THE APPLICATION OF GRAVITY INTERPRETATION TO AN INTRA CRATONIC BASIN

Abstract

I he Cooper Basin is a good example of a tectonically complex area, and this complexity is reflected in the gravity field. The gravity field caused by the sediments is distorted by the influence of a relatively strong regional field. Nevertheless along profiles over which gravity has been measured with appropriate care, the various components of the gravity field can be analysed and separated.

In the Cooper Basin the form of the regional field has been determined. As a result the structure of a major pre-Permian unconformity, which defines the base of the sediments mainly causing the gravity field anomaly, can be contoured. Other information related to some shallow structure is also derived.

The pertinent point emphasized by the Cooper Basin example is that over similarly complex areas gravity survey results can only be effectively used once the various components of the field are properly analysed. Scattered regional measurements may be of some value where the regional field varies little. In general, however, a few detailed profiles must also be available to upgrade gravity interpretation to the level where it is of immediate value in the early stages of oil exploration.

Specifications are therefore presented which detail gravity, elevation and positioning measurement accuracy as well as survey procedures necessary to detect geological structure at given depths.