Wilcox Chronostratigraphic Framework: Update 2019
The Wilcox continues to be an active deepwater exploration play nearly 20 years after the first trend wells. Wilcox strata cover > 35,000 square miles in the northwest Gulf of Mexico, and > 90% of the trend is covered by allocthonous salt. A common chronostratigraphic framework is essential for regional correlation, especially when correlating key wells from field to field. The 2007 Wilcox chronostratigraphic model integrated published and unpublished onshore information with early seismic and wildcat well data (~20) to establish a physical framework made up of four seismic sequences. The lower three sequences, Wilcox (Wx) 4, Wx3, and Wx2 were defined as simple sequences, while Wx1 was defined as a composite sequence. The 2019 chronostratigraphic model incorporates new data and new ideas. In the last 12 years ~44 Wilcox wildcat wells were drilled, not including additional appraisal and development wells. The absolute time component of the new chart is updated to 2012 and 2016 time scales, and our use of high resolution nannofossil zonation allows a more precise tie to the new time scales. Rigorous palynology analyses resulted in identification of time-significant zones and events, including recognition of the Paleocene Eocene Thermal Maximum (PETM) in core and cuttings. Locating the PETM led to redefinition of the multiple sequences that comprise the Wx1 composite sequence in deepwater and redefinition of the onshore middle Wilcox. New well data led to recognition of the Wx2 as a composite sequence of greater duration than in previous interpretation. Wx3 and Wx4 sequences are unchanged aside from more precise age calibration. Early interpretations of lowstand depositional systems were calibrated to > 3,000’ of conventional core. Detailed examination of an additional 10,400’ of new core has expanded and validated earlier core-based interpretations. Industry interest in the deepwater Wilcox trend remains high. Significant discoveries continue to occur. The productive geographic area has expanded inboard from earlier wells at and near the outboard edge of the allocthonous salt canopy. Also, while pay zones in early trend wells were restricted to the Wx1 and Wx2, pay zones are also documented for the Wx3 and Wx4.
AAPG Datapages/Search and Discovery Article #90350 © 2019 AAPG Annual Convention and Exhibition, San Antonio, Texas, May 19-22, 2019