for 24–36 hours; the injection volume of pre-acid solution is V. sy Determined by the following formula:

[0105] V sy =H s ×0.25×π×d tn 2

[0106] In the formula,

[0107] V sy This refers to the injection volume of pre-acid solution, in cubic meters (m³). 3 ;

[0108] H s The length of the horizontal section of a directional long borehole is expressed in meters (m).

[0109] d tn The inner diameter of the casing for directional long boreholes, in meters (m).

[0110] Step 6.2: Inject fracturing fluid from the surface using the designed fracturing operation displacement. The injection volume of fracturing fluid is V. yl Determined by the following formula:

[0111] V yl = N×(200~300)

[0112] In the formula,

[0113] V yl This refers to the injection volume of fracturing fluid, measured in meters (m). 3 ;

[0114] N represents the number of soluble perforated subsections;

[0115] If F > 0.8, it is considered that the fractures in some of the multiple perforation sections cannot be effectively extended, and temporary plugging and segmented fracturing construction should be carried out.

[0116] Specifically, it includes:

[0117] Step 6.1: Inject pre-acid solution into the directional long borehole and let the well sit for 24–36 hours; the injection volume of pre-acid solution is V. sy Determined by the following formula:

[0118] V sy =H s ×0.25×π×d tn 2

[0119] In the formula,

[0120] V sy This refers to the injection volume of pre-acid solution, in cubic meters (m³). 3 ;

[0121] H s The length of the horizontal section of a directional long borehole is expressed in meters (m).

[0122] d tn The inner diameter of the casing for directional long drilling is in meters, and the inner diameter of the casing lowered in step 3 is also mentioned.

[0123] Step 6.2: Using the designed fracturing operation displacement, inject fracturing fluid from the surface to perform the first fracturing operation of the entire borehole. The injection volume of fracturing fluid is 200-300 m³. 3 ;

[0124] Step 6.3: Use existing knot-locking agent delivery equipment to inject knot-locking agent to temporarily seal the opened pressure crack opening;

[0125] Among them, the amount N of knot-stopping agent added at one time s The total number of pores N of a single soluble pore section p The relationship between them satisfies the following equation:

[0126] N s = (1.2~1.5)×N p

[0127] in,

[0128] N s This refers to the number of temporary knot sealants added at one time.

[0129] N p The number of pores on a single soluble pore section;

[0130] Step 6.4: Inject fracturing fluid from the surface to perform a second fracturing operation. The injection volume of fracturing fluid is 200–300 m³.3 ;

[0131] Step 6.5. Repeat steps 6.3 to 6.4 to (N-1) times until the temporary plugging segmented fracturing construction of all fracturing sections is completed.

[0132] Step 7: After the fracturing operation is completed, stop the pump and release the blowout at the opening of the long borehole in the coal mine.

[0133] Step 8: Repeat steps 3 to 7 until the fracturing operation of all directional long boreholes within the layout layer is completed.

[0134] In the above description, unless otherwise explicitly specified and limited, terms such as "setup" and "connection" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to direct connections or indirect connections, etc. Those skilled in the art can understand the specific meaning of the above terms in this technical solution according to the specific circumstances.

[0135] The specific technical features described in the above embodiments can be combined in any suitable manner without contradiction, as long as they do not violate the spirit of the present invention, and should also be regarded as the content disclosed by the present invention.

[0136] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0137] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0138] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for staged fracturing of long boreholes in coal mines to promote uniform fracture propagation, characterized in that, Includes the following steps: Step 1: Collect reservoir parameters of the target mining area, determine the layout of directional long boreholes based on the collected reservoir parameters, and complete the construction parameter design for one or more directional long boreholes within the layout layout. Step 2: Construct one or more directional long boreholes within the determined layout layer; Step 3: Insert a casing string with a soluble perforated section into the directional long borehole, and then cement the hole to solidify it. Step 4: Connect the surface well to the underground roadway of the coal mine. After cementing the surface well with casing, run the tubing into the surface well. Step 5: Lay high-pressure fluid transport pipelines underground in the coal mine. The high-pressure fluid transport pipelines are respectively connected to the oil pipe openings in the surface penetrating well and the four-way connectors at the openings of the directional long boreholes. Step 6: Construct a fracturing numerical simulation model using numerical simulation software. Then, based on the collected reservoir parameters and designed construction parameters, calculate the simulated fracture propagation length at each soluble perforation sub-section or the simulated total fracturing fluid volume at each soluble perforation sub-section, thereby determining the equilibrium propagation coefficient F. Based on the determined equilibrium propagation coefficient F, determine the fracturing construction method: If F≤0.8, it is considered that the fractures in multiple perforation sections can expand evenly, and the entire hole is subjected to one-time fracturing operation. If F > 0.8, it is considered that the fractures in some of the multiple perforation sections cannot be effectively extended, and temporary plugging and segmented fracturing construction should be carried out. Step 7: After the fracturing operation is completed, stop the pump and release the blowout at the opening of the long borehole in the coal mine. Step 8: Repeat steps 3 to 7 until the fracturing operation of all directional long boreholes within the layout layer is completed.

2. The method for segmented fracturing of long boreholes in coal mines to promote uniform fracture propagation as described in claim 1, characterized in that, The soluble perforated section mentioned in step 3 includes a section body (1), on which a plurality of soluble perforations (2) capable of dissolving in acid are equally spaced along the circumference, and the diameter of the soluble perforations (2) is 10-20 mm.

3. The method for segmented fracturing of long boreholes in coal mines to promote uniform fracture propagation as described in claim 1, characterized in that, The soluble perforated section described in step 3 is located at the perforation position, and adjacent soluble perforated sections are connected by a sleeve.

4. The method for segmented fracturing of long boreholes in coal mines to promote uniform fracture propagation as described in claim 1, characterized in that, The numerical simulation software includes Abaqus and Kinetix.

5. The method for segmented fracturing of long boreholes in coal mines to promote uniform fracture propagation as described in claim 1, characterized in that, The reservoir parameters include coal seam rock mechanics parameters, roof rock mechanics parameters, and geostress parameters. The construction parameters include fracturing operation displacement and short-section spacing between adjacent soluble pores.

6. The method for segmented fracturing of long boreholes in coal mines to promote uniform fracture propagation as described in claim 1, characterized in that, The equalization expansion coefficient F mentioned in step 6 is determined by the following formula: or In the formula, F is the equilibrium expansion coefficient; L i Let be the simulated crack propagation length at the location of the i-th soluble pore nodule, in meters, where i is a positive integer and i = 1...N; Q i This is the simulated total amount of fracturing fluid entering the i-th soluble perforation sub-section, in m³. 3 ; N represents the number of soluble perforated subsections.

7. The method for segmented fracturing of long boreholes in coal mines to promote uniform fracture propagation as described in claim 1, characterized in that, Step 6, which describes the implementation of a single-stage fracturing operation for the entire borehole, specifically includes: Step 6.1: Inject pre-acid solution into the directional long borehole and let the well sit for 24–36 hours; the injection volume of pre-acid solution is determined by the following formula: V sy =H s ×0.25×π×d tn 2 In the formula, V sy This refers to the injection volume of pre-acid solution, in cubic meters (m³). 3 ; H s The length of the horizontal section of a directional long borehole is expressed in meters (m). d tn The inner diameter of the casing for directional long boreholes, in meters (m). Step 6.2: Inject fracturing fluid from the surface using the designed fracturing operation displacement. The injection volume of fracturing fluid is determined by the following formula: In yl =N×(200~300) In the formula, V yl This refers to the injection volume of fracturing fluid, measured in meters (m). 3 ; N represents the number of soluble perforated subsections.

8. The method for segmented fracturing of long boreholes in coal mines to promote uniform fracture propagation as described in claim 1, characterized in that, Step 6, which describes the implementation of temporary plugging staged fracturing, specifically includes: Step 6.1: Inject pre-acid solution into the directional long borehole and let the well sit for 24–36 hours; the injection volume of pre-acid solution is determined by the following formula: V sy =H s ×0.25×π×d tn 2 In the formula, V sy This refers to the injection volume of pre-acid solution, in cubic meters (m³). 3 ; H s The length of the horizontal section of a directional long borehole is expressed in meters (m). d tn The inner diameter of the directional long borehole casing is in meters (m). Step 6.2: Inject fracturing fluid from the surface using the designed fracturing displacement to perform the first fracturing operation. The injection volume of fracturing fluid is 200–300 m³. 3 ; Step 6.3: Inject rope knot temporary sealant to temporarily seal the opened pressure crack opening; Among them, the amount N of knot-stopping agent added at one time s The total number of pores N of a single soluble pore section p The relationship between them satisfies the following equation: N s =(1.2~1.5)×N p in, N s This refers to the number of temporary knot sealants added at one time. N p The number of pores on a single soluble pore section; Step 6.4: Inject fracturing fluid from the surface to perform a second fracturing operation. The injection volume of fracturing fluid is 200–300 m³. 3 ; Step 6.5: Repeat steps 6.3 to 6.4 until the temporary plugging and segmented fracturing construction of all fracturing sections is completed.

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