Outcrop and subsurface cores are sampled for a variety of low-cost rock analyses, including: Chemical (XRF) and mineralogical (XRF, XRD, petrography) composition and stratification, hardness (Leeb rebound hardness tester); microfabric, porosity and permeability (SEM); organic content (TOC, RockEval, biomarkers); fractures/ folds (visual observations); 2D and 3D seismic volumes, and biostratigraphy (if biota are present) This data set can then be combined to determine depositional environment, measure long-/short-distance lateral continuity of strata away from the wellbore, determine fracturability (brittle vs. ductile rock), categorize reservoir quality (porosity and permeability) and predict the potential for fractures to hold open or to close on proppant. These features provide important screening criteria for geoscientists and decision-makers. An example of the analysis, utility and application of these techniques is provided of the Woodford Formation, which is currently the 3rd most active hydrocarbon play in the U.S.
"Over the past three years, more than 100 oil and gas companies in North America ………. have filed for bankruptcy……" (Jenkins (SPE Reservoir Study Group lunch, Nov. 3, 2017). Although there are many non - technical reasons for this, Jenkins includes a lack of understanding of the shale reservoir and lack of quality/ quantity of properly-sampled rock and fluid data as contributors to less-than-desirable drilling and completion results. The Woodford Shale of Oklahoma stands as a very active play. At the writing of this paper, it ranks third place in U.S. states for active rig count, behind only the Permian and Eagle Ford (The Oklahoman, May 5, 2018, p. 4C).
A group of young geoscientists from the University of Oklahoma Institute of Reservoir Characterization have been studying the Woodford Shale for the past few years, producing 30+ graduate theses and dissertations across various parts of Oklahoma (Figure 1) and funded by a consortium of 32 companies, some of which have remained with the project for its duration, and others coming and going once their particular questions or issues have been addressed.