--> ABSTRACT: Early Cambrian Relief Sandstone, Officer Basin, South Australia--An Example of Secondary Porosity Development, by Chris J. Gaugham, John K. Warren; #91003 (1990).
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ABSTRACT: Early Cambrian Relief Previous HitSandstoneNext Hit, Officer Basin, South Australia--An Example of Secondary Previous HitPorosityNext Hit Development

Chris J. Gaugham, John K. Warren

The Lower Cambrian Relief Previous HitSandstoneNext Hit has been drilled and cored at seven locations in the eastern Officer basin, central Australia. Core, well log, petrographic, and x-ray diffraction analyses have been used to subdivide the Relief Previous HitSandstoneNext Hit into stratigraphic units and individual depositional environments, and to determined controlling factors on known reservoir distribution and quality.

Interest in the Relief Previous HitSandstoneNext Hit as a potential economic oil-bearing Previous HitsandstoneNext Hit is supported by excellent reservoir quality (up to 26.5% Previous HitporosityNext Hit and 4839 md Previous HitpermeabilityNext Hit). Potential source rocks are found above, below and interfingering with the Relief Previous HitSandstoneNext Hit. There are several occurrences of live oil bleeding from vugs and fractures in a stratigraphically higher carbonate. Traces of oil in the Relief sands and the presence of live oil in relatively close proximity suggests that the Relief Previous HitSandstoneNext Hit could host an economic oil accumulation.

The majority of the Relief Previous HitSandstoneNext Hit was deposited in eolian or braided fluvial environments, with some alluvial fan sedimentation in the east, and tidal- to shallow-marine deposition in the west. Distribution of reservoir-quality sands is bimodal. In the east, Previous HitporosityNext Hit and Previous HitpermeabilityNext Hit for the most part are very poor to average. In the west, Previous HitporosityNext Hit and Previous HitpermeabilityNext Hit are generally good to excellent. The bulk of the economic Previous HitporosityNext Hit is secondary, a result of dissolution of cement and matrix, with minor Previous HitporosityNext Hit from leaching of grains. The lower reservoir quality in the east is due to diagenesis associated with compaction and authigenic illite. Grain packing with suturing and silica overgrowths have reduced primary Previous HitporosityNext Hit to noneconomic levels. Previous HitPermeabilityNext Hit has been reduced by thes processes and by the blocking of pore throats with authigenic illite. In the west, the Previous HitporosityNext Hit and Previous HitpermeabilityNext Hit are high and generally due to dissolution of clay cement and primary matrix. In some cases where the clay has undergone less dissolution, it remains as grain rims and still blocks pore throats. This significantly reduces Previous HitpermeabilityNext Hit although the Previous HitporosityTop may remain high.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990