Abstract: Using build-up pressure curves to get saturation pressure of unsaturated reservoirs with low formation-saturation pressure difference in different types of reservoirs can not only make up the defects of limited PVT data and rigorous condition for sampling, but also can expand the applied range of build-up pressure curves. The application of this method to SN block in SX oilfield has obtained satisfactory result.

Key words: unsteady well testing, formation-saturation pressure difference, pressure build-up, saturation pressure