Recent Developments in Deep Sea Electrical Resistivity Probings - Its Application to The Sedimentary Study of the Red Sea Hot Brines

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Abstract
INTRODUCTION Previous studies have been made of the mass physical properties and the electrical resistivity of marine sediments. A third degree polynomial curve was found to, be the best fit for data relating porosity and the formation factor, which is the ratio of the bulk resistivity of marine sediments to the resistivity of interstitial water. An electrical resistivity probe has already been successfully used to obtain in-situ profiles of resistivity vs depth. A new instrument is now described where a similar principle is used for the study of the lithology of the Red Sea hot brines. In order to increase the definition of the measurements, the new probe is provided with a focused resistivity measuring device, that is less affected by borehole effects. This new probe is devised to operate in an environmental temperature of 700C and a salinity of 35 percent of salt content in water as well as in the interstitial water of the sediments. PREVIOUS DEVELOPMENTS IN THIS FIELD General Archie,1 Rust (1952), Atkins2 and Kermabon4 successful correlated some physical parameters of reservoir rocks in sedimentary strata with their electrical resistivity. The sandstones investigated had porosities ranging from 10 to 40 percent and were saturated with brine of known salinity. The following simple relation was defined. (Mathematical equation available in full paper) where Re is the resistivity of the sand when all the pores are filled with brine, Rw the resistivity of the brine, and F a formation resistivity factor. F appeared to be a function of the type and character of the formation, and varied among other properties with the porosity of the reservoir rock. A reasonably accurate relationship was found between the porosity and density. Thus, knowing the porosity of the sand in question, a fair estimate of the value of F may be given by the empirical relationship, (Mathematical equation available in full paper) where n is the porosity fraction of the sand. The value of m was found to range between 1.and 2. Correlation Between Porosity and the Electrical Properties of Some Deep Sea Sediments Correlation Between Porosity and the Electrical Properties of Some Deep Sea Sediments Cores were taken from the Tyrrhenian abyssal plain, and the mass physical properties of these cores were correlated with the' electrical formation factor. The sampler used was a wide-diameter sphincter corer and a special analysis bench (Fig. 1) was developed the following measurements were taken:porosity,wet (bulle) density andelectrical resistivity (formation factor). The well known linear relationship between porosity and wet (bulk) density was controlled (Fig. 2). From the results of 10 cores, the following regression was found: d = 2.60 - 0.0158n where d is wet density and n is porosity. By plotting the formation factor vs porosity, derived from2,500 measurements made on cores collected in the Tyrrhenian Sea, several regression curves were obtained.

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