%0 Journal Article
%A Okwen, R.T.
%A Stewart, M.T.
%A Cunningham, J.A.
%D 2010
%T Analytical solution for estimating storage efficiency of geologic sequestration of CO_{2}
%G English
%B International Journal of Greenhouse Gas Control
%V 4
%N 1
%P 102
%J International Journal of Greenhouse Gas Control
%@ 1750-5836
%K Aquifers; Brines; Buoyancy; Carbon dioxide; Carbon sequestration; Computer programs; Data processing; Gas injection; Ground water; Mathematical models; Permeability; Porosity; Salinity; Simulation; Temperature; Saline aquifers; Storage capacity
%X During injection of carbon dioxide (CO_{2}) into deep saline aquifers, the available pore volume of the aquifer may be used inefficiently, thereby decreasing the effective capacity of the repository for CO_{2} storage. Storage efficiency is the fraction of the available pore space that is utilized for CO_{2} storage, or, in other words, it is the ratio between the volume of stored CO_{2} and the maximum available pore volume. In this note, we derive and present simple analytical expressions for estimating CO_{2} storage efficiency under the scenario of a constant-rate injection of CO_{2} into a confined, homogeneous, isotropic, saline aquifer. The expressions for storage efficiency are derived from models developed previously by other researchers describing the shape of the CO_{2}-brine interface. The storage efficiency of CO_{2} is found to depend on three dimensionless groups, namely: (1) the residual saturation of brine after displacement by CO_{2}; (2) the ratio of CO_{2} mobility to brine mobility; (3) a dimensionless group (which we call a "gravity factor") that quantifies the importance of CO_{2} buoyancy relative to CO_{2} injection rate. In the particular case of negligible residual brine saturation and negligible buoyancy effects, the storage efficiency is approximately equal to the ratio of the CO_{2} viscosity to the brine viscosity. Storage efficiency decreases as the gravity factor increases, because the buoyancy of the CO_{2} causes it to occupy a thin layer at the top of the confined formation, while leaving the lower part of the aquifer under-utilized. Estimates of storage efficiency from our simple analytical expressions are in reasonable agreement with values calculated from simulations performed with more complicated multi-phase-flow simulation software. Therefore, we suggest that the analytical expressions presented herein could be used as a simple and rapid tool to screen the technical or economic feasibility of a proposed CO_{2} injection scenario. 2009 Elsevier Ltd. All rights reserved.
%O Document Type: Journal Article
%O Bibliographic Level: Analytic
%O Source Note: International Journal of Greenhouse Gas Control, 4(1), p.102-107. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 1750-5836
%O Copyright Information: GeoRef, Copyright 2020 American Geosciences Institute.
%O GeoRef ID: 2020024159
%O DOI: 10.1016/j.ijggc.2009.11.002
%U http://hdl.handle.net/10.1016/j.ijggc.2009.11.002