Review on airborne electromagnetic inverse theory and applications

Abstract

Airborne electromagnetic (AEM) data processing and inversion has progressed from the early conductivity-depth imaging, to 1D inversion for a layered earth model, and most recently to 2D/3D inversions. The new processes have used methods for searching for solutions, applying constraints, and focusing images, such as Occam's, laterally constrained, and holistic inversions. For airborne data imaging and 1D inversion, some algorithms are fast, whereas others have control over data misfit and the vertical or lateral smoothness. Beyond 1D algorithms, 2D/3D inversions are based on currently used methods such as isolated conductor models (which are good for highly conductive orebodies in resistive background) and techniques that discretized regions that are used for more complex structures and backgrounds. In the latter case, the computations are slow, so research is focusing on time-efficient computer algorithms for solving the equations such as Gauss-Newton, quasi-Newton, and nonlinear conjugate gradient algorithms. For the electromagnetic (EM) problem, the solution can be obtained in a more practical time frame if material that has minimal impact is ignored. Two approaches can be used to speedup the EM inversion process -the moving footprint and direct solver methods. We hope our work will to some extent help stimulate and focus the research in AEM inversion.

AEM in Norway: A Review of the Coverage, Applications and the State of Technology

“…Processed time-domain or frequency-domain AEM data is inverted with the help of 1D, 2D and 3D inversion routines and to calculate the true resistivity or conductivity of the ground [20][21][22].…”

Bayesian Inversion of Frequency-Domain Airborne EM Data With Spatial Correlation Prior Information

“…AEM data interpretation mainly relies on inversion. For a review of various inversion methods for AEM data, refer to Yin et al [5]. AEM inversion methods are mainly divided into deterministic inversion methods based on regularization theory and Bayesian inversion methods based on random sampling [5].…”

“…For a review of various inversion methods for AEM data, refer to Yin et al [5]. AEM inversion methods are mainly divided into deterministic inversion methods based on regularization theory and Bayesian inversion methods based on random sampling [5]. Deterministic inversion methods are based on various optimization methods to obtain a single inversion result [6][7], and has been developed to the inversion of 3D model [8][9][10].…”

libEMM: A fictious wave domain 3D CSEM modelling library bridging sequential and parallel GPU implementation

“…Controlled-source electromagnetics (CSEM) has been a well established technology in detecting hydrocarbon bearing formations to do geophysical explorations (Chave and Cox, 1982;Constable et al, 1986). CSEM has been applied to air-bone (Chang-Chun et al, 2015) and cross-well (Alumbaugh and Newman, 1997) geometries, in land (Grayver et al, 2014;Ward and Hohmann, 1988;Zhdanov and Keller, 1994) and/or marine environment (Constable, 2010;Eidesmo et al, 2002;Ellingsrud et al, 2002;MacGregor and Tomlinson, 2014). These applications are based on the high sensitivity of the low-frequency electromagnetic signals to detect high resistivity contrast in the subsurface.…”