Publication Name: New Petroleum Symposium 1993
Authors: Dennis Morton, Michelle Smyth and Neil Sherwood
Date Published: December 1993
Number of Pages: 30
Reference Type: Magazine Article
Abstract:
The Late Permian Back Creek Group and its age equivalents generally underlie Late Permian coal measures in all eastern Australian Permian basins. The Permian sequence has been a prolific gas and oil producer in central and eastern Australian sedimentary basins at many localities. In northern New South Wales and southern Queensland, the Back Creek Group is represented by a sequence of thick fluvio-deltaic clastics containing sandstone reservoirs with considerable porosities and permeabilities. In an adjacent area, west of the NewEngland High, the Back Creek Group is dominated by marine siltstones and shales. The hydrocarbon source potential of the Back Creek Group deposited in a variety of palaeodepositional environments was investigated using organic petrographic techniques, with special emphasis on the nearshore marine environment. Volumes of dispersed organic matter (DOM) in the sediments ranged from trace to 7 per cent; coal lenses and seams were
plentiful at some localities. Overall, vitrinite is the dominant maceral in DOM and coals. Sporinite is the most abundant type of liptinite, except for the nearshore marine coals where suberinite is dominant. The proportion of vitrinite in the organic matter increases in rocks deposited from proximal to distal environments. The source potential of the Back Creek Group was considered to be fair to good overall and highest in the area between Southwood-1 and Inglestone-1
The maturation level of the Back Creek Group not affected by intrusions ranges from early mature to late mature (vitrinite reflectance values from about 0.5%-1.15%) in the southern Bowen Basin. In general, maturity increases from south to north. The maturation of the southern part of the formation occurred prior to development of the minor structural deformation; the deeper burial and increased subsidence in the north has contributed to the
increased maturation.
Large anticlines are located in an area where good quality Back Creek Group reservoirs and mature oil prone source rocks occur combining to form a unique yet unexplored exploration play.