CN-122014252-A - Hard coal weakening method based on cooperation of static fracturing and hydraulic fracturing

CN122014252ACN 122014252 ACN122014252 ACN 122014252ACN-122014252-A

Abstract

The invention relates to the technical field of coal mine safe and efficient exploitation, and discloses a hard coal weakening method based on cooperation of static fracturing and hydraulic fracturing, which comprises the steps of determining a drilling arrangement mode and a quantity ratio; the method comprises the steps of constructing drilling holes according to preset intervals meeting physical penetration requirements, performing track control, loading a constructed packaged static expansion device into a static fracturing drilling hole, sealing, injecting water into a hydraulic fracturing drilling hole to generate water-guiding cracks, monitoring communication characteristics, activating the expansion device by using crack water flow after penetration is confirmed, superposing generated radial expansion stress and a hydraulic fracturing stress field to form a synergistic weakening effect, and measuring coal parameters to evaluate the weakening degree. According to the invention, the hydraulic fracture is communicated and the static fracturing unit is activated, the static stress is used for supporting the fracture to prevent the fracture from closing, and meanwhile, the composite stress is superposed on the tip of the fracture to induce the secondary fracture, so that the problems that a single hydraulic fracture is easy to close and the static fracturing deep part is difficult to crack are solved, and the high-efficiency volume fracture of the hard coal body is realized.

Inventors

LIU XIAOGANG
ZHANG ZHEN
HUANG ZHIZENG
LIU QIANJIN
XUE JISHENG
GAO XIAOJIN
LI ZHENGJIE
LIN XINGYU
MA RONGSHAN

Assignees

天地科技股份有限公司
中煤科工开采研究院有限公司

Dates

Publication Date: 20260512
Application Date: 20260226

Claims (10)

1. The method for weakening the hard coal body based on the cooperation of static fracturing and hydraulic fracturing is characterized by comprising the following steps of: determining an arrangement mode and a quantity ratio of static fracturing drilling holes and hydraulic fracturing drilling holes based on target coal seam geological conditions; Constructing the static fracturing drilling holes and the hydraulic fracturing drilling holes in a hard coal body according to the arrangement mode and the quantity ratio and the design space meeting the physical through requirement, and performing track control; Determining the size of a packaged static expansion device, constructing the packaged static expansion device, filling the constructed packaged static expansion device into the constructed static fracturing drilling hole, and sealing by using a hole sealing device; Injecting high-pressure water into the hydraulic fracturing drilling hole to generate a water guide crack, and monitoring communication response characteristics in the water injection process; When the communication response characteristics confirm to be communicated, activating the packaging type static expansion device by utilizing water flow in the water guide crack, so that radial expansion stress generated by the packaging type static expansion device and a hydraulic fracturing stress field are overlapped to form a synergistic weakening effect, and calculating the intensity of effectively overlapped cracking stress to represent the synergistic weakening effect; And measuring the coal body parameters after the synergistic weakening effect is acted, and evaluating the weakening degree of the hard coal body.
2. The method for weakening a hard coal body based on cooperation of static fracturing and hydraulic fracturing according to claim 1, wherein the step of determining the arrangement pattern of static fracturing drilling holes and hydraulic fracturing drilling holes comprises the following steps: setting the space positions of the static fracturing drilling holes and the hydraulic fracturing drilling holes to be a parallel staggered arrangement mode or a vertical transverse arrangement mode of the cutting holes; Setting the bedding parallel staggered arrangement mode, so that the axial direction of the drilling holes is parallel to the advancing direction of the working surface, and periodic staggered arrangement is shown on a section perpendicular to the trend; and setting the vertical transverse arrangement mode of the cutting holes, so that the axial direction of the drilling holes is perpendicular to the advancing direction of the working surface, and restraining the effective depth of the drilling holes based on the actually measured width of the cutting holes of the working surface.
3. The method for weakening a hard coal body based on cooperation of static fracturing and hydraulic fracturing according to claim 1, wherein the step of calculating the design distance comprises the steps of: acquiring engineering safety coefficients, heterogeneous geological correction coefficients of a coal seam, effective wetting radius of single-hole hydraulic fracturing and an included angle between the maximum horizontal main stress direction and the normal line of the central connecting line of two holes, and defining the acquired parameters as a distance calculation parameter set; constructing a fluid conduction constraint inequality meeting fluid conduction requirements based on the distance calculation parameter set; And calculating and defining the distance between the static fracturing drilling central axis and the adjacent hydraulic fracturing drilling central axis by using the fluid conduction constraint inequality, and confirming the calculated distance as the design distance.
4. The method of weakening a hard coal body based on the synergy of static fracturing and hydraulic fracturing according to claim 1, wherein the step of determining the quantitative ratio of static fracturing drillings and hydraulic fracturing drillings comprises: Acquiring an actual measurement value of the Brinell hardness coefficient of a target coal seam, a standard hardness threshold value without special enhanced fracturing and a hardness grading level difference, and defining the acquired parameters as a density index calculation parameter set; Substituting the density index calculation parameter set into a weakening unit density index calculation logic to perform operation; And calculating a logically output weakening unit density index according to the weakening unit density index, and determining the quantity ratio of the static fracturing drilling holes to the hydraulic fracturing drilling holes in unit volume.
5. A method of weakening a hard coal body based on the synergy of static fracturing and hydraulic fracturing according to claim 1, wherein the step of performing trajectory control comprises: Constructing by adopting a directional drilling machine provided with a measurement while drilling system, and calculating the real-time actual distance between the static fracturing drilling hole and the hydraulic fracturing drilling hole in real time; comparing the real-time actual distance with the boundary value allowed by the design distance; And when the comparison result shows that the real-time actual distance approaches to the boundary value, starting a directional deflecting and correcting program to prevent a rock bridge effect, thereby completing the track control.
6. The method of weakening a hard coal body based on the cooperation of static fracturing and hydraulic fracturing according to claim 1, wherein the step of constructing the encapsulated static expansion device comprises: Assembling by adopting an internal high-energy static crushing flux core and an external directional permeable constraint layer; determining a particle retention criterion based on the effective particle size and the safety screening coefficient of the high-energy static broken drug core powder particles; Screening the material of the directional permeable constraint layer to ensure that the average micropore diameter of the directional permeable constraint layer meets the particle retention criterion, so that external moisture permeates and internal powder is blocked from flowing out, thereby completing the construction of the packaged static expansion device.
7. A method for weakening a hard coal body based on the cooperation of static fracturing and hydraulic fracturing according to claim 1, wherein the step of sizing the encapsulated static expansion device comprises: Measuring the construction inner diameter of the static fracturing drill hole; Substituting the construction inner diameter into a radial filling matching coefficient calculation formula for calculation; and determining the outer diameter of the cylinder of the packaged static expansion device according to the calculation result of the radial filling matching coefficient calculation formula, and realizing the geometric matching of the packaged static expansion device and the static fracturing drilling.
8. A method of weakening a hard coal body based on the synergy of static fracturing and hydraulic fracturing according to claim 1, wherein said step of calculating an effective superimposed fracture stress intensity characterizes said synergistic weakening effect comprises: Acquiring a hydraulic coupling coefficient, residual pore water pressure, a stress transfer efficiency factor, a maximum radial expansion pressure, a reagent reaction rate constant and reaction time, and defining the acquired parameters as a fracture tip potential energy influence factor set; Constructing an effective superposition cracking stress intensity calculation formula based on the crack tip potential energy influence factor set; And calculating the effective superimposed fracture stress intensity by adopting the effective superimposed fracture stress intensity calculation formula, and quantitatively representing the damage potential energy of the fracture tip in the synergistic weakening effect.
9. A method of weakening a hard coal body based on the synergy of static fracturing and hydraulic fracturing according to claim 1, wherein the step of monitoring the communication response characteristics during water injection comprises: recording the change data of water injection pressure along with time in the water injection process; Analyzing the change data of the water injection pressure along with time, identifying whether the characteristic that the instantaneous pressure drop exceeds a set pressure threshold value and the water injection flow synchronously increases along with the change data of the water injection pressure along with time exists, and defining the identified characteristic as a communication response characteristic; when the communication response characteristic is identified, judging that the hydraulic fracture penetrates through the static fracturing drilling hole in physical space; the set pressure threshold is 3 megapascals or the set pressure threshold is 10% of the current system pressure.
10. A method of weakening a hard coal body based on the synergy of static fracturing and hydraulic fracturing according to claim 1, wherein said step of assessing the degree of weakening of said hard coal body comprises: constructing check drilling holes at the center and the edge of a fracturing area, acquiring the Prussian hardness coefficient of an original coal body, the residual Prussian hardness coefficient after the cooperative weakening treatment, the standard drilling cuttings amount of the unit drilling length of the original coal body and the average drilling cuttings amount of the unit drilling length after the cooperative weakening treatment, and defining the acquired parameters as a cooperative weakening efficiency evaluation parameter set; constructing a collaborative weakening efficacy index calculation model by utilizing the collaborative weakening efficacy evaluation parameter set; And calculating the cooperative weakening efficiency index by adopting the cooperative weakening efficiency index calculation model, and evaluating the weakening degree of the hard coal body based on the cooperative weakening efficiency index.

Description

Hard coal weakening method based on cooperation of static fracturing and hydraulic fracturing Technical Field The invention relates to the technical field of coal mine safe and efficient mining, in particular to a hard coal weakening method based on cooperation of static fracturing and hydraulic fracturing. Background The hard coal seam is widely distributed in China, and particularly in areas under the action of structural extrusion or thermal deformation of magma, the coal and rock strength is high and the integrity is strong. In fully mechanized mining operation, the cutting resistance of the coal mining machine is greatly increased due to the existence of the hard coal body, so that the cutting pick, the roller and the transmission system are worn severely, equipment faults frequently occur, and the stoping efficiency is restricted. In addition, the hard coal seam is often accompanied by a hard top plate, particularly during the initial mining of a working face, since mining stress is not fully developed and the top plate is not easy to naturally collapse, a large-area suspended roof is easy to form, and once suddenly collapses, strong mine pressure development is induced, thus threatening the safety of underground personnel and equipment. Currently, in order to reduce the exploitation difficulty of a hard coal seam, deep hole blasting, hydraulic fracturing or static fracturing and other technologies are generally adopted in engineering practice to weaken the coal body in advance. The deep hole blasting technology has strong breaking capacity, but is accompanied by shock waves, vibration and toxic gas in the construction process, so that the stability disturbance to surrounding rock is large, and high safety risk exists. The hydraulic fracturing technology utilizes high-pressure fluid to manufacture cracks in a coal seam, the safety is relatively good, but the generated crack forms are controlled by a ground stress field to be relatively strong, a crack network is often single, after water injection is stopped, the cracks are easily closed again under the compaction effect of deep high ground stress, and the weakening effect is attenuated along with time. The static fracturing technology utilizes expansion pressure generated by hydration reaction of an expanding agent to crush coal and rock, has the advantages of no vibration and no flying stone, but the effective implementation of the technology depends on the free surface of the boundary of a rock body, and the stress generated by the expanding agent is difficult to induce initial crack expansion in the deep-hole fracturing scene because the deep-hole fracturing technology is in a three-way stress state and lacks free surface to provide expansion space in the deep-hole complete coal body, so that the cracking is difficult and the crushing effect is poor. Therefore, the existing single weakening technology is difficult to simultaneously realize effective cracking and long-term maintenance of cracks of the coal body under a deep high-stress environment. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a hard coal weakening method based on the synergy of static fracturing and hydraulic fracturing, which solves the problems of single fracture form, easy closure under the action of ground stress, limited single static fracturing action range, difficult deep cracking, insufficient coal crushing and large subsequent mechanical cutting resistance generated by single hydraulic fracturing in the prior art. In order to achieve the above purpose, the invention is realized by the following technical scheme: A weakening method of a hard coal body based on synergy of static fracturing and hydraulic fracturing comprises the following steps of determining arrangement modes and quantity ratios of static fracturing drilling holes and hydraulic fracturing drilling holes based on geological conditions of a target coal seam, constructing the static fracturing drilling holes and the hydraulic fracturing drilling holes in the hard coal body according to the determined arrangement modes and quantity ratios and a preset distance meeting physical penetration requirements, performing track control, determining the size of a packaged static expansion device, constructing the device, filling the constructed packaged static expansion device into the constructed static fracturing drilling holes, sealing by using a hole sealing device, injecting high-pressure water into the hydraulic fracturing drilling holes to generate water guide cracks, monitoring communication response characteristics in a water injection process, activating the packaged static expansion device by using water flow in the water guide cracks after the communication response characteristics are confirmed to penetrate, enabling the packaged static expansion device to generate radial expansion stress, superposing the radial expansion stress and a hydraulic fracturing stress field