摘要
页岩气藏纳米尺度孔隙发育,气体渗流规律受滑脱效应影响显著。当气体在纳米孔隙中渗流时,基于连续介质建立的常规渗流模型已不能准确模拟页岩气微观渗流特征。为了达到提高页岩气藏产能预测精度、指导压裂施工设计的目的,必须准确分析页岩气藏气体滑脱效应。利用格子Boltzmann方法,建立页岩气渗流模型,确定反弹—镜面组合边界条件,对页岩气藏气体滑脱效应进行模拟分析。结果表明:孔隙直径和努森数是表征页岩气藏气体滑脱效应强度的决定性参数;孔隙壁面附近气体滑移速度沿孔隙通道呈近似线性缓慢增长,在出口端增幅加剧,该现象验证了气体压缩效应及稀薄效应理论;气体滑移速度会随努森数的增加而增大,气体渗流进入滑移区后滑移速度增幅加剧,基于连续介质方程建立的模型局限性更加凸显;页岩储层表观渗透率会随努森数的增加而显著增大,当努森数大于0.1后,Klinkenberg模型不能精确表征气体滑脱效应。
Shale gas reservoir is abundant in nanoscale pores. Therefore,the gas seepage is influenced significantly by slip?page effect. Conventional flow model cannot simulate the seepage law accurately in shale gas when gas flows in nanometerpores. In order to improve the accuracy of production simulation and make guidance for fracturing operation in the shalegas reservoir,slippage effect during gas flow must be analyzed precisely and directly. Lattice Boltzmann method was ap?plied to built seepage model of the shale gas and to know boundary condition of bounceback-specular combination. Theslippage effect in the shale gas reservoir was simulated and analyzed. The results show that the pore size and Knudsen num?ber are the decisive factors which can be used to characterize the strength of slippage effect. The slip velocity of the gas mol?ecule along the pore channels has approximate linear growth and increases more dramatically in the outlet end,which cantestify the compression effect and rarefaction effect of the gas in the shale gas reservoir. The slip velocity will increase dra?matically with the rising Knudsen number,especially after gas seepage in slip zone. The limitation of models based on con?tinuous medium formula will be highlighted. With the rise of Knudsen number,the apparent permeability has been in?creased sharply. Klinkenberg model is no longer suitable for simulation of slippage effect during gas seepage in slip zone af?ter the Knudsen number is more than 0.1.
作者
赵金洲
符东宇
李勇明
彭瑀
廖毅
Zhao Jinzhou;Fu Dongyu;Li Yongming;Peng Yu;Liao Yi(State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University,Chengdu City,Sichuan Province,610500,China)
出处
《油气地质与采收率》
CAS
CSCD
北大核心
2016年第5期65-70,共6页
Petroleum Geology and Recovery Efficiency
基金
国家自然科学基金项目"页岩地层动态随机裂缝控制机理与无水压裂理论"(51490653)
国家"973"计划"中国南方海相页岩气高效开发的基础研究"(2013CB228004)
