Time-lapse seismic amplitude versus offset responses with change of saturation and pressure in unconsolidated sandstone reservoir with high porosity

Key words:  : unconsolidated sandstone reservoir with high porosity  effective pressure  saturation  time-lapse seismic  amplitude versus offset  petrophysical parameter

Abstract:

The calculation method of primary wave and second wave speed were studied when the oil saturation and effective pressure of unconsolidated sandstone reservoir with high porosity in X Oilfield changed. And the calculated results were compared with the corresponding, real log data. The calculation of petrophysical parameters and the forward modeling of time-lapse seismic amplitude versus offset (AVO) indicate that oil saturation change gives more obvious effects to primary wave speed and P-P wave reflection coefficient than to second wave speed and P-S converted wave reflection coefficient. However, the effects of effective pressure on speed of primary wave and second wave are under a similar dfegree, and the AVO curves of upper interface have obvious responses with smaller incidence angle (0<20°) to P-P wave and with medium incidence angle (30°士0<50。)to P-S converted wave. Synthetic time-lapse seismic response analysis is a usefui tool in X Oilfield for studying the feasibility of time-lapse seismic, defining the borders of reservoirs, determining the change of oil saturation and effective pressure and realizing the quantitative interpretation of time-lapse seismic data.