CO2 Storage Resource Assessment and 3-D Property Modeling of the Middle Cambrian Mt. Simon Sandstone in Illinois
The feasibility of large-scale carbon dioxide (CO2) sequestration depends on the presence of porous and permeable formations with adequate regional extent, combined with an impermeable seal to accommodate and confine a large volume of greenhouse gases. Understanding the petrophysical characteristics of the target formation, as well as the regional geologic framework (including structural features and depositional setting), is a prerequisite to identifying the geologic processes that will directly control the CO2 injectability and containment behavior of the storage system. The Cambrian-age Mt. Simon Sandstone has a widespread distribution across Illinois, with a thickness range of 670 meters (2200 feet) in the northern part of the state to less than 122 meters (400 feet) in the southern part. Carbon dioxide storage in the Mt. Simon has been successfully demonstrated on a pilot scale at the Illinois Basin–Decatur Project. Although the thickness and reservoir characteristics of the Mt. Simon Sandstone have been assessed locally, more rigorous delineation of the distribution of reservoir properties is essential to verify the architecture and behavior of the reservoir regionally. Determination of 3-D porosity and permeability distributions was carried out by the Illinois State Geological Survey under the U.S. Department of Energy-funded CarbonSAFE project as a means of evaluating the Mt. Simon’s suitability as a target to identify promising areas for future scaling-up of CO2 sequestration activities. The petrophysical log data of over 70 wells that either fully or partially penetrate the Mt. Simon were utilized to generate structure and thickness maps and delineate the spatial distribution of porosity and permeability of the formation across the state. In addition, structural features including major faults that affected the reservoir volume have been identified. Based on geophysical well logs, the Mt. Simon Sandstone can be divided into three distinct lithostratigraphic zones, including Lower, Middle and Upper portions. Results achieved from the 3-D models indicate that an arkosic interval of the Lower Mt. Simon has the greatest CO2 storage potential relative to the rest of the formation. This part of the Mt. Simon is dominated by fluvial-alluvial deposits. Additionally, the results indicate that the arkosic interval is discontinuous, and pinches out in the southern and western parts of the state. Notable structures and faults are present in the modeled area. The impact these features may have on regional CO2 storage is part of the ongoing study. The highest CO2 storage capacity in regard to thickness and petrophysical characteristics are assigned to the arkosic intervals observed in north-central and central Illinois with a thickness range of 137 to 182 meters (450 to 600 feet) and a porosity range of 10 to 27%.
AAPG Datapages/Search and Discovery Article #90373 © 2019 AAPG Eastern Section Meeting, Energy from the Heartland, Columbus, Ohio, October 12-16, 2019