Gas hydrate systems in petroleum provinces of the SW-Barents Sea

• Our data provide evidence for the connection of deep-seated hydrocarbon and shallow gas hydrate reservoirs.
• Unique formation of Tilted BSR.
• The formation of the tilted BSR is due to the variation in fluid flux.
• Active fluid flow from deep hydrocarbon sources through chimney networks coincides well with the fault complexes.
• The upward migrating fluids are captured in the gas hydrate stability zone at relatively shallow subsurface.

3D seismic data of the SW-Barents Sea provided information about the existence of Structure II gas hydrates and shallow gas in marine sediments. Gas hydrates and shallow gas exist in the SW-Barents Sea in conjunction with deep-hydrocarbon reservoir leakage. Available conventional 3D seismic data show acoustic chimneys that extend to depths ∼1700 ms two-way travel time below the seafloor. The location of the chimneys coincides with structural boundaries and fault complexes cutting through mostly Jurassic and Triassic strata. Vertical fluid flow through these chimneys transports thermogenic gas to the gas hydrate stability zone, causing the formation of a bottom-simulating reflector (BSR). In addition, variations of fluid flux across deep-seated fault complexes cause changes in heat flow, which explains the shoaling of the BSR and the formation of a “tilted” BSR (TBSR) at the border between the Ringvassøya Fault complex and the Loppa High. The stability model using thermogenic gas composition (type I and II) shows gas hydrates are stable at ∼225 m–∼345 m depth, corresponding to variation in the geothermal gradient for upper BSR (28.7 °C/km and 37 °C/km) and lower BSR levels (23.4 °C/km and 28.3 °C/km). These lateral changes in the temperature gradient can be reconciled with changes in upward fluid flow rates of 1.8–2.2 mm yr−1. Such gas-hydrate and fluid flow systems on Arctic continental margins especially in shallow water depths are potential gas emitters due to their sensitivity to warming ocean temperatures.