Method for detecting multidimensional hydraulic fracturing effect of long and short holes in coal seam working face

Abstract

The invention relates to the technical field of coal mining, in particular to a coal seam working face long and short hole multi-dimensional hydraulic fracturing effect detection method which comprises the following steps: drilling holes in a fracturing area in two gate road directions of a working face, observing a roof rock mass structure and fracturing section hole wall crack conditions by adopting drilling peeping equipment, and comparing crack differences before and after fracturing; monitoring water pressure and flow parameters in the fracturing process in real time by adopting a monitoring instrument, and drawing a pressure-flow curve; respectively recording the water outlet states and parameters of the hole and the adjacent hole in the fracturing process; and performing multi-dimensional monitoring, including crack propagation monitoring, ground pressure monitoring, water permeability monitoring, roof stability monitoring, coal deformation monitoring and environment monitoring. The monitoring dimensionality is comprehensive, six core dimensionalities including crack propagation, ground pressure, water permeability, roof stability, coal deformation and environmental influence are involved, the fracturing effect can be accurately reflected, powerful support is provided for fracturing scheme optimization, supporting scheme adjustment and safe operation, and the scientific theory is evaluated.

Description

Technical Field

[0001] This invention relates to the field of coal mining technology, and in particular to a method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in coal seam working faces. Background Technology

[0002] The coal seam working face is an important area in coal mining, serving as the specific site for underground coal mining operations. Hydraulic fracturing of the coal seam working face roof is a mining technique that uses high-pressure hydraulic pressure to fracture the coal or rock strata, thereby improving roof stability and permeability. Monitoring the effectiveness of hydraulic fracturing operations after the operation is crucial, as the results allow for real-time implementation of follow-up plans or secondary operations to address any issues identified during the fracturing process.

[0003] Existing methods for detecting the effectiveness of hydraulic fracturing suffer from problems such as limited monitoring dimensions, insufficient data support, and incomplete evaluation. They are unable to accurately reflect various aspects such as fracture propagation, formation stress changes, permeability improvement, and roof and coal body stability. They cannot systematically and comprehensively verify the operational effectiveness, nor can they provide effective feedback on the effects of hydraulic fracturing. Consequently, they cannot provide sufficient scientific basis for subsequent operation optimization and safety assurance, which is detrimental to subsequent construction plans and secondary operation plans. Summary of the Invention

[0004] This invention provides a multi-dimensional hydraulic fracturing effect detection method with long and short holes in coal seam working faces, addressing one of the shortcomings of existing technologies. This invention offers comprehensive monitoring dimensions, covering six core dimensions: fracture propagation, ground pressure, permeability, roof stability, coal body deformation, and environmental impact, avoiding evaluation biases caused by single-dimensional monitoring. Each monitoring step and equipment operation is adapted to the special working environment underground, with a clear process, strong operability and practicality, facilitating on-site implementation. Based on comprehensive analysis of multi-source monitoring data, it accurately reflects the fracturing effect, providing strong support for fracturing scheme optimization, support scheme adjustment, and safe operation, resulting in a scientific and reasonable evaluation.

[0005] This invention provides a method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in a coal seam working face, comprising: S100, boreholes are drilled in the fracturing area along the two grooves of the working face. The borehole inspection equipment is used to observe the structure of the roof rock mass and the fracture condition of the borehole wall in the fracturing section, and to compare the fracture differences before and after fracturing. The S200 uses monitoring instruments to monitor water pressure and flow parameters in real time during the fracturing process and plots pressure-flow curves. S300, record the water outflow status and parameters of this hole and adjacent holes respectively during the fracturing process; S400 is subject to multi-dimensional monitoring, including crack propagation monitoring, ground pressure monitoring, permeability monitoring, roof stability monitoring, coal body deformation monitoring, and environmental monitoring.

[0006] According to the present invention, a method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in a coal seam working face is provided, wherein step S100 includes: The probe is inserted into the borehole via a connecting rod. The probe is decelerated at fissures and special structures to observe and record the surrounding rock structure. After the observation is completed, the observation results are recorded, processed, and analyzed.

[0007] According to the present invention, a method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in a coal seam working face is provided, wherein step S200 includes: Under the pressure holding state, the pressure rises from 0 to the initial pressure and then drops to the pressure holding state. The pressure fluctuates up and down in a sawtooth pattern as the fracture develops. When a large fracture channel appears, the pressure drops sharply and the flow rate increases. Based on the characteristics of the pressure-flow curve, the timing of crack initiation, the stage of crack propagation, and the state of crack channel formation in the roof rock mass can be determined.

[0008] According to the present invention, a method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in a coal seam working face is provided. In step S300, recording the water outflow state and parameters of the hole includes: When a large amount of water is observed gushing out of the wellhead, and the water pressure decreases and the flow rate increases simultaneously, it is determined that the wellhead sealer is damaged. The rod is immediately withdrawn and the wellhead sealer is replaced. The location of the fracturing section and the water outflow are recorded. After replacing the wellhead sealer, the rod is fed back for fracturing to ensure that there is no backflow in the well during each fracturing section.

[0009] According to the present invention, a method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in a coal seam working face is provided. In step S300, recording the water discharge status and parameters of the adjacent holes includes: When the water pressure in the fracturing section decreases and the flow rate increases, and the water output of the adjacent well reaches the preset threshold, it is determined that the hydraulic fracture has started and connected with the adjacent well. The fracturing time and water output parameters of the adjacent well are recorded. The fracturing of this section is stopped and the fracturing is moved to other fracturing sections to ensure that the fracturing points of the adjacent wells are staggered.

[0010] According to the present invention, a method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in a coal seam working face is provided. The fracture propagation monitoring includes microseismic monitoring and water pressure monitoring. The microseismic monitoring is carried out by installing an SOS microseismic monitoring system in the fracturing area and comparing the microseismic signals in the fracturing-enhanced area with those in the unfracturing-enhanced area to determine the development range of the fracturing fracture. The water pressure monitoring is carried out by statistically analyzing real-time pressure data of the fracturing section, plotting water pressure curves, and inverting the fracture propagation situation based on the cyclic law of pressure drop-recovery-reopening.

[0011] According to the present invention, a method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in a coal seam working face is provided, wherein the ground pressure monitoring includes coal body stress monitoring and roadway roof pressure monitoring; The coal stress monitoring includes: Each station is equipped with multiple borehole stress gauges. Each borehole stress gauge is installed with a set depth difference, the borehole diameter is a set diameter, the borehole is 1.2~1.5m away from the roadway floor and is installed horizontally, and the installation position is on the side of the main roadway close to the mining face. The roadway roof pressure monitoring includes: An anchor rod or anchor cable force gauge is used, and the stress state at the end of the anchor rod or anchor cable is calculated by measuring the deformation change of the strain gauge based on the principle of resistance strain gauge.

[0012] According to the present invention, a method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in a coal seam working face is provided. The permeability monitoring adopts the coal seam permeability comparison method. By observing and comparing the permeability data of the fracturing area and the unfracturing area, the degree of permeability improvement is determined.

[0013] According to the present invention, a method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in a coal seam working face is provided, wherein the coal deformation monitoring includes: Two holes with a diameter of 30mm and a depth of 400mm were drilled vertically in the middle of the top and bottom slabs and horizontally in the two sides. Wooden piles were driven into the holes. Curved measuring nails were installed at the ends of the wooden piles in the top slab and upper side slab, and flat-headed measuring nails were installed at the ends of the wooden piles in the bottom slab and lower side slab. The two monitoring sections were spaced 0.6 to 1.0m apart along the axial direction of the roadway to monitor the deformation process of the surrounding rock of the roadway as the working face advances after hydraulic fracturing.

[0014] According to the present invention, a method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in a coal seam working face is provided, wherein the environmental monitoring includes: Groundwater and surface water samples were taken from the fracturing area and sent to the laboratory for chemical analysis to determine whether the water quality met environmental protection requirements.

[0015] The multi-dimensional hydraulic fracturing effect detection method for long and short boreholes in coal seam working faces provided by this invention can provide valuable detection data support for subsequent effect analysis and evaluation. It mainly consists of steps including borehole inspection, fracturing data monitoring, water production recording, and multi-dimensional monitoring.

[0016] Drilling inspection involves drilling observation holes in both roadways towards the fracturing area of ​​the working face. A small-diameter panoramic electronic sight is used to observe the stratigraphic occurrence, structural characteristics, and fracture distribution of the borehole walls in the fracturing section of the roof rock mass. Observational data before and after fracturing are recorded, and fracture changes are compared and analyzed. Fracturing data monitoring involves installing a pressure gauge and flow meter on the fracturing equipment to collect real-time water pressure and flow data during the fracturing process. Data is recorded every 10 seconds, and pressure-flow curves are plotted based on the collected data. Water production status recording involves assigning personnel to observe the water production status of the borehole and adjacent boreholes in real time during fracturing, recording parameters such as water production time, water volume, water pressure, and flow rate changes. Multi-dimensional monitoring mainly consists of crack propagation monitoring, ground pressure monitoring, permeability monitoring, roof stability monitoring, coal deformation monitoring, and environmental monitoring. Crack propagation detection uses the SOS microseismic monitoring system to collect microseismic signals and simultaneously records water pressure data to plot water pressure curves. Ground pressure monitoring uses borehole stress gauges to monitor coal stress and anchor bolt (cable) force gauges to monitor roadway roof pressure. Permeability monitoring observes and records the coal seam permeability in the fracturing and unfracturing areas. Roof stability monitoring uses a roof delamination indicator to monitor roof delamination values. Coal deformation monitoring uses a cross-point method to monitor roadway surface displacement. Environmental monitoring involves sampling and analyzing water in the fracturing area. Finally, by integrating all the above monitoring data, the extent of crack development, formation stress distribution, degree of permeability improvement, roof and coal stability status, and environmental impact after fracturing can be analyzed to determine whether the fracturing effect meets design requirements, generate an evaluation report, and provide a basis for subsequent operational adjustments.

[0017] This invention provides comprehensive monitoring dimensions, covering six core dimensions: fracture propagation, ground pressure, permeability, roof stability, coal body deformation, and environmental impact, avoiding evaluation biases caused by monitoring only one dimension. It employs specialized equipment such as small-diameter panoramic electronic sights, hydraulic gauges, flow meters, and borehole stress gauges to ensure high accuracy and authenticity of monitoring data. Each monitoring step and equipment operation is adapted to the special working environment underground, with a clear process, strong operability and practicality, facilitating on-site implementation. Based on comprehensive analysis of multi-source monitoring data, it accurately reflects the fracturing effect, providing strong support for fracturing scheme optimization, support scheme adjustment, and safe operation, resulting in a scientific and reasonable evaluation. Environmental monitoring ensures that fracturing operations comply with environmental standards, while monitoring roof stability and ground pressure prevents safety accidents, balancing environmental protection and safety. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a flowchart illustrating the method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in coal seam working faces, as provided in an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0021] In the description of the embodiments of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0022] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0023] In embodiments of the present invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0024] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0025] like Figure 1 As shown, this embodiment of the invention provides a method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in a coal seam working face, including: S100, boreholes are drilled in the fracturing area along the two grooves of the working face. The borehole inspection equipment is used to observe the structure of the roof rock mass and the fracture condition of the borehole wall in the fracturing section, and to compare the fracture differences before and after fracturing. The S200 uses monitoring instruments to monitor water pressure and flow parameters in real time during the fracturing process and plots pressure-flow curves. S300, record the water outflow status and parameters of this hole and adjacent holes respectively during the fracturing process; S400 is subject to multi-dimensional monitoring, including crack propagation monitoring, ground pressure monitoring, permeability monitoring, roof stability monitoring, coal body deformation monitoring, and environmental monitoring.

[0026] The multi-dimensional hydraulic fracturing effect detection method for long and short boreholes in coal seam working faces, as described in this invention, can provide valuable data support for subsequent effect analysis and evaluation. It mainly consists of steps including borehole inspection, fracturing data monitoring, water production recording, and multi-dimensional monitoring.

[0027] Drilling inspection involves drilling observation holes in both roadways towards the fracturing area of ​​the working face. A small-diameter panoramic electronic sight is used to observe the stratigraphic occurrence, structural characteristics, and fracture distribution of the borehole walls in the fracturing section of the roof rock mass. Observational data before and after fracturing are recorded, and fracture changes are compared and analyzed. Fracturing data monitoring involves installing a pressure gauge and flow meter on the fracturing equipment to collect real-time water pressure and flow data during the fracturing process. Data is recorded every 10 seconds, and pressure-flow curves are plotted based on the collected data. Water production status recording involves assigning personnel to observe the water production status of the borehole and adjacent boreholes in real time during fracturing, recording parameters such as water production time, water volume, water pressure, and flow rate changes. Multi-dimensional monitoring mainly consists of crack propagation monitoring, ground pressure monitoring, permeability monitoring, roof stability monitoring, coal deformation monitoring, and environmental monitoring. Crack propagation detection uses the SOS microseismic monitoring system to collect microseismic signals and simultaneously records water pressure data to plot water pressure curves. Ground pressure monitoring uses borehole stress gauges to monitor coal stress and anchor bolt (cable) force gauges to monitor roadway roof pressure. Permeability monitoring observes and records the coal seam permeability in the fracturing and unfracturing areas. Roof stability monitoring uses a roof delamination indicator to monitor roof delamination values. Coal deformation monitoring uses a cross-point method to monitor roadway surface displacement. Environmental monitoring involves sampling and analyzing water in the fracturing area. Finally, by integrating all the above monitoring data, the extent of crack development, formation stress distribution, degree of permeability improvement, roof and coal stability status, and environmental impact after fracturing can be analyzed to determine whether the fracturing effect meets design requirements, generate an evaluation report, and provide a basis for subsequent operational adjustments.

[0028] This invention provides comprehensive monitoring dimensions, covering six core dimensions: fracture propagation, ground pressure, permeability, roof stability, coal body deformation, and environmental impact, avoiding evaluation biases caused by monitoring only one dimension. It employs specialized equipment such as small-diameter panoramic electronic sights, hydraulic gauges, flow meters, and borehole stress gauges to ensure high accuracy and authenticity of monitoring data. Each monitoring step and equipment operation is adapted to the special working environment underground, with a clear process, strong operability and practicality, facilitating on-site implementation. Based on comprehensive analysis of multi-source monitoring data, it accurately reflects the fracturing effect, providing strong support for fracturing scheme optimization, support scheme adjustment, and safe operation, resulting in a scientific and reasonable evaluation. Environmental monitoring ensures that fracturing operations comply with environmental standards, while monitoring roof stability and ground pressure prevents safety accidents, balancing environmental protection and safety.

[0029] According to an embodiment of the present invention, step S100 includes: The probe is inserted into the borehole via a connecting rod. The probe is decelerated at fissures and special structures to observe and record the surrounding rock structure. After the observation is completed, the observation results are recorded, processed, and analyzed.

[0030] In this embodiment, a small-diameter panoramic electronic sighting instrument for drilling is used for borehole inspection. The small-diameter panoramic electronic sighting instrument consists of a connecting rod, a main unit, a probe, a depth counter, and wires.

[0031] The connecting rod is made of specially treated aluminum, which is lightweight yet rigid, enabling it to withstand the humid and dusty environment of downhole wells and preventing rust and corrosion. The main unit, serving as the control unit, contains high-precision acquisition, stitching, storage, and display modules. It boasts strong shock resistance, an IP65 sealing rating for effective dust and moisture protection, and weighs only 2.6kg, making it easy to carry and operate downhole. The probe housing is made of stainless steel, and the probe cover uses tempered optical glass. The internal camera is a color low-light 450-line, 0.1Lux, 1.34 million-pixel camera with a crack resolution of up to 0.1mm, clearly capturing even tiny cracks. The probe also features a built-in high-precision electronic compass with an angular resolution of 0.1°, accurately recording the observation angle. The depth counter uses a high-precision photoelectric encoder, achieving a depth measurement accuracy of 0.1mm, ensuring accurate observation position. The guide wire uses a special armored cable for oil well logging, which is robust, durable, and resistant to damage.

[0032] The borehole inspection operation procedure is as follows: After drilling observation holes in the underground roadway, the probe of the borehole inspection instrument is slowly inserted into the borehole through the connecting rod. It is advanced at a constant speed in the normal borehole section. When encountering fractures or special rock structures, the advancing speed is reduced, and the surrounding rock structure of the borehole section is carefully observed and recorded. If necessary, images are taken. After the observation is completed, the probe is slowly retracted, and the inspection results are classified and recorded in a special table. Through the splicing and analysis functions of the host, a panoramic image of the borehole wall is generated. The number, length, width and distribution density of fractures before and after fracturing are compared to intuitively judge the fracturing effect.

[0033] According to an embodiment of the present invention, step S200 includes: Under the pressure holding state, the pressure rises from 0 to the initial pressure and then drops to the pressure holding state. The pressure fluctuates up and down in a sawtooth pattern as the fracture develops. When a large fracture channel appears, the pressure drops sharply and the flow rate increases. Based on the characteristics of the pressure-flow curve, the timing of crack initiation, the stage of crack propagation, and the state of crack channel formation in the roof rock mass can be determined.

[0034] In this embodiment, a calibrated hydraulic gauge and flow meter are used as monitoring instruments, which are installed at the outlet pipe and fracturing orifice of the fracturing pump group, respectively, to ensure that the connection between the instrument and the pipe is well sealed and to avoid water leakage affecting the monitoring accuracy.

[0035] During fracturing, a hydraulic pressure gauge and a flow meter collect pressure and flow data of the fracturing section in real time. The data collection frequency is once every 5 seconds. The real-time data is transmitted to the ground monitoring terminal through the data transmission module, and the terminal software automatically plots the pressure-flow curve.

[0036] The curve analysis process is as follows: In the initial stage of fracturing, the pressure gradually increases from 0 under the holding pressure state. When the pressure reaches the initiation pressure of the roof rock mass, fractures begin to form in the rock mass. At this time, the pressure will decrease slightly and enter the holding pressure state. As fracturing continues, the fractures expand continuously, and the pressure fluctuates up and down in a sawtooth pattern, indicating that the rock mass fractures are continuously developing in a cycle of "fracturing-expansion-re-fracturing". When the pressure curve suddenly drops and a significant increase in flow rate is simultaneously detected, it is determined that a large fracture channel has formed in the rock mass. At this time, a large amount of fracturing fluid seeps into the fracture, making it impossible to maintain the holding pressure state. Through the above curve characteristics, the timing of fracturing initiation, the stage of fracture expansion, and the state of fracture channel formation in the roof rock mass can be accurately determined, providing data support for the evaluation of fracturing effectiveness.

[0037] According to an embodiment of the present invention, in step S300, recording the water outlet status and parameters of this hole includes: When a large amount of water is observed gushing out of the wellhead, and the water pressure decreases and the flow rate increases simultaneously, it is determined that the wellhead sealer is damaged. The rod is immediately withdrawn and the wellhead sealer is replaced. The location of the fracturing section and the water outflow are recorded. After replacing the wellhead sealer, the rod is fed back for fracturing to ensure that there is no backflow in the well during each fracturing section.

[0038] During fracturing, a designated person should conduct real-time observation at the wellhead, equipped with auxiliary tools such as measuring cylinders and pressure gauges. When a large amount of water is observed gushing out of the wellhead, and the pressure gauge shows a rapid drop in water pressure while the flow meter shows a significant increase in flow rate, it should be immediately determined that the wellhead sealer has ruptured. In this case, the fracturing pump should be stopped immediately, and the specific location of the current fracturing section, the time when water begins to emerge, and the water pressure and flow rate data at the time of water emergence should be recorded.

[0039] The fracturing rod is then withdrawn from the borehole slowly. The damaged sealer is removed and replaced with a new sealer of the same model, ensuring proper installation and a good seal. After replacement, the fracturing rod is reinserted into the designated fracturing section, and the fracturing pump is started to continue fracturing operations. Throughout the process, the borehole is monitored for any recurrence of water flow to ensure no backflow occurs during each fracturing stage and to guarantee the fracturing effect.

[0040] According to an embodiment of the present invention, in step S300, recording the water outlet status and parameters of adjacent wells includes: When the water pressure in the fracturing section decreases and the flow rate increases, and the water output of the adjacent well reaches the preset threshold, it is determined that the hydraulic fracture has started and connected with the adjacent well. The fracturing time and water output parameters of the adjacent well are recorded. The fracturing of this section is stopped and the fracturing is moved to other fracturing sections to ensure that the fracturing points of the adjacent wells are staggered.

[0041] In this embodiment, the specific locations of adjacent boreholes are predetermined, with the horizontal distance between the adjacent boreholes and the fracturing boreholes not exceeding 5 meters. A simple water flow metering device and a pressure monitoring gauge are installed at the borehole openings of the adjacent boreholes. During fracturing, the water flow status, flow rate, and water pressure and flow rate data of the fracturing section are monitored in real time from the adjacent boreholes.

[0042] When a significant drop in water pressure is detected in the fracturing section, accompanied by a synchronous increase in flow rate, and the outflow from adjacent wells reaches 5 L / min (a preset threshold), it is determined that the hydraulic fracture has initiated and fully extended, achieving connection with adjacent wells. At this point, key parameters such as the current fracturing time, outflow from adjacent wells, water pressure and flow rate in the fracturing section are immediately recorded. Fracturing operations in this section are stopped, and the fracturing rod is moved back to the unfracturing area. A new fracturing section is selected at least 1.5 m away from the fracturing point of the adjacent well, and fracturing is restarted to avoid excessive overlap of fractures, which would affect the fracturing effect.

[0043] According to one embodiment of the present invention, fracture propagation monitoring includes microseismic monitoring and hydraulic pressure monitoring. Microseismic monitoring involves installing an SOS microseismic monitoring system in the fracturing area and comparing the microseismic signals in the fracturing-enhanced area with those in the unfracturing-enhanced area to determine the range of fracture development. Hydraulic pressure monitoring involves statistically analyzing real-time pressure data of the fracturing section, plotting hydraulic pressure curves, and inverting the fracture propagation based on the cyclical pattern of pressure drop-recovery-reopening.

[0044] In this embodiment, crack propagation monitoring employs a combination of microseismic monitoring and water pressure monitoring: Microseismic monitoring involves installing three SOS microseismic sensors on the tunnel walls surrounding the fracturing area. The sensors are installed at a depth of 1.0m and securely fixed to ensure stable signal acquisition. During fracturing, the sensors collect microseismic signals in real time from both the fracturing and unfracturing areas. These signals are transmitted to a ground analysis terminal via data transmission cables. The terminal software analyzes parameters such as amplitude, frequency, and duration of the microseismic signals, comparing the differences between the two areas to determine the development range and propagation direction of the fracturing fractures.

[0045] Water pressure monitoring involves using a high-precision water pressure gauge installed on the fracturing pipeline to collect pressure data of the fracturing section in real time, with a data acquisition frequency of once every 2 seconds. Water pressure curves are then plotted based on the collected data. The characteristics of the water pressure curves are analyzed to assess fracture propagation: at the moment the first fracture opens, water rapidly seeps into the fracture, causing a significant drop in water pressure; subsequently, the fracture is filled with fracturing water, and the pressure gradually recovers; once the pressure reaches a certain value, new fractures are gradually opened, forming multiple cycles of pressurization and pressure release under sufficient flow and pump pressure. This cyclical pattern is used to inversely determine the fracture propagation progress and development level.

[0046] According to the present invention, a method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in a coal seam working face is provided, wherein the ground pressure monitoring includes coal body stress monitoring and roadway roof pressure monitoring; Coal stress monitoring includes: Each station is equipped with multiple borehole stress gauges. Each borehole stress gauge is installed with a set depth difference. The borehole diameter is the set diameter. The borehole is 1.2~1.5m away from the roadway floor and is installed horizontally. The installation position is on the side of the main roadway close to the mining face. Roadway roof pressure monitoring includes: An anchor rod or anchor cable force gauge is used, and the stress state at the end of the anchor rod or anchor cable is calculated by measuring the deformation change of the strain gauge based on the principle of resistance strain gauge.

[0047] In this embodiment, ground pressure monitoring includes coal seam stress monitoring and roadway roof pressure monitoring: Coal stress monitoring was conducted using borehole stress gauges. The purpose of the monitoring was to analyze the distribution of lateral support pressure on the coal pillar from the goaf and the pressure relief mechanism of hydraulic fracturing on the support pressure. Three borehole stress gauges were installed at each monitoring station. The borehole diameter was 42 mm, and the boreholes were positioned 1.2–1.5 m from the roadway floor. Horizontal installation was adopted, with the gauges installed at depths of 5 m, 10 m, and 15 m in the main roadway near the working face. This ensured coverage of coal stress distribution at different depths. After installation, monitoring data from the stress gauges were collected periodically to analyze the changes in coal stress during the fracturing process.

[0048] Roof pressure monitoring in roadways is conducted using anchor bolt or cable force gauges, which operate based on the principle of resistance strain gauges. The force gauges are installed at the ends of the anchor bolts or cables. When roof pressure acts on the anchor bolts or cables, the force gauges experience compressive stress, causing deformation of the internal strain gauges. The deformation change of the strain gauges is measured using an analyzer, and combined with preset calibration coefficients, the stress state at the ends of the anchor bolts or cables is calculated. This allows for real-time monitoring of roof pressure changes, providing a basis for adjusting support schemes.

[0049] According to one embodiment of the present invention, the permeability monitoring adopts the coal seam permeability comparison method. By observing and comparing the coal seam permeability data of the fracturing area and the unfracturing area, the degree of permeability improvement is determined.

[0050] In this embodiment, permeability monitoring adopts the coal seam permeability comparison method, and the specific operation is as follows: Three representative observation points within the fracturing area and three corresponding observation points within the unfracturing area were selected. The geological conditions, coal seam thickness, and other basic parameters of the observation points were kept consistent to ensure the effectiveness of the comparison. Permeability observation holes were drilled at each observation point. The diameter of the holes was 50 mm and the depth was 8 m. The holes were perpendicular to the coal seam bedding plane. The permeability of coal seams was measured using a steady-state method. Clean water was injected into the observation well using a high-pressure grouting device, and the injection pressure was controlled to be stable at 0.5 MPa. The amount of water injected per unit time was recorded, and the permeability value of the coal seam was calculated based on Darcy's law. The permeability values ​​at each observation point before and after fracturing were measured, and the changes in permeability between the fracturing and unfracturing areas were compared to determine the degree to which hydraulic fracturing improved the permeability of the coal seam. If the permeability of the fracturing area increased by more than 30% compared to the unfracturing area, the improvement in permeability was considered to have achieved the expected effect.

[0051] According to one embodiment of the present invention, coal deformation monitoring includes: Two holes with a diameter of 30mm and a depth of 400mm were drilled vertically in the middle of the top and bottom slabs and horizontally in the two sides. Wooden piles were driven into the holes. Curved measuring nails were installed at the ends of the wooden piles in the top slab and upper side slab, and flat-headed measuring nails were installed at the ends of the wooden piles in the bottom slab and lower side slab. The two monitoring sections were spaced 0.6 to 1.0m apart along the axial direction of the roadway to monitor the deformation process of the surrounding rock of the roadway as the working face advances after hydraulic fracturing.

[0052] In this embodiment, the surface displacement cross-section is installed using the cross-point method for coal deformation monitoring.

[0053] Drill two 30mm diameter and 400mm diameter holes vertically in the middle of the top and bottom slabs of the tunnel, and two horizontally on both sides. 32mm×400mm wooden piles were driven into the holes, ensuring a tight fit between the piles and the hole walls. Bent measuring nails were installed at the ends of the piles on the roof and upper sidewalls, while flat-headed measuring nails were installed at the ends of the piles on the floor and lower sidewalls, with the measuring nails protruding 5mm from the pile ends. Monitoring sections were set along the tunnel axis, with a spacing of 0.8m between each monitoring section. After fracturing was completed, the relative displacement of the roof and floor slabs and the relative displacement of the two sidewalls were measured every 24 hours using a measuring tape. The deformation process of the surrounding rock as the working face advanced was recorded. If the daily deformation exceeded 5mm, the cause of the deformation needed to be analyzed and the support parameters adjusted.

[0054] In one embodiment, roof stability monitoring is performed using a roof delamination indicator, which consists of a fixture, measuring wire, sleeve, outer measuring cylinder, and inner measuring cylinder.

[0055] During installation, the anchors are fixed both within and outside the anchorage range of the roof strata. One end of the measuring wire is connected to the anchor, and the other end passes through a sleeve and connects to the scale devices of the outer and inner measuring cylinders. During monitoring, when delamination occurs in the roof strata, the relative positions of the anchors change, causing the measuring wire to move. By observing the scale changes in the outer and inner measuring cylinders, the delamination value of the roof strata within and outside the anchorage range is read. If the delamination value exceeds 20mm, it is determined that there is a potential risk to the stability of the roof strata, and reinforcement measures must be taken promptly.

[0056] According to one embodiment of the present invention, environmental monitoring includes: Groundwater and surface water samples were taken from the fracturing area and sent to the laboratory for chemical analysis to determine whether the water quality met environmental protection requirements.

[0057] In this embodiment, environmental monitoring adopts a chemical monitoring method, and the specific steps are as follows: Sampling: On the 1st, 3rd and 7th day after the start of fracturing operations, samples were taken from groundwater wells, surface drainage ditches and surrounding soil sampling points in the fracturing area. Groundwater was sampled at a depth of 5m, using a special water sampler, with a sample volume of 1L. Surface water was sampled in areas with gentle water flow, with a sample volume of 1L. Soil was sampled at a depth of 0.5m, with a sample volume of 500g. The samples were sealed and stored after sampling.

[0058] Sample processing: The collected water samples were filtered to remove suspended impurities, and the soil samples were air-dried and then ground through a 200-mesh sieve for later use.

[0059] Chemical composition analysis: The treated samples were sent to the laboratory, where the contents of anions such as chloride ions and sulfate ions in the water samples were analyzed by ion chromatography, and the contents of heavy metal ions (such as lead, cadmium, mercury, etc.) were analyzed by atomic absorption spectrophotometry; the contents of organic matter in the soil were analyzed by gas chromatography-mass spectrometry.

[0060] Evaluation criteria: Determine whether the chemical composition of water and soil samples meets environmental protection requirements. If all test indicators are within the standard limits, the fracturing operation is deemed to have no adverse environmental impact. If any indicators exceed the standards, corrective measures such as wastewater treatment and soil remediation must be taken.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in a coal seam working face, characterized in that, include: S100, boreholes are drilled in the fracturing area along the two grooves of the working face. The borehole inspection equipment is used to observe the structure of the roof rock mass and the fracture condition of the borehole wall in the fracturing section, and to compare the fracture differences before and after fracturing. The S200 uses monitoring instruments to monitor water pressure and flow parameters in real time during the fracturing process and plots pressure-flow curves. S300, record the water outflow status and parameters of this hole and adjacent holes respectively during the fracturing process; S400 is subject to multi-dimensional monitoring, including crack propagation monitoring, ground pressure monitoring, permeability monitoring, roof stability monitoring, coal body deformation monitoring, and environmental monitoring.

2. The method for detecting the multi-dimensional hydraulic fracturing effect of long and short holes in coal seam working faces according to claim 1, characterized in that, Step S100 includes: The probe is inserted into the borehole via a connecting rod. The probe is decelerated at fissures and special structures to observe and record the surrounding rock structure. After the observation is completed, the observation results are recorded, processed, and analyzed.

3. The method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in coal seam working faces according to claim 1, characterized in that, Step S200 includes: Under the pressure holding state, the pressure rises from 0 to the initial pressure and then drops to the pressure holding state. The pressure fluctuates up and down in a sawtooth pattern as the fracture develops. When a large fracture channel appears, the pressure drops sharply and the flow rate increases. Based on the characteristics of the pressure-flow curve, the timing of crack initiation, the stage of crack propagation, and the state of crack channel formation in the roof rock mass can be determined.

4. The method for detecting the multi-dimensional hydraulic fracturing effect of long and short holes in coal seam working faces according to claim 1, characterized in that, In step S300, recording the water outlet status and parameters of the orifice includes: When a large amount of water is observed gushing out of the wellhead, and the water pressure decreases and the flow rate increases simultaneously, it is determined that the wellhead sealer is damaged. The rod is immediately withdrawn and the wellhead sealer is replaced. The location of the fracturing section and the water outflow are recorded. After replacing the wellhead sealer, the rod is fed back for fracturing to ensure that there is no backflow in the well during each fracturing section.

5. The method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in coal seam working faces according to claim 1, characterized in that, In step S300, recording the water outlet status and parameters of the adjacent holes includes: When the water pressure in the fracturing section decreases and the flow rate increases, and the water output of the adjacent well reaches the preset threshold, it is determined that the hydraulic fracture has started and connected with the adjacent well. The fracturing time and water output parameters of the adjacent well are recorded. The fracturing of this section is stopped and the fracturing is moved to other fracturing sections to ensure that the fracturing points of the adjacent wells are staggered.

6. The method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in coal seam working faces according to any one of claims 1 to 5, characterized in that, The fracture propagation monitoring includes microseismic monitoring and water pressure monitoring. The microseismic monitoring involves installing an SOS microseismic monitoring system in the fracturing area and comparing the microseismic signals in the fracturing-enhanced area with those in the non-fracturing-enhanced area to determine the range of fracture development. The water pressure monitoring involves statistically analyzing real-time pressure data in the fracturing section, plotting water pressure curves, and inverting the fracture propagation based on the cyclical pattern of pressure drop-recovery-reopening.

7. The method for detecting the multi-dimensional hydraulic fracturing effect of long and short holes in a coal seam working face according to any one of claims 1 to 5, characterized in that, The ground pressure monitoring includes coal stress monitoring and roadway roof pressure monitoring; The coal stress monitoring includes: Each station is equipped with multiple borehole stress gauges. Each borehole stress gauge is installed with a set depth difference, the borehole diameter is a set diameter, the borehole is 1.2~1.5m away from the roadway floor and is installed horizontally, and the installation position is on the side of the main roadway close to the mining face. The roadway roof pressure monitoring includes: An anchor rod or anchor cable force gauge is used, and the stress state at the end of the anchor rod or anchor cable is calculated by measuring the deformation change of the strain gauge based on the principle of resistance strain gauge.

8. The method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in a coal seam working face according to any one of claims 1 to 5, characterized in that, The permeability monitoring adopts the coal seam permeability comparison method, which determines the degree of permeability improvement by observing and comparing the permeability data of the fracturing area and the unfracturing area.

9. The method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in a coal seam working face according to any one of claims 1 to 5, characterized in that, The coal deformation monitoring includes: Two holes with a diameter of 30mm and a depth of 400mm were drilled vertically in the middle of the top and bottom slabs and horizontally in the two sides. Wooden piles were driven into the holes. Curved measuring nails were installed at the ends of the wooden piles in the top slab and upper side slab, and flat-headed measuring nails were installed at the ends of the wooden piles in the bottom slab and lower side slab. The two monitoring sections were spaced 0.6 to 1.0m apart along the axial direction of the roadway to monitor the deformation process of the surrounding rock of the roadway as the working face advances after hydraulic fracturing.

10. The method for detecting the effect of multi-dimensional hydraulic fracturing with long and short holes in a coal seam working face according to any one of claims 1 to 5, characterized in that, The environmental monitoring includes: Groundwater and surface water samples were taken from the fracturing area and sent to the laboratory for chemical analysis to determine whether the water quality met environmental protection requirements.

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