| Abstract: | CO₂ injection has been used to improve oil recovery for several decades. In recent years, CO₂ injection has become even more attractive because of a dual effect; injection in the subsurface 1) allows reduction of CO₂ concentration in the atmosphere to reduce global warming, and 2) improves the oil recovery. In this study, the density effect from CO₂ dissolution in modeling of CO₂ injection is examined. A method to model the increase in oil density with CO₂ dissolution using the Peng-Robinson equation of state and the Pedersen viscosity correlation is presented. This method is applied to model the observed increase in oil density with CO₂ dissolution in a West Texas crude oil. Compositional simulation of CO₂ injection was performed in a 2D vertical cross section and a 3D reservoir with the density effect. The results show that the density increase from CO₂ dissolution may have a drastic effect on CO₂ flow path and recovery performance. One main conclusion from this work is that there is a need to have accurate density data for CO₂/oil mixtures at different CO₂ concentrations to ensure successful CO₂ injection projects. While CO₂ enhanced oil recovery (EOR) is part of the solution, saline aquifers have the largest potential for CO₂ sequestration. A literature review of the CO₂ sequestration in saline aquifers is performed. The dominant trapping mechanisms and transport processes and the methods used to model them are discussed in detail. The Aruma aquifer, a shallow saline aquifer in southwest Qatar is used as a case study for CO₂ sequestration. A compositional simulation model is prepared for the Aruma aquifer using the available log data and flow test data. It was found that the grid size is a key parameter in modeling CO₂ sequestration accurately. It affects the propagation of the CO₂ plume and amount of CO₂ in brine. |
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