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Geophysical Applications
Published in Stephen M. Testa, Geological Aspects of Hazardous Waste Management, 2020
Spontaneous-potential (SP) logs record the DC voltage differences between the naturally occurring potential of moveable electrodes in the borehole and the potential of a fixed electrode at the surface. Measured in millivolts, SP logging techniques have been used widely in the oil fields but have been restricted in use in fresh groundwater environments. SP is used to identify impermeable and permeable zones such as shale and sand, respectively, as well as the boundaries of permeable beds. In addition, SP logs can also be used to determine formation water resistivity (Rw), the volume of shale (Vsh) in permeable beds, and detection of hydrocarbon. Suppression of the SP response can be indicative of thin beds (i.e., less than 10 ft), shaliness, and/or the presence of hydrocarbon or gas. The SP log is influenced, however, by bed thickness and resistivity, invasion, borehole diameter, shale content, and the ratio of Rmf/Rw.
Subsurface Exploration, Sampling, and Mapping
Published in Christopher M. Palmer, Principles of Contaminant Hydrogeology, 2019
Geophysical logs are done in the open uncased borehole, and some logs (such as resistivity) require flooding the borehole. Geophysical logs that have general use in the groundwater studies are: Resistivity — used to identify porous (sandy) sediment.Spontaneous Potential — used to locate clay and sand strata.Natural Gamma — used for lithology and to distinguish sand and clay strata.Caliper — used to measure the borehole circumference and locate areas of erosion.Drift — used to measure the inclination and position of the borehole bottom.
Geophysical logging
Published in Ian Acworth, Investigating Groundwater, 2019
The SP log is a record of electrical potentials that develop at the contacts between shale or clay beds and a sand aquifer. The chief sources of spontaneous potential in the borehole are electrochemical and electrokinetic or streaming potentials. Electrochemical effects, which are probably the more significant, can be further subdivided into membrane and liquid-junction potentials. The SP log is often run as part of a wider logging suite including the 16-inch and 64-inch logs described below. However, in its simplest form, it is the output of a millivolt meter connected to a chart recorder with inputs provided by the down-hole electrode and a surface electrode.
Influence of activated carbon on crevice corrosion in adsorption tower of advanced liquid processing system
Published in Corrosion Engineering, Science and Technology, 2018
Yoshikazu Maeda, Hiroshi Abe, Yutaka Watanabe
The Cl− concentration of salt water is increased by RO treatment, and this results in an increase in the susceptibility to localised corrosion. In adsorption towers of ALPS, crevice corrosion of 316L stainless steel (SS) that is used in piping flange occurred in Ag-impregnated activated carbon (Ag AC) adsorption towers where neutral and alkaline solutions are present (see Figure 2). The high Cl− concentrations and Ag AC promote crevice corrosion [2]. It is known that crevice corrosion can occur when the spontaneous potential (Esp) is higher than the critical potential for crevice corrosion initiation. In this study, the influence of AC on Esp and the crevice corrosion susceptibility of 316L SS were investigated by performing electrochemical experiments.