Abstract

The Ship Shoal 91 field is a subtle stratigraphic play which consists of a seismic amplitude whose updip limits do not fit structure. The amplitude corresponds to both gas and oil in the Upper Miocene sand. To attempt to predict pay sand distribution accurately, several geologic models were defined as development drilling progressed. The models utilized self-potential curve shape, core, and seismic character analyses, combined with computer modeling studies, engineering data, and scanning electron microscope studies. Four geologic models evolved, ranging from a structural trap formed by small faults, to a stratigraphic pinchout of the pay sand, to a channel sand, and finally to a complex channel sand, resulting in the current model: a faulted stratigraphic trap.The development strategy for determining well locations also evolved, due to unexpected well results. The initial strategy was based on the presence of seismic amplitudes, until it became apparent that the amplitude alone is not a reliable hydrocarbon indicator. The revised strategy is based on complex attribute analysis, including the amplitude envelope and the weighted frequency.The discovery and development of this stratigraphic field required thorough integration of geology, geophysics, and engineering disciplines. The Ship Shoal 91 field demonstrates that complex stratigraphic fields are still of exploration interest and can be successfully developed by using an integrated approach.

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