Gas hydrate distribution and hydrocarbon maturation north of the Knipovich Ridge, western Svalbard margin

Abstract

A bottom‐simulating reflector (BSR) occurs west of Svalbard in water depths exceeding 600 m, indicating that gas hydrate occurrence in marine sediments is more widespread in this region than anywhere else on the eastern North Atlantic margin. Regional BSR mapping shows the presence of hydrate and free gas in several areas, with the largest area located north of the Knipovich Ridge, a slow spreading ridge segment of the Mid Atlantic Ridge system. Here heat flow is high (up to 330 mW m−2), increasing toward the ridge axis. The coinciding maxima in across‐margin BSR width and heat flow suggest that the Knipovich Ridge influenced methane generation in this area. This is supported by recent finds of thermogenic methane at cold seeps north of the ridge termination. To evaluate the source rock potential on the western Svalbard margin, we applied 1‐D petroleum system modeling at three sites. The modeling shows that temperature and burial conditions near the ridge were sufficient to produce hydrocarbons. The bulk petroleum mass produced since the Eocene is at least 5 kt and could be as high as ~0.2 Mt. Most likely, source rocks are Miocene organic‐rich sediments and a potential Eocene source rock that may exist in the area if early rifting created sufficiently deep depocenters. Thermogenic methane production could thus explain the more widespread presence of gas hydrates north of the Knipovich Ridge. The presence of microbial methane on the upper continental slope and shelf indicates that the origin of methane on the Svalbard margin varies spatially.

The history and future trends of ocean warming‐induced gas hydrate dissociation in the SW Barents Sea

“…Most of the above mentioned studies, however, do not consider how thermogenic gas hydrates could be affected by ocean warming, though it can occupy a much larger region both laterally and vertically in the sediments and could potentially store more carbon than pure methane hydrates. This can be particularly important in the Barents Sea as well as Vestnesa Ridge, Beaufort Shelf, and Kara Sea in the Arctic, where petroleum systems are known to exist [ Spencer et al ., ; Dumke et al ., ]. The total amount of carbon released during hydrate dissociation is halved if we omit SII hydrates from the hydrate dissociation estimate in the SW Barents Sea.…”

Chronology of the Fram Slide Complex offshore NW Svalbard and its implications for local and regional slope stability

“…For normal move out correction an interpolated and extrapolated 3D velocity model based on regional velocity information from multichannel seismic data (Sarkar et al, 2012) was used. Common midpoint (CMP) profiles were generated through crooked-line binning with a CMP spacing of 1.5625 before applying an amplitude preserving Kirchhoff poststack time migration (Dumke et al, 2016).…”

Detection of Gas Hydrates in Faults Using Azimuthal Seismic Velocity Analysis, Vestnesa Ridge, W‐Svalbard Margin

“…Considering the suggested presence of thermogenic gas (Panieri et al, ; Plaza‐Faverola et al, ; Smith et al, ) in the study area, the study of fault/fracture systems is even more important as thermogenic gases have deeper origins (often below the GHSZ) and structural features affect the migration pathways of thermogenic gases. Faults at deeper depths in this region can be potential fluid migration pathways for deep sourced warm fluids (Knies et al, ; Dumke et al, ; Waghorn et al, ), whereas faults at the shallower depths within the GHSZ can be migration pathways or can also act as seals, as they can potentially be plugged with gas hydrates (Goswami et al, ; Madrussani et al, ).…”