Modified Anisotropic Walton Model for Consolidated Siliciclastic Rocks: Case Study of Velocity Anisotropy Modelling in a Barents Sea Well

The anisotropic Walton model is proposed by Bandyopadhyay (2009), to model the stress-induced anisotropic seismic response of a rock. However, this model is only proposed for unconsolidated rocks, and has only been tested on laboratory data. This work extends the anisotropic Walton model using a test on a well in the Barents Sea. We demonstrate that this model gives a good velocity prediction for shallow unconsolidated rocks, but greatly underestimates the velocities for deeper consolidated rock. For the consolidated rock, we can adjust the velocities from the Walton model with compaction factors, in order to produce reasonable velocity and anisotropy predictions. The compaction factors are primarily dependent on depth, effective porosity, and clay volume, in decreasing order of importance. Facies dependent compaction factors can also be defined to allow us obtain values varying according to lithofacies distribution.