Prestack Time Lapse Inversion of Seismic Data from Heidrun Field, Norway

We present prestack inversion of time lapse data acquired over the Heidrun Field in Norway between 1986 and 2006. Common image point gathers after migration are inverted simultaneously to estimate the elastic parameters and the source wavelet. The inversion methodology directly estimates the perturbation in the elastic parameters due to 4D effects. In this paper we focus our attention on prestack analysis, particularly the gather conditioning prior to 4D prestack inversion. Examining the residual gathers and data misfit maps from the prestack inversion provides a diagnostic check on the quality of the prestack processing. In many instances the prestack inversion reinforces 4D interpretation of the previous post-stack inversion. In some instances the 4D prestack inversion resolves ambiguity in the interpretation.