Study On One-dimensional Lateral Constrained Regularization Inversion Method For Airborne Transient Electromagnetic Data

Relying on the research content of the research project "Comprehensive Aeronautical Geophysical Data Processing Methods and Software Development"(No.2017YFC0602202)of the National Key R&D Program Project "Development of Aerospace Geophysical Technology Demonstration and Processing Interpretation Software Platform in Typical Coverage Areas",This paper mainly discusses how to ensure the lateral continuity of the inversion profile in the 1D inversion of ATEM,and how to add a priori information such as logging data in the 1D inversion.In order to solve the problem of lateral continuity inversion,this paper discusses the method of 1D inversion with lateral constraints on ATEM data using the idea of regularization.The method is to add the lateral constraints regularization term on the basis of the Occam's inversion of the original vertical model smooth regularization.This method makes the model inversion,while maintaining the smoothest longitudinal model,the smallest difference from the previous inversion results.So as to achieve the purpose of lateral restraint.And considering that when there is a vertical model smooth regularization term,the model has more layers and a smaller layer thickness during inversion.Therefore,the lateral continuity of the profile can be achieved only by considering the lateral continuity of resistivity in the lateral constraint.Then,in order to effectively use a priori information,this paper proposes a segmented inversion strategy for transient electromagnetic profiles,which means that points with well logging data on the profile or points with better measured data can be used as the split point,and then invert from the split point to the two ends,and In the vicinity of the measuring point of priori information such as log data,the real logging model can be used as a reference model for lateral constraints,thereby reducing the accumulation of inversion errors due to lateral constraints.In addition,the efficiency and accuracy of calculating the ATEM response of the central loop device using the sine transform and G-S transform are discussed.And it discusses the problem of too many lookup tables and long time-consuming in areas where the terrain height changes greatly and the flying height fluctuates,and a method for calculating apparent resistivity using Newton iteration method instead of table lookup method is proposed.The results of theoretical model test and measured data processing show that: 1.Regularized lateral constrained inversion can effectively apply prior information such as logging to make the inversion results closer to the real results,and also make the inversion profile continuity better.2.The inversion results of the measured data show that the continuity of the profile is good,which is consistent with the actual geological conditions and the results of the surface electrical method.This shows that the method applied in this paper has certain effectiveness and practicability.3.The number of iterations using the Newton iteration method is within the acceptable range,which can avoid the establishment of complex query forms.