Abstract: Permeability of reservoir rocks changes with stress applying on the rocks. The change of permeability is due to the change of primary effective stress of rocks, not the Terzaghi's effective stress. Study on the permeability sensitivity should adopt the primary effective stress instead of the conventional Terzaghi's effective stress. Adoption of Terzaghi's effective stress usually overestimates the loss of reservoir permeability due to the drawdown of reservoir pressure.

Key words: reservoir, permeability, stress, sensitivity