Abstract: To implement the transformation of the relationships between permeability and confining pressures in changing-confining-pressure stress sensitivity experiments into the ones in changing-pore-pressure stress sensitivity experiments, and obtain the relationships between permeability and pore pressure, changing- confining -pressure stress sensitivity experiments and special stress sensitive experiments in tight sandstones with microfractures and artificial fractures are carried out. At the same time, based on the experimental data in changing-confining-pressure stress sensitivity experiments and the effective stress equations, the relationships between permeability and pore pressure are calculated, and are compared with the results in changing-pore-pressure stress sensitivity experiments. The results indicate that calculated permeabilities are larger than those measured directly, which is caused by the Klinkenberg effect, dimensionless permeabilities measured directly are equal to those calculated with the nonlinear effective principle, while larger than those calculated with Terzaghi effective principle. Both effective stress and slippage effect affect the determination of permeability in situ.

Key words: effective stress, nonlinear, stress sensitivity, artificial fracture, micro-crack