title: Geomechanical behavior of the reservoir and caprock system at the In Salah CO2 storage project.
abstract: Almost 4 million metric tons of CO2 were injected at the In Salah CO2 storage site between 2004 and 2011. Storage integrity at the site is provided by a 950-m-thick caprock that sits above the injection interval. This caprock consists of a number of low-permeability units that work together to limit vertical fluid migration. These are grouped into main caprock units, providing the primary seal, and lower caprock units, providing an additional buffer and some secondary storage capacity. Monitoring observations at the site indirectly suggest that pressure, and probably CO2, have migrated upward into the lower portion of the caprock. Although there are no indications that the overall storage integrity has been compromised, these observations raise interesting questions about the geomechanical behavior of the system. Several hypotheses have been put forward to explain the measured pressure, seismic, and surface deformation behavior. These include fault leakage, flow through preexisting fractures, and the possibility that injection pressures induced hydraulic fractures. This work evaluates these hypotheses in light of the available data. We suggest that the simplest and most likely explanation for the observations is that a portion of the lower caprock was hydrofractured, although interaction with preexisting fractures may have played a significant role. There are no indications, however, that the overall storage complex has been compromised, and several independent data sets demonstrate that CO2 is contained in the confinement zone.
authors.affiliation: Atmospheric, Earth, and Energy Division and jawhite@llnl.gov.
authors.forename: Joshua A
authors.initials: JA
authors.lastname: White
authors.affiliation: Atmospheric, Earth, and Energy Division and.
authors.forename: Laura
authors.initials: L
authors.lastname: Chiaramonte
authors.affiliation: Computational Engineering Division, Lawrence Livermore National Laboratory, Livermore, CA 94550.
authors.forename: Souheil
authors.initials: S
authors.lastname: Ezzedine
authors.affiliation: Atmospheric, Earth, and Energy Division and.
authors.forename: William
authors.initials: W
authors.lastname: Foxall
authors.affiliation: Atmospheric, Earth, and Energy Division and.
authors.forename: Yue
authors.initials: Y
authors.lastname: Hao
authors.affiliation: Atmospheric, Earth, and Energy Division and.
authors.forename: Abelardo
authors.initials: A
authors.lastname: Ramirez
authors.affiliation: Atmospheric, Earth, and Energy Division and.
authors.forename: Walt
authors.initials: W
authors.lastname: McNab
keywords: carbon sequestration; geomechanics