Nanosilica-enhanced water-based drilling mud for hole cleaning in inclined wells

Abstract

Inadequate hole cleaning often leads to challenges in drilling operations such as poor cuttings lifting that causes pipe sticking, losing tools, and difficulties in liner/casing placements. Designing a drilling mud with improved rheological properties that are facing minimal degradation under high temperature conditions would be a better solution to increase cuttings transportation efficiency. Static tests which included rheological properties, fluid loss, and fluid flow behaviour of the drilling mud with and without nanosilica were examined according to API standards. This study also involved dynamic tests which investigated the performance of nanosilica in degraded and non-degraded water-based drilling muds to improve cuttings lifting in inclined drilling operations. This research uses a jacketed mixing tank with a capacity of 200 litres and an operating temperature of up to 482? (250?) to degrade drilling mud with and without nanosilica before testing them at ambient condition in a flow loop. Simulated cuttings of irregular shape and sizes ranging from 1.4 to 4.0 mm were used. Different inclination angles (0, 30, 60, and 90°) have been considered in the dynamic tests with and without pipe rotation (120, 150, and 180 rpm) to simulate the drilling conditions in a wellbore. It was found that the presence of nanosilica has increased the cuttings transportation efficiency (CTE) in all experiments. Results indicate that the presence of nanosilica in mud increases the colloidal interactions with cuttings and contributes to improvements in CTE by 30.8 to 44%. At elevated temperatures, 12 ppg muds performed better than 9 ppg muds. However, after adding the optimum concentration of nanosilica of 1.0 ppb (by weight), the CTE improvement for 9 ppg muds was higher than that for the 12 ppg muds. The presence of nanosilica improves the CTE at elevated temperatures because the distribution of nanosilica in the mud is able to withstand the heat in high temperature conditions thus improving CTE when comparing to mud without nanosilica. The introduction of nanosilica in water-based drilling fluids shows promising results in hole cleaning process which will enable them to be used in extended reach drilling operations.