Please cite this article in press as: Khudaida, K.J., Das, D.B., A numerical study of capillary pressure–saturation relationship for supercritical carbon dioxide (CO 2 ) injection in deep saline aquifer. Chem. Eng. Res. Des. (2014), http://dx.doi.org/10.1016/j.cherd.2014.04.020 ARTICLE IN PRESS CHERD-1564; No. of Pages 14 chemical engineering research and design x x x ( 2 0 1 4 ) xxx–xxx Contents lists available at ScienceDirect Chemical Engineering Research and Design j ourna l h omepage: www.elsevier.com/locate/cherd A numerical study of capillary pressure–saturation relationship for supercritical carbon dioxide (CO 2 ) injection in deep saline aquifer Kamal Jawher Khudaida, Diganta Bhusan Das ∗ Department of Chemical Engineering, Loughborough University, Loughborough LE11 3TU, UK a b s t r a c t Carbon capture and sequestration (CCS) is expected to play a major role in reducing greenhouse gas in the atmo- sphere. It is applied using different methods including geological, oceanic and mineral sequestration. Geological sequestration refers to storing of CO 2 in underground geological formations including deep saline aquifers (DSAs). This process induces multiphase fluid flow and solute transport behaviour besides some geochemical reactions between the fluids and minerals in the geological formation. In this work, a series of numerical simulations are carried out to investigate the injection and transport behaviour of supercritical CO 2 in DSAs as a two-phase flow in porous media in addition to studying the influence of different parameters such as time scale, temperature, pressure, permeability and geochemical condition on the supercritical CO 2 injection in underground domains. In contrast to most works which are focussed on determining mass fraction of CO 2 , this paper focuses on determining CO 2 gas sat- uration (i.e., volume fraction) at various time scales, temperatures and pressure conditions taking into consideration the effects of porosity/permeability, heterogeneity and capillarity for CO 2 –water system. A series of numerical simu- lations is carried out to illustrate how the saturation, capillary pressure and the amount of dissolved CO 2 change with the change of injection process, hydrostatic pressure and geothermal gradient. For example, the obtained results are used to correlate how increase in the mean permeability of the geological formation allows greater injectivity and mobility of CO 2 which should lead to increase in CO 2 dissolution into the resident brine in the subsurface. © 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. Keywords: Two-phase flow; Capillary pressure; Porous media; Deep saline aquifer; CO 2 sequestration 1. Introduction Carbon sequestration is a technique for managing carbon dioxide (CO 2 ) that has been emitted into the atmosphere by various activities, e.g., combustion of carbon-based fuels. It is a relatively new concept that had been developed to address the problem of global warming, which is attributed to high lev- els of atmospheric CO 2 . In a more specific approach, geological sequestration aims to inject supercritical CO 2 into porous for- mations underground while attempting to prevent leakage of CO 2 to the surface again. This method can be applied to declin- ing oil fields, un-minable coal seams as well as deep saline aquifers (DSAs). Injecting CO 2 into DSAs is considered to be ∗ Corresponding author. Tel.: +44 1509222509. E-mail addresses: D.B.Das@lboro.ac.uk, dbd59@rediffmail.com (D.B. Das). one of the most feasible sequestration methods of CO 2 . From a fluid mechanics point of view, injecting supercritical CO 2 into geological formations can be treated as a two-phase flow in a porous medium (Tsang et al., 2008). Supercritical CO 2 is con- siderably denser than the gaseous CO 2 phase but has lower density and viscosity than the occupant brine in the porous space. As a result of the differences of fluid densities, super- critical CO 2 migrates buoyantly towards the upper confining layer. The preferred depths to inject CO 2 are greater than 800 m (Prevost et al., 2005) as they provide the required conditions above the critical points of CO 2 for it to stay in supercritical phase. This increases the storage capacity of the site because more CO 2 can be stored within a specific volume. http://dx.doi.org/10.1016/j.cherd.2014.04.020 0263-8762/© 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.