Coupled Strata and Gas Behaviour in the Co-Extraction of Coal and Methane

Abstract

As shallow coal deposits amenable to conventional extraction methods are being exhausted, coal mining is increasingly carried out in a deeper and more challenging environment with, for example, increased coal seam gas content and reduced coal and strata permeability. These conditions increase risks in mine gas drainage performance and mining operations and, if not managed properly, can have significant negative impact on coal mining productivity and recovery, mine health and safety, mine gas emission and its environmental impact. Coal mine gas (methane in particular) has been a cause of major coal mine disasters, significant greenhouse gas emissions and a key limiting factor to coal productivity improvement. However, when captured and utilised, coal mine methane becomes a source of abundant clean fuel or energy. An integrated mine gas simulation system has been developed to predict strata conditions and methane gas emission during longwall mining. The system can be used to assist selection and planning of suitable mining, gas management and utilisation strategies for new and existing mines. Several key mine gas assessment processes, such as mine site gas and geotechnical characterisation, and fully coupled mechanical deformation – fluid flow computer simulation, have been integrated in the simulation system. The integrated simulation approach is described in this paper and examples of mine site application are presented.