Experimental study of coalbed methane thermal recovery

• Published in: Energy science & engineering 2020-05, Vol.8 (5), p.1857-1867
• Main Authors: Cao, Yuanhao, Chen, Wei, Yuan, Yinnan, Wang, Tengxi, Sun, Jiafeng, Cai, Yidong
• Format: Article
• Language: English
• Subjects: Adsorption; Anthracite; Carbon; Coal; Coalbed methane; Desorption; Experiments; Fourier transforms; gas desorption; Gas transport; Gases; Heat conductivity; Hydraulic fracturing; Internal pressure; Low temperature; Methane; Methods; Microfracture; Microstructure; Organic matter; Permeability; Pore size; Porosity; Porous materials; Recovery; Sensors; Studies; Sulfur; thermal decomposition; thermal treatment
• ISSN: 2050-0505; 2050-0505
• DOI: 10.1002/ese3.637

Extracting coalbed methane is challenging due to the strong gas adsorption capacity and low matrix permeability of the coalbed. Recently, thermal recovery methods have been tested to promote methane recovery. In this study, anthracite samples were heated to different temperatures to investigate the internal pressure variation and microstructure changes. It was found that higher temperature resulted in higher internal pressure. At low temperatures, the increase in the internal pressure was mainly due to gas desorption. At 500°C, thermal cracking gases provided the main contribution to the high internal pressures, as more gaseous products were generated at the higher temperature. In addition, the microstructure of coal significantly changed after combustion, including the increased pore volume, the increased specific surface area, and the generation of microfractures. These changes could potentially increase the porosity and permeability of coal. Thus, high‐temperature thermal treatments not only provided energy for gas desorption and organic matter decomposition but also improved conditions for gas transport. In order to study the effect of thermal treatment on coalbed methane recovery, cylindrical anthracite samples were heated to different temperatures to investigate the internal pressure variation and microstructure changes. Gas desorption and organic matter thermal cracking during high‐temperature thermal treatment both contributed to the internal pressure variation of coal. Thermal treatment also improved gas transport conditions, including the increase in porosity and generation of microfractures.