Research On A New Control Mechanism For Mechanical Vertical Drilling Tools

The environment of oil and gas exploration and development is becoming more and more complex,which puts forward stricter requirements for drilling technology.Under the economic environment of low oil price,how to reduce the cost of oil and gas exploitation is a problem that the drilling industry must face.The mechanical vertical drilling technology relies on the power of the eccentric weight as the rectification power,and only rely on the deflection control of the eccentric weight under the action of gravity to continuously rectify the deflection.It has the advantages of low cost,simple equipment,good reliability,and can work in high temperature environment,which can be widely used in the field of vertical drilling.The mechanical automatic vertical drilling tool is becoming the best choice to reduce cost and increase efficiency.In this paper,a new control mechanism,nozzle hydraulic balance turbine disc valve control mechanism(NTD control mechanism for short),is proposed for mechanical vertical drilling tools.It is important to study and optimize the performance of the mechanism for improving the level of mechanical vertical drilling technology.This paper first introduces the technical principle of CFD numerical simulation,then designs the main components of NTD mechanism,and finally uses CFD method to simulate NTD mechanism to explore its performance.The starting performance of NTD mechanism is directly related to the stress of turbine.The change of turbine blade angle,fluid velocity,nozzle diameter and nozzle position are the main factors affecting the performance of hydraulic turbine.With the increase of blade angle,turbine torque increases first and then decreases.With the increase of fluid velocity,nozzle diameter and nozzle position,turbine torque increases continuously.The shape of the nozzle will affect the characteristics of the jet,the contraction nozzle can provide better power,but it will intensify the erosion of the turbine.The nozzle will move under the drive of the bias system,and the turbine willdrive the disc valve to follow the nozzle's movement under the action of the nozzle jet,which is called the following property of NTD mechanism.Following property is the most important characteristic of mechanism.When the nozzle stops moving,the turbine continues to rotate left and right,but eventually stabilizes.The farther the nozzle deviates from the equilibrium position,the longer the stabilization time is.Under the influence of friction,the stop time of turbine is less than that of non friction condition,and the stay position will deviate from the equilibrium position by a certain angle,which is the limit of position control accuracy of NTD mechanism.This limit is related to the construction of the symmetrical position of the hydraulic balance turbine.NTD control mechanism realizes the "soft" connection between the weight platform and the upper disc valve,which can reduce the friction resistance between the upper disc valve and the lower disc valve and the impact of bottom drilling vibration on the weight platform.This mechanism can effectively improve the control accuracy of drilling tools,and is of great significance to improve the technical level of vertical drilling tools in China.