The main part of Anadyr basin is in the shelf portion of the Russian sector of the Barents Sea. It is designated as the East Anadyr downwarp and is traced to the east and southeast 180-220 km from the coast line into the Pacific Ocean. The area of the offshore part of the basin on the shallow-water shelf with water depths from 20 to 80 m exceeds 60,000 sq km. Structural development was in stages, reflecting pre-middle Miocene, Pliocene, and even Pleistocene phases of folding.
Reconnaissance exploration with a thin net of seismic profiles in Anadyr Gulf has disclosed 16 local structures that may serve as traps for hydrocarbons. As a rule the dimensions of these traps are much greater than similar structures onshore. Several structures have been recognized at distance of 50 km from the coast as well as a group of large potential traps 130-170 km to the southeast of Beringovskiy. Oil and gas fields have been discovered in the western, onshore part of the basin, and indications of oil and gas are found in the eastern part. The oil-gas potential of the offshore part of Anadyr basin is assessed at 0.9-0.95 billion tons of oil equivalent (6.3-6.6 BBOE).
In order to minimize expenses in refining this assessment it would be best to drill in coastal sectors, the most favorable of which is the Lagun downwarp, which is located on the southeast of the continental part of Anadyr basin.
Several litho-stratigraphic complexes are recognized in the Cenozoic section of Anadyr basin. At the base of the section are volcanics and sediments of the Paleocene and possibly lower Eocene. These and probably also upper Senonian form a single structural stage of the intermediate type between the older Mesozoic complexes and the younger Cenozoic rocks of the sedimentary cover. Higher in the section and resting discordantly on an erosion surface are Eocene- Oligocene, Neogene, and Quaternary deposits.
Most of the sedimentary section of Anadyr basin consists of clastics of the upper Eocene-Miocene. Within this section are regional angular discordances corresponding with the main episodes of tectonic evolution of the basin. Discordance is present at the base of the Maynits (Oligocene), Sobol'kov (lower Miocene), and Avtatkul (middle Miocene) Horizons. The sub-Avtatkul break is present everywhere in the basin. The youngest surface of regional discordance is between the middle-upper Miocene and the Pliocene-Quaternary sediments. This break extends far beyond Anadyr basin on the Barents Sea Shelf.
The main oil-source beds of Anadyr basin are thought to be in the Maynits Horizon, which consists of gray clayey siltstone and beds of argillite. Fine-grained Maynits rocks are the most enriched in organic matter at 0.65 percent. Continued as next News Letter.
Taken from Burlin and Agapitov, 2001; digested in Petroleum
Geology, vol 36, no. 4, in preparation, two maps, one cross section.
Copyright 2002 James Clarke. You are encouraged to print out
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