Measuring techniques in induced polarisation imaging

Abstract

Multi-electrode geoelectrical imaging has become very popular and is used for many different purposes. For some of these, the inclusion of IP data would be desirable as it would allow the interpreter to distinguish between, e.g. sand formations with saltwater infiltration and clay formations or help delineate landfills. However, present-day IP measuring techniques require the use of nonpolarisable potential electrodes and special wire layout and are thus cumbersome and expensive. In this paper, we suggest making IP measurements with multi-electrode cables and just one set of steel electrodes. The polarisation potentials on the potential electrodes are corrected for by subtracting the polarisation potential measured when no primary current and no IP signal are present. Test measurements indicate that the polarisation potentials vary slowly and that the correction procedure is feasible. At two sites in southern Sweden, we have compared measurements with only stainless steel electrodes and measurements with both stainless steel and Pb -PbCl nonpolarisable electrodes using one or two sets of multicore cables, respectively. Almost no difference between the two data sets was observed. At one site, the charge-up effect on the potential electrodes was not important, while at the other site, the correction procedure was crucial. Though only two sites have been studied so far, it seems that time-domain IP imaging measurements can be taken with only steel electrodes and ordinary multicore cables. Coupling in the multicore cables has not presented any problems at the investigated sites where grounding resistances were moderate, making the coupling effect small. High grounding resistance sites have not yet been investigated. D 2002 Published by Elsevier Science B.V.

Numerical Modelling for Improvement of the Interpretation of Geoelectrical and Induced Polarization Measurements

“…The minerals can also have a needle-shape and be parallel oriented (Wikman and Bergström, 1987). The water decreases the resistivity in the fracture zone and as mentioned in Dahlin et al (2002) the mineralization increases the IP effect of the zone. The resistivity log also showed that fracturing of the gneiss decreases the resistivity considerably.…”

Data Quality Quantification for Time Domain IP Data Acquired along a Planned Tunnel near Oslo, Norway

“…The area is geologically complex with volcanic rocks including porphyry, basalt and dolerite dykes, plus faults and weathering. The electrode separation was 10 m giving a total layout of 800 m. Stainless steel electrodes were used throughout following results from Dahlin et al (2002). The mean electrode contact resistance was ranging from 0.6 to 25 kΩ, with a mean of 4.7 kΩ.…”

Mapping landfill gas migration using resistivity monitoring

“…The time for the 50% duty injection cycle was 1 s, which is sufficiently short to make it possible to measure all the lines (3888 measurements) within about 1 h and 45 min, and also sufficiently long to allow for the potential to stabilise. Charge-up and polarisation effects are notoriously important at landfills (Carlson et al 1999;Dahlin et al 2002;Leroux et al 2007) and measuring too hastily can result in underestimating the resistivity. The data have to be processed by inversion before a resistivity image of the studied area can be produced.…”

“…An indication for that is the high induced polarisation usually measured on municipal landfills (see e.g. Carlson et al, 1999;Dahlin et al, 2002;Leroux et al, 2007). Other models such as the equation proposed by Waxman and Smits (1968) might then better describe the electrical resistivity in such materials.…”