Abstract

The advantages of WAG (water-alternating-gas) injection compared to gas injection and waterflooding, from technical and economical points of view, are results of creating a mixed zone in which both water and gas are flowing simultaneously. Previously, an analytical model was developed in the literature to evaluate complete segregation distance and zone distributions for horizontal miscible WAG injection models. Even though this analytical model is derived using simplifying assumptions, it still gives good insight into the design of new projects when the lack of data does not allow a detailed full field reservoir simulation to be carried out. On the other hand, the advantages and disadvantages of applying WAG injection in dipped reservoirs, and up-dip or down-dip patterns are still in question while there isn’t any analytical model available for analyzing process in this type of reservoir. This paper develops analytical equations for a non-horizontal model and investigates the effect of dip angle on segregation effects in miscible WAG injection process. Up-dip versus down-dip WAG injection is another subject which will be discussed in this paper.

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