Optimization of Hole Cleaning and Cutting Removal in Vertical, Deviated and Horizontal Wells

Abstract

As measured depths and displacements in horizontal and extended-reach (ERD) wells increase, good hole cleaning and cuttings removal is essential to avoid associated problems with poor hole cleaning like pipe sticking, abnormal torque and drag, drop in ROP and etc. So far, some methods and models have been developed that can assist in finding the minimum flow rate required to efficient removal of the cuttings during drilling operation. One of them is Larsen’s model that predicts minimum flow rate for cuttings removal from 55 to 90 degrees of inclination. Another model, Moore’s correlation, is used to find the slip velocity of the cuttings in vertical wells (0 degree inclination). This paper presents a detailed combination of Larsen’s model and Moore’s correlation to predict and calculate the minimum flow rate for cuttings removal for all range of inclinations namely from 0° to 90°. The resultant flow rate is compared with flow rate that maximizes the bit horsepower or bit jet impact force (optimized flow rate). If the flow rate for cuttings removal is less than the optimized flow rate, the latter is selected. But if the flow rate for cuttings removal is higher than the optimized flow rate, then drilling fluid rheological properties should be changed until the optimized flow rate becomes higher than the flow rate for cuttings removal. This procedure gurantees achievement both optimized drilling hydraulics and good hole cleaning. To illustrate the usability of this approach whitin all inclination ranges, three points in vertical, deviated and horizontal parts of a horizontal well are chosen and the optimization procedure performed and presented.