Quantification of fault-related leakage risk

FRISK prosjektet setter søkelys på risikoen relater til forkastninger i reservoarer som skal kvalifiseres for lagring av CO2. Prosjektet har hatt god progresjon i arbeidet med å ta i bruk ny kunnskap om væskestrømning i forkastninger og bygge modeller som kan brukes for vurdering av forkastningsforsegling og risiko. Gjennom arbeidet har 3 viktige aspekter blitt vurdert: (1) forkastningsgeometri og usikkerheter, (2) strømningsegenskaper til forkastninger og (3) dynamiske trykk endringer i reservoaret. Vi har utviklet nye verktøy for å kunne beregne hvor mye CO2 som kan lekke ut gjennom en forkastning og vi belyser usikkerhetene i denne typen modeller. De nye modellene er testet for Vette forkastingen i Smeaheia på Hordaplatformen. Arbeidet viser at det er veldig små volumer av væske som kan strømme langs Vette forkastningen og opp gjennom de overliggende sedimentære lagene mot havbunnen. Dette skyldes at forkastningen er en veldig tynn sone i dette området og at lagene inneholder mye leire som gir en tett forkastning. Arbeidet er delt i flere møter og konferanser og møtt med stor interesse ho både industri og forskningsmiljø. Vi ser potensiale for å jobbe videre med å ta i bruk metoden og utvikle relevante verktøy for bruk i industrien.

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.