Method of Suspender Line Horizontal Well Trajectory Design and Its Applicable Conditions

The trajectory design method of the suspender line takes the slender rod's centerline in the overhanging state as the wellbore trajectory, which can reduce the drag and torque of the drill string effectively but is currently only applied in deep extended-reach well. The suspender line horizontal well trajectory design method is proposed to make the suspender line trajectory broader application. The suspender section established based on the elastic rod theory is regarded as an essential part of the deviated section, and then a mechanical model of the drill string is used for designing the hold section and transition section to meet the requirements of the horizontal well. The trajectories and drag and torque reduction abilities are compared between the suspender line horizontal and conventional horizontal well. The application scope of the suspender line horizontal well is analyzed, and how to control the trajectory in actual drilling is illustrated. The suspender line horizontal well still has the advantage of reducing drag and torque compared with a conventional horizontal well, but the effect of friction reduction will decrease as the increase in friction coefficient, initial deviation angle, and length of the horizontal section, and also increase as the build-up rate of the second transition. The drag and torque reduction capability of the suspender line horizontal well trajectory is lower than that of the conventional suspender line trajectory, but the maximum friction reduction and torque reduction rate can still exceed 30%.