An analysis of composition and rate effects in gravity stabilised gas injection

Gravity stabilised gas flooding is believed to have considerable potential as an lOR process in North Sea fields, This paper considers the mechanisms affecting the displacement efficiency. A theoretical analysis of gas flooding using the method of characteristics is summarised. A major result of this analysis is that the process should not be thought of as oil draining into an oil bank, but rather in terms of oil being left bebind, An analytical expression for the process efficiency in secondary flooding is derived, which for a given oil relative permeability Corey exponent is a function of a single dimensionless variable.