The last years feature reduction in the volume of geophysical operations. For exploration of solid minerals, well logging and seismic exploration of oil and gas this trend has occurred since 1986, 1990 and 1991 respectively. To illustrate it the results of activities of the six largest geophysical enterprises of Roskomne-dra (Russian Federation Committee on Geology and Use of the Earth Interior) operating in West and East Siberia, northern Europe- an part of Russia and its central and Middle-Volga regions in 1990-1993 have been analyzed.......

A new model of the Earth’s isostasy. The shape of our planet (geoid) can be quite closely approximated by the figure of equilibrium of a rotating liquid of the same mass (spheroid) enclosed in separate shells. The spheroid or theoretical geoid is characterized by a small compression value, s = 1/298.25, depending on the angular velocity of rotation and the law of mass distribution inside the Earth [4]. At one time, when the shape of ourplanet was studied by geophysical methods, a theory of isostasy appeared. In that theory the equilibrium state of the Earth was replaced with that of its crust (and later on, lithosphere). It conformed to that epoch’s standard of knowledge about the Earth’s structure and agreed with the objectives of use of the concept. From our present-day knowledge about the Earth’s structure, the above substitution cannot be regarded as reasonable. To solve geotectonic problems, we had to introduce a new model for the equilibrium state of the Earth as a whole which we named as geoisostasy. Its most detailed description can be found in earlier published works [6,10]. Its main points may be reduced to the.following. Geoisostasy should correspond to the Earth’s state it would have if its substance within each shell became liquid without mixing. In such case, our planet could be characterized as a set of certain-level surfaces being a system of spheroids with ever-decreasing compression coefficients formed by the entire Earth’s masses including its hydrosphere and atmosphere. Practically, the spheroid closest to geoid is the most significant.......

In June-October 1991, Schlum-berger Wireline Services provided well logging in the Tengiz field for formation and cement bond evaluation. Russian logs were also run in the same wells (most of the tools manufactured by NIIGI). The present paper gives a comparative analysis of the Russian and Western techniques used.......

The wave theory substantially refines the knowledge of the geometric seismics and suggests, in particular, that the reflection and diffraction mechanisms are the same, and the notion of the point source of secondary radiation has no real physical meaning. Diffraction, as well as reflection, the first being a limiting case of the latter, is formed by a finite-size surface. A point of a zero surface cannot radiate anything. Therefore, the imaging algorithm should not focus the waveform information of seismic records at discrete points of medium, as it is done now on the basis of the concepts of geometric seismics. On the contrary, it should distribute the waveform information along the surfaces producing the waveforms in the process of reflection/diffraction according to the wave approach. Implementing the above suggestion requires a quantitative evaluation of sizes of the surfaces forming the secondary radiation and contributions of individual points of these surfaces to the signal formed.......

Timely well seismic surveys can substantially increase the geologic and economic efficiency of geological exploration by improving the pattern of wells. The use of combined surface and well seismic exploration provides new approaches to organizing the geological exploration process due to an opportunity for reliable field evaluation during a shorter exploration period.......