Study On The Method Of Improving Cuttings Transportation Efficiency In Extended Reach Well Annulus

The cleaning of cuttings bed is one of the hot issues in the area of extended reach wells drilling technology.The forming of cuttings bed in the process of extended reach well drilling can cause many safety problems to drilling construction.Thus,how to improve the transportation efficiency for cuttings in extended reach well annulus is studied in this thesis.Different cuttings particles are studied.The force analysis of cuttings in different well sections is performed,the mechanical model is created,and the critical rolling velocity and the critical lifting velocity of cuttings are calculated.The transportation rule of cuttings is found.The results indicate that cuttings bed more easily forms in well section when the deviation angle is 50 degrees.Moreover,the detail study on the forming process of cuttings bed is performed,with Lagrange's and Euler's methods.The results indicate that the particles with larger diameters or bigger wall friction are more easily deposited to the well wall.In the meantime,transportation efficiency are analyzed in aspect of the deviation angle,the annular velocity,the rolling velocity of drilling pipe and the eccentricity of drilling pipe.The results are consistent with the actual operation rule.To improve the cleaning efficiency of cuttings bed,a cuttings cleaner is designed.The cleaner removes the cuttings bed with the mechanical and hydraulic function.The effect of cuttings cleaner on the annular flow field is simulated using FLUENT,and the optimum spacing distance of the new cuttings cleaner in different well sections is calculated.The results indicate that the new cuttings cleaner has a good performance.