Eastern Section Meeting

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Comparing High Resolution Sedimentology and Elemental Analyses in the Union Springs Formation of New York


Subsurface mudrock characterization is of great importance in decision-making regarding management of hydrocarbon reservoirs. Handheld x-ray fluorescence (XRF) analysis on drillcore is a common technique for evaluating bulk chemical composition. Elemental abundance data from these analyses can be interpreted as indicative of specific paleodepositional or diagenetic regimes, and can be important for evaluating resource potential or predicting geomechanical properties. This presentation explores the validity of associations of geochemical signals with depositional facies, using elemental abundance data and petrographic microfacies data.

In the Union Springs Formation of the Marcellus shale, some environmental characteristics can be predicted to correlate with certain elemental parameters with a high degree of reliability. For example, a facies defined by lamination-displacive early diagenetic calcite concretions likely has a high calcium concentration. However, a high calcium concentration is not unique within the Union Springs, and the calcium abundance of this facies is similar to that of a facies with post-compaction calcite cementation. The two facies, which may possess significantly different textural and geomechanical properties, can be distinguished by comparing the full suite of elemental data.

We aim to determine the uniqueness of correspondence of a suite of chemical composition data to small-scale facies variations. Using handheld XRF, we probe the elemental abundances of 91 Union Springs samples, and examine how these data relate to compositional, faunal, and bedding-related variability, encapsulated by three broad lithofacies and sixteen narrowly-defined microfacies. Examining inter-facies and intra-facies variability, we can better clarify the predictive power of geochemical analysis in the Appalachian Basin.