Structure and Evolution of Sedimentary Cover Laptev Sea Concerned with Oil and Gas Content

Nikolay A. Malyshev, V. V. Obmetko, A. A. Borodulin, E. M. Barinova, and B. I. Ikhsanov
Rosneft, Moscow, Russia.

Above 17000 km of 2D seismic data from the Laptev Sea area and generalized analysis results are presented in the report. The understanding of the structure and evolution of the Laptev Sea sedimentary cover were specified basing on the reinterpretation of seismic data and geological data from onshore outcrops and wells.

Upper Cretaceous-Permian pericratonic complex of the Siberian platform is supposed to develop in the western part of the shelf. On its northern onshore part the Permian rocks overlap various formations of the Riphean up to the Carboniferous rocks. On Laptev Sea shelf Riphean and Carboniferous rocks are submerged to the depths of 12-14 km and, we suggest that it’s the part of the acoustic base. On the eastern part of Laptev shelf in the basement of the sedimentary cover there is a postorogenic Aptian-Upper Cretaceous complex which mainly composes grabens. Underlaying rocks form the folded basement in this area. At the top of the section the synrift Upper Cretaceous-Pliocene complex is spread almost everywhere. Distinctions of magnetic evidence in structure of the earth crust of the western and the eastern parts of Laptev Sea shelf are also recognized. We suppose that the boundary between it passes along Lazarev fault which is the right-hand strike slip associated with Amerasian basin development.

In the western part of Laptev Sea shelf Omolojsko-Ust-Lensky rift-system is allocated. It is a uniform large depocenter. In the south-east part of the basin narrow submeridional and northwest trending grabens and halfgrabens (Belkovsky, Svjatonossky, etc.) are generally developed. Propagation and rejuvenation of the rifting in southeast direction in Late-Cretaceous-Pliocene age is discovered, and rift axis migration to the east from the Late Cretaceous up to the present (North Laptevsky and Anisinsky troughs) is discovered as well.

The combination of aforementioned compression processes and extension movements has led to formation of transtension structures in the sedimentary cover of the western part of Laptev Sea shelf. They are traced as extended swell-form zones (flower structures), divided by narrow rigid blocks. Taking into account features of the structure, development of the sedimentary cover, and also using basin modelling technology the estimation of region prospects has been executed, shelf parts are optimum spotted for detection of hydrocarbons accumulation

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