考虑接触角滞后性多孔介质内非混相驱替研究

An Investigation on the Immiscible Displacement in Porous Media With Contact Angle Hysteresis

接触角滞后性表现为前进和后退接触角不同,其是润湿表面上两相流动中的重要现象.该文采用改进的伪势格子Boltzmann(LB)两相模型,并与几何润湿边界条件相结合,研究了接触角滞后性、毛细数以及几何结构对多孔介质内不混溶驱替过程的影响.数值结果表明:单渗透性多孔介质内相同毛细数下,保持后退角一定,驱替效率随着前进角的增大而增大;疏水和中性接触角滞后性窗口中,驱替效率随滞后性窗口大小增大而减小.在亲水接触角滞后性窗口中,接触角滞后性大小作用不明显;同等窗口大小下,所有选取的亲水滞后性窗口驱替效率大于中性滞后性窗口,中性滞后性窗口驱替效率大于疏水滞后性窗口.单渗透性多孔介质内相同接触角滞后性条件下,毛细数C_(a)越大,驱替相在多孔介质内的指进现象越明显,驱替效率越小.另外,双渗透多孔介质中驱替相更易在高渗透性区域流动并率先突破边界,驱替效率较单渗透性显著下降.

Contact angle hysteresis is the difference between advancing and receding contact angles,and makes an important phenomenon in 2-phase flow on a wetting surface.An improved interparticle potential model was coupled with the geometrical formulation contact angle scheme to investigate the effects of the contact angle hysteresis,the capillary number,and the geometry structure on immiscible displacement issues in porous media.The numerical results show that,the displacement efficiency increases with the receding angle for a given capillary number and a given advancing angle.On the other hand,for 3 types of contact angle hysteresis windows:hydrophilic,neutral and neutral hysteresis windows,the displacement efficiency of hydrophilic hysteresis windows is higher than that of neutral and hydrophobic conditions.Furthermore,in hydrophobic and neutral contact angle hysteresis windows,the displacement efficiency decreases with the hysteresis window magnitude.In the same contact angle hysteresis for single-permeability porous media,a larger C_(a) number makes the viscous fingers more obviously,so the displacement efficiency decreases with the capillary number.For the dual-permeability porous media,it is easier for the displacing phase flows to finger in high-permeability areas and break through the boundary first.As a result,in the high-permeability area the displacement efficiency is significantly higher than that in the single-permeability area.The heterogeneity of dual-permeability porous media will enhance the influence of contact angle hysteresis on the distribution of the displacing or displaced fluid,but limit the influence on the displacement efficiency.