History, Geology, In Situ Stress Pattern, Gas Content and Permeability of Coal Seam Gas Basins in Australia: A Review

Coal seam gas (CSG), also known as coalbed methane (CBM), is an important source of supply to the liquefied natural (LNG) exporting facilities in eastern Australia and Australian domestic market. In late 2018, became largest exporter LNG world. 29% country’s nameplate capacity three east coast that are supplied primarily by coal gas. Six geological basins including Bowen, Sydney, Gunnedah, Surat, Cooper Gloucester host majority CSG resources Australia. The Bowen Surat contain estimated 40Tcf whereas other relatively minor accumulations. Basin South Australia, thick laterally extensive Permian deep seams (>2 km) currently underdeveloped resources. Since 2013, production exclusively from has been tested a single add-on fracture stimulation vertical well completions across Basin. rates reserves achieved since 2013 demonstrate robust statistical distribution (>130 hydraulic stages), mean which, economically viable. characteristics rank, thickness hydrogeology present-day stress pattern create favourable conditions for production. Detailed analyses high-resolution borehole image log data reveal there major perturbations maximum horizontal (SHmax) orientation, both spatially with depth basins, which critical geomechanical modelling. Within basin, significant variability content permeability may be observed depth. reasons such variabilities sealing overlying formations, measurement methods, thermal effects magmatic intrusions, structures regime. Field studies show enhance throughout depletion fields functional form versus reservoir pressure exponential, consistent observations North American fields.