HR: 1340h
AN: H13F-1661    [Abstracts]
TI: Pressure Propagation and Brine Displacement in CO2 Storage Formations: The Role of Sealing Units
AU: Tsang, C
EM: cftsang@lbl.gov
AF: Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 90-1116, Berkeley, CA 94720, United States
AU: * Birkholzer, J T
EM: jtbirkholzer@lbl.gov
AF: Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 90-1116, Berkeley, CA 94720, United States
AU: Zhou, Q
EM: qzhou@lbl.gov
AF: Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 90-1116, Berkeley, CA 94720, United States
AB: If carbon dioxide capture and storage technologies are implemented on a large scale, enormous amounts of CO2 will be injected and sequestered underground, which means that large volumes of native brines will be displaced. Provided that there is hydraulic communication to shallow formations, such brine displacement from deep storage reservoirs may impact the hydrologic conditions in fresh-water aquifers, for example affecting groundwater table levels or discharge and recharge zones. In some cases, brines or brackish water may also be displaced into the capture zone of fresh-water wells. To explore the conditions important for pressure propagation and brine displacement, we conduct a simulation study investigating the multiphase processes resulting from CO2 injection into a large multi-layer geologic system comprising of a storage formation and the confining low- permeability sealing units. The pressure changes and transport patterns within the storage formation are evaluated as a function of time and distance from the injection point. We are particularly interested in the role of pressure mitigation and vertical brine flow through the upper and lower sealing units. Several sensitivity cases are therefore considered varying the permeability of the upper and lower sealing units within reasonable ranges. Our results suggest that seal conductivities on the order of 0.1 to 0.001 millidarcy may allow for considerable pressure attenuation in the storage formation by interlayer brine migration, while still providing an effective barrier to CO2 leakage (since they serve as capillary and permeability seals). It is thus important to fully understand the multi-layer characteristics of a storage site if the possible environmental impacts of CO2 injection on fresh-water aquifers are to be investigated. In addition to conducting detailed simulations of the multi-phase processes, we also investigate whether existing analytical solutions for well drawdown in leaky aquifers can provide first-order estimates of the expected large-scale pressure conditions during CO2 injection.
DE: 1807 Climate impacts
DE: 1829 Groundwater hydrology
SC: Hydrology [H]
MN: 2007 Fall Meeting