CN109751075B - Gas treatment method for bedding drilling of medium-hard coal seam - Google Patents
Gas treatment method for bedding drilling of medium-hard coal seam Download PDFInfo
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Abstract
The invention discloses a method for treating gas in bedding drilling of a medium-hard coal seam, which comprises the following steps: coring to determine average f value of coal seam, determining hydraulic cutting technological parameters, measuring the pumping radius r1 after hydraulic cutting in coal seam, and measuring hydraulic cutting and liquid CO2The extraction radius r2 after phase change fracturing is adopted, and the drill holes are rearranged according to the value r2 for hydraulic cutting and liquid CO2And (4) phase change fracturing, and connecting the hole sealing with an underground extraction system to test the extraction effect. The method comprises the steps of firstly utilizing a hydraulic slotting technology to directionally cut a gap along the trend direction of the coal seam, carrying out pressure relief disturbance on the coal seam, and then utilizing liquid CO2High-pressure gas generated after phase change is directionally fractured along the gap, so that the fracturing effect can be effectively improved, coal seam gas extraction is accelerated, the gas treatment time is shortened, and the safe production of a working face is ensured.
Description
Technical Field
The invention relates to the technical field of coal mine gas treatment, in particular to a method for treating gas in bedding drilling of a medium-hard coal seam.
Background
Coal is a main energy source in China, and the status of main energy sources can be still kept for a long time. Under the occurrence conditions of coal resources, the coal resources in China mainly come from underground mining. With the increasing of the coal seam burial depth and the mining intensity, coal mine gas also becomes a main disaster threatening coal mining. In China, most of the serious coal mine accidents which occur in recent years are caused by gas accidents. Although the invested capital and personnel for gas control in mines are increasing, the threat of gas disasters still exists.
Once gas accidents happen, the gas accidents are often accompanied with group death and group injury, so that great loss is caused to enterprises and workers, and the concealment of gas and the invisibility of human bodies often cause people to be numb and relaxed, so that the occurrence of various major gas accidents is stopped and prevented at present when a harmonious society is built, and the method has important significance.
Coal bed gas in China has the characteristic of 'two low and one high', namely the coal bed gas is low in pressure, the coal bed is low in air permeability and high in coal bed gas adsorption capacity, and the characteristic brings great difficulty to coal bed mining and gas drainage. The gas existing in the coal body is mainly adsorbed gas, the gas accounting for 80% -90% of the gas content of the coal body is adsorbed in the microporous structure of the coal body, and only 10% -20% of free gas exists in joints and cracks of the coal body.
Years of scientific research and production practice in China, especially coal mine gas drainage experience shows that gas can be analyzed and transported in a large amount only under the condition that the stress strain of a coal rock body changes.
After dozens of years of large-scale coal mining in China, gas treatment means are continuously developed and enriched, and the currently applied gas treatment methods mainly comprise measures such as bedding drilling, cross-layer drilling, loosening blasting, protective layer mining, ground drilling extraction, hydraulic gas treatment technology and the like.
Bedding drilling is the earliest used underground gas extraction method, and still occupies an important position in coal seam extraction until now. Bedding drilling is drilling in a coal seam, the utilization efficiency of the drilling is high, and the defects are that the drilling work amount is large, the extraction time is long, and certain influence is exerted on normal taking over of a mine.
The loosening blasting technology mainly utilizes the explosion energy of explosives, a pressure relief area is formed in the coal body around the coal body, a stress zone is made to be transferred to the deep part of the coal body, meanwhile, more cracks are generated in the coal body through blasting, the air permeability of the coal body is increased, gas in the coal body is enabled to be discharged in a large amount, better conditions are created for gas emission, however, a large amount of heat is released simultaneously when high-temperature flame is generated in the blasting process of the explosives, a large amount of harmful gas can be generated due to insufficient reaction, meanwhile, gas accidents are easily caused due to the fact that coal bed gas exists, and safety is low.
After long-term theoretical research for many years and combined with field engineering practice, the protective layer technology is the most effective, safe and economic technology for preventing and treating coal and gas outburst for coal seams with outburst risks. The protective layer mining technology is listed as a outburst prevention technology which should be preferentially adopted in regional outburst prevention measures by outburst prevention regulations, but most mining areas in China are single coal seams or the intervals between the coal seams are too large, so that the mining and using range of the protective layer is limited.
The hydraulic gas treatment measures comprise various gas treatment methods such as hydraulic punching, hydraulic slotting, hydraulic scouring and hydraulic fracturing. The hydraulic punching is generally to perform high-pressure water washing on a coal seam under the shield of a bottom suction roadway or a rock pillar, the hydraulic slotting is generally to perform slotting on coal bodies in a crossheading, and the hydraulic fracturing is generally to perform high-pressure fracturing on hard coal in the bottom suction roadway.
The principle of hydraulic cutting is that high-pressure water jet is used to cut coal bodies on two sides of a drill hole in the drill hole, 1 flat slot with a certain depth is formed on two sides of the drill hole, the cut coal blocks are taken out of the hole by water flow, and the exposed area of the coal bodies is increased, and the flat slot is equivalent to a layer of an extremely thin protective layer mined in a local range, so that the coal bodies near the drill hole are locally relieved, and the flowing condition of gas is improved.
In order to reduce gas accidents in coal mining and guarantee the safety of miners, the technicians in the field still continuously innovate a gas treatment method.
Disclosure of Invention
The invention provides a method for treating gas in bedding drill holes of a medium-hard coal seam, which aims to solve the technical problems of small disturbance of the existing single gas treatment means on the coal seam, small drilling extraction radius, large gas extraction engineering quantity and long extraction time.
According to one aspect of the invention, the invention provides a method for treating gas in bedding drilling of a medium-hard coal seam, which comprises the following steps:
s1, drilling and coring along the coal seam direction on a stope face, measuring the average f value of the coal seam, and preliminarily determining hydraulic slotting process parameters according to the average f value, wherein the hydraulic slotting process parameters mainly comprise the selection of a high-pressure pump model, the size of a slotting nozzle and the width of a slotting, and f is a firmness coefficient of coal;
s2, performing hydraulic cutting on the coal seam construction drill hole by using the cutting equipment selected in the step S1, and measuring the extraction radius r1 after the hydraulic cutting;
s3, drilling holes in the coal seam in parallel construction by taking the extraction radius r1 determined in the step S2 as the center distance of the adjacent drill holes, performing hydraulic slotting, and performing liquid CO in the drill holes subjected to hydraulic slotting2Blasting and drilling by phase change fracturing, measuring hydraulic cutting and liquid CO2The extraction radius r2 under the double influence of phase change fracturing;
s4, hydraulic slotted drilling and liquid CO determination in step S32The extraction radius r2 of the drill hole under the double influence of phase change fracturing is used as the center distance between adjacent drill holes, the drill holes are rearranged, and the hydraulic slotting work is completed;
s5, performing liquid CO once every other drilling hole2Fracturing the coal bed in a phase change fracturing blasting mode;
s6, sealing the newly-arranged drill holes and connecting the newly-arranged drill holes with a downhole extraction system, and periodically measuring and counting extraction parameters;
and S7, after the designed extraction time is reached, carrying out extraction effect inspection.
Further, n drill holes with equal intervals are constructed in the coal seam in parallel, n is larger than or equal to 5, the interval is 0.8-2 m, one drill hole on the outermost side is selected for hydraulic slotting according to the hydraulic slotting process parameters determined in the step S1, and slotting parameters are recorded during hydraulic slottingThe seam parameters comprise seam pressure, coal output, seam cutting time and water consumption, the rest n-1 drill holes are sealed and connected with an underground extraction system, and SF is adopted6And determining the extraction radius r1 under the slotting parameter by a tracer gas method.
Further, in step S3, the method for measuring the extraction radius r2 is: constructing m drill holes in the coal seam in parallel, wherein m is more than or equal to 5, the distances between the adjacent drill holes are r1, d, … and d respectively, wherein d is less than r1, performing hydraulic slotting on the drill holes which are positioned at the outer sides and have the distance between the adjacent drill holes r1 according to the same hydraulic slotting process parameters in the step S2, and after slotting is finished, performing hydraulic slotting on liquid CO2Pushing the phase change fracturing device into the drilled hole after hydraulic slotting for implosion, then sealing the rest m-1 drilled holes and connecting the drilled holes with an underground extraction system, and adopting SF6Determination of hydraulic cutting seam and liquid CO by tracer gas method2And (3) extracting radius r2 under the double influence of phase change fracturing.
Further, the hydraulic cutting is a directional hydraulic cutting parallel to the coal seam and inclined along the radial direction of the drill rod.
Furthermore, the drill bit adopted by the hydraulic slotting is a drilling and slotting integrated drill bit, drilling is carried out at low pressure, and slotting is carried out at high pressure.
Furthermore, a safe coal pillar of 20-30 m is reserved in the hydraulic slotting during construction.
Further, the hole sealing mode is a cement mortar hole sealing method or a Marilyn hole sealing method or a two-plugging one-injection method.
Further, the hole sealing depth is 15-20 m.
Further, the extraction negative pressure of the underground extraction system is not less than 13 kPa.
Further, the extraction effect inspection comprises that the content of residual gas is less than 8m3/t。
The invention has the following beneficial effects:
the method for treating gas in bedding drill holes of medium-hard coal seams comprises the steps of firstly carrying out hydraulic slotting to obtain an extraction radius r1 under the condition of hydraulic slotting, then arranging and constructing hydraulic slotting drill holes according to the extraction radius r1, and carrying out liquid state drilling in the hydraulic slotting drill holesCO2The hydraulic cutting and the liquid CO can be quickly and accurately obtained according to the step of phase change fracturing blasting drilling2The extraction radius r2 under the dual influence of phase change fracturing is utilized, the extraction radius r2 is utilized to re-lay the hydraulic slotted drill hole on the stope face of the coal seam, and the hydraulic slotted drill hole is subjected to corresponding liquid CO2Phase change cracking and gas extraction. A seam is directionally cut along the coal seam trend direction by utilizing a hydraulic cutting seam technology, the pressure relief disturbance is carried out on the coal seam, and the hydraulic cutting seam is liquid CO2The phase change cracking provides cracking direction to make liquid CO2High-pressure gas generated by expansion cracks along the direction of the coal seam, the length of a fractured zone of the drilled hole after cracking is effectively increased, the gas extraction radius is increased, and the gas extraction engineering quantity and the extraction time are shortened. The invention adopts hydraulic cutting and liquid CO2The phase change fracturing synergistic method is used for gas control of medium-hard coal seams, so that overall disturbance to the coal seams is greatly improved, conditions and channels are provided for gas desorption and migration, and CO is used2After gasification, due to the competitive adsorption effect with gas, the gas is driven and replaced, so that the extraction of the gas in the coal seam is accelerated, the gas treatment time is shortened, and the safe production of a working face is ensured.
In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below with reference to the drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic flow chart of a method for treating gas in a down-hole of a medium-hard coal seam according to a preferred embodiment of the invention;
FIG. 2 is a borehole layout for hydraulic slotted extraction radius determination according to a preferred embodiment of the present invention;
FIG. 3 is a hydraulic slitting and liquid CO embodiment of the present invention2Extraction radius measurement under dual influence of phase change fracturingAnd (4) determining a drilling layout.
Detailed Description
The embodiments of the invention will be described in detail below with reference to the accompanying drawings, but the invention can be embodied in many different forms, which are defined and covered by the following description.
Fig. 1 is a schematic flow chart of a method for treating gas in a bedding drill hole of a medium-hard coal seam according to a preferred embodiment of the invention.
As shown in fig. 1, the method for treating gas in the bedding drilling hole of the medium-hard coal seam in the embodiment includes the following steps:
s1, drilling and coring along the coal seam direction on a stope face, measuring the average f value of the coal seam, and preliminarily determining hydraulic slotting process parameters according to the average f value, wherein the hydraulic slotting process parameters mainly comprise the selection of a high-pressure pump model, the size of a slotting nozzle and the width of a slotting, and f is a firmness coefficient of coal;
s2, performing hydraulic cutting on the coal seam construction drill hole by using the cutting equipment determined in the step S1, and measuring the extraction radius r1 after the hydraulic cutting;
s3, drilling holes in the coal seam in parallel construction by taking the extraction radius r1 determined in the step S2 as the center distance of the adjacent drill holes, performing hydraulic slotting, and performing liquid CO in the drill holes subjected to hydraulic slotting2Blasting and drilling by phase change fracturing, measuring hydraulic cutting and liquid CO2The extraction radius r2 under the double influence of phase change fracturing;
s4, hydraulic slotted drilling and liquid CO determination in step S32The extraction radius r2 of the drill hole under the double influence of phase change fracturing is used as the center distance between adjacent drill holes, the drill holes are rearranged, and the hydraulic slotting work is completed;
s5, performing liquid CO once every other drilling hole2Fracturing the coal bed in a phase change fracturing blasting mode;
s6, sealing the newly-arranged drill holes and connecting the newly-arranged drill holes with a downhole extraction system, and periodically measuring and counting extraction parameters;
and S7, after the designed extraction time is reached, carrying out extraction effect inspection.
Liquid CO2The phase-change cracking technology is a new type of coalThe layer permeability increasing technology belongs to physical high-pressure gas blasting, has the advantages of no spark in the blasting process, simple and convenient operation, cyclic utilization, no pollution, safety, high efficiency and the like, and can be well applied to high-gas low-permeability coal layers. In the method for treating gas in bedding drilling of the medium-hard coal seam, a seam is directionally cut along the trend direction of the coal seam by utilizing a hydraulic cutting technology, the pressure relief disturbance is carried out on the coal seam, and then liquid CO is utilized2High-pressure gas generated after phase change is directionally fractured along the cracks, so that the fracturing effect can be effectively improved, the generation and the extension of the cracks in the coal bed are increased, the overall disturbance to the coal bed is greatly improved, conditions and channels are provided for gas desorption and migration, and CO is used2After gasification, due to the competitive adsorption effect with gas, the gas is driven and replaced, so that the extraction of the gas in the coal seam is accelerated, the gas treatment time is shortened, and the safe production of a working face is ensured.
The method for treating gas in bedding drilling of the medium-hard coal seam comprises the steps of firstly carrying out hydraulic cutting to obtain an extraction radius r1 under the hydraulic cutting condition, and then arranging and constructing hydraulic cutting drilling holes according to the extraction radius r1 to carry out liquid CO drilling2The hydraulic cutting and the liquid CO can be quickly and accurately obtained according to the step of phase change fracturing blasting drilling2The extraction radius r2 under the dual influence of phase change fracturing, and the hydraulic cutting seam is liquid CO2The phase change cracking provides cracking direction to make liquid CO2High-pressure gas generated by expansion cracks along the direction of the coal seam, the length of a fractured zone of the drilled hole after cracking is effectively increased, the gas extraction radius is increased, and the gas extraction engineering quantity and the extraction time are shortened.
In step S1, drilling and coring are performed on the stope along the coal seam, in order to ensure the validity of the detection data, it is preferable to take several more sampling points at positions at equal intervals around and in the middle of the stope, drill a coal sample at the sampling points by using a coring drill rod, and send the coal sample to a laboratory to determine the value f, where the compressive strength of the coal is generally 10f, so as to initially select the model of the high-pressure pump and the size of the nozzle.
During slotting, the pressure and flow output by the pump are certain, if no flow is lost in the whole pipeline, the pressure at the nozzle is the pressure of the pump, and the pressure at the nozzle is as follows:
in the formula (I);
p-jet pressure, MPa;
q-jet volume flow, L/min;
mu-nozzle flow coefficient, taking 0.82;
d, the diameter of the section of the outlet of the nozzle is mm;
therefore, the slotting can be ensured to be smoothly performed only if P is more than 10f, and the rated pressure of the high-pressure pump is more than P when the high-pressure pump is selected.
In step S2, the method for measuring the extraction radius r1 includes: according to the hole distribution mode of figure 2, n parallel drill holes with equal intervals are constructed in the coal seam, n is larger than or equal to 5, preferably 5-8, the intervals are 0.8-2 m, one drill hole on the outermost side is selected for hydraulic slotting according to hydraulic slotting process parameters preliminarily determined in the step S1, slotting parameters are recorded during hydraulic slotting, the slotting parameters comprise slotting pressure, coal yield, slotting time and water consumption, the rest n-1 drill holes are sealed and connected with an underground extraction system, the hydraulic slotting drill holes are sealed, SF is adopted for sealing the holes, and the hole distribution mode is adopted6And determining the extraction radius r1 under the slotting parameter by a tracer gas method.
The number and the spacing of the drill holes are selected and determined according to actual geological parameters of the coal seam, the accuracy of the extraction radius is determined by the proper drill hole spacing and the proper drill hole number, in practical application, if the drill hole spacing is selected to be larger, the drill hole number is properly reduced, and if the drill hole spacing is selected to be smaller, the drill hole number can be properly increased, so that the effectiveness of the measured extraction radius is ensured.
The concrete construction method of the parallel drilling comprises the following steps: preparing a drilling machine, a high-pressure sealing drill rod and a drilling and slotting integrated drill bit, and constructing n drill holes in parallel along the coal seam trend in an engine lane according to the hole distribution mode shown in the figure 2, wherein the inclination angle of each drill hole is 3-5 degrees, the drill holes with the diameter phi of 94mm and the length of 120m are drilled, and the drill hole interval is 0.8-2 m. The diameter and length of the drill hole can be adjusted according to the geological parameters of the actual coal seam, and are not limited to the numerical values.
The specific method of hydraulic slotting comprises the following steps: selecting the drilling hole on the outermost side, connecting the high-pressure sealing drill rod with the high-pressure pump, adjusting to a set pump pressure, enabling the drilling and slotting integrated drill bit to enter a slotting mode, adjusting the angle of the drill bit to enable the drill bit to cut a slot along the radial direction, and slotting while retreating, and stopping slotting when the slotting position reaches a position 20m away from the machine lane.
One drill hole on the outermost side is selected to be subjected to hydraulic slotting, other drill holes are used as investigation holes, the investigation holes are sealed and connected with an underground extraction system, the hole sealing depth is 15-20 m, cement mortar is used for sealing the hole in a hole sealing mode, the hydraulic slotting drill holes are sealed at the same time, the hole sealing depth is also 15-20 m, cement mortar is used for sealing the hole in a hole sealing mode, and then the extraction radius r1 is measured by adopting tracer gas. In other embodiments, the hole sealing method can also be selected from a Marilsan hole sealing method or a two-plugging one-injection method, the sealing performance of the drill hole is related to the extraction effect, the hole sealing methods are all common hole sealing methods, and the hole sealing length is determined according to actual conditions.
SF6Is a colorless, odorless, non-combustible and non-corrosive gas, has stable properties, has inertia higher than that of nitrogen and other rare gases at normal temperature, has high thermal stability and light stability, is not influenced by climate such as severe cold and severe heat during release, and has SF6The gas has large physical activity, can be quickly mixed and uniformly distributed in a detection space in disturbed air, is insoluble in water, has no sedimentation and coagulation, is not adsorbed on the surface of underground materials, does not react with alkali, and is visible as SF6Is an ideal mine tracer gas. 20ml SF6Injecting tracer gas into the hydraulic slotted borehole, and regularly detecting SF in the observation hole6The gas concentration is recorded, and after the sealing tightness of the sealing hole is ensured, SF6The tracer gas enters the observation hole mainly through extraction negative pressure so as to be according to SF6The diffusion distance of the tracer gas is measured to obtain the extraction radius r 1. SF6The gas detection adopts the commercially available portable SF6And (7) detecting the instrument. For example, if SF is detected in all of the 2 nd to a nd boreholes6Tracer gas, no SF detected in the a +1 th borehole6And (d) tracer gas, r1 is (a-1) hole spacing.
In this embodiment, in step S3, the method for measuring the extraction radius r2 includes: constructing m parallel drill holes in the coal seam according to the hole distribution mode of figure 3, wherein m is more than or equal to 5, preferably 5-8, the distances between adjacent drill holes are r1, d, … and d respectively, wherein d is less than r1, d is preferably 1m, performing hydraulic slotting on the drill holes which are adjacent to each other and have the distance between r1 and are positioned at the outer sides according to the same hydraulic slotting process parameters in the step S2, and after slotting is finished, performing hydraulic slotting on liquid CO2Pushing the phase change fracturing device into the drilled hole after hydraulic slotting for implosion, then sealing the rest m-1 drilled holes and connecting the drilled holes with an underground extraction system, and adopting SF6Determination of hydraulic cutting seam and liquid CO by tracer gas method2And (3) extracting radius r2 under the double influence of phase change fracturing.
The distance between adjacent drilled holes is selected as r1, d, … and d, wherein d is less than r1, and the drilled holes after hydraulic slotting are selected by liquid CO2The phase change cracking equipment is used for filling liquid CO into the blasting tube section by section2Then, the release pipe, the blasting pipe and the pushing rod are connected with each other, meanwhile, a drilling machine is used as power, the release pipe and the blasting pipe are pushed into a coal bed needing fracturing by the pushing rod, after the release pipe is pushed to a designated position, the pushing is stopped, the drilling machine is used as a lower support body, and liquid CO is delivered to the coal bed through the drilling machine2The phase change cracking device is fixed in a drill hole and is connected with a tail terminal binding post by adopting a detonating cord, and the device is exploded after field constructors evacuate and liquid CO2The high-pressure gas generated after phase change is directionally fractured along the seam of the hydraulic cutting seam, so that the length of a fractured zone of the drilled hole is effectively increased, the gas extraction radius is increased, and the gas extraction engineering quantity and the extraction time are shortened. Using the remaining m-1 drill holes as investigation holes, sealing the remaining m-1 drill holes with cement mortar, or adopting a Marilyn sealing method or a two-plugging one-injection sealing method, wherein the sealing length is 15-20 m, connecting the sealing length with a downhole extraction system, and mixing liquid CO2Sealing the blast hole with cement mortar or other sealing methods, wherein the sealing length is 15-20 m, and sealing the hole with 20ml of SF6Gas injection of liquid CO2In a blast hole, then periodically detectingSF in remaining m-1 boreholes6Gas concentration and recording, thus according to SF6The gas diffusion distance is measured to obtain the extraction radius r 2. For example: if SF is detected in all of the 2 nd to the b th drill holes6Tracer gas, while no SF was detected in the b +1 th borehole6And r2 is r1+ (b-2) × d.
In the embodiment, the hydraulic cutting is a directional hydraulic cutting which is parallel to the coal seam and tends to be along the radial direction of the drill rod, and after the drill bit reaches a preset position, the angle of the drill bit is adjusted, so that the cutting nozzle is parallel to the trend of the coal seam, and the cutting edge retreats.
In the embodiment, the drill bit used for hydraulic slotting is a drilling and slotting integrated drill bit, drilling is carried out at low pressure, and slotting is carried out at high pressure. The operation flow of the drilling and slotting integrated drill bit is as follows: in the drilling process of the drilling machine, the powder is discharged by the drilling machine in cooperation with low-pressure water fed into the drill rod, and the drilling operation is completed together with the drilling machine. When hydraulic slotting is carried out, the high-pressure pump station is pressurized, and after the water pressure reaches a set pressure value, the angle of the drill bit is adjusted, so that the drill bit cuts a slot along the radial direction, and slotting operation is carried out. The integrated drill for drilling and slotting can meet the requirements of drilling and slotting at any time, low pressure and high pressure are relative concepts, and the working pressures of drilling and slotting of different drill bits are different.
In the embodiment, a safe coal pillar of 20-30 m is reserved in the hydraulic slotting during construction. The safety coal pillar is reserved for the safety of field construction.
In the embodiment, the extraction negative pressure of the underground extraction system is not less than 13 kPa. The extraction negative pressure is too small, so that the extraction efficiency and the extraction effect are reduced, and the extraction negative pressure is not less than 13kPa, so that the extraction inspection result can meet outburst prevention regulations after the extraction reaches the specified time.
In this embodiment, the extraction effect test includes that the content of residual gas is less than 8m3T is calculated. The specific operation is as follows: after the designed extraction time is reached, according to outburst prevention regulations, at least 2 measuring points are arranged along the working face direction at intervals of 30-50 m along the advancing direction of the stope working face, the residual gas content of the coal bed is measured, and when the residual gas content is less than 8m3And the extraction reaches the standard at the time of/t.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method for treating gas in bedding drilling of a medium-hard coal seam is characterized by comprising the following steps:
s1, drilling and coring along the coal seam direction on a stope face, measuring the average f value of the coal seam, and preliminarily determining hydraulic slotting process parameters according to the average f value, wherein the hydraulic slotting process parameters mainly comprise the selection of a high-pressure pump model, the size of a slotting nozzle and the width of a slotting, and f is a firmness coefficient of coal;
s2, performing hydraulic slotting on the construction drill holes of the coal seam by using slotting equipment selected according to the hydraulic slotting process parameters determined in the step S1, and determining the extraction radius r1 after hydraulic slotting;
s3, drilling holes in the coal seam in parallel construction by taking the extraction radius r1 determined in the step S2 as the center distance of the adjacent drill holes, performing hydraulic slotting, and performing liquid CO in the drill holes subjected to hydraulic slotting2Blasting and drilling by phase change fracturing, measuring hydraulic cutting and liquid CO2The extraction radius r2 under the double influence of phase change fracturing;
s4, hydraulic slotted drilling and liquid CO determination in step S32The extraction radius r2 of the drill hole under the double influence of phase change fracturing is used as the center distance between adjacent drill holes, the drill holes are rearranged, and the hydraulic slotting work is completed;
s5, performing liquid CO once every other drilling hole2Fracturing the coal bed in a phase change fracturing blasting mode;
s6, sealing the newly-arranged drill holes and connecting the newly-arranged drill holes with a downhole extraction system, and periodically measuring and counting extraction parameters;
and S7, after the designed extraction time is reached, carrying out extraction effect inspection.
2. The method for treating gas in bedding drilling of medium-hard coal seam according to claim 1,
in step S2, the method for measuring the extraction radius r1 includes:
constructing n drill holes with equal intervals in a coal seam in parallel, wherein n is more than or equal to 5, the interval is 0.8-2 m, selecting one drill hole on the outermost side for hydraulic slotting according to hydraulic slotting process parameters preliminarily determined in the step S1, recording slotting parameters during hydraulic slotting, wherein the slotting parameters comprise slotting pressure, coal yield, slotting time and water consumption, sealing the rest n-1 drill holes and connecting an underground extraction system, and adopting SF6And determining the extraction radius r1 under the slotting parameter by a tracer gas method.
3. The method for treating gas in bedding drilling of medium-hard coal seam according to claim 1,
in step S3, the method for measuring the extraction radius r2 includes:
constructing m drill holes in the coal seam in parallel, wherein m is more than or equal to 5, the distances between the adjacent drill holes are r1, d, … and d respectively, wherein d is less than r1, performing hydraulic slotting on the drill holes which are positioned at the outer sides and have the distance between the adjacent drill holes r1 according to the same hydraulic slotting process parameters in the step S2, and after slotting is finished, performing hydraulic slotting on liquid CO2Pushing the phase change fracturing device into the drilled hole after hydraulic slotting for implosion, then sealing the rest m-1 drilled holes and connecting the drilled holes with an underground extraction system, and adopting SF6Determination of hydraulic cutting seam and liquid CO by tracer gas method2And (3) extracting radius r2 under the double influence of phase change fracturing.
4. The medium hard coal seam bedding drilling gas treatment method according to any one of claims 1 to 3,
the hydraulic cutting is a directional hydraulic cutting which is inclined parallel to the coal seam and along the radial direction of the drill rod.
5. The medium hard coal seam bedding drilling gas treatment method according to any one of claims 1 to 3,
the hydraulic slotting adopts a drill bit which is a drilling and slotting integrated drill bit, drilling is carried out in the low pressure process, and slotting is carried out in the high pressure process.
6. The medium hard coal seam bedding drilling gas treatment method according to any one of claims 1 to 3,
and a safe coal pillar of 20-30 m is reserved in the hydraulic cutting seam during construction.
7. The medium hard coal seam bedding drilling gas treatment method according to any one of claims 1 to 3,
the hole sealing mode is a cement mortar hole sealing method or a Marilsan hole sealing method or a two-plugging one-injection method.
8. The medium hard coal seam bedding drilling gas treatment method according to any one of claims 1 to 3,
the depth of the hole sealing is 15-20 m.
9. The medium hard coal seam bedding drilling gas treatment method according to any one of claims 1 to 3,
and the extraction negative pressure of the underground extraction system is not less than 13 kPa.
10. The medium hard coal seam bedding drilling gas treatment method according to any one of claims 1 to 3,
the extraction effect inspection comprises that the content of residual gas is less than 8m3/t。
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