No abstract

Inadequate wellbore cleaning contributes to several major drilling problems such as; increase in torque and drag that can limit the reach to target, mechanical pipe sticking, difficulties in casing and cementing and logging operations that can increase well cost significantly. Meanwhile, effective removal of drilled cuttings from the wellbore improves penetration rate and drilling efficiency. Herein, water-based mud was formulated with nanosilica to enhance cuttings and solid particles transport from the wellbore to the surface. Four different weight percent concentrations of nanosilica (0.001, 0.003, 0.005 and 0.01 wt.%) at three different flow rates in litres/seconds (0.4, 0.6 and 1.0) and cutting size (small, medium and large) were used to investigate the formulated water-based mud lifting capacity of the drilled cuttings and other solid particles. Thereafter, the hole cleaning efficiency of the water-based mud containing nanosilica was compared to conventional water-based mud. The results show that nanosilica water-based mud influences the cuttings lifting capacity. The addition of the nanosilica concentrations to the water-based mud enhances the viscosity, thereby increasing the muds carrying and circulating capacity. Moreover, nanosilica water-based mud displays mud stability that will stabilize the wellbore and prevent the intrusion of formation fluids into it when compared with the conventinal water-based mud. The effect of cuttings size on the wellbore cleaning is minimal. The large cuttings size shows a lower degree of cuttings transportation compared with the small and medium cutting size. The small cuttings size has higher cuttings recovery to the surface. Finally, though increase in flowrate leads to more cuttings recovery, there is every tendency that much fluid flow rate will cause an increase in frictional pressure losses and equivalent circulating density, high pump pressure requirement and potential hole erosion.