title: Measurement of CO2 diffusivity for carbon sequestration: a microfluidic approach for reservoir-specific analysis.
abstract: Predicting carbon dioxide (CO(2)) security and capacity in sequestration requires knowledge of CO(2) diffusion into reservoir fluids. In this paper we demonstrate a microfluidic based approach to measuring the mutual diffusion coefficient of carbon dioxide in water and brine. The approach enables formation of fresh CO(2)-liquid interfaces; the resulting diffusion is quantified by imaging fluorescence quenching of a pH-dependent dye, and subsequent analyses. This method was applied to study the effects of site-specific variables--CO(2) pressure and salinity levels--on the diffusion coefficient. In contrast to established, macro-scale pressure-volume-temperature cell methods that require large sample volumes and testing periods of hours/days, this approach requires only microliters of sample, provides results within minutes, and isolates diffusive mass transport from convective effects. The measured diffusion coefficient of CO(2) in water was constant (1.86 [± 0.26] × 10(-9) m(2)/s) over the range of pressures (5-50 bar) tested at 26 °C, in agreement with existing models. The effects of salinity were measured with solutions of 0-5 M NaCl, where the diffusion coefficient varied up to 3 times. These experimental data support existing theory and demonstrate the applicability of this method for reservoir-specific testing.
authors.affiliation: Mechanical and Industrial Engineering and Centre for Sustainable Energy, University of Toronto, 5 King's College Road, Toronto, ON, Canada M5S 3G8.
authors.forename: Andrew
authors.initials: A
authors.lastname: Sell
authors.forename: Hossein
authors.initials: H
authors.lastname: Fadaei
authors.forename: Myeongsub
authors.initials: M
authors.lastname: Kim
authors.forename: David
authors.initials: D
authors.lastname: Sinton
mesh_terms: D000393:Air Pollutants / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry*; D057965:Carbon Sequestration; D004058:Diffusion; D044085:Microfluidics; D054712:Salinity; D014867:Water / Q000737:chemistry
chemical_list: D000393:Air Pollutants; D014867:Water; D002245:Carbon Dioxide