PETROPHYSICAL PROPERTIES OF THE WANAKAH FORMATION: EVALUATING SEAL EFFICACY OF TERRESTRIAL VERSUS MARINE SHALES

The Jurassic Wanakah Formation is an important fine-grained seal formation that overlies the porous and permeable, eolian Entrada Sandstone – a proposed carbon capture and sequestration reservoir in western Colorado. Petrophysical properties of the Wanakah Formation are investigated using two end member models, a terrestrial and a marine shale, to evaluate the efficacy of the models as seals for hydrocarbon and CO₂ reservoirs. Petrographic analysis, scanning electron microscope, QEMSCAN, x-ray diffraction, and whole rock analysis are used to evaluate the petrography, mineralogy, and geochemistry to determine lateral variability in terrestrial shales produced by features such as paleosols, bioturbation and diagenetic microenvironments. Petrophysical properties of the Wanakah Formation may be utilized as a guide to predict fluid/rock interactions (for both CO₂ and hydrocarbons) in similar terrestrial seal formations.