井下电磁源磁场在铁磁环境下的衰变机理研究

Study on the Magnetic Field Decay Mechanism of Downhole Electromagnetic Source in the Ferromagnetic Environment

为了分析在电磁导向钻进过程中井下电磁源所受到的铁磁干扰因素,对电磁源磁场在铁磁套管影响下的衰变原因进行针对性研究。利用镜像电流分析法在恒定磁场边界条件下对于不同磁导率介质交界面上的磁场矢量的变化规律进行了分析,得出在井下套管的铁磁环境下其磁感应强度的衰变规律。利用软件分析了套管对电磁场的阻碍作用,并通过试验进行验证。研究结果表明:电磁源在铁磁环境下的衰变主要是由于在井下铁磁物质磁导率与周围其他介质磁导率存在的差异而导致的。

In order to find out the reason of the electromagnetic field decay during the electromagnetic guidance drilling,the ferromagnetic interference of the casing in the downhole should be analyzed.By using the mirror-current method the magnetic induction changes on the interface between the two mediums can be calculated.The results show that the deterioration law of magnetic induction parameters mainly associates with the magnetic conductivity.The casing ferromagnetic blockade effect is simulated and tested.The research findings show that the different the magnetic induction of the different mediums is the key reason of the electromagnetic field decay in the ferromagnetic environment.