Lev Eppelbaum

Crustal structure of the Levant Basin, eastern Mediterranean

Abstract A seismic refraction/wide-angle reflection experiment was undertaken in the Levant Basin, eastern Mediterranean. Two roughly east–west profiles extend from the continental shelf of Israel toward the Levant Basin. The northern profile crosses the Eratosthenes Seamount and the southern profile crosses several distinct magnetic anomalies. The marine operation used 16 ocean bottom seismometers deployed along the profiles with an air gun array and explosive charges as energy sources. The results of this study strongly suggest the existence of oceanic crust under portions of the Levant Basin and continental crust under the Eratosthenes Seamount. The seismic refraction data also indicate a large sedimentary sequence, 10–14 km thick, in the Levant Basin and below the Levant continental margin. Assuming the crust is of Cretaceous age, this gives a fairly high sedimentation rate. The sequence can be divided into several units. A prominent unit is the 4.2 km/s layer, which is probably composed of the Messinian evaporites. Overlying the evaporitic layer are layers composed of Plio–Pleistocene sediments, whose velocity is 2.0 km/s. The refraction profiles and gravity and magnetic models indicate that a transition from a two layer continental to a single-layer oceanic crust takes place along the Levant margin. The transition in the structure along the southern profile is located beyond the continental margin and it is quite gradual. The northern profile, north of the Carmel structure, presents a different structure. The continental crust is much thinner there and the transition in the crustal structure is more rapid. The crustal thinning begins under western Galilee and terminates at the continental slope. The results of the present study indicate that the Levant Basin is composed of distinct crustal units and that the Levant continental margin is divided into at least two provinces of different crustal structure.

Thermal Properties of Rocks and Density of Fluids

This Chapter describes the most important thermal parameters such as conductivity, capacity, duffusivity and interrelation of these parameters between themselves. Effect of thermal anisotropy in some cases may significantly change the studied geothermal pattern. Investigation of melting points of rocks and minerals, and temperature and pressure influence to thermal properties of rocks and minerals and fluid density play an important role in development of deep geothermal models. It is shown that analysis of the early Earth atmosphere is significant for detecting some peculiarities of the modern geothermal regime of the Earth.

Transport infrastructure surveillance and monitoring by electromagnetic sensing: the ISTIMES project

The ISTIMES project, funded by the European Commission in the frame of a joint Call “ICT and Security” of the Seventh Framework Programme, is presented and preliminary research results are discussed. The main objective of the ISTIMES project is to design, assess and promote an Information and Communication Technologies (ICT)-based system, exploiting distributed and local sensors, for non-destructive electromagnetic monitoring of critical transport infrastructures. The integration of electromagnetic technologies with new ICT information and telecommunications systems enables remotely controlled monitoring and surveillance and real time data imaging of the critical transport infrastructures. The project exploits different non-invasive imaging technologies based on electromagnetic sensing (optic fiber sensors, Synthetic Aperture Radar satellite platform based, hyperspectral spectroscopy, Infrared thermography, Ground Penetrating Radar-, low-frequency geophysical techniques, Ground based systems for displacement monitoring). In this paper, we show the preliminary results arising from the GPR and infrared thermographic measurements carried out on the Musmeci bridge in Potenza, located in a highly seismic area of the Apennine chain (Southern Italy) and representing one of the test beds of the project.

Structure of the Sea of Galilee and Kinarot Valley derived from combined geological- geophysical analysis

The Sea of Galilee (Lake Kinneret) is located in northern Israel in an area of complex tectonic setting where the Dead Sea Fault (DSF) (Figure 1) crosscuts other fault systems. This transform is more than 1000 km long, and is a plate boundary separating the Sinai and Arabian plates (Garfunkel et al., 1981). This lake is located with a larger Kinneret - Bet Shean basin which is a part of a series of rhomb-shaped grabens (pull apart basins) along the DSF (Freund et al., 1970). The lake is the main source of fresh water in Israel with an average surface of 166 km2 and an average volume of 4·109m3. Maximal depths of the lake (about 50 m) are located in the NE part of the basin (Figure 1C). The present configuration of Lake Kinneret was formed about 24,000 years ago (Hazan et al.,, 2005). Geological studies indicate that rock outcrops in this area and rock samples discovered in wells surrounding the lake range from Jurassic to Quaternary.

Determination of formation temperature from bottom-hole temperature logs—a generalized Horner method

A new technique has been developed for the determination of the formation temperature from bottom-hole temperature logs. The adjusted circulation time concept, and a semi-analytical equation for the dimensionless temperature at the wall of an infinite long cylindrical source with a constant heat flow rate, is used to obtain the working formula. It is shown that the transient shut-in temperature is a function of the mud circulation and shut-in time, formation temperature, thermal diffusivity of formations and well radius. The sensitivity of the predicted values of formation temperature to the thermal diffusivity is shown. Two examples of calculations are presented.

Near‐surface thermal prospecting: Review of processing and Interpretation

Temperature measurements at shallow depths (up to 3 m) contain useful information about features of the geological structures in the areas under investigation; however, the noise caused by seasonal temperature variations and terrain relief effects may significantly distort the observed temperature field. Therefore, procedures are developed for the calculation and removal of these noise sources: (a) seasonal variations are first eliminated by a procedure using repeated observations; (b) terrain relief corrections are calculated by a correlation technique, which facilitates the identification of anomalies associated with concealed geological features. Essential similarities between thermal and magnetic prospecting make it possible to apply to thermal prospecting modifications of the rapid methods of characteristic points and tangents developed for magnetic prospecting. These methods are applicable to conditions of inclined relief, arbitrary magnetization (polarization), and an unknown level of the normal field. The methods can be used to locate disturbing bodies by their associated temperature anomalies. Interpretation is made possible by approximating bodies by a dipping thin sheet or a horizontal circular cylinder. The interpretation results obtained both on models and polymetallic (Greater Caucasus) and oil and gas (Middle Kura Depression) deposits testify to the accuracy and reliability of these methods. These methods were also used successfully for interpretation of temperature anomaly over underground cavity in Cracov (Poland).

Estimation of geothermal gradients from single temperature log-field cases

A geothermal gradient is one of the most frequently used parameters in logging geophysics. However, the drilling process greatly disturbs the temperature of the formations around the wellbore. For this reason, in order to determine with the required accuracy the formation temperatures and geothermal gradients, a certain length of shut-in time is required. It was shown earlier (Kutasov 1968 Freiberger Forshungshefte C 238 55–61, 1987 Geothermics 16 467–72) that at least two transient temperature surveys are needed to determine the geothermal gradient with adequate accuracy. However, in many cases only one temperature log is conducted in a shut-in borehole. For these cases, we propose an approximate method for the estimation of the geothermal gradient. The utilization of this method is demonstrated on four field examples.

Estimation of the effect of thermal convection and casing on the temperature regime of boreholes: a review

In a vertical borehole, free heat convection arises when the temperature gradient equals or exceeds the so-called critical gradient. The critical temperature gradient is expressed through the critical Rayleigh number and depends on two parameters: (a) the ratio of formation (casings) to fluid (gas) conductivities (λf/λ) and (b) the convective parameter of the fluid. Both these parameters depend on the temperature (depth). An empirical equation for the critical Rayleigh number as a function of the ratio λf/λ is suggested. For the 0–100 °C range, empirical equations for convective parameters of water and air are proposed. The analysis of the published results of field investigations in deep boreholes and modelling shows that the temperature disturbances caused by thermal convection do not exceed 0.01–0.05 °C. Thus, in deep wells the temperature deviations due to thermal convection are usually within the accuracy of the temperature surveys. However, due to convection cells the geothermal gradient cannot be determined with sufficient accuracy for short well sections. In shallow boreholes the effect of thermal convection is more essential (up to 3–5 °C). To reduce the effect of convection on the temperature regime in shallow observational wells, it is necessary to reduce the diameter of the wellbores and use well fillers (fluids and gases) with low values of the convective parameters. The field observations and numerical calculations indicate that the distorting effect due to casing pipes is small and its influence is localized to the ends of the pipes, and this effect is independent of time.

Well temperature testing—an extension of Slider's method*

A new technique has been developed for determination of the formation thermal conductivity, skin factor and contact thermal resistance for boreholes where the temperature recovery process after drilling operations is not completed. Slider suggested a technique for analysing transient pressure tests when conditions are not constant. We extend Sliders method for transient temperature well tests. It assumes that the volumetric heat capacity of formations is known, and the instantaneous heaters wall temperature and time data are available for a cylindrical probe with a constant heat flow rate placed in a borehole. A semi-analytical equation is used to approximate the dimensionless wall temperature of the heater. A simulated example is presented to demonstrate the data processing procedure.

Application of piezoelectric and seismoelectrokinetic phenomena in exploration geophysics: Review of Russian and Israeli experiences

Systematic research of piezoelectric and seismoelectrokinetic phenomena in the context of exploration geophysics began in the former Soviet Union in the mid-1950s. These phenomena are manifested by electrical and electromagnetic (EM) processes that occur in rocks under the influence of elastic oscillations triggered by shots or mechanical impacts (hits). This paper presents a classification of piezoelectric and seismoelectrokinetic phenomena, which is based on the analysis of abundant theoretical, laboratory, and field data accumulated mainly by Soviet, Russian, and Israeli researchers. This classification divides the above phenomena into the following types: (1) the seismoelectrokinetic (electrokinetic) phenomenon E, which occurs in poly-phase media because of the mutual displacement of the solid and liquid phases; (2) the piezoelectric phenomenon, which occurs in rocks that contain piezoactive minerals; (3) the shot-triggered phenomenon, observed in rocks in the vicinity of a shotpoint or hit point; (4) the seismoelectric phenomenon I, manifested by the change of the electric current passing through rock; and (5) high-frequency impulse EM radiation, generated by massive base-metal bodies. This paper describes these five phenomena in detail — their nature, manifestation patterns, and registration techniques. Because the manifestation patterns of the phenomena differ in various types of rock, the phenomena can be used as a basis for geophysical exploration techniques. The piezoelectric method is an example of a successful application of piezoelectric and seismoelectrokinetic phenomena in exploration geophysics. This method was developed in the former Soviet Union, and it has been applied successfully in mineral exploration and research in Russia and, recently, in the West. The method uses a new geophysical parameter: piezoelectric activity of rocks, ores, and minerals. It enables direct exploration for pegmatite, apatite-nepheline, sphalerite, and ore-quartz deposits of gold, tin, tungsten, molybdenum, zinc, crystal, and other raw materials. This method also differentiates rocks such as bauxites and kimberlites from host rocks by their electrokinetic properties.