Geological Investigation of the Polaris CO₂ Storage Prospect in the Barents Sea

Abstract

This thesis investigates the Polaris prospect in the southwestern Barents Sea as a potential site for geological CO₂ storage. The study’s objectives were to (1) map the storage complex, (2) assess reservoir and seal suitability, (3) estimate storage capacity, and (4) evaluate leakage potential through the regional fault system. To achieve this, 3D seismic data were interpreted in Petrel alongside well‐log information from well 7125/1‐1. Results show that the Stø Formation comprises a homogeneous Jurassic sandstone interval with thicknesses between 52 and 120 m, average porosity of ~20 %, and permeability around 500 mD. Strong lateral connectivity is only interrupted by minor faults, indicating excellent reservoir quality. The overlying Hekkingen Formation consists of 50–85 m of laterally continuous, fine‐grained, organic‐rich shale with very low permeability, providing an effective cap rock. Structural mapping reveals a coherent, fault‐sealed trap: the Nysleppen Fault Complex (NFC) bounds the southern and southeastern margins, while stratigraphic continuity elsewhere maintains closure. The estimated capacity is 113 Mt CO₂, equivalent to roughly 11 years of Norway’s road traffic emissions, making the prospect suitable multi-decadal injection. Fault throws within the reservoir interval remain small, with no major leakage pathways observed. Although deeper NFC faults exhibit evidence of past fluid migration, they are interpreted as currently sealing; nevertheless, high‐pressure injection scenarios warrant ongoing monitoring. Further appraisal drilling, advanced seismic analyses, and reservoir monitoring should be undertaken to mitigate remaining uncertainties in fault integrity, heterogeneity, and pressure management.