Experimental Study on Coal Seam Gas Desorption Characteristics Caused by Moisture under Stepwise Depressurization

Author:

Li Xinjian123,Chen Xiangjun145,Wang Lin1,Shi Haoyang1,Yu Tongyong23

Affiliation:

1. State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Henan Polytechnic University, Jiaozuo 454003, China

2. State Key Laboratory of Gas Detecting, Preventing and Emergency Controlling, Chongqing 400037, China

3. China Coal Technology and Engineering Group, Chongqing Research Institute, Chongqing 400037, China

4. State Collaborative Innovation Center of Coal Work Safety and Clean-Efficiency Utilization, Henan Polytechnic University, Jiaozuo 454003, China

5. College of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, China

Abstract

Expansion energy is the main factor of coal and gas outbursts, and the gas desorption around the outburst hole is developed in variable pressure conditions. While studying the impact of moisture on gas desorption characteristics, atmospheric pressure desorption is usually used, but its characteristics under variable pressure conditions have not been thoroughly investigated. In this study, typical outburst coal samples with different water contents from the Jincheng mining area of China were selected as research objects, and the effects of water on gas displacement, desorption, desorption rate, and gas desorption index (K1) of drilling cuttings under step-by-step depressurization were analyzed by means of stepwise depressurization and atmospheric desorption experiments. The research conclusions suggest that (1) the amount of gas replacement, which augments rapidly during the inception, increases with the growth of water content under the experimental conditions, and then the rate decreases; (2) the gas desorption falls gradually at different depressurization stages when the humidity is constant, while the total desorption and the drop amplitude taper with the increasing water content; (3) the additional water enhances the desorption rate significantly only at the initial stage, but scarcely has an impact later on; and (4) the value of the drilling cuttings’ gas desorption index (K1) shows a downward trend with the developing humidity in each stage of stepwise depressurization desorption. We take humidity as a variable to simulate the desorption process of coal gas around the hole when coal and gas outbursts occur in the laboratory and study the influence of water on the desorption characteristics under desorption conditions of stepwise depressurization. This provides a reference for the purpose of studying the mechanism of coal and gas outbursts from the perspective of energy.

Funder

National Natural Science Foundation of China

Key R & D and Extension Projects of Henan Province

Publisher

MDPI AG

Subject

Energy (miscellaneous),Energy Engineering and Power Technology,Renewable Energy, Sustainability and the Environment,Electrical and Electronic Engineering,Control and Optimization,Engineering (miscellaneous),Building and Construction

Reference27 articles.

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2. Research progress of mining response and disaster prevention and control in deep coal mines;Yuan;J. China Coal Soc.,2021

3. A Novel In-Seam Borehole Discontinuous Hydraulic Flushing Technology in the Driving Face of Soft Coal Seams: Enhanced Gas Extraction Mechanism and Field Application;Zhang;Rock Mech. Rock Eng.,2022

4. Coal and Gas Outburst Control Using Uniform Hydraulic Fracturing by Destress Blasting and Water-Driven Gas Release;Yang;J. Nat. Gas Sci. Eng.,2020

5. Massive Hydraulic Fracturing to Control Gas Outbursts in Soft Coal Seams;Lyu;Rock Mech. Rock Eng.,2022

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