Current Demands to Accuracy of Near-Surface Studies for Performing CDP Reflection Surveys

Steady toughening of demands to accuracy of seismic exploration results against amplitude contraction and reduction of prospect-target areas being brought into operation is a present-day tendency seen in West Siberia. A complex but rather urgent practical task of CDP reflection surveying is to identify low-amplitude small-sized and shallow-buried (at level of S-G horizons) targets which presence in a wave field of time sections is hidden by near-surface velocity inhomogeneities, i.e. when a near-surface factor is dominant or comparable to a structure factor. It is necessary to provide a proper accuracy of near-surface inhomogeneities corrections in the conditions typical for northern areas of West Siberia. To perform accurate correction for near-surface structures, it is necessary to apply special near-surface targets’ observation systems, for example: multi-level seismic technologies that envisage use of several receiving systems different in their specification parameters. A report gives a brief overview of the existing approaches to near-surface correction, as applied, mainly, to weathering and permafrost zones; draws attention to distortion effects of these inhomogeneities; formulates methodic conditions at which a seismic exploration method provides the accuracy needed.