Abstract:

Theoretical study of water saturation in oil-water fluid flow area is meaningful to the high, stabilized production and the improvement of ultimate recovery. At present, there is no theoretical description of water saturation in the oil and water seepage process. Combining relational expression between relative permeability and water saturation with the fractional flow equation produces an expression of water cut changed by water saturation; Introducing Taylor expansion and Vieta's theorem to the differentiation of water cut gives a theoretical expression of water saturation in oilwater fluid flow area; Possibility of continuity of the water saturation is also discussed. Applying this formula to certain sandstone reservoir in China achieves good results: In oil-water seepage process, water saturation is continuous in certain interval and the values of it are double in another interval; the oil recovery can be re-calculated and improved with this new equation. This new water saturation equation lays a base for the study of residual oil mobility and enhanced oil recovery.