Annual Report 2000 - WIT

107
Porosity variation with Depth
|Rpp|
0.3
0.25
0.2
0.15
0.1
decreasing porosity
0.05
1.0 200 0
2.0 100
Depth [km]
3.00
AVO curves
0 5 10 15 20 25
Receiver number
Figure 10: AVO curves for every depth point on the left reflector. Decreasing amplitude
with depth correspondes to decreasing porosity. Near-offset slopes of the AVO
curves are governed by Poisson's ratio.
domain and vice versa. We present an application of the method to retain precise information
about amplitude variations with offset in the depth domain. By comparing the
resulting AVO curves with the analytical reflectivity calculated from Zoeppritz' equations
(Zoeppritz, 1919), we find that the method is capable of mapping fine-scaled
variations of target properties as, e.g., those caused by variations of hydraulic properties.
The high accuracy of the reflectivity curves obtained enables us to draw more
information than the classical 2 AVO parameters (intercept and gradient) even in the
depth domain. This proves to be especially advantageous in complex environments
involving e.g. steep dips and/or unconventional acquisition geometries. The method
can also be used to simulate 4D monitoring experiments to investigate the change of
AVO anomalies over time.