Transp Porous Med (2010) 85:743–756 DOI 10.1007/s11242-010-9589-5 Phase Behaviour, Fluid Properties and Recovery Efficiency of Immiscible and Miscible Condensate Displacements by SCCO 2 Injection: Experimental Investigation Abdullah Al-Abri · Robert Amin Received: 23 October 2009 / Accepted: 30 April 2010 / Published online: 21 May 2010 © Springer Science+Business Media B.V. 2010 Abstract This paper presents a quantitative investigation of the interfacial tension dependent relative permeability (IFT-DRP) and displacement efficiency of supercritical CO 2 injection into gas-condensate reservoirs. A high-pressure high-temperature experimental laboratory was established to simulate reservoir conditions and to perform relative perme- ability measurements on sandstone cores at a constant reservoir temperature of 95 ◦ C and displacement velocity of 10 cm/h. This investigation covers immiscible displacements (1100 and 2100 psi), near-miscible displacement (3000 psi) and miscible displacements (4500 and 5900 psi). The coreflooding results demonstrated that displacement pressure is a key factor governing the attainment of optimum sweep efficiency. The ultimate condensate recovery in- creased by almost threefold when CO 2 was injected at near-miscible conditions (i.e., 23.40% ultimate recovery at 1100 psi compared to 69.70% at 3000 psi). Miscible flooding was found to give the optimum condensate recovery (9% extra ultimate recovery compared to near-mis- cible injection). Besides improving the ultimate recovery, miscible floods provided better mobility ratios and delayed gas breakthrough (0.62 PV BT at 5900 psi compared to 0.21 PV BT at 1100 psi). In addition to the elimination of IFT forces in miscible displacements, favourable ratios of fluid properties and phase behaviour relationships between the SCCO 2 and condensate were believed to be the driving force for the improved recovery as they pro- vided a stabilising effect on the displacement front and stimulated swelling of the condensate volume. This paper incorporates the theoretical aspects of phase behaviour and fluid prop- erties that largely affect the microscopic displacement efficiency and serves as a practical guideline for operators to aid their project designs and enhance their recovery capabilities. Keywords Gas condensate reservoirs · SCCO 2 injection · Immiscible and miscible displacements · Relative permeability · Displacement efficiency A. Al-Abri (B ) · R. Amin Woodside Hydrocarbon Research Facility, Curtin University of Technology, Perth, WA, Australia e-mail: a.al-abri@postgrad.curtin.edu.au 123