Significance of carbon dioxide density estimates for basin-scale storage resource assessments

The geologic carbon dioxide (CO₂) storage resource size is a function of the density of CO₂ in the subsurface. The pressure and temperature of the storage reservoir at depth affect the CO₂ density. Therefore, knowing these subsurface conditions allows for improved resource estimates of potential geologic CO₂ storage capacity. In 2012, the U.S. Geological Survey (USGS) completed an assessment of geologic CO₂ storage resources for large sedimentary basins in onshore and State waters areas of the U.S. Evaluating the subsurface conditions and CO₂ density in these basins was integral to the assessment. To better understand these conditions, investigations of pressure and temperature gradients, typically derived from borehole data and analog studies, were assembled at the basin scale. Based on the USGS assessment results and findings here, changes in subsurface pressure and temperature may yield density changes up to 40 percent, which may translate into significant changes in storage resource estimates.