A microwave heating removal method for coal seam water lock damage in surface coalbed methane extraction drilling

Abstract

The invention discloses a method for relieving a water blocking damage of a ground coal-bed methane extracting and drilling coal seam by microwave heating. The method comprises the steps that firstly, a microwave emitter is arranged on the ground near a coal-bed methane extracting borehole; a microwave generated from the ground is guided into the coal-bed methane extracting borehole by a waveguide tube; a microwave radiation opening including a microwave helix antenna is formed in the position of a target coal seam in the water blocking damage; an inner medium and an outer medium of the coal seam near the borehole are simultaneously heated by an electromagnetic radiation effect on a coal medium containing two-phase fluids of gas, water and the like in the target coal seam caused by a microwave field; moisture evaporation of the gas-containing coal seam in the water blocking damage is promoted; the water saturation of the coal seam is reduced; the osmotic volume of a gaseous phase in a coal seam hole is improved; the desorption and diffusion capabilities of the coal seam gas are restored or improved; meanwhile, matrix pores and cracks of the coal seam near the borehole are expanded by the selectivity characteristics of the microwave field on coal heating; and the gas permeability of the coal seam in the water blocking damage is restored or improved, so that the target of relieving the water blocking damage of the coal seam is reached.

Description

technical field [0001] The invention relates to a technology of hydraulic anti-permeability enhanced coal bed gas (coal bed gas) extraction, in particular to a method for removing coal seam water lock damage generated in the hydraulic anti-permeability process and improving the effect of coal seam gas drainage. Background technique [0002] Ground drilling and extraction of coalbed methane is the main way to prevent and control mine gas disasters, reduce greenhouse gas emissions in mining areas and develop coalbed methane resources. However, most coal seams in my country have the characteristics of low gas permeability, low gas pressure and low gas saturation, which makes the gas recovery rate of coal seams generally low. In order to promote low permeability coal seam gas drainage, hydraulic anti-permeability technology has been widely used. However, under the action of various hydraulic anti-permeability technologies, the external water body gradually invades the pores ins...

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Problems solved by technology

However, under the action of various hydraulic anti-permeability technologies, the external water body gradually invades the pores inside the coal seam matrix from the high-permeability fractures, pushes the original gas in the pore throats to the deep part of the coal seam, and forms a concave direction at the gas-water interface. The meniscus of the water phase forms capillary resistance; when the gas drainage negative pressure is not enough to overcome the additional capillary resistance, the gas will not be able to drive away the water slug and flow to the extraction well, thereby forming water lock damage and causing water in the coal seam With the increase of saturation, the desorption rate and permeability of coal seam gas decrease

Therefore, the phenomenon of water locking seriously restricts the development and application of hydraulic coal seam anti-permeability technology.

Moreover, as far as the research status at home and abroad is concerned, the existing research mainly focuses on the prevention of water lock damage in gas-containing coal seams, and there are few research reports on the methods of removing water lock damage in gas-containing coal seams

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