Insights into modelling hydro-chemical interactions in colloid-brine-mineral systems

This study focuses on the interactions between organic (oil) - inorganic (calcite) colloids and porous media, particularly in the context of carbonate reservoirs. The examination pertains to colloidal flow in porous media, which is a crucial aspect in various subsurface fluid flow schemes such as produced water reinjection. We propose an integrated approach, combining surface complexation models, extended DLVO theory, and fluid hydrodynamics. Our model enables us to evaluate the potential of colloids retainment in rock under diverse physiochemical and hydrodynamic conditions. The incorporation of the surface complexation model helps capturing variations in electrostatic forces due to changes in solution chemistry, temperature, or pH, while fluid rate primarily governs the hydrodynamic aspect. Produced water and its 50 times diluted form are chosen as high and low saline carrying fluids, respectively. Our model findings reveal that colloids are prone to deposit on the rock surface in high saline produced water flow at the studied pH (5 and 10) and temperature (20 °C and 80 °C). Considering 50 times diluted produced water, the propensity for colloidal attachment on the surface decreases with increasing both pH and temperature from 5 to 10 and 20 °C to 80 °C, respectively. It is also indicated that within the normal subsurface flow rate ranges in porous media (1×10^-5-1×10^-4 m/s), colloid-brine-rock interactions at close distances between colloid and rock are predominantly influenced by chemical factors rather than hydrodynamics. However, elevating the injection rate to very high values (1×10^-3-1×10^-2 m/s) leads the hydrodynamics to become prominent in the system. The findings set the stage for future research, where the deposition and pore clogging of colloids under the framework of reactive transport models can be investigated. These insights are crucial for planning subsurface water flooding scenarios, evaluating risks associated with colloid-surface-brine interactions, and mitigating potential formation damage.