Geochemical, Mineralogical, and Lithological Linkages in a Thick, Early Permian, Siliciclastic Succession, Midland Basin, West Texas, USA

Abstract

The latest Pennsylvanian and Early Permian (Wolfcamp, Dean, and Spraberry interval) of the Midland Basin, West Texas, represents a thick (often >1000 feet), mixed succession of shale, carbonate, and siltstone/sandstone lithologies that accumulated in a deep-water environment under variable hydrographic restriction. The succession is a prime target for petroleum companies working in the Permian Basin, of which the Midland Basin is an integral part. Because the succession is very thick and lithologically variable, it is critical to understand and predict the stratigraphic and lateral variability of the rocks. A highly-resolved (2-inch vertical) XRF-based chemostratigraphic study was undertaken on the Sun Oil D.E. Richards #1 drill core, recovered from Martin Co., Texas. While the core does not preserve a continuous record of the interval, it does contain long, uninterrupted sections of the upper Wolfcamp shale/siltstone through the lowermost Clearfork equivalent strata, just above the uppermost Spraberry operational unit. Major and trace element analyses were conducted on the slabbed core face using a Bruker Tracer IV-SD ED-XRF spectrometer. Elemental concentrations for 2567 sample intervals were calibrated from raw x-ray spectra using a set of reference materials developed from a broad range of mudrock lithologies (Rowe et al., 2012), and a subset of depth-matched sample powders (n = 229) was collected from the back of the core for mineralogical (XRD) and organic carbon analysis (LECO).