Comprehensive Assessment of Inorganic Salt Inhibitors for Clay Swelling Mitigation in Drilling and Completion Operations

Abstract

Abstract Clay swelling in geological formations presents a substantial challenge during drilling and completion operations, resulting in formation damage and decreased wellbore productivity. To address this issue, various clay swelling inhibitors have been incorporated into drilling and completion fluids. Inorganic salts, such as KCl, CaCl2, NaCl, and MgCl2, are frequently employed for their inhibitory properties. This study aims to consolidate and provide a comprehensive overview of the inhibitory potential of these inorganic salts by concurrently examining multiple salts at various concentrations (1%,3%, 7%, and 10% wt%). To assess the swelling inhibition capabilities of these inorganic salts on sodium bentonite clay, we utilized a dynamic linear swell tester. The linear swelling test was extended to a duration of 120 hours to simulate conditions in extended-reach wells, ensuring a comprehensive evaluation. Additionally, we conducted capillary suction timer (CST) tests, analyzed zeta potential, and examined particle size and sedimentation patterns of salt solutions prepared at different concentrations. Our findings indicate a clear inverse relationship between clay swelling and salt concentration, with higher concentrations leading to reduced swelling. Notably, the lowest swelling was observed in KCl brine after 100 hours, while CaCl2 salt reached a plateau across all concentrations. Zeta potential analysis revealed that salts mitigate the repulsion between clay particles, potentially promoting flocculation. Particle size analysis confirmed the enlargement of clay particles in the presence of salts. Stability tests further demonstrated sedimentation of clay particles within the first 5 hours in salt solutions, with varying settlement patterns observed over 24 hours. This comprehensive investigation into the swelling inhibition potential of different salts provides valuable insights for both academia and industry. It aids in designing drilling fluids and completion brines with suitable salts that efficiently inhibit swelling in a shorter time and at lower concentrations with minimum formation damage.