Study On Directional Drilling Coupling Dynamics Based On Drill String Rotary Controller

Abstract

In the process of long horizontal directional well drilling, the contact between drill string and borehole wall leads to serious dragging pressure. Therefore, a Drill String Rotary Controller(DSC) for directional well is proposed, and the function test and performance test of DSC are completed through experimental platform. According to working characteristics of DSC, a coupled drill string dynamic model for directional well drilling is established. The coupling dynamic characteristics of different drill pipe sections and different modules in the axial and torsional directions are studied. The results show that in the process of directional drilling, the axial velocity of the bottom hole module is low. Under the action of formation reaction force, the drilling volume of the drill bit decreases, but it still keeps in contact with the rock. At this time, the drill string system is in a normal drilling state. When drill string is stable, the angular velocity of different drill pipes, rotary table and collars are stable at 31.16 rad / s, and the angular velocity of DSC and BHA are stable at 43.19 rad/s. It indicates the DSC works well, the drill string is balanced in the torsional direction, and there is dynamic friction between the drill pipe and the drill string, which is conducive to lower the drill string. Through theoretical and experimental research, the tool effectively solves the problem of serious drag pressure in directional drilling process, and provides a theoretical basis for directional well drilling speed increase.