Elimination of wrong results at study of near-borehole space by offset VSP

At interlinking of surface seismics with offset VSP (OVSP) cross-sections it is supposed, that the latter sections are more authoritative. However at considerable offsets of the shot point, the danger of obtaining wrong results grows because of fast alteration of the angles of incidence of waves on reflecting boundaries and alteration of wave form of reflected wave associated with it. It is shown, that wave field modeling with taking into account dynamics before acquisition and at the interpretation stage enables to eliminate such mistakes. As an alternative way, application at the same time with OVSP of another VSP modification method – moving source VSP (MS VSP) – is considered, that is less incured to danger of obtaining of absurd results when apriori information about the model of the medium is absent. Advantages of the MS VSP are illustrated by calculations on mathematical models.