Changes

==Geologic setting==

==Geologic setting==

The North Slope evolved from a passive continental margin to a foredeep during the Jurassic. Prior to the Jurassic, Paleozoic and Mesozoic strata were deposited on a passive continental margin. They consist of Carboniferous platform carbonate rocks and Permian to Jurassic shelf to basinal siliciclastic rocks. The passive margin converted to a foredeep during the Jurassic and Cretaceous when it collided with an ocean island arc. The foredeep began to fill with sediments in the Middle Jurassic and continues to do so.

The North Slope evolved from a passive continental margin to a foredeep during the Jurassic. Prior to the Jurassic, Paleozoic and Mesozoic strata were deposited on a passive continental margin. They consist of Carboniferous platform carbonate rocks and Permian to Jurassic shelf to basinal siliciclastic rocks. The passive margin converted to a foredeep during the Jurassic and Cretaceous when it collided with an ocean island arc. The foredeep began to fill with sediments in the Middle Jurassic and continues to do so.

The foredeep basin fill consists of orogenic sedimentary materials eroded from the nearby ancestral Brooks Range that were deposited as a northeasterly prograding wedge of non-marine, shallow marine, basin-slope, and basin conglomerates, sandstones, and mud-stones.

The foredeep basin fill consists of orogenic sedimentary materials eroded from the nearby ancestral Brooks Range that were deposited as a northeasterly prograding wedge of non-marine, shallow marine, basin-slope, and basin conglomerates, sandstones, and mud-stones.

==Petroleum system map==

==Petroleum system map==

The map below shows the Ellesmerian(!) petroleum system geographic extent. The limit is determined by the extent of the contiguous active source rock and the related petroleum accumulations.

[[:file:petroleum-systems_fig3-12.png|Figure 1]] shows the Ellesmerian(!) petroleum system geographic extent. The limit is determined by the extent of the contiguous active source rock and the related petroleum accumulations.

[[file:petroleum-systems_fig3-12.png|thumb|{{figure number|3-12}}.]]

[[file:petroleum-systems_fig3-14.png|left|thumb|{{figure number|3}}.]]

==Petroleum system maturity map==

==Petroleum system maturity map==

The map below shows the thermal maturity of the two main Ellesmerian(!) petroleum system source rocks, the Shublik Formation and the Kingak Shale. Note that Ellesmerian(!) petroleum system traps (shown in Figure 3-12) are mostly located above immature source rocks.

[[:file:petroleum-systems_fig3-13.png|Figure 2]] shows the thermal maturity of the two main Ellesmerian(!) petroleum system source rocks, the Shublik Formation and the Kingak Shale. Note that Ellesmerian(!) petroleum system traps (shown in [[:file:petroleum-systems_fig3-12.png|Figure 1]]) are mostly located above immature source rocks.

 

[[file:petroleum-systems_fig3-13.png|thumb|{{figure number|3-13}}.]]

==Petroleum system cross section==

==Petroleum system cross section==

The cross section of the Ellesmerian(!) petroleum system (below) shows major structural-stratigraphic elements, the occurrence of oil fields, elevation of selected vitrinite reflectance values, and reflectance isograds. For the location, refer to Figure 3-12.

The cross section of the Ellesmerian(!) petroleum system ([[:file:petroleum-systems_fig3-14.png|Figure 3]]) shows major structural-stratigraphic elements, the occurrence of oil fields, elevation of selected vitrinite reflectance values, and reflectance isograds. For the location, refer to [[:file:petroleum-systems_fig3-12.png|Figure 1]].

[[file:petroleum-systems_fig3-14.png|thumb|{{figure number|3-14}}.]]

[[file:petroleum-systems_fig3-15.png|thumb|{{figure number|4}}.]]

==Burial history chart==

==Burial history chart==

Analysis of the burial history chart of the Inigok 1 well (below) and other burial history charts indicates peak petroleum generation (the critical moment) probably occurred in Late Cretaceous time (approximately 75 Ma) in the western North Slope and in early Tertiary time (approximately 50 Ma) in the central and eastern part of the North Slope. Also, note the large increase in the rate of sedimentation during the Early Cretaceous.

Analysis of the burial history chart of the Inigok 1 well ([[:file:petroleum-systems_fig3-15.png|Figure 4]]) and other burial history charts indicates peak petroleum generation (the critical moment) probably occurred in Late Cretaceous time (approximately 75 Ma) in the western North Slope and in early Tertiary time (approximately 50 Ma) in the central and eastern part of the North Slope. Also, note the large increase in the rate of sedimentation during the Early Cretaceous.

[[file:petroleum-systems_fig3-15.png|thumb|{{figure number|3-15}}.]]

[[file:petroleum-systems_fig3-16.png|left|thumb|{{figure number|5}}(left). Copyright: Seifert et al., 1980; courtesy World Petroleum Conference. (right) From ;<ref name=ch03r9>Sedivy, R., A., Penfield, I., E., Halpern, H., I., Drozd, R., J., Cole, G., A., Burwood, R., 1987, Investigation of source rock–crude oil relationships in the northern Alaska hydrocarbon habitat, in Tailleur, I., Weimer, P., eds., Alaskan North Slope Geology: Pacific Section SEPM Book 50, p. 169–179.</ref> courtesy Pacific Section of SEPM.]]

==Oil-source rock correlation==

==Oil-source rock correlation==

Biological marker analysis (below, left) from the main reservoir rock, Sadlerochit Group, of Prudhoe Bay field shows that the oil originated from the Shublik Formation, the Kingak Shale, and the Hue Shale. Carbon isotopic composition comparisons (below, right) indicate that Shublik and Kingak share similar ¹³C values with oil from the Prudhoe Bay field, whereas the Hue Shale does not.

Biological marker analysis ([[:file:petroleum-systems_fig3-16.png|Figure 5]]) from the main reservoir rock, Sadlerochit Group, of Prudhoe Bay field shows that the oil originated from the Shublik Formation, the Kingak Shale, and the Hue Shale. Carbon isotopic composition comparisons ([[:file:petroleum-systems_fig3-16.png|Figure 5]])) indicate that Shublik and Kingak share similar ¹³C values with oil from the Prudhoe Bay field, whereas the Hue Shale does not.

[[file:petroleum-systems_fig3-16.png|thumb|{{figure number|3-16}}(left). Copyright: Seifert et al., 1980; courtesy World Petroleum Conference. (right) From ;<ref name=ch03r9>Sedivy, R., A., Penfield, I., E., Halpern, H., I., Drozd, R., J., Cole, G., A., Burwood, R., 1987, Investigation of source rock–crude oil relationships in the northern Alaska hydrocarbon habitat, in Tailleur, I., Weimer, P., eds., Alaskan North Slope Geology: Pacific Section SEPM Book 50, p. 169–179.</ref> courtesy Pacific Section of SEPM.]]

[[file:petroleum-systems_fig3-17.png|thumb|{{figure number|6}}.]]

==Petroleum system events chart==

==Petroleum system events chart==

The events chart below for the Ellesmerian(!) petroleum system indicates when its elements and processes occurred. The cross-hatched pattern shows the estimated time of the tilting of the Barrow Arch, which resulted in remigration of petroleum from older to younger (early Tertiary) reservoir rocks.

[[:file:petroleum-systems_fig3-17.png|Figure 6]], an events chart for the Ellesmerian(!) petroleum system, indicates when its elements and processes occurred. The cross-hatched pattern shows the estimated time of the tilting of the Barrow Arch, which resulted in remigration of petroleum from older to younger (early Tertiary) reservoir rocks.

 

==Size of the petroleum system==

==Size of the petroleum system==