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The effect of temperature on their permeability to gas flow of non-stressed rocks |
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The effect of temperature on their permeability to gas flow of non-stressed rocks Authors: J. Żółcińska, L. Dryga
An investigation of the permeability of sandstone from Tumlin together with fine and coarse-struetured granites from Strzelin was conducted using a steady flow ofnitrogen and helium. The permeability values were detennined for sampIes cut from solid rock-masses, firstly at ambient temperature and subsequently at temperatures of 100oC, 200oC, 300oC and 500oC. Heating the Tumlin sandstone up to 100oC rcsulted in its cvident drying up and the desorption of all the gases contained in it; therefore the permeability increased more than eight-fold. Further heating to 300oC caused a decrease in permeability whilst on raising the tcmperaturc to 500oC the permeability again increased somewhat, due to both a slightly greater level of rock destruction, by the removal of the bonded water and other changes in its ilIitic binding material. Both Nitrogen and Helium showed similar temperature-related flow-patterns. The progressive changes in permeability accompanying the heating, measured from the flow of both gases, were observed to be qualitatively identical for the fine-grained and coarse-structured--grained granites. A monotonie increase in permeability was observed, which was much higher than in the case of sandstone. This was due to the dehydration of the granite and, possibly, to the preferential direction o fthe thermal expansion of the rock material, resulting from the directional array of the biotite plates in the granite.
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2011