The Chukchi Sea is that part of the Arctic Ocean north of northeastern
Siberia and northwest of Alaska. It has an area of 582,000 sq km, and
average water depth is 77 m. It is frozen over from November to May.
The main structural features of the region are the South Chukchi basin,
North Chukchi basin, and the intervening Gerald-Wrangel zone of highs.
Passive margin sediments of the North Chukchi basin are more than 10 km
thick and are highly favorable for discoveries. Prudhoe Bay is far to the
east of this basin but is on its trend. The sedimentary section of the
South Chukchi basin is relatively thin at 2-4 km.
The North Chukchi basin is of interest for petroleum, although it lies
400-600 km north of the Chukchi Peninsula. The thickness of the section
at 10 km greatly exceeds that of the North Slope of Alaska with its 6 km
thickness, This North Chukchi basin has a progradational structure.
Paleozoic sediments predominate on the Gerald-Wrangel system of
highs. Then to the north are thick Permo-Triassic - Jurassic deposits,
and farther to the north are Cretaceous-Cenozoic sediments.
By analogy with the North Slope of Alaska, three petroleum systems
are expected to be present in the North Chukchi basin: Paleozoic,
Permian-Mesozoic, and Upper Cretaceous-Cenozoic.
The Paleozoic system includes carbonate reservoirs and seals.
The main source beds are Devonian-Carboniferous clayey
carbonates with sapropelic organic matter.
The Permian-Mesozoic system contains good reservoirs and seals.
Potential source beds are Permo-Triassic clayey rocks with sapropelic
organic matter as well as some Jurassic and Cretaceous rocks.
The Upper Cretaceous-Cenozoic system also has good reservoirs
and seals. Source beds are expected in Cretaceous-Paleocene lake
beds, Eocene-Oligocene coastal marine deposits, and Oligocene-Miocene
clayey-siliceous marine deposits.
All three of these petroleum systems may be hydrodynamically
connected by faults.
Two petroleum systems are recognized in the South Chukchi basin:
Mesozoic and Upper Cretaceous-Cenozoic. The Mesozoic system is
over-mature and offers little promise. The Upper Cretaceous-Cenozoic
system may contain small gas pool.
A cautious assessment of resources in place for the Russian sector
of Chukchi Sea is 5-7 billion tons oil equivalent (35-50 BBOE). Using
Alaska North Slope as an analog this assessment increases to 13-15
billion tons oil equivalent (91-105 BBOE) (Petroleum Geology, vol. 34,
no. 2, p. 144-149, 2000; structure map, cross section, and
stratigraphic chart - from Orudzheva and others 1999).
Copyright 2000 James Clarke. You are encouraged to print out this
News Letter and forward it to others. Earlier News Letters are available at
http://geocities.com/internetgeology/
