Applicability Of Eudo-Rotation Technique For Land Vsp With Difference In Surface Conditions At The Source Locations In Anisotropy Study

Pseudo-rotation technique may be applied in marine VSP study of azìmuthal anisotropy of horizontally layered<br>media. lt uses multicomponent downhole registration of downgoing converted PS-waves from two symmetrical<br>sources with small offsets because directed sources of S-waves can not be used on sea. Land symmetrícal<br>sources are more widely used than directed sources, so we would like to estimate efficiency of this technique<br>for land VSP. The land survey conditions involve variations of near-surface properties and altitudes, which<br>cause the travel times of identical waves to differ. The technique of equalization of these travel times before the<br>pseudo-rotation was suggested. lt was tested on synthetical data of full wavefield. The model used was based<br>on the VSP surveys in the Yurubchen-Tokhomo oilfield zone in Eastern Siberia.