Cracking and permeability increasing device capable of pressurizing liquid nitrogen to dissolve coal body and permeability increasing experiment method

Abstract

The invention discloses a cracking and permeability increasing device capable of pressurizing liquid nitrogen to dissolve coal body containing gas, which comprises a heat preservation cylinder, wherein the center of the top wall of the heat preservation cylinder is downwards connected with an inner cylinder, and a gap is formed between the bottom end of the inner cylinder and the bottom wall of the heat preservation cylinder; the middle part of the inner cylinder is horizontally provided with a pressure-resistant metal mesh sheet which divides the upper part and lower part of the inner cylinder into a coal body cavity and a liquid inlet cavity; the middle part of the inner cylinder is provided with an isolation valve, the isolation valve is used for separating the inner cylinder, and the valve rod of the isolation valve extends out of the heat preservation cylinder in the horizontal direction; the top wall of the heat preservation cylinder, at the top end of the inner cylinder, is in threaded connection with an inner cylinder cover, and a threaded shaft body is arranged on the inner cylinder cover; the invention also discloses a permeability increasing experiment method which can be used to carry out liquid nitrogen leaching coal body experiments under the conditions of different gas adsorption pressures of the coal body, can better control the specific size of the liquid nitrogen leaching coal body, is suitable for repeatedly carrying out permeability increasing experiments on the coal body under different experiment conditions, is favorable for obtaining an optimal permeability increasing scheme and provides technical support for the exploitation and utilization of coal bed gas.

Description

technical field [0001] The invention relates to the field of coal bed gas exploitation, in particular to liquid nitrogen fracturing anti-permeability technology. Background technique [0002] Coalbed methane refers to the hydrocarbon gas that exists in coal seams with methane as the main component, mainly adsorbed on the surface of coal matrix particles, and partly free in coal pores or dissolved in coal seam water. It is an associated mineral resource of coal and belongs to very Standard natural gas is a clean, high-quality energy and chemical raw material that has risen internationally in the past ten or twenty years. The low permeability of coal seams seriously affects the extraction efficiency. Hydraulic fracturing currently has problems such as low flowback rate, short fractures, and environmental pollution. The use of new fracturing technology is the key to improving the fracturing effect of coal seams. Using low-temperature fluid to fracturing coal Reservoirs have th...

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Problems solved by technology

The low permeability of coal seams seriously affects the extraction efficiency. Hydraulic fracturing currently has problems such as low flowback rate, short fractures, and environmental pollution. The use of new fracturing technology is the key to improving the fracturing effect of coal seams. Using low-temperature fluid to fracturing coal Reservoirs have the advantages of increasing energy and drainage, and less damage to coal seams; it is an existing technology to conduct liquid nitrogen leached coal fracture development experiments under predetermined temperature conditions and coal reservoir pressures, but there is a lack of liquid nitrogen pressure for experiments. The existing equipment cannot realize the gas-containing coal liquid nitrogen cold soaking anti-permeability experiment, cannot realize the liquid nitrogen anti-permeability experiment under fixed or loading conditions, and cannot study the effect of liquid nitrogen infiltrated coal sample size on the coal sample under a certain pressure. The influence of crack development

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