Oil production in presence of a bottom aquifer is one of the most challenging issues in reservoir engineering. In most cases water coning happens very quickly and the influx of water restricts oil production and limits recovery. The problem is even more difficult when the oil is heavy because the viscosity contrast is large. In some cases horizontal wells may be used to improve the situation but when reservoirs are thin and the oil is viscous even horizontal wells are of limited use. This paper presents the challenges and potential solutions for Enhanced Oil Recovery in heavy oil reservoirs with bottom aquifer.
Existing literature is reviewed for field cases of EOR experience with bottom aquifer for chemical as well as thermal processes (SAGD, steam injection as well as In Situ Combustion).
In the case of chemical EOR the chemicals may be lost to the aquifer; for thermal recovery the bottom water can act as a heat sink and affect and steam oil ratio. Some in-situ combustion projects have been successful in such settings but in every case the outcome is the same: the economics of the project can be affected.
The paper contains some previously unpublished data of polymer injection in a heavy oil pool with some limited bottom aquifer; for the most part it is a review of the existing literature which may prove useful to practicing engineers who are faced with the issue of developing heavy oil resources in the presence of bottom aquifer.