Abstract The US Geological Survey (USGS) recently assessed the potential for undiscovered oil and gas resources of the East Barents Basins and Novaya Zemlya Basins and Admiralty Arch Provinces as part of the USGS Circum-Arctic Resource Appraisal. These two provinces are located NE of Scandinavia and the northwestern Russian Federation, on the Barents Sea Shelf between Novaya Zemlya to the east and the Barents Platform to the west. Three assessment units (AUs) were defined in the East Barents Basins for this study – Kolguyev Terrace Assessment Unit (AU), South Barents Basin and Ludlov Saddle AU, and North Barents Basin AU. A fourth, defined as Novaya Zemlya Basins and Admiralty Arch AU, is coincident with the Novaya Zemlya basins and Admiralty Arch Province. These AUs, all lying north of the Arctic Circle, were assessed for undiscovered, technically recoverable resources resulting in total estimated mean volumes of approximately 7.4 billion barrels of crude oil, 318 trillion cubic feet of natural gas and 1.4 billion barrels of natural gas liquids.

Abstract The Siberian Craton consists of crystalline rocks and superimposed Precambrian sedimentary rocks deposited in rift basins. Palaeozoic rocks, mainly carbonates, were deposited along the margins of the craton to form an outwardly younger concentric pattern that underlies an outward-thickening Mesozoic sedimentary section. The north and east margins of the Siberian Craton subsequently became foreland basins created by compressional deformation during collision with other tectonic plates. The Tunguska Basin developed as a Palaeozoic rift/sag basin over Proterozoic rifts. The geological provinces along the north and east margins of the Siberian Craton are immature with respect to exploration, so exploration-history analysis alone cannot be used for assessing undiscovered petroleum resources. Therefore, other areas from around the world having greater petroleum exploration maturity and similar geological characteristics, and which have been previously assessed, were used as analogues to aid in this assessment. The analogues included those of foreland basins and rift/sag basins that were later subjected to compression. The US Geological Survey estimated the mean undiscovered, technically recoverable conventional petroleum resources to be approximately 28 billion barrels of oil equivalent, including approximately 8 billion barrels of crude oil, 103 trillion cubic feet of natural gas and 3 billion barrels of natural gas liquids.

Abstract The Siberian craton consists of crystalline rocks and superimposed Precambrian sedimentary rocks deposited in rift basins. Palaeozoic rocks, mainly carbonates, were deposited along the margins of the craton to form an outwardly younger concentric pattern that underlies an outward-thickening Mesozoic sedimentary section. The north and east margins of the Siberian craton subsequently became foreland basins created by compressional deformation during collision with other tectonic plates. The Tunguska Basin developed as a Palaeozoic rift/sag basin over Proterozoic rifts. The geological provinces along the north and east margins of the Siberian craton are immature with respect to exploration, so exploration-history analysis alone cannot be used for assessing undiscovered petroleum resources. Therefore, other areas from around the world having greater petroleum exploration maturity and similar geological characteristics, and which have been previously assessed, were used as analogues to aid in this assessment. The analogues included those of foreland basins and rift/sag basins that were later subjected to compression. The US Geological Survey estimated the mean undiscovered, technically recoverable conventional petroleum resources to be c. 28 billion barrels of oil equivalent, including c. 8 billion barrels of crude oil, 103 trillion cubic feet of natural gas, and 3 billion barrels of natural gas liquids.

Abstract Tertiary and Cretaceous nonmarine sandstones are reservoirs for large amounts of natural gas at Natural Buttes field in the eastern part of the Uinta basin, Utah. A cored interval in the Upper Cretaceous Tuscher Formation dominantly comprises fine- to medium-grained, moderately to well-sorted sandstones and less abundant carbonaceous and coaly shale beds. These rocks represent sedimentation on the lower part of an alluvial braidplain. The Paleocene and Eocene Wasatch Formation unconformably overlies Cretaceous rocks and intertongues with marginal lacustrine strata of the Green River Formation. The cored interval in the upper part of the Wasatch consists of fine-grained lenticular sandstones with small-scale cross-bedding, argillaceous siltstones, and variegated mudstones, all of which were deposited in lower delta plain settings along the margin of Lake Uinta. Cored sandstones in the Tuscher and Wasatch formations have been extensively modified by minor quartz overgrowths; by the precipitation and subsequent dissolution of a carbonate mineral assemblage comprising iron-free calcite, ferroan calcite, dolomite, and ankerite; by local occurrences of anhydrite and barite; and by the formation of authigenic illite, mixed- layer illite-smectite, kaolinite, chlorite, and corrensite. Most authigenic carbonate formed during early burial before significant compaction. During later stages of diagenesis, anhydrite and barite precipitated locally, replacing detrital grains and mineral cements such as carbonate. Porosity and permeability have been significantly reduced in the sandstones owing to clay mineral development and the formation of carbonate cement. Large amounts of natural gas are stratigraphically trapped in these lenticular, diagenetically modified low-permeability sandstones. Potential source rocks in the Tuscher Formation may have generated thermogenic gas even though they are only moderately mature with respect to liquid hydrocarbon generation.