Structural Geology of Laptev Shelf - a New Look and Perspectives

Evgheniy I. Grokhotov
TomskNIPIneft, Tomsk, Russia.

The Laptev Sea region is in an unique plate tectonic setting in the Arctic ocean. It is a key region for the reconstruction of the Late Mesozoic and Cenozoic history of the Arctic. This region developed under the influence of the Gakkel spreading ridge during the last 60-56 Ma. Today’s understanding of the Laptev shelf geology is based on the seismic reflection data and extrapolation of the terrestrial geology. The Laptev Rift System consists of several deep subsided rifts and high standing blocks of the basement. From west to east they are: West Laptev and South Laptev Rift basins, Ust’ Lena Rift, East Laptev and Stolbovoy horsts, Bel’kov-Sviatoy and Anisin Rifts. This work is based on interpretation of seismic profiles made between 1989 and 2005, on evaluating hydrocarbon potential of sedimentary cover deposits framing land and islands. Seven seismic complexes were outlined while analyzing seismic interpretation data, tectonics of the study area and contrasts in the gravity field. These are Upper Riphean-Cambrian, Middle Paleozoic, Permian, Triassic, Jurassic-Lower Cretaceous, Cretaceous and Cenozoic potentially oil-and-gas-bearing complexes. The estimated total thickness of sedimentary cover section vary between 1-4 km in Eastern part and up to 15.5 km in Western region. We built facies maps based on seismofacial analysis. Analysis of available material allowed to make geological section of Western part of Laptev shelf with source rocks, seals and potential collectors. We also estimated geological risks (trap presense, trap volume, collector presense, safe storage of hydrocarbon field, seal presense, generation and accumulation of hydrocarbons) that resulted in ranging of perspective areas within Laptev shelf. The most perspective are in order West-Laptev, Central-Laptev, Trofimov, Eastern, Mariinsky and North-Laptev regions. Analysis of available data gave us possibility to evaluate oil and gas potential prospects at a new qualitative level. At the same time today’s tectonics and geodynamics of the Laptev shelf are poorly studied. The problem of oil geological zoning still exists because of complicated geology of the Laptev shelf and absence of drilling offshore.

AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia