Synergistic Effects of Polyethyleneimine and Potassium Citrate on Drilling Fluid Properties

Abstract:

Maintaining the optimal properties of drilling fluids such as rheology, fluid loss, and mud cake thickness is crucial for wellbore stability, shale inhibition, and efficient drilling operations. However, the addition of shale swelling inhibitors can alter these properties either positively or negatively, necessitating a thorough investigation of their compatibility and effectiveness. In this study, polyethyleneimine (PEI) and potassium citrate (PC) were used as a shale swelling inhibitor, and their effect on water-based muds’ (WBM) compatibility and rheological properties were investigated and compared to the commercial inhibitor, potassium chloride (KCl). Compatibility tests were conducted to visually examine the water-based drilling fluid after the addition of the shale swelling inhibitors for over 24 hours. Mud density and pH were measured using a mud balance and a pH meter. The rheological properties were then determined using a rotational viscometer by taking readings at 600 rpm and 300 rpm. These are done to observe the flow behavior of the fluids and their abilities to maintain wellbore stability. Further, the fluid loss and mud cake thickness properties of the WBM formulations were determined using a dynamic fluid loss apparatus (HPHT API RP 13B-1) at a pressure of 1000 psi and 90°C. Based on this study, the PEI, PC, and KCl inhibitors were found to be compatible with the drilling fluid as their interactions affected the optical properties but not the physical state. Also, the rheological properties of the WBM were not highly compromised upon the addition of 1 v/v % KCl as a shale inhibitor. However, it was highly compromised upon the addition of 1 v/v % PEI and PC. It was found that cationic PEI interfered with the interactions and structures developed by the anionic components in the drilling fluid. This led to a 16% reduction in viscosity, a 21% reduction in yield point, and a 46% reduction in gel strength. The effects were also most adverse on the fluid loss characteristics of the fluids. In contrast, the use of 1 v/v % PC improved structural integrity and interactions and thus increased the viscosity and the yield point by 16 % and 68 %, respectively. The optimal balance was achieved with the formulation of 0.6 v/v % PEI: 0.4 v/v % PC, which effectively maintained and enhanced the desirable rheological properties of the WBM while maintaining favorable fluid loss control and mud cake formation. The PEI and PC interactions appear to have had a synergistic effect on the overall performance of the WBM.

• Periodical: Key Engineering Materials (Volume 1030)
• Pages: 73-90
• DOI: https://doi.org/10.4028/p-YfL1oy
• Online since: November 2025
• Authors: Siti Qurratu Aini Mahat*, Muhammad Alif Hakeem Mohd Sukeri, Wan Muhammad Afif Hilmi Wan Mohd Nor, Chika Umunnawuike, Augustine Agi Aja, Ismail Mohd Saaid
• Keywords: Compatibility, Fluid Loss, Mud Cake Thickness, Rheological Properties, Water-Based Mud

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