Improved adaptive thin-layer inversion for semi-airborne transient electromagnetic method

Abstract

ABSTRACT To improve the resolution of electromagnetic inversion for thin layers, electromagnetic one-dimensional inversion was studied. The smooth conductivity model produced by Occam's inversion cannot accurately represent the information of the subterranean thin resistive layers, leading to erroneous inversion findings. The existing thin resistive layers’ inversion method sets the model constraint term at the thin resistive layers to 0, resulting in abrupt changes in resistivity values. Given these problems, we proposed an adaptive roughness matrix calculation method to improve the thin, low-resistive-layer resolution. The resistivity difference between neighboring layers of the updated inversion model determines the roughness matrix, allowing for the realization of adaptive inversion of the thin layer. It achieves semi-airborne transient electromagnetic enhanced adaptive thin-layer inversion and automatically manages the model constraint term. The calculation of the synthetic model demonstrates that the improved adaptive thin-layer inversion method does not need to know the thin, low-resistive layers information in advance. The model can produce appropriate inversion results regardless of the presence of thin, low-resistive layers. Finally, the drilling results are consistent with the inversed appearance of the semi-airborne transient electromagnetic field data. Other geophysical adaptive thin resistive layers inversion can also benefit from this paper's findings.