Derivation of Basement Structure Map from Joint Interpretation of Potential Field and Seismic Data, Kwanza Basin, Angola

The Kwanza basin is part of the greater Aptian salt basin of West Africa. The recent discovery of giant fields in the sub-salt section of the conjugate Brazilian margin has focussed interest on the essentially unexplored deep water Kwanza basin. The presence of a functioning petroleum system is known from onshore wells. However, the deep water and complex geology associated with poor seismic imaging makes conventional exploration challenging. Due to the high density contrast between the sediments, salt and basement, the area is an ideal case for application of potential field methods in an integrated interpretation workflow. Modelling of interpreted seismic sections constrained by potential field data exploits the complementary nature of the datasets. This study uses a subset of the WesternGeco multi-client dataset covering much of the Angolan passive margin. Gravity models were constructed along 10 regional seismic lines. The initial models were based on the pre-existing seismic interpretation. The basement was modified to produce a model consistent with both the seismic and potential field data. A regional basement surface was derived utilizing the 2D models as a constraint. Significant changes to the seismic interpretation of salt were also required to ensure a consistent fit to the gravity data.