Regional Porosity Estimation in Danish North Sea Chalk

When performing seismic inversion over a large area we often face lateral changes in the seismic signature not related to the geology of the target. Therefore a methodology to equalize seismic data over large areas was developed. The methodology was used to prepare the data for absolute seismic acoustic inversion. The P-wave impedance result was subsequently transformed into porosity via a relationship from well data. The methodology builds on the ability to assess differences in data using an un-biased wavelet and well tie estimation method. The method is utilized to correct for data issues without removing geologic information. We did this by constructing a matching filter from a wavelet parametrization that varied with depth. The methodology was successfully applied for regional porosity estimation over an area of 6400 km2, or more than 40 million seismic traces, in the Danish North Sea. The regional nature of the results is beneficial for the large scale geological understanding of the area especially for exploration purposes. Furthermore, it provides insights into relations between porosity and geomorphology, and helps identifying new exploration opportunities.