Hole cleaning and hydraulics

Abstract

Cuttings transport and efficient hole cleaning remains a vital challenge when planning and drilling vertical, deviated, high angle and extended reach wells. Optimization of cuttings transport depends on so many factors- hole angle, cutting size, drill string rotation, drill pipe eccentricity, optimization of bit hydraulics, etc. As to date, most existing hole cleaning models and charts have been derived for wells with angles greater than 25 degrees, these models use charts developed from the original physicalbased model. Hole cleaning in vertical holes have been evaluated by calculating the carrying capacity and most hole cleaning charts do not apply to near vertical and vertical wells. This thesis will study the different factors that affect the efficient cleaning/transport of cuttings and bit hydraulics during drilling. Furthermore, a model is developed to bridge the gap between existing vertical and deviated models for predicting hole cleaning. A single model is proposed which can be used in predicting hole cleaning in both vertical and deviated wells. hole cleaning charts are also developed to be used in conjunction with existing hole cleaning charts in the field. Also, the effect of washout is investigated in vertical wells. Corrections factors are proposed for correcting the critical flow rate. Finally, the predicted models are validated using field data and hole cleaning charts are produced.