Abstract

Over the past 20 years, oil and gas companies have turned their attention to producing petroleum directly from organic-rich shale. Successful exploration, appraisal, and production strategies for source rocks critically depend on reliable identification of their organic components (kerogen, in particular) and their generation potential. There is mounting demand to evaluate organic richness in terms of quantity (i.e., total organic carbon) and quality (i.e., hydrogen index) from seismic data, which is usually the only source of information in the early development period of emerging shale plays. We have delineated major seismic lithofacies on the Alaska North Slope using elastic, seismic, and petrophysical properties. We performed a well-established quantitative seismic interpretation workflow to integrate geochemical data in the lithofacies definition. Rock-physics templates (RPTs) of seismic parameters, acoustic impedance, versus P-wave to S-wave velocity ratio (VP/VS), are constructed for each lithofacies to assess variations in pore fluid and lithology. We developed correlations between source rock properties (hydrogen index and total organic carbon) and petrophysical properties (bulk density, porosity, and sonic velocity ratio) of the major lithofacies. These correlations, together with facies-specific RPTs, can be used to predict organic richness and source rock properties away from drilled wells. The models are validated by training data from two regional wells to observe their applicability on the Alaska North Slope.

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