Effect of electrostatic interaction on the retention and remobilization of colloidal particles in porous media

We investigate the effect of pH on external hematite colloidal particles entrapment and remobilization by coreflood experiments combined with X ray computed tomography. Suspensions of calibrated hematite colloidal particles were injected into Bentheimer sandstones sample, composed mainly of well-sorted quartz and small clay fraction (up to 1 wt%), consisting mainly of kaolinite. We have found that permeability impairment due to an external cake build-up can be reversed when pH exceeds the point of zero charge of hematite particles. This effect could be successfully interpreted by the switching of the surface charge of hematite particles from positive to the negative, similar to the rock surface. The experimentally verified pH-controlled electrostatic retention and remobilization technique can be extended to other colloidal particles, having pH-dependent surface charge, including natural clay minerals in hydrocarbon and geothermal reservoirs. Therefore, varying pH of injected fluid can be applied for targeted external cake build-up and transportation of colloidal particles within a reservoir.