Evaluation of the Potential Application on the Wag Process in a North Sea Reservoir

Abstract

The paper discusses the potential increase in oil recovery due to injection of water alternating gas (WAG). The WAG process is compared to waterflooding and gas injection. The mechanisms of the WAG process which makes the process interesting for a North Sea reservoir are discussed. The application of a WAG scheme is discussed with regard to the field restrictions and possibilities of Norwegian reservoirs. The WAG process is found to improve the oil recovery primarily due to improved vertical sweep efficiency. Cross-sectional models have been used to study the sensitivity to variations in vertical permeability. The paper also reports results of multi-phase displacement experiments using sequences of gas and water injections. The oil recovery by primary and secondary injection of both gas and water have been measured both on Berea sandstone cores and sandstone reservoir cores. The measurements include experiments at realistic reservoir conditions using reservoir fluids, and also series of experiments performed at reduced pressure and temperature utilising model fluids.