Abstract: This paper analyses the relation of the variation of reservoir rock pore volume, porosity and compressibility with the effetive overburden pressure,and basing on the polynomials regreasion of rock experimental data,it presents the calculating. equations of rock porosity,mean and instaneous pore volume compressibility under the reservoir condition. The practical applieation of these equations to processsingrock testing date of Zhongyuan,Xinjing,and Sichuan oiifields proves that. this method is precise and convenient for calculation.

Key words: rock stress, rock deformation, rock pore, porosity measurement, compressibility, measuring method