ABSTRACT: Geology of the Seventy-Six, West Field, Duval County, Texas

Diane Birdwell Hyatt

The Seventy-Six, West field in Duval County, Texas, is a significant example of the Jackson barrier-bar/strandplain shorezone System of South Texas with a complex heterogeneous reservoir. This field is a typical instance of a combination stratigraphic structural trap. The facies sequence reflects a mosaic of mud-rich marsh, beach-ridge plain, distributary channel and levee, lagoonal, and backbarrier environments. Compartments caused by these facies distinctions (undrained areas of recoverable reserves) are a prime objective; however, any improvement in production is a boon. The field has produced more than 4,600,000 barrels of oil since its discovery in 1954. In many older fields such as this, the mobile oil left in the reservoir can be one third or more of the original o l in place after economic "limits" are reached. The economics are widely variable between major operators and small independents as illustrated by this study. Reevaluation using a synergistic approach to a "completely developed" oil field has led to additional waterflooding, improved recovery through infill drilling, and economic water disposal in a mature oil and gas province.

AAPG Search and Discovery Article #90999©1990 GCAGS and Gulf Coast Section SEPM Meeting, Lafayette, Louisiana, October 17-19, 1990