Unambiguous apparent conductivity for fixed-loop transient electromagnetic data

2006 ◽  
Vol 37 (4) ◽  
pp. 348-354 ◽  
Author(s):  
R. Schaa ◽  
J.E. Reid ◽  
P.K. Fullagar
Keyword(s):  
Electromagnetic Data ◽  
Apparent Conductivity ◽  
Transient Electromagnetic

Imaging quasi‐layered conductive structures by simple processing of transient electromagnetic data

Geophysics ◽  
1987 ◽  
Vol 52 (4) ◽  
pp. 545-554 ◽  
Author(s):  
James Macnae ◽  
Yves Lamontagne
Keyword(s):  
Delay Time ◽  
A Priori ◽  
Step Response ◽  
Layered Earth ◽  
Electromagnetic Data ◽  
Apparent Conductivity ◽  
Data Inversion ◽  
Transient Electromagnetic ◽  
Static Zone ◽  
The Cost

An “imaged” conductivity section of a layered earth can be obtained by simple transformation of step‐response electromagnetic data measured in the quasi‐static zone. This method of data transformation is presented as an alternative to conventional apparent conductivity transformations. At each delay time, the variation of the step response as a function of geometry (transmitter and receiver location) is transformed to an equivalent reference depth h, which can be related to the depth of electromagnetic field diffusion. The behavior of h as a function of delay time is nearly independent of the source‐receiver geometry. The slowness dt/dh divided by the magnetic permeability is almost exactly proportional to the cumulative conductance measured from the surface down to a depth h. Thus we can estimate an apparent conductivity, which we call the “imaged conductivity,” at depth to be [Formula: see text]. The cost of this transformation is a fraction of the cost of conventional data inversion, and it does not require an a priori constraint on the number of parameters used in the inversion. The empirically developed technique was used successfully to process UTEM field data measured over a quasi‐layered earth.

scholarly journals An Express Algorithm for Transient Electromagnetic Data Interpretation

Electronics ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 354 ◽  
Author(s):  
Roman Kaminskyj ◽  
Nataliya Shakhovska ◽  
Gregus Michal ◽  
Borys Ladanivskyy ◽  
Lidia Savkiv
Keyword(s):  
Experimental Data ◽  
Spline Approximation ◽  
Numerical Differentiation ◽  
Data Interpretation ◽  
Continuous Functions ◽  
Electromagnetic Data ◽  
Polynomial Coefficients ◽  
Transient Electromagnetic ◽  
1D Model ◽  
Tem Method

The transient electromagnetic (TEM) method is a time-domain, controlled source, electromagnetic (EM) geophysical technique which is often applied to image the subsurface conductivity distributions of shallow layers due to its effectiveness and adaptability to complex site working conditions. The means for an express analysis of such experimental data in several practical cases have advantages and are suitable for use. We developed our approach for determining the approximate one-dimensional (1D) model of background conductivity based on the formal transformation of the TEM experimental data and the mathematical analysis of continuous functions. Our algorithm, which allows the 1D model’s parameters to be obtained in terms of a layer’s thickness and resistivity, widely utilizes the numerical differentiation of experimental curves as well as of transformed ones. Since the noise level increases with time in the attenuating TEM signals and differentiation even enhances it, special procedures are required to calculate the derivative values. We applied the piecewise cubic spline approximation to solve this problem. In that case, the derivatives are obtained using polynomial coefficients which are available for each node. The application of the created facilities is demonstrated using real experimental data of the TEM soundings.

scholarly journals New method for denoising borehole transient electromagnetic data with discrete wavelet transform

2019 ◽  
Vol 168 ◽  
pp. 41-48 ◽  
Author(s):  
Xueping Dai ◽  
Li Zhen Cheng ◽  
Jean-Claude Mareschal ◽  
Daniel Lemire ◽  
Chong Liu
Keyword(s):  
Wavelet Transform ◽  
Discrete Wavelet Transform ◽  
New Method ◽  
Discrete Wavelet ◽  
Electromagnetic Data ◽  
Transient Electromagnetic
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