页岩气储层吸附渗流研究现状及发展趋势

Status quo and development trends of research on shale gas adsorption and seepage in shale gas reservoirs

张益 张斌 刘帮华 柳洁 魏千盛 张歧 陆红军 朱鹏宇 王瑞

Yi ZHANG Bin ZHANG Banghua LIU Jie LIU Qiansheng WEI Qi ZHANG Hongjun LU Pengyu ZHU Rui WANG

针对页岩气藏有机微纳米级孔隙中吸附气大量赋存以及有机质以“镶嵌”形式赋存于无机质中的特点，分析了目前页岩气吸附渗流的表征方法，并对影响吸附渗流的重要因素如气体吸附层厚度变化、无机孔水膜厚度变化和气体解吸导致孔隙变化的数学表达方法进行了归纳，接着指出了目前表观渗透率计算模型中存在的主要问题：①储层孔隙结构表征不够准确；②固溶态气体分子解吸对吸附渗流流量的影响尚无表征方法；③对页岩气储层有机质的离散分布刻画不完善；④直接应用室内等温吸附实验参数不合理，忽视了吸附态和固溶态页岩气的吸附-解吸差异性。然后分析了利用分子模拟技术研究页岩气的吸附渗流相较于物理实验的优点，总结了应用该技术对页岩气吸附渗流进行建模和模拟的方法及模拟结果，并就页岩气吸附渗流的分子模拟技术未来发展提出了建议：①基于常规无机孔和有机孔分子模型，继续改进多介质、多尺度建模方法，以符合页岩气储层实际情况；②开发更符合实际页岩气吸附渗流过程的页岩气吸附渗流模拟方法。

Shale gas reservoirs are characterized by large amounts of adsorbed gas within nano- to micron-scale organic pores and the mosaic form of organic matter in the inorganic matter. To understand these unique features， we initially review current methodologies used to characterize shale gas adsorption and seepage. Afterward， we summarize the mathematical representations of critical factors influencing these processes， including changes in the gas adsorption layer thickness， changes in the thickness of water film in inorganic pores， and changes in gas desorption-induced pores. Subsequently， we point out major problems in the current models of calculating the apparent permeability of shale gas reservoirs： （1） inaccurate characterization of reservoir pore structures； （2） a lack of methods to characterize the effects of the desorption of gas molecules dissolved into the solid organic matter on the adsorption of seepage flux； （3） inadequate characterization of the discrete distribution of organic matter in shale gas reservoirs； and （4） the unreasonability in direct application of parameters obtained from laboratory isothermal adsorption experiments， which neglects the differences between adsorbed shale gas and that dissolved into the solid organic matter in adsorption and desorption. Then， we analyze the advantages of the molecular simulation technique over physical experiments in examining shale gas adsorption and seepage. Accordingly， we summarize molecular simulation technique-based methods for modeling and simulating shale gas adsorption and seepage， as well as the simulation results. Finally， suggestions for further advancement in the molecular simulation of shale gas adsorption and seepage are put forward， including the improvement of multi-medium and multi-scale modeling methods based on conventional molecular models of inorganic and organic pores to be in line with the actual situation of shale gas reservoirs， as well as the necessity to develop methods for shale gas adsorption and seepage simulation that are more suitable for actual conditions.

10.11743/ogg20240118