Anisotropic Pre-stack Overburden R-Factor Measurement from Field Data

In response to the pressure change in the reservoir, the rocks are expected to compact/dilate to recover the balance in the stress state. This deformation further manifests itself as detectable time-shifts. The semi-empirical R-factor rock physics model links the Geomechanics (strain changes) and seismic time-shifts. This simple and linear model, coupled by the mentioned post-stack workflow has been the common standard for Geomechanical seismic history matching. However, this model ignores the lateral strain changes, and assumes the time-lapse changes are isotropic. In this study both shortcomings are addressed by incorporating anisotropy and strain-dependency into the 4D velocity change model. Pre-stack time-shift modelling and application a North Sea data showed that the proposed workflow provides the possibility to compare modelled and observed angle-dependent time-shifts to capture the true physics underlying the time-lapse changes.