| Relying on the research content of "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" as well as "intelligent identification and engineering demonstration of multi-method integrated detection of hidden disaster causing body" sub project "ground multi-dimensional and multi-component exploration technology and equipment engineering demonstration",this paper proposes a wide field apparent resistivity method based on translation algorithm;at the same time,discusses how to add logging data in 1D inversion of WFEM,and how to improve the lateral continuity of profile.Firstly,this article systematically discusses the 1D forward modeling theory of WFEM,and by analyzing the spatial distribution law of each component of the bipolar source electromagnetic field with different frequencies in a uniform half space,then gives the measurement range of each component.In addition,the iteration algorithm or inverse interpolation algorithm is often used to calculation the apparent resistivity in the WFEM,and speed is relatively slow.In this paper,by analysing the analytical expressions of the electromagnetic field components of bipolar source in uniform half space,we found a translation characteristic between frequency and resistivity if other conditions unchanged.According to this characteristic,a high precision solution of apparent resistivity without iteration is proposed.Compared with the traditional method,this method also takes into account the influence of the relative position of the transmitter and receiver,and the calculation speed is higher.In order to verify the correctness of the translation algorithm,we design the uniform half space model and the H-type model,then compare and analyze the results of the translation algorithm with the iterative algorithm and the inverse interpolation algorithm.The results show that the three are in good agreement,which proves the feasibility of the translation algorithm.In order to further verify the effectiveness of the translation algorithm,we calculate the apparent resistivity of each component of the uniform half space,two-layer and three-layer model in turn.The results show that each component can correctly reflect the parameters of the geoelectric model,but the ability to identify the bottom layer is different.Finally,we analyse the influence of the receiving and transmitting distance on the apparent resistivity curve.It can be seen that when the receiving and transmitting distance is large,the apparent resistivity curve in the low frequency band is closer to the real resistivity of the bottom layer,while the difference in the middle and high frequency band is smaller.In order to improve the lateral continuity of 1D inversion profile,we add a priori condition to the Occam's inversion objective function,so that not only the longitudinal smoothness of the inversion model is considered in the inversion process.When there is logging data,this condition can realize the longitudinal constraint which in the vicinity of the measuring point of the well,and the least difference between the inversion results of the other measuring points and the previous measuring point.To effectively use a priori data and reduce the accumulation of inversion errors due to lateral constraints,this paper adopts the method of dividing the whole profile by taking the measuring points adjacent to the well logging or the measuring points with stable electric(magnetic)field value and wide field apparent resistivity as the section dividing points.Finally,the measured data of WFEM are processed.The results show that 1D lateral constrained inversion can improve the lateral continuity of the profile,and it is consistent with the actual geological conditions,which shows that the research has certain practical application value. |
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