Boris Khesin

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).

Investigation of geophysical fields in pyrite deposits under mountainous conditions

Abstract Geophysical surveys under mountainous conditions are generally complicated by various noises, primarily by rugged topography effects. A rational integration of mobile geophysical methods (gravity prospecting, magnetic prospecting and VLF technique has been substantiated and effective methods of interpretation have been developed for copper pyrite deposits of a Kuroko type (an important source of non-ferrous and noble metals) not infrequently occurring in mountainous regions. A special scheme for obtaining the Bouguer anomalies has been employed to suppress the terrain relief effects dampening the anomaly effects from the objects of prospecting. The scheme is based on calculating the difference between the free-air anomaly ( Δ g F.a ) and the field determined from a 3-D model of a uniform medium with a real topography. This scheme almost doubled the accuracy of the Δ g B chart. The further interpretation includes the following basic steps: (1) singling out the object of search using summation of the amounts of information obtained in various fields; (2) revision of the geological section using the methods specially devised for quantitative interpretation of anomalies under conditions of a rugged topography, inclined polarization and an unknown level of the normal field; and (3) physical-geological simulation realized as man-computer selection with the use of an effective algorithm for solving a direct 3-D problem of gravity and magnetic prospecting under the conditions of complex mediums and rugged observation surfaces. The method has been successfully tested at various stages of geophysical investigation under a variety of geological conditions, including saturated prospecting on the Kuroko-type Kyzylbulakh deposit (Lesser Caucasus) which has been thoroughly investigated by mining and drilling operations.

Rapid methods for interpretation of induced polarization anomalies

Abstract The induced polarization (IP) method is used at various stages of prospecting in poorly accessible regions that have complex structure. For such conditions we suggest approximate procedures for acquiring information about the location of the structures in question. Correlation between the observed fields and the heights of observation points is used for reducing the effect of terrain relief. Simultaneously, the problem of revealing an anomalous body is qualitatively solved. The qualitative construction of pseudosections of apparent polarizability η a and semi-quantitative determination of the depth of a polarized bed using vertical sounding allow us to obtain information about the ore potential of a region as a whole and the location of ore deposits specifically. We demonstrate common aspects of typical models (thin and thick beds, horizontal circular cylinder) with models used in magnetic prospecting. On this basis it is suggested that one should apply quantitative methods of magnetic anomaly interpretation in the cases of rugged topography, oblique magnetization (polarization) and unknown levels of the normal field for rapid inversion of η a anomalies. These rapid methods (improved modifications of characteristic point and tangent methods) are successfully tested both on models and in actual prospecting and investigation of a karst terrain.

Geophysical evidence of deep hydrocarbon flow in Mottled Zone areas, Dead Sea Transform zone

The origin of unusual magnetic initially sedimentary rocks of the Mottled Zone (MZ) in Israel and Jordan remained enigmatic for several decades until integrated characterization of the MZ area was achieved by ground magnetic measurements and geologic observations along representative profiles in parallel with reprocessing and reinterpretation of available aeromagnetic and gravity data. Micromagnetic profiling was combined with gamma-radioactivity measurements, and representative samples were selected to determine rock physical properties. Results of field measurements, reduction and transformation of geophysical fields, anomaly inversion, and forward modeling accompanied by geologic analysis suggest that two types of magnetic anomalies and local gravity minima in the MZ areas are related to the same event, i.e., deep hydrocarbon flow associated with fossil mud volcanism. Physicochemical interaction of deep hydrocarbon flow and surrounding sedimentary rocks caused widespread weak magnetization and correspo...

Methodological Specificities of Geophysical Studies in the Complex Environments of the Caucasus

Geophysical studies of the Caucasus need to cope with the mountainous environments of many of its regions and their inclined (oblique) magnetization in temperate latitudes. The uneven topography not only impedes geophysical surveys in mountainous areas due to poor accessibility, but also distorts the measurement results.

Common Aspects of Geophysical Fields in Question

As mentioned above, magnetic prospecting is the best investigated method to be applied under mountainous conditions [146]. Alexeyev [5] has developed rapid methods for quantitative interpretation of anomalies observed under the conditions of oblique magnetization, rugged relief and unknown level of the normal field. Therefore, the possibility of adapting the techniques involved for other geophysical investigations and the analysis of the similarity of analytical expressions for the arising anomalies are note worthy. The comparative study of analytical expressions for some geophysical fields has been carried out earlier in [18,205].

Geophysics in Hydrology

The Transcaucasian and areas of the Greater Caucasus within the territories of Azerbaijan and Georgia alone incorporate more than 53,000 rivers, lakes, water reservoirs, glaciers and swamps with total water reserves of 168 km3 (Svanidze and Tzomaya 1988). It is obvious that the total Caucasian water reserves consist of much larger volumes.

Investigation of Seismic Activity

The Caucasus is one of the most active segments of the Alpine-Himalayan seismic belt (Khain 2000). The Caucasian region is characterized by intensive deformation and seismicity that accommodates the continental shortening between the Eurasian and Arabian plates, which are converging at a rate of about 30 mm/year (De Mets et al. 1990; Jackson 1992). The Caucasus is considered a key area for seismic hazard assessment for the following main reasons (Balassanian et al. 1999): (1) the active tectonics and seismicity rate of the whole area, (2) availability of abundant multi-disciplinary data and a long established tradition of hazard assessment, (3) the unique opportunity to test different methodologies in one test area.

Environmental and Near-Surface Geophysics

Mud volcanoes are widespread in the world both on land and in marine basins, in collision and transtensional settings (e.g., Kholodov 2002; Limonov 2004). Their presence is often an indicator of deep-seated hydrocarbon accumulations. At the same time, mud volcanism represents great environmental hazard that must be taken into account in the design of oil-and-gas pipelines and other constructions. The main conditions for mud volcano formation are a thick sedimentary cover (several kilometers) and plastic clayey members with an anomalously high formation of pore pressure and the presence of thermal water (Pilchin 1985; Limonov 2004). Nowadays, more than 900 terrestrial and 800 offshore mud volcanoes are known or presumed to exist (Dimitrov 2002). More than a quarter of all the known mud volcanoes are concentrated within the Caucasus (e.g., Kadirov et al. 2005) and most (more than 220) (Kholodov 2002) are located within the “Abikh triangle” (Abikh 1863) near Baku (Fig. 8.1). Mud volcanoes are always confined to longitudinal faults or to the intersection nodes of longitudinal and transverse faults (Pilchin 1985). In general, pre-existing deep faults are the main controlling factors. Many mud volcanoes exist in the Black Sea and Taman Peninsula (northwestern Caucasus) as well as mid valley in the Yori River near the Georgia-Azerbaijan border (Fig. 8.1).

Tectonical-Geophysical Setting of the Caucasus

Many outstanding geologists such as G. V. Abikh, I. M. Gubkin, V. E. Khain, K. N. Paffenholtz studied the Caucasus. The Caucasus comprises four main morphological and tectonic units (Khain and Koronovsky 1997): (1) the Ciscaucasian plain (Scythian platform), including the foredeeps of the Greater Caucasus; (2) the Greater Caucasus itself, stretching in a WNW-ESE direction; (3) the Transcaucasian system of intermontane basins, and (4) the Lesser Caucasus with its an arcuate N-convex shape and the most heterogeneous structure. This geological division of the Caucasus is traditional, although it is sometimes modified (Fig. 2.1).