Coal mine methane re-imagined

Dr Guangyao Si’s cross-disciplinary research on coal mine methane capture and utilisation is helping mines improve safety, reduce greenhouse gas emissions and add value to their operations.Dr Guangyao Si

With a fundamental mission to develop safer, smarter and more sustainable mining technologies, Dr Guangyao Si is addressing a serious problem in the coal mining industry: the wasteful release of coal mine methane into the atmosphere.

In coal mining, there is often a considerable amount of methane trapped in the coal matrix. When the coal is mined the methane is disturbed and released into the underground mining environment where it becomes dangerous to mine workers. Compared with other mining hazards, methane-related accidents are responsible for the most casualties in the industry.

“Methane is a very dangerous, explosive gas, so it must be removed from the mine. But in most cases, there is no effective methane capture process, the purity of capture gas is low, and the majority of gas is ventilated straight into the environment,” Guangyao explains.

“It is estimated that coal mine methane is responsible for 8% of greenhouse gas emissions worldwide, so this is a big concern for global warming.”

According to Guangyao letting this gas escape into the atmosphere is not only terrible news for climate change, but a huge waste because methane is a valuable clean energy source.

“My research aims to develop efficient methods to help mines capture methane based on an improved understanding of mining geomechanics and gas flow patterns, so they can improve safety, reduce their environmental impact and add value to their operations,” he continues.

Although not common, Guangyao says methane capture is a proven activity and there are several sites in Australia that capture it for onsite power generation or, for the very pure methane, they also explore the possibility of gas pipeline injection to generate extra revenue.

One of the motivations behind his research is the changing nature of the industry and the increasing challenge for companies to recover deeper coal seams which have complex geology, high stresses and low permeability.

“These new deep mines often have a high gas content, so one of the techniques I’m investigating is how to pre-capture the gas before mining commences in the most cost-effective manner.”

The technique involves drilling long-distance boreholes into the coal seam and creating a negative pressure for gas drainage (similar to the wells in the oil and gas industry). The problem is that coal generally has very low permeability, so it’s difficult to extract the methane given the tight mine production schedule.

To address this, Guangyao is combining the strengths from mining and petroleum techniques to stimulate the coal reservoir, increase the permeability and make the gas flow faster.

“Our research priority is trying to optimise borehole designs to increase drainage efficiency. We need to understand where the gas flows, so we can capture the most gas with the fewest boreholes drilled,” he says.

In addition to developing practical solutions to address industry demands, Guangyao says he is also undertaking fundamental research. This includes revealing gas flow patterns around mine openings based on a solid understanding of mining geomechanics and fluid flow behaviours, which underpins the development of industry-focused technologies. 

“We are exploring questions like: ‘What are the stress and permeability distributions in the mining area?’ and ‘How does mining induce fracture and associated fluid flow behaviour around the mine openings?’” he continues.

Answering these questions will not only help improve coal mine methane capture, but also contribute to understanding the impact of mining on shallow aquifers. The new School of Minerals and Energy Resources Engineering provides a perfect platform for cross-disciplinary research, which is the key to tackling the challenge of fugitive gas emissions from the coal mining industry.

Guangyao says his research has already contributed to gas drainage and methane capture in coal mines in Eastern Europe and China and, having recently moved to Australia, he is looking for opportunities to work with the coal industry in New South Wales and Queensland, where there is considerable interest in improving safety and optimising methane drainage and capture systems.

More information
If you are interested in discussing a coal mine methane capture project with Guangyao, please contact him at: g.si@unsw.edu.au

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