Steering Control Research On A New Steering Mechanism For Static Point-the-bit Rotary Steerable System

Rotary steerable technology is a new drilling technology of mechanical,electrical and hydraulic integration. The obvious advantages of rotary steerabletechnology include low drilling resistance, high drilling efficiency, flexible drillingdirection adjustment, high drilling speed and long service time. The rotary steerabletechnology is widely used in the horizontal wells, extended reach wells and3Dmultiple targets wells. It represents the highest level technology in the oil exploitationequipments. Due to the technological monopoly of the foreign oil companies and theurge drilling needs of the domestic oil industry, to research the rotary steerabletechnology thoroughly is very significant. The achievement of rotary steerable drillingfor rotary steerable technology is based on the offset effect of steering mechanism.And then, the research of steering mechanism is the key point of the research of rotarysteerable technology. This thesis aims at a new steering mechanism for staticpoint-the-bit rotary steerable system, and some key technologies focus on the steeringcontrol principle, steering motion control, oil trajectory control, combined motionsimulation and control system analysis. The main achievements are as follows:(1) Steering principle analysis. The structural components of the new steeringmechanism are described. The steering principle based on a set of2DOFspecially designed planetary drive with small teeth number difference and auniversal joint is analyzed. And then, the mathematic model between the inputand the output of the new steering mechanism is established.(2) Well trajectory control analysis. The mathematic model of the eccentricdisplacement vector of the offset point on the drilling mandrel is established. Therelationship between the amplitude of the eccentric displacement vector and theinclination angle of2D well trajectory is established based on the ‘Three PointGeometry Method’ principle. And then, the relationship between the eccentricdisplacement vector of the offset point on the drilling mandrel and the inclinationangle, azimuth angle of3D well trajectory is then established based on the‘Limiting Curvature Method’principle.(3) Steering motion control simulation. The combined motion simulation isperformed by combining SolidWorks and LabVIEW. The design proposal, control principle and well trajectory control analysis of the new steering mechanism areverified by the simulation, which will lay theory foundation for the furtherexperiment design of the steering mechanism.(4) Control system research. The control system model based on3-closed loop PID isestablished. The performance of each single input control system is analyzed andthe correction of the control system is performed to satisfy the speed abilityrequirement of the new steering mechanism, which will provide theoreticalguidance for the future prototype experiment.