页岩含水分布及其对甲烷吸附影响的孔隙尺度模拟  

Water distribution in shale and its effect on methane adsorption:A lattice Boltzmann simulation

作　　者：张涛[1] 赵玉龙[1] 张烈辉[1] 何骁[2] 李树新 李星涛 刘香禺 王滨瑞 ZHANG Tao;ZHAO Yulong;ZHANG Liehui;HE Xiao;LI Shuxin;LI Xingtao;LIU Xiangyu;WANG Binrui(National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University,Chengdu 610500,China;PetroChina Southwest Oil&Gasfield Company,Chengdu 610051,China;PetroChina Coalbed Methane Co.,Ltd.,Beijing 100028,China)

机构地区：[1]西南石油大学油气藏地质及开发工程全国重点实验室,四川成都610500 [2]中国石油西南油气田公司,四川成都610051 [3]中石油煤层气有限责任公司,北京100028

出　　处：《天然气地球科学》2024年第12期2253-2263,共11页Natural Gas Geoscience

基　　金：国家自然科学基金重点基金项目“海相页岩水平井超临界二氧化碳压裂机理与一体化模拟研究”(编号:52234003);国家自然科学基金优秀青年科学基金项目“页岩气多尺度非线性渗流力学”(编号:52222402);国家自然科学基金青年项目“CO_(2)-水-岩系统中‘溶解-沉淀-沉淀运移’机制及微观渗流规律研究”(编号:52304044);四川省科技计划项目“深层页岩气藏流体赋存及多相流动介观模拟方法研究”(编号:2023NSFSC0934);中国石油—西南石油大学创新联合体科技合作项目“不同构型页岩储层流体流动规律及开发优化理论与方法”(编号:2020CX030202)联合资助。

摘　　要：页岩原始储层含水,影响甲烷吸附能力,对页岩气储量精确评估带来困难。目前的主流研究方法具有一定的局限性,例如,吸附实验法缺乏直观性、分子动力学模拟法(MD)研究尺度较小、解析建模法相对理想等。基于格子玻尔兹曼方法(LBM),通过修正原始Shan-Chen模型考虑分子间作用力、耦合真实状态方程表征吸附热力学行为,建立了页岩水蒸气吸附和甲烷吸附的LBM模型,从介观孔隙尺度可视化展现了页岩三维孔隙网络中的含水分布及其对甲烷吸附的影响。结果表明,若将无机孔和有机孔的润湿角分别设为0°和120°,受亲水吸引力的影响,无机质呈现“小孔隙充填水、大孔隙附着水膜”的特征,而受疏水排斥力的影响,有机质不含水。不同含水饱和度下,孔喉配置关系和有机孔分布方式对有效流通路径的影响极大。原始页岩储层含水导致甲烷仅能吸附在有机质孔隙壁面,甲烷吸附位的数量大大降低。当压力较低和含水饱和度较高时,不考虑含水对甲烷吸附影响会导致计算的储量被高估(该研究算例可达到30%),特别对于黏土含量较高的陆相/海陆过渡相页岩,需要考虑含水对甲烷吸附的影响。Shale gas reservoir contains initial water saturation,influencing the adsorption capacity of methane,which makes challenge for the accurate reserve estimation for shale gas.Molecular dynamic simulation(MD),sorption experiment,and analytical modelling are the current methods to study this topic,which,however,have respective limitations in terms of lack of intuitiveness,small research scale,and relative idealism.Based on lattice Boltzmann method(LBM),the LBMs for water vapor sorption and methane sorption in shale are es⁃tablished by modifying the original Shan-Chen model to consider molecular interactions and by incorporating re⁃al equation of state to characterize the sorption thermodynamic behavior,and the water distribution in 3D pore network in shale and its effect on methane adsorption are visualized from the mesoscopic perspective.Results show that,if the contact angle of the inorganic pores and organic pores are assumed as 0°and 120°respectively,influenced by hydrophilic attraction forces,“small pores filled with liquid water and large pores covered by wa⁃ter film”can be found within inorganic matter;influenced by hydrophobic repulsion forces,no water can be found within organic matter.Under different water saturation,pore-throat configuration relationship and organic pores distribution have considerable effects on effective flow pathways.Due to the initial water saturation in shale gas reservoir,methane can only be adsorbed on organic pore surfaces,which reduces the numbers of meth⁃ane adsorption sites significantly.When the pressure is low and water saturation is high,the reserves will be overestimated if the effect of water distribution on methane adsorption is ignored(the error can be up to 30%for the studied case).Especially for continental/transitional shale gas reservoir which contains high clay contents,the effect of water distribution on methane adsorption should be considered.

关 键 词：页岩 气水分布 甲烷吸附 格子玻尔兹曼法 储量评价 

分 类 号：TE122[石油与天然气工程—油气勘探]