Spontaneous potential

Other logs employed to determine N/G ratio include the spontaneous potential (SP) log and the microlog, which differentiate permeable from non-permeable intervals. The N/ G ratio can also be measured directly on cores if there is visible contrast between the reservoir and non-reservoir sections, or from permeability measurements on core samples, providing sample coverage is sufficient. 

Switzer et al. found that CU/CU2O layered nanostructures are electrodeposited with spontaneous potential oscillations from alkaline Cu(II)-lactate solution in a self-... 

Eskhult, J., Herranen, M. and Nyholm, L. (2006) On the origin of the spontaneous potential oscillations observed during galvanostatic deposition oflayers of Cu and CU2O in alkaline citrate solutions. J. Electroanal. Chem., 594, 35-39. 

J. O. (2001) Spontaneous potential oscillations in the Cu(II)/tartrate and lactate systems, aspects of mechanisms and film deposition. J. Electrochem. Soc., 148, C513-C517. 

In this chapter, novel oscillations observed with liquid membrane systems by the present authors [22-25] will be introduced, and the mechanisms for the oscillation are clarified by using VITIES, taking into consideration ion transfer reactions and adsorptions at two aqueous-membrane interfaces. The mechanism of the spontaneous potential oscillation in a liquid membrane system proposed by Yoshikawa et al. is also discussed briefly. 

Quantal analysis defines the mechanism of release as exocytosis. Stimulation of the motor neuron causes a large depolarization of the motor end plate. In 1952, Fatt and Katz [11] observed that spontaneous potentials of approximately 1 mV occur at the motor endplate. Each individual potential change has a time course similar to the much larger evoked response of the muscle membrane that results from electrical stimulation of the motor nerve. These small spontaneous potentials were therefore called... 

Most notably, subtle positive spontaneous potential (SP) anomalies can be noted in association with strong, negative-inward, redox gradients (Hamilton Hattori 2008). The goal of our work is to understand the role of micro-organisms in the oxidation process and in the generation of electrical fields. 

Hamilton, S.M. Hattori, K.H. 2008. Spontaneous potential and redox responses over a forest ring. Geophysics, 73, B67-B75. 

Fig. 18. Oil well logging provides valuable information on the down-hole" characteristics of oil and gas wells. Spontaneous potential (SP). electrical resistivity/conductivity logs are frequently recorded simultaneously...

Spontaneous potential Caliper log Compared to a free gas bearing zone, the spontaneous potential log is less negative, but similar to that of ice An oversized drill hole is indicated by hydrate dissociation. This may also occur with ice in the permafrost. However, as noted by Kleinberg (Personal Communication, July 20, 2006) In some circumstances, hydrates can be a good cement (until it dissociates), and strengthen the unconsolidated host sediment ... 

Figure 50 Electrochemical noise (spontaneous potential and current fluctuations) associated with the metastable pitting of austenitic stainless steel. (From Ref. 57.)...

SEI rolytic ceii - an electrochemical cell. -f,in which reactions are driven by the, application of an external voltage greater , ohan the spontaneous potential of the ... 

Salinity. Synonymous with total dissolved solids (TDS), generally reported in milligrams per liter (mg L ) as determined either (i) directly by summing measured dissolved constituents or by weighing solid residues after evaporation, or (ii) indirectly from electrical conductivity or spontaneous potential response. 

The salinity of formation waters is often calculated using electrical-resistivity and spontaneous-potential (SP) logs, and the values obtained are reasonable, except in geopressured zones with high shale content (Hearst and Nelson, 1985 Rider, 1996). It is often possible to determine vertical variations in salinity over a distance of several kilometers from a single log. 

The existence of spontaneous potentials in the Earth has been known for at least 150 years and their measurement has been used systematically in the search for buried ore deposits since the 1920s (Parasnis, 1979). Spontaneous or self potentials (SP) are natural voltage differences between two points in the Earth which result in electrical... 

Fig. 3-3. Non-polarising CU-CUSO4 electrodes for measurement of spontaneous potentials in surface materials. If the ground at A is more reducing than the ground at B , a potential difference exists between the two electrodes and current in the wire is possible.

All moist Earth materials contain redox-active species, such as 02(aq>, Fe, HS", OH and which impart a bulk redox capacity, or Eh if measured against the H -H2 halfcell, to the soil or groundwater. The variable chemical composition of overburden, groundwater and rock therefore results in variable redox capacity which, in turn, results in spontaneous potential voltages and currents between different points in the Earth. The multitude of potential processes that affect the composition of Earth materials and might thereby affect redox processes can be divided into primary lithological processes and surficial processes. 

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