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This study is justified by the issues on site in directional well as blowouts, abnormal formation pressure, obstructions in the wellbore, inaccessible target locations caused by an obstacle (for example dome of salt) and the pollution of formations. The objective of this study is to optimize the hole cleaning in directional well with environmentally drilling muds. For this goal, different formulations of "green" drilling muds were tested for 4 inclinations of 10°, 20°, 30° and 40° compared with a horizontal plane for modeling the vertical drill. The drilling muds used are water based with environmentally friendly products; this study tested two biopolymer-based formulations, which are the constants of the experiment. For the specific needs of drilling muds, different products as clay, weighting and potassium chloride were added to the based solution. The microstructure and quantification of the chemical content of biopolymers were examined with SEM-EDS (scanning electronic microscope and energy dispersive X-ray spectrometer). Rheological properties were evaluated with modular rheometer; biopolymer solutions exhibit a non-Newtonian behavior. The samples tested in this study are compliant with API standards. For a suspension of macroscopic particles in the non-Newtonian environment, the sedimentation velocity shows a rapid increase according to the angle value which is well known in macroscopic suspensions under the name of "Boycott effect". The results showed the close link between the composition of the drilling mud and its ability to transport cuttings predictive for directional drilling.

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