弹性波作用下渗流多孔介质微粒运移分析

Transport of fine particles in saturated porous media under elastic waves

弹性波作用下渗流多孔介质微粒运移分析是对目前静态流体或稳态多相渗流中微粒运移/捕集的补充,通过分析弹性波对微粒剥离运移捕集过程的影响,建立弹性波作用下微粒运移模型,得到对微粒运移效果和储层物性变化的影响规律。由推导得到的弹性波作用下微粒剥离临界速度可知,当微粒与孔喉半径的比值越小时弹性波导致的振荡附加力影响越大,临界速度与流体粘度、微粒/孔喉半径比成负相关,与基质胶结程度、结构力、微粒半径、微粒密度成正相关。弹性波作用下微粒运移模型需同时考虑多孔介质渗流速度的变化,此时微粒剥离释放速率增加,但随着波衰减和时间延长而降低,微粒在孔隙表面沉积滞留速率先上升后下降,喉道堵塞的速率有所上升,说明弹性波作用下微粒的剥离和悬浮能力增加,但亦增加了微粒在微细孔喉"架桥"堵塞的可能性。研究结论对岩石物理学和工业化波动处理涉及的储层物性研究具有一定指导意义。

The research on the transport of fine particles in saturated porous media under elastic waves is complementary to the current study of particle migration in static multi-phases or steady-state seepage flow. Considering the influence of elastic waves on particle detachment-migration-capture process, we established a modified model of fine particle transport under elastic waves, and analyzed the changes of particle migration and physical properties in reservoir. Furthermore, the critical velocity of particle detachment from the pore surface under elastic waves was derived, which was found negatively related to the fluid viscosity and particle/pore-throat radius ratio, but positively related to th,e degree of matrix cementation, structural force, particle radius and density. It also shows the smaller the particle/pore-throat radius ratio is, the stronger the impact of wave imposing on particle detachments is. The model also considers the changes of flow rate under waves. When the detachment rate of fine particles increases, the retention rate of deposition would increase firstly and then decline with wave attenuation and time extension, and the retention rate of throat-blocking would rise. It demonstrates that the elastic wave not only leads to an enhancement in the capacity of particle detachment and suspension, but increases the possibilities of ＂bridge＂ blocking in micro throats. This study might be useful to the exploration on rock physical properties in petrophysics and industrial wave application.