Salt structures from inversion of residual gravity anomalies: application in Santos Basin, Brazil

Abstract

The Santos Basin, with an area of about 350.000 km² , is the largest salt basin of the South Atlantic, and due to its high economic hydrocarbon potential, it is a recurrent theme in scientific studies. The salt structures over the region present great importance for hydrocarbon accumulation and the geological/geophysical studies are performed from seismic reflection data, which requires time and efforts for acquisition and data processing. We identify salt structures using a new workflow based on inversion of residual gravity anomalies, where we use the Moho and basement depths obtained from gravity inversion, followed by the calculation of the gravity residual anomaly, assumed to be representative of the salt structures. This workflow is tested for a geological profile in the Santos Basin, and the results are evaluated along a 2D seismic section tied to well markers. The geometry of the stratified salt obtained from gravity inversion correlates with the seismic interpretation, with the advantage of estimating the entire salt package, including halite and stratified salt. With only seismic data, sometimes the stratified salt can be misinterpreted as sediments. The procedure can be applied to identify salt in sedimentary basins where seismic data is unavailable or of low quality.

KEYWORDS:
Santos basin; pre-salt; gravity anomalies; crustal structure; diapirism; inverse theory