微纳米孔隙网络中天然气充注的三维可视化物理模拟

利用微纳米孔隙三维可视化在线天然气充注物理模拟实验，结合孔隙尺度原位叠算技术、孔隙网络模拟技术和视渗透率理论，研究低渗（致密）气充注过程中气水流动与分布规律及其影响因素。通过精确刻画分析微纳米孔隙网络中的气水流动与分布特征及其变化可以发现，低渗（致密）气充注过程分为扩张和稳定两个阶段：扩张阶段形成了大孔喉先于小孔喉，孔喉中央先于边缘的气驱水连续流动模式，半径大于20μm的孔喉是气相充注的主要通道；随充注动力增加，孔隙边缘和更小孔隙中央的可动水持续被驱出，半径为20～50μm和半径小于20μm的孔喉先后主导了气相充注通道的扩张，充注通道的孔喉半径、喉道长度和配位数递减，是气相渗透率与含气饱和度的主要增长阶段；半径为30～50μm的孔喉控制了含气饱和度的增长模式。稳定阶段，气相充注通道扩张至极限，通道的孔喉半径、喉道长度和配位数保持稳定，孔喉网络中形成稳定的不可动束缚水，气相呈集中网簇状、水相呈分散薄膜状分布，含气饱和度和气相渗透率趋于稳定。半径小于20μm的连通孔喉控制了气相充注通道的极限规模，控制了稳定气水分布的形成及最大含气饱和度。连通孔喉非均质性影响了孔喉中气相充注和气水分布的动态...

A three dimensional visualized physical simulation for natural gas charging in the micro-nano pore system

A micro-nano pore three-dimensional visualized real-time physical simulation of natural gas charging,in-situ pore-scale computation,pore network modelling,and apparent permeability evaluation theory were used to investigate laws of gas and water flow and their distribution,and controlling factors during the gas charging process in low-permeability(tight)sandstone reservoir.By describing features of gas-water flow and distribution and their variations in the micro-nano pore system,it is found that the gas charging in the low permeability(tight)sandstone can be divided into two stages,expansion stage and stable stage.In the expansion stage,the gas flows continuously first into large-sized pores then small-sized pores,and first into centers of the pores then edges of pores;pore-throats greater than 20μm in radius make up the major pathway for gas charging.With the increase of charging pressure,movable water in the edges of large-sized pores and in the centers of small pores is displaced out successively.Pore-throats of 20-50μm in radius and pore-throats less than 20μm in radius dominate the expansion of gas charging channels at different stages of charging in turn,leading to reductions in pore-throat radius,throat length and coordination number of the pathway,which is the main increase stage of gas permeability and gas saturation.Among which,pore-throats 30-50μm in radius control the increase pattern of gas saturation.In the stable stage,gas charging pathways have expanded to the maximum,so the pathways keep stable in pore-throat radius,throat length,and coordination number,and irreducible water remains in the pore system,the gas phase is in concentrated clusters,while the water phase is in the form of dispersed thin film,and the gas saturation and gas permeability tend stable.Connected pore-throats less than 20μm in radius control the expansion limit of the charging pathways,the formation of stable gas-water distribution,and the maximum gas saturation.The heterogeneity of connected pore-throats affects the dynamic variations of gas phase charging and gas-water distribution.It can be concluded that the pore-throat configuration and heterogeneity of the micro-nanometer pore system control the dynamic variations of the low-permeability(tight)sandstone gas charging process and gas-water distribution features.