Research On Measurement Method Of Dynamic Point-the-Bit Rotary Steerable Drilling Tool

Dynamic Point-the-Bit Rotary Steerable Drilling Tool(DPRSDT)is the most advanced steerable drilling tool at present,which has the advantages of small frictional resistance,fast drilling speed,good borehole quality,easy controlling,and strong displacement extension capability,can be more adaptable to harsh geological conditions and complex borehole structure.Its measurement accuracy directly affects the technical index and control performance of the steerable drilling tool,so the research is of great significance.Based on a self-developed prototype of the DPRSDT,the measurement method is studied.The accurate measurement for the speed to ground of stable platform and toolface angle is the focus of research.Firstly,the classification of rotary steerable drilling tools and the research status at home and abroad are summarized.The advantages and research significance of the DPRSDT are indicated.Secondly,on the basis of mastering the directional drilling parameters,the working principle and control scheme of the DPRSDT prototype are analyzed.The necessity and importance of the measurement method research are explained.Thirdly,the measurement goal of the DPRSDT is clarified.On the basis of being familiar with the structure of measurement system,through analyzing measurement characteristics of sensors and studying filtering theory,the signal processing method of rate gyroscope and the measurement scheme based on a complementary filter for the toolface angle are determined.Fourthly,the constant error of the rate gyroscope is eliminated by correcting the zero voltage.The static random error of the rate gyroscope is reduced by classical Kalman filter while the dynamic random error is reduced by state-augmented Kalman filter.The Allan variance is used as a criterion for evaluation.Through the above signal processing methods,the measurement accuracy of the rate gyroscope is effectively improved.Finally,on the basis of in-depth study of the complementary filtering algorithm,combined with the data of a simulation experiment for downhole working condition,a complementary filter is designed to achieve accurate measurement of the toolface angle.By studying the vibration criterion and the velocity criterion,an adaptive complementary filter is further designed and implemented,of which the parameters can be automatically adjusted according to the change of the DPRSDT motion state and downhole condition,so the practical drilling demand can be satisfied.Through the research of the measurement method of the DPRSDT,laying a foundation for the practical development of rotary steerable drilling tools.