Structural Design And Experimental Study Of Double-bit Self-balancing Drilling System

Nowadays,due to the over exploitation of resources in shallow layer,its reserves have been gradually exhausted.Therefore,in the future,the exploration of energy resource will gradually move to deeper strata.This also means that as the most direct means of resource exploration,drilling is also necessary to improve the drilling capacity for deeper strata.In traditional drilling method,the drill rig provides torque to the drill bit through the drill string,so excessive drilling depth means too long drill string length,and brings greater wear and risk of damage,which will finally improve the risk of downhole accidents.Therefore,the research group put forward the principle of selfbalancing drilling,that is,using the inner and outer double rotors of the motor to drive a pair of inner and outer double bits to drill at the same time.This new working mode can make the drilling tool form a closed-loop torque self balance state at the bottom of the hole.This working method can completely solve the loss and disturbance caused by the drill pipes' rotation in the hole,and fundamentally improve the comprehensive drilling efficiency.This paper makes an in-depth study on the self-correlation of the new drilling tool.The main research contents and conclusions are as follows:(1)The specific function analysis of self-balancing drilling system is carried out,including torque self-balance calculation of double bit,WOB regulation analysis of inner and outer bit,and torque regulation analysis of inner and outer bit.It is concluded that the reverse rotary rock breaking of double-bits can balance their reverse torque,and the upper drilling tool does not have to bear the torque from double bit.By adjusting the pressure,the inner and outer drill bits can rotate independently or simultaneously.(2)The sealing design of self-balancing drilling system in the mud environment is studied.According to the analysis of the existing conventional sealing methods and the sealing environment encountered by the self-balancing drilling system in the hole,combined with the design concept of self balanced self compensation,a set of sealing system suitable for the self-balancing drilling system is optimized,which can guarantee stable long-term running.The system is mainly composed of high pressure sealed oil cavity and combined dynamic and static seals.(3)This paper designs and optimizes the electric control system suitable for the self-balancing drilling system,selects the sensor system of data acquisition and analysis according to the various conditions required by the self-balancing drilling system,and further refines the relevant operation of the self-balancing drilling system from the aspects of the determination of the control logic relationship and the control program and execution.(4)Based on the analysis of material selection,processing process and assembly process,the processing,experiment and adjust of the functional prototype of the selfbalancing drilling system are completed,which ensures the performance of the functional prototype including reliability and stability.Through the function analysis,research of sealing method,electric control system's design and processing assembly process of self-balancing drilling system,this paper clarifies a series of drilling parameters of self-balancing drilling system,further improves the equipment reliability of self-balancing drilling system,and makes a good theoretical and equipment foundation for the further promotion and application of selfbalancing drilling system.