The Concept of Multi-scale MT Interpretation Strategy and Its Application in Guizhou Province of China

Improving the resolution of the magnetotelluric (MT) method and reducing the non-uniqueness of MT inversion for abnormal bodies of different depth and different scale is a significant problem, and thus research on this issue is important. First, based on the classical optimal inversion theory of the MT method, we introduced the concept of multi-scale MT interpretation strategy (MSMIS). Then, typical geo-electric models were constructed, and numerical simulations were carried out; the results of these simulations illustrated the advantages of MSMIS, which can effectively identify not only the overall structural framework of deep bodies but also the spatial distribution characteristics of shallow local inhomogeneous abnormal bodies with small scale. Finally, by targeting the slurry leakage caused by underground karst in shale gas drilling, we used MSMIS to reprocess the existing audio magnetotelluric (AMT) data, which accurately identified the spatial location and distribution characteristics of the shallow underground karst and provided a reliable reference for the re-selection of the appropriate location of the borehole. Subsequent drilling data verified the correctness of MSMIS. The research results show that MSMIS can effectively improve the exploration effect of the MT method for deep and shallow anomalies, which effectively promotes and improves the practical application of the MT method.