--> ABSTRACT: Computer-Aided Geological Characterization of a Sandstone Reservoir, North Ward Estes Field, Ward and Winkler Counties, Texas, by A. S. Wylie, Jr., E. K. Davidsen, J. D. Gillespie, and R. S. Butler; #91030 (2010)

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Computer-Aided Geological Characterization of a Sandstone Reservoir, North Ward Estes Field, Ward and Winkler Counties, Texas

A. S. Wylie, Jr., E. K. Davidsen, J. D. Gillespie, R. S. Butler

The North Ward Estes field is located along the western edge of the Central Basin platform in Ward and Winkler Counties, Texas. The field is part of an upper Guadalupian productive trend that extends uninterrupted for 90 mi on the edge of the platform. The North Ward Estes field has produced over 350 million bbl of oil (one-third of the trend's cumulative production) from more than 3,000 wells since its discovery in 1929. Production in the field is from back-reef lagoonal siliciclastics (sandstones) of the Yates, Seven Rivers, and Queen Formations.

A correlation scheme was developed for the field based on laterally continuous key dolomites that bracket the productive sands and segment the reservoir into discrete mappable units. Applying this scheme, more than 60,000 correlation markers were selected and loaded into a computer database. Concurrently, 15 million curve feet of log data and 30,000 ft of core analysis data were digitized. Core analyses were depth corrected. Logs were normalized using a 60-ft interval of laterally continuous anhydritic dolomite. Core porosity data were cross plotted vs. bulk-density log values to develop equations (transforms) for derivation of porosity. Corrections for hole rugosity, overburden pressure, and lithologic complications were applied to refine the porosity transform. Structure and porosit -feet maps were then merged with fluid contact and water saturation data to calculate volumetrics.

Computer-generated net isopach maps of the sands display a north-south strike. The sands pinch out into an evaporite facies updip and a carbonate facies downdip. Dip-oriented cross sections illustrate a systematic migration of the sand "thicks" through time. The depositional model for the field indicates that the siliciclastics were deposited during an overall progradational, shallowing-upward Late Permian event that experienced minor transgressive and regressive cycles.

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