Modelling the effect of oil on foam for EOR: Local equilibrium behavior

Enhance Oil Recovery (EOR) techniques are theoretically very promising but in real life suffer the effects of many physical complications in the subsurface which are yet to be understood in detail. One such complication is the detrimental effect of oil in foam in foam EOR. Current-generation reservoir simulators represent these effects in an approximate way. The STARS simulator is one such simulator. Though nearly 20 years old, till now there has not been a detailed study on how its parameters predict foam behavior without oil. We investigate in detail the effect of the oil-related parameters in the STARS simulator by studying the behavior of foam in the two foam-flow regimes, as identified by Osterloh and Jante and Alvarez et al, on steady state behavior of foam without oil. The focus of this thesis is to study the shift in the two foam-flow regimes with oil present. This is achieved by fixing oil saturation, fixing oil superficial velocity or by fixing the oil to water superficial velocity ratio. Initially we employ a Corey-type relative- permeability function. We investigate the effects of oil-related parameters with fixed limiting water saturation (wet foam model) but later study the effects of changing limiting water saturation (dry-out foam model). We then proceed to understand the model behavior for three-phase oil relative permeabilities by implementing Stones Model II oil relative permeabilities in both the models (STARS Foam Simulator). Additionally, we generate 3D plots of pressure gradients as a function of phase saturations to examine the effect of oil-related parameters of the STARS simulator on foam. We capture and understand the behavior of all above mentioned cases on gas foam mobility reduction factor (FM) plots to predict foam performance under Corey’s and Stone’s saturation profiles. The study reveals combinations of oil, water and gas superficial velocities where the steady-state saturations and foam state are not unique. We study these cases further using a simple 1D in-compressible simulator.

Subject

foam
enhanced oil recovery
effect of oil on foam
foam simulation
mobility control

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master thesis

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