Qualitative analysis of MTEM response using instantaneous attributes

• Published in: Journal of applied geophysics 2017-11, Vol.146, p.37-45
• Main Authors: Fayemi, Olalekan, Di, Qingyun
• Format: Article
• Language: English
• Subjects: Center finite difference; FDTD; Instantaneous attributes; MTEM; Polynomial phase difference
• ISSN: 0926-9851; 1879-1859
• DOI: 10.1016/j.jappgeo.2017.07.014

This paper introduces new technique for qualitative analysis of multi-transient electromagnetic (MTEM) earth impulse response over complex geological structures. Instantaneous phase and frequency attributes were used in place of the conventional common offset section for improved qualitative interpretation of MTEM data by obtaining more detailed information from the earth impulse response. The instantaneous attributes were used to describe the lateral variation in subsurface resistivity and the visible geological structure with respect to given offsets. Instantaneous phase attribute was obtained by converting the impulse response into a complex form using the Hilbert transform. Conversely, the polynomial phase difference (PPD) estimator was favored over the center finite difference (CFD) approximation method in calculating the instantaneous frequency attribute because it is computationally efficient and has the ability to give a smooth variation of the instantaneous frequency over a common offset section. The observed results from the instantaneous attributes were in good agreement with both the subsurface model used and the apparent resistivity section obtained from the MTEM earth impulse response. Hence, this study confirms the capability of both instantaneous phase and frequency attributes as highly effective tools for MTEM qualitative analysis. •MTEM earth response contains information about the cumulative subsurface resistivity.•A more efficient qualitative analysis technique for MTEM method is proposed.•The technique relies on changes in frequency and phase; independent on amplitude.•Polynomial phase difference estimator generated smoothly varying IF section.•Instantaneous attributes gave a better representation of subsurface geology.