--> ABSTRACT: Expanded Yegua: Excellent Example of Prolific Production from Extremely Laminated Sand and Shale Sequence, by Richard E. Hart, Steve Grayson, and John Benes; #91030 (2010)

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Expanded Yegua: Excellent Example of Prolific Production from Extremely Laminated Sand and Shale Sequence

Richard E. Hart, Steve Grayson, John Benes

The upper Eocene Yegua Formation expands dramatically across a regional flexure generally 12-15 km wide. During each of several postulated Yegua sea level drops, this flexure became a focal point for deltaic deposition of good to excellent reservoir-quality sands. From the western edge of the Houston salt dome basin to the San Marcos arch, this trend has yielded, since 1982, at least seven noteworthy discoveries: Toro Grande and Lost Bridge fields in Jackson County, and Black Owl, Shanghai, Shanghai East, El Campo, and Phase Four fields in Wharton County, Texas.

El Campo field in Wharton County, Texas, was discovered in December 1985 by Ladd Petroleum Corporation with the drilling of the Ladd Petroleum 1 Popp well. Mud logs acquired while drilling indicated that a very sandy reservoir, with encouraging quantities of natural gas and condensate, had been encountered. Subsequent open-hole logging generated more questions than answers about the prospective sand section. Additional open-hole logs (EPT/ML, SHDT) were run to identify what turned out to be an extremely laminated sand-shale sequence over 400 ft thick. Subsequent development drilling and the acquisition of a 120 ft whole core provided valuable data in analyzing this prolific, geopressured natural gas and condensate Yegua reservoir. Whole-core data, open-hole logs, and computer logs wer integrated to develop petro-physical evaluation procedures and to determine the environment of deposition. El Campo field is believed to represent an extremely thick, delta front slope to distal delta front facies.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.