砂岩孔隙介质内天然气运移的微观物理模拟实验研究

Physical Simulation Experiment of Gas Migration in Sandstone Porous Media

采用真实的砂岩微观模型,通过与实际地质状况较为相似条件下的气驱水运移实验模拟天然气在砂岩孔隙内的二次运移,直接观察了天然气在砂岩孔隙、喉道内运移的过程和特征,在此基础上,分析和探讨了真实砂岩孔隙介质中天然气的微观运移机理。研究发现,天然气运移路径的形态通常迂回曲折,表现复杂的分支状特征,而且气体只沿毛细管阻力最小的运移路径向前运移;受真实砂岩孔隙结构的非均质性和运移动力变化的影响,天然气运移的速率不均一,呈现出跳跃式的运移方式;在孔喉比相差较大的亲水介质中,气体的卡断现象较为普遍,卡断增加了气体运移的阻力,对天然气运移十分不利;外界突发性的振动能够增加天然气运移的有效性。

Based on true sandstone micro-model, an experiment of gas-drive-water was performed to simulate the secondary migration in the sandstone porous media. The migration course and characteristics of gas in pores and throats are observed. Furthermore, the micro-mechanisms of gas migration are analyzed and discussed. It is found that the migration pathways are usually flexuous and look like branches of tree. Gas always migrates forward along the limited pathway where the capillary force is lowest. The migration speed is inhomogeneous because of the inhomogeneous porous structure and the change of migration drive. The snap-off is prevalent in water-wet media whose ratio of pore and throats is large. The snap-off is disadvantageous for gas migration because it will increase the migration resistance. It is also observed that a sudden shake can promote gas migration.