Abstract
Reservoir simulation and modeling remains a cost-effective tool to characterize geological structure, determine fluid saturation, and optimize reservoir performance. In spite of extensive research work, it remains a challenge to generate multiple reservoir models conditional to static and dynamic data that represent a correct sampling of the true posterior probability density function. Although many challenges remain, the ensemble Kalman filter (EnKF) technique has recently been proved to be an efficient data assimilation method and successfully used in assisted history matching for estimating reservoir petrophysical parameters, such as porosity, absolute and relative permeability, and fluid-contact depth. Few attempts have been made to study impacts of simultaneously tuning multiple parameters on the estimation results. In this study, the ensemble-based history matching has been successfully applied to simultaneously estimate multiple petrophysical parameters for the PUNQ-S3 model. More specifically, the selected tuning petrophysical properties include horizontal and vertical permeability, porosity and three-phase relative permeability curves. Four data assimilation scenarios with different combination of the tuning parameters have been evaluated. The ensemble-based history matching technique is found to be capable of estimating multiple petrophysical parameters by conditioning the reservoir geological models to production history. The uncertainty range of production data generated from the updated models is reduced compared to that of initial models. However, the history-matched models may not always provide good production prediction results, especially when absolute permeability and relative permeability are tuned simultaneously. This further illustrates the non-uniqueness of the history matching solutions. In addition, for the PUNQ-S3 case examined in this study, three-phase relative permeability curves can be estimated with good accuracy when absolute permeability fields are known.
