Geology and petroleum potential of Hope and Selawik Basins, offshore northwestern Alaska

John Decker, Mark Robinson, James G. Clough, William M. Lyle

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

The Hope and Selawik Basins are predominantly offshore depocenters of Tertiary age located in less than 50 m of water in the epicontinental Chukchi Sea. The United States portion of the Hope Basin lies between the Kotzebue Arch to the south and the Cape Krusenstern-Cape Lisburne shoreline and Herald Arch to the northeast. The Selawik Basin is located south of the Kobuk fault zone-Kotzebue Arch structural discontinuity, entirely within Kotzebue Sound and adjacent onshore lowlands. Both the Hope and Selawik Basins coincide with gravity lows that help define the margins of the main depocenters. The most likely petroleum reservoir in the Hope and Selawik Basins is the Neogene section. Order-of-magnitude calculations indicate that Hope Basin contains about 70,000 km3 and Selawik Basin about 15,000 km3 of Neogene sediment with an estimated average porosity of about 15%. Thermal maturation levels within the oil window are predicted to occur in both basins between 2500 and 3300 m. Small- to moderate-sized structural and stratigraphic traps can be expected in extensional basins of this type. However, the volume of high-organic-carbon source rock within the Neogene deposits is extremely low, and there is no evidence that oil or gas generation has ever occurred. Pre-Tertiary strata around Kotzebue Sound are thermally overmature and have probably been so since pre-Neogene time. Little is known about the source rock potential of Paleogene rocks. The Paleocene strata at Chicago Creek were deposited in a nonmarine environment and contain a high percentage of organic carbon in the form of coal. The coal is lignitic and has not reached the grade of subbituminous-C. Under the conditions in which Paleogene deposits are likely to occur in Hope and Selawik Basins, these deposits could produce gas or oil.

Original languageEnglish (US)
Pages (from-to)1-18
Number of pages18
JournalMarine Geology
Volume90
Issue number1-2
DOIs
StatePublished - 1989
Externally publishedYes

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Petroleum
Arches
Geology
geology
crude oil
Oils
Deposits
Coal
Rocks
petroleum
Organic carbon
Gases
basin
Acoustic waves
Petroleum reservoirs
Neogene
arches
arch
Gravitation
Sediments

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geology
  • Geophysics

Cite this

Geology and petroleum potential of Hope and Selawik Basins, offshore northwestern Alaska. / Decker, John; Robinson, Mark; Clough, James G.; Lyle, William M.

In: Marine Geology, Vol. 90, No. 1-2, 1989, p. 1-18.

Research output: Contribution to journalArticle

Decker, John ; Robinson, Mark ; Clough, James G. ; Lyle, William M. / Geology and petroleum potential of Hope and Selawik Basins, offshore northwestern Alaska. In: Marine Geology. 1989 ; Vol. 90, No. 1-2. pp. 1-18.
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abstract = "The Hope and Selawik Basins are predominantly offshore depocenters of Tertiary age located in less than 50 m of water in the epicontinental Chukchi Sea. The United States portion of the Hope Basin lies between the Kotzebue Arch to the south and the Cape Krusenstern-Cape Lisburne shoreline and Herald Arch to the northeast. The Selawik Basin is located south of the Kobuk fault zone-Kotzebue Arch structural discontinuity, entirely within Kotzebue Sound and adjacent onshore lowlands. Both the Hope and Selawik Basins coincide with gravity lows that help define the margins of the main depocenters. The most likely petroleum reservoir in the Hope and Selawik Basins is the Neogene section. Order-of-magnitude calculations indicate that Hope Basin contains about 70,000 km3 and Selawik Basin about 15,000 km3 of Neogene sediment with an estimated average porosity of about 15{\%}. Thermal maturation levels within the oil window are predicted to occur in both basins between 2500 and 3300 m. Small- to moderate-sized structural and stratigraphic traps can be expected in extensional basins of this type. However, the volume of high-organic-carbon source rock within the Neogene deposits is extremely low, and there is no evidence that oil or gas generation has ever occurred. Pre-Tertiary strata around Kotzebue Sound are thermally overmature and have probably been so since pre-Neogene time. Little is known about the source rock potential of Paleogene rocks. The Paleocene strata at Chicago Creek were deposited in a nonmarine environment and contain a high percentage of organic carbon in the form of coal. The coal is lignitic and has not reached the grade of subbituminous-C. Under the conditions in which Paleogene deposits are likely to occur in Hope and Selawik Basins, these deposits could produce gas or oil.",
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