Sensitivity of Reservoir Simulations to Uncertainties in Viscosity

Abstract

Abstract The paper examines the sensitivity of reservoir simulations to uncertainties in viscosity. The simulations are performed for three different oils, ranging from light to viscous, for three different geological terrains. In each case, the viscosity has been estimated by a number of currently recommended prediction methods and by recourse to the measured values. The preliminary results indicate that the results of reservoir simulations are sensitive to the fluid viscosity. The sensitivity increases with increase in the absolute viscosity of the oil, increase in heterogeneity of the reservoir and increase in uncertainty in viscosity. The results show, that in the worst case scenario examined (e.g. heavy, viscous oils, η > 6 cp) a ±1% error in viscosity will produce a 1% error in the cumulative production. Overall, the preliminary results indicate that the common assumption in reservoir simulations, that the accuracy of fluid properties has a marginal influence on the reservoir performance, is false. Uncertainties in viscosity can lead to large errors in predicted production rates, thus unduly influencing the economics of reservoir exploitation.