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Geological Development and Hydrocarbon Potential of the Yenisei-Khatanga Trough, Russian Arctic

Graham Blackbourn and Moira Thomson
Blackbourn Geoconsulting, Carriden, United Kingdom.

The Yenisei-Khatanga (Y-T) Trough, 900 x 300 km in extent, is a northeastern extension of the West Siberia Basin, between the Taimyr Peninsula to the north and the Central Siberian Platform to the south. To the east is the Gulf of Khatanga on the Laptev Sea. Its history is not clearly documented and it is underexplored; this study aims to unravel its geological development and assess more fully its prospectivity.

The basement of the Y-T Trough records a long and complex series of accretional events on the northern margin of the Siberian Platform. Precambrian to Permian successions accumulated on its flanks. The Trough was initiated at the Permo-Triassic boundary as an eastward-propagating rift associated with supposed mantle-plume activity beneath the northern part of the West Siberian Basin. Trap basalts infill deep rift structures in the west.

Thermal subsidence continued throughout the Mesozoic, leading to deposition of a mainly conformable marine clastic succession, with most facies changes and disconformities associated with variations in sea level. The succession dips gently away from the basin margins, and is relatively unfaulted. Partial reconstruction of the Trough during the early Neocomian, associated with closure of the South Anyui ocean to the east (creating the Verkhoyan-Olenek fold belt) led to development of an en-echelon chain of highs (the Malaya Kheta-Rassokha-Balakhnya arches), with ENE-WSW to NE-SW orientation, oblique to the axis of the Trough, with erosion of previously deposited Jurassic sediments on the crests of the arches, and the creation of several separate depocentres (the Nosok, Agapa and Zhdanikha troughs).

Subsidence ended at the close of the Mesozoic with a period of slight uplift and peneplanation. There are no significant Tertiary deposits, and in most places the Cretaceous is overlain by a thin Quaternary veneer.

Much of the Jurassic, and the Lower Cretaceous within deeper parts of the Trough, entered the oil window before the end of the Mesozoic. Oil-prone source rocks are sparse, although gas has been generated and has accumulated in Mesozoic (mainly Early Cretaceous) reservoirs around the Trough margins, and on the arches which transect it where reservoirs are intact. More gas accumulations could be discovered in anticlinal and fault-related traps if a denser seismic grid were shot. There is some potential for oil, but major discoveries are regarded as unlikely.

 

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