页岩气超临界吸附机理及模型

发布时间：2018-10-09 08:24

【摘要】：页岩气吸附机理和模型的研究对于页岩气地质储量计算和开发方案编制等具有重要意义.结合低温氮气吸附实验和高压甲烷等温吸附实验,对龙马溪组页岩的微观孔隙结构和超临界吸附特征进行了分析.结果表明,孔隙体积和比表面积主要受中孔(2~200 nm)控制;在压力较大时(10 MPa),页岩过剩吸附量随着压力增大而降低.4种常用吸附模型的对比分析表明:对于微孔充填方式,D-A模型的拟合效果要优于D-R模型;对于单层吸附方式,L-F模型的拟合效果要优于Langmuir模型.结合孔隙体积分析结果,通过两种假设,证明了甲烷不是以单一的微孔充填或者单分子层吸附方式在页岩中进行吸附的,推测其吸附机理为微孔充填和单分子层吸附并存.并基于该吸附机理,建立了页岩气超临界吸附新模型——DA-LF模型.新模型比4种常用模型具有更好的拟合效果,并可以分别计算出微孔和中孔的吸附量.计算表明微孔充填吸附量比单层吸附量大,占总吸附量的76%左右.这表明页岩气超临界吸附机理可以进一步深化为:微孔充填为主、单分子层吸附并存.
[Abstract]:The study on the mechanism and model of shale gas adsorption is of great significance for the calculation of shale gas geological reserves and the preparation of development plans. Combined with low temperature nitrogen adsorption experiment and high pressure methane isothermal adsorption experiment, the microscopic pore structure and supercritical adsorption characteristics of Longmaxi formation shale were analyzed. The results show that the pore volume and specific surface area are mainly controlled by mesoporous (2 ~ 200 nm). When the pressure is high (10 MPa),) the excess adsorption capacity of shale decreases with the increase of pressure. 4 kinds of commonly used adsorption models are analyzed. The results show that the fitting effect of D-A model is better than that of D-R model for micropore filling mode. The fitting effect of L-F model for monolayer adsorption is better than that of Langmuir model. Based on the results of pore volume analysis and two hypotheses, it is proved that methane is not adsorbed in shale by single micropore filling or monolayer adsorption, and the adsorption mechanism of methane is presumed to be the coexistence of micropore filling and monolayer adsorption. Based on the adsorption mechanism, a new supercritical adsorption model of shale gas, DA-LF model, was established. The new model has better fitting effect than four common models, and the adsorption capacity of micropore and mesopore can be calculated respectively. The results show that the adsorption capacity of micropore filling is more than that of monolayer, accounting for about 76% of the total adsorption capacity. This indicates that the mechanism of supercritical adsorption of shale gas can be further deepened as follows: micropore filling is dominant and monolayer adsorption coexists.
【作者单位】： 北京大学工学院能源与资源工程系;中国石油勘探开发研究院;国家能源页岩气研发(实验)中心;
【基金】：国家重点基础研究发展计划(2013CB2281)资助
【分类号】：P618.13
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本文编号：2258650