SALT BED IDENTIFICATION FROM UNFOCUSED RESISTIVITY LOGS

Geophysics ◽  
1961 ◽  
Vol 26 (3) ◽  
pp. 320-341
Author(s):  
J. R. Lishman
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Borehole Diameter ◽  
Drilling Fluids ◽  
Characteristic Shape ◽  
Resistivity Logs

Salt beds have almost infinite electrical resistivity. They differ from other infinitely resistive beds in that they are usually soluble in drilling fluids, and give rise to enlarged boreholes. An infinitely resistive bed lying between shales may be recognized from the characteristic shape of the electric log resistivity curves, and the ratios of their readings. Any one of the curves may then be used to compute the borehole diameter, and hence decide whether the bed is salt. Where a washed out salt bed is adjacent to another infinitely resistive bed in which the borehole is to gauge, the configuration of the curves is very characteristic. Apparent resistivity ratios again help to identify the salt.

A Walsh sequency filtration method for integrating the resistivity log and sounding data

Geophysics ◽  
1991 ◽  
Vol 56 (8) ◽  
pp. 1259-1266 ◽  
Author(s):  
Poorna C. Pal
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Groundwater Exploration ◽  
Walsh Functions ◽  
Filtration Method ◽  
Resistivity Logs ◽  
Logarithmic Scaling ◽  
Input Model ◽  
Resistivity Log

The integration of resistivity logs and soundings data, essential for resolving the problems of ambiguity and nonuniqueness ubiquitous in the interpretation of electrical resistivity soundings, is generally difficult because the former contain far more details than can be retrieved from the latter. As logarithmic scaling linearizes the behavior of apparent resistivity values and resistivity transform functions, and as the Walsh functions realistically mimic the resistivity logs, the strategy proposed here is to use the resistivity‐stratigraphy schematized from Walsh‐filtration of logarithmically scaled logs‐profile as input model for sounding interpretation. The efficiency of this strategy is demonstrated here with a practical example from groundwater exploration. The synthetic sounding curve based on 29 layers manually schematized from the observed linearly scaled logs‐profile could be modeled by 8 layers, whereas that computed from 14 layers schematized from sequency‐filteration of the logarithmically scaled logs‐profile closely matched the observed sounding curve from a nearby location.

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.

Applications and advantages of the Slingram electromagnetic method for archaeological prospecting

Geophysics ◽  
1986 ◽  
Vol 51 (3) ◽  
pp. 576-584 ◽  
Author(s):  
Alain Tabbagh
Keyword(s):  
Electrical Resistivity ◽  
Magnetic Susceptibility ◽  
Apparent Resistivity ◽  
Electromagnetic Method ◽  
Grid Technique ◽  
Types Of Information ◽  
Mesh Grid ◽  
Apparent Susceptibility ◽  
Depth Of Investigation ◽  
Measurement Capabilities

The electromagnetic Slingram method can provide three types of information simultaneously: (1) the apparent resistivity of the ground; (2) its apparent susceptibility; and (3) the characteristic signatures of buried metallic objects. To build an apparatus with these three measurement capabilities requires an appropriate choice of parameters, including frequency, coil separation, and coil orientation as well as calculations which take into account the electrical resistivity and the magnetic susceptibility of the ground. The value of the Slingram method for archaeological applications is shown by two examples: (1) a Gallo‐Roman pottery workshop investigated with measurements of the apparent susceptibility using a reduced sampling wide mesh grid technique; and (2) the study of a Bronze hoard site located in a marsh. Capabilities of the Slingram method may be improved by further study of an apparatus using several receivers which would increase the depth of investigation. Use of several frequencies would overcome difficulties related to resolving the magnetic quadrature susceptibility.

Inversion of borehole normal resistivity logs

Geophysics ◽  
1984 ◽  
Vol 49 (9) ◽  
pp. 1541-1548 ◽  
Author(s):  
Fang‐Wei Yang ◽  
Stanley H. Ward
Keyword(s):  
Theoretical Model ◽  
Ridge Regression ◽  
Arbitrary Number ◽  
Inverse Method ◽  
Apparent Resistivity ◽  
Random Noise ◽  
High Resistivity ◽  
Number Of Layers ◽  
Boundary Position ◽  
Resistivity Logs

This paper reports on an investigation of the inversion of borehole normal resistivity data via ridge regression. Interpretation is afforded of individual thin beds and of complicated layered structures. A theoretical solution is given for a layered model containing an arbitrary number of layers in the forward problem. Two forward model results for resistive and conductive thin beds indicate that for high‐resistivity contrasts, the departure between true and apparent resistivity may be more important than the effects caused by the variations in borehole diameter and mud resistivity. Four normal resistivity logs were chosen to test the inversion scheme. Two of the logs were theoretical logs with and without random noise added, and the remaining two were field examples. Theoretical model results and field examples indicate that the inverse method can be used to obtain the resistivity for each layer when the boundary position is known, but it also can be used to obtain the thickness and resistivity for each layer simultaneously.

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.

scholarly journals Two-dimensional Electrical Resistivity Tomography of Bitumen Occurrence in Agbabu, Southwest Nigeria

2019 ◽  
pp. 1-9
Author(s):  
O. F. Ogunlana ◽  
O. M. Alile ◽  
O. J. Airen
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Electrical Resistivity Tomography ◽  
Electrode Spacing ◽  
Southwestern Nigeria ◽  
Resistivity Tomography ◽  
2D Inversion ◽  
Earth Resistivity ◽  
Southwest Nigeria ◽  
Resistivity Meter

The Electrical Resistivity Tomography (ERT) data was acquired within the area suspected to have high potential for bitumen occurrence using the Wenner-Schlumberger configuration in Agbabu, southwestern Nigeria. PASI 16GL-N Earth resistivity meter instrument was used to acquire data along five (5) traverses with 5m electrode spacing and traverses length of 150m. The apparent resistivity values obtained was processed using RES2DINV software which helped to automatically obtain the 2D inversion model of the subsurface. This study has shown the occurrence of bitumen between the depth of 13.4m and 9.93m for Traverses 1, 2, 3 and Traverses 4, 5 respectively in a 2-Dimensional electrical resistivity images for boreholes with a depth of about 18m. The results indicate that the bitumen is characterized by good lateral continuity and is sufficiently thick for commercial exploitation.

scholarly journals Electrical resistivity tomography for aquifer imaging

2000 ◽  
Vol 22 ◽  
Author(s):  
Dipak Raj Pant
Keyword(s):  
Electrical Resistivity ◽  
Cross Section ◽  
Electrical Resistance ◽  
Apparent Resistivity ◽  
Electrical Resistivity Tomography ◽  
Field Experiments ◽  
Region Of Interest ◽  
Electrical Energy ◽  
Resistivity Tomography ◽  
Computerised Analysis

Aspects related to the development of a technique called electrical resistance tomography for producing two- or three­ dimensional subsurface images of an aquifer have been discussed. The technique is based on the automated measurement and computerised analysis of electrical resistivity changes caused by natural or man-made processes. A subsurface region of the aquifer to be studied is sampled by transmitting electrical energy through it along many paths of known orientations, and the apparent resistivity data derived are used to construct a cross-section al image of the region of interest. The physical model experiments and field experiments show that the presented method is effective and flexible for crosshole resistivity imaging of aquifer with bipole-bipole electrode configurations.

scholarly journals Exploring the regolith with electrical resistivity tomography in largescale surveys: electrode spacing related issues and possibility

2020 ◽  
Author(s):  
Laurent Gourdol ◽  
Rémi Clément ◽  
Jérôme Juilleret ◽  
Laurent Pfister ◽  
Christophe Hissler
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Large Scale ◽  
Electrical Resistivity Tomography ◽  
Subsurface Layer ◽  
Electrode Spacing ◽  
High Resistivity ◽  
Constant Thickness ◽  
Resistivity Tomography

Abstract. Within the Critical Zone, regolith plays a key role in the fundamental hydrological functions of water collection, storage, mixing and release. Electrical Resistivity Tomography (ERT) is recognized as a remarkable tool for characterizing the geometry and properties of the regolith, overcoming limitations inherent to conventional borehole-based investigations. For exploring shallow layers, a small electrode spacing (ES) will provide a denser set of apparent resistivity measurements of the subsurface. As this option is cumbersome and time-consuming, smaller ES – albeit offering poorer shallow apparent resistivity data – are often preferred for large horizontal ERT surveys. To investigate the negative trade-off between larger ES and reduced accuracy of the inverted ERT images for shallow layers, we use a set of synthetic conductive/resistive/conductive three-layered soil–saprock/saprolite–bedrock models in combination with a reference field dataset. Our results suggest that an increase in ES causes a deterioration of the accuracy of the inverted ERT images in terms of both resistivity distribution and interface delineation and, most importantly, that this degradation increases sharply when the ES exceeds the thickness of the top subsurface layer. This finding, which is obvious for the characterization of shallow layers, is also relevant even when solely aiming for the characterization of deeper layers. We show that an oversized ES leads to overestimations of depth to bedrock and that this overestimation is even more important for subsurface structures with high resistivity contrast. To overcome this limitation, we propose adding interpolated levels of surficial apparent resistivity relying on a limited number of ERT profiles with a smaller ES. We demonstrate that our protocol significantly improves the accuracy of ERT profiles when using large ES, provided that the top layer has a rather constant thickness and resistivity. For the specific case of large-scale ERT surveys the proposed upgrading procedure is cost-effective in comparison to protocols based on small ES.

scholarly journals STRUCTURE OF FREEZING TALIK UNDER LAKE AT THE PARISENTO FIELD STATION (GYDAN PENINSULA) ACCORDING TO ELECTRICAL RESISTIVITY TOMOGRAPHY

2019 ◽  
Vol 2 (2) ◽  
pp. 103-110
Author(s):  
Alexandr Shein ◽  
Vladimir Olenchenko ◽  
Yaroslav Kamnev ◽  
Anton Sinitskiy
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Electrical Resistivity Tomography ◽  
Two Dimensional ◽  
Resistivity Tomography ◽  
Field Station ◽  
Approximate Rate

The article presents the results of studies of freezing talik under lake with using of electrical resistivity tomography. The research was conducted on one of paleolake – khasyrey. The measurements performed in two perpendicular profiles by pole-dipole array with a maximum spacing of 435 m. According to results of two-dimensional inversion, an area of low electrical resistivity of rocks at a depth of 25-30 m associated with a freezing talik under lake was identified. It was determined that the depth of freezing within drained lake for the period from 1996 to 2018 is 17-22 m. The approximate rate of freezing is 1 m/year. Formation of talik have a resistance of 5-15 Ω·m. Frozen formations in the contours of young paleolake have apparent resistivity hundreds Ω·m. Within the boundaries of the more ancient khasyrey apparent resistivity of the frozen rocks up to several thousand Ω·m.

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