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Understanding Reservoir Complexity and Heterogeneity: Unique Aspects of Developing Core and Cuttings Based Chemostratigraphic & Lithologic Facies; Examples from Williston, Gulf Coast and Anadarko Basins


While many factors influence reservoir quality and facies, their spatial variability and controls on porosity, permeability, and brittleness are often enigmatic. One of the most important contributions in accessing reservoir quality and heterogeneity is to understand facies and facies-scale variability. Developing a quantitative approach to determining facies-scale heterogeneity in petroleum reservoirs is imperative and particularly difficult in mudrocks and mineralogically complex rocks. The fine-grained nature, lack of visible fabric and complex mineralogy make conventional interpretations difficult. In recent years scientists have been capable of producing more comprehensive interpretations through the implementation of specific instrumentation. Such methods include Energy Dispersive X ray Florescence (ED-XRF), capturing elemental composition, X ray diffraction (XRD), capturing mineralogical composition, Rock-Eval Pyrolysis, capturing thermal maturity, In situ hydrocarbons and TOC. These techniques integrated together with geologic and petrophysical models are commonly utilized in the evaluation of these complex rocks, producing chemostratigraphic and lithologic facies units. Utilizing XRF spectral data combined with specific methodology and sample preparation, geoscientists are capable of creating high resolution chemostratigraphic profiles of reservoir facies. Portable XRF aids in resolving micro scale facies and mineralogical variability efficiently at a low cost.