Downhole coal bed methane extraction method and liquid nitrogen flowing frost cracking devices used in same

Abstract

The invention discloses a downhole coal bed methane extraction method and liquid nitrogen flowing frost cracking devices used in the same. The method includes the steps that 1, liquid nitrogen injection drilled holes and reinforced extraction drilled holes are alternately formed in a coal bed; 2, the fixed liquid nitrogen flowing frost cracking devices are inserted into the liquid nitrogen injection drilled holes; 3, liquid nitrogen is continuously injected into the drilled holes through a liquid nitrogen inlet, and the liquid nitrogen which flows back from a liquid nitrogen outlet is receivedto form a liquid nitrogen flowing loop; 4, the internal temperature of the liquid nitrogen injected into the drilled holes is increased through cable heating, and the liquid nitrogen is rapidly gasified; 5, mixed gas of coal bed methane and the nitrogen is extracted through the reinforced extraction drilled holes. The structure and the method have the advantages that the extraction cost of the coal bed methane is low and the extraction rate is high.

Description

technical field [0001] The invention relates to the technical field of coal bed gas extraction, in particular to an underground coal bed gas extraction method and a liquid nitrogen flow freezing cracking device used therein. Background technique [0002] As we all know, low-permeability and high-gassy coal seam groups generally exist in my country, which hinders the pre-extraction of coal bed methane. Now, in order to ensure the safe production of coal mines and the efficient extraction of coal bed methane, physical and chemical methods are usually used at home and abroad to carry out coal seam extraction. Permeability enhancement, the existing coal seam permeability enhancement technologies that are widely used mainly include: hydraulic fracturing, hydrochloric acid chemical method, hydraulic slotting method, deep hole pre-splitting blasting method, hydraulic punching and other methods. The extraction rate of coalbed methane, but also has shortcomings and deficiencies. Altho...

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Problems solved by technology

Although the hydraulic fracturing method has a good anti-permeability effect, the use of a large amount of water mixed with chemical substances in this technology will seriously pollute the water source, threatening the ecological environment and the health of local residents; High operation difficulty; deep hole blasting operation is more complex and prone to accidents th

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