可控源海洋电磁测量深层弱信号增强与地层电导率分布反演方法研究

The project mainly focuses on the subject of "Study on methods of enhancement of weak electromagnetic signals from deep buried target and inversion of formation conductivity distribution under the sea floor by using Controlled Source Marine EM Measurements". The research topics include three aspects of technique of synthetic aperture source of the MCSEM data and the enhancement method of the weak electromagnetic signals of the deep buried target, the EM field decomposition and interferometry deconvolution methods and the multiplicative regularization inversion method. The first item of investigation is reconstruction method of optimal synthetic aperture source from the MCSEM data and the enhancement technique of the weak electromagnetic signals of the deep buried target covers analysis of the characteristics of the EM responses of the synthetic aperture sources of the MCSEM data, investigation of the compensation for effects of EM diffusion on the field amplitude and phase of a single source, and the determination of the weights that construct the optimal synthetic aperture source from several single sources. The second item of study on the EM fields decomposition and interferometry deconvolution methods include the effective decomposition method of original EM field into upgoing and downgoing EM field components, and the interferometry deconvolution method of the EM data acquired from seal floor receivers, and suppress both of direct wave and airwave and other noises to improve the signal to noise ratio of the MCSEM measurements. The third aspect of research on the multiplicative regularization inversion method covers the acceleration procedures of the convergence rate of the multiplicative regularization function, the effective calculation of the EM response sensitivity to the formation conductivity and the quality Gauss-Newton iterative inversion technique, in order to derive an adequate reconstruction of the under sea floor formation conductivity. The project will start with the analysis of the characteristics of the electromagnetic responses of the synthetic aperture source. and adopt methods of the field decomposition and interferometry deconvolution of the EM response to enhance the weak EM signal resulted from the deep buried target, furthermore, through the implementation of the Gauss-Newton iterative inversion technique with multiplicative regularization function to fulfill the aim of obtaining correct distribution of the under sea floor formation conductivity

研究可控源海洋电磁(MCSEM)测量深层弱信号增强与地层电导率分布反演方法。研究内容有MCSEM响应合成孔径源及深层弱电磁信号增强方法、电磁波场分离与干涉反褶积方法和乘积型正则化反演方法三个方面。MCSEM响应合成孔径源及深层弱电磁信号增强研究包括：合成孔径源电磁响应特征分析,单个电磁源响应的幅度和相位移校正方法,优化合成孔径源权系数计算；电磁响应的波场分离与干涉反褶积方法研究包括：合成孔径源电磁响应的上行和下行波场分离方法，海底地层电磁响应的干涉反褶积方法，用于空气波等干扰信号的压制和信噪比提高；乘积型正则化反演成像方法的研究包括：乘积型正则化因子加速收敛方法,电磁响应灵敏度有效计算方法和高斯-牛顿迭代反演方法,以得到海底地层电性异常体的正确重构。本项目从电磁响应合成孔径源信号特征分析入手，用电磁响应的干涉反褶积实现深层弱信号增强，进而基于高斯-牛顿迭代反演方法获取准确的电导率分布。

研究了可控源海洋电磁(MCSEM)测量深层弱信号增强与地层电导率分布反演方法。在可控源海洋电磁(MCSEM)响应合成孔径源及深层弱电磁信号增强方面，研究了合成孔径源电磁响应特征，单个电磁源响应的幅度和相位移校正方法，优化合成孔径源权系数计算。在MCSEM响应的波场分离与干涉反褶积方法，研究了合成孔径源电磁响应的上行和下行波场分离方法，海底地层电磁响应的干涉反褶积方法，并用于空气波等干扰信号的压制和信噪比提高。在乘积型正则化反演成像方法研究方面，推导并实现了乘积型正则化因子加速收敛方法，建立并测试了电磁响应灵敏度有效计算方法和高斯-牛顿迭代反演方法，应用所研究的方法得到了正确的海底地层电性异常体的重构像。通过MCSEM响应合成孔径源及深层弱电磁信号增强方法、电磁波场分离与干涉反褶积方法和乘积型正则化反演方法三方面内容的研究，较好地实现了可控源海洋电磁深层弱信号的增强和海底地层电导率分布的正确成像，对于海洋资源与能源的勘探开发具有重要的意义。