Team 1 Hydrocarbon Potential Evaluation Team Summary of Knowledge With respect to ANWR the Definition of an A Introduction 2 Formation of Hydrocarbons 3 The Geologic History of ANWR The purpose of this section is to provide everyone with a basic understanding of how ANWR came about geologically speaking This information is important in understanding why hydrocarbons are where they are and is also important in understanding its current geological condition such as seismic activity how that impacts exploitation and so forth The information is very brief and the sources used are at the conclusion Overview The Artic National Wildlife Refuge covers an area of 1 5 million acres and is roughly 105 miles east west and 16 40 miles north south It is bounded on the west by the Canning and Stains River north by the Beaufort Sea east by the Archilik River and South by township lines and approximately the 1000 ft elevation contour About 100 000 acres are owned by Native Alaskans Kaktovik Inupiat Corporation The village of Kaktovik population 200 is in the 1002 region on Barter Island and is the only village in ANWR The region mostly lies within the Artic Coastal Plain physiographic province The area is treeless tundra covered and 99 wetland Topographically speaking it is comprised of foothills 95 of area river flooded plains 25 hilly coastal plains 22 lagoons and oceans 5 thaw lake plains 5 and mountains less than 1 Geologically speaking ANWR is at present 95 covered by a veneer of unconsolidated frozen sediments of late Cenozoic mostly Quaternary age generally less than 100 ft thick History The geologic history of ANWR is briefly as follows Development of Devonian to Triassic south facing in present day coordinates passive continental margin Northern Part margin rifted in Jurassic to early cretaceous time for an unknown parent continent Coeval with the North and arc continent collision occurred in the south producing and organic land mass and adjacent foreland basin As the foreland basin filled continuing deformation resulted in a foreland fold and thrust belt Youngest foreland basin sediments where fold and thrust belt intersects and overrides the earlier formed rift margin and when the deformation and related sedimentation continues to present More geologically complex that anywhere in Northern Alaska 4 Part of the North Slope geologic provinces Petroleum prospective rocks are restricted to mostly the Mississippi and younger rocks same as in Prudhoe Bay and Mackenzie Delta region of Canada The plate that ANWR rests upon is part of small continental fragment call Artic Alaska micro plate Historically most hypotheses regarding plate tectonics hold that Cretaceous rifting and the opening of the oceanic Canadian basin of the Artic ocean is what gave rise to the eventual positioning of ANWR Thermal Maturity Thermal maturity is the level of alteration of the organic matter in a given sedimentary rock due to high temperatures It gives the absolute maximum temperature to which the rock has been exposed When there is no igneous source of heat the maximum temperature measured is just a product of burial heating Therefore the thermal maturity of a rock can be used to determine the uplift it has suffered and this can show broad patterns of geologic structure in a studied region The tectonic makeup of Alaska is very complex and there is little stratigraphic correlation between areas There thermal maturity is used to determine the structure of basins and the deformations they have Thermal maturity indicators The most common available data for Alaska comes from vitrinite reflectance and conodon color alteration Vitrinite is organic matter composed of remains of woody plants that is found in classic sedimentary rocks It originated in terrestrial environments During burial heating vitrinite loses volatile compounds and the carbon turns into graphite increasing its reflectively This reflectively is proportional to the temperature reached is not influenced by pressure or common chemical reactions and doesn t return to the original state after it has reached a given level For heating periods greater than 1 000 years the reflectance of vitrinite depends only on the maximum temperature reached and not in the time Conodons are teeth like fossils of primitive fish that existed from the Cambrian to the Triassic They were deposited in marine environments and are found in carbonates and loose classic sedimentary rocks Conodons are composed of layers of apatite calcium fluoride phosphate Ca5F PO4 3 and organic matter When conodons are buried and the temperature rises the organic matter is carbonized and its color changes from light yellow to black then to white and finally to clear There are established standards between the color of conodons and the temperature they were subject to Regional thermal maturity patters 5 Tertiary basins of interior Alaska The low thermal maturity of surface rocks show that the basins are at their maximum burial depth and they have suffered no uplift Aleutian Arc The rocks mature with depth being under mature at the surface This shows that the basins are near their maximum burial depth Colville basin North Slope At the surface the thermal maturity of rocks increases from the coast at the north to the Brooks Range origin at the south Yukon Koyukuk basin Kuskokwin flysh sandstone schist belt There is a nearly concentric thermal maturity pattern showing greater uplift at the basin margins The basin as a whole suffered uplifting and deformation Kandik basin east central Alaska The basin shows uplifts and a fold and thrust belt placing younger mature rocks over older immature rocks Petroleum Systems The petroleum systems meaning where the areas in which petroleum is likely to be found coupled with information on what type of hydrocarbons are present and with which geologic features found in the North Slope include Ellesmerian Source rocks type II kerogen Shublik Formation gas Kingak Shale gas Pebble shale unit Reservoir rocks Endicott Group Sedlerochit Group quartz rich conglomerate sandstone Kuparuk River Formation of Jamison Lisburne Group carbonate Overburden to mature source rocks Brookian sequence deltaic deposits Type of hydrocarbons Low gravity med to heavy hydrocarbons High sulfur content Torok Nanushuk North East North Slope 6 Source rocks type III kerogen Torok Formation Pebble shale unit Reservoir rocks Nanushuk Formation sandstones derived from formation of Brooks Range
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