Constraints for plate reconstruction using gravity data - implications for source and reservoir distribution in Brazilian and West African margin basins

Evaluation of tertiary sequences of West Africa and Brazil typically requires large budgets and staffs to identify drilling targets. Since these tertiary sedimentary systems extend for hundreds of kilometers (Proc. Petrol. Geol. Deepwater Depositional Syst. (2001) 2; Marine Petrol. Geol. (1990) 94-122). well beyond the limits of individual 3D and many 2D seismic surveys, additional information is necessary to interpret the most favourable locations for detailed exploration. Potential field data are powerful but often underutilized assets in building an exploration framework for reducing costs and interpretation risks. Although drilling locations are normally based on 3D seismic interpretations, reservoir distribution is controlled by features mappable with other methods such as potential fields. Other factors crucial to petroleum maturation. migration and trap formation relate to deep-seated controls that are well imaged (and sometimes exclusively imaged) on potential field data. Our observations from potential field data help identify reservoir distribution; source pod locations, source maturity, possible migration pathways: and potential traps. This paper illustrates the power of combining both regional and basinal scale interpretations based primarily on gravity analyses with extensive knowledge of the underlying geology. We review data sets and methods employed and describe results of a regional overview based on special plate-tectonic reconstructions of the South Atlantic. Examples from basin-scale work offshore West Africa and Brazil are used to illustrate factors important to hydrocarbon exploration. We conclude with a look ahead to improvements in methodology and application. (C) 2003 Elsevier Ltd. All rights reserved.