Mechanisms initiating fluid migration at Snøhvit and Albatross fields, Barents Sea

Abstract

The southwestern Barents Sea, part of the epicontinental Barents Sea located between Norway and the Svalbard archipelago, hosts several mature petroleum systems. Large gas chimneys, leaking faults and seabed pockmarks are proof that hydrocarbon leakage has taken place previously in this part of the Barents Sea. Glacial erosion, being one of the major episodes of erosion and uplift, has probably caused fluid leakage out of proven hydrocarbon reservoirs and fluid migration along permeable carrier beds. We use 3D seismic data from the Snøhvit gas field to focus on the nature of the fluid transport systems and the origins and potential mechanisms for how fluids migrated from deep-seated reservoirs. Mapping of the trap of the reservoirs at Snøhvit has allowed us to determine potential spill point locations, coinciding with major gas chimneys and several faults that extend into shallow strata. We explain how uplift and erosion caused gas expansion in the reservoirs allowing the gas to reach below the spill point located at the gas–water contact level at the bottom of the closure. Fluids, such as hydrocarbons, may have escaped through these spills points, leading to the emplacement and development of the aforementioned gas chimneys. Similarly, migration of fluids may have taken place along faults, reactivated by glaciotectonic processes and connected with spill points at reservoir depth. Both gas chimneys and faults have allowed gas to migrate into and be trapped in shallow gas accumulations within the Torsk Formation and below the upper regional unconformity.