The Effects of Particle Size and Viscosity on Settling Behaviour and Rheological Performance of Isopropyl Laurate Drilling Fluid

Density and viscosity are two major rheological properties that determine the performance of an isopropyl laurate (IPL) ester based drilling fluid. In this study, the effect of barite particle size on the IPL drilling fluid system settling behaviour was investigated using five particle sizes namely-32, 32-45, 45-75, +75μm and the unsieved barite. Stokes’ law of separation theory was employed in the analysis. It was found that smaller barite particle sizes (<75μm) enhances the settling resistance. An ideal barite particle size of-32μm was chosen and used in the subsequent formulations to obtain optimum rheological properties by varying the amount of viscosifier used at 4.0, 10.0 and 20.0g marked as sample (a), (b) and (c). These samples were analysed for their rheology by using the conventional Fann viscometer calibrated using Bingham model. The results showed that sample (b) exhibited the most promising performance based on the plastic viscosity, yield point and gel strength rheological analyses. Moreover, IPL drilling fluid sample (b) showed improve particle suspension ability for more than 78 hours when compared to IPL drilling fluid system prepared using unsieved barite particles. The results suggested that palm oil based isopropyl laurate ester has the potential to be used as based fluid in the ester based drilling fluid system.