CSEM Pre-well Predictions in the Johan Castberg Area, Barents Sea

In the Johan Castberg area, several exploration wells have been drilled the last four years testing mainly eight different prospects. All the exploration wells have been discoveries, but in some wells the hydrocarbon phase was dominantly gas. At present gas is not commercial in this part of the Barents Sea. Prior to drilling the wells, available CSEM data were used to assess resistivity values and potential hydrocarbon saturation range in the prospects. The pre-well assessment was not straightforward. Each prospect contributed with slightly different challenges for choice of inversion strategy and CSEM interpretation. However, the well results show that the overall track record for CSEM hydrocarbon prediction in the area is good. Six out of eight prospects were given an uplift based on CSEM data. For two out of eight prospects, CSEM analysis was inconclusive, because the expected prospect resistivities were below CSEM detectability threshold. Thorough understanding of the CSEM methodology as well as integration with geology and seismic has been imperative to obtain CSEM results with sufficient level of detail. For Statoil the Johan Castberg area has represented a laboratory for CSEM technology development and applicability.