Evaluation and Treatment of Cement Contamination in Water Based Mud

Abstract

Drilling mud is susceptible to contamination, particularly from cement, yet monitoring its characteristics and implementing control and remediation strategies is critical for its performance in safe and cost-effective drilling operations. This study presents an experimental investigation into the evaluation and treatment of cement contamination in Water Based Mud (WBM). Four mud samples were prepared and three were contaminated with 4g, 8g and 12g of cement. A chemical treatment using 6g of sodium bicarbonate was applied as a remedy for contamination. The Rheological properties, mud pH and mud densities of the contaminated and treated Water Based Mud at temperatures of 35°C, 55°C, 75°C and 95°C were determined. Furthermore, the elemental composition of samples of contaminated and treated Water Based Mud was determined using an X-Ray Fluorescence Spectrometer. From the results obtained the mud density increased with a rise in cement concentration for both contamination and treatment with the exception of 8g cement concentration at 75°C and 95°C and 12g cement concentration at 55°C and 75°C where a decrease was observed in the treatment process. The yield point and 10second gel increased for both contamination and treatment process. In contrast, the 10minute gel decreased for both contamination and treatment process. With some exceptions, increasing cement concentration resulted in a decrease in plastic viscosity, whereas treatment with sodium bicarbonate resulted in an increase with some exceptions. The mud pH for the contamination process increased as cement concentration increased, while treatment only marginally increased it with exception of 12g at 75°C and 95°C where a decrease was observed. Sodium bicarbonate treatment improves stability by decreasing excessive calcium and lime contamination from cement, reducing pollutants and enhancing the pH stability of the drilling mud. Additionally, results from the mud characterization indicates a higher percentage of 17.962% lime (CaO) for cement contamination and lower percentage of 15.710% lime (CaO) for treatment with sodium bicarbonate which agrees with literature for the treatment process.