DEEP GRAVITY INTERPRETATION BY STRIPPING

Abstract

“Old gravity data never die.” Review interpretations of gravity surveys can be made whenever warranted by new geological concepts, development information, or improved techniques. Important additional uses can be gained by extending the interpretation to deeper horizons by calculating and subtracting the gravity effects of overlying strata whose structure becomes known in detail from shallower development. This constitutes the new technique reported in this paper. An essential new factor which makes gravity “stripping” practicable is the advent of the gamma‐gamma density log which determines subsurface density relations in strata penetrated by development drilling. Combined stratigraphic and density information defines the mass anomalies in the upper strata. Subtracting the calculated shallower gravity influences improves the definition of the deeper gravity prospects. Applications of the method are illustrated by selected examples.