In the past, the Yegua and Wilcox Formations, of Eocene age, have been major exploration objectives in the Upper Texas Gulf Coast. The Yegua has been a prolific producer and has received widespread investigation along established trends. It has been only within relatively recent times that attention has been given to the downdip potential, especially as concerns the basal sands in that formation.

The Wilcox has not received the same intense exploration in regard to complete penetration of the entire section. In detail the Wilcox is very difficult to correlate, and markers must be established to guide exploration. Marine wedges, or zones with source-bed connections, exist, and a tentative middle marker has been proposed to identify one such zone.

The configuration of the Wilcox and Yegua depositional basin is considered to be important for downdip exploration. Major regional tectonic features had an effect on deposition as did faults and structural movement contemporaneous with deposition. Dip and east-west sections indicate regional sedimentation changes.

The utilization of regional studies along with detailed local investigation helps to explain existing production. The same tools can be used as a guide for future exploration.

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