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Reflected waves breakdown on planes of propagation in three dimensional space


Abstract

The paper underlines that in areas of complicated relief featured by complex deep seismic geological conditions, the geological efficiency of 2D seismic survey is low and this is due to the multidirectional property of reflection planes in space. In areas with a wide development of narrow anticlines and bowl-shaped synclines with steep flanks while shooting of linear 2D seismic lines a large number of waves propagating in inclined plane of the section are observed, that is, the so-called lateral waves, many of which are waves single-reflected from bedding surfaces. Evidently, if the elements of occurrence of reflective surfaces are unequally oriented in space (i.e. they have different azimuths of uprising), then the lateral waves will propagate in different inclined planes and arrive to the line from different sides. It is underlined that without 3D seismic data and knowledge on existence of lateral waves, a geophysicist compiling a seismic section along a linear 2D seismic line in a usual way gets a composite “section”, which is a set of reflecting horizons corresponding mainly to lateral waves (propagating in different planes), which essentially is not a section as it does not reflect the structure of the studied area in any one plane. Such a section is characterized by a very complex interference wave pattern with a chaotic arrangement of the wave in-phase axes. This is precisely the nature of the complicacy, chaos and ambiguity of most seismic sections derived by seismic exploration in areas with complicated geology in Azerbaijan. The theoretical bases and methodology for breakdown of reflected waves along propagation planes, as well as a technique for constructing of vertical and inclined sections dissecting the studied complex geological environment on various planes at different angles to the vertical plane, have been developed. Equations establishing relation between the elements of occurrence of a flat reflecting element and the quantities that determine the spatial position of wave propagation plane have been derived. Two-staged methodology is displayed for constructing of vertical and inclined seismic sections: at the first stage, we define positions of inclined planes at which the reflected waves arrived to the selected observation line, at the second stage the waves are grouped by propagation planes and both inclined and vertical sections are constructed.

Keywords

upper cretaceous, maykop, seismic survey 2D and 3D, propagation planes, seismic planes, reflected waves, vertical and inclined sections

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