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The Diagenesis Of Sandstone Reservoir Rocks In The Upper Roper Group Of The Proterozoic Mcarthur Basin, Northern Territory.

Loeliger, Marius

Honours Degree, 1988

University of Adelaide

Abstract

Proterozoic basins are generally not. considered to have great, petroleum prospectivity. Organic-rich sediments in the Late Proterozoic McArthur Basin in northern Australia have been recognised, and potential reservoir rocks identified by several workers (eg. Muir et al., 1980; Womer, 1986; Powell et al., 1987). The Moroak and Bessie Creek sandstones of the Upper Roper group are two such potential reservoir units evaluated in this study.

Analytical methods including core logging and wireline log interpretation and several laboratory techniques (Transmitted Light Microscopy, XRD, and SEM) were tools used. These were utilised to examine the clastic sediments with a view to determining the influence of both depositional environment and diagenesis on their reservoir potential.

Diagenesis within the Bessie Creek and Moroack sandstones has adversely affected primary porosity. The major cause of porosity destruction in the bassie Creek Sandstone is mechanical compaction and subsequent pressure solution. Diagenetic clays have reduced the volume of remaining pore space. The Moroak sandstone was seen to be well cemented by silica prior to compaction. Quartz overgrowths tend to strenghten the framework grains reducing the effects of compaction. Detrital and diagenetic clays are abundant and reduce porosity. Siderite was found to be a replacement mineral in the Moroak sandstone. Subsequent dissolution of this siderite has enhanced secondary porosity. Bitumen and relict oil from at least two phases of hydrocarbon emplacement was observed in both sandstones.

Australian School of Petroleum
THE UNIVERSITY OF ADELAIDE

SA 5005 AUSTRALIA

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