Performance Evaluation of Local Cassava Starch Flour as a Secondary Viscosifier and Fluid Loss Agent in Water Based Drilling Mud
The success of any rotary drilling process depends on the type of drilling mud selected to achieve a particular task. The main function of drilling mud is to remove cuttings during drilling process. Viscosity is by far, the most needed property of the drilling fluid to aid it perform its needed task. The viscosity property of the mud helps in well cleaning and also aid in the suspension of drilling cuttings when circulation of the fluid is put on hold. It is important to monitor and continuously adjust the viscosity of the drilling fluid. Series of investigations have been carried out to discover less expensive and high performance viscosifiers. Cassava starch flour with bentonite in controlling viscosity and fluid loss in Water Based Mud (WBM) was investigated in this study. Various mud samples were formulated consisting of different masses of cassava starch flour (2 g, 4 g, 6 g and 8 g) and an additional one being the control bentonite (0 g of cassava starch flour). Fluid loss and rheological tests were carried out to determine the plastic viscosity, yield point, gel strength among others. Results from this investigation showed that, increasing the amount of cassava starch flour in the WBM increased the viscosity of the mud samples due to its swelling ability. Mud samples with cassava starch flour exhibited greater suspension ability (gel strength) of cuttings than that of the control sample with the exception of 6 g and 8 g of cassava starch at 80 ℃ for the 10 minutes gel strength. At the end of the fluid loss test, mud sample with cassava starch flour concentration of 2 g recorded a filter cake thickness of 2 mm while that of 4 g, 6 g, and 8 g gave 3 mm thickness. In conclusion, introduction of cassava starch flour into the mud samples from concentrations of 2 g to 8 g reduced its fluid loss by an average of 8 %. Based on the analyses, starch flour prepared from freshly uprooted local cassava has the potential to improve viscosity and also control fluid loss in WBM.
Keywords: Bentonite, Drilling Fluid, Fluid Loss, Rheology, Water Based Mud (WBM), Viscosifier