Bureau of Economic Geology

Targeted Secondary Recovery of Hydrocarbons from Barrier-Bar and Tidal-Channel Facies, Jackson Group, Prado Field, South Texas

Abstract
Low recovery efficiencies of sandstone reservoirs in the Jackson-Yegua Barrier/ Strandplain Sandstone play mark it as a large hydrocarbon resource target for advanced recovery techniques. Prado field, Jim Hogg County, South Texas, has produced more than 23 million barrels of oil and more than 32 billion cubic feet of gas from structural-stratigraphic traps in barrier/strandplain sandstones of the Eocene lower Jackson Group. Recovery efficiency is 34 percent from the primary oil reservoir and 72 percent from the primary gas reservoir. To evaluate depositional and structural controls on hydrocarbon accumulation in Prado field and to determine the field's potential for geologically targeted reexploration, we analyzed well logs and engineering data. Excellent prospects for successful field reexploration are based on reservoir pressures and indications of undrained reservoir compartments. Hydrocarbon entrapment at Prado field resulted from anticlinal nosing by differential compaction and updip pinch-out of barrier/strandplain sandstone. Relative base-level lowering caused forced regression that established lower Jackson shoreline sandstones in central Jim Hog County 15 mi downdip from their former position. Subsequent progradation caused the barrier/strandplain system to build seaward 1 to 2 mi. Reservoir sandstone bodies at Prado field comprise complex assemblages of barrier-bar, tidal-inlet-fill, back-barrier-bar, and shoreface facies. Two findings in this study have regional application to exploration in the Jackson-Yegua and Frio Barrier/Strandplain Sandstone plays: (1) a regionally significant forced regression has locally shifted shoreline deposits basinward, where they are typically encased in mudstone, and (2) tidal-inlet and transgressive-barrier facies are geologically complex and thus have high potential for undrained hydrocarbon-bearing compartments.
Authors
Steven J. Seni
Suk-Joo Choh
Citation

Seni, S. J., and Choh, S-J., 1994, Targeted Secondary Recovery of Hydrocarbons from Barrier-Bar and Tidal-Channel Facies, Jackson Group, Prado Field, South Texas: The University of Texas at Austin, Bureau of Economic Geology Geological Circular 9402D, 47 p.

ISSN
2475-3637
Number of figures
21
Number of pages
47
Publisher
The University of Texas at Austin, Bureau of Economic Geology
Series
Geological Circular
Year
1994