ANALYSIS ON THE FRICTIONAL FORCE OF DRILL STRING IN SIDETRACKED HORIZONTAL WELL

Frictional force is the dominant factor that influences drilling operation and limits the further reach of horizontal section. This paper presents a new model for predicting frictional force of drill string in sidetracked horizontal well, with the wellbore elasticity and the effect of pipe joints taken into consideration. The three-moment equation for drill string constrained by elastic wellbore, as well as the numerical solving method is also created. The results show that such factors as WOB, hole curvature, ground elasticity, drill string stiffness and length, and friction coefficient between drill string and wellbore can all affect the magnitude and distribution of friction force, in which hole curvature is a most distinctive factor for sidetracked horizontal well. This method could be used for frictional force analysis in short to medium radius horizontal wells, and as a reference to field drilling practice.