Depositional and diagenetic controls on anomalously high porosity within a deeply buried CO2 storage reservoir-The Cambrian Mt. Simon Sandstone, Illinois Basin, USA

Similar to expected trends from other deep basin reservoirs, the COPL generally increases with depth in the Mt. Simon. The CEPL is significantly lower in the lower half of the Mt. Simon compared to the upper half of the Mt. Simon, indicating that higher porosity is attributed to having a lower volume of intergranular cement. Early episodes of diagenesis within the arkosic lower half of the Mt. Simon, such as clay infiltration and feldspar alteration, produced diagenetic grain-coating clays, which inhibited the development of quartz cements. Thus, these grain coatings assisted in porosity preservation within the Lower Mt. Simon by reducing CEPL. The upper half of the Mt. Simon is more heavily cemented as a result of changes in the depositional setting and thus changes in the lithology. Later, largely post-compaction feldspar dissolution further increased porosity in the Lower Mt. Simon Sandstone.