柴达木盆地东部石炭系页岩吸附特性实验研究

The experimental study of adsorption characteristics of Carboniferous shale in Eastern Qaidam

柴达木盆地东部石炭系页岩是一套待开发的优质烃源岩,吸附是页岩气最主要的储集状态,但针对该区页岩吸附特征的研究较少。依据物质守恒与热力学平衡原理,运用自主设计的气固双相等温吸附实验仪,参考煤的高压等温吸附测定行业标准,对取自柴达木盆地东部石浅1井的页岩样品进行了不同温度(30℃、40℃、50℃和60℃)的甲烷等温吸附实验研究,并运用Langmuir-Freundlich(L-F)模型对吸附量实验值进行非线性回归分析;根据Clausius-Clapeyron方程计算得到页岩对甲烷的等量吸附热方程。研究结果表明:压力一定时,页岩对甲烷的吸附量随着温度升高而降低;温度一定时,随压力升高,甲烷吸附量出现先增大后降低的现象,具有典型的超临界吸附特征;L-F模型对等温吸附过程拟合效果良好,实验结果将模型中4个参数确定,且各参数物理意义明确;计算得到等量吸附热与吸附量之间的关系为:q=-3 679.7n+9 779.5,等量吸附热随吸附量增大而降低。等量吸附热结合L-F模型可以预测任意温度、压力下页岩对甲烷的吸附量,且预测值与实验所得数据结果吻合较好,对页岩气储量评估与开发利用具有实际意义。

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 ~C, 40 ~C, 50 ~C and 60 ~C. The Langmuir- Freundlich model is used for adsorption nonlinear regression analysis. The isosteric heat equation for mathane adsorption to coal is calculated through Clausius - Clapeyron 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.