Bubble Point Simulation of Reservoir Oil and Carbon Dioxide Mixtures

Abstract

Accurate knowledge of the multicomponent phase behavior of carbon dioxide ($\hbox {CO}_2$) with hydrocarbon fluids is needed in the design, operation and development of carbon dioxide-based enhanced oil recovery (EOR) techniques, in particular, understanding the phase behavior of $\hbox {CO}_2$ and hydrocarbon fluids system. In recent years, the possibility of sequestering $\hbox {CO}_2$ (a greenhouse gas) in underground (oil) reservoirs has been proposed. The feasibility will also be affected by the phase behavior of $\hbox {CO}_2$ in the presence of chemical species present in the reservoirs (Al-Marri in PVT, phase behavior and viscosity measurements and modeling of the ternary and binary systems of carbon dioxide $+$ heavy hydrocarbon (n-eicosane) $+$ light gas (ethane or propane), Ph.D. Thesis, University of Southern California, 2006). PVT viscosity and vapor–liquid equilibria are important in EOR process, reservoir simulations and process design. Phase behavior consists of two parts, in the first part the recombination process takes place by inserting the data of surface fluids into the PVT simulation to determine various fluid properties and especially the bubble point at reservoir temperature. In the second part, the swelling test is introduced by inserting the data of carbon dioxide (99.6% purity) as injection fluid into the recombined fluid to investigate the swelling factors. The modified Peng–Robinson equation of state was used for predicting saturation pressure. For fluid mixtures, the Van Der Waals mixing rules are commonly used. Results of the simulation were compared with the experimental data showing that the saturation pressure of the recombined fluid/$\hbox {CO}_2$ system was strongly affected by the concentration of carbon dioxide. Thus, this enhanced the oil recovery from heavy oil reservoirs.