DLVO-based prediction of critical pH for fines migration in sandstone reservoirs

Fines migration is a formation damage mechanism that occurs in sandstone formations due to the incompatibility between injected fluids and in situ fluids during various operations such as water flooding, drilling, and completion. Fines migration can lead to production problems such as pore blockage and reduced permeability. Parameters such as salinity, pH, and flow rate affect the forces between fines and the rock surface, potentially triggering fines migration. Therefore, predicting the conditions that lead to fines release and migration is critical for ensuring safe operations. Enhanced oil recovery methods, such as low-salinity water injection and alkaline flooding, alter the salinity and pH within the formation, affecting the electrostatic interaction forces between fines and the rock surface. Hydrodynamic forces also influence fines release. Therefore, predicting the initiation of fines migration requires considering and analyzing all these forces. In this work, a modified method based on DLVO theory was developed to predict the critical pH for fines release. The model estimates the onset of fines migration by evaluating electrostatic and hydrodynamic repulsive and attractive forces. For example, the model predicted critical pH values of 8 and 10 at salinities of 0.2 M NaCl and 0.25 M NaCl, respectively. Several core flooding tests were conducted to measure the critical pH for fines release, validating the developed model. The experimental observations showed good agreement with the model, with an error of approximately 13% in predicting the critical pH. The developed approach enables the identification of optimal brine conditions to mitigate fines migration and formation damage, which is a significant finding for enhanced oil recovery and production operations.