Hybrid Modelling of Heterogeneity to Improve 3D Simulation Results: Case Studies 1 and 2 on a North Sea Gas Field

Abstract

A three-dimensional computer simulation model of a Rotliegend gas field, constructed to describe the fluid and reservoir behaviour under strong water drive, predicted certain problems in the gas field. A detailed characterization of the reservoir properties that influence the fluid movement was deemed necessary. Accordingly, a hybrid modelling technique was applied. The deterministic part of this method produced detailed maps of reservoir porosity and horizontal permeability based on a sedimentological model and a distinct facies correlation. The stochastic part of this method was developed to calculate how the presence of shale breaks affects fluid behaviour in terms of flow-path tortuosity and vertical effective permeability. Two different models based on different structure maps of the same gas reservoir were constructed. The geological models that resulted from applying the hybrid modelling technique provided a base for an adequate and simple matching procedure. The models were matched satisfactorily with the average reservoir pressure, water breakthrough in well 4 and the rise of the gas—water contact (GWC) in the field. Both models can predict the overall fluid movement within acceptable confidence levels.