Usage of Geosat Altimeter Data for Offshore Oil Exploration off Bombay, India

Abstract

Geosat altimeter Exact Repeat Mission (ERM) data over a part of western offshore, India have been used to determine the prospecting geoid and the free‐air gravity anomaly. The sea surface height measured by satellite altimeter, when corrected for atmospheric propagation delays and other dynamic (time‐varying) oceanic variabilities, conforms to an equipotential surface known as the geoid. Geoidal anomalies contain information regarding mass distribution in the entire earth, including those due to bathymetric variations. The geoidal contribution due to the lithospheric zone (called prospecting geoid as it is obtained after removing the contributions for the deeper earth and the bathymetric variation) has been interpreted in terms of major geological structures significant to occurrences of petroleum. The prospecting geoidal anomalies can be used to compute the free‐air gravity anomaly which is useful for locating offshore hydrocarbon-bearing structures. Spectral analysis of the prospecting geoid and gravity anomaly field provide short, medium and long wavelength components which bring out density variations in the sedimentary layer of the earth's crust. One year of Geosat altimeter data have been processed over western offshore, India and a number of geological features e.g. Bombay high, Saurastra Platform, Ratnagiri basin etc. could be demarcated.