Structural Analysis of a Core on Fractured Carbonate Reservoir, Brazil: Implications for Exploration and Reservoir Modeling*

Fractured Albian carbonate reservoirs, localized along eastern Brazilian marginal basins, have proven to contain important hydrocarbon reserves. The purpose of this paper is to discuss the structural analysis carried out on a selected oriented core, and its application for exploring and modeling fractured reservoirs. Attributes of fractures and faults measured on the core were correlated with depositional sequences, facies, and other petrophysical properties. We observe that the most deformed facies are mechanically soft, porous laminated mudstones. We suggest that this occurs due to flexural slip. We suggest that a clear, positive correlation between fracture density and some petrophysical parameters occurs when deformation results from wider wavelength structures in relation to thickness, like large folds. Nevertheless, this correlation is not so obvious when restricted fault-related deformation occurs. Like sub-seismic faults, flexural slip zones are virtually undetectable by seismic imaging, and may connect different structural levels in the reservoir. The detachment horizons may also represent a decouple between distinct mechanical layers, and hence a boundary between zones with distinct stress axis orientation. It could be expected that in this case, the fracture systems could have distinct hydraulic properties from the decouple surface