层状各向异性介质中任意取向电偶源的海洋电磁响应

从麦克斯韦方程组出发,利用双重傅里叶变换和矢量势函数,详细推导出了层状各向异性介质中任意取向电偶源的电磁场计算公式,利用汉克尔数值滤波方法计算得到电磁场,并验证了算法的正确性和精度.有限长电偶源不能作为电偶极子源计算其电磁场响应,尤其是在收发距较小的情况下,可以采用积分法或者将有限长电偶源剖分成足够多的电偶极子源计算其电磁响应后累加得到有限长电偶源的电磁响应.针对海底油气模型,分析了覆盖层和油气层的垂向电阻率在不同姿态发射源下电磁场的变化情况,发现覆盖层和油气层的垂向电阻率对水平电场有很大影响,且轴向装置要比赤道装置受覆盖层和油气层垂向电阻率的影响大.

Marine controlled-source electromagnetic fields of an arbitrary electric dipole over a layered anisotropic medium

A new algorithm for marine controlled-source electromagnetic (CSEM) fields of an arbitrary electric dipole over a layered anisotropic medium is presented in this paper. The algorithm is correct and accuracy based on the Maxwell equations, which is implemented by Hankel transform and double Fourier transform combined with vector potential. The fields of finite length wire source cannot be approximated as fields of a point dipole source, especially for the small source-receiver distance; but it can be synthesized by superposing point dipole fields and numerical integral method. We simulate the marine CSEM responses of canonical oil model over a layered anisotropic medium and analyze effects of anisotropy in over-burden layers and reservoir targets with different electric dipole sources. The results show that vertical anisotropy in both the reservoir target and the over-burden sediment affects considerably the marine CSEM fields, and contributes more to inline geometry electric field than to broadside geometry.