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

Alireza Salmachi, Mojtaba Rajabi, Carmine Wainman, Steven Mackie, Peter McCabe, Bronwyn Camac and Christopher Clarkson
Additional contact information
Alireza Salmachi: Australian School of Petroleum and Energy Resources, University of Adelaide, Adelaide, SA 5005, Australia
Mojtaba Rajabi: School of Earth and Environmental Sciences, University of Queensland, Brisbane, QLD 4072, Australia
Carmine Wainman: Australian School of Petroleum and Energy Resources, University of Adelaide, Adelaide, SA 5005, Australia
Steven Mackie: Australian School of Petroleum and Energy Resources, University of Adelaide, Adelaide, SA 5005, Australia
Peter McCabe: Australian School of Petroleum and Energy Resources, University of Adelaide, Adelaide, SA 5005, Australia
Bronwyn Camac: Santos Ltd., 60 Flinders Street, Adelaide, SA 5000, Australia
Christopher Clarkson: Department of Geoscience, University of Calgary, Calgary, AB T2N 1N4, Canada

Energies, 2021, vol. 14, issue 9, 1-37

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

Keywords: coal seam gas; coalbed methane; gas content; permeability; in situ stress; deep coal seams; geology (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View complete reference list from CitEc
Citations: View citations in EconPapers (5)

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