A Review of the Rheological Effects of Power Law Drilling Fluids on Cuttings Transportation in Non-Vertical Boreholes
Cuttings transportation during in non-vertical boreholes is necessary for oil and gas wells. Adequate cuttings removal from a well in drilling is critical for cost-effective drilling as high annular cuttings buildup often leads to high risk of stuck pipe, reduced rate of penetration and other impediments to standard drilling and completion procedures. This study investigates how rheological parameters influence the removal of cuttings in non-vertical boreholes. It contributes to work already done to ensure efficient hole cleaning process. In this study, the rheological parameters examined were the flow index (n), consistency index (K), plastic viscosity (PV), mud yield point (YP), YP/PV ratio, apparent viscosity and effective viscosity. Fifteen mud samples, three annular velocities (3.82, 2.86 and 1.91 ft/sec) and three hole angles (30 o, 45o and 70o) were considered. An Excel Spreadsheets program was used to determine the parameters. The results of this study show that, higher annular mud velocities are required for efficient hole cleaning in directional wells than in vertical wells. Increasing values of YP, YP/PV ratio and K promote effective cuttings transport while the value of n should be low. Effective and apparent viscosities also should be high.