X-Ray Fluorescence Applications in Mudrock Characterization: Investigations into Middle Devonian Stratigraphy, Appalachian Basin, USA

Abstract

Mudrocks are characterized by nanometer-scale pore sizes and nano-darcy permeability, which plays a significant role in hydrocarbon flow during production. Resulting from these characteristics, mudrocks were exclusively considered a source rock, which charged overlying, more porous mediums. Hydraulic fracturing, a technology used to create artificial fractures to liberate hydrocarbons from the reservoir, enabled natural gas to be produced from mudrock reservoirs economically. Over the last fifteen years, this technology motivated research efforts to understand reservoir characteristics of mudrock. These investigations significantly improved our knowledge of mudrock systems, but have also highlighted key areas that are undeveloped and/or where conflicting hypotheses exist. Utilizing wave-dispersive X-ray fluorescence (XRF) and highresolution handheld energy-dispersive X-ray fluorescence (hhEDXRF) datasets collected from seven middle Devonian core throughout the Appalachian basin, this dissertation focuses on three areas of mudrock research: (1) development of mudrock calibrations to increase the analytical quality of hhEDXRF datasets, (2) investigation into the relationship between chemical composition of the host rock and natural fracture presence, and (3) assessment of the relationship between paleo-depositional conditions and organic carbon enrichment. This research indicates that lithology-specific calibrations significantly increase the analytical quality of hhEDXRF datasets, natural fractures preferential concentrate in zones of similar composition in a predictable manner, and an interplay of limited dilution and a robust anoxia-productivity feedback mechanism controlled organic carbon enrichment within middle Devonian mudrock of the Appalachian basin.

Regional variability of Caney Shale elemental composition, mineralogy, and petrophysical properties: Ardmore Basin, Oklahoma

“…The origin of quartz is often shown by the ratio of Si to a clay proxy, such as Si/Al. A positive correlation in concentration between Si and Al can indicate the presence of detrital quartz, while a decrease in Al paired with an increase in Si may indicate an autogenic influence (Pearce and Jarvis, 1992;Martin, 2019. Ca and Sr are commonly associated with a carbonate sources, which can originate from direct precipitation of sea water, calcareous algae, or the skeletons of marine organisms (Vine and Tourtelot, 1979;Tribovillard et al, 2006;Martin, 2019). Molybdenum (Mo) is a redox-sensitive trace element that is often found in organic-rich sediments, is fairly unreactive with seawater, and is associated with anoxic water conditions and a sulfide-rich (euxinic) water column (Emerson and Huested, 1991;Luther and Morse, 1999;Tribovillard et al, 2006;Dahl et al 2013).…”