Abstract: In the pre-stack elastic impedance inversion, since the shear wave time difference log data are frequently not gained, the rock Poisson ratio cannot be accurately calculated. For this reason, the compressional wave time difference, formation density, shale content, porosity, water saturation and a variety of rock matrix and fluid elastic parameters are sufficiently used to develop Xu-White model for fluid displacement and get the shear wave time difference. This method is used for calculation of shear wave time differences of Well PMNA-001 at M block, Well F18B-29 and Well F18B-116 at F block in MBTL area. The results show that compared with the actually measured shear wave timedifference for these wells, the errors are small, completely meeting the demands of elastic wave inversion and oil-gas prediction.

Key words: rock, Poisson ratio, shear wave time difference, compressional wave time difference, formation density