Determination of the regional and residual gravity anomalies to reconstruct basin structures of the Cauvery Basin

Abstract

The measured gravity field of the Earth contains two main components of short wavelength residual anomalies and long wavelength regional anomalies. In the petroleum industry, the most important component is the residual anomalies which correlate with the shallow density variations in sedimentary basins. The regional anomalies are caused by deeper density contrasts in the lithospheric mantle and the Asthenosphere. The current study is focused to determine residual and regional gravity anomalies for understanding basin architecture of the Cauvery Basin. In this study, the basement of the Cauvery Basin was determined using two-way-travel time seismic data and well log data obtained from eight exploration wells. Depth data from selected 2D sections were used as input data for a Mathematica® program which developed based on the iterative algorithm to calculate the residual gravity anomaly caused by a 2D polygonal body having a density contrast with the surrounding. The difference of the calculated and the observed gravity was then used to obtain the regional gravity along the arbitrary survey lines. Results show that the regional gravity ranged from about -50 mGal to 70 mGal with having a relatively high gravity anomaly in the central part of the Cauvery Basin. According to the regional tectonic settings, the high gravity anomaly can indicate a crustal thinning process that occurred during the rifting phase of the basin. The residual gravity anomaly of the Cauvery Basin ranged from about -60 mGal to 20 mGal and it follows the horst and graben structures. In summary, several undiscovered sub-basins were identified related to the rifting of (i) East–West Gondwana (ca. 167 Ma, NE–SW trending structures) and (ii) the East India–Antarctica (ca. 137 Ma, NW–SE trending). Therefore, this study can be productively used for mapping the structural elements and architecture in terms of considering the most favorable locations for future hydrocarbon exploration in the Cauvery Basin.