Abstract

Integrated study of well logs, cores, high resolution seismic data, and biostratigraphy has established the sequence framework of the Lower Pennsylvanian (Atokan)-Lower Permian (Wolfcampian) along the eastern margin of the Central Basin Platform in the Permian Basin. Sequence interpretation of high resolution (high fold) seismic data through this stratigraphic interval has revealed a complex evolution of platform margin architecture that has demonstrated overall progradation of at least 7 miles during Lower to Middle Wolfcampian time. Sequence stratigraphic study of the Wolfcamp interval has revealed details of the internal geometry and morphologic evolution of the contemporaneous platform margins.

The Wolfcamp stratigraphic section along the eastern Central Basin Platform consists of at least six third-order stratigraphic sequences. These sequences are characterized by thin transgressive systems tracts (TST) which overlie third-order sequence boundaries. Facies of the TST consist of mud-rich upward shoaling parasequences which are overlain by thicker highstand deposits consisting of grain-rich upward shoaling progradational parasequences. Lowstand systems tract deposits are not preserved on the platform proper.

Two generalized seismic facies assemblages are recognized in the Wolfcamp. Platform interior facies are characterized by high amplitude, laterally continuous parallel reflections. Platform margin facies consist of progradational oblique clinoforms and are characterized by discontinuous, low amplitude, low angle downlapping reflections. Platform interior facies are typically low energy, lime mud-rich facies with low reservoir potential. In contrast, grainstones are common in the platform margin facies providing widespread reservoir potential on the Central Basin Platform.

Fully integrated sequence stratigraphic study of low angle platform margins is critical to establishment of the third-order sequence stratigraphic framework. Recognition of mappable seismic facies within each sequence is essential to prediction of potential reservoir facies distribution, and stratigraphic traps within this framework. Moreover, stratigraphic trap plays can be developed or refined from sequence stratigraphic study. This interpretive method also assists description of complex reservoir geometries and internal heterogeneities which can contribute to significant reserve additions from within existing fields.