New research using drilling samples points to a widespread Miocene-age petroleum system in the eastern Nordic Seas that is similar to prolific producing basins offshore West and Central Africa.
The study published this week on the Marine and Petroleum Geology journal analyzed results from the Ocean Drilling Program at Site 909 in the central Fram Strait and Site 985 in the Iceland Sea; International Ocean Discovery Program Expedition 396 at Site U1572 in the Vøring Plateau; exploration wells 6608/10-1 in the Mid-Norwegian margin; and exploration well 7316/5-1 in the southwestern Barents Sea. The work was authored by researchers in Norway, including from the country’s regulator for upstream oil and gas activities.
Boreholes and oil seeps showed mature Miocene rocks generating hydrocarbons beneath a kilometer-thick Plio-Pleistocene cover in the southwestern Barents Sea, according to the study.
Biomarkers found in oil seeps and borehole sediments from the sites share similar characteristics with those of Niger Delta crude, which come from rocks containing mixed marine and terrestrial fossils, it said.
“One of the most exciting results is that the studies document a young source rock from what used to be a large-scale deltaic sedimentary environment in large parts of the Norwegian Sea”, Rune Mattingsdal, a co-author from the Norwegian Offshore Directorate (NOD), was quoted as saying in an online statement by the regulator. “The sedimentary conditions can best be compared with the conditions in the Niger and Congo deltas off the coast of West Africa”.
The NOD said the study shows potential for unexplored locations in the Norwegian Sea that have already been awarded under Norway’s Awards in Pre-Defined Areas.
“The organic-rich sediments from ODP/IODP Holes 909C, 985A and U1572B contain strong terrestrial input, evidenced by the presence of angiosperm-derived biomarkers such as oleanane and its precursor, olean-12-ene”, the study said. “These compounds, along with the sterane, hopane and diasterane distributions, reveal a clear genetic link between the oils from the Molloy and Prins Karls Forland oil seeps offshore western Svalbard and the Miocene source rocks in the studied boreholes.
“The presence of these biomarkers, in combination with age-diagnostic indices like the Nordiacholestane Ratio and the oleanane index, confirms that the oil seepage is sourced from Tertiary, deltaic source rocks rich in type III kerogen. These findings align with tectonic and sedimentological data indicating widespread delta formation during the Early to Middle Miocene, caused by regional uplift events in areas such as East Greenland, the Barents Sea and central Norway. These deltas supplied substantial terrestrial organic matter into a restricted marine basin, producing ideal conditions for source rock deposition under varied redox conditions.
“The conceptual analogies drawn with the Niger Delta and Congo fan systems are particularly instructive. In all three cases, deep marine sediments enriched with terrestrial organic material – delivered by river systems and deltaic outflows – served as efficient petroleum source rocks. The Miocene Nordic Seas system resembles this model, with high TOC values, angiosperm-derived biomarkers and signs of oil generation in both surface seeps and deep subsurface sediments.
“Basin modeling on the margin of the SW Barents Sea, using seismic lines and exploration well 7316/5-1, confirms the maturity of Miocene source rocks buried under kilometer-thick Plio-Pleistocene glacial sediments. The thermal modelling at a Pseudo Well along the seismic line indicates that large parts of this source rock are currently within the main oil window, having been buried deep enough to reach hydrocarbon-generating temperatures. The detection of olean-12-ene in immature sections further upslope towards the shelf edge (well 7316/5-1) corroborates the terrestrial origin and early maturity stage of this source rock.
“Furthermore, the corresponding biomarker composition of oils from seeps and boreholes throughout the region provides strong evidence of a coherent petroleum system. The spatial distribution – from the Arctic-Atlantic Gateway (Fram Strait) to the SW Barents Sea and Mid-Norwegian margin – suggests a geographically extensive Miocene source rock interval. The confirmation of such a system not only advances geological understanding but also highlights untapped petroleum exploration potential in underexplored regions like the SW Barents Sea.
“While further drilling and sampling are needed to validate the economic viability of this system, the presence of biomarkers such as oleanane and olean-12-ene across a variety of maturity levels and settings demonstrates a consistent source input and a dynamic depositional environment.
“Collectively, these findings indicate that the Miocene source rocks of the eastern Nordic Seas represent a significant, deltaic-driven petroleum system analogous to some of the world’s most productive offshore basins.
“Potential play types include stratigraphic traps in slope and basin floor fans, and structural traps related to Miocene deltaic loading and Plio-Pleistocene glacial overburden.
“However, key exploration risks remain, particularly in terms of reservoir quality, seal integrity and migration pathways within glacially modified margins”.
To contact the author, email jov.onsat@rigzone.com
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