Improving The Efficiency Of Transportation Of Cuttings In Wellbore - Experimental Investigations On Critical Rolling And Lifting Velocities
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Poor hole cleaning have dire consequences and as a result, special efforts and considerations are planned in drilling operations to avoid complications or hole cleaning issues. Drillers have often been tasked by finding the optimum drilling and rheological parameters for proper hole cleaning. Enormous breakthrough and improvement on hole cleaning has been observed in the oil and gas industry, thanks to past decades of efforts channeled through research and studies on the understanding of hole cleaning. Nevertheless, hole cleaning still pose a big challenge in many wells today, mostly as a result of non-compliance on use of optimum drilling and rheological parameters, as well as uncertainty of formation type drilled. Although significant amount of works and time have been devoted on hole cleaning by different authors, not so much resources have been dedicated to the critical velocities controlling mode of cuttings transport in wellbore. This thesis work focuses on improving the efficiency of transportation of cuttings in wellbore, with major emphasis on the critical velocities of transportation of particles. A literature review on hole cleaning and critical velocities was carried out by the author. Factors affecting hole cleaning and critical velocities of transportation of cuttings was also highlighted in this work. The author reviewed different models for calculating critical rolling and lifting velocities. Analyses of selected model were performed prior to starting the experimental work. Experimental work on critical velocities was performed on a flow loop and the results of the experiments were compared with the theoretical results. From the analyses, the author concluded that the theoretical model could be improved by taking into account plastic forces acting on cuttings particles.