Geochemical characterization of a tar mat in the Oseberg field Norwegian sector, north sea

Dahl, Birger; Speers, G. C.

doi:10.1016/0146-6380(86)90053-7

Cited by 42 publications

(18 citation statements)

References 4 publications

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“…Water washing and biodegradation often occur together, in which case the effects from the later obscure that from the former (Waples, 1985). It has also been described that this association results in the formation of tar mats, which are precipitation of asphaltenes near the oil-water contact (Dahl and Speers, 1986). However, Speers (1985, 1986) concluded that deasphalting and minor water washing, rather than biodegradation, formed the tar mats found in part of the Oseberg Field, North Sea.…”

Section: Basinal/climatic Sense and In Relation To The Water Fluxes Smentioning

confidence: 99%

“…Dahl and Speers, 1986;Karlsen et al, 1995;Leythaeuser and Rückheim, 1989;Tissot and Welte, 1984). A number of studies, devoted to understanding the reasons and consequences of diversities in petroleum composition, have already been undertaken long ago (Bailey et al, 1973a;Bailey et al, 1973b;Dahl and Speers, 1986;Espach and Fry, 1951;Evans et al, 1971;Hirschberg, 1988;Hunt, 1979;Justwan and Dahl, 2005;Karlsen et al, 1995;Karlsen and Skeie, 2006;Milner et al, 1977;Sage and Lacey, 1939;Tissot and Welte, 1984;Tyson, 1995). These studies have revealed that the factors that cause heterogeneities in petroleum composition in reservoirs can roughly be related to 1) variations in source rock organic facies and source rock maturity and 2) secondary alteration processes.…”

Section: 2mentioning

confidence: 99%

“…Significant compositional changes, related to biodegradation, are thought to occur near oil water contacts, where the bacteria gain easy access to nutrients and free oxygen (Dahl and Speers, 1986;Head et al, 2003). Biodegradation near the oil water contact leads to accumulation of a partly degraded residue as the reservoir is filling.…”

Section: Biodegradation and Water Washingmentioning

confidence: 99%

“…We concluded that the semi-solid bitumen from the palaeo-oil may have effectively filled the pore space and close pore-throats to act as flow barriers, decreasing the permeability of the reservoir and reducing the water drive efficiency (Dahl and Speers, 1986). This may imply that the Embla reservoir is vertically compartmentalized.…”

mentioning

confidence: 99%

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Thermal maturity, hydrocarbon potential and kerogen type of some Triassic–Lower Cretaceous sediments from the SW Barents Sea and Svalbard

Abay

Karlsen

Pedersen

et al. 2017

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Rock-Eval and total organic carbon (TOC) analyses of 144 samples representing Triassic–Lower Cretaceous intervals from the SW Barents Sea (the Svalis Dome, the Nordkapp and Hammerfest basins, and the Bjarmeland Platform) and Svalbard demonstrate lateral variations in source rock properties. Good to excellent source rocks are present in the Lower–Middle Triassic Botneheia and Steinkobbe, and Upper Jurassic Hekkingen formations, 1 – 7 wt% and 6 – 19 wt% TOC, respectively. Hydrogen indices of 298 – 609 mg HC/g TOC in the Botneheia Formation from Svalbard, and 197 – 540 mg HC/g TOC in the Steinkobbe Formation of Svalis Dome suggest Type II (oil-prone) and Type II/III (oil/gas-prone) kerogens, respectively. The Kobbe Formation (Botneheia/Steinkobbe-equivalent) is organic-lean and generally gas-prone (Type III kerogen) on the Bjarmeland Platform and in the Nordkapp Basin, and is a good source rock with Type III/II kerogen in the Hammerfest Basin. In the investigated wells, the Hekkingen Formation is more oil-prone on the Bjarmeland Platform than in the Nordkapp Basin, while Lower Cretaceous samples have poor potential for oil. Upper Triassic samples show potential mainly for gas; however, coal/coaly-shale samples in well 7430/07-U-01 (Bjarmeland Platform) are oil/gas-prone. Most samples analysed are immature to early mature; thus, the variation in petroleum potential and kerogen type is a function of organic facies rather than maturity levels.

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Section: Basinal/climatic Sense and In Relation To The Water Fluxes Smentioning

confidence: 99%

Section: 2mentioning

confidence: 99%

Section: Biodegradation and Water Washingmentioning

confidence: 99%

mentioning

confidence: 99%

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Thermal maturity, hydrocarbon potential and kerogen type of some Triassic–Lower Cretaceous sediments from the SW Barents Sea and Svalbard

Abay

Karlsen

Pedersen

et al. 2017

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“…Since the 1990s, great progress has been made in the study on solid reservoir bitumen [14][15][16][17][18][19][20] . The bitumen related with paleo-oil reservoirs can be generated by reservoir degradation [21,22] , oil cracking [23][24][25] , bitumen tar formed by hydrocarbons charged at different stages [26][27][28] and gas invasion bitumen [29,30] .…”

Section: Bitumen In Paleo-oil Reservoirs Being Pyrobitumen Generated mentioning

confidence: 99%

Geochemical features and genesis of the natural gas and bitumen in paleo-oil reservoirs of Nanpanjiang Basin, China

Zhao

Zhang

Zhao

et al. 2007

Sci. China Ser. D-Earth Sci.

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Bitumen from the Nanpanjiang Basin occurs mainly in the Middle Devonian and Upper Permian reef limestone paleo-oil reservoirs and reserves primarily in holes and fractures and secondarily in minor matrix pores and bio-cavities. N 2 is the main component of the natural gas and is often associated with pyrobitumen in paleo-oil reservoirs. The present study shows that the bitumen in paleo-oil reservoirs was sourced from the Middle Devonian argillaceous source rock and belongs to pyrobitumen by crude oil cracking under high temperature and pressure. But the natural gas with high content of N 2 is neither an oil-cracked gas nor a coal-formed gas generated from the Upper Permian Longtan Formation source rock, instead it is a kerogen-cracked gas generated at the late stage from the Middle Devonian argillaceous source rock. The crude oil in paleo-oil reservoirs completely cracked into pyrobitumen and methane gas by the agency of hugely thick Triassic deposits. After that, the abnormal high pressure of methane gas reservoirs was completely destroyed due to the erosion of 2000--4500-m-thick Triassic strata. But the kerogen-cracked gas with normal pressure was preserved under the relatively sealed condition and became the main body of the gas shows.source rocks, paleo-oil reservoir, pyrobitumen, kerogen-cracked gas, Nanpanjiang Basin

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Discovery of tar mats in terrestrial gas-condensate reservoirs and its geological significance

Zhang¹

1997

Chin.Sci.Bull.

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Geochemical characterization of a tar mat in the Oseberg field Norwegian sector, north sea

Cited by 42 publications

References 4 publications

Thermal maturity, hydrocarbon potential and kerogen type of some Triassic–Lower Cretaceous sediments from the SW Barents Sea and Svalbard

Thermal maturity, hydrocarbon potential and kerogen type of some Triassic–Lower Cretaceous sediments from the SW Barents Sea and Svalbard

Geochemical features and genesis of the natural gas and bitumen in paleo-oil reservoirs of Nanpanjiang Basin, China

Discovery of tar mats in terrestrial gas-condensate reservoirs and its geological significance

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