Rock permeability evolution during cyclic loading and colloid migration after saturation and drying

The study of the influence of cyclic loading on the permeability of rocks has been conducted for a long time. Despite the extensive research database, the actual reasons for the decrease in permeability during loading have not been fully revealed. One of these reasons, as described in the research, is the migration of colloids. This paper presents the findings of a study on colloid migration as one of the causes of permeability degradation in porous rocks under cyclic loading. Permeability is measured by injecting nitrogen at a constant pressure. The cyclic loading program is designed to eliminate the effects of residual deformations, creep, and gas slippage. Direct and reverse nitrogen blowings with increased injection pressure were performed between loading cycles. These blowings promote colloidal movement within the porous medium, blocking pore throats and changes in permeability. A notable aspect of this work is that cyclic testing was performed before and after the saturation and drying procedure. Stuck colloids that cannot be moved by blowing are mobilized during saturation and drying. Comparative tests of cores after saturation and drying confirm the effect of colloid migration on permeability and enable the examination of whether plastic deformations caused permeability degradation in previous loading cycles. Additionally, it was observed that when saturated, new colloids can detach due to the Rehbinder effect, significantly reducing permeability.