QUADRIPOLE‐QUADRIPOLE ARRAYS FOR DIRECT CURRENT RESISTIVITY MEASUREMENTS—MODEL STUDIES

Geophysics ◽  
1976 ◽  
Vol 41 (1) ◽  
pp. 79-95 ◽  
Author(s):  
Dariu Doicin
Keyword(s):  
Half Space ◽  
Electric Fields ◽  
Direct Current ◽  
Apparent Resistivity ◽  
Cross Product ◽  
Resistivity Measurements ◽  
Model Studies ◽  
True Resistivity ◽  
Vertical Contact ◽  
Source Dipole

For a quadripole‐quadripole array, in which current is sequentially injected into the ground by two perpendicular dipoles, an apparent resistivity can be defined in terms of the vectorial cross product of the two electric fields measured at the receiver site. Transform equations are derived (for horizontally layered media) which relate this apparent resistivity to the apparent resistivities obtained with conventional dipole‐dipole and Schlumberger arrangements. To evaluate the method, two mathematical models are used. The first model is a half‐space with an “alpha conductivity center,” and the second model is a half‐space with a vertical contact. For an idealized quadripole‐quadripole array, simple expressions are found for the apparent resistivity, which is shown to be independent of the orientation of the current quadripole. Theoretical anomalies calculated for the quadripole‐quadripole array are compared with those obtained for a dipole‐quadripole array. It is shown that whereas the apparent resistivity map for the dipole‐quadripole array varies greatly with the azimuth of the source dipole, the results obtained with the quadripole‐quadripole array consistently display a remarkable resemblance to the assumed distribution of true resistivity. This is especially true when the current quadripole is placed at a large distance from the surveyed area.

The differential parameter method for multifrequency airborne resistivity mapping

Geophysics ◽  
1996 ◽  
Vol 61 (1) ◽  
pp. 100-109 ◽  
Author(s):  
Haoping Huang ◽  
Douglas C. Fraser
Keyword(s):  
Half Space ◽  
Apparent Resistivity ◽  
Skin Depth ◽  
Parameter Method ◽  
Apparent Depth ◽  
Analytic Method ◽  
Geologic Mapping ◽  
Depth Images ◽  
True Resistivity ◽  
Differential Parameter

Helicopter EM resistivity mapping began to be accepted as a means of geologic mapping in the late 1970s. The data were first displayed as plan maps and images. Some 10 years later, sectional resistivity displays became available using the same “pseudolayer” half‐space resistivity algorithm developed by Fraser and the new centroid depth algorithm developed by Sengpiel. Known as Sengpiel resistivity sections, these resistivity/depth images proved to be popular for the display of helicopter electromagnetic (EM) data in conductive environments. A limitation of the above resistivity and depth algorithms is that the resulting Sengpiel section may imply that the depth of exploration of the EM system is substantially less than is actually the case. For example, a target at depth may be expressed in the raw data, but its appearance on the Sengpiel section may be too shallow (which is a problem with the depth algorithm), or it may not even appear at all (which is a problem with the resistivity algorithm). An algorithm has been adapted from a ground EM analytic method that yields a parameter called the differential resistivity, which is plotted at the differential depth. The technique yields the true resistivity when the half‐space is homogeneous. It also tracks a dipping target with greater sensitivity and to greater depth than does the Sengpiel display method. The input parameters are the apparent resistivity and apparent depth from the pseudolayer half‐space algorithm and the skin depth for the various frequencies. The output parameters are differential resistivity and differential depth, which are computed from pairs of adjacent frequencies.

On: “The interpretation of direct current resistivity measurements” by D. W. Oldenburg (GEOPHYSICS, April 1978, p. 610–625)

Geophysics ◽  
1982 ◽  
Vol 47 (2) ◽  
pp. 264-265 ◽  
Author(s):  
D. Guptasarma
Keyword(s):  
Characteristic Function ◽  
Half Space ◽  
Direct Current ◽  
Layered Medium ◽  
Inverse Theory ◽  
Dc Resistivity ◽  
Vertical Variation ◽  
Resistivity Sounding ◽  
Resistivity Measurements

Oldenburg made an excellent example of the application of linearized inverse theory to invert dc resistivity sounding data to fit a continuous vertical variation of resistivity. In the Introduction he mentioned that the Frechet kernels for resistivity are the same as the depth investigation characteristic function (DIC) used by Roy and Apparao (1971). In the second part of the paper, he showed that it is so for a uniformly conducting half space. He mentioned that the electrostatic analog which was used (by Roy and Apparao) becomes quite complex when a layered medium is introduced, and that the extension to a continuous ρ(z) would be a difficult task (p. 623).

The effect of structure and anisotropy on resistivity measurements

Geophysics ◽  
1986 ◽  
Vol 51 (4) ◽  
pp. 964-971 ◽  
Author(s):  
M. J. S. Matias ◽  
G. M. Habberjam
Keyword(s):  
Apparent Resistivity ◽  
Field Experience ◽  
Resistivity Measurements ◽  
Model Studies ◽  
Array Measurements ◽  
Resistivity Anisotropy ◽  
Square Array ◽  
Effect Of Structure

When conducting resistivity investigations over steeply dipping geologic structures, large orientational variations in resistivity response are commonly encountered. These variations can arise from resistivity contrasts between constituent layers or from anisotropy within the beds. When such structures are concealed, a thorough sampling of these orientational variations must be conducted. Field experience and model studies have shown that such sampling can be conveniently conducted using the crossed‐square array and that the orientational variations encountered can be adequately summarized by the anisotropically defined parameters of apparent resistivity, anisotropy, and strike derived from these array measurements.

INTERPRETATION OF BURIED ELECTRODE RESISTIVITY DATA USING A LAYERED EARTH MODEL

Geophysics ◽  
1978 ◽  
Vol 43 (5) ◽  
pp. 988-1001 ◽  
Author(s):  
Jeffrey J. Daniels
Keyword(s):  
Direct Current ◽  
Field Data ◽  
Apparent Resistivity ◽  
Current Source ◽  
Well Logs ◽  
Earth Model ◽  
Layered Earth ◽  
Resistivity Data ◽  
True Resistivity ◽  
Resistivity Logging

The layered earth model is a fundamental interpretation aid for direct current resistivity data. This paper presents a solution for the layered earth problem for a buried current source and a buried receiver. The model is developed for source and receiver electrodes buried anywhere within a horizontally stratified layered earth containing an arbitrary number of resistivity layers. Model results for the normal well‐logging array indicate that large departures between true and apparent resistivity can be caused by thin beds or highly resistant layers. A true resistivity distribution from well logs can be established by modeling when the effects from borehole rugosity and fluid resistivity are negligible. The equations derived for resistivity well logs can be used to interpret hole‐to‐hole, hole‐to‐surface, and conventional surface array data. A field example demonstrates that deviations between hole‐to‐hole field data and model results, based on well logs in the receiver hole, can be accounted for by combining the resistivity logging models in the receiver holes with information from geologic logs. Differences between the field data and the layered‐model results are attributed to lateral changes between or near the source and receiver holes.

scholarly journals Use of Direct Current Resistivity Measurements to Assess AISI 304 Austenitic Stainless Steel Sensitization

2015 ◽  
Vol 18 (2) ◽  
pp. 341-346 ◽  
Author(s):  
Ramaiany Carneiro Mesquita ◽  
José Manoel Rivas Mecury ◽  
Auro Atsumi Tanaka ◽  
Regina Célia de Sousa
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Direct Current ◽  
Aisi 304 ◽  
Resistivity Measurements ◽  
304 Austenitic Stainless Steel

scholarly journals Corrections of surface fissure effect on apparent resistivity measurements

2014 ◽  
Vol 200 (2) ◽  
pp. 1118-1135 ◽  
Author(s):  
J. Gance ◽  
P. Sailhac ◽  
J.-P. Malet
Keyword(s):  
Apparent Resistivity ◽  
Resistivity Measurements

Airborne resistivity and susceptibility mapping in magnetically polarizable areas

Geophysics ◽  
2000 ◽  
Vol 65 (2) ◽  
pp. 502-511 ◽  
Author(s):  
Haoping Huang ◽  
Douglas C. Fraser
Keyword(s):  
Half Space ◽  
Magnetic Permeability ◽  
Apparent Resistivity ◽  
Dynamic Range ◽  
Single Frequency ◽  
Measured Signal ◽  
Apparent Permeability ◽  
Quadrature Component ◽  
New Methods ◽  
Quadrature Response

The apparent resistivity technique using half‐space models has been employed in helicopter‐borne resistivity mapping for twenty years. These resistivity algorithms yield the apparent resistivity from the measured in‐phase and quadrature response arising from the flow of electrical conduction currents for a given frequency. However, these algorithms, which assume free‐space magnetic permeability, do not yield a reliable value for the apparent resistivity in highly magnetic areas. This is because magnetic polarization also occurs, which modifies the electromagnetic (EM) response, causing the computed resistivity to be erroneously high. Conversely, the susceptibility of a magnetic half‐space can be computed from the measured EM response, assuming an absence of conduction currents. However, the presence of conduction currents will cause the computed susceptibility to be erroneously low. New methods for computing the apparent resistivity and apparent magnetic permeability have been developed for the magnetic conductive half‐space. The in‐phase and quadrature responses at the lowest frequency are first used to estimate the apparent magnetic permeability. The lowest frequency should be used to calculate the permeability because this minimizes the contribution to the measured signal from conduction currents. Knowing the apparent magnetic permeability then allows the apparent resistivity to be computed for all frequencies. The resistivity can be computed using different methods. Because the EM response of magnetic permeability is much greater for the in‐phase component than for the quadrature component, it may be better in highly magnetic environments to derive the resistivity using the quadrature component at two frequencies (the quad‐quad algorithm) rather than using the in‐phase and quadrature response at a single frequency (the in‐phase‐quad algorithm). However, the in‐phase‐quad algorithm has the advantage of dynamic range, and it gives credible resistivity results when the apparent permeability has been obtained correctly.

Sign in / Sign up

Export Citation Format

Share Document