Analysis of the effects of drilling fluid viscosity on hole cleaning in directional well drilling

Hole cleaning is one of the most important aspects of extractive drilling operations. When drill cuttings combine with drilling fluids, cutting bed gel is created, which becomes extremely challenging to remove while drilling. One of the functions of drilling fluid when the flow is static is to maintain the drill bits' suspension. However, the settling of drill bits makes this nearly impossible. In this paper, the influence of fluid viscosity on hole cleaning performance was critically studied through a series of laboratory experiments. The effects of different viscosity levels on hole cleaning were investigated. This paper evaluated the use of lecithin and carboxymethyl hydroxyethyl cellulose (CMHEC) as a viscosifier and fluid loss agent in oil-based drilling fluid. The rheological properties of the formulated drilling fluids were determined at various temperatures according to the API 13B-2 specifications in order to identify the most suitable mud type for high-temperature drilling operations. From this study, it was discovered that Formulation B has the best rheology, with a plastic viscosity (PV) of 12, 7, and 7 cP at 30, 40, and 50 °C, respectively, while its yield point (YP) was found to be 30, 24, and 16, respectively. These values were compared with the generic oil-based formulation (A), which had a plastic viscosity (VP) of 43, 39, and 22 cP at 30, 40, and 50 °C, respectively, while its yield point (YP) was found to be 38, 20, and 26, respectively. The findings show that formulation B has a significant resistance to high temperatures, which means that it can be applied to drilling operations in reservoirs with high temperatures. It is more environmentally friendly. Furthermore, this paper explores the implications of the results in terms of the efficiency of hole cleaning and the drilling process relative to the viscosity of oil-based drilling fluid. This paper concludes by providing suggestions for improving drilling efficiency through the selection of an appropriate drilling fluid viscosity.