An estimate of carbon dioxide storage capacity in the Upper Cambrian basal sandstone of the Midwest region

Abstract

Porosity values collected from core analyses and geophysical logs from the Upper Cambrian Mount Simon Sandstone in the western part of the Midwest Regional Carbon Sequestration Partnership (MRCSP) region indicate a predictable decrease in porosity with depth. Using this relationship and the methodology of the Carbon Sequestration Atlas of the United States and Canada, we have estimated the potential geologic storage capacity of CO2 in this deep saline aquifer. The storage capacity is a function of the area being assessed, the porosity and gross thickness of the stratigraphic unit, and the CO2 storage efficiency factor, which accounts for reservoir continuity, effective porosity, and the level of certainty of characterization. Our calculations include different scenarios for CO2 storage capacity, which is highly sensitive to changes in the subsurface properties. The porosity and thickness of the deep saline aquifer were used to calculate net porosity feet by using the regional trend of decreasing porosity (φ) with depth relationship (d, in feet) [φ (d) = 16.36 * e-0.00012*d; r2=0.41]. To evaluate the applicability of this relationship, we compared the theoretical values of net porosity with those obtained from geophysical logs. This approach generates solutions of the spatial distribution of net porosity feet that can be used to calculate storage volume potential at specific localities. The summation of these locality-specific calculations is in agreement with the value of 86 billion metric tons of CO2 estimated by the MRCSP for the total capacity of the Mount Simon Sandstone in the region.