This regional stratigraphic study of the Silurian and Devonian strata in the northern Permian Basin focuses on the exploration and production potential of Wristen and Fusselman carbonate reservoirs that were deposited in the Tobosa Basin. This study represents approximately eight man-years of geological research. All or portions of 12 counties and approximately 13,000 square miles in western Texas and southeastern New Mexico are included in the study area.

   The database includes 3,200 wells with 11 regional markers and up to eight additional subregional markers or internal markers correlated. Ten regional cross sections were constructed across the study area, with formation-level contacts from the Ellenburger through the Woodford correlated. Mapping of internal picks within Siluro-Devonian carbonates permitted the interpretation of the development of this complex platform-dominated system.

     The scientific team described 88 cores comprising more than 8,500 total feet. The cores were systematically sampled for

petrographic analyses where permitted. Analyses of 550 thinsections are integrated into the core descriptions. The described cores comprise a complex suite of lithofacies deposited in diverse depositional environments, ranging from distal lower ramp to restricted supratidal. Stromatoporoid and coralline buildups are pervasive. The presence of repeated shoaling-upwards cycles terminating at subaerial exposure surfaces indicates the presence of multiple regional to subregional disconformities. Original depositional textures are often obscured by intense dolomitization and/or brecciation associated with the development of karst profiles.

     The six field studies contain development geology and engineering analyses including detailed geologic mapping and modeling, evaluations of drive mechanisms, reservoir characterization, reserve evaluations, and well performance reviews. Selected seismic lines provided by Permian Exploration Corp. illustrate structural styles and trap types of several of the fields.