Gravity inversion of the onshore potiguar basin basement relief: Simulating results associated with different exploratory phases

Abstract

Gravity inversion results aiming to estimate the crystalline basement relief of the onshore Potiguar Basin are presented. It is assumed that the density contrast between the sediments and the crystalline basement is constant and known. The sediments are approximated with vertical rectangular prisms whose thicknesses, representing the depths to crystalline basement, are the parameters to be estimated from the gravity inversion. In all cases, the inversion process was stabilized with smoothness constraint on the spatial variation of the basement relief. Besides the gravity data, we used information about the basement relief obtained from boreholes and from seismic interpretation. These data were combined in order to compose three different scenarios simulating different phases during the exploratory development of the basin. In the first scenario we used the gravity data only. In the second scenario we worked with two combinations, first we combined the gravity data with information from boreholes, and second, with the basement relief reference model that resulted from the seismic interpretation. Finally, in the third scenario, we used the gravity data, the information from the boreholes and the reference model obtained from the seismic interpretation. In all scenarios, we obtained reliable estimates for the basement relief. Concerning the discrepancies among the results, the estimates obtained with additional constraints (from boreholes and/or seismic interpretation) increased the overall resolution of the basement relief and the reliability of the absolute depth values. However, it is important to stress that the first scenario already yielded a reliable estimate to the basin relief. If one takes into account the huge difference both in financial cost and environmental impact associated with gravity and seismic surveys, respectively, as well as with borehole drilling, this result highlights the great importance of properly using the gravity data in the initial exploratory phase of the basin. © 2013 Sociedade Brasileira de Geofísica.