Depth Relationships in Porosity and Permeability in the Mount Simon Sandstone (Basal Sand) of the Midwest Region: Applications for Carbon Sequestration

Abstract

Porosity and permeability values collected from core analyses in the Upper Cambrian Mount Simon sandstone indicate a predictable relationship with depth owing to diagenetic changes in the pore structure. This predictive relationship is useful for evaluating the geological carbon sequestration capacity in the Midwestern region. Porosity logs from wells in the study area provide additional sources of petrophysical data. The regional trend of decreasing porosity with depth is described by the equation: φ(d) = 16.36 * e-0.00012*d (r2=0.41), where φ equals porosity and d is depth in feet. The correlation between burial depth and porosity can help predict the petrophysical character of the Mount Simon sandstone in more deeply buried and largely undrilled portions of the basin. Understanding the relationship among porosity, permeability, and depth also provides information for use in numerical models that simulate supercritical carbon dioxide flow within the Mount Simon sandstone. The decrease of porosity and permeability with depth generally holds true on a basinwide scale. However, localized stratigraphic and spatial variations in sedimentary facies also affect reservoir quality. In some areas, we observed a reversal in the porosity/depth relationship. Careful documentation of the mineralogical and sedimentological characteristics of the reservoir are critical to the successful prediction of the petrophysical attributes of deep saline aquifer systems and how they perform at a given locality.