Improved seismic inversion for mapping of among other things pre-chalk reservoirs

The reservoir characterisation is done in two different ways. One is performing the reservoir characterisations without using the seismic data; the other is integrating the seismic impedance. The first approach is a simulation of sandstone architecture on middle Jurassic in the Harald field while the second is mapping the porosity in the Callovian unit in the west Lulu part of the Harald field. By utilizing these quite different approaches in the description of the Harald field the influence of utilising the seismic data is clearly shown. The non-seismic description shows how it is possible to create realistic sandstone architectures but with a large diversity in the different realisations. When this type of method is applied, as in this case on a reservoir that does not have a good coverage with wells, it does not attempt to make a detailed description of porosity and permeability. The characterisation methods including the seismic data do allow for realisations that describe the diversity in porosity and permeability, with a diversity that is limited by the information from the seismic data. Furthermore, it is illustrated in the project how facies realisations can be done utilising the seismic impedance as soft constrain at the realisations. The present EFP-96 project is part of an ongoing research between GEUS and Ødegaard. The aim of the research is to investigate ways of combining seismic data and geostatistics for reservoir characterisation. As a predecessor to the present project the Dan field has been characterised with geostatistical methods including seismic data. On the Dan field the target was a chalk oil reservoir with many wells. In the present project the focus is one pre chalk reservoir where there is a need to predict ahead of most of the wells and where, furthermore, lithology and facies predictions are needed. The third part of this research activity is description on the Roar field, a chalk gas field. The first and third parts of these research activities include COWI with their reservoir simulation experience. The present project is just between GEUS and Ødegaard