Geology topics
Publications and source records attributed to Marilyn E. Tennyson.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 30.5 trillion cubic feet of tight gas in the Grand Erg/Ahnet Province of Algeria.
In 2008, the U.S. Geological Survey assessed the potential for undiscovered oil and gas resources of the Franklinian Shelf Province of northern Canada and Greenland as part of the U.S. Geological Survey Circum-Arctic Resource Appraisal Program. The Franklinian Shelf Province lies along the northernmost edge of the North American craton in Greenland and Canada. It encompasses a Cambrian through Middle Devonian passive margin sequence deposited on the margin of an ocean formed by rifting and seafloor spreading that began in latest Precambrian time and continued into Ordovician time. In the Canadian part of the province, the passive margin sequence is overlain by a thick succession of Devonian clastic strata shed from uplifts produced by the Caledonian collision between Laurentia and Baltica that closed Iapetus Ocean. The late Silurian to Early Devonian Boothia-Cornwallis uplifts within the region, apparently a distal effect of earlier phases of the Caledonian collision, were local sources of clastic wedges within the predominantly carbonate shelf sequence. Much of the northern part of the province was subjected to folding and thrusting during Late Devonian to earliest Carboniferous Ellesmerian deformation, followed by a prolonged period of erosion. The eastern part of the province again experienced transpressive and compressive deformation as Greenland converged with North America during the early Tertiary Eurekan orogeny. Potential source rocks include Ordovician to Lower Devonian shales that contain abundant oil-prone organic matter, deposited on the outer continental shelf and slope. The most likely source rocks are Silurian strata, deposited as the continental shelf was drowned by a marine transgression caused by regional subsidence most likely associated with thrust loading. Potential source rocks in Greenland also may include organic-rich Cambrian shales deposited on the continental shelf. Rapid burial by thick Caledonian-derived strata in Late Devonian time abruptly matured the source rocks and generated oil; continued rapid burial may have cracked much of the accumulated oil to gas. In North Greenland, oil generation may have resulted from burial by now-eroded Devonian strata or from burial by Ellesmerian thrust sheets. Widespread bitumen in outcrops and in exploration wells appears to confirm that oil was indeed generated. Potential reservoirs include Cambrian nearshore clastic strata, Cambrian to Silurian carbonate bank strata, and Silurian to Middle Devonian reef buildups on the drowned shelf. Because Ellesmerian deformation postdated migration, only stratigraphic traps are likely, except in the area of the Boothia-Cornwallis uplift, a north-trending, structurally elevated zone, where structural traps formed by late Silurian to Early Devonian deformation are possible. It is unlikely that any large accumulations survived subsequent deformation or uplift and erosion. Three assessment units were defined: the Western Franklinian Shelf, the Boothia-Cornwallis Uplift, and the Eastern Franklinian Shelf Assessment Units. These assessment units were not quantitatively assessed, mostly because of the high risk to timing and preservation.
The Sverdrup Basin Province, an area of 515,000 square kilometers on the northern margin of North America, extends 1,300 kilometers across the Canadian Arctic Islands from near the Mackenzie Delta to northern Ellesmere Island. It consists of an intracratonic late Paleozoic to early Cenozoic rift-sag basin and a Mesozoic rift shoulder that bounds it on the north. Basin inception was Mississippian, manifested by deposition of nonmarine strata in rift basins, followed by Pennyslvanian marine transgression, which began with evaporites and progressed to Permian carbonate and clastic deposition at basin fringes and organic-rich marine strata in the basin center. Sediment transport was both northward from North America and southward from a now-subsided or rifted-away landmass to the north. Mesozoic strata indicate continued marine deposition, including both organic-rich, fine-grained rocks deposited during highstands and progradational deltaic sequences. A new episode of rifting began in Middle Jurassic time and culminated in the opening of the Canada Basin by Early Cretaceous seafloor spreading. The Sverdrup Rim formed as the rift shoulder between North America and the thinned, subsided crust to the north. Widespread Upper Cretaceous organic-rich shales were deposited during the major transgression induced by Canada Basin opening, followed by an influx of coarser east-derived detritus. In Paleogene time, incipient North Atlantic seafloor spreading caused deformation in northeasternmost North America, producing uplifts that shed detritus westward across the Sverdrup Basin. Tight folding and thrusting resulting from the Eurekan orogeny took place in the eastern part of the basin during the Eocene, with decreasing intensity of deformation westward. Since deformation ended in late Eocene time, little significant tectonism or deposition has taken place. Two petroleum systems were defined in the Sverdrup Basin Province. Upper Paleozoic marine shale generated petroleum beginning in the Early Triassic, but this petroleum system was not quantitatively assessed because reservoir quality in adjacent strata is poor, the rocks are mostly overmature, and subsequent deformation likely affected trap integrity. The second petroleum system was sourced by Lower Triassic strata rich in oil-prone organic matter. Oil was generated during Paleogene burial synchronous with Eurekan deformation, and the oil migrated into Triassic and Jurassic deltaic, shallow marine and nonmarine strata. However, most of the oil may have escaped during deformation and subsequent uplift and erosion, which probably caused oil to be displaced from traps by gas expansion. The population of undiscovered accumulations was characterized as likely to include stratigraphically trapped and small, structurally trapped accumulations, with a median size of 80 million barrels of oil (MMBO); the number of undiscovered accumulations was estimated to be between 1 and 50, with the most likely number being 10. The resulting estimate of undiscovered, technically recoverable, conventional oil resources is 61 to 1,255 MMBO, with a mean of 427 MMBO. Undiscovered, technically recoverable, conventional gas resources are estimated at 4.95 trillion cubic feet (TCF), with slightly more than half of that in nonassociated gas accumulations. A third petroleum system in the adjacent Amerasia Basin Province to the north was considered somewhat likely to contain accumulations on the Sverdrup Rim. Deeply buried Upper Jurassic, Upper Cretaceous, and Eocene organic-rich strata probably generated oil that may have migrated up the continental slope into Triassic to Paleogene sandstones on the Sverdrup Rim. Based on analogy with the Barrow Arch in Alaska, a median of 20 accumulations was estimated, with accumulation volumes as much as 2,500 MMBO and a median of 100 MMBO. The probability of at least one accumulation of the minimum size assessed (50 MMBO) was estimated at 0.22. The resulting estimate of undiscovered, technically recoverable, conventional oil resources is 0 to 2,679 MMBO, with a mean of 424 MMBO. Mean estimates for associated and nonassociated gas are 1.3 and 2.3 TCF, respectively.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 3.6 billion barrels of oil and 8.9 trillion cubic feet of natural gas (associated and nonassociated) in conventional accumulations in Mississippian through Paleogene strata in the central North Slope of Alaska.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 5.6 billion barrels of oil and 109.1 trillion cubic feet of gas in the Jurassic Hanifa-Tuwaiq Total Petroleum System of the Arabian Peninsula.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 118 million barrels of continuous oil and 170 billion cubic feet of continuous gas in the Jurassic Posidonia Shale Total Petroleum System of western Greece and southern Albania.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable continuous mean resources of 1.8 billion barrels of oil and 117.2 trillion cubic feet of gas in the Upper Ordovician Point Pleasant Formation and Utica Shale of the Appalachian Basin Province.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable continuous mean resources of 96.5 trillion cubic feet of gas in the Middle Devonian Marcellus Shale of the Appalachian Basin Province.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated means of 534 million barrels of oil and 939 billion cubic feet of gas in the Niobrara interval of the Cody Shale in the Bighorn Basin Province, Wyoming and Montana.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of about 54 trillion cubic feet of gas resources within gas hydrates in the North Slope of Alaska.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 16.4 billion barrels of oil and 106.3 trillion cubic feet of gas in the Sirte and Pelagian Basin Provinces of Libya, Tunisia, Malta, and Italy.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 378 million barrels of oil and 7 trillion cubic feet of gas in the Grand Erg/Ahnet Province of Algeria.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 241 million barrels of tight oil and 10.1 trillion cubic feet of tight gas in the Junggar and Santanghu Basins of northwestern China.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 1.4 billion barrels of shale oil and 26.9 trillion cubic feet of shale gas in Paleozoic formations in the Tarim Basin of China.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 1.3 billion barrels of oil and 63 trillion cubic feet of gas in the Reggane Basin Province of Algeria.
The Northwest Canada Interior Basins Province is bounded by the Mackenzie and Richardson Mountains on the southwest and west, by the Eskimo Lakes Arch on the northwest, and by the erosional limit of Paleozoic strata on the east. It lies within the far northwest part of the Paleozoic continent of Laurentia. During early Paleozoic time, it was part of a passive margin formed when the Neoproterozoic supercontinent Rodinia broke apart. A Cambrian marine transgressive sequence gave way to an evaporitic intrashelf basin, succeeded by a westward-building carbonate bank from Late Cambrian through Middle Devonian time. In Late Devonian and early Carboniferous time, the region was buried by a thick succession of south-prograding clastic strata derived from orogenic belts to the northeast and north. A subsequent period of inactivity and erosion persisted until sedimentation resumed as the opening of the Canada Basin initiated an Early Cretaceous marine transgression over much of the region. Later in Cretaceous time, clastic strata derived from Cordilleran uplifts to the southwest began to prograde north, ending with eventual Laramide uplift and deformation in latest Cretaceous and Paleogene time. Two petroleum systems are known within the province. A petroleum system in Cambrian to Middle Devonian strata, sourced by alginitic Cambrian shales and sealed by Cambrian evaporites, is proven by modest gas discoveries in the Colville Hills; generation is attributed to burial under the Upper Devonian clastic wedge. An Upper Devonian petroleum system, proven by the presence of the 250-million-barrel Norman Wells field at the southern edge of the province, was sourced by organic-rich shale of the Canol Formation. Generation is similarly inferred to have been driven by burial beneath the Devonian clastic wedge, perhaps augmented locally by additional Cretaceous burial. Potential reservoirs include Devonian reefs and sandstones stratigraphically below and laterally equivalent to the source rocks, as well as overlying sandstones in the clastic wedge. Subordinate source rocks could include organic-rich shales within the clastic wedge. Principal risks to the lower Paleozoic petroleum system include (1) inadequate reservoir volume for a field of the minimum size and (2) petroleum loss by remigration caused by Laramide deformation. One lower Paleozoic assessment unit (AU) was quantitatively assessed, with estimated resources of 0 to 117 million barrels of oil (MMBO), mean 23 MMBO; and 0 to 1,364 billion cubic feet of gas (BCFG), mean 310 BCFG. The principle risks to the Devonian petroleum system were considered to be (1) lack of preservation due to extensive erosion before the Cretaceous, and (2) inadequate reservoir volume, because the best potential reservoir strata, Devonian reefs, may be absent throughout most of the province owing to either lack of deposition or erosion. These risks were sufficiently high that the single AU defined in the Devonian petroleum system was not quantitatively assessed, because the chance of a field of the minimum size, 50 million barrels of oil equivalent, was estimated to be only 0.1.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 24 trillion cubic feet of gas in the Mesaverde Group and Wasatch Formation of the Uinta-Piceance Province in northeast Utah and northwest Colorado.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean resources of 1.2 billion barrels of tight oil and 29.1 trillion cubic feet of tight gas in Mesozoic formations in the Sichuan Basin of China.