Abstract: According to the statistics formula between the ratio of capillary pressure to threshold pressure (P_c/P_e) and the efective wetting phase saturation($s_{wt}^{*}$) established by Brooks R.H. and Corey A.T, the method for determining average capillary pressure curve is presented in this paper. It is checked with the data of mercury injection capillary pressure of Xiazijie oilfield and the shape of curve is satisfactory. As compared with that of the traditional J-function, this method is simple, convenient, high-precision and easy to operate on PC. Meanwhile, a mathmatical expression for average capillary pressure curve and porosity size distribution exponent λ also put forward. It is of great significance to extend: the application of capillary pressure curve.

Key words: Capillary Pressure, Curve, Pressure, Saturation, Linear, Regression analysis