Abstract: Based on a study conducted on characteristics of the porosity-depth curve and its mathematic expression, it is discovered that the curve could be divided into two stages, namely an exponential decline stage and a constant stage. The earlier traditional porosity-depth curve can only be used to describe the variation of porosity in exponential decline stage. The newly-suggested unified porosity-depth equation can be used to describe the variation of porosity simultaneously both in exponential decline stage and in constant stage too. Consequently, the new equation will serve better in the research work of basin simulation and petroleum geology.

Key words: porosity, burial depth, curve, equation