Enhancement of a compositional reservoir simulator, for realistic modeling of CO(2) EOR processes

Phase equilibrium calculations are of primary importance in the numerical simulation of gas injection processes. The presence of an aqueous phase will influence the phase behavior of CO{dollar}sb2{dollar}/hydrocarbon systems. However, most reservoir models have traditionally ignored the aqueous phase from phase behavior studies. UTCOMP, a three-dimensional, compositional reservoir simulator was modified to include the gas solubility in the aqueous phase. In the modeling of CO{dollar}sb2{dollar} EOR processes, carbon dioxide is by far the most soluble gaseous component in the aqueous phase. The principle of Henry's law is used to model CO{dollar}sb2{dollar} solubility in the aqueous phase.; The modified algorithm in the simulator was validated by successfully history-matching the experimental Salt Creek immiscible CO{dollar}sb2{dollar} corefloods results. The effect of CO{dollar}sb2{dollar} solubility in the aqueous phase was also determined in the simulation runs. The simulator was used to identify the primary mechanisms responsible for incremental oil recovery during a CO{dollar}sb2{dollar} displacement process. Several parametric runs were also performed to investigate the sensitivity of the CO{dollar}sb2{dollar} flooding process to variations in key reservoir and operational conditions. The normalized Stone I method was used to estimate the three-phase oil relative permeabilities in the simulator.; The simulation results demonstrate that the model overestimates the ultimate oil recovery when the CO{dollar}sb2{dollar} solubility in aqueous phase is ignored. Better fits for the experimental Salt Creek fluid production profiles were obtained when the presence of the aqueous phase was accounted for in the phase equilibrium calculations. This study also indicates that the gas solubility effects in the aqueous phase could reduce the predicted oil recovery by as much as 5 to 7%. The most severe reductions in oil recovery was observed for the water alternating gas cases.; The cyclic CO{dollar}sb2{dollar} simulation runs show that the incremental oil recovery is sensitive to the injected CO{dollar}sb2{dollar} slug size, initial oil saturation and the bottomhole pressure during the production period. The predicted huff 'n' puff process performance worsened under the reservoir and operating conditions prevalent in typical Wyoming formations, which is in agreement with the field test results.