Reservoir properties and CO2 storage capacity of the Rose Run Sandstone (Lower Ordovician, Knox Group) in the Central Appalachian Basin, northeast Kentucky

Abstract

The Lower Ordovician Rose Run Sandstone is a potential CO2storage reservoir in the Central Appalachian Basin in northeast Kentucky where the Kentucky Geological Survey’s 1 Hanson Aggregates research well penetrated it at drill depths of 1,000–1,009.5 m. Average Rose Run porosity and permeability from core plugs are 9.1% and 44.6 mD, respectively.In situreservoir properties were determined by step-rate testing an 18.6-m interval bracketing the Rose Run. Pressure derivative analysis of wellbore falloff pressure suggests that the Rose Run shares properties of both dual-porosity and dual-permeability reservoirs, consistent with its mixed lithologies. The Rose Run pore pressure was 9.3 MPa/km, 1.1 MPa/km underpressured compared to the expected hydrostatic gradient of 10.4 MPa/km. Average porosity of the Rose Run, at the industry-standard 7% porosity cutoff for assessing CO2storage capacity, calculated from 27 wells in the surrounding region, was 11.6% and the average net reservoir thickness was 6.2 m. Geomechanical properties of the overlying Beekmantown Dolomite show that it would act as a reservoir confining interval during CO2injection. The estimated P50supercritical CO2storage volume is 77.2 kt/km2, yielding P50storage capacity of 165.7 Mt in the region. By itself, an average surface area of 12.9 km2would be required to store 1 Mt of supercritical CO2in the Rose Run, thus lacking the volume to act as a stand-alone CO2storage reservoir in this area. It could contribute to a stacked-reservoir storage project developed in the larger Knox section, however. CO2–brine relative permeability tests suggest that nearly half of any supercritical CO2injected into the Rose Run would be residually trapped, and another portion would be trapped by mineral precipitation. The Rose Run in the KGS 1 Hanson Aggregates well is very close to the subsurface CO2critical depth in the northeast Kentucky region and lacks an updip reservoir trap. How far and fast the mobile CO2migration might occur at this site remains for future research and reservoir modeling.