Optimizing Hole Cleaning Using Low Viscosity Drilling Fluid

When drilling for hydrocarbon, one most important thing to recognise is the bottom hole cleaning. Poor well hydraulics will lead to poor bottom hole cleaning. Several suggestions have been made in years back to prevent cuttings from falling to the lower side of the borehole thereby forming cutting bed. One of the main functions of drilling fluids is suspending the drill cuttings when the flow is static. But having met this criterion, cutting beds are still formed. The settling down of drill cutting makes this function of drilling fluid almost impossible. The formation of cutting bed due to the inability of the drilling fluid to establish this function brings about the objective of this research work. The main objective is to optimize hole cleaning using low viscosity drilling fluid and also to evaluate the effect of high flow rate on low viscous drilling fluid with respect to hole cleaning. This was carried out by a laboratory formulation of synthetic drilling fluid and the viscosity of this formulated fluid was varied from low to high. Tests for its rheological properties were carried out using Fann viscometer and the data obtained were recorded. The plastic viscosity and yield point were calculated from existing equations. The values for their rheological properties were tested using an existing hole cleaning model to determine the time taken for each of the drilling fluid to erode a 5 inches cutting bed. The fluid with an excellent hole cleaning value was also determined (CCI > or =1) and at optimum flow rate obtained for an 8-inches open hole section. When the values of their rheological properties were tested in the hole cleaning models, it was observed that, low viscosity fluids can erodes a 5 inches cutting bed height faster than the other drilling fluids and achieved an excellent hole cleaning value at an optimum flow rate when tested with the second model.