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The analysis of seismic response based on well interpolated data was done. Our results follow the AVO theory based on Shuey's relation, equation (9), for amplitude variations with offset.

The interpolated data obtained from the given well data follows a geological distribution characteristic of a depositional system. It is also possible to note that the interpolation result correlate very well with the original well information. These results correlate with the original data distribution.

Fluid substitution with Gassmann's equations brings changes in the velocity model; we observe that the P velocity decreases with changes in the fluid type and that the lowest velocity in the sand body selected for the study corresponds to the gas substitution (Figure 13). It was also noted that there was a contrary behavior for the S velocity, since the shear modulus remains the same in the fluid substitution receipe, the S velocity increment observed is due to the density decreasement after the fluid substitution.

A high frequency seismic modeling with different velocity models brought different seismic responses. These different responses were due only to differences in the rock fluids. These behaviors reinforce the fact that different fluid type in the rock yield differents seismic responses, especially in the amplitude behavior.

The fact that the highest amplitude was the one with gas saturated sand confirms the bright spot phenomena observed in real seismic data in the presence of gas. This observation is an important in real life productions in order to predict gas reservoirs in the subsurface with seismic data.

The velocity analysis corroborates the frequency dependence of the velocity, since it was possible to note that seismic velocities are smoother than well velocities, but both velocities follow the same tendency.

Seismic velocities are different to well velocities not only in the frequency content but also in the velocity values. This value difference is probably due to the different components of the velocity that both experiments measure.

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Next: Appendixes Up: Gratwick & Rosales: Velocity Previous: Velocity Analysis
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