WOLFE, J. E., and F. T. SOBOL, Amoco Production Company, Houston, TX

ABSTRACT: A Right-Lateral Structural Model for Poui Field, Offshore Trinidad, from 3-D Seismic Interpretation and Subsurface Well Control

A new wrench fault structural model is developed for Poui Field, in the Columbus Basin, offshore Trinidad. A strain ellipse for a right-lateral simple shear stress field is demonstrated from observed fault patterns on recent seismic mapping of deep hydrocarbon-bearing sands at Poui Field. The seismic interpretation is calibrated by 20 points of well control which penetrated the best, continuous, mappable reflector at these deep sand levels. Seismic cross-sections taken over the Poui structure, which are perpendicular to the structural axis of the feature, and constrained by well control, demonstrate geometries typical of wrench faulting observed along the Los Bajos fault complex, onshore Trinidad, and along the San Andreas wrench fault systems of southern California. Variable dip rate along the fault, flower structures with associated sag features, asymmetry of the structure, an extensional duplex, and a possible horsetail splay appear on the maps and cross-sections, and support the wrench fault model. Various pieces of subsurface information, observed in the Field from well control, support the wrench hypothesis: isolated, pressure separated compartments, abrupt facies changes across faults and hydrocarbon migration anomalies. Subsequent extensional faulting created an overprinting of rotated, normal faulting that followed fracture planes created by the right-lateral simple shear stress field. Regional mapping indicates that this wrench fault is a continuation of the right-lateral fault system mapped onshore Trinidad as the Marcel Main fault system.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.