Prediction of Cuttings-Induced Annular-Pressure Loss in Extended-Reach Wells

Drill cuttings are broken bits of solid material removed from a borehole drilled by rotary, percussion, or auger methods and brought to the surface in the drilling mud. When these cuttings enter the annulus, they have an effect on the drilling fluid rheology and density, which is, in general, quite difficult to evaluate. By introducing an empirical correlation for the rheological properties of cuttings-laden drilling fluids, this study proposes a pressure-loss prediction method for an extended-reach well (ERW). After verifying the accuracy of this method, a case study is considered and a sensitivity analysis is conducted assuming a yield-power law fluid. The results show that an increased concentration of cuttings in the annulus contributes to an increased annular pressure loss. Compared to their effect on the drilling fluid density, cuttings have a greater impact on the drilling fluid rheology. A larger rate of penetration contributes to an increased annular pressure loss. For higher drilling fluid flow rates, the annular pressure loss first decreases and then it increases. In addition, the annular pressure loss becomes higher as the cuttings' particle size decreases and the cuttings' concentration grows.