The initial oil saturation calculation and water cut rising rules of low oil saturation reservoir

Under the influence of low amplitude structures, low formation dip, low reservoir permeability, insufficient supply of oil sources and other factors, there is free water in the reservoir. If large areas of the reservoir in the entire layer series of development are oil-water layers, it is a low oil saturation reservoir. Reservoir wells have certain water cut during the initial production in low oil satura-tion reservoir. Oil-water relative permeability curves are obtained from indoor core tests in the case of the saturated oil, therefore, the actual water cut and degree of reserve recovery which was calculated through indoor tests can't match well. And the error will be very large with higher initial water saturation, which makes the theoretic curve of water cut and degree of reserve recovery unable to predict water cut rising rules correctly. Taking the method of confirming experimental data and actual production by each other, based on the relative permeability curves obtained by experiments and data from actual production, this paper revises the laws of water cut rising, calculates the initial water saturation, and solves the problems of the calculation of the initial oil saturation and the prediction of water cut rising rules in a reservoir with initial water saturation, which is of great importance to a correct understanding of reservoir and the prediction of development index.