页岩气多层吸附的分子模拟与理论模型  

Molecular Simulation and Theoretical Model of Shale Gas Multilayer Adsorption

作　　者：穆中奇 宁正福[1,2] 吕方涛 顾可名 刘蓓[3] MU Zhongqi;NING Zhengfu;LYU Fangtao;GU Keming;LIU Bei(State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum(Beijing),Beijing 102249,China;Key Laboratory of the Ministry of Educationfor Petroleum Engineering,China University of Petroleum(Beijing),Beijing 102249,China;State Key Laboratory of Heavy Oil Processing,China University of Petroleum(Beijing),Beijing 102249,China)

机构地区：[1]中国石油大学(北京)油气资源与探测国家重点实验室,北京102249 [2]中国石油大学(北京)石油工程教育部重点实验室,北京102249 [3]中国石油大学(北京)重质油国家重点实验室,北京102249

出　　处：《西安石油大学学报（自然科学版）》2023年第1期69-76,84,共9页Journal of Xi’an Shiyou University（Natural Science Edition）

基　　金：国家自然科学基金项目“海相深层油气富集机理与关键工程技术基础研究”(U19B6003-03-04);国家自然科学基金项目“页岩气多组分竞争吸附机理研究”(51774298)。

摘　　要：用蒙特卡洛方法获得了储层条件下页岩气在有机质孔内的吸附等温线,并用分子动力学方法获得孔内气体分布与吸附层特征。基于热力学理论提出了表征过剩吸附的超临界气体多层吸附模型。通过用多层吸附模型与Langmuir模型拟合吸附等温线并分析拟合结果,说明多层吸附模型的合理性与优点。结果表明:非微孔中,页岩气发生双层吸附,靠近孔壁的第一吸附层受到的吸附作用远强于远离孔壁的第二吸附层,吸附层体积与温度、压力、孔宽无关,吸附层密度与孔宽基本无关。在宽1 nm的孔中,页岩气形成填充全部自由空间的吸附。超临界多层吸附模型拟合非微孔吸附等温线的效果与Langmuir模型同样良好,但其得到的吸附层厚度更准确,且能较准确计算吸附层密度随压力变化规律。The isotherms of the shale gas adsorbed in organic matter poresunder the reservoir conditions were acquired by Monte Carlo simulation, and the gas distribution in the pores and thecharacteristics of adsorption layers are obtained using molecular dynamics simulation.A supercritical multilayer gas adsorptionmodel for characterizing excess adsorption is proposed on the basis of thermodynamics.The gas adsorption isotherm is fitted with the model and Langmuir equation and the reasonability and advantages of the model are illustrated by analyzing the fitted results.The results show that shale gas is adsorbed as double layers in non-micropores.The adsorption of the first adsorption layer near the pore wall is much stronger than that of the second adsorption layer far away from the pore wall.The volume of adsorption layers is independent of temperature, pressure and pore width, while the density of adsorption layers is almost independent of pore width.In the pore with a width of 1 nm, shale gas forms adsorption to fill all free space.The effect of the supercritical multilayer adsorption model is as good as that of Langmuir model in fitting non-microporous adsorption isotherm, but the adsorption layer thickness obtained by it is more accurate than that by Langmuir model, and the change rule of the adsorption layer density with pressure can be more accurately calculated.

关 键 词：气体吸附 多层吸附 分子模拟 超临界 页岩气 

分 类 号：TE311[石油与天然气工程—油气田开发工程]