Multicomponent mass transfer across water "lms during hydrocarbon gas injection

Understanding the dynamics of pore-scale multicomponent gas and oil mass transfer across water "lms during hydrocarbon gas injection in petroleum reservoirs is important in the design of tertiary oil recovery schemes at the "eld scale. The water "lms prevent oil and gas coming into direct contact and, for miscible gas injection, delay the onset of miscibility. We use a pore-scale model to describe the di7usion-controlled mass transfer through the water "lms. The following di7erent processes are found: (i) rapid oil swelling which results in short times needed to rupture the water "lms shielding the oil, (ii) slow oil swelling resulting in very long water "lm rupture times and (iii) both oil swelling and oil shrinking. The rate of oil recovery and the way it is recovered (either by rupturing the water "lm or being vaporized into the displacing gas) is critically dependent upon the oil and gas compositions, the oil droplet size and the water "lm thickness. We show cases at the pore scale where the time for gas and oil to be brought into direct contact and reach equilibrium in the presence of water "lms during miscible gas displacement is so long that water-blocking will adversely a7ect oil recovery at the "eld scale. ? 2003 Elsevier Science Ltd. All rights reserved.