旋转磁导向系统井下磁源优化设计

为了提高随钻探测过程中永磁体磁源的磁性能，增大磁源信号的使用范围，对旋转磁导向系统井下磁源进行了优化设计研究。根据电磁场理论及所用磁源的特点，建立了圆柱形永磁体电流模型；利用矢量磁位方程推导出圆柱形永磁体截面直径和长度与其空间磁场强度的关系，圆柱形永磁体的截面直径和长度决定了其空间磁场强度；并对不同几何参数的圆柱形永磁体和其所在磁短节的空间磁场强度进行了测量和分析。永磁体长度一定时，直径从10 mm增大到20 mm，其空间磁感应强度增加了近80%；长度从50 mm增大到100 mm，其空间磁感应强度增大了近200%。试验表明，内部并排平行放置永磁体的磁短节空间磁场强度与圆柱形永磁体的直径和长度均呈单调递增关系。等体积永磁体的空间磁场测量结果表明，长度与直径之比越大，永磁体空间磁场越强。因此，合理设计永磁体的几何参数，可以增强磁短节的空间磁感应强度，提高测量的准确性。 

Design Optimization of Downhole Magnetic Source for Rotary Magnetic Ranging System

In order to improve the magnetic field intensity and extend the range of magnetic field of magnetic source used in RMRS(rotating magnet ranging system),magnetic source optimization design was conducted.Based on static magnetic field theory and the feature of magnetic source,the electric current model of cylindrical permanent magnet used in the magnetic source was established.The relationship among the magnetic intensity and the diameter as well as length of the cylindrical permanent magnet was derived based on magnetic vector potential equation.Spatial magnetic intensity is dependent on diameter and length of the cylindrical permanent magnet.According to the experiments on the different cylindrical permanent magnets,the spatial magnetic intensity of the magnet sub was measured and analyzed.The results show that the spatial magnetic induction density was increased 80% when the diameters of the magnets increase from 10 mm to 20 mm with the same length.Given the same magnet diameter,the spatial magnetic induction density increases 200% when the magnet length increased from 50 mm to 100 mm.For the magnet sub whose permanent magnets are arranged side by side,its spatial magnetic intensity will increase with the increase of diameter and length of cylindrical permanent magnets.Given the same volume,the magnet will have a stronger magnetic intensity with a greater length-to-diameter ratio.The magnet with a length-to-diameter ratio of 8.33 has the twice magnetic intensity as the magnet with a length-to-diameter ratio of 0.53.Consequently,the design optimization of the magnet’s geometrical parameter can effectively improve the performance of the magnetic source.