页岩气超临界吸附研究进展

 超临界吸附是指在临界温度以上时气体在固体表面上发生的吸附，在地层温度条件下，甲烷在页岩中的吸附为超临界吸附。吸附气是页岩气的重要组成部分，研究页岩气的超临界吸附对于页岩气储量评价和开发方案编制等具有重要意义。本文综述了国内外在页岩气超临界吸附研究方面的进展，从页岩等温吸附实验方法、超临界吸附特征及模型建立3方面进行分析。结果表明：1）页岩的甲烷吸附量与煤相比小很多，为满足页岩吸附量测试的要求，对于容量法吸附仪，应配置更高精度的压力传感器；对于重量法吸附仪，应配置更高精度的磁悬浮天平；2）等温吸附实验测试的吸附量为过剩吸附量，过剩吸附量在达到一定压力后会下降，在评价页岩的吸附能力时，不能将过剩吸附量和绝对吸附量混淆，这样将严重低估地层条件下页岩的吸附能力；3）页岩气的吸附面临着理论与实践相矛盾和脱节的问题，页岩气超临界吸附的研究应从理论和实验两方面入手，深化对页岩气超临界吸附特征的认识，建立具有普遍适用性的页岩气超临界吸附理论。

Progress and prospect in supercritical adsorption of shale gas

The supercritical adsorption is the adsorption of gas on the solid surface when the adsorption temperature is above the critical temperature. Under the condition of the shale gas reservoir, the adsorption of methane in the shale is the supercritical adsorption. The adsorbed gas is an important component of the total shale gas. Therefore, the study of the supercritical adsorption of shale gas is very important for the reserve evaluation and the development plan preparation of the shale gas reservoir. This paper reviews the research development of the supercritical adsorption of shale gas at home and abroad. It is shown that:1) compared to the coal, the methane adsorption capacity of the shale is very small. In order to meet the requirements of the shale adsorption test, pressure sensors with high accuracy in the volumetric adsorption apparatus are required, as well as an accurate magnetic suspension balance for the gravimetric adsorption apparatus; 2) the adsorption capacity measured by the isothermal adsorption experiment is the excess adsorption capacity, and the excess adsorption capacity will decline after reaching a certain pressure. So we should not confuse the excess adsorption with the absolute adsorption, which might cause the underestimation of the real adsorption capacity of the shale gas reservoir; 3) the shale gas adsorption is faced with the problem of discrepancy between theory and practice. In the future, the research of the shale gas supercritical adsorption should be conducted from two aspects:theory and experiment. We should focus on the understanding of the characteristics of the supercritical shale gas adsorption, to ultimately establish a universal and applicable theory of the shale gas supercritical adsorption and to guide practice and application.