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The analysis of features of a wave seismic field

The wave seismic field filed on a vertical profile is representative of area of operations. In the generalised form it can be characterised as a field of multiple types of waves and the oilpaintings linked to them of the interferential phenomena. On high, in the whole background of waves-hindrances, mainly, regular nature on records the following types of the beneficial waves bearing the indispensable information on features of a constitution by the uncovered hole of environment are distinctly enough dedicated:
- Forward incidenting longitudinal wave Station;
- Forward incidenting transverse wave SV;
- Reflected longitudinal waves Station;
- Reflected alternating waves PS.
Because modern seismic studies on oil and gas are almost completely grounded on use only longitudinal waves, logical are introduced conducting of the fullest analysis of the wave field filed on a Z-component , first of all, with near Shot1.;
Forward incidenting longitudinal wave P, which one time-depth curve is a ground of definition of high-speed arguments of environment (Vmean, Vlayer, Vintrval- mean, layerand interval velocities) is registered maiden on absolutely quiet background throughout almost all vertical profile that provides possibility of unequivocal correlation go-devil tracing of its primary arrivals observed in the form of accurate sharp frustratings downwards (fig. 4.1). The exception compounds a 230-metre spacing in the uppermost part of a profile where go-devil tracing of wave P is completely stopped at the expense of laying of a pipe wave.
The time-depth curve of wave P represents hollow-convex, towards the subsequent record, a line with monotonously smooth reduction of a gradient of time with depth from 0,050s in a spacing 350-550m to 0,033s in a bottom-hole part counting on 100m a vertical profile. Below depth 230m wave P is registered with the positivegoing apparent velocity continuously accruing with depth from 2000m/s to 3050m/s in pointed spacings of a time gradient.
On a recording format the forward longitudinal wave looks like a simple short impulse which one form with depth remains enough steady (fig. 4,2a) that can testify to safety of conditions of excitation.
From the analysis of a peak spectrum of this wave follows that the frequency range in which one its basic energy is distributed, is concluded in a range of 10-40 Hz;; in process of magnification of depth of observation dominating frequency in a wave spectrum (as it is possible to see it on fig. 4.2b) is offset in field of low frequencies.
The longitudinal is single-pass-reflected waves , which are the basic class of beneficial waves, are registered on the source summary seismogram Z-components (Shot1) against an essential contamination waves-hindrances of the different nature (see more low). The Most peak-expressive and steady on tracing in a depth interval – an index point – a base surface of the conductor are the reflexes linked to boundaries Jura and Lower Cretaceous (Pokursk suite) cut-away spacings (fig. 4.1). In the pointed spacings it is observed on one line of correlation, sharply dedicated concerning the next fulcrums, on the high peak expressiveness. Other reflexes from boundaries Jura (light-duty) and very powerful Cretaceous spacings are characterised by gentle intensity and traced, as a rule, only on a part of a vertical profile.

On the seismogram Z-components with removed Shot2 increase of peak level was gentle the reflexes expressed to this sign on records with Shot1 is marked as a whole 1

Z-component

 

 

 

 

 

 

 

 

 

 

 

Wave form

Forward incidenting transverse wave SV registred on horizontal X-, Y- reductants with near Shot1; its piece is snapped on a short piece of a profile from a base surface of the conductor (220m) to depth ~ 600m also on a Z-component. Its confident go-devil tracing is reached after a polarising record processing operations X-, Y- a reductant.
On the seismogram R-components the field of wave SV is distinctly dedicated on sharp shift of nature of record before its arrival: before arrival we see the record saturated with regular and irregular waves high-frequency, after arrival – low frequency composition (fig. 4.4). Apparently, with some fraction of convention the boundary between these two records can be taken over for a primary arrival of wave SV.
Actually wave SV introduces difficult oscillating with the visible period nearby 0.070s.
Phase hodograph of wave SV also as well as a hodograph of forward longitudinal wave P introduce smooth, but it is ready more an easy curve with monotonous decrease of a gradient of time with depth from 0,114 with in a spacing 500-700m to 0,055 with in a bottom-hole spacing on 100m a vertical profile.

Z-component - wave types

 

 

 

 

 

 

 

 

 

 

 

 

R-component

 

 

 

 

 

 

 

 

 

 

 

Exchange back waves of type PS are a regular component of the wave field fixed on records horizontal X-, Y- a reductant with removed Shot2. Specially it is possible to see expressive nature of PS-waves on polarised reductant R (fig. 4.5). On peak expressiveness in the field of this reductants dominate reflexes with index points on depths 1370m and 2450-2500m. Hill up on a profile appreciable decay of these waves is observed.
Waves-hindrances. As a part of the filed wave field of a wave-hindrance play an essential role. On the genesisis they are linked to factors of technical or geologic nature.
The basic technical clutter is the clutter caused by 'ring' of a casing, introduced on records with near Shot1 waves of irregular nature (fig. 4.1), and on records with Shot2- in the form of regular oscillatings with the visible period ~ 0,030s (fig. 4.3).
The second clutter of a technical genesisis is introduced by a hydrowave diffused in a column of mud with velocity of 1480m/s. This wave reshaped in to-jig a spacing, specially expressive nature has on records horizontal a reductant.
Clutters of the geologic nature are introduced by multiple waves among which one distinctly dominating role waves play companions of straight lines of longitudinal and cross waves.

Incidenting alternating waves are referred to other kinds of 'geologic' clutters, is most multiple the Z-components introduced on the seismogram with Shot1, and waves, auxiliary the basic a reductant.

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"A stratigraphic control of reflexes"