Dong, F.; Feng, Z.; Yang, D.; Zhao, Y.; Elsworth, D. Permeability Evolution of Pyrolytically-Fractured Oil Shale under In Situ Conditions. Energies2018, 11, 3033.
Dong, F.; Feng, Z.; Yang, D.; Zhao, Y.; Elsworth, D. Permeability Evolution of Pyrolytically-Fractured Oil Shale under In Situ Conditions. Energies 2018, 11, 3033.
In-situ injection of steam for heating of the subsurface is an efficient method for the recovery of oil and gas from oil shale where permeability typically evolves with temperature. We reported measurements on Jimusar oil shales(Xinjiang, China) at different temperatures to 600℃ and under recreated in situ triaxial stresses to obtain permeability evolution with temperature and stress. Permeability of tight oil shales evolves with temperature to a threshold temperature and peak temperature. The threshold temperature was subjected to triaxial stresses. For Jimusar oil shale, the threshold temperature ranges from 200℃ to 250℃ at ground stress of buried depth of 500m and from 350℃ to 400℃ at buried depth of 1000m. The peak temperature was almost not subjected to triaxial stress and the range is from 450℃ to 500℃ for all Jimusar samples. Pyrolysis plays an important role in permeability evolution and fundamentally changes permeability tendency and magnitude. At high temperature permeability exhibits a little reduction due to stress effect but still remains a high level due to pyrolysis. The above results show that oil shale mass can change from tight porous media into highly permeable media and oil & gas can easily flow through oil shale stratum.
Oil shale; Permeability; Pyrolysis; High temperature and high pressure
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