Percolation Theory of Oil-Gas Two Phases (Dissolved Gas Drive)

Abstract

There is also lots of natural gas dissolved in oil in any reservoir. No matter if reservoir is opened or closed, when the bottom pressure of oil well is lower than the saturation pressure, in definite area near bottom the initial natural gas dissolved in oil before will separate from oil, which will cause oil-gas two-phase percolation in this area. With the decrease of formation pressure, the two-phase area will expand to the whole formation. And when the formation pressure is lower than the saturation pressure, the whole reservoir will form the oil-gas two-phase percolation. The dissolved gas drive is a kind of drive mode of the least recovery ratio which is lower than 10%. However, it is the least cost because it totally depends on the natural energy to develop. The theory calculation proves that the recovery ratio will not decrease when formation pressure is 20% lower than saturation pressure, while that is not approved in reality.