Experimental investigation of cuttings transportation in deviated and horizontal wellbores using polypropylene–nanosilica composite drilling mud

Abstract

The experience acquired in the field showed that poor cuttings transportation results in several drilling problems, such as pipe sticking, undue torque and drag, hole–pack off, or lower than projected drilling performance. In this study, complex water–based mud (WBM) formulated with polypropylene–nanosilica composite (PP–SiO2 NC) and partially hydrolyzed polyacrylamide (PHPA), a drag–reducing agent were used to examine cuttings transferring efficiencies (CTEs). The examination focused on the impact of diameters of cuttings (between 0.50 and 4.00 mm), hole angles (45, 60, 75, 90°), mud velocities (between 0.457 and 1.80 m/s) and different concentrations (0.4, 0.5, 0.8 and 1.2 ppb) of PP–SiO2 NC and PHPA. A field–oriented cuttings transport flow loop of dimensions (69.85 mm × 26.67 mm, 6.07 m–long annulus) was constructed to determine the CTEs of the drilling muds. Results showed that smallest cuttings were easiest to remove when mud velocities of 0.457, 0.630, 0.823 and 0.960 m/s were used, but when the velocity increased to 1.80 m/s, the transport of largest cuttings became the easiest. Results also confirmed that PP–SiO2 NC muds are more capable of transferring cuttings than PHPA mud samples with or without pipe rotation speed due to increased colloidal forces that increase the interaction between cuttings and PP–SiO₂ NC particles. Rotation of drill pipe and an increase in mud velocity will effectively increase the drag effects, which will lead to increased CTE. Hole angle 45° was the most difficult inclination in the cuttings transport process due to the higher settling tendency of cuttings on the low side of the hole. The application of complex WBM with PP–SiO2 NC showed promising attributes in a cuttings transport process.