Energy and Environment Research; Vol. 4, No. 1; 2014 ISSN 1927-0569 E-ISSN 1927-0577 Published by Canadian Center of Science and Education 32 Evaluation of Asphaltene Stability During CO 2 Flooding at Different Miscible Conditions and Presence of Light Components Vahid Alipour Tabrizy 1 & Aly A. Hamouda 2 1 Department of Reserve Replacement, ASG PTC, Statoil ASA, Norway 2 Department of Petroleum Engineering, University of Stavanger, 4036 Stavanger, Norway Correspondence: Vahid Alipour Tabrizy, Department of Reserve Replacement, ASG PTC, Statoil ASA, Norway. Tel: 47-90-039-846. E-mail: vtab@statoil.com Received: December 12, 2013 Accepted: January 6, 2014 Online Published: January 10, 2014 doi:10.5539/eer.v4n1p32 URL: http://dx.doi.org/10.5539/eer.v4n1p32 Abstract The negative side effect of the flooding with CO 2 is asphaltene deposition; while little work was reported in the literature on asphaltene precipitation due to CO 2 flooding in presence of light components. The main objective in this paper is to address asphaltene precipitation for oil containing methane and propane due to CO 2 flooding at different miscibility conditions. Experimental measured asphaltene deposition due to miscible CO 2 injection is compared with corresponding values estimated by proposed model. It is shown that there is a critical concentration of CO 2 , where below it; solubility parameter of the liquid is enhanced, hence preventing asphaltene from depositing. The first objective of the paper is to address an approach which is based on solubility parameters/CO 2 fraction in the liquid to qualitatively assess stability/instability region for the asphaltene. The second objective is to quantitatively compare the predicted and experimental results. It is shown that the higher CO 2 flooding pressure and temperature, the more deposited asphaltene. It was also shown that a higher risk for asphaltene deposition in case of chalk cores than for sandstone cores. Keywords: miscible CO 2 flooding, asphaltene, solubility parameter, light components 1. Introduction Carbone dioxide flooding in Enhanced Oil Recovery (EOR) processes has been encouraging; however it may result to asphaltene deposition which it turns affect reservoir rock and fluid properties (Moritis, 2006; Chukwudeme & Hamouda, 2009; Hamouda et al., 2008; Idem & Ibrahim, 2002; Simon et al., 1978; De Boer et al., 1995; Burke et al., 1990; Haskett & Tartera, 1965). Haskett and Tartera (1965) reported that crude oils with low asphaltene percentage could experience asphaltene precipitation/deposition due to pressure reduction in early stage recovery, as well as reservoir fluid composition variations during enhanced recovery by gas/chemical injection. Different models have been reported in the literature to describe the behaviour of asphaltene deposition using different approaches. Hirschberg (1984) described a method based on solubility model using the Flory-Huggins theory with thermodynamic model considering temperature and pressure effects on asphaltene precipitation. Kawanaka et al. (1991) extended Hirschberg et al. (1984) approach considering asphaltene is a large nonhomogeneous polymers providing better fitting though increasing, the number of parameters to be adjusted. Thomas et al. (1992) derived an empirical correlation including the precipitated asphaltene as a multicomponent system using liquid-solid wax theory. Yang et al. (1992) described a modified Hirschberg solubility model and pointed that the oil phase should be modelled as a multicomponent system. Nghiem (1999) documented a thermodynamic solid model to see the dynamic description of asphaltene precipitation/deposited using a compositional simulator during miscible CO 2 injection. Paricaud et al. (2002) used statistical association fluid (SAFT) theory of the thermodynamics of large chain polymers used to model the onset of stability of polymer-colloid mixtures. Updated Statistical association fluid theory (SAFT) Equation of State derived by Chapman et al. (2004) was described providing the influence of polymer shape, Van der Waals interaction and aggregation of molecules. Kirangkrai et al. (2007) showed an empirical correlation between the solubility parameter limit and the molar volume of precipitants to observe the effect of dissolved gas on the onset solubility parameter of live oils. Gonzalez et al. (2008) demonstrated that CO 2 can be an inhibitor or a promoter of asphaltene precipitation depending on temperature, pressure, and composition studied. They have shown that at