Abstract:

The Carboniferous shale in Eastern Qaidam is a highquality source rock with great hydrocarbon potential. Adsorption is the most important form of shale gas storage. But the shale adsorption of this region had never been wellstudied and had seriously hindered the development of shale gas production. According to the law of conservation of matter and the principle of thermodynamic equilibrium, by using the gasparticle two phase adsorption analytical instrument designed by ourselves, and based on the industrial standard of highpressure isothermal determination of adsorption of coal, we carry out methane isothermal adsorption experiments for the shale sample from Shiqian 1 Well in eastern Qaidam Basin under 30 ℃, 40 ℃, 50 ℃ and 60 ℃. The LangmuirFreundlich model is used for adsorption nonlinear regression analysis. The isosteric heat equation for mathane adsorption to coal is calculated through ClausiusClapeyron equation. The experimental results show that: at a certain pressure, methane adsorption capacity of shale decreases with increasing temperature; and at a certain temperature, pressure increases, the amount of methane adsorption increases firstly and then decreases. And it is characteristic of a typical supercritical adsorption. LF model fits well to isothermal adsorption process. Through the experimental results the 4 parameters in the model are determined and the physical meaning of each parameter is clear. The relation between the calculated isosteric heat and adsorption capacity is q=-3679.7n+9779.5. The isosteric heat deceases with the increasing of adsorption capacity. Isosteric heat combined with LF model can predict the adsorption of shale gas at any temperature and pressure. The predicted results are in good agreement with experimental data. It has practical significance for the evaluation and exploitation of shale gas.

Key words: adsorption experiment, LangmuirFreundlich model, isosteric heat, shale gas, Eastern Qaidam