Transformacja prędkości składania na inne rodzaje prędkości sejsmicznych
Abstract
TRANSFORMATION OF COMPOSITION VELOCITIES INTO OTHER KINDS OF SEISMIC VELOCITIES
Summary
The paper deals with a problem of transformation of composition velocity Vs into other types of seismic velocities (mean square VRMS, mean Vśr and interval Vi ones). Automatic analyses of velocity used at present demand large spacing. As the latter gets larger, the accuracy of composition velocity Vs is greater but unfortunately, a divergence increases between the composition velocity Vs and mean square VRMS and mean Vśr velocities determined close to the generator.
Therefore, elimination of unfavorable influence of long spacing is important at preserved accuracy in determination of a composition velocity Vs. ensured by large spacing. In the paper the method that fulfills such demands is proposed. It is based upon modelling of the composition velocity Vs and the mean square velocity VRMS (or mean one Vśr) for an approximate model of geologic structure and for assumed schemes of seismic spacing used in the field.
Differences between these velocities for the analyzed reflecting horizons for the basis to define a correction of the composition velocity Vs received from real data recorded by such measurement schemes as accepted for modelling. A choice of a model body creates a significant item in the influence on effectiveness of the correction method. This problem was discussed in detail with a consideration of:
a) possible construction of a model body for an area with a poor geophysical recognition,
b) divergence of parameter values of model and real bodies, and their influence on stability of corrections with a detailed classification of various variants resulting from deviations of parameters of a theoretical model and of a real geologic body. In general the proposed method enables to eliminate a negative influence of a large measurement spacing and in the same time, to preserve benefits resulting from a use of such spacings.
Summary
The paper deals with a problem of transformation of composition velocity Vs into other types of seismic velocities (mean square VRMS, mean Vśr and interval Vi ones). Automatic analyses of velocity used at present demand large spacing. As the latter gets larger, the accuracy of composition velocity Vs is greater but unfortunately, a divergence increases between the composition velocity Vs and mean square VRMS and mean Vśr velocities determined close to the generator.
Therefore, elimination of unfavorable influence of long spacing is important at preserved accuracy in determination of a composition velocity Vs. ensured by large spacing. In the paper the method that fulfills such demands is proposed. It is based upon modelling of the composition velocity Vs and the mean square velocity VRMS (or mean one Vśr) for an approximate model of geologic structure and for assumed schemes of seismic spacing used in the field.
Differences between these velocities for the analyzed reflecting horizons for the basis to define a correction of the composition velocity Vs received from real data recorded by such measurement schemes as accepted for modelling. A choice of a model body creates a significant item in the influence on effectiveness of the correction method. This problem was discussed in detail with a consideration of:
a) possible construction of a model body for an area with a poor geophysical recognition,
b) divergence of parameter values of model and real bodies, and their influence on stability of corrections with a detailed classification of various variants resulting from deviations of parameters of a theoretical model and of a real geologic body. In general the proposed method enables to eliminate a negative influence of a large measurement spacing and in the same time, to preserve benefits resulting from a use of such spacings.