FIDUK, J. C., Department of Geological Sciences, The University of Texas at Austin, Austin, TX; and DOUGLAS S. HAMILTON, Bureau of Economic Geology, The University of Texas at Austin, Austin, TX

ABSTRACT: Identifying Potential Field Extensions by Integrated Reservoir Characterization and Seismic Analysis: Eocene Strata of Duval County, South Texas

Hydrocarbon potential of the middle Eocene Queen City Formation and the upper Eocene Jackson Group was investigated in Lundell (Queen City) and Seventy-Six West fields (Jackson Group, Cole sandstone), in northwestern Duval County. Although they are mature producing intervals, integration of detailed reservoir characterization with seismic data indicates that significant potential exists for additional commercial hydrocarbon accumulations within these strata.

High-amplitude "bright spot" anomalies were identified at Lundell field, and correlate directly to producing Queen City Sandstones. Time-based well logs from within the field and in adjacent nonproductive strata were correlated with the seismic data. Whereas SP log character indicated the presence of sandstone in both the producing and nonproducing wells, only wells thatcorrelated to the seismic "bright spots" demonstrated a response on the resistivity tool indicative of hydrocarbons. An untested fault block east of the field displays a similar seismic "bright spot" anomaly and provides potential for field extension at Lundell.

At Seventy-Six West field, reservoir geometry is highly complex, consisting of a mosaic of discontinuous strike-oriented barrier-beach ridges, channel facies, and lagoonal mudstones. High-amplitude seismic reflections correlated closely with the oil-productive barrier-beach ridge and channel sandstones. Moreover, the high-amplitude reflections diminish at the updip pinch-out of the barrier-beach ridge, and define the updip field limit. Potential for field extension exists to the southeast, where high-amplitude seismic reflections suggest the presence of another well-developed but untested barrier-beach ridge.

These results highlight the potential for field extensions at Lundell and Seventy-Six West, and similar studies using available seismic data over mature areas in South Texas could lead to further field extensions or possibly to new field discoveries.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.