GEOCHEMICAL CHARACTERIZATION OF UTICA SHALE PLAY USING XRF-BASED CHEMOSTRATIGRAPHY IN OHIO

The Upper Ordovician Utica shale play is one of the major natural gas producers in the eastern United States. It consists of the Utica shale, Point Pleasant Formation and the Trenton/Lexington Limestone. The Utica-Point Pleasant is a mixed siliciclastic-carbonate system, with its lithology varying significantly across the Appalachian Basin making it challenging to characterize. Using chemostratigraphic data will increase the understanding of the depositional and facies characteristics of the Utica shale and Point Pleasant Formation in Ohio.

This study examines the carbonate vs. siliciclastic deposition in the Utica shale play during the Middle to Late Ordovician Taconic Orogeny in eastern Ohio. X-ray florescence (XRF) combined with lithologic descriptions as well as x-ray diffraction (XRD) and total organic carbon (TOC) data performed by Core Laboratories, are used to investigate changes in the detrital and paleoproductivity distribution between the carbonate rich Lexington Limestone through to the argillaceous carbonate mudstones in the Utica shale. XRF was performed on core 6430 from Washington County (OH), focusing on elemental changes in concentrations with depth using selected major and trace elements. Elemental cross-plots were generated to establish relationships between elements to determine sediment source. Positive correlation of Si, Fe and K with Al indicate their association with terrigenous-sourced clay minerals. Aluminum concentrations of Lexington Limestone, Point Pleasant Formation and Utica shale samples range between 1.0 and 10.0 wt%, compared to average shale with a value of 8.8 wt% (Wedepohl 1971). In depth analysis regarding the existence of bottom water anoxia environment was not performed based on the depletion of redox sensitive trace metals.

Results of the study reveals nine chemofacies identified by Hierarchical Cluster Analysis (HCA), paleoproductivity and provenance changes that provide information on depositional history. Primary deposition is controlled by carbonates with storm waves influenced by tectonics and eustatic fluctuations responsible for siliciclastic input. XRF results will help create “stratigraphic timelines” as well as correlate the Utica shale Play across the entire state to provide insights into the depositional environment and identify productive zones of the Point Pleasant Formation as well as in the Utica shale. Next, Hetrogenous Rock Analysis (HRA) will identify clusters of well-log responses with similar characteristics to group into electrofacies.