Impact of Fault Displacement on Syn-Extensional Carbonate Deposition and Excess Permeability

Abstract

Summary Evaluating footwall carbonate geometries in concert with fault displacement and the flexural isostatic response to fault displacement, i.e. footwall uplift, can help improve prediction of reservoir presence, facies distribution, and non-matrix permeability. Large-scale faulting can produce footwall highs that are exposed and eroded as fault displacement increases, forming beveled exposure surfaces that may promote development of non-matrix permeability by processes such as meteoric karsting. Structural-stratigraphic analysis focusing on the relationship between faulting, carbonate deposition, and changes in lake level was conducted at a field in the Santos basin to aide in understanding recent and upcoming well results as well as development optimization of existing pre-salt assets. We applied concepts relating fault displacement and lake level to footwall carbonate geometries, fundamental structural mapping and analysis, and forward isostatic modelling to the field. Accommodation changes at the field scale correspond to changes in footwall uplift through time along strike of the field. Zones of high fault displacement are associated with beveled highs in the footwall, which represent exposure surfaces and thus may be prone to meteoric karsting. Fault displacement and carbonate geometry mapping helps to reduce uncertainty in possible non-matrix permeability by reducing uncertainty in lateral variability of these exposure surfaces.