title: Mechanisms for mechanical trapping of geologically sequestered carbon dioxide.
abstract: Carbon dioxide (CO2) sequestration in subsurface reservoirs is important for limiting atmospheric CO2concentrations. However, a complete physical picture able to predict the structure developing within the porous medium is lacking. We investigate theoretically reactive transport in the long-time evolution of carbon in the brine-rock environment. As CO2is injected into a brine-rock environment, a carbonate-rich region is created amid brine. Within the carbonate-rich region minerals dissolve and migrate from regions of high-to-low concentration, along with other dissolved carbonate species. This causes mineral precipitation at the interface between the two regions. We argue that precipitation in a small layer reduces diffusivity, and eventually causes mechanical trapping of the CO2. Consequently, only a small fraction of the CO2is converted to solid mineral; the remainder either dissolves in water or is trapped in its original form. We also study the case of a pure CO2bubble surrounded by brine and suggest a mechanism that may lead to a carbonate-encrusted bubble owing to structural diffusion.
authors: Lorenz Center, Department of Earth Atmospheric and Planetary Sciences , Massachusetts Institute of Technology , Cambridge, MA 02139, USA.
authors: Yossi
authors: Y
authors: Cohen
authors: Lorenz Center, Department of Earth Atmospheric and Planetary Sciences , Massachusetts Institute of Technology , Cambridge, MA 02139, USA.
authors: Daniel H
authors: DH
authors: Rothman
keywords: Grotthuss mechanism; carbon sequestration; invasion percolation; reactive transport model; self-sealing; structural diffusion