An insight into the origin of midcontinent unconventionals using an integrated mineralogical and geochemical approach

• In Event: Geosciences: Oral session 1

Abstract

The Anadarko Basin located in the foreland of the Wichita Mountains in Oklahoma is one of the deepest and most prolific hydrocarbon basins in North America. Historically, the mudstones from this basin have been known as major hydrocarbon sources of the Midcontinent region. Yet, these mudstones remained relatively under-researched with respect to their provenance and clay diagenesis control over the reservoir rock properties. The focus of this study is set on the Pennsylvanian shale-rich intervals composed of alternating sequences of black shales, argillaceous sandstones and shaley interbedded sandstones. A 160 m long core with a maximum depth of 3000 m served as an excellent source of multiple mineralogical and chemical data on this prolific formation. The research aims to unravel the genesis and diagenetic evolution of the Anadarko Basin shales. Further on, it strives to understand the impact of paleo-environmental and diagenetic controls on the distribution of reservoir characteristics in the subsurface. To reach this objective several analytical techniques have been utilized including the X-ray diffraction to determine shale mineralogy and microbeam techniques needed to report on clay mineral morphologies and phase chemistry. Our preliminary data indicate detrital illite, quartz, and some minor feldspar as major shale minerals. Investigation of clay fraction highlighted the presence of mixed-layered illite-smectite along with ubiquitous chlorite and kaolinite. More work is however needed to elucidate on specific mineralogical variations that correspond to the changes in stratigraphy and sediment source mineralogy, and in particular how susceptible shale mineralogy is with respect to progressive diagenesis.

Authors

• Giovanni Zanoni, Texas Tech University

• Branimir Segvic, Texas Tech University