Field-scale simulation of WAG using pore-scale network modelling

In recent years the interest in water alternating gas (WAG) injection as tertiary recovery method has increased. This method has been applied successfully in many fields around the world. The WAG process results in three-phase flow, of which the mechanisms are still not well understood. Therefore; it is important to understand and properly describe the multi-phase flow properties (relative permeability and capillary pressure) which controll the WAG process.

In this study we have used pore-scale network modeling to describe the multi-phase flow properties for use in reservoir simulation of WAG injection at the field scale. Network models are being used as alternative for empirical methods to describe the multi-phase flow properties, since the former are physically-based tools which integrate the relevant pore-scale mechanisms while the latter often have little physical basis. A recently developed three-phase flow pore-network model has been used, which integrates the formation and collapse mechanism for oil layers, represents more complexity of the pore structure and incorporates so-called multiple displacement process. In the reservoir simulation we have studied the effect of WAG on recovery factor for different injection scenarios. We additionally studied the effect of different WAG ratios on improving overall WAG performance.