Outcrop and subsurface geology applied to drilling, sweet spot and target zone detection of resource shales: the Woodford example

摘要

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.