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.

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.

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

scholarly journals Numerical Modeling of the Effects of Electrode Spacing and Multilayered Concrete Resistivity on the Apparent Resistivity Measured Using Wenner Method

2020 ◽  
Author(s):  
Karthick Thiyagarajan ◽  
Parikshit Acharya ◽  
Lasitha Piyathilaka ◽  
sarath kodagoda
Keyword(s):  
Contact Area ◽  
Apparent Resistivity ◽  
Resistivity Measurement ◽  
Gaussian Process Regression ◽  
Electrode Spacing ◽  
Electrical Resistivity Measurement ◽  
Resistivity Measurements ◽  
Electrode Contact ◽  
Concrete Resistivity ◽  
Moisture Conditions

Smart Sensing technologies can play an important role in the conditional assessment of concrete sewer pipe linings. In the long-term, the permeation of acids can deteriorate the pipe linings. Currently, there are no proven sensors available to non-invasively estimate the depth of acid permeation in real-time. The electrical resistivity measurement on the surface of the linings can indicate the sub-surface acid moisture conditions. In this study, we consider acid permeated linings as a two resistivity layer concrete sample, where the top resistivity layer is assumed to be acid permeated and the bottom resistivity layer indicates normal moisture conditions. Firstly, we modeled the sensor based on the four-probe Wenner method. The measurements of the developed model were compared with the previous studies for validation. Then, the sensor model was utilized to study the effects of electrode contact area, electrode spacing distance and two resistivity layered concrete on the apparent resistivity measurements. All the simulations were carried out by varying the thickness of top resistivity layer concrete. The simulation study indicated that the electrode contact area has very minimal effects on apparent resistivity measurements. Also, an increase in apparent resistivity measurements was observed when there is an increase in the distance of the electrode spacing. Further, a machine learning approach using Gaussian process regression modeling was formulated to estimate the depth of acid permeated layer

scholarly journals Electrical Resistivity Profiles and Temperatures in the Ross Ice Shelf

1976 ◽  
Vol 16 (74) ◽  
pp. 307-308
Author(s):  
C.R. Bentley
Keyword(s):  
Electrical Resistivity ◽  
Computer Program ◽  
Depth Profile ◽  
Apparent Resistivity ◽  
Ice Shelf ◽  
Resistivity Measurements ◽  
Ross Ice Shelf ◽  
Field Season ◽  
A Site ◽  
Temperature Depth

AbstractDuring the 1973-74 Antarctic field season, two electrical resistivity profiles were completed along directions perpendicular to each other at a site in the south-easternpart of the Ross Ice Shelf. These profiles differ from each other only at short electrode spacings (less than 10 m) indicating no measurable horizontal anisotropy below the uppermost firn zone. The shape of the apparent resistivity curves is similar to that found by Hochstein on the Ross Ice Shelf near Roosevelt Island, but is displaced toward lower resistivities despite the colder 10 m temperature (—29°C instead of —26°C) at the more southerly site. Some factor other than temperature must therefore be effective in determining the overall magnitude of the resistivities in the shelf, although the variation with depth can still be expected to be primarily a temperature phenomenon.A computer program has been written to calculate apparent resistivities based on Crary’s analysis of temperatures in an ice shelf. Results are not yet available; when completed they should indicate the sensitivity of the resistivity measurements to differences in the temperature- depth profile, and hence their usefulness in estimating bottom melt/freeze rates.

DIRECT CURRENT RESISTIVITY MODELING FOR AXIALLY SYMMETRIC BODIES USING THE FINITE ELEMENT METHOD

Geophysics ◽  
1978 ◽  
Vol 43 (3) ◽  
pp. 550-562 ◽  
Author(s):  
H. M. Bibby
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Apparent Resistivity ◽  
Vertical Axis ◽  
Geothermal Field ◽  
Axially Symmetric ◽  
The Finite Element Method ◽  
Cross Sectional ◽  
Resistivity Anisotropy ◽  
Element Method

The finite element method is used to determine numerically the apparent resistivity anomaly caused by the presence of any body with a vertical axis of symmetry embedded in a uniform half‐space. The potential for a point source of current, and hence the apparent resistivity, is determined in the form of a Fourier series. The use of the finite element method enables certain classes of resistivity anisotropy to be modeled. Several examples of bipole‐dipole apparent resistivity enable us to examine assumptions that are necessarily made when inhomogeneities are approximated by models for which explicit solutions exist for the potential. An application to the Broadlands geothermal field suggests that the horizontal cross‐sectional area of the geothermal reservoir increases with depth, consistent with a decrease in the permeability with depth.

A PARADOX IN APPARENT RESISTIVITY MEASUREMENTS OVER A GROUND SECTION WITH CONDUCTIVE SUBSTRATUM

Geophysics ◽  
1974 ◽  
Vol 39 (1) ◽  
pp. 93-94 ◽  
Author(s):  
B. N. Satpathy
Keyword(s):  
Apparent Resistivity ◽  
Critical Value ◽  
Surface Electrode ◽  
Conductive Layer ◽  
Electrode Arrays ◽  
Opposite Result ◽  
Resistivity Measurements ◽  
Opposite Manner ◽  
Value Changes ◽  
Lower Resistivity

It is generally accepted that the resistivity of the top layer largely influences the apparent resistivity measured through conventional surface electrode arrays. Thus, intuitively it would be assumed that the overlaying of a conductive layer would give an apparent resistivity which is less than the value obtained without the conducting cover and an opposite result would be obtained by introducing a resistive top layer. Though this belief is valid for many geoelectric sections, it is here shown that for a two‐layer section with [Formula: see text], if the top portion of the first layer is replaced with a layer of higher or lower resistivity, the apparent resistivity value changes in an opposite manner after a critical value of the electrode separation: the apparent resistivity for large separations is decreased due to the introduction of the resistive top layer. It is intended in this note to elucidate this paradox through a suitable example.

Square array resistivity anomalies and inhomogeneity ratio calculated by the finite‐element method

Geophysics ◽  
1997 ◽  
Vol 62 (2) ◽  
pp. 426-435 ◽  
Author(s):  
Gregory N. Tsokas ◽  
Panagiotis I. Tsourlos ◽  
John E. Szymanski
Keyword(s):  
Finite Element ◽  
Apparent Resistivity ◽  
Careful Consideration ◽  
The Finite Element Method ◽  
Array Configuration ◽  
Strike Direction ◽  
Directional Variation ◽  
Types Of Information ◽  
Square Array ◽  
Subsurface Resistivity

In this work the square array configuration is studied. As with any four‐electrode measuring configuration, three different resistances can be measured directly and, in particular, by using the square array these resistance values can be used to obtain a measure of the apparent anisotropy: this is the so‐called azimuthal inhomogeneity ratio (AIR). The AIR is used widely to derive information regarding the directional variation of the subsurface resistivity. Similar types of information can be obtained using any collinear array but would need to be used in a crossed mode. This gives an operational advantage to the square array. Here, the AIR and the square α and β apparent resistivities have been calculated for a number of simple subsurface models. Moreover, the apparent resistivity responses for several different linear arrays were calculated to allow useful comparisons. The forward modeling has been carried out via a 2.5-D finite‐element scheme and an existing approach has been modified in order to calculate the potential variations parallel to the strike direction. Here, the use of AIR as a pattern recognition tool is investigated. The AIR anomalies are shown to delineate the edges of the targets successfully, retaining the same pattern when the model was shifted in depth, and indicating a satisfactory resolving ability. The AIR can be used as complementary information to the apparent resistivity measures and can improve the interpretation. However, careful consideration has to be given to the data noise.

scholarly journals Experimental Studies on the Changes in Resistivity and Its Anisotropy Using Electrical Resistivity Tomography

2012 ◽  
Vol 2012 ◽  
pp. 1-10
Author(s):  
Tao Zhu ◽  
Jian-Guo Zhou ◽  
Jin-Qi Hao
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Large Scale ◽  
Electrical Resistivity Tomography ◽  
Experimental Studies ◽  
Major Axis ◽  
Residual Resistivity ◽  
Resistivity Tomography ◽  
D Region ◽  
Resistivity Anisotropy

Three measuring lines were arranged on one of free planes of magnetite cuboid samples. Apparent resistivity data were acquired by MIR-2007 resistivity meter when samples were under uniaxial compression of servocontrol YAW-5000F loadingmachine in laboratory. Then we constructed the residual resistivity images using electrical resistivity tomography (ERT) and plotted the diagrams of apparent resistivity anisotropy coefficient (ARAC)λ∗and the included angleαbetween the major axis of apparent resistivity anisotropy ellipse and the axis of load with pressure and effective depth. Our results show that with increasing pressure, resistivity and the decreased (D region) and increased (I region) resistivity regions have complex behaviors, but when pressure is higher than a certain value, the average resistivity decrease and the area of D region expand gradually in all time with the increase of pressure, which may be significant to the monitoring and prediction of earthquake, volcanic activities, and large-scale geologic motions. The effects of pressure onλ∗andαare not very outstanding for dry magnetite samples.

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