Gas drainage method and equipment with alternative drainage

Abstract

Provided are a gas extraction method and device with alternating extraction and injection, adapted to increase the extraction radius of a gas extraction drilling well and improve the total gas extraction amount of the drilling well. The main extraction pipeline (6) in front and back of a gas pump (8) is connected to a bypass pipeline (9) in parallel via a front and a back three-way ball valves (10, 7); the main extraction pipeline (6) in front of the front three-way ball valve (10) is connected to a high-pressure gas storage tank (13); the back part of the high-pressure gas storage tank (13) is connected to a gas replenish pipeline (12) controlled by a gas replenish control ball valve (11); the gas replenish pipeline (12) is connected to the main extraction pipeline (6) between the back three-way ball valve (7) and the gas pump (8), connecting a gas extraction pipe in the gas extraction drilling well to the main extraction pipeline to extract the gas. During the operation of the gas pump (8), by controlling the states of the front and the back three-way ball valves (10, 7), the gas replenish control ball valve (11) and an outlet control ball valve (15), the extracted gas flow and the injected gas flow alternate in the gas extraction drilling well, and the coal mass fissures around the drilling well continuously expand and gradually deepen under the effect of an alternating stress, thus improving the total gas extraction amount of the drilling well.

Description

technical field [0001] The invention relates to a gas drainage method and equipment with alternating pumping and pressure, and is especially suitable for increasing the drainage radius of a gas drainage borehole and increasing the total amount of gas drainage of the borehole. Background technique [0002] Gas drainage is to use the negative pressure generated by the gas pump to extract the gas stored in the coal seam through the gas drainage borehole. After a long period of extraction, the pressure and content of coal seam gas can be greatly reduced, so gas extraction is the fundamental measure to prevent and control coal mine gas disasters. In order to eliminate the threat of gas and ensure the safe production of mines, extensive gas drainage projects have been carried out in outburst mines, high-gas mines and some low-gas mines in my country. [0003] After the drilling of gas drainage, the stress of the coal body in a certain range around it is released and deformed. Dur...

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Problems solved by technology

For example, when the hydraulic fracturing method is used, although the cracks in the coal seam are enlarged, the air permeability of the coal body is reduced after the water is saturated, and the flow of the desorbed gas cannot be accelerated. In addition, the coal body becomes muddy when it meets water, which can block the cracks Therefore, it cannot increase the gas extraction volume

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