Microscopic oil displacement and sweep efficiency of waterflooding and continuous gas injection can be improved by water alternated gas (WAG) injection.
Reservoir and fluid properties are determining factors in screening WAG injection strategies. Evaluation of miscibility condition is an important step in the process design. Different correlations used for miscibility evaluation are compared on the Brent reservoir example. The effect of injection parameters on injectivity and recovery in the layers of a stratified reservoir is shown through the simulation results.
Methods improving WAG efficiency like non-stationary injection are discussed. Main parameters of cyclic injection with variation of flow directions are considered in relation with non-stationary WAG. Numerical modelling with respect to three phase effects showed the advantages of non-stationary WAG in a stratified reservoir.