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stratigraphic control of reflexes

a stratigraphic control of reflexes was carried out with application of the traditional method of application basing on the comparative analysis of data VSP, LOG, a land seismics. The basic approach of an establishment of lithologic-and-stratigraphic confinedness of reflexes is the finding of position of a communal dot of hodographs of a straight line and back waves. The position of this dot characterised depth H and time to to, corresponds to the beginning of formation of a back wave. Definition of co-ordinates H, to to an index point is most precisely carried out after the deduction to a vertical (or a flattening) lines of correlation of back waves on the seismogram the basic reductants VSP – Z – a component.

R-component (far offset)

 

 

 

 

 

 

 

 

 

 

 

 

The greatest presentation of a stratigraphic control of reflexes, and also coordinations of data VSP, LOG, a land seismics and a geological section is reached at data of the enumerated materials on one plane-table - the composite schema. Such schema compounded under again received data , is introduced on fig. 4.6, 4.7. On this schema there is no the uppermost part of a cut-away (above Lulinvor suites, ~ 200m); the reason of an exception of this part is the high extent of a contamination of a seismogram waves – clutters. We will notice that data LOG, time section CMP on a profile through a hole, suites, and for some spacings layer breakdowns, are introduced by the Customer in full. The analysis of the materials deduced on the composite schema in aggregate with high-speed model of a cut-away and taking into account some features of a wave seismic field allows to make the following concludings.
On the introduced schema as on seismogram Z – a component with the straightened lines of correlation, and on a piece of time section CMP, it is possible to see a high extent of a saturation reflexes in the range of times 0,2-1,3s (a depth interval 200-1450m), in the stratum relation encompassing depositions from tops Gankinsk to bottoms Pokursk suites. This saturation is caused multi-layer alternating lithological (arenaceous and argillaceous) the differentials, an a consequence high extent of high-speed differentiation. Last is pointed out not only large number of longitudinal back waves, but also and an abundance of incidenting alternating waves (fig. 4.3, 4.10) which one generation is promoted by frequent differences of velocities of transverse waves. From the stated follows that the cut-away of an esteemed spacing laies out the favorable preconditions for its detailed partition and (if necessary) conductings layer time references of reflexes (within the limits of resolution of the instrument of seismic survey).
Reflexes are referred to the held most out and traditionally traced in this spacing with a communal subscipt IV. Among them the properties, marking characterise reflexes IVG and  IVB1, dated for boundaries in depositions Gankinsk and Ipatov suites (fig. 4.6). Both reflexes are introduced by multiphase oscillatings with some differentiation of phases on peak expressiveness. Phases with the greatest amplitude, dedicated on seismogram VSP and traced on time section CMP are registered on times to to 0,390s and 0,650s accordingly.

Reflexes IV are referred to group of reflexes with a subscipt IV on the generalised schema of a stratigraphic control of reflexes of the Tomsk region [1] IV] (boundary in top parts of Ipatov suites) and IVB (a bottom of Kuznetsov suites).

Composite table

 

 

 

 

 

 

 

 

 

 

 

 

Cmposit-stratigraphy

 

 

 

 

 

 

 

 

 

 

 

 

Reflexes in the range from a base surface Kuznetsov to a bottom a part Pokursk suites have no regular nature and co-ordinate with unstable on track boundaries of layers of sandy and argillaceous differentials.
It is regional traced and falling into marking reflex with a subscipt III on seismogram VSP it is introduced by twophase oscillating with high peak expressiveness of both phases. Reflex is unequivocally identified with boundaries of pays marine clay, developed in a bottom part Pokursk suites. A decay interval of the maiden phase of reflex III – 1,300s.
Reflex IIa – is regional steadily traced on territory of the Tomsk region unequivocally is stratified with a base surface Bazhen suites upper Jura. Its forming originates on boundary of shift of bituminous mudstones Bazhen suites sand depositions top-Vasugan suite. According to modelling this boundary brings the basic contribution to reflex energetics. On seismogram VSP reflex IIa  is introduced with indistinctly expressed staging oscillating in which one only one phase possesses peak expressiveness of the average level with decay in profile top (fig. 4.6, 4.7). The Decay interval of reflex IIa – 1,900s.
After reflex IIa, in the range of times 1,935-1,985s three intensive lines of correlation are registered, maiden two of which one we identify with bench coals, third - with a surface below Jura the bases. The abbreviated thickness of deposit of the Tyumen suite has caused a close layout of acoustic discontinuities at the expense of what reflexes generated by them are fixed in the form of uniform three-phase oscillating.
Reflex F2 which is registered as soon as that has been noted, in difficult three-phase oscillating, is introduced by a line of correlation with unstable peak expressiveness; essentially sharp dip of amplitude is observed in a depth interval 400-700m (fig. 4.6). Decay interval F2 – 2.000s.

After this reflex (approximately on 0.035s) it is fixed was gentle expressed on amplitude on seismogram VSP, but very powerful on time sections CMP and VSP (partition 4.4 see) reflex F1 as which one presumptively we consider dated for a base surface of a zone of desintegration of formations of a near-surface part of the Paleozoic foundation. A little enhanced peak expressiveness of reflex F1 can be observed in the most original path of propagation (fig. 4.7).

"The velocity configuration performance"