煤层气连通井导向钻井钻头定位方法

基于低频交变磁场的特性，构建了近钻头磁源的低频交变磁场数学模型。根据随钻测量仪器（MWD）的测量原理， 建立测量坐标系，并推导出磁源坐标系向测量坐标系转换的解算方法，从而形成了测量坐标系下的钻头定位方法。在此基础上设计并制作了精确连通导向仪器和工具，配套了磁导向连通井的钻井工艺，并进行了现场应用，结果表明:在常规导向钻具组合基础上增加近钻头磁短节形成磁导向钻具组合，利用参数优化和轨迹实时测量和轨迹姿态控制，在730 m 水平段实现了连接误差小于1 m，使水平井和直井精确连通，为煤层气的开发提供了技术支撑。

Drill bit positioning method based on connected well guidance for coalbed methane

On the basis of the features of low-frequency alternating magnetic field, the mathematical model of low-frequency alternating magnetic field near the magnetic source in drill bit has been set up. According to the measurement principle of measurement-while-drilling (MWD) tool, the measurement coordinate system has been set up, and the method for conversion from magnetic source coordinate system to measurement coordinate system has been derived, so as to form the drill bit positioning method under measurement coordinate system. On this basis, the accurate connection guiding instruments and tools have been designed and made, the drilling process for magnetic guiding connected well has been developed, and the field application has been carried out. The results indicate that: by adding the near-drill-bit magnetic tool to conventional combination of drilling tools, optimizing the parameters, carrying out real-time measurement of trajectory and controlling the trajectory posture, the connection error less than 1m has been achieved in the 730m horizontal section, so that the horizontal well and vertical well can be connected accurately, and the technical support has been provided for the development of coalbed methane.