Better Hole Cleaning In Highly Deviated Wellbores

Abstract

Many drilling problems (lost circulation, hurdle in running casing, poor cement jobs, high torque and drag and the necessity of re-drilling and, mechanical stuck caused by cutting accumulation in the wellbore) can be avoided by good hole cleaning during drilling operation especially in directional wells.In this experimental work, the cutting transport ratio (CTR) in hole inclined (60 degree) from vertical was estimated by using three values of drilling mud viscosities, three annular velocities, two types of cuttings size and two rotation speed of inner pipe (RPM). Note that the rig consisted from PVC outer casing 4 1/2 inch as OD diameter and inner drill pipe 2 inch as OD diameter.The experimental results showed that the Cuttings Transport Ratio (CTR) increased with increasing the annular velocity and better hole cleaning which obtained from the third velocity (3.247 ft/sec) for all cases. Moreover, increasing the mud yield point (YP) helped to improve the cuttings transport ratio; however increasing the mud yield point slightly affected with increased the annular velocity. Furthermore, it was noticed that the rotation of drill pipe (RPM) is one of the most important parameter for cuttings removal especially in laminar flow and transition flow. The cuttings sizes 1.7 mm are also easier to transport than 3.35 mm cuttings sizes for all cases except low yield point (YP).