Dag Arild Karlsen

• Abay, Tesfamariam Berhane; Karlsen, Dag Arild; Olaussen, Snorre; Pedersen, Jon Halvard & Hanken, Nils-Martin (2022). Organic geochemistry of Cambro-Ordovician succession of Ny Friesland, Svalbard, High Arctic Norway: Petroleum generation potential and bulk geochemical properties. Journal of Petroleum Science and Engineering. ISSN 0920-4105. 218. doi: 10.1016/j.petrol.2022.111033. Full text in Research Archive Show summary

  Lower Paleozoic source rock (SR) characteristics and paleo-depositional environments are not well understood in the Barents Sea region. Organic and inorganic geochemical analyses of 17 carbonaceous samples from the Lower Cambrian Tokammane Formation, the Lower to Middle Ordovician Kirtonryggen and Valhallfonna formations in Ny Friesland, north-east Spitsbergen, show that there is a striking difference in petroleum generation potential and bulk geochemical properties between the Cambrian and Ordovician samples, and also within the Ordovician samples. TOC contents of <0.20 wt% for the Lower Cambrian Tokammane Formation samples indicate poor source rock richness. TOC contents in the range between 0.3 and 2.1 wt% and HI values between 123 and 424 mg HC/g TOC for the Valhallfonna and Kirtonryggen formation samples suggest significant variation in remaining petroleum generation potential with oil-prone (Type II) to mixed oil- and gas-prone (Type II/III) kerogen. Source rock maturity parameters such as Tmax (range 435–449 °C) and production indices for most Ordovician samples suggest relatively uniform maturity levels, ranging from the early-, to the peak-, of the oil generation window (i.e. ca. 0.70–0.85% Ro). This maturity level could have significant implication on the original petroleum potential assuming early generation from carbonate source rocks. Bulk carbon isotope data show that the Lower Cambrian Tokammane Formation samples are heavier (δ13C range from −28.4 to −28.8‰) than the Lower to Middle Ordovician Valhallfonna Formation samples (δ13C range from −29.7 to −30.9‰). The differences in the source rock richness and kerogen type within the Ordovician samples are attributed to organic facies variation. Tentatively, three categories of source rock organic facies (B, BC and C) are supported based on assumed-initial hydrogen index values for the Ordovician samples. The reliability of the indicated organic facies could be supported by addition of biomarker data from bitumen extracts. To our knowledge, this is the first study revealing the existence of a potential Lower Paleozoic source rocks in this part of the High Arctic, and this facies may also exist on the continental shelf to the north and NE.

• Hanken, Nils-Martin; Sztybor, Kamila; Høeg, Helge I.; Karlsen, Dag Arild; Rasmussen, Tine Lander & Abay, Tesfamariam Berhane (2022). Late Quaternary terrigenous plant and coaly fragments found at Vestnesa Ridge, Fram Strait: implications for postglacial plant colonization at Svalbard. Lethaia: An International Journal of Palaeontology and Stratigraphy. ISSN 0024-1164. 55(4), p. 1–13. doi: 10.18261/let.55.4.6. Full text in Research Archive Show summary

  One of four marine cores of glacial sediments collected from a water depth of about 1200 m at Vestnesa Ridge (west of Svalbard) contained small fragments of coal, charcoal and moss. This material was restricted to a single level, and 14C dating of bivalves both above and below indicates an age of c. 18.0–15.5 kyr BP. Chemical analyses of the coal indicate that the provenance area was from the northern part of Andøya, North Norway. The moss fragment was identified as Aulacomnium turgidum, which is a well-known species from the northern part of Andøya, which was an ice-free refugium with tundra vegetation during the Weichselian maximum. One small piece of charcoal with reasonably well-preserved cell structures is derived from burnt Salix sp. These findings are important, because they demonstrate the presence of drift ice carrying organic material from the northern part of Andøya towards the west coast of Svalbard during Heinrich event H1, an event of extensive ice-rafting in the Nordic seas. This also implies that some components of the vascular plant communities growing on Svalbard today, might originally have been imported as seeds floating on sea ice, before stranding along the coast of Svalbard. The plant colonization of Svalbard can thus have started already during Heinrich event H1. The finding of charcoal can only be explained by a fire due to lightning and not by campfire, because the first human population arrived in northern Norway at a much later time (probably during Preboreal). The charcoal is thus from the oldest known wild fire in Norway.

• Ohm, Sverre Ekrene; Larsen, Leif; Olaussen, Snorre; Senger, Kim; Birchall, Thomas & Demchuk, Thomas [Show all 11 contributors for this article] (2019). Discovery of shale gas in organic-rich Jurassic successions, Adventdalen, Central Spitsbergen, Norway. Norwegian Journal of Geology. ISSN 2387-5844. 99(2), p. 349–376. doi: 10.17850/njg007. Full text in Research Archive Show summary

  Thermogenic dry gas flowed from Jurassic sections in the DH5R research well drilled onshore in Adventdalen, central Spitsbergen, Arctic Norway. The DH5R gas originates from the organic-rich units of the mudstone-dominated Middle Jurassic to Lower Cretaceous Agardhfjellet Formation, which is the onshore equivalent to the Fuglen Formation and the prolific oil and gas generating Hekkingen Formation in the southern Barents Shelf. Low-permeable, low-porosity sandstones from the Upper Triassic De Geerdalen Formation of the neighbouring DH4 well were oil-stained and gas was also collected from this interval. Gas from the two stratigraphic intervals have different compositions; the gas from the Agardhfjellet Formation is drier and isotopically heavier than the gas from the Upper Triassic succession. Both gases originated from source rocks of maturity near the end of the oil window (1.1 < Ro < 1.4% Ro). Maceral analyses of the Agardhfjellet Formation indicate that the more silty parts contain a high percentage of vitrinite-rich type III kerogen, whereas the clay-dominated parts are rich in liptinitic type II kerogen. The Agardhfjellet Formation has therefore the potential to generate both oil and gas. Several simulations based on pressure data and flow rates from the DH5R well were run to evaluate if the gas accumulation in the Agardhfjellet Formation is producible, i.e., can it be commercial shale gas. The models demonstrate how changes in the drainage area size and form, well types (vertical versus horizontal), number and length of induced fractures and thickness of the Agardhfjellet Formation affect gas production rates and producible volumes. Despite uncertainties in the input data, simulations indicate that the shale gas accumulation characterised in Adventdalen is producible. This gas can have major environmental benefits as an alternative for local power generation compared to coal.

• Abay, Tesfamariam Berhane; Karlsen, Dag Arild; Olaussen, Snorre & Pedersen, Jon Halvard (2019). Organic geochemistry of petroleum in the Cambro-Ordovician succession of NY Friesland, Spitsbergen, Svalbard. 29th International Meeting on Organic Geochemistry. doi: 10.3997/2214-4609.201902714. Full text in Research Archive
• Matapour, Zagros; Karlsen, Dag Arild; Lerch, Benedikt & Backer-Owe, Kristian (2019). Petroleum occurrences in the carbonate lithologies of the gohta and alta discoveries in the barents sea, arctic Norway. Petroleum Geoscience. ISSN 1354-0793. 25(1), p. 50–70. doi: 10.1144/petgeo2017-085. Full text in Research Archive
• Abay, Tesfamariam Berhane; Fossum, Katrine; Karlsen, Dag Arild; Dypvik, Henning; Narvhus, Lars J Jørgensen & Haid, Muna Hassan Mohamoud [Show all 7 contributors for this article] (2019). Petroleum geochemical aspects of the Mandawa Basin, coastal Tanzania: The origin of migrated oil occurring today as partly biodegraded bitumen. Petroleum Geoscience. ISSN 1354-0793. doi: 10.1144/petgeo2019-050. Full text in Research Archive Show summary

  The shallow marine Upper Jurassic to Lower Cretaceous sedimentary successions of the Mandawa Basin, coastal Tanzania, are located about 80 km away from the offshore gas discoveries of Block 2, Tanzania. In this paper we present petroleum geochemical data, including bitumen extracted from outcrop samples which are relevant to the understanding of the onshore “Petroleum System” and possibly also to the offshore basin. Despite some biodegradation and weathering, common to all outcrop samples, most bitumen samples analyzed contain mature, migrated oil. The maturity span of geomarkers (C13-C15 range) covers the entire oil and condensate/wet gas window (Rc = 0.7–2% Rc), with the biomarkers generally indicating the oil window (Rc = 0.7–1.3% Rc). This suggests that the bitumen extracts represent several phases of migrated oil and condensate, which shows that the samples are part of an active or recently active migration regime or “Petroleum System”. The source rock facies inferred for the bitumen is Type II/III kerogen of siliciclastic to carbonate facies. This is oil-prone kerogen, typical for a marine depositional system with influx of proximal derived terrigenous material blended in with in situ marine algal organic matter (OM). Application of age specific biomarkers such as the C28/C29 steranes, extended tricyclic terpane ratio (ETR), nordiacholestanes and the aromatic steroids suggest that more than one source rock have contributed to the bitumen. Possible ages are limited to the Mesozoic i.e. excluding the Late Paleozoic, with the most likely source rock belonging to the Early Jurassic. More geochemical and geological studies should be undertaken to further develop the general understanding of the petroleum system of the Mandawa Basin and its implications to the “Petroleum Systems” both offshore and onshore. This paper also presents a reinterpretation of published gas composition and isotope data on the Pande, Temane and Inhassoro gas fields (Mozambique) with implications for possible oil discoveries in the gas dominated region.

• Lerch, Benedikt; Karlsen, Dag Arild; Thießen, Olaf; Abay, Tesfamariam Berhane; Soelen, Elsbeth Ester van & Kürschner, Wolfram Michael [Show all 8 contributors for this article] (2018). Investigations on the use of triaromatic dimethylcholesteroids as age-specific biomarkers in bitumens and oils from Arctic Norway. Organic Geochemistry. ISSN 0146-6380. 122, p. 1–16. doi: 10.1016/j.orggeochem.2018.04.011. Full text in Research Archive
• Abay, Tesfamariam Berhane; Karlsen, Dag Arild; Pedersen, Jon Halvard; Olaussen, Snorre & Backer-Owe, Kristian (2018). Thermal maturity, hydrocarbon potential and kerogen type of some Triassic-Lower Cretaceous sediments from the SW Barents Sea and Svalbard. Petroleum Geoscience. ISSN 1354-0793. 24(3), p. 349–373. doi: 10.1144/petgeo2017-035. Full text in Research Archive
• Matapour, Zagros & Karlsen, Dag Arild (2018). Ages of Norwegian oils and bitumen based on age-specific biomarkers. Petroleum Geoscience. ISSN 1354-0793. 24(1), p. 92–101. doi: 10.1144/petgeo2016-119. Full text in Research Archive
• Lerch, Benedikt; Karlsen, Dag Arild; Seland, Reinert & Backer-Owe, Kristian (2017). Depositional environment and age determination of oils and condensates from the Barents Sea. Petroleum Geoscience. ISSN 1354-0793. 23(2), p. 190–209. doi: 10.1144/petgeo2016-039. Full text in Research Archive
• Matapour, Zagros & Karlsen, Dag Arild (2017). GEOCHEMICAL CHARACTERISTICS OF THE SKRUGARD OIL DISCOVERY, BARENTS SEA, ARCTIC NORWAY: A "PALAEO-BIODEGRADED- GAS REACTIVATED" HYDROCARBON ACCUMULATION. Journal of Petroleum Geology. ISSN 0141-6421. 40(2), p. 125–152. doi: 10.1111/jpg.12669. Full text in Research Archive
• Abay, Tesfamariam Berhane; Karlsen, Dag Arild; Lerch, Benedikt; Olaussen, Snorre; Pedersen, Jon Halvard & Backer-Owe, Kristian (2017). Migrated petroleum in outcropping Mesozoic sedimentary rocks in Spitsbergen: organic geochemical characterization and implications for regional exploration. Journal of Petroleum Geology. ISSN 0141-6421. 40(1), p. 5–36. doi: 10.1111/jpg.12662. Full text in Research Archive
• Lerch, Benedikt; Karlsen, Dag Arild; Abay, Tesfamariam Berhane; Duggan, Deirdre; Seland, Reinert & Backer-Owe, Kristian (2016). Regional petroleum alteration trends in Barents Sea oils and condensates as a clue to migration regimes and processes. American Association of Petroleum Geologists Bulletin. ISSN 0149-1423. 100(2), p. 165–190. doi: 10.1306/08101514152. Full text in Research Archive
• Lerch, Benedikt; Karlsen, Dag Arild; Matapour, Zagros; Seland, Reinert & Backer-Owe, Kristian (2016). Organic geochemistry of barents sea petroleum: Thermal maturity and alteration and mixing processes in oils and condensates. Journal of Petroleum Geology. ISSN 0141-6421. 39(2), p. 125–148. doi: 10.1111/jpg.12637. Full text in Research Archive
• Abay, Tesfamariam Berhane; Karlsen, Dag Arild & Ohm, Sverre Ekrene (2014). Vertical variations in reservoir geochemistry in a palaeozoic trap, Embla Field, offshore Norway. Journal of Petroleum Geology. ISSN 0141-6421. 37(4), p. 349–372. doi: 10.1111/jpg.12590. Full text in Research Archive
• Ohm, Sverre Ekrene; Karlsen, Dag Arild; Phan, Trung Nghia; Strand, Tor & Ivevsen, Gunnar (2012). Present Jurassic petroleum charge facing Paleozoic biodegraded oil: Geochemical challenges and potential upsides, Embla field, North Sea. American Association of Petroleum Geologists Bulletin. ISSN 0149-1423. 96(8), p. 1523–1552. doi: 10.1306/01021211094. Full text in Research Archive
• Koeverden, Jan Hendrik van; Karlsen, Dag Arild & Backer-Owe, Kristian (2011). CARBONIFEROUS NON-MARINE SOURCE ROCKS FROM SPITSBERGEN AND BJORNOYA: COMPARISON WITH THE WESTERN ARCTIC. Journal of Petroleum Geology. ISSN 0141-6421. 34(1), p. 53–66. doi: 10.1111/j.1747-5457.2011.00493.x. Full text in Research Archive
• Koeverden, Jan Hendrik van; Nakrem, Hans Arne & Karlsen, Dag Arild (2010). Migrated oil on Novaya Zemlya, Russian Arctic: Evidence for a novel petroleum system in the eastern Barents Sea and the Kara Sea. American Association of Petroleum Geologists Bulletin. ISSN 0149-1423. 94(6), p. 791–817. doi: 10.1306/10200909146. Full text in Research Archive
• Koeverden, Jan Hendrik van; Karlsen, Dag Arild; Schwark, L; Chpitsglouz, A & Backer-Owe, Kristian (2010). OIL-PRONE LOWER CARBONIFEROUS COALS IN THE NORWEGIAN BARENTS SEA: IMPLICATIONS FOR A PALAEOZOIC PETROLEUM SYSTEM. Journal of Petroleum Geology. ISSN 0141-6421. 33(2), p. 155–181. doi: 10.1111/j.1747-5457.2010.00471.x. Full text in Research Archive
• Ohm, Sverre Ekrene; Karlsen, Dag Arild & Austin, TJF (2008). Geochemically driven exploration models in uplifted areas: Examples from the Norwegian Barents Sea. American Association of Petroleum Geologists Bulletin. ISSN 0149-1423. 92, p. 1191–1223. doi: 10.1306/06180808028. Full text in Research Archive
• Pedersen, Jon Halvard; Karlsen, Dag Arild; Spjeldnæs, Nils; Backer-Owe, Kristian; Lie, JE & Brunstad, H (2007). Lower Paleozoic petroleum from southern Scandinavia: Implications to a Pleozoic petroleum system offshore southern Norway. American Association of Petroleum Geologists Bulletin. ISSN 0149-1423. 91, p. 1189–1212. doi: 10.1306/03080706020. Full text in Research Archive
• Ohm, Sverre Ekrene; Karlsen, Dag Arild; Backer-Owe, Kristian; Pedersen, Jon Halvard & Beeley, H. S. (2007). A drilling mud additive influencing the geochemical interpretations of hydrocarbon shows. Petroleum Geoscience. ISSN 1354-0793. 13, p. 369–376. Full text in Research Archive
• Svensen, Henrik; Karlsen, Dag Arild; Sturz, Anne; Backer-Owe, Kristian; Banks, David A. & Planke, Sverre (2007). Processes controlling water and hydrocarbon composition in seeps from the Salton Sea geothermal system, California, USA. Geology. ISSN 0091-7613. 35(1), p. 85–88. doi: 10.1130/G23101A.1. Full text in Research Archive
• Ohm, Sverre Ekrene & Karlsen, Dag Arild (2007). Biogenic gas(?) in fluid inclusions from sandstones in contact with oil-mature coals. American Association of Petroleum Geologists Bulletin. ISSN 0149-1423. 91(5), p. 715–739. doi: 10.1306/11280606021. Full text in Research Archive
• Ohm, Sverre Ekrene; Beeley, H; Karlsen, Dag Arild; Hall, PB & Foss, A (2006). An atypical early mature oil in Block 35/1, Norwegian North Sea - hypersaline, carbonate Jurassic environment? Petroleum Geoscience. ISSN 1354-0793. 12, p. 157–174. Full text in Research Archive
• Karlsen, Dag Arild & Skeie, JE (2006). Petroleum migration, faults and overpressure, Part I: Calibrating basin modelling using petroleum in traps - A review. Journal of Petroleum Geology. ISSN 0141-6421. 29, p. 227–255. Full text in Research Archive
• Ohm, Sverre Ekrene; Karlsen, Dag Arild; Roberts, A.; Johannessen, E. & Høiland, O. (2006). The Paleocene sandy Siri fairway: an efficient "pipeline" draining the prolific Central Graben? Journal of Petroleum Geology. ISSN 0141-6421. 29, p. 53–82. Full text in Research Archive
• Pedersen, Jon Halvard; Karlsen, Dag Arild; Lie, Jan Erik; Brunstad, Harald & Primio, Rolando di (2006). Maturity and source-rock potential of palaeozoic sediments in the NW European Northern Permian Basin. Petroleum Geoscience. ISSN 1354-0793. 12, p. 13–28. Full text in Research Archive Show summary

  ABSTRACT: The Northern Permian Basin is located in the offshore area SSW of Norway, NNW of Denmark and east of Scotland. This basin is filled mainly by Lower Permian aeolian desert sediments and volcanics, plus Upper Permian evaporitic sediments. The aeolian sandstone is an excellent reservoir rock and is generally capped by thick layers of salt that potentially form a tight cap rock. The highest risk in the petroleum exploration of the Palaeozoic Northern Permian Basin is linked to the presence of source rocks. Palaeozoic source-rock candidates in the Northern Permian Basin area may be present among Lower Palaeozoic marine sediments, within Devonian–Carboniferous lacustrine/deltaic pre- and syn-rift sediments and as Permian marine shales. This study investigates Lower Palaeozoic marine shales, lacustrine Devonian mudstones, Carboniferous mudstones and coals and marine Permian shales in order to assess the thermal maturity, source-rock potential and distribution of Palaeozoic sediments in the Northern Permian Basin region. The majority of the investigated samples were within the oil window in terms of thermal maturity. Lower Palaeozoic marine sediments may have generated both oil and gas, while Upper Palaeozoic coals and mudstones are dominantly gas-prone source rocks. Middle Permian marine shales (Kupferschiefer) are a good oil-prone source rock. Generation and expulsion of hydrocarbons from Lower Palaeozoic source rocks in the eastern parts of the Northern Permian Basin probably began in the Upper Silurian, with peak oil generation in Carboniferous times. Upper Palaeozoic rocks in the same area matured rapidly in Early Triassic times. The likely presence of multiple Palaeozoic source rocks suggests that hydrocarbons were generated in the Northern Permian Basin.

• Pedersen, Jon Halvard; Karlsen, Dag Arild; Backer-Owe, Kristian; Lie, Jan Erik & Brunstad, Harald (2006). The geochemistry of two unusual oils from the Norwegian North Sea: implications for new source rock and play scenario. Petroleum Geoscience. ISSN 1354-0793. 12, p. 85–96. Full text in Research Archive Show summary

  ABSTRACT: Two oils from the Norwegian North Sea and a source-rock extract from the Danish North Sea are seen to have chemical properties deviating from any previously known North Sea oils. An organic geochemical investigation concludes that the two oils are of low to medium maturity, and that these oils represent alternative organic facies of Upper Jurassic age. The organic facies that sourced the investigated oils are believed to be hypersaline and carbonate-type source rocks, which were most likely deposited in locally developed, secluded lagoonal settings with elevated salinity and low clastic influx. The alternative source rocks inferred by the two atypical oils may add new concepts to petroleum exploration on the margins of the Mesozoic Central Graben and Viking Graben in the North Sea.

• Karlsen, Dag Arild; Skeie, Jon Erik; Backer-Owe, Kristian & Bjørlykke, Knut (2004). PETROLEUM MIGRATION, FAULTS AND OVERPRESSURE-Part II--CASE HISTORY-THE HALTENBANKEN PETROLEUM PROVINCE, OFFSHORE NORWAY. Geological Society Special Publication. ISSN 0305-8719. 237, p. 305–372. Full text in Research Archive Show summary

  Petroleum inclusion and geochemical data from core extracts were applied to deduce model for oil migration, over-pressure development and paleo-leakage of oil from currently dry structures in the Haltenbanken Vest area. The existence of fluorescent oil type inclusions in quartz in the Smørbukk (Åsgard-2) field suggest that oil migrated into this structure 70-50 million years before present (M.Y.b.p.). This is also the case for the dry structures 6506/12-4, 6506/11-3 and 6506/11-1, west of the main Smørbukk Fault Zone. Black oil inclusions with medium gas to oil ratio (GOR) occur in these fields together with condensate type petroleum inclusions. This suggests that the dry structures transformed from containing oil to condensate before leakage. Petroleum extracted from inclusions in these structures and in nearby fields have identical marine type II kerogen signatures. Source rocks at the Spekk Fm. level in the current drainage area of Smørbukk and these dry structures, were immature 70-50 M.Y.b.p. and the Smørbukk Sør (Åsgard-3) field did not fill at this early time. Thus, oil must initially have entered into Smørbukk from areas to the west-south west, through the currently pressure sealing Smørbukk Fault Zone which today marks the westward limit of the Smørbukk field. Diagenesis in this fault zone caused the much later overpressure development and petroleum was lost from the 6506/12-4, 6506/11-3 and 6506/11-1 structures as overpressure built up regionally. Petroleum loss from these structures with their often thick seals must have occurred via self-propagating open-fracture induced mechanisms. Lack of petroleum in the Cretaceous strata above these structures suggests that leakage occurred to even shallower strata. This could imply that the Cretaceous strata in Halten Vest were over-pressured at the time of leakage. In contrast, the oil in the Cretaceous Lysing and Lange Fm. (above the Jurassic reservoirs in Smørbukk and Smørbukk Sør) most likely originated (based on geochemistry and gas to oil ratios) from the Jurassic reservoirs below and not from Cretaceous strata. This migration event would have been facilitated if it occurred before these sands became over-pressured as they are today. Modelling suggests that the Spekk Fm. became mature in the Smørbukk Sør region < 10 M.Y.b.p. and microthermometry of oil inclusions from Smørbukk Sør supports filling during the last 10 M.Y. This implies that cap-rock failure in the Halten Vest structures 6506/12-4, 6506/11-1 and 6506/11-3 most likely occurred after filling of the Smørbukk Sør and 6406/3-1 structures. Rapid regional burial during the last 10 M.Y. caused local migration of oil into Smørbukk Sør, Smørbukk and 6406/3-1 structures, and generation of high gas to oil ratio oils (GOR) in the deeper Halten Vest region. High GOR petroleum inclusions in the Halten Vest structures signifies this event and suggests that cap rock fracturing occurred after a gas/condensate had replaced oil in these traps. Rapid burial during the last 3 M.Y. is likely to have caused the current overpressure and associated leakage in Halten Vest. The fact that these traps did not later refill in this progressively subsiding and maturing basin must be related to trap pressures remaining too close to the actual fracture pressures.

• Skeie, Jon Erik; Primio, Rolando Di; Karlsen, Dag Arild & Bjørlykke, Knut (2004). An integrated basin modelling study applying asphaltene kinetics from reservoired petroleum in the Snorre Area, northern North Sea. Geological Society Special Publication. ISSN 0305-8719. 237, p. 133–155. Full text in Research Archive
• Bhullar, Abid Ghafoor; Primio, Rolando Di; Karlsen, Dag Arild & Gustin, D.P. (2003). Determination of the Timing of Petroleum System Events Using Petroleum Geochemical, Fluid Inclusion, and PVT Data: An Example from the Rind Discovery and the Frøy Field, Norwegian North Sea. AAPG Datapages Discovery Series. p. 123–135. Full text in Research Archive Show summary

  The characteristics of oils in the subsurface as well as the hydrocarbon filling history of the Frøy Field and the Rind Discovery, blocks 25/5 and 25/2 Norwegian North Sea, were studied using geologic, organic geochemical, fluid inclusion, and pressure, volume, and temperature (PVT) data. Geochemical signatures of present and PaJeopetroleum distributions in combination with microthermometry of fluid inclusions are integrated in this study with burial history modeling to understand the filling history of these structures and the timlng of the main petroleum system events. Oils from the Rind Discovery are significantly different from the fluids encountered in Frøy Field, indicating that these structures received oil from different kitchen areas. In the Rind Discovery, migration of oil between the main southem compartment and the presently dry and overpressured adjacent northern compartment was timed relatively, based on the maturity differences in the bitumen from these two structures, as well as using fluid inclusion data. Sealing of the fault between these two compartments, caused by fault movement and/or diagenesis, disrupted communication, and the caprock failed because of pressure buildup in the presently dry northen structure. The oil charge in the main structure was preserved from pressure buildup because of communication updip. The difference in the homogenization temperatures of the petroleum and aque- ous inclusions from these two compartments was used in combination with their burial histories, to bracket the time for overpressure buildup and leakage. Within the Frøy Field, geochemical analyses indicated that most of the oils en- countered belonged to one uniform population, a conclusion supported by the PVT data. However, one of the compartments contained slightly biodegraded oil that was entirely different from the oil in the rest of the field. This biodegraded oil is believed to be sourced from Dunlin Group shales, and the presence of this oil in this isolated com- partment indicates a lack of communication with the main reservoir strata of the Frøy Field. Maturity differences between the oils sampled from the Frey indicated that the most mature oils are encountered at the crest of the reservoir and oils of decreasing maturity occur toward the flanks, suggesting that this trap was filled in the usual top- and down-flank style. Using the burial history of the Frøy Field, we determined that the filling of the subcompartment holding the biodegraded oil must have occurred at about 40 Ma, before oil from the Late Jurassic Draupne shales more homogeneously filled the main Frøy structure. The integration of the geochemical data obtained from the Rind Discovery and the Frey Field with 1-D basin modeling of both the reservoir and kitchen areas allowed the timing of the main petroleum system events to be constrained, namely, the generation, migration, emplacement, and leakage of hydrocarbons in the study area.

• Karlsen, Dag Arild; Backer-Owe, Kristian; Bjørlykke, Knut; Schaefer, Rainer G.; Bhullar, Abid Ghafoor & Angard, Kristian [Show all 11 contributors for this article] (2003). Faults and Oil Migration in the Halten Vest High Pressure and Haltenbanken Normal Pressure Regimes, Offshore Norway. AAPG Datapages Discovery Series. p. 343–346. Full text in Research Archive Show summary

  The occurrence and geochemistry of fluid inclusions in authigenic mineral cements in addition to chemical characterization of bitumen and oil was used to provide a model for hydrocarbon sourcing and migration in the Smørbukk and Halten Vest region. We have found evidences to suggest that the main fault zone west of Smeørbukk, which today forms a pressure seal, was open for petroleum migraton from the west at least as early as 50 m.y.b.p. The presently dry structures in the Halten Vest region experienced cap-rock leakage upon receiving petroleum from the Spekk Formation and the subsequent genetically associated development of too high petroleum columns was evidently the cause of leakage as the region experienced a build up in pressure. The pressure build up must have occured at a time when the fault zone west of Smerbukk transformed from open to sealing. The same abundance of fluorescent petroleum inclusions in the Halten Vest dry wells as in Smørbukk implies according to our model that the time during which the presently dry Halten Vest structures actually held oil is roughly similar to the time petroleum has been present in Smerbukk. This implies that cap rock leakage in Halten Vest must have occurred, in geological terms, very recent. Petroleum migration from the vest through the presently sealing Smørbukk main fault zone should according to the homogenisation temperatures measured on the inclusions have occurred as early as 70-50 m.y.b.p. Subsequent fault movement and diagenesis on the fault plane lead to a situation in which the Halten Vest region was effectively sealed off from pressure let-off in a proximal direction towards the,East. This lead to seal failure in the Halten Vest region whilst in the normally pressured Halten region, pressure bleed-off towards the east continued, preserving oil m the structures. We exclude, in contrast to earlier published models by other workers, any quantitatively important contributions of light hydrocarbons (C2-C8) and heavier hydrocarbons (C15+) from the coal bearing Are Fm. to the presently reservoired hydrocarbon charges in these fields. This suggest the oil generative capability of the Spekk Fm. in deep basin depressions to be higher than often indicated from published models and we propose most condensates in the Haltenbanken region, apart from the 6406/7-1 condensate, to be evaporative condensates owing their existence to phase separation rather than to high maturity or an inferior kerogen quality.

• Storvoll, Vidar; Bjørlykke, Knut; Karlsen, Dag Arild & Saigal, Girish (2002). Porosity preservation in reservoir sandstones due to grain-coating illite: a study of the Jurassic Garn Formation from the Kristin and Lavrans fields, offshore Mid-Norway. Marine and Petroleum Geology. ISSN 0264-8172. 19, p. 767–781. Full text in Research Archive Show summary

  The Garn Formation is an important reservoir-sandstone in the Haltenbanken area. The Garn Formation from the Kristin field is deeply buried (4.6¿4.9 km) but displays higher porosity values compared to the general porosity trend in the region. In the Lavrans field the same formation is extensively quartz cemented with low porosity values despite its shallower depth (4.4¿4.5 km). Porosity is controlled by grain coatings preventing quartz overgrowth. It is well known that chlorite coatings inhibit quartz cementation, but our observations show that illite and illite/chlorite coatings can also be effective in preventing quartz precipitation. The grain-coating illite and chlorite in the studied wells may have developed from a smectitic precursor that formed from volcano-clastic material at lower temperatures. Bitumen covers the grains in many of the samples, but the bitumen formed too late to significantly affect quartz overgrowths and has not contributed to preservation of porosity.

• Pinturier-Geiss, Laurence; Méjanelleb, L.; Dale, Barrie & Karlsen, Dag Arild (2002). Lipids as indicators of eutrophication in marine coastal sediments. Journal of Microbiological Methods. ISSN 0167-7012. 48, p. 239–257. Full text in Research Archive Show summary

  Author Keywords: Lipids; Phospholipid ester-linked fatty acids; Eutrophication; Bacteria; Dinoflagellates; Long-chain diols and long-chain keto-ols; Oslofjord

• Storvoll, Vidar; Bjørlykke, Knut; Karlsen, Dag Arild & Saigal, Girish (2002). Porosity preservation in reservoir sandstones due to grain-coating illite: A study of the Jurassic Garn Formation from the Kristin and Lavrans Fields, Offshore Mid-Norway. Marine and Petroleum Geology. ISSN 0264-8172. p. 767–781. Full text in Research Archive Show summary

  The Garn Formation is an important reservoir sandstone in the Haltenbanken area. The Garn Formation from the Kristin Field is deeply buried (4.6-4.9 km) but displays higher porosity values compared to the general porosity trend in the region. In the Lavrans Field the same formation is extensively quartz cemented with low porosity values despite its shallower depth (4.4¿4.5 km). Porosity is controlled by grain coatings preventing quartz overgrowth. It is well known that chlorite coatings inhibit quartz cementation, but our observations show that illite and illite/chlorite coatings can also be effective in preventing quartz precipitation. The grain-coating illite and chlorite in the studied wells may have developed from a smectitic precursor that formed from volcano-clastic material at lower temperatures. Bitumen covers the grains in many of the samples, but the bitumen formed too late to significantly affect quartz overgrowths and has not contributed to preservation of porosity.

• Svensen, Henrik; Jamtveit, Bjørn; Banks, D.A. & Karlsen, Dag Arild (2001). Fluids and halogens at the diagenetic-metamorphic boundary: evidence from veins in continental basins, Western Norway. Geofluids. ISSN 1468-8115. 1, p. 53–70. Full text in Research Archive
• Breedveld, Gijs & Karlsen, Dag Arild (2000). Estimating the availability of polycyclic aromatic hydrocarbons for bioremediation of creosote contaminated soils. Applied Microbiology and Biotechnology. ISSN 0175-7598. 54, p. 255–261. Full text in Research Archive Show summary

  Bioremediation of soil contaminated by organic compounds can remove the contaminants to a large extent, but residual contamination levels may remain which are not or only slowly biodegraded. results indicate that both desporption and selective extraction measurements could aid the assessment of the feasability for bioremediation and identifying acceptable end-points.

• Bhullar, Abid Ghafoor; Karlsen, Dag Arild; Backer-Owe, Kristian; Tran, Ken Le & Skålnes, Eli (2000). Reservoir Characterization by a combined micro-extraction-micro thin-layer chromatography (Iatroscan) method: A calibration study with examples from the Norwegian North Sea. Journal of Petroleum Geology. ISSN 0141-6421. 23(2), p. 221–244. Full text in Research Archive Show summary

  well logging is used routinely to deliniate variations in physical properties of water, gas and oil zones in petroleum reservoirs. We demonstrate how added information about the hydrocarbon distribution, the filling history of the structure and identification of prime production zones for hydrocarbons can be obtained by rapid and cost effective methods.

• Bhullar, Abid Ghafoor; Karlsen, Dag Arild; Lacharpagne, J.C. & Holm, Kristine (1999). Reservoir screening using Iatroscan TLC-FID and identification of palaeo-oil zones, oil-water contacts, tar-mats and residual oil saturations in the Frøy and Rind petroleum accumulations. Journal of Petroleum Science and Engineering. ISSN 0920-4105. 23, p. 41–63. Full text in Research Archive
• Bhullar, Abid Ghafoor; Karlsen, Dag Arild; Backer-Owe, Kristian; Seland, R.T. & Tran, Ken Le (1999). Dating reservoir filling - a case history from the North Sea. Marine and Petroleum Geology. ISSN 0264-8172. 16, p. 581–603. Full text in Research Archive
• Bhullar, Abid Ghafoor; Karlsen, Dag Arild; Lacharpagne, J.C. & Holm, Kristine (1999). Reservoir screening using Iatroscan TLC-FID and identification of palaeo-oil zones, oil-water contacts, tar-mats and residual oil saturations in teh Frøy and Rind petroleum accumulations. Petroleum science and technology. ISSN 1091-6466. 23, p. 41–63. Full text in Research Archive Show summary

  The Iatroscan method is used for detection of a number of geologically relevant organic elements in reservoirs. Resudual oil sturation (ROS) and oil water contacts (OWCs) are determined with high accuracy in complex lithologies where more traditional methods have difficulties in producing good quality data points.

• Bhullar, Abid Ghafoor; Karlsen, Dag Arild; Backer-Owe, Kristian; Seland, R.T. & LeTran, K. (1999). Dating reservoir filling - a case history from the North Sea. Marine and Petroleum Geology. ISSN 0264-8172. 16, p. 581–603. Full text in Research Archive Show summary

  The Frøy oil field and the Rind discovery in the North Sea were investigated geochemically for the identification of oil families and their relation to the generative basins in region. The filling histories of the field - which differ dramatically - despite the close proximity of the structures - were discussed.

• Ashan, S. A.; Karlsen, Dag Arild; Mitchell, A.W. & Rothwell, N. (1998). Inter and intrafield hydrocarbons compositional variations in the Ula and the Gyda fields (Central Graben-North Sea) - Implications for understanding the controls of hydrocarbon distribution within and between these fields. Organic Geochemistry. ISSN 0146-6380. 29, p. 429–448. Full text in Research Archive Show summary

  A suite of 34 oil samples from the Central Graben area and in particular from the Ula and Gyda fields were investigated to evaluate genetic relationships between the oils, their organic facies signatures and their maturity. The oils represent in Ula represent a) the original oil distribution and b) the oil distribution after several years of production. This is the first study ever which has followed the oil distribution in a field over years of production and we have evaluated the degree of communication across faults. The Gyda Sourth Accumulation is proved to be independant of the Gyda field and regional implications for exploration in this region is discussed.

• Ahsan, A.; Karlsen, Dag Arild & Patience, R.L. (1997). Petroleum biodegradation in the Tertiary reservoirs of the North Sea. Marine and Petroleum Geology. ISSN 0264-8172. 14, p. 55–64. Full text in Research Archive Show summary

  Bidegradation of oil in reservoirs in the North Sea was investigated. The degree of biodegradation varies dramatically and is found to reflect basically the burial depth of the reservoirs i.e. the reservoir temperature and also the openness of the reservoir system or the reservoir sandstone "plumbing" system. Biodegradation reduces drmatically the price of the crude oil and it is important to be able to predict if undrilled resrvoirs will be degraded or not.

• Olstad, Richard; Bjørlykke, Knut & Karlsen, Dag Arild (1997). Pore water flow and petroleum migration in the Smørbukk Field area, Offshore mid-Norway. Hydrocarbon Seals: Importance for exploration and Production, NPF Special Publication. p. 201–207. Full text in Research Archive Show summary

  The paper discusses segmentation of the Smørbukk reservoir in relation to faults, lithology and diagenetic mineral reactions. Different hydrocarbon families are detected within Smørbukk and used to determine the degree of lateral and vertical compartmentalization of this field.

• Ettner, D.C.; Lindblom, S. & Karlsen, Dag Arild (1996). Identification and implications of light hydrocarbon fluid inclusions from the proterozoic Bidjovagge gold-copper deposits, Finnmark, Norway. Applied Geochemistry. ISSN 0883-2927. 11, p. 745–755. Full text in Research Archive Show summary

  Carbonic fluid inclsuions were observed in quartz-bearing veins at the Proterozoic Bidjovagge Au-Cu deposits within the Kautokeino greenstone belt in Norway. The paper discussed the occurences of gold in these deposits and their correlation to light hydrocarbons found in fluid inclusions. The origin of the light hydrocarbons seems to be co-genetic with the gold deposits.

• Karlsen, Dag Arild; Nyland, Bente; Flood, B.; Ohm, Sverre; Brekke, T. & Olsen, S. [Show all 7 contributors for this article] (1995). Petroleum Geochemistry af the Haltenbanken, Norwegian Continental Shelf. Geochemistry of Reservoirs. p. 203–256. Full text in Research Archive Show summary

  All petroleum accumulations in Haltenbanken have been investigated geochemically. Clear-cut systematic relationships between oil facies ang geographic locations are detected. The oils and condensates ahve all origin from the marine type II Spekk Fm. and condenstes are generated, not by high maturity, rather by phase fractionation during secondary migration.

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• Abay, Tesfamariam Berhane; Karlsen, Dag Arild; Olaussen, Snorre & Pedersen, Jon Halvard (2019). Organic Geochemistry of Petroleum in the Cambro-Ordovician Succession of Ny Friesland, Spitsbergen, Norway. Full text in Research Archive
• Wesenlund, Fredrik & Karlsen, Dag Arild (2017). The Petroleum Geochemistry of the Johan Sverdrup Field, Southern Utsira High, Norwegian North Sea. Full text in Research Archive
• Abay, Tesfamariam Berhane; Karlsen, Dag Arild; Pedersen, Jon Halvard & Olaussen, Snorre (2017). Middle Triassic Source Potential and Lateral Variation in Organic Facies, Southwestern Barents Sea and Svalbard. Full text in Research Archive
• Lerch, Benedikt; Karlsen, Dag Arild & Duggan, Deirdre (2015). Geochemical Characterization of Loppa High oils (SW-Barents Sea) and implications for regional petroleum systems. Full text in Research Archive
• Olaussen, Snorre; Abay, Tesfamariam Berhane; Karlsen, Dag Arild; Hammer, Øyvind & Pedersen, Jon Halvard (2014). Novel Results on Migrated Oil in several Svalbard out-crop samples. What does this tell us about the Petroleum Systems responsible for the Migrated Oils in these samples. Full text in Research Archive
• Abay, Tesfamariam Berhane; Karlsen, Dag Arild; Pedersen, Jon Halvard; Lerch, Benedikt & Backer-Owe, Kristian (2014). Regional Variation in the Triassic Organo-Facies signatures of the Barents Sea. Full text in Research Archive
• Abay, Tesfamariam Berhane; Karlsen, Dag Arild & Pedersen, Jon Halvard (2014). Source Rocks at Svalbard: An Overview of Jurassic and Triassic Formations and Comparison with Offshore Barents Sea Time Equivalent Source Rock Formations. Full text in Research Archive
• Lerch, Benedikt & Karlsen, Dag Arild (2014). Light Hydrocarbon Appraisal on Migration and Alteration Modes in Barents Sea Oils and Condensates - A Geochemical Approach to Improved Petroleum System Understanding. Full text in Research Archive
• Lerch, Benedikt; Karlsen, Dag Arild & Duggan, Deirdre (2014). Migration and Alteration Processes in Barents Sea Oils and Condensates - A Geochemical Approach to Improved Petroleum System Understanding. Full text in Research Archive
• Lerch, Benedikt; Karlsen, Dag Arild & Duggan, Deirdre (2014). The Light Hydrocarbon Paradox of the Barents Sea - Light Hydrocarbon Correlation- & Transformation Parameters in Barents Sea Oils and Condensates. Full text in Research Archive
• Abay, Tesfamariam Berhane; Karlsen, Dag Arild; Backer-Owe, Kristian & Ohm, Sverre Ekrene (2013). Geochemical comparison of oils from the Central Graben: with special emphasis on correlation and transformation of oils from the Embla Field. Full text in Research Archive
• Koeverden, Jan Hendrik; Karlsen, Dag Arild & Nakrem, Hans Arne (2009). Migrated hydrocarbons on Novaya Zemlya, Russian Arctic - a novel petroleum system for the Barents and Kara Sea regions? Full text in Research Archive
• Ohm, Sverre Ekrene & Karlsen, Dag Arild (2005). Gas expulsion from coals (Brent and Åre Fm NOCS);New proofs and understanding. Full text in Research Archive Show summary

  Gas composition and isotope values of gas liberated from coals on the Norwegian Continental Shelf (NOCS) by simple crushing have been analyzed. These values were compared to those from fluid inclusion gases. The fluid inclusions were extracted from sandstones in contact with the coals. The coal gas was found to be isotopically similar to that liberated from inclusions. The methane is very light with δ13C values in the range of -58 to -72‰. For ethane, propane and butane the values were heavier and more in agreement with anticipated values. The methane is isotopically very different from most of the gas discovered on the NOCS in which methane values generally fall in the range of -42 to -45‰. Most of the coal samples have a vitrinite reflectivity of 0.8 to 1% Ro. The inclusion samples contain dominantly methane (70 to 90%) while the coal gas is much wetter. The study shows that the examined coals have expelled biogenic gas: 1) over a temperature window where quartz overgrowth formation takes place (80-1200C), 2) in sufficient amounts to become trapped in inclusions and 3) over a sufficient time interval to become trapped. This suggests that volumes of biogenic produced methane have been expelled from the investigated coals at a surprisingly high temperature (depth of burial ~4000m) and that this light methane besides being trapped in inclusions also can migrate – potentially into commercial traps and mix with thermogenic high maturity gas – which is isotopically heavy and thereby skew the overall gas isotope values towards lighter values (values in the -45 to -55‰ range).

• Ohm, Sverre Ekrene & Karlsen, Dag Arild (2005). The Paleocene sandy Siri Fairway (2); an efficient 'pipeline' draining the prolific Central Graben. Full text in Research Archive Show summary

  Conclusions A common Paleo closure existed for the Siri-1 and Siri-2 reservoar. A regional tilt disturbed this closure and a new OWC was established, tentatively dated to Miocene. The Siri-2 oil opposed to Siri-1 and 3 is saturated and the accumulation has a gas cap and a tar mat at and above the OWC. This hints on a communication problem (no homogenization) between individual turbidite fans/sand lobes. It does as well suggest a possible recent pulse of hydrocarbons to Siri-2. If the GOR of the Siri-1 and 3 oils are real and not a result of phase fractionation and if this oil migrated in as a saturated phase this is modeled to have occurred when the reservoir/carrier was buried ca. 1000m more shallow. This was the case roughly 24 M.Y.b.p.. The tar mat in Siri-2 formed after the Tertiary regional tilt along the present OWC and could be a result of mixing of an original undersaturated fluid (comparable to Siri-1 and 3) with a recent saturated one. Sieving of asphaltenes in the carrier sands during migration of hydrocarbons in the more porous part of the carrier could as well lead to formation of a tar mat. A combination of these two mechanisms could as well be envisaged. All the analysed oils in the Siri Fairway in this study have an early mature signature. The source area in the Tail-End Graben presently expels late mature oil and gas. Consequently the Siri Fairway is believed no longer to drain this basin. The source rock (Farsund Fm) in the Søgne Basin has just entered the oil window and could maturity wise be responsible for some of the observed hydrocarbons. There is a significant amount of biogenic gas in Siri-1 and 3, less in Siri-2. This suggests that huge quantities of hydrocarbons never passed through the Siri Fairway, which also helps explain the low maturity of the oils. The possible lower quantities of biogenic gas in Siri-2 hints on more thermogenic hydrocarbon migrating through this part of the Fairway, supporting the formation of the observed tar mat. Possible fault movements along the Coffee Soil Fault during the time of regional tilting could have caused the connection between the Paleocene Siri Fairway sands and the Jurassic produced Tail-End Graben hydrocarbons to be cut. Alternatively influx of hydrocarbons to the Siri Fairway rests on vertical migration from Jurassic to Paleocene in the basin areas, possibly implying that the physiochemical properties of the chalk rules when it became a seal and prevented further migration through it. The Paleocene Tabita oil, located in the Tail-End Graben, has a significantly lower maturity (comparable to the Siri oils) than the underlying Jurassic Amalie oil, supporting that oil from the deep basin earlier migrated vertically, but that this now is prevented.

• Pedersen, Jon Halvard; Karlsen, Dag Arild; Lie, Jan Erik; Brunstad, Harald & Primio, Rolando di (2005). Petroleum Potential, Thermal Maturity and Organic Facies of Palaeozoic Sediments from the North Sea Region. Full text in Research Archive Show summary

  The Palaeozoic successions in the northern North Sea are not as well mapped and understood as younger strata in the North Sea sedimentary basins. This is due to great burial depths, but also because the Palaeozoic has been regarded as of low economic interest in this area. There are however Palaeozoic sediments with possible petroleum potential in both Norwegian and Danish wells in the northern North Sea. We also know that source rocks of Cambro-Silurian, Devonian, Carboniferous and Permian age are found in areas fringing the North Sea, i.e. in Norway, Denmark, Sweden, Poland, Germany, the Netherlands, in the UK and on East Greenland. In the Skagerrak Sea and northern North Sea, thick sequences of marine sediments most likely accumulated in Cambro-Silurian times. Additionally, shales, coals and mudstones of Devonian to Permian age may have been deposited in Palaeozoic half-grabens and N-S trending rift basins underlying the Upper Permian Zechstein evaporites. In this study, we investigate Palaeozoic sediments collected from wells and outcrops in the North Sea and adjacent areas. In specific, we focus on Cambro-Silurian, Carboniferous and Permian sediments, which may have petroleum source rock properties. In the northeastern North Sea and Norwegian-Danish Basin (NDB), Palaeozoic source rocks may be a crucial part of plays capped by thick Upper Permian evaporite layers.

• Alsger, Sager; Karlsen, Dag Arild & Pedersen, Jon Halvard (2005). Petroleum Geochemistry of the Goliath discovery compared to other fields and traps in the Hammerfest Basin. Full text in Research Archive Show summary

  The Goliath discovery which is located in the Hammerfest Basin near the Troms-Finnmark fault complex is particular for its size and its content of oil and the lack of gas, whilst other traps in the Hammerfest Basin largely contains gas/condensate and generally only thin oil rims.

• Heggsum-Hubred, Jørnar & Karlsen, Dag Arild (2005). THERMAL EFFECTS OF BASALTIC SILL EMPLACEMENT INTO SOURCE ROCKS ON MATURITY & HYDROCARBON GENERATION. Full text in Research Archive Show summary

  THERMAL EFFECTS OF BASALTIC SILL EMPLACEMENT INTO SOURCE ROCKS ON MATURITY & HYDROCARBON GENERATION Jørnar Heggsum Hubred1,2),Dag A. Karlsen1) and Sven Dahlgren3) 1) Department of Geosciences P.O.Box 1047, Blindern, N-0316 Oslo, Norway 2) jornar@geo.uio.no 3) Norwegian Petroleum Directorate, P.O.Box 600, N-4001 Stavanger, Norway Present address: County councils of Buskerud, Telemark and Vestfold, Svend Foynsgt. 9 Fylkeshuset, N-3110 Tønsberg, Norway In sedimentary basins sills have a tendency to become emplaced in litholgies of lower mechanical competence, like shales, which can possess source rock qualities. In this study we have been investigating the thermal effects of thick sills on sedimentary rock units at Svalbard, Norway. We believe this study to be directly relevant for sills in large scale sedimentary basins. If sills were emplaced in contact with the source rocks at great burial depth a "source rock on a hot plate" type of situation could arise with a temperature-heat history quite unlike that of small dykes in shallow, water-rich sediments. An additional effect could be related to a regional increase in heat flow if the sills are in a sense "symptoms" of massive ingenious activity as known from other regions. It is well proven that thin sills and dykes can locally mature source rocks, increase biomarker ratio in extractable compounds and at the same time cause systematic increases in kerogen maturity parameters. Since few organic geochemistry results on large scale sills have been published it was not clear to us if massive sills simply could be viewed as a upscalling phenomena of the smaller dyke and sill systems.. Samples were collected from eight different profiles with sills. The Triassic Botneheia black shale source rock formation, with dominantly marine kerogen, were collected from the hills of Botneheia (Central Spitsbergen), Teistberget (eastern Central Spitsbergen), Krefftberget and Høgrinden (Barentsøya Island). Samples were also collected from the Jurassic Janusfjellet black shale (with dominantly terrestrial kerogen) from Domen (eastern Central Spitsbergen) and the Wilhelmøya Island. Samples from identical black shale units in nearby sections not thermally affected by the sills were also collected and used for comparison. Organic petrographical descriptions, vitrinite reflectance, Rock Eval, TC and TOC were determined on all 170 samples, whereas metamorphic phase petrology, EOM, Iatroscan TLC-FID, GC-FID, GC-MS and isotopic studies of C and O (in carbonates, kerogen and extracts) were conducted on 48 selected samples. The vitrinite reflectance (%Ro) profiles show the typical inverted profile closer to the sills i.e. the vitrinite values are as low as 1.5 at 2m from a 23m thick sill, 5 at 5m, decreasing to 3.5 at 10 meters before reaching the background value of 0.8 at about 20m distance from the sill. However, no trends in biomarker maturity of the extracts could be detected over the same profile. These results were in the beginning difficult to understand but lead us to suggest that the generative process caused violent mobilization of water, at the same time as generation of light hydrocarbons took place, transporting these light hydrocarbons away. Low maturity biomarkers have at a later stage back diffused from the lower maturity, unaffected shales into the thermally affected shales following cooling of the intrusions. The composition of generated hydrocarbons extracted from the rock samples indicates that hydrocarbon generation by sills may be a less than perfect analogue for "normal" hydrocarbon generation in subsiding basins. Results from this study would not only be relevant for sill intruded sedimentary basins but would possibly also be relevant for deep water exploration e.g. the Atlantic volcanic margin were sediments have experienced increased heat flows due to magmatic underplating.

• Pedersen, Jon Halvard; Kristiansen, Trond & Karlsen, Dag Arild (2005). Degradation of oil in relation to the Barents Sea. Full text in Research Archive Show summary

  Degradation of oil in relation to the Barents Sea J. H. Pedersen1, T. Kristiansen2, D. A. Karlsen1, J. E. Lie3 & H. Brunstad3 1Department of Geosciences, University of Oslo, P.O. Box 1047 Blindern, N-0316 Oslo, Norway 2Department of Biology, University of Bergen, P. O. Box 7800, N-5020 Bergen, Norway 3RWE Dea Norge AS, P.O. Box 243 Skøyen, N-0213 Oslo, Norway Since 1965, over 900 petroleum exploration wells have been drilled in the Norwegian North Sea, while around 70 exploration wells has been drilled in the Barents Sea since 1980. New attention to the Barents Sea as a potential oil and gas province may result in several new exploration wells to be drilled in the near future. Major oil spills in the past have been related to transportation of oil, rather than from oil exploration activities. The biggest risk for oil spills in the Barents Sea is therefore probably leakage from oil tankers. Oil spilled on the sea surface will within hours change composition and properties due to physical and chemical processes, such as spreading, dispersion, evaporation, weathering, emulsification, water washing and oxidation. Wave action and temperature are key factors. Long term biological processes include break-down of oil by bacterial oxidation of petroleum. These processes altogether increase the viscosity and gravity of the spilled oil, due to removal of the light components in the oil. In this study we demonstrate how degradation alters the composition and properties of oil, and that some identifiable specific organic molecules are still contained in the oil residue even long time after the spill. These molecules may be used to identify the source of an oil spill.

• Pedersen, Jon Halvard & Karlsen, Dag Arild (2005). Maturity and organic facies of Mesozoic and Palaeozoic petroleum from off- and onshore Scandinavia. Full text in Research Archive Show summary

  Maturity and organic facies of Mesozoic and Palaeozoic petroleum from off- and onshore Scandinavia Pedersen, Jon H.1, Karlsen, Dag A.1, di Primio, Rolando2, Lie, Jan E.3 and Brunstad, Harald3 1)Department of Geosciences, University of Oslo, P.O. Box 1047 Blindern, N-0316 Oslo, Norway 2)GeoForschungsZentrum Potsdam, Telegrafenberg, D-14473 Potsdam, Germany 3)RWE Dea Norge AS, P.O. Box 243 Skøyen, N-0213 Oslo, Norway In Lower Palaeozoic times, large parts of the Scandinavian region of the NW Europe were covered by the Iapetus Ocean. Shales, mudstones and carbonates were deposited on the mainland of Scandinavia, and in offshore areas east, south and west of the Scandinavian mainland. Some of these sediments, like the Upper Cambrian – Lower Ordovician Alum Shale, have certainly generated petroleum. On- and offshore oil and gas fields in the Baltic countries Latvia and Lithuania are sourced from Cambrian, Ordovician and Silurian marine shales. In Scandinavia, insoluble bitumen, oil stains and oils in inclusions found on the Scandinavian onshore prove that Lower Palaeozoic petroleum systems have been active in this region. Insoluble bitumen found in Upper Palaeozoic rocks in the Norwegian North Sea suggest that Lower Palaeozoic petroleum also have been present in the North Sea region. This study presents an evaluation of Palaeozoic and Mesozoic source rocks and oil stains from Norway, Sweden, Scotland and Spitsbergen. We use established organic geochemical methods to characterise marine and lacustrine samples in order to better understand the thermal maturity and organic facies of Palaeozoic source rocks and petroleum in the Scandinavian on- and offshore region.

• Pedersen, Jon Halvard & Karlsen, Dag Arild (2005). Source Rocks and Petroleum of the Norwegian Barents Sea. Full text in Research Archive
• Svensen, Henrik; Karlsen, Dag Arild & Banks, DA (2004). Seep geochemistry and origin of petroleum from the Salton Sea Geothermal System, California, USA. Geochimica et Cosmochimica Acta. ISSN 0016-7037. 68, p. A266–A266. Full text in Research Archive
• Ohm, Sverre Ekrene & Karlsen, Dag Arild (2004). The Paleocene Sandy Siri Fairway; An efficient 'pipeline' draining the prolofic Danish Central Graben? Full text in Research Archive Show summary

  A new petroleum charge model is presented for the sandy, Paleocene channel system known as the Siri Fairway. The Siri Fairway straddles the platform area along the Danish � Norwegian offshore border and stretches from the Norwegian paleo-shelf until the Tail-End Graben and Søgne Basin (within the Central Graben). The closest known expelling source rocks are located in the Central Graben. The discoveries of the Siri Field and later the Cecilie and the Nini Fields prove that petroleum has migrated through the sandy Paleocene deposits for distances up to 70 km. If the Siri Fairway acts as a pipeline transporting petroleum from the Graben onto the Platform area, the chemical composition of the petroleum discovered in the Graben area and within the Fairway itself should be similar. This study shows that this is not the case. The oils in the Graben area have a very mature signature whilst the oils from the Siri have an early mature signature and are mixed with in-situ derived biogenic gas suggesting Siri to represent a �dead-end for migration�. This biogenic gas signature would have been completely obliterated were the petroleum continuously introduced to the Fairway. We therefore suggest that hydrocarbon charging to the Fairway for some reason came to a halt before the source rocks in the Graben entered the main and late part of the oil window. The consequence for the Siri Fairway is that limited charging has occurred. The chemical composition of the oils in the Siri Field also led us to suggest that the Fairway has been charged from two different sub-basins with different subsidence history. The Siri-2 structure is in this context interpreted to have been initially filled with the same oil as found today in Siri-1 and Siri-3, but that it was later partly displaced with oil from a shallower buried sub-basin. The Siri Fairway consists of sands deposited as turbidites through Late Paleocene. The deposit consists of stacked interfingering fans. These could be completely, or partly covered by layers of fine-grained clays reflecting the time lag between deposition of individual fans. Long distance migration is proven through this deposit. However, connectivity and thus migration between individual fans could represent a problem depending on the local presence and continuity of the clay. The number of dry wells drilled in the Fairway and the �dead-end� character of the analysed oils indicates that migration routes are difficult to predict.

• Pedersen, Jon Halvard; Karlsen, Dag Arild; Primio, Rolando di; Lie, Jan Erik & Brunstad, Harald (2004). Evaluation of extracts and pyrolysates from Palaeozoic sediments from the North Sea region. Full text in Research Archive Show summary

  The Palaeozoic successions in the northern North Sea is not mapped and understood as well as younger strata in the North Sea sedimentary record. This is due to great burial depths, but also because the Palaeozoic has been regarded as of low economic interest in this area. In this project we investigate Palaeozoic sediments collected from wells and outcrops in the North Sea and adjacent areas. In specific, we focus on Cambro � Silurian, Carboniferous and Permian sediments, which may have petroleum source rock properties. We hope that this study will increase our understanding of the distribution, organic facies and thermal maturity of Palaeozoic sediments in the northern North Sea. We also believe that this work may help us to better evaluate the significance of Palaeozoic petroleum systems in the northern North Sea and Norwegian Danish Basin.

• Pedersen, Jon Halvard; Karlsen, Dag Arild; Lie, Jan Erik & Brunstad, Harald (2004). Petroleum potential and thermal maturity of Palaeozoic sediments from the North Sea region. Full text in Research Archive Show summary

  The dominating oil and gas source rocks in the northern North Sea are of Mesozoic age. Especially important are the Upper Jurassic marine clays of the Kimmeridge Clay Formation, deposited in the Jurassic Central and Viking Graben rift structures. There are however Palaeozoic sediments with possible petroleum potential in both Norwegian and Danish wells in the northern North Sea. We also know that source rocks of Cambro-Silurian, Devonian, Carboniferous and Permian age are found in areas fringing the North Sea, i.e. in Norway, Denmark, Sweden, Poland, Germany, the Netherlands, in the UK and on East Greenland. In the northern North Sea, thick sequences of marine sediments most likely accumulated in Cambro-Silurian times. Additionally, shales, coals and mudstones of Devonian to Permian age may have been deposited in half-grabens and N-S trending rift basins underlying the Upper Permian Zechstein evaporites. In this study, we investigate the kerogen types, petroleum potential and thermal maturity of some of these Palaeozoic sediments, and look for traces of Palaeozoic petroleum in reservoir rocks in the North Sea. In the northeastern North Sea, Palaeozoic source rocks may be a crucial part of plays capped by thick Upper Permian evaporite layers.

• Pedersen, Jon Halvard; Karlsen, Dag Arild; Lie, Jan Erik & Brunstad, Harald (2004). Atypical source rocks and petroleums of the Norwegian Continental Shelf. Full text in Research Archive Show summary

  ***This poster won the Best Student Poster Award at the 21st Annual Meeting of TSOP , Sydney, 26 September - 1 October, 2004*** In one of the world�s most important oil and gas provinces, the North Sea and NE Atlantic margin of the NW Europe, the dominating source rock is the Upper Jurassic marine Kimmeridge Clay. Up to 1 km of this excellent source rock was deposited in extensive Jurassic rift systems developed along almost the entire Norwegian continental shel,f from the Central Graben in the south to the Barents Sea in the north. 21 hydrocarbon samples, including some highly atypical oils, were analysed geochemically to determine their source rock facies and maturity relationships. While most of the samples are from the Norwegian Offshore Continental Shelf (NOCS), oils and condensates from onshore Scandinavia are also analysed, debated and attempted interpreted in relation to source facies and thermal maturity. It was hoped that this work might help in providing evidences that the NOCS and neighbouring regions may contain additional source rocks besides the widespread Upper Jurassic Kimmeridge Clay formation and its equivalents. Another goal was to seek out and point to potential atypical petroleums and bitumens on and offshore Norway and Fennoscandia, by using organic geochemical analytical procedures and parameters obtained from these. The molecular parameters are used to illustrate the differences between the typical and atypical petroleums, and to show the variation in NOCS source rock depositional facies and maturity.

• Skeie, Jon Erik; Karlsen, Dag Arild; di-Primio, Rolando; Backer-Owe, Kristian; Lie, Jan Erik & Brunstad, Harald [Show all 8 contributors for this article] (2003). How an integrated study combining basin modelling, geochemical data and petroleum properties can constrain the timing of petroleum migration and evolution of overpressures in sedimentary basins. An example utilizing the distribution of petroleum in Mesozoic sediments in the Haltenbanken area, offshore Norway. Full text in Research Archive
• Skeie, Jon Erik; di-Primio, Rolando & Karlsen, Dag Arild (2003). An integrated basin modelling study applying asphaltene kinetics from reservoired petroleum in the Snorre Area, Northern North Sea. Full text in Research Archive
• Skeie, Jon Erik; Karlsen, Dag Arild & di-Primio, Rolando (2002). The release of petroleum from source rocks; implications for basin modelling. Full text in Research Archive
• Storvoll, Vidar; Bjørlykke, Knut; Karlsen, Dag Arild & Girish, Saigal (2000). Diagenesis and reservoir quality in the Garn Formation from deep wells in the Halten Area. Full text in Research Archive Show summary

  Although we would expect extensive quartz cementation and low porosity and permeability values in sandstones buried below 4 km, it is sometimes found that the reservoir quality in the Garn Formation is remarkably good. This study focuses on the diagenetic differences in the Kristin and Lavrans fields and the variations in the reservoir properties. The effect of chlorite coatings are well known from several publications, but this study suggests that illite- and illite/chlorite-coatings also have been most effective in preventing precipitation of quartz. Many of the studied samples contain a more or less continuos fluorescent coatings around the detrial sand grains. A green and "fibrous" coating has been observed in the samples from one of the studied wells, but it is completely absent in the other wells from this area. We conclude that it is mainly the illite- and illite/chlorite-coatings that are responsible for the good reservoir quality in the Garn Formation. The occurance of the fluorescent coatings, the green "fibrous" coatings and the black "asphalt-rich" material found in the pores does not seem to have had any positive influence with respect to the reservoir quality in the Garn Formation from the studied wells. The absence of the clay coatings in the extensively cemented wells is most likely due to variations in the depositional environment.

• Pinturier-Geiss, Laurence; Dale, Barrie; Abdullah, Mohamed I & Karlsen, Dag Arild (2000). Lipid composition and cultural eutrophication in the oslofjord (Norway). Full text in Research Archive Show summary

  The aim of this work is to evaluate variations in chemical signals extracted from sediments as a mean of tracing out the development of eutrophication, and to compare this with potential parallel variations in the dinocyst assemblages. The lipid fraction of the organic matter was analysed by TLC-FID, GC-FID and GC-MS.Particular attention was given to the polar fraction (phospholipids, glycolipids) and hydrocarbons. The down-core distribution of lipids is strongly correlated with the dinocyst signal.The highest concentrations as well as a marked increase in the HC concentration are observed during the period of intensive eutrophication.The molecular composition of HC and fatty acid methyl esters of the polar fraction enables identification of the predominant source of the Om: bacteria and dinocyst.

• Karlsen, Dag Arild; Backer-Owe, Kristian & Helland, Reidar (2000). Defining dynamics of hydrocarbon zones in reservoir strata using petroleum inclusions distribution and geochemistry. Full text in Research Archive Show summary

  Oil reservoir compartmentalisation is deliniated using geochemical tools and examples from 5 wells in the Gullfaks Sør and the nearby Gullfaks Gamma structure illustrate this approach. The results obtaine does not only help in optimizing field production but do also provide data relevant for understanding better basin scale hydocarbon migration patters. Thus, the methods we illustrate have a clear impact for reservoir production and exploration for hydrocarbon resources.

• Karlsen, Dag Arild; Dahlgren, Sven; Jamtveit, Bjørn & Kjærnet, Torfinn (2000). Thermal effects of basaltic sill emplacement in source rocks for maturation & hydrocarbon generation. Full text in Research Archive Show summary

  Emplacement of basaltic sills into sedimentary strata may represent a heat source for hydrocarbon generation from shallow source rocks. Mathematical modeling of this phenomena and studies of thin intrusive boddies suggest that the heat impact can be favourably for oil generation. Our studies of real rock systems from Svalbard and nearby islands do, however, suggest the heatimpact to be destructive for oil generation generation.

• Karlsen, Dag Arild; Backer-Owe, Kristian; Bjørlykke, Knut; Berge, Kari & Schaefer, Rainer G. (2000). Faults, Oil Migration Overpressure and Dismigration - Dating Events. A case History from the Halten Vest High Pressure Region, Offshore Norway. Full text in Research Archive Show summary

  Geochemical evidences from core extracts and fluid inclusions in diagenetic mineral is used to shed light on the overpressure development and palaeo-leakage from currently dry structures in the Haltenbanken area. A new model is presented for the role of faults during hydrocarbon migration and for determining the time for overpressure development

• Karlsen, Dag Arild (2000). Primary migration of hydrocarbons and hydrocarbon generation. Full text in Research Archive Show summary

  Hydrocarbon generation from organic matter in shales and carbonates occur by thermocatalytic cracking of a polymer called kerogen. The thermal response of the kerogen during progresive burial of the source rocks will produce specific types of petroleum (oil and gas) depending on the type of organic matter making up the kerogen, the degree of anoxic conditions in the palaeo-depositional environment, the termal profile, and the organization of the organic matter in the source rocks. Oil moves out of good quality source rocks as a singel phase whilst diffusive type mechanisms operate in lean source rocks.

• Brekke, Trond; Karlsen, Dag Arild; Bhullar, Abid Ghafoor; Holm, Kristine; Melberg, Nina & Kvinnsland, Steinar R. (2000). Variability in organic extracts from cores from the Frøy reservoir. Full text in Research Archive Show summary

  Principal component analysis of organic core extracts from the Frøy oil field reservoir section was used to detail the different potential origins of the organic matter from i.e. to isolate contributions from in-situ generated bitumen from migrated oil from distant source rocks. In-situ contributions can greatly mask the proper origin of migrated oil.

• Karlsen, Dag Arild; Backer-Owe, Kristian & Helland, Reidar (2000). Defining Dynamics of Hydrocarbon Zones in reservoir Strata Using petroleum Inclusion - distributions and Geochemistry - Elucidating petroleum migration into the Gullfaks Sør Field and the nearby Gullfaks Gamma Structure, Norwegian Continental Shelf. Full text in Research Archive Show summary

  Examination of core extracts, drill stem tests and fluorescent petroleum inclusions in 5 wells from the Gullfaks Sør and the Gullfaks Gamma structure has showed that these structures have experienced dramatic shift in their gas/oil zones during filling. The structures closest to the filling direction have experienced larger shifts in the contacts as the field filled. The presently gas filled Gamma structure is proved to ahve ealier contained oil. We illustrate how geochemical data are used to construct a filling direction model for the Gullfaks Sør and the Gullfaks Gamma structure.

• Khoshbakht, Payam; Karlsen, Dag Arild; Backer-Owe, Kristian & Ohm, Sverre (2000). Variations in source facies and matuirty in Central Garaben Oils, Norwegian continental Shelf. Full text in Research Archive Show summary

  The poster describes detailed geochemical characteristics of oils in the Central Graben Area. Clear trends in terms of increasing terrestrial contributions to oils from more proximal positions in the basin is demonstrated and oils are grouped into families.

• Karlsen, Dag Arild; Backer-Owe, Kristian; Bjørlykke, Knut; Scjaefer., R.G.; Bhullar, Abid Ghafoor & Angard, K. [Show all 11 contributors for this article] (1999). Faults and Oil Migration in the Halten Vest High Pressure and Haltenbanken Normal Pressure Regimes, Offshore Norway. Full text in Research Archive
• Bhullar, Abid Ghafoor; Karlsen, Dag Arild; Holm, Kristine & Primio, R. de (1999). "Characterizationn of petroleum fluids in the Frøy Fields and Rind Discovery, NOCS, using petroleum geochemical, fluid inclusion and PVT data. Poster presentation at AAPG Hedberg Conference, Multi-Dimentional Basin Modeling.". Full text in Research Archive
• Bhullar, Abid Ghafoor; Karlsen, Dag Arild; Johansen, H.; Holm, Kristine & Seland, R.T. (1999). "The filling history of the Rind and Frøy petroleum accumulations, North Sea - Application of fluid inclusions, core extracts and oils to geological dating". Full text in Research Archive
• Bhullar, Abid Ghafoor; Karlsen, Dag Arild; Johansen, H.; Backer-Owe, Kristian; Holm, Kristine & Primio, R. de (1999). "The filling history of the Rind and Froy petroleum accumulations, North Sea, using petroleum geochemical, fluid inclusion and PVT data to geological dating". Full text in Research Archive
• Bhullar, Abid Ghafoor; Karlsen, Dag Arild; Holm, Kristine & Lacharpagne, J.C. (1999). "Filling history and petroleum characterisation of the Frøy Field and Rind discovery, Nocs, using petroleum geochemical, fluid inclusion and PVT data.". Full text in Research Archive
• Karlsen, Dag Arild; Backer-Owe, Kristian; Bjørlykke, Knut; Angard, K.; Steinhoff, Inga & Olstad, Richard [Show all 9 contributors for this article] (1999). Differential pressure across a fault zone and oil migration - an ezample from Haltenbanken offshore, Norway. Full text in Research Archive
• Karlsen, Dag Arild; Dahlgren, Sven; Jamtveit, Bjørn & Kjærnet, Torfinn (1999). Thermal effects of basaltic sill emplacement in source rocks maturation and hydrocarbon generation. Full text in Research Archive
• Karlsen, Dag Arild; Dahlgren, Sven; Jamtveit, Bjørn & Kjærnet, Torfinn (1999). Thermal effects of basaltic sill emplacement in source rocks for maturation and hydrocarbon generation. Full text in Research Archive

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