Abstract: The permeability of rock is usually measured at common pressure and temperature on surface. However, the pressure and the temperature underground are much higher than that on surface condition. The permeability of rock decreases due to compression at higher pressure, and increases due to thermal expansion at higher temperature. A theoretical formula is proposed in this paper to calculate the permeability of rock underground from the permeability measured on surface condition. The formula takes account of the influences of pressure and temperature on the rock permeability. The calculations by the formula show that the permeability of rock underground is not much different from that measured on surface condition.

Key words: rock, permeability, pressure, temperature, compressibility