Triassic play analysis in the northern Dutch offshore

Abstract

The Triassic play has been overlooked in the northern Dutch offshore. As the reservoirs thin towards the north and prospect volumes are therefore relatively low, future discoveries are likely to be uneconomical for standalone development. A dedicated Play Based Exploration (PBE) approach enables shared risks between prospects to be quantified and used to raise the attractiveness of a prospect portfolio. Four Common Risk Segment (CRS) maps are created in this study for (1) reservoir presence, (2) reservoir effectiveness, (3) seal and (4) charge. These CRS maps are stacked and multiplied to create a Composite CRS map which shows the variability of the overall geological probability of success (POS) of the study area. In the CRS maps, areas are risked using a split risking method to separate shared risks and non-shared risks. The CRS maps are of good quality and confidence and when stacked, they give insight in where the promising areas within the study area are located, based on current knowledge. The F08 and F09 blocks in the Central Graben have the highest POS of the play, followed by the Step Graben in the E03, F01 and B16 blocks. The shared risk of the composite CRS map shows where a successful well can have a significant impact on the risk of specific areas. These areas are located in the north of the Step Graben and Central Graben and in the E09 and E12 Blocks. The CRS maps are used to risk 48 leads in the study area. The leads are evaluated on their shared risks and value of information and are compared to the current lead risking available in the EBN database. The POS defined by the location of leads on the CRS maps, are generally lower than the available risking in the EBN database, however, they cannot be compared effectively due to the lack of prospect specific and local risks in the CRS maps. The dependency analysis shows which leads in which areas can have impact on the portfolio when successfully drilled. Optimization of the prospect portfolio, including a prospect specific risking and the termination of uneconomical leads can improve the dependency analysis and result in a more attractive portfolio.