Petroleum Geology of the Dreki area on the Jan …IEC-2008 1 Petroleum Geology of the Dreki area on...
Transcript of Petroleum Geology of the Dreki area on the Jan …IEC-2008 1 Petroleum Geology of the Dreki area on...
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Petroleum Geology of the Dreki area on the Jan Mayen
Ridge
Þórarinn Sveinn ArnarsonHydrocarbon Licensing Manager
National Energy Authority, Energy Resources
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Acknowledgements• Steinar Þór Guðlaugsson and Bjarni Richter
– Formerly at Iceland Geosurvey (ÍSOR), now at GeysirGreen Energy
• Anett Blischke at Iceland Geosurvey• Many previous contributors
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Outline
• Introduction to the Icelandic continental shelf• Overview of geological research of the area• Geology of the Jan Mayen Ridge• Hydrocarbon resource potential of the Jan
Mayen Ridge
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Outline
• Introduction to the Icelandic continental shelf
• Overview of geological research of the area• Geology of the Jan Mayen Ridge• Hydrocarbon resource potential of the Jan
Mayen Ridge
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Icelandic Continental Shelf
• Solid lines: EEZ boundaries
• Dashed lines: continental shelf claims by Iceland
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Iceland GeoSurvey 2008
Northern Dreki licensing round
Three areas on the Icelandic continental shelf with potential for commercial accumulations of oil and gas
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Oil shows
Oil and gas fields
Jan Mayen Ridge
NorthernDreki area
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The northern Dreki area in relation to hydrocarbon basins in East Greenland, the North Sea and offshore western
Norway and Shetland
• Jan Mayen Ridge geologically similar to neighbouring hydrocarbon basins
• Next door neighbours prior to the opening of the northeast Atlantic ocean basin
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JM Agreement Area
Northern Dreki Area
Jan Mayen
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Bathymetric map and limits of the northern
Dreki Area
• Water depths in the northern Dreki Area mostly range from 800 to 2000 m
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NorthernDrekiArea
Jan MayenAgreementArea
Jan Mayen
IcelandIceland GeoSurvey2008
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Outline
• Introduction to the Icelandic continental shelf• Overview of geological research of the
area• Geology of the Jan Mayen Ridge• Hydrocarbon resource potential of Jan
Mayen Ridge
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Academic interest in the geology of the Jan Mayen Ridge
• The Jan Mayen Ridge is magnetically quiet
• It is a microcontinent – a piece of continental crust stranded in the middle of the northeast Atlantic
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Academic research of the Jan Mayen Ridge –multi channel seismic
• French survey in 1975 (Cepan 1) by CNEXO
• German survey by Bundesanstalt für Geowissenschaften und Rohstoffe in 1975 and 1976
• British cruise by the University of Durham in 1977
• University of Bergen survey in 1978, mostly on the northern part of the ridge
• US cruise by Lamont-Doherty Geological Observatory in 1979
• University of Oslo survey in 1986Iceland GeoSurvey 2008
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• NPD-survey in 1979• NPD-NEA survey in 1985• NPD-NEA survey in 1988
• Total: 5500 km of 2D-seismic lines
Icelandic and Norwegian seismic surveys
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• Non-exlusive, prospecting survey in 2001• 2800 km of 2D-
seismic data• Additional 850 km infill
survey in 2008(approximate locations)
Seismic surveys by Wavefield-Inseis
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Seismic refraction data
• Sonobuoy locations (red dots) from NPD-NEA surveys in 1985 and 1988
• Expanding Spread Profiles (blue lines and dots) by Institut Francais du Petrole in 1987 and L-DGEO in 1979
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Deep Sea Drilling Project boreholes
• Five shallow boreholes drilled in the area during DSDP Leg 38 in 1974• Water depths ranged
between 700 and 1800 m• Penetration depths
ranged between 180 and 550 m
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Outline
• Introduction to the Icelandic continental shelf• Overview of geological research of the area• Geology of the Jan Mayen Ridge• Hydrocarbon resource potential of the Jan
Mayen Ridge
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Bott 1985
The Jan Mayen Ridge (light brown) was separated from the continental shelfs of Greenland and Norway
by plate tectonic movements
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Bott 1985
Subsequently new ocean floor (blue) was gradually created around active oceanic ridges
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Bott 1985
Kolbeinsey Ridge initially most active in the south, Aegir Ridge becomes extinct
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Bott 1985
Jan Mayen Ridge continues to move away from Greenland as a result of sea-floor spreading
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Oceanic crust in the Norway Basin
Wedge-shaped piles of lava flows formed at the beginning of seafloor-spreading in the Norway basin when the ridge was separated from the Norwegian continental shelf: -Younger pile
-Older pile
Continental crust with sediments and a layer of lava flows:-Relatively undisturbed
-Extended and extensively faulted during separation from Greenland
Composite sheet of flatlying intrusives covering subsided continental crust just before oceanic crust started to form on the Iceland Plateau
Oceanic crust on the Iceland Plateau
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Gunnarsson, Sand & Gudlaugsson, 1989
Simplified geological map of the Jan Mayen Ridge: based on the 1985 survey
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Gunnarsson, Sand & Gudlaugsson, 1989
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Gunnarsson, Sand & Gudlaugsson, 1989
Igneous features at the eastern margin of the Jan Mayen Ridge and their stratigraphic relationship to sedimentary layers
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57 mya (anomaly 24R) Gunnarsson, Sand & Gudlaugsson, 1989
Initial breakup of the continent and eruption of lavas
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50 mya (anomaly 21) Gunnarsson, Sand & Gudlaugsson, 1989
Sediment accumulation on the East Greenland margin
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30 mya (anomaly 10) Gunnarsson, Sand & Gudlaugsson, 1989
Rifting within the East Greenland margin – erosion of the top of the ridge, submarine fans
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21 mya (anomaly 6A) Gunnarsson, Sand & Gudlaugsson, 1989
Breakup to the west of the ridge and emplacement of submarine lavas or sills
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PresentGunnarsson, Sand & Gudlaugsson, 1989
Subsidence due to cooling and thermal contraction. Sedimentation mostly pelagic, some gravity flows
down steep ridge slopes
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Outline
• Introduction to the Icelandic continental shelf• Overview of geological research of the area• Geology of the Jan Mayen Ridge• Hydrocarbon resource potential of the
Jan Mayen Ridge
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Potential surface seeps• Unconfirmed report of gasses in shallow cores within
the northern Dreki area by Soviet scientists on the Akademic Kurchatov in 1973• Interpreted as indications of deep hydrocarbon
sources• Could also have a shallow source from low-
temperature chemical or biochemical processes
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Results from DSDP boreholes• Shallow penetration – only to
Late Eocene age (~40 m.y.)• Sediments with fairly low total
organic content• Oil genesis of organic matter
at a very early stage
• Boreholes did not reach deep enough!
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Potential source rocks
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Potential source rocks• Tertiary post-rift source rocks
• Time of restricted water exchange early in the rifting phase may have resulted in accumulation of organic matter in sediments
• Pre-rift source rocks• Possible analogies with continental margins on
either side of the ocean• The Jan Mayen Ridge was separated earlier from
the Norwegian side than from Greenland• Not known which parts of the Mezosoic or
Paleozoic sequence is present
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Preliminary hydrocarbon maturation modelling
• Two heat flow cases• Moderate heat flow• High heat flow
• Caveats• Uncertainty in subsidence history• Sills may increase maturation locally• Level of maturation strongly influenced by highest
temperature experienced – heat pulses may have large impact
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Preliminary hydrocarbon maturation modelling
Gunnarsson, Sand & Gudlaugsson, 1989
High heat flow: Early Eocene source-rocks have reached oil window
Tertiary source rocks: Immature
Mesozoic source rocks: In gas window ( high)In oil window (moderate)
Tertiary source rocks: At most very early oil-matureMesozoic source rocks: Overcooked (high)In late oil or gas window
(moderate)
Tertiary source rocks:
Early Eocene early oil-mature (moderate)
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Sheet of basalt intrusives
Wedge of lava flows
Listric fault complex
Transverse structural/volcanic high
Sills above lavas
Normal fault
Reverse fault
Areas with potentialhydrocarbon traps
From Åkermoen 1989 & Sagex 2006
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From Sagex 2006 and Åkermoen 1989
Areas with potential hydrocarbontraps, from Sagex (2006)
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Surface pockmarks in the northern Dreki area
• Surface pockmarks were discovered in June 2008 during a multibeam-study of the Dreki area led by Gudrún Helgadóttir of the Marine Research Institute
• Pockmarks had been found on the Norwegian side during the 1985 survey
• Pockmarks have been found at the bottom of the North sea, and sometimes cluster around major hydrocarbon fields
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Origin of pockmarks• There are several potential explanations for the
formation of pockmarks at the sea floor• They can be a result of eruptions of gashydrates
that have become unstable and get “gassed out”• They can be formed by seepage of gas through
the sea-bottom• This gas could be methane formed in situ at
shallow depth• A deep hydrocarbon source for the gas is also
possible• Analysis of surface sediment cores from pockmarks
and/or fault lines with modern equipment has not been done yet to determine if there is a surface seepage of hydrocarbons in the area
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Satellite hydrocarbon seep study
• The National Energy Authority is funding a preliminary study of satellite radar-images to search for natural oil seepage in the Dreki Area• The leader of the project is Ingibjörg Jónsdóttir,
Associate Professor at the University of Iceland• A report on the investigation is due to be released
in December 2008
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Hydrocarbon Potential in the Dreki Area
• Sedimentary rocks of sufficient thickness and age
• Indications of pre-opening sedimentary strata
• Potental source rocks similar to East Greenland
• Potential reservoir rocks, including submarine fans
• Potential traps present, both structural and stratigraphic
• Seismic anomalies indicate that hydrocarbons may be present