Middle Paleozoic Reefs of Siberian North as Potential Reservoirs of Oil and Gas: ABSTRACT

Abstract

Middle Paleozoic buried reef masses are believed to be possible oil and gas reservoirs in the Arctic, because similar reefs yield commercial oil and gas in adjacent areas (Ural foothills, Western Canada, etc.). This possibility is based on the wide distribution of middle Paleozoic carbonate formations in the Arctic and on the prediction of the presence of ancient reefs. The middle Paleozoic carbonate formations containing reef limestones occur with the terranes of Arctic Siberia from Novaya Zemlya on the west to the Chukotsk Peninsula and Koryak Upland on the east, suggesting favorable paleoclimatic environments. The middle Paleozoic tropical belt had a strike across the Arctic Ocean oblique to the modern latitudes. The available data on paleotectonic conditions in the Arctic during the middle Paleozoic indicate the presence of certain structural zones controlling the distribution of reefs, i.e., geosyncline-platform boundaries and depressions within platforms. If one considers these facts and takes into account lithologic features of the ancient reefs (organic framework, nearreef, and related facies) the following reef provinces may be distinguished Pechora-Novaya Zemlya, Taimyr-Tungusy, and East Siberian-Chukotsk provinces. Only for the Pechora-Novaya Zemlya province do we have a direct evidence for widespread reefs. Devonian reef structures in the southern part of this province are oil-productive in the Pechora basin. In the Taimyr-Tungusy province, reefs are not yet known, but a set of features is present which are critical for the prediction of ancient reefs (e.g., thick salt deposits). Here the possible reef coral-stromatoporoid limestones have a fairly high porosity with generally abundant aquifers and gas shows. The East Siberian-Chukotsk province is questionable, because the possibility that reefs are present has been recognized only from indirect data on the old Hyperborean platform and from the presence of the middle Paleozoic carbonate complex in the New Siberian Islands, Kolyma, and Chukotsk, as well as the presence of graptolitic facies (which commonly border reefs) in the New Siberian and De-Longa Islands. The middle Paleozoic reef bodies known from the Koryak Upland seem to have no relation to the East Siberian-Chukotsk reef province; those may be isolated reef frameworks on the slopes of volcanic cones. End_of_Article - Last_Page 2500------------