Issues of the journals Геофизика 2012 y. issue 0

Topical issues of vibroseis observation and processing of results

(Belousov A.V. Zacharyev Yu.M. Pleshkevich A.L. Ryaboshapko S.M. )

The problems associated with the production and quality assessment of vibroseis operations are considered. In the first part of the article the nature of the noise obsen’ed on the correlograms is examined, and a conclusion of predominance of deterministic noise is made. The second part is devoted to the feasibility of using nonlinear reference signals. It is shown that the conversion of linear sweep in a non-linear one may be conducted by construction of a single-channel correction filter with insignificant errors, it is concluded that one needs to compare the spectra of the seismograms and the approximation error in order to make a decision on the feasibility of using nonlinear sweeps.......

  • 2012  № 0, pp. 10-17

Technology of azimuthal amplitude analysis data of Land 3-D seismic data in the search for fractured zones

(Gogonenkov G.N. Pleshkevich A.L. )

The azimuthal anisotropy of the reflection coefficients and the related amplitude effects are considered as an important sign of vertical rock fractures, which may be related to hydrocarbon accumulations. Developed method and technology of the seismic amplitudes azimuthal analysis for 3-D seismic land data or “azimuthal A VO-analysis” is a new tool designed to evaluate the azimuthal anisotropy of the refection coefficients. Seismic data processingfor this analysis is discussed, including amplitude preservation and special azimuthal 3-D seismic pre-stack migration. The inverse problem solution with such migration results allows to avoid seismic data decomposition to narrow azimuthal sectors and the associated negative effects. Some practical examples of the amplitudes azimuthal analysis are given. A precondition for successful application of the technique is a sufficient range of shots/geophones offsets - both in the inline and crossline directions. This imposes additional requirements to seismic data acquisition of cross-type survey. A perspective application of the method is a problem offractures detection in Bazhenov strata of West Siberia for Big-Salym type non-anticlinal fields.......

  • 2012  № 0, pp. 18-27

Reciprocity relation, the amplitude and energy of waves energy from point sources in an inhomogeneous isotropic medium

(Pleshkevich A.L. )

Although the reciprocity relation (theorem, principle) is a well-known and widely usedfact, its traditionalformulation refers to a narrow and non-divergence form of a scalar wave equation which is associated with specific constraints on the properties of an inhomogeneous medium. Reciprocity relation is provedfor a scalar wave equation with general and divergence form, which describes waves in arbitrary inhomogeneous isotropic medium. A zero-order asymptotic approximation is constructed for this equation, including a transport equation for squared ray amplitudes, with the equation’s right-hand side describing a point source, and asymptotic Green’s function for which a reciprocity relation is formulated. The asymptotic estimate of wave energy from an instantaneous point source of constant strength is done which depends on an inhomogeneous medium. In addition, we have estimated total energy of waves from a point source with no asymptotic approximation. Surprise is that the instantaneous point sources and the corresponding Green’s functions have infinitely large energy. This phenomenon can be eliminated by setting a nonzero finite duration and signal amplitude at point sources.......

  • 2012  № 0, pp. 38-48