Experimental Study on Desorption Hysteresis Characteristic for Shale Gas

 Compared with the adsorption isotherms, desorption isotherms could evaluate accurately shale absorbed gas reserves in different pressure stage, the desorption hysteresis characteristics exists in shale gas formation. In order to discover the adsorption hysteresis phenomenon and the influence factor of adsorption hysteresis in high pressure range, The physical properties test and adsorption/ desorption test of shale gas were Carried out by shale outcrop samples from horse Creek group in Eastern Sichuan. The results show that the shale gas adsorption isotherm curve and desorption isotherm curve are not coincided. It has obvious adsorption hysteresis loop, which hysteresis degree relate to shale physical parameter. It shows that the worse shale gas physical property is, the more complicated pore structure is, the more hysteresis degree appears. Meanwhile, three theoretical models were used to fit the measured isotherm adsorption and desorption curves. The results show that comparing to the Langmuir-Freudlich equation and Freundlich equation, Langmuir equation fits the adsorption and desorption characteristic of shale gas betterly.