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Petroleum Potential and Stratigraphic Architecture of Siberian Frontier Basins as Revealed by Long Offset, Long Record Seismic Surveys

Abstract

Eastern Russia Arctic SPANTM (ERAS) is a multi-phase survey presently comprising 13215 km of new long offset, long record reflection data in the Laptev, East Siberian, and Chukchi Seas, an area of 3×10E6 km2 spanning a distance of 2500 km along one of the broadest continental shelves. The data are processed to display 16 sec (PSTM) and 40 km (PSDM) records. With no offshore wells, the geology is thought to be a simple extension of onshore geology, dominated by Phanerozoic fold belts, associated volcanic & plutonic complexes, and suture assemblages (acoustic basement), locally overlain by successor basins and a partial cover of a thin platformal overlap succession. The proven East and West Siberian Basins lie well to the south in central Siberia. Hence with <.04 line km/km2 (Kaminsky et al., 2011), the area has been previously thought to have limited petroleum potential. USGS Fact Sheet 2008–3049 for example assigns little potential to the East Siberian Sea, and modest potential to the Laptev Sea and Hope Basin, compared to other circum-arctic basins. However, ERAS and potential field data image a number of attractive late Mesozoic and Cenozoic basins on the shelf with at least 7.5 to 10 km of sedimentary fill, and in the case of the North Chukchi Basin something like 20 km of fill. These basins exhibit a variety of stratigraphic fill styles, related to the tectonics underlying their creation. For example, late-stage (post-rift) architecture in the North Chukchi Basin shows Tertiary deltaic progradational sequences traversing over 400 km northward and overlying Late Cretaceous high-accommodation aggradational sediments. This fill style creates several prospective petroleum system/reservoir combinations. In contrast, the Laptev Sea and Lena delta areas exhibit trends and successions related to passive margin subsidence histories, with low-angle sedimentary systems tracts including well-developed ancient shelf margins and lowstand systems tracts, all cut by intra-continental extensional structures on trend with the active Gakkel Ridge spreading center. These basins offer petroleum systems development with pay options in shelf margin, lowstand systems, and within the Neogene rifts. A mega-regional total sediment (above acoustic basement) isopach map in the East Siberian Sea illustrates that several other large gravity lows are in fact substantial, presumably prospective basins.