Abstract:

Determination of permeabilities of low permeability rock (≤10－18 m2) under different stress conditons and temperatures is the basis of stability evaluation in geological disposal of radioactive waste，underground gas and oil storage tanks and construction of deep cavern groups. Based on the developed low permeability test equipment(T-M-PTS)，gas transport properties of typical Jinping marbles are studied under different hydrostatic pressures and temperatures. Based on microcrack linkage model, evolution of permeability is also studied theoretically. Some results are achieved：(1) Klinkenberg effect is remarkable when gas transport through dense rocks, and should be considered; (2)based on statistic theory and percolation theory, a 3-D penny-shaped microcrack moded has been developed to predict and investigate the evolution of permeability due to microcrack closure in compressive regime; (3) permeability decreases as hydrostatic stress increases because of the decrease of porosity under compression, and permeability decreases faster at the first stage of compression; and (4) permeability decreases from 21.9×10－21 m2 to 3.9×10－21 m2 as temperature increases from 15℃ to 40℃ because of the decrease of elasticity, which lead to decrease of porosity under the same hydrostatic stress.

Key words: low permeability medium, Klinkenberg effect, percolation, intrinsic permeability