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A Depositional and Diagenetic History of the Barnett Shale (Mississippian) in the Oil Window, Northern Ft Worth Basin, Cooke County, Texas.

Tyler Ashley
Department of Geology: Texas Christian University, Ft. Worth Texas

The Barnett Shale (Mississippian) in the Fort Worth basin is one of the most prolific unconventional gas plays in North America. Successful economic wells in this low-permeability reservoir result from application of innovative drilling and completion techniques such as horizontal drilling and hydraulic fracturing. Until recently production has been mainly from areas of the basin that yield only dry gas. Declining gas prices have caused operators to shift exploration to areas of the basin that produce condensate, natural gas liquids and oil in addition to gas. The organic-rich shale serves as the source, reservoir, and seal for the hydrocarbons. The conventional wisdom wrongly considers deep-water marine shales such as the Barnett to be homogeneous and lack significant lithlogic variation. Understanding lithologic variation is an important key for locating hydrocarbon-rich areas (sweet spots) in the Barnett Shale and other shale gas reservoirs. Only a few detailed studies of Barnett Shale core are available in the public domain. Moreover, all these core analyses have been from core from wells in the gas-generating window of the play and there are no such publicly available analyses of a core from the oil- generating window of the play. A clear understanding of the depositional and diagenetic history of the Barnett Shale in the oil-generating portion of the basin is necessary for efficient production of oil and gas from the Barnett Shale in the northern Fort Worth basin. A detailed description of a continuous core from the oil window in the Fort Worth basin demonstrates the lithologic variation of the Barnett Shale both vertically and laterally. Lithologic descriptions and structural interpretations are based from whole core and thin section descriptions, geochemical data, well logs, FMI, and stratigraphic intervals identified by mapping.


AAPG Search and Discovery Article #90152©2012 AAPG Southwest Section Meeting, Fort Worth, Texas, 19-22 May 2012