Research On Work Characteristics Of The Eccentric Stable Platform In Mechanical Automatic Vertical Drilling Tool

As a kind of active deviation correction technology,automatic vertical drilling technology is one of the most important key technologies in drilling engineering.The mechanical automatic vertical drilling tool relies on the mechanical stability platform to control the well inclination.It is simple in structure,low in cost,and can withstand temperature up to 300℃.It is suitable for deep wells,ultra-deep wells and other hightemperature and high-pressure operating environments,and it is the only way to actively prevent the inclination under high temperature conditions in extra-deep scientific drilling.As a key component of mechanical automatic vertical drilling tool deviation measurement and control,the response sensitivity and stability of the stable platform directly affect the tool deviation correction performance.It is meaningful to study the dynamic characteristics of automatic vertical drilling tools to improve the accuracy of automatic vertical drilling tools deviation correction.Based on the force analysis of the mechanical automatic vertical drilling tool’s eccentric stable platform,the initial design of the eccentric stable platform is completed,and the effect of the friction coefficient between disc valves,thrust bearing friction coefficient,axial bearing friction coefficient and the force between the upper and lower disc valves on the response accuracy and stability of the eccentric stable platform,thus clarifying that the friction coefficient and the interaction force between the upper disc valve and the lower disc valve which are important parameters for forming the friction resistance between the disc valves also are key factor for stable platform performance.To decrease the interaction force between the upper plate and the lower plate of the valve,an incomplete contact structure was used between the upper plate and the lower plate.Combining the theory of gap flow and numerical simulation methods,it can be found that the introduction of highly appropriate gap flow not only can effectively reduce the contact area between the valve and equivalent friction radius,it also can reduce small valve and fluid pressure difference between the different contact surface at the same time,thereby reducing friction resistance between disc valve and improving controlling precision of the stabilized platform.The upper and lower disc valves are required to bear the effect of the fluid pressure difference in the tool flow channel during the operation.Through the introduction of computational fluid dynamics analysis method,the internal pressure distribution of the mechanical vertical drilling tool system is analyzed.On the basis of guaranteeing the effective force at the pushing actuator,the pressure difference acting between the upper and lower disc valves is obtained.On the basis of fluid dynamics simulation,the design of the indoor experiment was completed,and the fluid environment of the stable platform at the disc valve of the stable platform under different boundary conditions was analyzed and verified by combining with the thrust force,which has positive significance for the dynamic analysis and optimization design of the stable platform.Based on Coulomb’s law,the principle of friction coefficient measurement is clarified,and the laboratory test bench for friction coefficient is developed.The friction coefficient of disc valve and thrust bearing in dry,water-lubricated and drilling fluid with 4% bentonite is tested,and the friction coefficient of bearing and disc valve under different working conditions is obtained.After analyzing the force of the stable platform and completing the research and testing of the key factors affecting the performance of the stable platform,this paper refers to the single pendulum dynamic model to complete the construction of the dynamic model of the stable platform,and introduces the method of numerical analysis.Based on the dynamic characteristics of the stabilized platform,the analysis shows that the stabilized platform exhibits a simple pendulum-like characteristic during the action,and its swing frequency increases with the increase of the inclination angle;at the same time,during the swing of the stabilized platform,the stable time and stable position of the heavy-weight stable platform are affected by the relationship between the frictional resistance and the eccentric torque.Since the stable platform is in the working process,especially the dynamic push-on mechanical automatic vertical drilling tool,the stable platform is affected by the rotation speed of the body during the working process.This paper analyzes the influence of the rotation speed on the performance of the stable platform and finds that when the rotation speed of the tool is the same as the initial movement direction of the stable platform,the response accuracy will be improved.At the same time,the platform will shift to the zero point of potential energy(the position of the low side of the well deviation)when the speed is reasonable,but when the speed increases,it will accelerate the deviation of the stable position.When the turning direction of the tool is opposite to the initial movement trend direction of the stable platform,the response accuracy will be reduced.The dynamic model of the stabilized platform of the mechanical vertical drilling tool and indoor test model built to test the key parameters of mechanical vertical drilling tool are benefit to improve control precision,thus laid a foundation for the structure optimization design,and the accumulated experimental data,the industrialization application of mechanical automatic vertical drilling tool is of great significance.