Assessing the Rheological and Filtration Loss Control Potential of Selected Plant-Based Additives in Oil-Based Mud

In drilling operations, chemical additives pose environmental concerns during mud disposal. This study evaluated three plant-based additives, namely rice husk (RH), <i>Detarium microcarpum</i> (DM), and <i>Brachystegia eurycoma</i> (BE), in oil-based mud at low-pressure, low-temperature conditions. The mud’s rheological profile followed Herschel Bulkley’s model. With 8 g additive content, RH increased the mud's apparent viscosity (AV), plastic viscosity (PV), and yield point (YP) by 62.5%, 51.25%, and 34.38%, respectively. DM showed higher increases of 200.0%, 195.0%, and 162.5%, while BE exhibited the most significant improvements of 287.5%, 272.5%, and 250.0%. The filtration tests indicated that RH reduced spurt loss and fluid loss volumes by 83.33% and 62.35%, while DM decreased by 82.41% and 47.94%, as BE had the highest reduction of 94.44% and 51.18%. Again, the filter cake thickness of RH, DM, and BE muds increased by 210.29%, 273.53%, and 79.41%, respectively, with permeabilities of 8.90×10<sup>-3</sup> mD, 11.87×10<sup>-3</sup> mD, and 7.35×10<sup>-3</sup> mD. Furthermore, the mud susceptibility to NaCl showed that AV decreased for RH, DM, and BE, while YP decreased significantly. The filter cake thickness and permeability increased by 62.38 and 359.55% for RH, as the DM decreased by 93.80% and 84.37% and the BE by 96.68% and 96.62%, which indicates that RH is more susceptible to NaCl than DM and BE in the mud. Also, these plant-based additives in mud exhibited fragile gel strength and commendable cake characteristics: firm, smooth, and soft/slippery, which make them potentially suitable for oil well drilling.