CN112647909A - Gas extraction system and method - Google Patents
Gas extraction system and method Download PDFInfo
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- CN112647909A CN112647909A CN202011483753.4A CN202011483753A CN112647909A CN 112647909 A CN112647909 A CN 112647909A CN 202011483753 A CN202011483753 A CN 202011483753A CN 112647909 A CN112647909 A CN 112647909A
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/006—Production of coal-bed methane
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/18—Repressuring or vacuum methods
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/30—Specific pattern of wells, e.g. optimizing the spacing of wells
Abstract
The invention relates to the technical field of coal mining, in particular to a gas extraction system and a gas extraction method. The gas extraction system comprises a gas pump, a first extraction pipe and a second extraction pipe. The first extraction pipe is connected to the air pump through a first valve and provided with a plurality of first connecting ports, the second extraction pipe is connected to the air pump through a second valve and provided with a plurality of second connecting ports, and the second extraction pipe is arranged in parallel with the first extraction pipe and connected to the air pump through the second valve; the gas extraction method comprises the following steps: drilling a coal seam; connecting a gas extraction system; and gas is extracted. The gas extraction system and the method can effectively enhance the pressure relief and permeability enhancement of the coal seam.
Description
Technical Field
The invention relates to the technical field of coal mining, in particular to a gas extraction system and a gas extraction method.
Background
Coal is one of the basic energy sources on which human beings rely for survival, and the use of coal is not opened in both life and industry, for example: building material coal, power generation, industrial boiler coal, and the like. The generation process of coal is accompanied by the accumulation of gas, and the combustion and explosion of the gas are one of the main disasters in the coal mining, so that huge casualties and property loss are caused, and the gas needs to be extracted in the coal mining process. Because coal seams in China are generally poor in air permeability, low in permeability and high in gas content, the existing gas extraction technology is high in gas extraction difficulty and poor in pressure relief effect, and a good gas extraction effect is difficult to achieve.
Disclosure of Invention
The invention provides a gas extraction system and a gas extraction method, which aim to solve the technical problems of high difficulty in gas extraction and poor pressure relief effect.
The invention provides a gas extraction system, which comprises:
an air pump;
the first extraction pipe is connected to the air pump through a first valve, and the first valve is provided with a valve port capable of being communicated with the first gate slot; the first extraction pipe is provided with a plurality of first connecting ports, and the first connecting ports are used for connecting first drill holes on one side of a coal seam; and the number of the first and second groups,
the second extraction pipe is connected in parallel with the first extraction pipe and is connected to the air pump through a second valve, and the second valve is provided with a valve port capable of being communicated with a second crossheading; the second extraction pipe is provided with a plurality of second connecting ports, and the second connecting ports are used for connecting second drill holes on the other side of the coal seam.
Further, the first valve and/or the second valve is a three-way ball valve.
The invention provides a gas extraction method for extracting gas from a coal seam by using the gas extraction system, which comprises the following steps:
drilling a plurality of first drill holes on one side of the coal seam, drilling a plurality of second drill holes on the other side of the coal seam, wherein the first drill holes and the second drill holes are sequentially and alternately arranged at intervals;
connecting a gas extraction system, correspondingly and respectively connecting a plurality of first connecting ports of a first extraction pipe to a plurality of first drill holes, and correspondingly and respectively connecting a plurality of second connecting ports of a second extraction pipe to a plurality of second drill holes;
and gas is extracted, the on-off of corresponding valve ports of the first valve and the second valve is controlled, so that when the first extraction pipe extracts the gas, the second extraction pipe conveys air for the second drill hole, when the second extraction pipe extracts the gas, the first extraction pipe conveys air for the first drill hole, and the first extraction pipe and the second extraction pipe alternately extract coal bed gas.
Further, in the coal seam drilling step, the coal seam on the outer periphery of the first drill hole is fractured to generate a first fracture, and the coal seam on the outer periphery of the second drill hole is fractured to generate a second pressure fracture.
Further, in the coal seam drilling step, the coal seam on the outer peripheral side of the first drill hole is cut, and a plurality of first annular slots are formed and are axially arranged along the first drill hole at intervals; and cutting the coal bed at the outer peripheral side of the second drilling hole to generate a plurality of second annular slot grooves which are arranged at intervals along the axial direction of the second drilling hole.
Furthermore, the first fracturing fracture is communicated with the first annular fracture groove, the second fracturing fracture is communicated with the second annular fracture groove, and the second fracturing fracture is communicated with the first fracturing fracture.
Further, the first and second fractures are each formed by hydraulic fracturing; the first annular slot and the second annular slot are both formed by hydraulic cutting.
Further, in the coal seam drilling step, the coal seam on the outer peripheral side of the first drill hole is cut, and a plurality of first annular slots are formed and are axially arranged along the first drill hole at intervals; and cutting the coal bed at the outer peripheral side of the second drilling hole to generate a plurality of second annular slot grooves which are arranged at intervals along the axial direction of the second drilling hole.
Further, the first annular slot and the second annular slot are both formed by hydraulic slitting.
Further, the first valve comprises a first valve port, a second valve port and a third valve port, the first valve port is communicated and fixedly connected with the first extraction pipe, the second valve port is communicated and fixedly connected with an air inlet pipe of the air pump, and the third valve port can be communicated with the first gate slot;
the second valve comprises a fourth valve port, a fifth valve port and a sixth valve port, the fourth valve port is communicated and fixedly connected with the second extraction pipe, the fifth valve port is communicated and fixedly connected with an air inlet pipe of the air pump, and the sixth valve port can be communicated with the second crossheading;
the gas extraction step comprises a first pipeline control mode and a second pipeline control mode, wherein the first pipeline control mode and the second pipeline control mode are alternately carried out;
the first middle pipeline control mode is that the first valve is controlled to enable the first valve port to be communicated with the second valve port, the third valve port is sealed, and gas on the periphery of the first drill hole is conveyed to the gas pump through the first extraction pipe; controlling a second valve to enable a fourth valve port to be communicated with a sixth valve port, plugging a fifth valve port, and enabling air in a second crossheading to sequentially pass through the sixth valve port and a second extraction pipe to enter a second drill hole;
the second pipeline control mode is that the first valve is controlled to enable the first valve port to be communicated with the third valve port, the second valve port is blocked, and air in the first crossheading enters the first drill hole through the third valve port, the first valve port and the first extraction pipe in sequence; and controlling the second valve to enable the fourth valve port to be communicated with the fifth valve port, plugging the sixth valve port, and conveying the gas on the peripheral side of the second drill hole to the gas pump through the second extraction pipe.
The gas extraction system and the method provided by the embodiment of the invention have the following beneficial effects:
in the gas extraction system and the method provided by the embodiment of the invention, the gas extraction system comprises a gas pump, a first extraction pipe and a second extraction pipe, wherein the first extraction pipe is provided with a plurality of first interfaces which are sequentially arranged at intervals along the length of the first extraction pipe, and the second extraction pipe is provided with a plurality of second interfaces which are arranged at intervals along the second extraction pipe. When the gas extraction system is used for performing gas extraction on a coal seam, a plurality of first drill holes are drilled on one side of the coal seam, a plurality of second drill holes are drilled on the other side of the coal seam, the first drill holes and the second drill holes are sequentially and alternately arranged at intervals, namely, second drill holes are arranged between the adjacent first drill holes, first drill holes are arranged between the adjacent second drill holes, a first interface of a first extraction pipe is respectively connected to the first drill holes, a second interface of a second extraction pipe is respectively connected to the second drill holes, by controlling the connection and disconnection of a first valve and a second valve, when the first extraction pipe extracts gas around the first drill holes, the first extraction pipe is communicated with an air pump through the first valve, the first valve is used for communicating a valve port of a first crossheading and is in a blocking state, the valve port of the second valve for communicating the second crossheading is in an opening state, and the second valve is in a blocking state with the air pump, at the moment, air in the second crossheading enters the second extraction pipe and the second drill holes through the second valve, the peripheral side of the first drilling hole is in a negative pressure state, the second drilling hole is in an atmospheric pressure state (equivalent to the air pressure in the second crossheading), and a pressure difference is formed between the peripheral side of the first drilling hole and the peripheral side of the second drilling hole; when the second extraction pipe extracts gas on the peripheral side of the second drill hole, the second extraction pipe is communicated with the air pump through the second valve, a valve port of the second valve, which is used for communicating the second gate groove, is in a blocking state, air which is used for communicating the first gate groove enters the first extraction pipe and the peripheral side of the first drill hole through the first valve, the first drill hole is in an atmospheric pressure state (equivalent to the air pressure of an opening in the first gate groove), the peripheral side of the second drill hole is in a negative pressure state, and a pressure difference is formed between the peripheral side of the first drill hole and the peripheral side of the second drill hole; when the first extraction pipe and the second extraction pipe alternately extract gas, pressure difference is always kept between the peripheral side of the first drill hole and the peripheral side of the second drill hole, and when the on-off state of the first valve and the on-off state of the second valve are alternately changed, the direction of the pressure difference between the peripheral side of the first drill hole and the peripheral side of the second drill hole can be alternately changed, so that the effect of pressure relief and permeability increase of the coal seam gas can be enhanced by repeated operation, and the technical problems of high difficulty and poor pressure relief effect of the coal seam gas extraction are effectively solved; only need set up the both sides in the coal seam and respectively bore a hole to correspond and set up first adopting pipe, second and adopt pipe, first valve, second valve and air pump, have the advantage of simple structure, simple process, can use manpower and materials cost sparingly.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a schematic view of a gas extraction system according to an embodiment of the present invention;
fig. 2 is a schematic diagram of first pipeline control of the gas extraction method provided by the embodiment of the invention;
fig. 3 is a schematic diagram of control over a second pipeline of the gas extraction method provided by the embodiment of the invention.
Description of reference numerals:
010-a first gate; 020-second gate; 030-a first bore; 040-second bore hole;
050-coal seam;
100-a first extraction pipe; 200-a second extraction pipe;
300-a first valve; 310 — a first valve port; 320-a second valve port; 330-third valve port;
400-a second valve; 410-fourth valve port; 420-fifth valve port; 430-sixth valve port;
500-air pump.
Wherein arrows "→" in fig. 2 and 3 indicate an air flow direction schematic, and the arrows
Showing a gas flow schematic.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 1 to 3, embodiments of the present invention provide a gas extraction system and a method.
The gas extraction system provided by the embodiment includes, as shown in fig. 1, a gas pump 500, a first extraction pipe 100, and a second extraction pipe 200.
The first extraction pipe 100 is connected to the air pump 500 through a first valve 300, and the first valve 300 is provided with a valve port capable of being communicated with the first gate way 010; the first extraction pipe 100 is provided with a plurality of first connecting ports which are sequentially arranged at intervals along the length direction of the first extraction pipe 100, and the first connecting ports are used for connecting a first drill hole 030 on one side of a coal seam 050.
The second extraction pipe 200 is connected in parallel with the first extraction pipe 100 and is connected to the air pump 500 through a second valve 400, and the second valve 400 is provided with a valve port capable of being communicated with the second gate 020; the second extraction pipe 200 is provided with a plurality of second connecting ports which are sequentially arranged at intervals along the length direction of the second extraction pipe 200, and the second connecting ports are used for connecting second drill holes 040 on the other side of the coal seam 050.
The gas extraction method provided by the embodiment adopts the gas extraction system to extract gas from the coal seam, and comprises the following steps:
s102, drilling a coal seam, namely drilling a plurality of first drill holes 030 on one side of the coal seam 050, drilling a plurality of second drill holes 040 on the other side of the coal seam 050, and sequentially and alternately arranging the first drill holes 030 and the second drill holes 040;
s104, connecting the gas extraction system, correspondingly and respectively connecting the first connecting ports of the first extraction pipe 100 to the first drill holes 030, and correspondingly and respectively connecting the second connecting ports of the second extraction pipe 200 to the second drill holes 040;
s106, gas is extracted, and the on-off of corresponding valve ports of the first valve 300 and the second valve 400 are controlled, so that when the first extraction pipe 100 extracts gas, the second extraction pipe 200 conveys air for the second drill hole 040, when the second extraction pipe 200 extracts gas, the first extraction pipe 100 conveys air for the first drill hole 030, and the first extraction pipe 100 and the second extraction pipe 200 alternately extract 050 gas in a coal seam.
In the gas extraction system and the method provided by the embodiment of the invention, the gas extraction system comprises a gas pump, a first extraction pipe and a second extraction pipe, wherein the first extraction pipe is provided with a plurality of first interfaces which are sequentially arranged at intervals along the length of the first extraction pipe, and the second extraction pipe is provided with a plurality of second interfaces which are arranged at intervals along the second extraction pipe.
When the gas extraction system is used for performing gas extraction on a coal seam, a plurality of first drill holes are drilled on one side of the coal seam, a plurality of second drill holes are drilled on the other side of the coal seam, the first drill holes and the second drill holes are sequentially and alternately arranged at intervals, namely, second drill holes are arranged between the adjacent first drill holes, first drill holes are arranged between the adjacent second drill holes, a first interface of a first extraction pipe is respectively connected to the first drill holes, a second interface of a second extraction pipe is respectively connected to the second drill holes, by controlling the connection and disconnection of a first valve and a second valve, when the first extraction pipe extracts gas around the first drill holes, the first extraction pipe is communicated with an air pump through the first valve, the first valve is used for communicating a valve port of a first crossheading and is in a blocking state, the valve port of the second valve for communicating the second crossheading is in an opening state, and the second valve is in a blocking state with the air pump, at the moment, air in the second crossheading enters the second extraction pipe and the second drill holes through the second valve, the peripheral side of the first drilling hole is in a negative pressure state, the second drilling hole is in an atmospheric pressure state (equivalent to the air pressure in the second crossheading), and a pressure difference is formed between the peripheral side of the first drilling hole and the peripheral side of the second drilling hole; when the second extraction pipe extracts gas on the peripheral side of the second drill hole, the second extraction pipe is communicated with the air pump through the second valve, a valve port of the second valve, which is used for communicating the second gate groove, is in a blocking state, air which is used for communicating the first gate groove enters the first extraction pipe and the peripheral side of the first drill hole through the first valve, the first drill hole is in an atmospheric pressure state (equivalent to the air pressure of an opening in the first gate groove), the peripheral side of the second drill hole is in a negative pressure state, and a pressure difference is formed between the peripheral side of the first drill hole and the peripheral side of the second drill hole; when the first extraction pipe and the second extraction pipe alternately extract gas, pressure difference is always kept between the peripheral side of the first drilling hole and the peripheral side of the second drilling hole, and when the on-off state of the first valve and the on-off state of the second valve are alternately changed, the direction of the pressure difference between the peripheral side of the first drilling hole and the peripheral side of the second drilling hole can be alternately changed, so that the permeability of the coal seam can be improved by repeated operation, the effect of pressure relief and permeability increase of the coal seam gas is enhanced, and the technical problems of high difficulty and poor pressure relief effect of the coal seam gas extraction are effectively solved; only need set up the both sides in the coal seam and respectively bore a hole to correspond and set up first adopting pipe, second and adopt pipe, first valve, second valve and air pump, have the advantage of simple structure, simple process, can use manpower and materials cost sparingly.
Specifically, in this embodiment, the first valve 300 may be a three-way ball valve, and the second valve 400 may be a three-way ball valve. The three-way ball valve has the advantages of small fluid resistance, simple structure, small volume, light weight, tightness, reliability, convenient operation, convenient maintenance, difficult erosion, wide application range and the like.
In this embodiment, in the coal seam drilling step S102, the coal seam on the outer circumferential side of the first drill hole 030 is fractured to generate a first fracture 031, and the coal seam on the outer circumferential side of the second drill hole 040 is fractured to generate a second pressure fracture 041. The first fracturing crack 031 and the second fracturing crack 041 can effectively release gas in the coal seam, and the pressure relief and permeability increasing effects of the coal seam are more easily enhanced. When the first fracturing cracks 031 and the second fracturing cracks 041 are distributed uniformly in the coal seam 050, pressure relief and permeability enhancement of the coal seam can be further ensured.
In this embodiment, in the step S102 of drilling the coal seam, the coal seam on the outer circumferential side of the first drilled hole 030 is cut, and a plurality of first annular slotted grooves 032 arranged at intervals in the axial direction of the first drilled hole 030 are generated; the coal seam on the outer circumferential side of the second drilled hole 040 is cut, and a plurality of second annular slits 042 are formed and arranged at intervals in the axial direction of the second drilled hole 040. The arrangement of the first annular slit 032 and the second annular slit 042 can further enhance the pressure relief and permeability enhancement of the coal seam. Specifically, first annular slotted groove 032 and second annular slotted groove 042 evenly spaced set up, and both can evenly spaced in turn set up, further improve the permeability in coal seam, and then strengthen the release permeability of coal seam.
In this embodiment, the first fracture 031 is communicated with the first annular slit 032, the second fracture 041 is communicated with the second annular slit 042, and the second fracture 041 is communicated with the first fracture 031. So set up, can further improve the permeability in coal seam, reinforcing release permeability. Specifically, the first fracture 031 is connected to the second fracture 041.
In this embodiment, the first fracture 031 and the second fracture 041 are both formed by hydraulic fracturing; the first annular slit 032 and the second annular slit 042 are both formed by hydraulic cutting, which has the advantage of easy implementation.
It should be noted that, in the coal seam, only the corresponding pressure fractures may be formed; corresponding fracturing fractures and corresponding annular slots can also be formed in the coal seam, as described above; corresponding annular slots can also be formed in the coal seam only by machining, for example, cutting the coal seam on the outer peripheral side of the first bore 030 to generate a plurality of first annular slots 032 arranged at intervals in the axial direction of the first bore 030; the coal seam on the outer circumferential side of the second drilled hole 040 is cut, and a plurality of second annular slits 042 are formed and arranged at intervals in the axial direction of the second drilled hole 040.
In this embodiment, specifically, the first annular slit 032 and the second annular slit 042 are both formed by hydraulic cutting, which has the advantage of easy implementation.
In this embodiment, as shown in fig. 2 and 3, the first valve 300 includes a first valve port 310, a second valve port 320, and a third valve port 330, the first valve port 310 is communicated and fixedly connected to the first extraction pipe 100, the second valve port 320 is communicated and fixedly connected to an air inlet pipe of the air pump 500, and the third valve port 330 can be communicated with the first gate 010.
The second valve 400 comprises a fourth valve port 410, a fifth valve port 420 and a sixth valve port, 430 the fourth valve port 410 is communicated and fixedly connected to the second extraction pipe 200, the fifth valve port 420 is communicated and fixedly connected to the air inlet pipe of the air pump 500, and the sixth valve port 430 can be communicated with the second gate 020.
The gas extraction step comprises a first pipeline control mode and a second pipeline control mode, wherein the first pipeline control mode and the second pipeline control mode are alternately carried out;
the first pipeline control mode is as follows: controlling the first valve 300 to enable the first valve port 310 to be communicated with the second valve port 320, sealing the third valve port 330, and conveying the gas around the first drill hole 030 to the gas pump 500 through the first extraction pipe 100; the second valve 400 is controlled to enable the fourth valve port 410 to be communicated with the sixth valve port 430, the fifth valve port 420 is blocked, and air in the second smooth groove 020 sequentially passes through the sixth valve port 430, the fourth valve port 410 and the second extraction pipe 200 to enter the second borehole 040
The second pipeline control mode is as follows: controlling the first valve 300 to enable the first valve port 310 to be communicated with the third valve port 330, sealing the second valve port 320, and enabling air in the first gate 010 to enter the first borehole 030 through the third valve port 330, the first valve port 310 and the first extraction pipe 100 in sequence; the second valve 400 is controlled to connect the fourth valve port 410 with the fifth valve port 420, the sixth valve port 430 is blocked, and the gas around the second borehole 040 is delivered to the air pump 500 through the second extraction pipe 200.
The two valve control modes can ensure that when the gas is extracted by negative pressure from any drill hole, the pressure of the adjacent drill holes is the pressure of a roadway (corresponding gate way), and the value of the pressure of the adjacent drill holes is larger than the negative pressure value in the corresponding drill holes, namely, the pressure difference is formed between the adjacent drill holes, so that the gas flowing and the gas extraction in the coal bed through cracks are facilitated, and the pressure relief and desorption of the gas are facilitated. Through constantly switching two kinds of valve control methods, can constantly change coal seam crack both sides pressure differential direction and gas flow direction, be favorable to further release of pressure desorption of anisotropic coal seam gas, make things convenient for gas drainage.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Finally, it should also be noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
In the above embodiments, the descriptions of the orientations such as "up", "down", and the like are based on the drawings.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A gas extraction system, comprising:
an air pump (500);
the first extraction pipe (100) is connected to the air pump (500) through a first valve (300), and the first valve (300) is provided with a valve port capable of being communicated with a first gate way (010); the first extraction pipe (100) is provided with a plurality of first connecting ports which are sequentially arranged at intervals along the length direction of the first extraction pipe (100), and the first connecting ports are used for connecting a first drill hole (030) on one side of a coal seam (050); and the number of the first and second groups,
the second extraction pipe (200) is connected with the first extraction pipe (100) in parallel and is connected to the air pump (500) through a second valve (400), and the second valve (400) is provided with a valve port capable of being communicated with a second gate way (020); the second extraction pipe (200) is provided with a plurality of second connecting ports which are sequentially arranged at intervals along the length direction of the second extraction pipe (200), and the second connecting ports are used for connecting second drill holes (040) on the other side of the coal seam (050).
2. The gas extraction system of claim 1, wherein the first valve (300) and/or the second valve (400) is a three-way ball valve.
3. A gas extraction method for a coal seam by using the gas extraction system according to claim 1 or 2, the method comprising the steps of:
drilling a coal seam, drilling a plurality of first drill holes (030) on one side of the coal seam (050), drilling a plurality of second drill holes (040) on the other side of the coal seam (050), and sequentially and alternately arranging the first drill holes (030) and the second drill holes (040);
connecting a gas extraction system, correspondingly and respectively connecting a plurality of first connecting ports of a first extraction pipe (100) to a plurality of first drill holes (030), and correspondingly and respectively connecting a plurality of second connecting ports of a second extraction pipe (200) to a plurality of second drill holes (040);
and gas is extracted, the on-off of corresponding valve ports of the first valve (300) and the second valve (400) is controlled, so that when the first extraction pipe (100) extracts the gas, the second extraction pipe (200) conveys air for the second drill hole (040), when the second extraction pipe (200) extracts the gas, the first extraction pipe (100) conveys air for the first drill hole (030), and the first extraction pipe (100) and the second extraction pipe (200) alternately extract the gas in the coal seam (050).
4. The gas extraction method according to claim 3, wherein in the coal seam drilling step, the coal seam on the outer periphery of the first drill hole (030) is fractured to generate a first fracture (031), and the coal seam on the outer periphery of the second drill hole (040) is fractured to generate a second pressure fracture (041).
5. The gas extraction method according to claim 4, wherein in the coal seam drilling step, the coal seam on the outer peripheral side of the first drill hole (030) is cut to generate a plurality of first annular slotted grooves (032) which are axially arranged at intervals along the first drill hole (030); and cutting the coal seam on the outer peripheral side of the second drilling hole (040) to generate a plurality of second annular slot grooves (042) which are arranged at intervals along the axial direction of the second drilling hole (040).
6. The gas extraction method according to claim 5, wherein the first fracture (031) is communicated with the first annular slit (032), the second fracture (041) is communicated with the second annular slit (042), and the second fracture (041) is communicated with the first fracture (031).
7. The gas extraction method according to claim 6, wherein the first fractured fracture (031) and the second fractured fracture (041) are both formed by hydraulic fracturing; the first annular slit groove (032) and the second annular slit groove (042) are both formed by hydraulic slitting.
8. The gas extraction method according to claim 3, wherein in the coal seam drilling step, the coal seam on the outer periphery side of the first drill hole (030) is cut to generate a plurality of first annular slotted grooves (032) which are axially arranged at intervals along the first drill hole (030); and cutting the coal seam on the outer peripheral side of the second drilling hole (040) to generate a plurality of second annular slot grooves (042) which are arranged at intervals along the axial direction of the second drilling hole (040).
9. The gas extraction method according to claim 3, characterized in that the first annular slit groove (032) and the second annular slit groove (042) are both formed by hydraulic slitting.
10. The gas extraction method according to any one of claims 3 to 9, wherein the first valve (300) comprises a first valve port (310), a second valve port (320) and a third valve port (330), the first valve port (310) is communicated and fixedly connected to the first extraction pipe (100), the second valve port (320) is communicated and fixedly connected to an air inlet pipe of the air pump (500), and the third valve port (330) can be communicated with the first gate way (010);
the second valve (400) comprises a fourth valve port (410), a fifth valve port (420) and a sixth valve port, (430) the fourth valve port (410) is communicated and fixedly connected with the second extraction pipe (200), the fifth valve port (420) is communicated and fixedly connected with an air inlet pipe of the air pump (500), and the sixth valve port (430) can be communicated with a second gate way (020);
the gas extraction step comprises a first pipeline control mode and a second pipeline control mode, wherein the first pipeline control mode and the second pipeline control mode are alternately carried out;
the first middle pipeline control mode is that the first valve (300) is controlled to enable the first valve port (310) to be communicated with the second valve port (320), the third valve port (330) is blocked, and gas on the peripheral side of the first drill hole (030) is conveyed to the air pump (500) through the first extraction pipe (100); controlling the second valve (400) to enable the fourth valve port (410) to be communicated with the sixth valve port (430), blocking the fifth valve port (420), and enabling air in the second gate groove (020) to sequentially pass through the sixth valve port (430), the fourth valve port (410) and the second extraction pipe (200) to enter the second borehole (040);
the second pipeline control mode is that the first valve (300) is controlled to enable the first valve port (310) to be communicated with the third valve port (330), the second valve port (320) is blocked, and air in the first crossheading (010) sequentially passes through the third valve port (330), the first valve port (310) and the first extraction pipe (100) and enters the first borehole (030); and controlling the second valve (400) to enable the fourth valve port (410) to be communicated with the fifth valve port (420), blocking the sixth valve port (430), and conveying the gas on the peripheral side of the second drilling hole (040) to the air pump (500) through the second extraction pipe (200).
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