A brief interpretation

Comparison of the top semblance analysis to the bottom semblance analysis in Figure demonstrates the potential for high-resolution migration velocity analyses in reservoir applications. The gas reservoir is located at about 2.25 s pseudo-depth in the near offset section of Figure . The change in amplitude along the gas event from the surface location at 4.0 km to 4.7 km (700 m separation), from bright (gas?) to dim (no gas?), may be indicative of change in reservoir sand porosity and/or pore gas saturation. The velocity analyses in Figure imply a clear change in kinematic hyperbolic moveout spatially along the reservoir, since the migration velocity at reservoir depth is about 1950 m/s at 4.0 km (gas?) and 2050 m/s at 4.7 km (no gas?). This change of 100 m/s in migration velocity implies a much larger change in interval velocity along the reservoir, on the order of 500 m/s, which is consistent with sandstone compressional velocities under dry versus saturated conditions (Lumley et al., 1992). Of course, any responsible interpretation of such velocity analysis results should include correlation with in situ borehole measurements.