Downhole Propulsion/Steering Mechanism for Wellbore Trajectory Control in Directional Drilling

Abstract

Advanced directional drilling, especially rotary steerable systems, provides directional control of wellbore while continuously rotating the drill bit. Downhole propulsion/steering mechanism is one of the key components in rotary closed-loop drilling system. Downhole steering/propulsion mechanisms currently used for directional control include adjustable stabilizer, steerable downhole motor and steering actuators used in state-of-the-art rotary steerable systems. The novel electro-mechanical propulsion and steering mechanisms are introduced, in order to produce downhole weight on bit (WOB) and directional control of the drill bit while rotating it as well. The mechanisms are based on high-reduction ratio planetary gear system and DC motor. This propulsion/steering mechanism introduces a unique rotary steering method with a manner of turning screw inside borehole. As a downhole propulsion/steering mechanism, it can be integrated with an existing MWD system to provide directional control and downhole propulsion force on drill bit.

Development of Mathematical Model for Controlling Drilling Parameters with Screw Downhole Motor

“…To ensure required load on the bit a combined drilling method is used in production process. Distinctive feature of this method is in the joint operation of drilling string (DS) and screw down-hole motor (SDM) [4]. In the process of their joint work, torsional, lateral and axial oscillations can occur depending on type of SDM, its energy characteristics and DS, which acts as an elastic unbalanced rod [5].…”