井周界面电磁散射探测数值模拟

依据电磁散射理论，模拟电磁散射对地层界面响应，探讨电磁波测井"向前看"能力。根据电磁场分布特征，将接收天线对称分布在发射天线两侧，对比接收天线信号差异，获取井旁界面电磁散射信号；在不同供电频率、天线源距、电阻率对比度条件下，模拟天线分量信号的响应特征，分析其与地层界面关系及敏感性。结果表明：与现有测量方法相比，在更小的源距条件下，该方法利用电磁散射信号探测井旁界面，达到了更优的探测效果；仪器信号强度和探测范围受界面两侧电阻率及其差异的影响，并随着电阻率差异的增大而增大；将同轴和倾斜天线幅度差信号交会，根据交会数据落点位置，确定界面位置简单有效。
The response to the interface is numerically simulated based on the electromagnetic scattering theory. Putting symmetrically the receiving antenna on two sides of the transmitting antenna, the scattered signal off the interface can be reflected by the difference of receiving signals. The electromagnetic responses to the bed boundary were analyzed at different frequencies, distances of antenna and resistivity contrast ratios of two sides' formations. The results show that electromagnetic scattering measurements can reach deeper sensitivity than most current tools. The contrast ratio of the formation resistivity determines the signal strength. The sensitivity depth becomes larger with increasing resistivity contrasts. A cross plot can be drawn to show the signal magnitude difference between the coaxial and tilt antenna, which can be easily used to determine the position of formation interfaces