PNNL

Abstract

Geologic carbon sequestration is the process of injecting carbon dioxide captured from an industrial source into the subsurface for long-term storage. An Area of Review (AoR) evaluation is one of the requirements for obtaining a Class VI permit under the Underground Injection Control Program of the U.S. Environmental Protection Agency. The Class VI Rule requires that multi-phase computational modeling be used to delineate of the Area of Review, based on the horizontal extent of the separate-phase CO2 plume. A new approach is presented to quantify the plume extent of CO2 based on the vertically integrated mass per area (VIMPA). The distribution of CO2 mass in a horizontal plane is described as VIMPA contour lines. The plume extent can be defined by either a contour line of a pre-defined VIMPA value or a contour line within which a certain percentage of CO2 mass is contained. The method was demonstrated by a hypothetical injection of CO2 into a deep saline aquifer. The results indicate that the VIMPA decreases with distance in an exponential manner and hence, most of the injected CO2 resides in a much smaller area near the injection wells. The VIMPA approach for determining the plume extent applies to all injection scenarios regardless of the spatial variability of the properties of the injection zone and allows for the calculation of the CO2 plume extent to be standardized for injection permit applications.