Pore Scale Examination Of The Impact Of Porous Media Morphology And Particle Hydrophobicity On Colloid Retention And Remobilization Behavior

Abstract

The understanding of colloidal retention properties in multiphase systems is essential to a multitude of industries like oil extraction and groundwater recharge. A pore-scale understanding of the dynamics of colloid retention behavior on different pore geometries can heavily influence the efficiency of these operations. The main goal of this study is to investigate the impact of pore geometry, and particle hydrophobicity on colloid retention on different interfaces. Three different colloid suspensions were prepared, a hydrophobic suspension, a hydrophilic suspension, and a mixed suspension that is half hydrophobic colloids and half hydrophilic colloids. The three suspensions were injected using a pump syringe into Polydimethylsiloxane (PDMS) micromodels of three different geometries each that were initially filled with air. Resulting in nine experimental runs. After injection, the pump was set to withdraw the fluid inside the micromodels to examine saturation degradation under pore clogging conditions. Findings from the flooding phase of the experiments demonstrate that significant colloid retention occurs starting from 60% saturation at the least. As the existing gas phase within the media acts as a blocking agent against colloid attachment. The blocking effect is due to colloids mainly retaining on the Sand-Water-Interface (SWI), while having insignificant retention on the Gas-Water-Interface (GWI) and Gas-Solid-Interface (GSI). A higher redundancy in flow pathways in a pore geometry results in achieving significant retention at lower saturation levels. While the chemical heterogeneity of the mixed particle suspension resulted in it achieving significant retention at higher levels of saturation compared to the hydrophobic and hydrophilic suspensions. While findings from the withdrawal phase indicate that multiphase flow achieves insignificant removal of colloids from the system. Which was due to throat clogging and pore filling colloids becoming irremovable. Additionally, a lack of flow pathway redundancy causes expanding gas bubbles to be entrapped within the media, thereby hindering saturation degradation.