Abstract A total of 143 sedimentary successions that contain, or may be prospective for, hydrocarbons were identified in the Arctic Region north of 58–64°N and mapped in four quadrants at a scale of 1:11 000 000. Eighteen of these successions (12.6%) occur in the Arctic Ocean Basin, 25 (17.5%) in the passive and sheared continental margins of the Arctic Basin and 100 (70.0%) on the Circum-Arctic continents of which one (<1%) lies in the active margin of the Pacific Rim. Each succession was assigned to one of 13 tectono-stratigraphic and morphologic classes and coloured accordingly on the map. The thickness of each succession and that of any underlying sedimentary section down to economic basement, where known, are shown on the map by isopachs. Major structural or tectonic features associated with the creation of the successions, or with the enhancement or degradation of their hydrocarbon potential, are also shown. Forty-four (30.8%) of the successions are known to contain hydrocarbon accumulations, 64 (44.8%) are sufficiently thick to have generated hydrocarbons and 35 (24.5%) may be too thin to be prospective.

Abstract The US Geological Survey recently assessed the potential for undiscovered conventional petroleum in the Arctic. Using a new map compilation of sedimentary elements, the area north of the Arctic Circle was subdivided into 70 assessment units, 48 of which were quantitatively assessed. The Circum-Arctic Resource Appraisal (CARA) was a geologically based, probabilistic study that relied mainly on burial history analysis and analogue modelling to estimate sizes and numbers of undiscovered oil and gas accumulations. The results of the CARA suggest the Arctic is gas-prone with an estimated 770–2990 trillion cubic feet of undiscovered conventional natural gas, most of which is in Russian territory. On an energy-equivalent basis, the quantity of natural gas is more than three times the quantity of oil and the largest undiscovered gas field is expected to be about 10 times the size of the largest undiscovered oil field. In addition to gas, the gas accumulations may contain an estimated 39 billion barrels of liquids. The South Kara Sea is the most prospective gas assessment unit, but giant gas fields containing more than 6 trillion cubic feet of recoverable gas are possible at a 50% chance in 10 assessment units. Sixty per cent of the estimated undiscovered oil resource is in just six assessment units, of which the Alaska Platform, with 31% of the resource, is the most prospective. Overall, the Arctic is estimated to contain between 44 and 157 billion barrels of recoverable oil. Billion barrel oil fields are possible at a 50% chance in seven assessment units. Undiscovered oil resources could be significant to the Arctic nations, but are probably not sufficient to shift the world oil balance away from the Middle East.

Abstract Petroleum system case studies provide an important link in understanding the petroleum system concept. Petroleum system case studies from different petroleum provinces of the world demonstrate practical problems that are typical of a petroleum system investigation. Well-documented case studies provide not only an understanding of the present-day distribution of hydrocarbons but also the basis to evaluate petroleum exploration risk in a play or prospect and to carryout petroleum research effectively. The case studies in the next two units describe and characterize 25 petroleum systems. Some studies address the migration of hydrocarbons from the pod of active source rock to the trap and show the difficulty of determining not only the hydrocarbon migration path but also the loss of petroleum during migration. The case studies also address generation-accumulation efficiency and size so that conclusions can be drawn as to what essential elements and processes most affect efficiency and size. This overview shows that the most prolific petroleum system is not necessarily the most efficient. By comparing several petroleum systems on either an efficiency or size scale and then comparing the essential elements and processes of each system, a general impression is gained of how each system functions.