Abstract
The implications and influences of the structural model in hydrocarbon trapping and production have been normally overlooked in the Amistad gas field, located in the Gulf of Guayaquil, Ecuador. As a result of a recent study, crossing conjugate faults were recognized as the main structural style controlling the gas accumulation. These faults consist of normal faults with opposite dips and normally occur in extensional basins where no clear preferential dip direction exists.
The recognition and impact of crossing conjugate faults in Amistad field has been underestimated or not properly interpreted basically due to limitations in quality of the seismic data which leads to the simplification of seismic interpretation. Another important factor worth mentioning is that fault intersection areas are normally not properly resolved in seismic images, therefore leaving room for misinterpretations and misplacement of faults. These areas can also present permeability anisotropy normally increasing transmissibility parallel to the direction of fault intersection.
In Amistad field two main impacts of the interpreted crossing conjugate faults have been observed. The first one is the structural compartmentalization of the field with its impact on production. Secondly, the reduction of the effective reservoir thickness observed in wells inducing to incorrect stratigraphical and sedimentological interpretations of facies changes.
Several examples showing the conjugate fault system, the compartmentalization of the Amistad structure, and the thinning out of the reservoir in several wells will be analyzed and shown.
The recognition of this structural style and its impact will allow Petroamazonas EP to locate in an optimal manner additional infill wells, surface platforms, and the development of still undrilled structural compartments.
