Estimation of fault hydraulic properties on regional time and spatial scales using pre-production overpressure distribution

This paper presents preliminary results of the analysis and interpretation of the observed pre-production fluid overpressure distribution in Rotliegend sandstones in block L8 in the Dutch offshore. The general objective of this study is to develop workflows to improve the understanding of timescales of pressure dissipation in relation to regional to basin scale fault models, including fault sealing properties. For this case study we used Eclipse reservoir modeling. The model for the Permian Upper Rotliegend Group includes the numerous gas fields in the area. Based on the configuration of these gas fields in combination with the observed regional overpressure distribution the original fault model could be improved. By creating a ‘dynamically stable’ model, fault multipliers were determined which gave a pressure drop below 1 bar over a period of 5000 years. The resulting distribution of the fault multipliers over the model area clearly identified differences within the study area. A large part of the estimated fault sealing capacity could be explained by the geometry of the fault (offset and sand-sand juxtaposition). The simulations also showed that only a small area of sand-on-sand juxtaposition requires a reduced fault transmissibility in order to retain the observed overpressure for any length of time