Experimental investigation of tea leaf extract as thinning agent and lubricity enhancer for water-based drilling fluid

This study aims to develop a low-cost and environmentally friendly multifunctional thinning agent for water-based mud (WBM) from tea leaf extract (TLE). Matured tea leaves that are not used for tea production were collected, processed, and boiled in distilled water to release the extracts and prepare the liquid thinning agent. The resultant TLE was characterized using Fourier Transform Infrared spectroscopy (FTIR). Rheological properties were measured at two temperature conditions (35 °C and 70 °C) with varying concentrations of TLE, and the findings were compared with the widely used thinning agent potassium lignite (PL) under all test conditions. In addition, the density, pH, filtration control, and lubricating properties were evaluated under ambient conditions. The findings revealed that TLE, under all test conditions, exhibited better thinning performance than potassium lignite. At the temperature of 35 °C, when used at 1% concentration, TLE reduced apparent viscosity, plastic viscosity, yield point, initial and final gel strength by 23.94%, 21.57%, 27%, 76.99%, and 24.44%, respectively, compared to 12.89%, 16.34%, 8.44%, 39.82%, and 7.94% using the same concentration of potassium lignite. Compared to the ambient condition, the effectiveness of TLE in controlling rheology was found to be more pronounced at higher temperatures. Moreover, TLE at different concentrations significantly improved the filtration and lubricating properties of the mud. The addition of TLE reduced the mud cake thickness by a maximum of 44.44% and the coefficient of friction by a maximum of 40.7%. The comprehensive investigation and comparison with potassium lignite suggest that TLE can be effectively used as a multifunctional, non-toxic, and low-cost thinning agent for water-based drilling fluids.