Optimizing Drilling Fluid Performance with Green Inhibitors

The compatibility and rheological properties of water-based drilling fluids (WBM) are crucial for ensuring wellbore stability and efficient drilling operations. However, the addition of shale swelling inhibitors can significantly alter these properties, necessitating a comprehensive evaluation. This study examines the effects of formulated shale inhibitors, polyethyleneimine (PEI) and potassium citrate (PC), on WBM properties and compares them to the commonly used potassium chloride (KCl). Compatibility tests were performed by visually assessing WBM after the addition of inhibitors over 24 hours. Mud density was determined using a mud balance, while pH was measured with a pH meter. Rheological properties, including apparent viscosity, plastic viscosity, yield point, and gel strength, were evaluated using a rotational viscometer at 600 rpm and 300 rpm. These measurements help determine the flow behavior of WBM and its ability to support wellbore stability. Additionally, fluid loss and mud cake thickness were determined using a dynamic fluid loss apparatus. The results demonstrated that PEI, PC, and KCl were compatible with WBM, as their interactions affected only the optical properties without compromising the physical state. However, the rheological properties were significantly influenced by PEI and PC addition. The cationic PEI disrupted the interactions of anionic components in the drilling fluid, reducing viscosity by 16%, yield point by 21%, and gel strength by 46%. Conversely, PC improved structural integrity and interactions, increasing viscosity by 16% and yield point by 68%. The optimal balance was achieved with 0.6 v/v% PEI: 0.4 v/v% PC, effectively maintaining desirable rheological properties while ensuring favorable fluid loss control and proper mud cake formation. The interaction between PEI and PC exhibited a synergistic effect on overall WBM performance.