Fault seal behaviour in Permian Rotliegend reservoir sequences : case studies from the Dutch Southern North Sea

van Ojik, K. and Silvius, A. and Kremer, Y. and Shipton, Z. K. (2019) Fault seal behaviour in Permian Rotliegend reservoir sequences : case studies from the Dutch Southern North Sea. Geological Society Special Publications. ISSN 0305-8719 (In Press)

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Abstract

Permian Rotliegend reservoir rocks are generally characterised by high N/G ratios, and faults in such sand-dominated lithologies are typically not considered likely to seal. Nevertheless many examples of membrane sealing are present in Rotliegend gas fields in the Southern Permian Basin. This manuscript reviews examples of membrane sealing in the Dutch Rotliegend, it presents a dataset of petrophysical properties of Rotliegend fault rocks, and analyses two case studies using commonly used workflows. From the field studies it is concluded that observable small AFPDs are present and that these are likely pre-production AFPDs due to exploration-time scale trapping and retention of hydrocarbons. It is concluded SGR-based tools may predict AFPD for Upper Rotliegend lower N/G reservoir rocks with reasonable results. Nonetheless the core sample data sets show a much wider range of permeability and capillary entry pressure than predicted by the SGR transforms. This highlights the potential to modify existing workflows for application to faults in high N/G lithologies and the need for more data. Data sharing and collaboration between industry and academics is encouraged, so that in the long run workflows can be developed specifically for faults in high N/G lithologies.

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