Estimation Of Viscoelastic Paramenters From Zero-Offset Vsp Data

There exist different expressions for seismic attenuation. We want to compare some of these models by<br>doing parameter estimation on a zero-offset VSP dataset. The attenuation models are the Kolsky-Futterman<br>model (Kolsky. 1956; Futtctman, 1962), the standard linear solid model (Ben-Menahcm and Sin&. 198 I L<br>the power law (Strick. 1967), Azimi’s second and third law (Azimi et al., 196X), the Cole-Colt model (Colt<br>and Cole. 1941). Miiller’s (1981) model and Kjartansson’s (1979) model.<br>In the modeling scheme we have used the geometric ray approximation (Ursin and Arntsen. 1985). for<br>point-source. vertical wave propagation in a 1-D viscoclastic medium with plane wave reflection coefticients.<br>Amundsen and Mittet (1994) used the same modeling algorithm to invert for complex velocities in<br>a set of layers using zero-offset VSP-data. They did inversion with respect to each frequency component of<br>the complex velocity. Our approach is to assume a formula for the complex velocity and then invert for the<br>parameters in a few homogeneous layers. The inversion algorithm has been tested on a VSP-datasct from<br>a well in the North Sea for different attenuation models. By minimizing the error energy we estimate the<br>parameters in the different models.