Impact of Pore Morphology on Colloid Migration at Variable Saturation Levels of Natural Porous Media

Abstract

The migration of colloids within porous media has a critical impact on many important industrial processes such as oil production and groundwater recharge. Colloids can clog the pore space and hence impair the permeability of fluids which adversely impacts the efficiency of fluids movement through such media. Therefore, understanding the mechanisms of pore clogging at the pore-scale is critical to develop efficient remediation methodologies for permeability reduction at different physio-chemical conditions. To study pore clogging at a pore-scale, microfluidic chips were fabricated to mimic geometries of natural porous media extracted from tomographic scans of sand packs. A colloidal suspension was injected in three phases into the system. The phases consisted of an initial imbibition of the suspension, followed by drainage of the suspension from the system, and finally, a second imbibition. During each phase, a series of images are taken of a section of the porous media. Findings reveal that pore-clogging considerably impairs saturation levels of the porous media through blocking the flow from reaching the gas phase within the system. Considerably increasing the time the gas is trapped in the pore-space, which in turn develops higher irreducible water saturation. This was also observed in the case of drainage of the colloidal suspension from the pore-space where colloids blocked pathways of the gas phase and prevented its migration through the pore space. In contrast, the migration of colloids was also impacted by the presence of the gas phase. Gas provided a clogging surface while forcing colloids to migrate through the pore space and accumulate at other pores. This implies that gas phase presence within a low porosity system can increase pore clogging at a significant rate. This is also supported by the short period between the clogging of two pores and the clogging of a dozen pores within the observed system.