Abstract: The keep-up pressure recovery of most oil-gas reservoirs and the gas storage measurement on some depletion reservoirs have been made in China, which have endlessly caused variation of pressure difference between inside-pore and outside-pore, followed by always changes of compressibility, porosity and permeability of rocks due to injection and production time and again of reservoir fluids. The variation of petrophysical parameters with pressure drawdown is better known, but the changing law of them with cycling, rising and declining of formation pressure is seldom researched. This paper presents the experiment of compressibility, porosity and permeability by using artificial cores on which different confining pressures are put. Study shows that these petrophysical parameters will change with pressures, of which rock porosity will affect other parameters' variations, and permeability has lag-effect during cycling, rising and declining of the pressure.

Key words: reservoir, compressibility, porosity, permeability, overburden pressure