Abstract

Sediment gravity flows in deepwater environments are important stratigraphic traps in lithologically diverse reservoirs, generating multiple plays for hydrocarbon exploration. These highly heterogeneous deposits can be studied using chemostratigraphy and higher-order sequence stratigraphy. Studying these gravity flows along a carbonate platform’s slope can further expand the understanding of the stratigraphy filling adjacent basins. The application of elemental analyses can support identifying mineralogy that impacts reservoir quality, especially when conventional testing cannot be applied.

This study utilized five cores in the Wolfcamp Formation from the southeastern slope of the Central Basin Platform in northwest Crockett County, Texas. High-resolution chemostratigraphy was conducted using X–ray fluorescence along with total organic carbon, X–ray diffraction, and scanning electron microscopy at resolutions based on chemofacies defined by hierarchical clustering analyses. Interpretation of chemofacies mineralogy and organic matter, gravity flows, and sequence cycles was used to evaluate depositional conditions along the carbonate platform margin of the Wolfcamp Formation.

The combination of high-resolution geochemical analyses, hierarchial clustering analysis, and mineralogy helped indicate that the massive to laminated mudstone lithofacies of the Wolfcamp Formation in the study area can be divided into argillaceous/siliceous mudstone, mixed siliceous mudstone, clay-rich siliceous mudstone, and mixed carbonate mudstone. Chemostratigraphy identified new depositional processes in the study area, including hemiturbiditc plumes during gravity flow transformations. Mudstones associated with gravity flows along the slope are organically-rich (4.65% mean total organic carbon [TOC]) due to the preservation of organic matter from: (1) organic matter supply, (2) rapid burial, and (3) disoxic conditions.