SHALLOW INJECTION OF CO2 INTO A SANDSTONE RESERVOIR WITH HIGH POTENTIAL FOR SEEPAGE FROM POINT-SOURCES AND CONSEQUENT MONITORING

Preliminary site characterization indicates that injection of CO₂ into a faulted shallow sandstone reservoir will likely result in seepage to the surface, enabling evaluation of multiple monitoring technologies. Most carbon storage site characterization studies have focused on how to prevent leaks; this study examined a setting where one can deliberately create leakage in order to better understand leakage pathways and test monitoring systems. The possible test area is located within the Rocky Mountain Oilfield Testing Center (RMOTC) in the Powder River Basin, Wyoming. RMOTC encompasses the Teapot Dome oil field, the last federally owned and operated oil field in the United States. Teapot Dome is an elongated, asymmetrical anticline with a north-northwest trending axis. The stratigraphy of Teapot Dome consists of marine sediments with coastal sandstones. The Upper Cretaceous Shannon Sandstone is approximately 120 feet thick and is an actively producing shoreface sand unit which lies roughly 500 feet below the surface at Teapot Dome. The Shannon Sandstone is of interest because of its high leak potential due to shallow depth, numerous known faults, and abundant active and plugged oil wells at the site. CO₂ would be injected as a gas because the reservoir temperature and pressure of the Shannon would not support CO₂ in the supercritical phase. CO₂ remaining in the gas phase is also likely to increase the desired effect of leakage. The estimated volume of CO₂ required to reach leak monitoring locations was calculated using methods presented in the 2008 Carbon Sequestration Atlas of the United States and Canada. These calculations provide an estimate of the volume of CO₂ needed to assure the plume reaches designated monitoring locations. The estimated volume of trucked CO₂ can be used in developing a rough cost estimate for the prospective project. Monitoring technologies used in completed and ongoing carbon storage projects were reviewed briefly and selected as possible monitoring methods for this project. Future work will focus on testing a range of monitoring technologies, some of which have already been studied at RMOTC.