Comparative core analysis from a Wolfcamp formation well ; a case study

The Permian Basin Wolfcamp shale formation is a prolific producer of oil and gas from horizontal wells. The formation is over 1000 feet thick in most areas and has multiple prospective completion targets. The Wolfcamp formation is also highly variable in mineralogy, total organic content (TOC), porosity and other key reservoir properties. For this project, a full diameter core of 246 feet length was obtained, and a multi-faceted core analysis program was conducted. The program included spectral gamma logging, dualenergy CT imaging, plug sample selection, geochemistry, traditional shale core analysis, and digital rock analysis. Digital rock data from plug sample was upscaled to the whole core scans and continuous vertical curves were computed for mineralogy, brittleness index, TOC, porosity, and permeability. Plug samples were taken from 34 depth locations selected to be representative of the key lithologies as indicated by the bulk density (RHOB) and photo-electric factor (PEF) computed from dual-energy CT imaging. Preserved plug samples were sent to three different labs for physical lab testing, geochemistry, and digital rock analysis. One objective of this project was to obtain key reservoir and completion quality data to aid in selecting an optimum horizontal landing zone and to quantify hydrocarbon in place. Another goal was to enable comparisons between physical lab and digital rock experiments. Using ion-milled SEM images and 3D FIB-SEM data, TOC, intergranular porosity, and porosity associated with organic matter (PAOM) were determined. Of particular interest was to understand the importance of PAOM and to explore the similarities and differences between SEM derived porosity and helium porosity from traditional physical lab test.