A22 TIME LAPSE SEISMIC ANALYSIS USING LONG OFFSET PS DATA Abstract 1 A new time lapse seismic analysis method that exploits the high angle properties of PS reflected data is proposed. Many hydrocarbon fields are characterized by a significant increase in shear wave velocity at the top reservoir interface. If this increase is followed by a slight increase in P-wave velocity a well defined peak will occur for the PS reflection coefficient at high incidence angles. If the P-wave velocity within the reservoir layer changes due to production this will lead to a shift (with angle or offset) of this