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近年来,随着三维深部地质调查和非常规能源勘探项目的展开,大地电磁这种非震地球物理方法的重要性越来越突显.尽管大地电磁三维反演方法在近十年得到蓬勃的发展,但是还处在试验阶段,没有得到普遍应用.因此生产实践中普遍使用二维反演方法.大地电磁反演方法主要有非线性共轭梯度法,奥卡姆法和数据子空间法.由于占用内存少、速度快,非线性共轭梯度法得到更广泛应用.该方法在理论上介绍比较多,但在实践中如何应用的介绍却非常少.本文利用内蒙古扎鲁特盆地采集的一条大地电磁剖面数据,选择不同电阻率的初始模型,正则化参数,底板误差做一系列共轭梯度反演方法试验.试验结果表明:在通常取值范围内,一般参数对反演结果影响不大,但是在个别参数数值,反演结果有一定差别.本文还使用TM模式,TE模式,TM+TE模式做共轭梯度反演试验.试验结果表明不同模式反演结果差别较大.TM+TE模式反演电阻率模型综合TM和TE单独反演特征,更好地反映地质结构.然而反演结果应该参考视电阻率和阻抗相位的曲线图、拟断面图做综合分析.这样做能减少对地质的错误解释.本文试验结果对大地电磁实践者具有一定参考意义.
In recent years, with the development of 3D deep geological survey and unconventional energy exploration projects, the importance of the non-seismic geophysical methods such as MT has become more and more prominent.Although the 3D EMT method has been booming in recent ten years , But it is still in the experimental stage and has not been widely used, so two-dimensional inversion method is widely used in production practice.The methods of the geomagnetic inversion mainly include the nonlinear conjugate gradient method, the Occam method and the data subspace method Occupying less memory, faster, and nonlinear conjugate gradient method is more widely used.This method is more introduction in theory, but the introduction of how to use in practice is very little.This paper makes use of a land collected in Zhalut Basin, Inner Mongolia Electromagnetic cross-section data, initial models with different resistivities, regularization parameters and backplane error were tested by a series of conjugate gradient inversion methods.The experimental results show that the general parameters have little effect on the inversion results in the range of normal values, However, there are some differences between the inversion results and the numerical values of individual parameters.This paper also uses the TM mode, the TE mode and the TM + TE mode to do the conjugate gradient inversion test.The experimental results show that The results of the same model inversion are quite different.TTM + TE model inversion resistivity model integrated TM and TE alone inversion characteristics to better reflect the geological structure.However, the inversion results should refer to the apparent resistivity and impedance phase curve, To do a comprehensive analysis of the quasi-section map.This can reduce the wrong interpretation of the geological.The results of this paper is of some reference to the earth electromagnetic practitioners.