Method for strengthening drilling extraction exhaustion period underpressure gas

Abstract

The invention discloses a method for intensifying drilling extraction exhaustion period underpressure gas, which comprises the following steps of: sealing a drilling hole, fully utilizing gas desorbed in the drilling hole to realize self-boosting of the drilling hole, enabling the pressure in the drilling hole to reach a required value in a gas injection supplementing manner, and enabling the pressure in the drilling hole to reach a required value through the reciprocating motion of a transmission pipe and a rubber sealing head; alternating air pressure pulsation is generated in the drill hole to crack the coal body alternately, and the permeability of the coal body is increased; meanwhile, in the reciprocating motion process, gas in the drill hole can be driven to be alternately compressed and recovered, so that the coal seam gas flowing driving force is improved, and under-pressure gas in the extraction exhaustion period is promoted to be desorbed to the drill hole from micropores in a reciprocating motion mode; and after completion, performing gas extraction on the drill hole, and repeating the process for multiple times until the gas extraction of the coal seam reaches the standard. According to the method, on the premise that construction is simple and large equipment is not needed, reinforced extraction treatment is carried out on the gas drill hole entering the depletion period, so that the gas extraction efficiency of the drill hole is improved, and subsequent safe mining of a coal seam is facilitated.

Description

Technical Field

[0001] The invention relates to a method for strengthening gas extraction, in particular to a method for strengthening drilling extraction of under-pressure gas in the exhaustion period. Background Art

[0002] Gas extraction is the fundamental way to prevent and control gas. However, many of the coal seams that have been mined are low-permeability coal seams. It is difficult to achieve the required extraction within the specified time by conventional drilling extraction. Therefore, various technical means are needed to increase the permeability of coal seams, among which mining pressure relief and permeability enhancement are the most significant. For single low-permeability coal seams without mining pressure relief mining conditions, other artificial forced permeability enhancement measures must be taken. Considering the differences in coal-breaking media, it can be roughly divided into two categories: hydraulic permeability enhancement technology and waterless permeability enhancement technology. After field test application, good permeability enhancement effects have been achieved in many low-permeability coal seams. However, many low-permeability coal seams not only have low permeability, but also low gas saturation. Even though different technical means, such as hydraulic fracturing, hydraulic cutting, pre-splitting blasting, carbon dioxide fracturing blasting, etc., can improve the permeability of coal seams to a certain extent, the low gas saturation still causes gas extraction to quickly enter the exhaustion period after a short period of time, ultimately leading to insufficient gas flow force. However, in fact, a large amount of gas is still stored in the micropores of the coal body. The reason is that the insufficient gas flow force cannot drive the gas in the micropores to desorb into the borehole, which greatly restricts the gas extraction efficiency.

[0003] Therefore, how to provide a method for enhanced gas extraction that can perform enhanced extraction treatment on gas boreholes that have entered the depletion period under the premise of simple construction and without the need for large-scale equipment, thereby improving the gas extraction efficiency of the boreholes and facilitating the subsequent safe mining of coal seams, is the research direction required by the present invention. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the present invention provides a method for enhanced drilling extraction of under-pressure gas in the depletion period. With simple construction and no need for large-scale equipment, the method can perform enhanced extraction treatment on gas boreholes that have entered the depletion period, thereby improving the gas extraction efficiency of the borehole and facilitating the subsequent safe mining of the coal seam.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: a method for strengthening the extraction of under-pressure gas in the exhaustion period by drilling, the specific steps are:

[0006] A. Laying out the enhanced extraction system: The enhanced extraction system includes a bracket, a power unit, a transmission pipe, a rubber sealing head, a hydraulic pump station and a pulsation control console. The power unit is installed on the bracket, and one end of the transmission pipe passes through the power unit. The power unit can drive the transmission pipe to reciprocate along its axial direction; the rubber sealing head is installed on the outer wall of the transmission pipe and close to the other end of the transmission pipe. The hydraulic pump station is connected to the pulsation control console and the power unit in sequence through a high-pressure rubber hose to provide power for the power unit. The pulsation control console is used to control the start and stop of the power unit; the extraction device of the borehole that is in the extraction exhaustion period is removed, and the other end of the transmission pipe and the rubber sealing head are extended from the sealing pipe into the borehole, and the rubber sealing head is in close contact with the inner wall of the sealing pipe on all sides; a pressure gauge and a control valve are installed on the transmission pipe outside the borehole; the initial state of the control valve is closed.

[0007] B. Pulsating alternating fracture of coal body: The borehole is sealed for a period of time, and the gas pressure in the borehole is observed by a pressure gauge. If the pressure is less than 1.0MPa, one end of the transmission pipe is connected to the underground compressed air system, and the control valve is opened to inject gas into the borehole until the gas pressure in the borehole reaches 1.0MPa, then the control valve is closed and the connection with the underground compressed air system is disconnected; the power device is started through the pulsating control console, so that the power device drives the transmission pipe and the rubber sealing head to move a certain distance into the borehole and then reverse to the initial position, and repeats this reciprocating motion; during the movement, the rubber sealing head always slides and seals with the inner wall of the sealing pipe, so that the gas in the borehole is repeatedly compressed and restored with the movement of the rubber sealing head, and the alternating gas pressure generated in the borehole impacts and fractures the coal body, thereby increasing the permeability of the coal body. At the same time, the action of the alternating gas can increase the driving force of coal seam gas flow and promote the desorption of gas in the pores into the borehole.

[0008] C. Gas extraction: After completing step B, stop the power device, seal the borehole for a period of time, then connect one end of the transmission pipe to the underground gas extraction pipeline, and open the control valve to extract the gas.

[0009] D. Coal seam gas extraction meets the standard: when the pure flow rate of gas extraction is less than 0.001m 3 / min, close the control valve, and repeat steps A to C for continuous gas extraction until the coal seam gas extraction meets the standard.

[0010] Furthermore, the enhanced extraction system also includes an auxiliary positioner placed on the bracket, and the transmission pipe passes through the middle of the auxiliary positioner. The auxiliary positioner is used to limit the radial position of the transmission pipe when it reciprocates, so as to keep the transmission pipe moving along its axial direction.

[0011] Furthermore, the drilling sealing time in steps B and C is 48 hours. This time can ensure that the drilling sealing achieves the desired effect.

[0012] Furthermore, in step B, the frequency of the reciprocating motion of the transmission pipe is 0.015-0.025 Hz, and the reciprocating motion time is 6-8 hours. The above reciprocating motion parameters can ensure the effect of pulsating alternating fracture of coal.

[0013] Furthermore, the unidirectional moving distance of the transmission tube in the reciprocating motion in step B is 1 to 1.5 m. This distance range can not only ensure the effect of compressing and pressurizing the gas in the borehole, but also facilitate the reciprocating motion.

[0014] Compared with the prior art, the present invention fully utilizes the desorbed gas in the borehole to realize the self-pressurization of the borehole by sealing the borehole, and uses gas injection to supplement the pressure in the borehole to reach the required value. Then, through the reciprocating motion of the transmission pipe and the rubber sealing head, self-pressurized airflow and extracted airflow alternately appear in the borehole, so that the cracks in the coal body around the borehole are repeatedly subjected to expansion and contraction (alternating stress), which makes it easier for the coal body to reach the fatigue limit and fracture, so that the cracks continue to expand and gradually develop into the deep, so that alternating air pressure pulsation is generated inside the borehole to alternately fracture the coal body, increase the coal The permeability of the body; at the same time, the reciprocating motion will drive the gas in the borehole to alternately compress and recover, thereby increasing the driving force for coal seam gas flow, that is, when the gas in the micropores is compressed in the borehole, the gas pressure in the borehole is higher than the gas pressure in the micropores, and the gas will flow into the micropores at this time. When the gas in the borehole recovers, the gas pressure in the borehole decreases, and the gas in the micropores will flow back into the borehole, thereby driving the gas in the micropores to flow into the borehole. This continues to reciprocate, thereby promoting the desorption of underpressure gas from micropores to the borehole during the exhaustion period. After completion, the borehole is gas-extracted. When the pure gas flow rate during the extraction process is reduced to a certain value, the above-mentioned pulsating alternating fracturing and desorption promotion process is repeated many times until the gas extraction of the coal seam meets the standard. The present invention integrates alternating pneumatic fracturing and gas displacement, and superimposes multiple effects such as "flow promotion" and "permeability enhancement" under the premise of simple construction and no need for large-scale equipment. It can enhance the gas extraction efficiency of the boreholes that have entered the exhaustion period, thereby facilitating the subsequent safe mining of the coal seam and having wide practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a construction schematic diagram of the present invention.

[0016] In the figure: 1. Coal seam; 2. Drill hole; 3. Sealing pipe; 4. Rubber sealing head; 5. Transmission pipe; 6. Auxiliary positioner; 7. Power unit; 8. Pressure gauge; 9. Control valve; 10. High-pressure hose; 11. Pulsation control console; 12. Hydraulic pump station; 13. Bracket. DETAILED DESCRIPTION

[0017] The present invention will be further described below.

[0018] like Figure 1 As shown, the specific steps of the present invention are:

[0019] A. Laying out the enhanced extraction system: The enhanced extraction system includes a bracket 13, a power device 7, a transmission pipe 5, a rubber sealing head 4, a hydraulic pump station 12 and a pulsation control console 11. The power device 7 is installed on the bracket 13. One end of the transmission pipe 5 passes through the power device 7. The power device 7 can drive the transmission pipe 5 to reciprocate along its axial direction. The rubber sealing head 4 is installed on the outer wall of the transmission pipe 5 and close to the other end of the transmission pipe 5. The hydraulic pump station 12 is connected to the pulsation control console 11 and the power device 7 in sequence through a high-pressure rubber hose 10 to provide power for the power device 7. The pulsation control console 11 is used to control the start and stop of the power device 7. The extraction device of the borehole that has been in the extraction exhaustion period is dismantled, and the other end of the transmission pipe 5 and the rubber sealing head 4 are extended from the sealing pipe 3 into the borehole 2, and the rubber sealing head 4 is in close contact with the inner wall of the sealing pipe 3 on all sides. The close contact between the two can resist 2-3MPa gas pressure without leakage. The transmission pipe 5 outside the borehole 2 is equipped with a pressure gauge 8 and a control valve 9; the initial state of the control valve 9 is closed.

[0020] B. Pulsating alternating fracture of coal body: The borehole is sealed for 48 hours, and the gas pressure in the borehole 2 is observed through the pressure gauge 8. If the pressure is less than 1.0MPa, one end of the transmission pipe 5 is connected to the underground compressed air system, and the control valve 9 is opened to inject gas into the borehole 2 until the gas pressure in the borehole 2 reaches 1.0MPa, and the control valve 9 is closed, and the connection with the underground compressed air system is disconnected; the power device 7 is started through the pulsating control console 11, so that the power device 7 drives the transmission pipe 5 and the rubber sealing head 4 to move a distance inside the borehole 2 and then reverse to the initial position, and the reciprocating motion is repeated; the frequency of the reciprocating motion of the transmission pipe 5 is 0.015-0.025Hz; the reciprocating motion time is 6-8h. The unidirectional moving distance of the transmission pipe 5 in each reciprocating motion is 1-1.5m. The above reciprocating motion parameters can ensure the effect of pulsating alternating fracture of coal body, and the moving distance range can not only ensure the effect of compressing and pressurizing the gas in the borehole 2, but also facilitate the realization of reciprocating motion. During the movement, the rubber sealing head 4 always slides and seals with the inner wall of the sealing tube 3, so that the gas in the borehole 2 is repeatedly compressed and restored with the movement of the rubber sealing head 4. The alternating gas pressure generated in the borehole 2 impacts and fractures the coal body, thereby increasing the permeability of the coal body. At the same time, the alternating gas action can increase the driving force for the gas flow in the coal seam 1 and promote the desorption of gas in the pores into the borehole 2.

[0021] C. Gas extraction: After step B is completed, the power device 7 is stopped, the borehole 2 is sealed for 48 hours, and then one end of the transmission pipe 5 is connected to the underground gas extraction pipeline, and the control valve 9 is opened to extract the gas.

[0022] D. Coal seam gas extraction meets the standard: when the pure flow rate of gas extraction is less than 0.001m 3 / min, close control valve 9, and repeat steps A to C for multiple times to continue gas extraction until the gas extraction of coal seam 1 meets the standard.

[0023] As an improvement of the present invention, the enhanced extraction system also includes an auxiliary positioner 6 placed on the bracket 13, and the transmission pipe 5 passes through the middle of the auxiliary positioner 6. The auxiliary positioner 6 is used to limit the radial position of the transmission pipe 5 when it reciprocates, so as to keep the transmission pipe 5 moving along its axial direction.

[0024] The above-mentioned power unit 7, transmission pipe 5, rubber sealing head 4, pressure gauge 8, control valve 9, auxiliary positioner 6, hydraulic pump station 12 and pulsation control console 11 are all existing equipment or components, which can be purchased directly on the market. This application does not improve the various equipment or components themselves, but only utilizes their corresponding functions.

[0025] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for enhancing the extraction of under-pressure gas during the exhaustion period by drilling, characterized in that: The specific steps are: A. Laying out the enhanced extraction system: The enhanced extraction system includes a bracket, a power device, a transmission pipe, a rubber sealing head, a hydraulic pump station and a pulsation control console. The power device is installed on the bracket, and one end of the transmission pipe passes through the power device. The power device can drive the transmission pipe to reciprocate along its axial direction; the rubber sealing head is installed on the outer wall of the transmission pipe and close to the other end of the transmission pipe. The hydraulic pump station is connected to the pulsation control console and the power device in sequence through a high-pressure rubber hose to provide power for the power device. The pulsation control console is used to control the start and stop of the power device; the extraction device of the borehole that is in the extraction exhaustion period is removed, and the other end of the transmission pipe and the rubber sealing head are extended from the sealing pipe into the borehole, and the rubber sealing head is in close contact with the inner wall of the sealing pipe; a pressure gauge and a control valve are installed on the transmission pipe outside the borehole; the initial state of the control valve is closed; B. Pulsating alternating fracture of coal body: The borehole is sealed for a period of time, and the gas pressure in the borehole is observed by a pressure gauge. If the pressure is less than 1.0MPa, one end of the transmission pipe is connected to the underground compressed air system, and the control valve is opened to inject gas into the borehole until the gas pressure in the borehole reaches 1.0MPa, then the control valve is closed and the connection with the underground compressed air system is disconnected; the power device is started through the pulsating control console, so that the power device drives the transmission pipe and the rubber sealing head to move a certain distance into the borehole and then reverse to the initial position, and the reciprocating motion is repeated in this way; during the movement, the rubber sealing head always slides and seals with the inner wall of the sealing pipe, so that the gas in the borehole is repeatedly compressed and restored with the movement of the rubber sealing head, and the alternating gas pressure generated in the borehole impacts and fractures the coal body, thereby increasing the permeability of the coal body. At the same time, the action of the alternating gas can increase the driving force of coal seam gas flow and promote the desorption of gas in the pores into the borehole; C. Gas extraction: After step B is completed, the power device is stopped, the borehole is sealed for a period of time, and then one end of the transmission pipe is connected to the underground gas extraction pipeline, and the control valve is opened to extract gas; D. Coal seam gas extraction meets the standard: when the pure flow rate of gas extraction is less than 0.001m 3 / min, close the control valve, and repeat steps A to C for continuous gas extraction until the coal seam gas extraction meets the standard.

2. The method for enhanced drilling and extraction of under-pressure gas in the depletion period according to claim 1 is characterized in that: The enhanced extraction system also includes an auxiliary positioner placed on the bracket, and the transmission pipe passes through the middle of the auxiliary positioner. The auxiliary positioner is used to limit the radial position of the transmission pipe when it reciprocates, so as to keep the transmission pipe moving along its axial direction.

3. The method for enhanced drilling and extraction of under-pressure gas in the depletion period according to claim 1 is characterized in that: The drilling sealing time in steps B and C is 48 hours.

4. The method for enhancing the extraction of under-pressure gas during the depletion period by drilling according to claim 1, characterized in that: The frequency of the reciprocating motion of the transmission tube in step B is 0.015-0.025 Hz; the reciprocating motion time is 6-8 hours.

5. The method for enhancing the extraction of under-pressure gas during the depletion period by drilling according to claim 1, characterized in that: In the step B, the unidirectional moving distance of the transmission tube in the reciprocating motion is 1 to 1.5 m.

Images