THE VSP STUDY OF VELOCITIES OF SHEAR AND COMPRESSIONAL WAVES IN THE HALOGEN-CARBONATE SECTION OF THE SIBERIAN PLATFORM

Under consideration are results of the multiwave VSP performed in two deep boreholes within the Yurubchen-Tokhomo zone (YTZ) on the Siberian Platform with the use of special equipment: universal vibration compl ex <<Vibrolokator>> and 3-component borehole probe of gyroscopic orien tation. The paper describes a technique of field observations, methods of processing, behavior of wave fields of directed and undirected sou rces of elastic waves. Special attention is given to the revealed spli tting of the shear wave into <<quick>> and <<slow>>, which is the cons equence of azimuthal anisotropy in the upper part of the section (in b orehole Yur-33). Analysis of polarization of shear waves is promising for predicting the direction of the predominant orientation of subvert ical fractures. It is shown that by means of simple processing of data of standard one-component VSP it is possible to receive additional in formation on velocities of propagation of shear waves. Conditions unde r which the shear waves are reliably traceable in z-component are eluc idated. The data on formational velocities of compressional and shear waves obtained in a total of six deep boreholes. With the velocity dat a statistically analyzed, an averaged velocity model for the YTZ has b een constructed.