The FRISK project focus on the risk related to faults in reservoirs under consideration for CO2 storage. The project has had good progress on developing new knowledge about faults and implement the knowledge into fault modelling tools relevant for addressing fault properties and risk assessment. In the current work we have identified three main factors important for fault seal behaviour: (1) fault geometry and complexity, (2) fault flow properties and (3) reservoir dynamics and pressure changes. We have developed new tools to calculate how much CO2 that can leak out trough a fault and we demonstrate the uncertainties for these types of models. The new models are tested for the Vette Fault Zone in the Smeaheia Fault block in the Horda platform area. Our work show that very small volumes of fluid can migrate along the fault and up in the overburden towards the seafloor. This is due to this part of the fault being very thin and the sedimentary layers in the overburden have a high clay content providing good sealing. The work has been shared in several meetings and conferences and well received by industry and academic groups. We see potential for implementation of methods in relevant industrial workflows for CO2 seal integrity evaluations.
The project outcome is an improved fault derisking workflow that includes an evaluation along-fault fluid migration. We have identified uncertainties in the fault zone interpretation methodologies and new models for fault zone complexities related to the fault growth history has been described and proposed as an important controlling factor for fault zone sealing capacity. Tools for estimating fault zone permeability has been developed and integration with reservoir simulation tools has been demonstrated for singe and two-phase flow. The work has contributed to improved knowledge of the fault seal properties in the North Sea, specifically the Vette Fault Zone in the Horda Platform. The new data and tools are useful for the qualification of faulted traps for CO2 storage. However, it still remains to be seen if such reservoir will be qualified as storage sites.
Prediction of fault seal integrity has been identified as a major technology gap and obstacle for qualification of CO2 storage within faulted reservoirs with structural traps. Existing workflows and methods have limitations when it comes to including along-fault flow and dynamic changes related to increasing reservoir pressure during injection. The FRISK proposal has the ambitions to improve the fundamental understanding of fluid flow in faults and contribute to a better framework for fault derisking with application for CO2 site qualification. The proposed research activities is focused towards the Smeahia case study and includes: (1) mapping and quantification of fault complexity as a base for 3D risking of faults, (2) constrain static and dynamic fault flow properties from experimental data and field observations, (3) develop effective along-fault flow models and (4) quantify uncertainty in key controlling parameters and leakage rates. The main findings will be integrated and synthesised to quantify the fault related leakage-risk and outline how the new findings may contribute to the structural derisking for Smeaheia. Reduced uncertainty in fault related leakage risk may enable qualification of potential geological CO2 storage sites in the North Sea. Hence, the FRISK project answers directly to the priority area of the CLIMIT call on Large-scale storage of CO2 on the Norwegian shelf in the North Sea.