title: Interface pinning of immiscible gravity-exchange flows in porous media.
abstract: We study the gravity-exchange flow of two immiscible fluids in a porous medium and show that, in contrast with the miscible case, a portion of the initial interface remains pinned at all times. We elucidate, by means of micromodel experiments, the pore-level mechanism responsible for capillary pinning at the macroscale. We propose a sharp-interface gravity-current model that incorporates capillarity and quantitatively explains the experimental observations, including the x~t(1/2) spreading behavior at intermediate times and the fact that capillarity stops a finite-release current. Our theory and experiments suggest that capillary pinning is potentially an important, yet unexplored, trapping mechanism during CO(2) sequestration in deep saline aquifers.
authors.affiliation: Massachusetts Institute of Technology, 77 Massachusetts Ave, Building 48, Cambridge, Massachusetts, USA.
authors.forename: Benzhong
authors.initials: B
authors.lastname: Zhao
authors.forename: Christopher W
authors.initials: CW
authors.lastname: MacMinn
authors.forename: Michael L
authors.initials: ML
authors.lastname: Szulczewski
authors.forename: Jerome A
authors.initials: JA
authors.lastname: Neufeld
authors.forename: Herbert E
authors.initials: HE
authors.lastname: Huppert
authors.forename: Ruben
authors.initials: R
authors.lastname: Juanes
mesh_terms: D003198:Computer Simulation; D008956:Models, Chemical; D016062:Porosity; D012212:Rheology / Q000379:methods*; D012996:Solutions / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D012996:Solutions