AN EXPERIMENTAL INVESTIGATION OF THE EFFECTS OF CUTTINGS SIZE ON MUD RHEOLOGY

Abstract

Effective hole-cleaning is vital for a successful drilling operation and has significant effect on optimizing factors such as penetration rate, bit optimization and well stability. Efficient transportation of drilling cuttings are dependent on factors such as fluid properties and rheology, cuttings size and shape, fluid velocity, cuttings concentration, cuttings transport velocity and rate of penetration. This experimental work examined the effects of cutting sizes on drilling fluid rheology. To achieve this, two fresh samples of mud were prepared and the rheological properties were analyzed at different temperature ranges representing the operating conditions of most Niger Delta wells. A mesh analysis was carried on dried fresh drill cuttings from the Anieze North Field and dried cuttings taken from the laboratory and two samples were selected at ASTM#40 and #18. 10 % of these cuttings samples were added to each mud sample and the rheological properties were measured at similar temperature ranges as the original mud samples. The results gotten shows that at the various temperature ranges, mud contamination with smaller drill cuttings size (ASTM #40=400um) showed a better performance than the larger particles. The mud rheological properties (viscosity, yield point, YP, plastic viscosity, PV and density) measured at different temperatures showed a remarkable non-linear behavior as shown in the results. KEY WORDS: Cuttings Size, Drill Cuttings, Mud Contamination, Mud Rheology, Temperature