Abstract：When conducting seismic prediction for carbonate reservoir and its oil-gas possibility,we need to understand the rock physical change when filled with different fluids in the carbonate reservoir.In the absence of rock physical testing information,the studies on fluid substitution are needed.In this paper a fluid substitution method in carbonate reservoir was proposed.With this method the elastic properties of the rock matrix for carbonate were estimated by using full wave well logging data,the empirical formula by Batzle et al.was used to calculate elastic properties of the fluids,and Gassmman equation was used to calculate the elastic properties of rock matrix and to conduct the fluid substitution.Using statistic average algorithm to derive the elastic properties of the rock matrix is a character of the method,therefore the method does not need to know the rock constituents and other data and it can be easily used in the oilfield.
