Influence of polypropylene beads and sodium carbonate treated nanosilica in water-based muds for cuttings transport

Abstract

The drilling for hydrocarbons from oil and gas wells requires efficient drilling fluid and cutting-edge drilling technology. Furthermore, the removal of rock cuttings from oil and gas wells while drilling is a vital task of the drilling fluid, particularly in large-angle wells and long-range drillings. The rock cuttings if not transported to the surface effectively can result in severe costly drilling problems of drag and torque, pipe sticking, faster bit damage, etc. This research suggests a new method that applies polypropylene beads (PP) and silica nanoparticle (NS) treated by sodium carbonate (Na2CO3) to enhance the cuttings transport efficiency (CTE) of water-based mud (WBM). Tests were carried out in laboratory-scale cuttings lifting rig simulator equipped with a 20-ft. Long annulus, a 2.75-in. ID outer acrylic pipe, and an inner drill pipe of 1.05-in. OD. Six different 10 ppg weighted mud samples were formulated and coded mud nos. 1–6 using PP beads and Na2CO3 treated NS concentrations. Four cuttings sizes in the range between 0.4 and 4.0 mm at various hole angles (0°, 30°, 60°, and 90°) without pipe rotation were evaluated using a constant flow rate of 5.13 L/s. The results of rheological characterization using Herschel-Buckley model showed that all the mud systems are shear-thinning as the flow behaviour index ranged between 0.50 and 0.60. The fluid consistency parameter of the WBM indicates that the addition of PP beads and NS concentrations decreases the viscosity of the WBM. Also, the viscosity, yield point, gel strength, and filtration parameters of the WBM were decreased when the PP beads and NS concentrations were introduced before and after thermal aging experiments. This interprets the thinning nature of the mud systems. However, when these products were applied to lift cuttings to the surface, the lifted cuttings increased. The optimum mud system using Bingham plastic expression was found at mud no. 6 (BM-PP8-NS1) containing apparent viscosity of 30.5 cP at a shear rate of 1022 s?1, plastic viscosity of 13 cP and a yield point of 35 lb/100 ft2 at 78 °F. Cuttings size and hole angles seem to wield significant influence on CTE as the smallest cuttings (0.4–1.4 mm) were easier to be lifted in the vertical hole (0° angle), while the largest ones (2.8–4.0 mm) were the most lifted in the horizontal section (90° angle). The findings of this study can help for a better understanding of the mud performance of PP beads and Na2CO3 dispersed NS mixture for cuttings transport in a wellbore.