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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 miles on the edge of the platform. The North Ward Estes Field has produced over 388 MMBO (one-third of the trend's cumulative production) from more than 3300 wells since its discovery in 1929. Production in the field is from back-reef lagoonal 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 68,000 correlation markers were selected and loaded into a computer database. Concurrently, 15 million curve feet of log data, 30,000 feet of core analysis data, and 125,000 feet of core lithology data were digitized. Core analyses and lithologies were depth-corrected. Logs were normalized using a 60-foot interval of laterally continuous anhydride dolomite. Core porosity data were cross-plotted verses 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 porosity-feet maps were then merged with fluid contact and water saturation data to calculate volumetries. Facies and permeability relationships and actual to apparent pay ratios were applied to determine effective hydrocarbon pore volume.

Computer generated net isopach maps of the sands display a north-south

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