REGIONAL CHEMOSTRATIGRAPHY AND MECHANICAL STRATIGRAPHY OF THE BARNETT SHALE, FORT WORTH BASIN, TEXAS

The Barnett Shale in the Fort Worth Basin continues to be an important unconventional resource play. Geochemical and geomechanical properties have become increasingly important in well correlations and completions in these unconventional plays. Furthermore, understanding of elemental composition of mudstones has resulted in the identification of chemofacies, which are not readily distinguishable through macroscopic core descriptions. Chemofacies identification can aid in stratigraphic correlations and interpretation of depositional environments. In addition, variations in geomechanical properties are important to determine stress state, wellbore stability, and complex hydraulic fracture stimulation needed to make an unconventional reservoir economic.

Here, we present several multi-well cross sections showing chemofacies variations and mechanical stratigraphy of the organic-rich Barnett Shale across the Fort Worth basin. These basin-wide correlations are primarily based on geochemical data derived from high-resolution ED-XRF analyses and mechanical data collected with a micro-rebound hammer. Correlations of chemostratigraphy and mechanical stratigraphy enhance our understanding of regional variations and trends in chemical composition and rock competence. Although quite variable, rock strength is controlled predominantly by clay content and secondarily by carbonate content in the rocks. Overall, results show basic chemostratigraphic zones that do not readily correlate to mechanical divisions, but reveal fundamental variations in the Barnett Shale across the Fort Worth Basin.