Sun Ying, Li Shuxia, Sun Renyuan, Yang Shikai, Liu Xiaoqiang
School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China.
Department of Petroleum Engineering, University of Regina, Regina, Saskatchewan S4S 0A2, Canada.
ACS Omega. 2020 Jun 25;5(26):16189-16199. doi: 10.1021/acsomega.0c01675. eCollection 2020 Jul 7.
In order to evaluate the total shale gas-in-place (GIP) resources in deep formations, it is important to study the sorption of supercritical methane in shales. At present, the Dubinin-Astakhov model is used to describe sorption isotherms. However, it still has some shortcomings. The main objective of this study is to establish an optimized model for supercritical methane sorption in shales. A series of high-pressure methane sorption isotherms were measured at different temperatures (from 293 to 333 K) for shale samples collected in the Cengong block, Guizhou, China. The characteristics and causes of shale gas sorption capacity changes were analyzed. By comparing the fitting results of several conventional sorption models, the characteristics and applicable scope of these models are obtained. A four-parameter ( , , , and ρ) modified supercritical D-A model was developed to accurately estimate the sorption of supercritical methane on shales based on Polanyi sorption potential theory. The results show that the sorption characteristic curve of methane on the shale surface under high pressure is obviously different from that under low pressure. The density of the sorption phase and the virtual saturated vapor pressure have a great influence on the fitting results of the sorption models. The density of the adsorption phase directly determines the ultimate sorption capacity of the shale sample. Also, the modified D-A model can improve the accuracy of the prediction of supercritical methane sorption on shales, and it can accurately describe the isothermal sorption law of gas in the supercritical state.
为了评估深层地层中的页岩气原地总资源量，研究超临界甲烷在页岩中的吸附作用很重要。目前，杜宾宁-阿斯塔霍夫模型用于描述吸附等温线。然而，它仍存在一些缺点。本研究的主要目的是建立一个优化的页岩中超临界甲烷吸附模型。对在中国贵州岑巩区块采集的页岩样品，在不同温度（从293到333K）下测量了一系列高压甲烷吸附等温线。分析了页岩气吸附能力变化的特征及原因。通过比较几种传统吸附模型的拟合结果，得出了这些模型的特征及适用范围。基于波兰尼吸附势理论，开发了一个四参数（、、、和ρ）修正超临界D-A模型，以准确估算超临界甲烷在页岩上的吸附。结果表明，高压下甲烷在页岩表面的吸附特征曲线与低压下明显不同。吸附相密度和虚拟饱和蒸气压对吸附模型的拟合结果有很大影响。吸附相密度直接决定了页岩样品的最终吸附能力。此外，修正后的D-A模型可以提高超临界甲烷在页岩上吸附预测的准确性，并且能够准确描述气体在超临界状态下的等温吸附规律。
