1D OCCAM inversion of SOTEM data and its application to 3D models

We propose an OCCAM scheme for inversion of SOTEM data based on the vertical magnetic field component, and applied it to synthetic 3D data and field measured data. This inversion scheme works well for the most 1D models and the inversion results are independent of offsets. The noise has a great influence on the OCCAM inversion, but the results still have good accuracy as long as the noise level is less than 5%. However, if there is a thick conductive layer in the shallow subsurface, the resolution of the OOCAM inversion will be reduced and only the average resistivity of lower strata can be obtained. The 1D inversion scheme applied to 3D data will produce a large error, especially in the edges of the abnormal bodies. The degree of such influence is related to the resistivity contrast between the anomaly bodies and the background. But for the most real earth models whose resistivity approximately changes continuously, the 1D OCCAM inversion still works well. At last, a case study in Shaanxi province is presented to verify the research results of this work.