Unconventional Gas

The unconventional hydrocarbon potential of South Australian basins includes shale gas, tight gas and hydrocarbons from coal, via coal seam gas (CSG), in situ gasification and surface syngas processes on mined coal. Exploration for these new resources is at an early stage in the State, however significant potential exists and research by explorers and the Department of State Development to understand and evaluate new plays is progressing.

In a mature basin such as the Cooper major effort is being focused on these new plays in 2011-2012. Two vertical wells specifically drilled to test shale gas potential in the Cooper Basin, Encounter 1 and Holdfast 1, encountered gas saturated Permian successions, with Holdfast 1 flowing gas at up to 2 MMscf/d after a seven stage fracture stimulation. In addition Santos has announced gas flows from coal seam, Stuart Petroleum (now Senex) has published resource estimates for a shale gas play in the Allunga Trough and Mettika Embayment, AGL has tested the Winton CSG play, Strike is testing the shallowest Permian coals for CSG in the southern Cooper Basin, and Santos continues to exploit tight gas. Linc Energy has been exploring in situ gasification of coal in the Walloway Basin, and CSG and shale oil in the Arckaringa Basin.

Globally, there are different perceptions of the definition of unconventional gas systems. In the United States, earlier distinctions between conventional and unconventional resources were primarily based on economics; in the early to middle 1970s, sub-economic or marginally economic gas resources such as coalbed methane, shale gas, and tight (low-permeability) gas were considered by most exploration geologists as unconventional (Law and Curtis, 2002). However these gas systems are now economically viable resources in the United States, and some exploration companies no longer refer to them as unconventional. Aside from economic considerations, there is a fundamentally important geological distinction; conventional gas resources are buoyancy-driven deposits, occurring as discrete accumulations in structural and/or stratigraphic traps, whereas unconventional gas resources are generally non buoyancy-driven accumulations. They are regionally pervasive accumulations, most commonly independent of structure and stratigraphic traps (Law and Curtis, 2002).

Characteristics of the Gidgealpa Group Composite Resource Play in the Cooper Basin, South Australia  (.PDF - 9.5 MB)

AAPG 2012 - Shale Gas Posters

AAPG 2011 - Shale Gas Posters