Changes

  | isbn    = 0891816658

  | isbn    = 0891816658

}}

}}

Prudhoe Bay field lies on the Alaska coastal plain between Naval Petroleum Reserve No. 4 (NPRA) and the Arctic National Wildlife Refuge (ANWR; [[:file:Mth14ch07f01.jpg|Figure 1]]). Present-day production from Permian-Triassic sandstones and conglomerates of the Ivishak Formation ([[:file:Mth14ch07f02.jpg|Figure 2]]) is approximately 550 MSTBD.

Prudhoe Bay field lies on the Alaska coastal plain between Naval Petroleum Reserve No. 4 (NPRA) and the Arctic National Wildlife Refuge (ANWR; [[:file:Mth14ch07f01.jpg|Figure 1]]). Present-day production from Permian-Triassic sandstones and conglomerates of the Ivishak Formation ([[:file:Mth14ch07f02.jpg|Figure 2]]) is approximately 550 MSTBD.

[[file:Mth14ch07f03.jpg|thumb|300px|{{figure number|3}}Regional south-to-north cross section from the Brooks Range to the Beaufort Sea illustrates the stratigraphy and major structural features of the North Slope. Prudhoe Bay field formed where the Ivishak Formation is draped over the Barrow Arch, truncated by the Lower Cretaceous unconformity, and overlain by marine shales. Location is shown in Figure 1.]]

[[file:Mth14ch07f03.jpg|thumb|300px|{{figure number|3}}Regional south-to-north cross section from the Brooks Range to the Beaufort Sea illustrates the stratigraphy and major structural features of the North Slope. Prudhoe Bay field formed where the Ivishak Formation is draped over the Barrow Arch, truncated by the Lower Cretaceous unconformity, and overlain by marine shales. Location is shown in Figure 1.]]

Prudhoe Bay field is 52 km long by 19 km wide (32 mi by 12 mi). Structurally, the field occurs between 2500 and 2800 m subsea (8200 and 9200 ft), and original oil- and gas-column thicknesses were 142 m (465 ft) and 122 m (400 ft), respectively. Numerous west-to-east- and northwest-to-southeast-trending faults segregate the reservoir into isolated blocks and, in places, enhance fluid migration ([[:file:Mth14ch07f04.jpg|Figure 4]]).

Prudhoe Bay field is 52 km long by 19 km wide (32 mi by 12 mi). Structurally, the field occurs between 2500 and 2800 m subsea (8200 and 9200 ft), and original oil- and gas-column thicknesses were 142 m (465 ft) and 122 m (400 ft), respectively. Numerous west-to-east- and northwest-to-southeast-trending faults segregate the reservoir into isolated blocks and, in places, enhance fluid migration ([[:file:Mth14ch07f04.jpg|Figure 4]]).

Geologic investigations undertaken since field discovery are almost universal in their acceptance of a fluviodeltaic origin for the Ivishak Formation (Detterman,<ref name=Detterman_1970>Detterman, R. L., 1970, Sedimentary history of the Sadlerochit and Shublik Formations in northeastern Alaska, ''in'' W. L. Adkison and M. M. Brosge, eds., Proceedings of the geological seminar on the North Slope of Alaska: AAPG Pacific Section, p. o1-o13.</ref> Morgridge and Smith,<ref name=Morgridgeandsmith_1972 /> Eckelmann et al.,<ref name=Eckelmannetal_1975>Eckelmann, W. R., R. J. Dewitt, and W. L. Fisher, 1975, Prediction of fluvial-deltaic reservoir geometry, Prudhoe Bay Field, Alaska: Proceedings of the 9th World Petroleum Field, Congress: John Wiley and Sons, International, v. 2, p. 223-227.</ref> Jones and Speers,<ref name=Jonesandspeers_1976 /> Wadman et al.,<ref name=Wadmanetal_1979>Wadman, D. H., D. E. Lamptecht, and I. Mrosovsky, 1979, [https://www.onepetro.org/journal-paper/SPE-7531-PA Joint geologic/engineering analysis of the Sadlerochit Reservoir, Prudhoe Bay Field]: Journal of Petroleum Technology, v. 31, p. 933-940.</ref> Jamison et al.,<ref name=Jamisonetal_1980 /> Melvin and Knight,<ref name=Melvinandknight_1984>Melvin,</ref> Lawton et al.,<ref name=Lawtonetal_1987>Lawton,</ref> McMillen and Colvin,<ref name=Mcmillenandcolvin_1987>McMillen,</ref> Atkinson et al.,<ref name=Atkinsonetal_1988>Atkinson,</ref> Atkinson et al.,<ref name=Atkinsonetal_1990>Atkinson,</ref> Crowder,<ref name=Crowder_1990>Crowder,</ref> Begg et al.,<ref name=Beggetal_1992>Begg,</ref> Tye et al.<ref name=Tyeetal_1999>Tye,</ref>). Fluvial strata have been described as braided-river deposits on a coastal plain (Eckelmann et al.,<ref name=Eckelmannetal_1975 /> Jones and Speers,<ref name=Jonesandspeers_1976 /> Wadman et al.,<ref name=Wadmanetal_1979 /> Melvin and Knight,<ref name=Melvinandknight_1984 /> Lawton et al.,<ref name=Lawtonetal_1987 /> Atkinson et al.<ref name=Atkinsonetal_1990 />) or on a large alluvial fan (McGowen and Bloch,<ref name=Mcgowenandbloch_1985>McGowan,</ref> McGowen et al.<ref name=Mcgowenetal_1987>McGowan,</ref>). Petrophysically defined layers (SMUT Units; [[:file:Mth14ch07f02.jpg|Figure 2]]) constitute a gross reservoir-layering scheme for this interval, which is approximately 180 m (600 ft) thick (Wadman et al.,<ref name=Wadmanetal_1979 /> Melvin and Knight<ref name=Melvinandknight_1984 />).

Geologic investigations undertaken since field discovery are almost universal in their acceptance of a fluviodeltaic origin for the Ivishak Formation (Detterman,<ref name=Detterman_1970>Detterman, R. L., 1970, Sedimentary history of the Sadlerochit and Shublik Formations in northeastern Alaska, ''in'' W. L. Adkison and M. M. Brosge, eds., Proceedings of the geological seminar on the North Slope of Alaska: AAPG Pacific Section, p. o1-o13.</ref> Morgridge and Smith,<ref name=Morgridgeandsmith_1972 /> Eckelmann et al.,<ref name=Eckelmannetal_1975>Eckelmann, W. R., R. J. Dewitt, and W. L. Fisher, 1975, Prediction of fluvial-deltaic reservoir geometry, Prudhoe Bay Field, Alaska: Proceedings of the 9th World Petroleum Field, Congress: John Wiley and Sons, International, v. 2, p. 223-227.</ref> Jones and Speers,<ref name=Jonesandspeers_1976 /> Wadman et al.,<ref name=Wadmanetal_1979>Wadman, D. H., D. E. Lamptecht, and I. Mrosovsky, 1979, [https://www.onepetro.org/journal-paper/SPE-7531-PA Joint geologic/engineering analysis of the Sadlerochit Reservoir, Prudhoe Bay Field]: Journal of Petroleum Technology, v. 31, p. 933-940.</ref> Jamison et al.,<ref name=Jamisonetal_1980 /> Melvin and Knight,<ref name=Melvinandknight_1984>Melvin, J., and A. S. Knight, 1984, [http://archives.datapages.com/data/specpubs/sandsto2/data/a059/a059/0001/0300/0347.htm Lithofacies, diagenesis and porosity of the Ivishak Formation, Prudhoe Bay Area, Alaska], ''in'' D. A. McDonald and R. C. Surdam, eds., Clastic diagenesis: [http://archives.datapages.com/data/alt-browse/aapg-special-volumes/m37.htm AAPG Memoir 37], p. 347-365.</ref> Lawton et al.,<ref name=Lawtonetal_1987>Lawton, T. F., G. W. Geehan, and B. J. Voorhees, 1987, Lithofacies and depositional environments of the Ivishak Formation, Prudhoe Bay Field, ''in'' I. Tailleur and P. Weimer, eds., Alaskan North Slope Geology: Society for Sedimentary Geology (SEPM) Pacific Section, v. 50, p. 61-76.</ref> McMillen and Colvin,<ref name=Mcmillenandcolvin_1987>McMillen, K. J., and M. D. Colvin, 1987, Facies correlation and basin analysis of the Ivishak Formation, Arctic National Wildlike Refuge, Alaska, ''in'' I. Tailleur and P. Weimer, eds., Alaskan North Slope Geology: Society for Sedimentary Geology (SEPM) Pacific Section, v. 50, p. 381-390.</ref> Atkinson et al.,<ref name=Atkinsonetal_1988>Atkinson, C. D., P. N. Trumbly, and M. C. Kremer, 1988, Sedimentology and depositional environments of the Ivishak Sandstone, Prudhoe Bay field, North Slope, Alaska, ''in'' A. J. Lomando and P. M. Harris, eds., Giand Oil and Gas Fields: Society for Sedimentary Geology (SEPM) Core Workshop No. 12, p. 561-613.</ref> Atkinson et al.,<ref name=Atkinsonetal_1990>Atkinson, C. D., J. H. McGowen, S. Bloch, L. L. Lundell, and P. N. Trumbly, 1990, Braidplain and deltaic reservoir, Prudhoe Bay, Alaska, ''in'' J. H. Barwis, J. G. McPherson, and R. J. Studlick, eds., Sandstone Petroleum Reservoirs: New York, Springer-Verlag, p. 7-29.</ref> Crowder,<ref name=Crowder_1990>Crowder, R. K., 1990, [http://archives.datapages.com/data/bulletns/1990-91/data/pg/0074/0009/0000/1351.htm Permian and Triassic sedimentation in the northeastern Brooks Range, Alaska: Deposition of the Sadlerochit Group]: AAPG Bulletin, v. 74, no. 9, p. 1351-1370.</ref> Begg et al.,<ref name=Beggetal_1992>Begg, S. H., E. R. Gustason, and M. W. Deason, 1992, [https://www.onepetro.org/conference-paper/SPE-24698-MS Characterization of a fluvial-dominated delta: Zone 1 of the Prudhoe Bay Field], Paper No. 24698: Society of Petroleum Engineers 67th Annual Technical Conference, Richardson, Texas, p. 351-364.</ref> Tye et al.<ref name=Tyeetal_1999>Tye, R. S., J. P. Bhattacharya, J. A. Lorsong, S. T. Sindelar, D. G. Knock, D. D. Puls, and R. A. Levinson, 1999, [http://archives.datapages.com/data/bulletns/1999/10oct/1588/1588.htm Geology and stratigraphy of fluvio-deltaic deposits in the Ivishak Formation: Applications for development of Prudhoe Bay Field, Alaska:] AAPG Bulletin, v. 84, no. 10, p. 1205-1228.</ref>). Fluvial strata have been described as braided-river deposits on a coastal plain (Eckelmann et al.,<ref name=Eckelmannetal_1975 /> Jones and Speers,<ref name=Jonesandspeers_1976 /> Wadman et al.,<ref name=Wadmanetal_1979 /> Melvin and Knight,<ref name=Melvinandknight_1984 /> Lawton et al.,<ref name=Lawtonetal_1987 /> Atkinson et al.<ref name=Atkinsonetal_1990 />) or on a large alluvial fan (McGowen and Bloch,<ref name=Mcgowenandbloch_1985>McGowan, J. H., and S. Bloch, 1985, Depositional facies, diagenesis, and reservoir quality of the Ivishak Sandstone (Sadlerochit Group), Prudhoe Bay Field: AAPG Bulletin, v. 69, p. 286.</ref> McGowen et al.<ref name=Mcgowenetal_1987>McGowan, J. H., S. Bloch, and D. Hite, 1987, Depositional facies, diagenesis, and reservoir quality of Ivishak Sandstone (Sadlerochit Group), Prudhoe Bay Field (abs.), ''in'' I. Tailleur and P. Weimer, eds., Alaskan North Slope Geology: Society for Sedimentary Geology (SEPM) Pacific Section, p. 84.</ref>). Petrophysically defined layers (SMUT Units; [[:file:Mth14ch07f02.jpg|Figure 2]]) constitute a gross reservoir-layering scheme for this interval, which is approximately 180 m (600 ft) thick (Wadman et al.,<ref name=Wadmanetal_1979 /> Melvin and Knight<ref name=Melvinandknight_1984 />).

[[file:Mth14ch07f05.jpg|thumb|300px|{{figure number|5}}Map of recovery processes active in Prudhoe Bay field. Gravity drainage is the dominant recovery mechanism in the north-central part of Prudhoe, whereas the eastern, southern, and western field margins are under active waterflood and miscible-injectant recovery.]]

[[file:Mth14ch07f05.jpg|thumb|300px|{{figure number|5}}Map of recovery processes active in Prudhoe Bay field. Gravity drainage is the dominant recovery mechanism in the north-central part of Prudhoe, whereas the eastern, southern, and western field margins are under active waterflood and miscible-injectant recovery.]]

Four reservoir-depletion mechanisms (gravity drainage/gas-cap expansion, waterflooding, miscible-gas flooding, and gas cycling) operate simultaneously at Prudhoe Bay ([[:file:Mth14ch07f05.jpg|Figure 5]]; Szabo and Meyers<ref name=Szaboandmeyers_1993>Szabo,</ref>). Each process is managed to work in concert with the existing fluid distribution (expanding gas cap, injected water, and oil), regional geology (2&deg; southward structural dip; intersecting east-west and northwest-southeast fault trends), and field-scale geology. Interbedded conglomerates, sandstones, and mudstones create a spatially variable rock volume containing permeabilities ranging from a few millidarcys to tens of darcys. Tailoring horizontal wells and their completions to suit specific engineering and geologic conditions significantly increases primary and tertiary recovery from fine-grained sandstones and conglomerates in Prudhoe Bay field.

Four reservoir-depletion mechanisms (gravity drainage/gas-cap expansion, waterflooding, miscible-gas flooding, and gas cycling) operate simultaneously at Prudhoe Bay ([[:file:Mth14ch07f05.jpg|Figure 5]]; Szabo and Meyers<ref name=Szaboandmeyers_1993>Szabo, D. J., and K. O Meyers, 1993, Prudhoe Bay: Development history and future potential, Paper No. 26053: Society of Petroleum Engineers Western Regional Meeting, Anchorage, Alaska, p. 1-9.</ref>). Each process is managed to work in concert with the existing fluid distribution (expanding gas cap, injected water, and oil), regional geology (2&deg; southward structural dip; intersecting east-west and northwest-southeast fault trends), and field-scale geology. Interbedded conglomerates, sandstones, and mudstones create a spatially variable rock volume containing permeabilities ranging from a few millidarcys to tens of darcys. Tailoring horizontal wells and their completions to suit specific engineering and geologic conditions significantly increases primary and tertiary recovery from fine-grained sandstones and conglomerates in Prudhoe Bay field.

==References==

==References==