Print this pageUse of 3-D Visualization Tools to Interpret Structure and Fracture Potential: Rosario Field, Maracaibo Basin, Venezuela
APOTRIA, TED G. and M. SCOTT WILKERSON
The Rosario Oil Field lies between the Perija Mountain front and Lake Maracaibo and produces from fractured Cretaceous carbonates and Tertiary clastics in a dominantly contractional setting. Structure was mapped and fracture potential assessed with two different interpretation processes. The conventional approach consisted of posting and hand contouring time structure maps, map digitization, depth conversion, and curvature calculation. The second method involved digitizing serial sections into GEOSEC{TM}, depth conversion, loading into one of several 3-D modeling tools, constructing surfaces, and automatic creation of structure and curvature maps on multiple-horizons. Both methods have pros and cons, but the latter provides superior geometric validation capability.
The Rosario structure is a Mid Miocene and younger detached fault-related fold which ramps through Cretaceous Cogollo and La Luna carbonates and flattens into an upper detachment at the base of the Upper Cretaceous Colon Shale. Fold geometry at different stratigraphic levels is strongly controlled by lithology. Stiff Cogollo and La Luna carbonates exhibit kink-style folding above the upper fault-bend. The weak Colon Shale decouples the faulted carbonates from the overlying Tertiary clastics which are smoothly folded. It is expected that fracture density increases in areas of more intense faulting. Seismic data suggest that faulting is enhanced in the area of the frontal ramp-oblique ramp intersection in the main thrust and along the forelimb where the hangingwall has passed through a ramp-flat fault-bend. The latter is also characterized by higher production rates probably associated with higher fracture density.