Is Well Clean Enough? A Fast Approach to Estimate Hole Cleaning for Directional Drilling

Abstract

Abstract In spite of many recent technology improvements in drilling, hole cleaning remains a significant challenge, especially in deviated and horizontal wells. Inadequate hole cleaning can lead to a series of problems such as stuck pipe, fractured formation, high drag and torque, premature bit wear, decreased ROP, logging, and casing and cementing difficulties. Hole cleaning is a complex issue that is affected by many drilling parameters. The major approaches of hole cleaning evaluations include experimental correlations and mechanistic models. But these techniques frequently require complex computations or numerical iterations to get the solutions. In this paper, a set of charts is developed to allow the drilling engineer to quickly estimate the cuttings volumetric concentration in the wellbore. From previous cuttings transport studies, we know that well inclination angle, drilling fluid velocity, fluid rheology, fluid density and drill pipe rotation have the most important effects on hole cleaning. These parameters are divided into several ranges based on their sensitivity to cuttings concentration in the wellbore. The charts are obtained by running a hole cleaning simulator, which is based on a large number of experimental and modeling studies of cuttings transport. The results of the charts are verified by experimental data. The difference between the charts' prediction results and experimental data are within 20%. Instead of solving complex equations in cuttings transport models, drilling engineers are able to quickly estimate the cuttings volumetric concentration by looking up the charts and conducting very simple calculations. This paper is also helpful in guiding the driller to quickly choose proper operational parameters during drilling operations.