title: Liquid CO2 displacement of water in a dual-permeability pore network micromodel.
abstract: Permeability contrasts exist in multilayer geological formations under consideration for carbon sequestration. To improve our understanding of heterogeneous pore-scale displacements, liquid CO(2) (LCO(2))-water displacement was evaluated in a pore network micromodel with two distinct permeability zones. Due to the low viscosity ratio (logM = -1.1), unstable displacement occurred at all injection rates over 2 orders of magnitude. LCO(2) displaced water only in the high permeability zone at low injection rates with the mechanism shifting from capillary fingering to viscous fingering with increasing flow rate. At high injection rates, LCO(2) displaced water in the low permeability zone with capillary fingering as the dominant mechanism. LCO(2) saturation (S(LCO2)) as a function of injection rate was quantified using fluorescent microscopy. In all experiments, more than 50% of LCO(2) resided in the active flowpaths, and this fraction increased as displacement transitioned from capillary to viscous fingering. A continuum-scale two-phase flow model with independently determined fluid and hydraulic parameters was used to predict S(LCO2) in the dual-permeability field. Agreement with the micromodel experiments was obtained for low injection rates. However, the numerical model does not account for the unstable viscous fingering processes observed experimentally at higher rates and hence overestimated S(LCO2).
authors.affiliation: Pacific Northwest National Laboratory, 902 Battelle Boulevard, PO Box 999, MSIN K8-96, Richland, Washington 99352, United States. Changyong.Zhang@pnnl.gov
authors.forename: Changyong
authors.initials: C
authors.lastname: Zhang
authors.forename: Mart
authors.initials: M
authors.lastname: Oostrom
authors.forename: Jay W
authors.initials: JW
authors.lastname: Grate
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Wietsma
authors.forename: Marvin G
authors.initials: MG
authors.lastname: Warner
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry*; D019015:Geologic Sediments / Q000737:chemistry*; D008962:Models, Theoretical; D010539:Permeability; D016062:Porosity; D014783:Viscosity; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D002245:Carbon Dioxide