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a b s t r a c tWhile the majority of shale formations will serve as reservoir seals for stored anthropogenic carbon dioxide (CO 2 ), hydrocarbon-bearing shale formations may be potential geologic sinks after depletion through primary production. Here we present the United States-Department of Energy-National Energy Technology Laboratory (US-DOE-NETL) methodology for screening-level assessment of prospective CO 2 storage resources in shale using a volumetric equation. Volumetric resource estimates are produced from the bulk volume, porosity, and sorptivity of the shale and storage efficiency factors based on formationscale properties and petrophysical limitations on fluid transport. Prospective shale formations require: (1) prior hydrocarbon production using horizontal drilling and stimulation via staged, high-volume hydraulic fracturing, (2) depths sufficient to maintain CO 2 in a supercritical state, generally >800 m, and (3) an overlying seal. The US-DOE-NETL methodology accounts for storage of CO 2 in shale as a free fluid phase within fractures and matrix pores and as an sorbed phase on organic matter and clays. Uncertainties include but are not limited to poorly-constrained geologic variability in formation thickness, porosity, existing fluid content, organic richness, and mineralogy. Knowledge of how these parameters may be linked to depositional environments, facies, and diagenetic history of the shale will improve the understanding of pore-to-reservoir scale behavior, and provide improved estimates of prospective CO 2 storage.Published by Elsevier Ltd.

A cost-benefit analysis is presented to evaluate the economic feasibility of carbon dioxide (CO 2)enhanced oil recovery (EOR) in Ohio. Ohio-specific data is integrated with reservoir performance and economic models to define the analysis framework. The analysis is applied to two Ohio oil fields to illustrate how the methodology can be used to constrain project economics and profitability. The regression derived from the CO 2 break-even price calculated for a range of oil prices indicates that the change in the unit value of CO 2 for EOR is approximately four times the corresponding change in the unit value of oil. A similar correlation observed in other oil fields suggests differences in reservoir properties may not significantly alter the price elasticity of CO 2 relative to the prevailing oil price. The break-even correlation presented here represents a standalone metric that can be applied for project screening purposes to determine the price conditions at which CO 2 becomes a viable purchase for EOR and a marketable asset for power plants with capture technology.