Seventy-Six West field, in northwest Duval County, South Texas, produces from the uppermost Jackson Group at depths of 1300 to 1400 ft [396 to 426 m]. Reservoir geometry is highly complex, consisting of strike-oriented beach ridge, channel, and sand-poor lagoonal facies, which are modified by dip-oriented tidal-inlet fill and washover sands. Production trends mirror the beach ridge and channel facies but are also influenced by dip-oriented facies and by small normal faults. The reservoir is heterogeneous and has an estimated 6 MMBbl [9.5 × 105 stock-tank m3] of remaining mobile oil trapped in untapped compartments and poorly swept zones. Results of detailed reservoir characterization identify these compartments and provide targets for infill drilling. Results at Seventy-Six West field are applicable to nearly 300 similar South Texas fields.

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