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The Structure, Deposition And Diagenesis Of Jurassic Sandstones In The Mount Horner Oil Field, Northern Perth Basin, Western Australia.

Newlands, Ian

Honours Degree, 1993

University of Adelaide

Abstract

The Mount Horner oil field is a rollover anticline in the northern Perth Basin. All oil production is from the Cattamarra Coal Measures Member of the Jurassic Cockleshell Gully Formation. A study of available seismic, log and core data was carried out to determine the depositiona1 environment and distribution of the L, K and F sandstones of the Cattamarra Coal Measures. The reservoir quality of the L Unit was investigated and compared to the F Unit.

The available seismic data was interpreted. Cores from the K, L and F units were logged. Core was tied to the well logs and the existing correlation of the K and L units was assessed. Thickness and percentage sandstone of the units was estimated from the gamma, sonic and density logs. Petrological analysis, X-ray Diffractometry (XRD) and Scanning Electron Microscopy (SEM) were performed on selected core plug samples.

It was found that the distribution of the L, K and F units was not affected by major fault movements. The F Unit is a widespread marine transgressive sand of uniform thickness. The L Unit is a widespread braided plain sandstone of uniform thickness which passes into the K Unit. The K Unit is divided into a lower, meandering, mixed load steam environment and an upper silty meandering steam environment. Sandstones in the K Unit are expected to have "shoestring" geometries. The best porosity and permeability in the L Unit occur in the coarse basal channel sandstones. The K Unit contains channels that may contain similar lithofacies.

Dickite cement is the main pore filling agent in the L Unit. There is effective porosity within the dickite. Oil ought to be recoverable from the coarse channel base sandstones in the L Unit.

The absence of anticipated chlorite from the diagenetic sequence suggests that chlorite occurs as a later stage replacement of early authigenic kaolin.

Australian School of Petroleum
THE UNIVERSITY OF ADELAIDE

SA 5005 AUSTRALIA

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