Evaluating the regional geological characteristics of the St. Peter Sandstone and Everton Formation for CO2 storage in Southern Illinois: A case study on site-specific injection feasibility in Washington County, Illinois

This study provides a detailed investigation of CO₂ storage potential in the St. Peter Sandstone and Everton Formation in Southern Illinois, employing a comprehensive, multidisciplinary approach that integrates geological and petrophysical analysis, seismic evaluations, and reservoir modeling. The objective of this study is to thoroughly characterize the geological and petrophysical attributes of these formations, emphasizing the lithology, thickness, and spatial distribution of porosity and permeability. A regional geocellular model was developed to identify specific areas within the St. Peter Sandstone and Everton Formation with significant CO₂ storage potential. The parameters used to identify these areas include average thickness, porosity, permeability, and brine salinity. The evaluation of the petrophysical logs and core intervals indicate that the St. Peter Sandstone is predominantly characterized by its fine to medium, well-sorted pure quartz sandstone composition, which is notably devoid of clay minerals. Furthermore, the Everton Formation exists locally in southwestern and southern Illinois and has two distinct intervals: the upper dolomite and the lower fine to medium grained, well-sorted quartz sandstone intervals. The Everton sandstone interval in southwest Illinois has reservoir properties similar to the St. Peter Sandstone. Regional variation in porosity and permeability is evident, with high porosity values in the west-central region of Illinois diminishing gradually towards the southern parts of the state. A portion of the regional geocellular model was used as input to dynamic reservoir simulation of CO₂ injection via the Lively Grove 1 well in Washington County, Illinois. A 30-year injection phase and a 50-year post-injection phase were simulated. Dynamic reservoir simulations were performed to assess the long-term viability of securely storing CO₂ within the St. Peter Sandstone and Everton Formation. Preliminary simulation results indicate that over two million metric tonnes of CO₂ can be securely injected annually into the St. Peter Sandstone and Everton Formation via a single well, thereby underscoring the practical implications of the study's findings for effective CO₂ management. Significantly, the study identifies the west-central part of Illinois as a highly suitable location for CO₂ storage within these formations. This insight is instrumental for developing targeted CO₂ storage strategies in the Illinois Basin, contributing to broader carbon mitigation efforts worldwide. The research emphasizes the role of geological storage in lowering atmospheric CO₂ concentrations, marking a critical step forward in combating climate change. Moreover, it highlights the indispensable role of the St. Peter Sandstone and Everton Formation in advancing carbon storage techniques.