Younas Dadmohammadi
University of Oklahoma, USA
Title: Ultimate CO2 Storage Capacity of an Over-pressurized Aquifer
Biography
Biography: Younas Dadmohammadi
Abstract
This paper examines a systematic approach to determine ultimate CO2 storage capacity of two-dimensional (2D) aquifer model owing to capillary snap-off, gas compression and dissolution into water. In our previous paper, an application of fractional flow theory waspresented to evaluate CO2 storage capacity of an aquifer because of capillary snap-off and gas dissolution; we re-visit that solution and incorporate gas compression as the third mechanism by which CO2 is sequestered in geological formation. The gas compression is triggered when the injected gas reaches to the physical boundaries of aquifer; beyond that point, the aquifer would realize pressure build-up (over-pressurized). Using the method we developed earlier, we determine the maximum CO2 trapped in 2D models that are negatively affected by gravity override. The effect of gravity override is introduced through a multiplier that depends on the aquifer’s aspect ratio and the buoyancy number; the solution is in dimensionless form normalized by total aquifer pore volume. Next, we use that value and put it in an equation derived based on the volumetric balance of the aquifer’s pore space. We perform sensitivity analysis to investigate the contribution of various factors on the CO2storage capacity. However, we limit the maximum allowed pressure to the fracturing pressure/ rock failure beyond which elastic deformation is not observed. Our results suggest that doubling the average pressure of an aquifer would approximately increase the CO2 storage capacity by % 50. However, we do not observe CO2 storage capacity of an aquifer being more than % 2 of total pore volume.Generally, numerical simulations are used to assess the CO2 storage capacity of a geological formation and evaluate various trapping mechanisms.However, the simulations are complex and time-consuming and they require detailed inputs; whereas, the presented method requires limited inputs and provides fast results in agreement with the simulation that makes the method suitable tool to compare and screen the CO2 storage potential of various formations. In practice, the proposed method provides an efficient screening method to assess the CO2 storage capacity of over-pressurized aquifers and significantly reduces the simulation costs while providing an interesting insight.