In-situ liquid-gas two-phase heat injection and permeability enhancement method for coal mine underground

By using a liquid-gas two-phase heat injection method, a three-dimensional slit network is formed by high-temperature and high-pressure aqueous solution and nitrogen gas. Combined with gas-water separation treatment, the permeability and safety problems of underground gas extraction in coal mines are solved, achieving efficient gas extraction and reducing the risk of spontaneous combustion of coal seams.

CN117722166BActive Publication Date: 2026-06-19CHINA COAL TECH & ENG GRP SHENYANG ENG CO
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
CHINA COAL TECH & ENG GRP SHENYANG ENG CO
Filing Date
2024-01-04
Publication Date
2026-06-19

AI Technical Summary

Technical Problem

Existing underground gas extraction technologies in coal mines suffer from the dangers of high-temperature operations, the risk of spontaneous combustion of coal seams, and poor permeability. Current heat injection methods have failed to effectively improve coal seam permeability and gas desorption efficiency.

Method used

The liquid-gas two-phase heat injection method is adopted. By alternately setting up heat injection boreholes and extraction boreholes, high-temperature and high-pressure aqueous solution and inhibitor are first injected to form a three-dimensional fracture network. Then, high-temperature and high-pressure nitrogen is injected for displacement. Combined with gas-liquid separation and slag removal treatment, coal seam permeability enhancement and gas extraction are achieved.

Benefits of technology

It effectively improves coal seam permeability and gas extraction efficiency, reduces the risk of high-temperature operations and the possibility of coal seam spontaneous combustion, and solves the safety and efficiency problems of coal mine gas extraction.

✦ Generated by Eureka AI based on patent content.

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Abstract

This invention relates to the field of coal mine gas extraction technology, specifically to an in-situ liquid-gas two-phase injection method for enhancing permeability and promoting decomposition in underground coal mines. In the initial stage of extraction, a high-temperature, high-pressure aqueous solution with a high specific heat capacity is injected into the injection borehole, rapidly increasing the coal seam temperature. The aqueous solution contains acid for enhancing coal seam permeability, an inhibitor for preventing spontaneous combustion of the coal seam, and a surface activator for improving the wettability of the coal seam. The acid reacts with carbonates within the coal seam to form new gas diffusion channels; the inhibitor reduces the oxidizing activity of the coal, thus reducing the possibility of spontaneous combustion; and the surface activator reduces the surface tension of the aqueous solution and improves its wettability to the coal, reducing the resistance of the coal seam pores to the high-temperature aqueous solution. In the later stage of extraction, high-temperature, high-pressure nitrogen is injected to replace and displace the gas in the coal seam. Nitrogen is an inert gas and will not react with the injected coal seam to prevent spontaneous combustion.
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