The Overview of Geology and Hydrocarbon Systems of North Kara Basin

Dmitry Komissarov

It is widely believed that North Kara shelf represents one of the most prospective Arctic regions for hydrocarbon (mostly oil) discoveries. But the Kara region is characterized by a very low exploration maturity. For this reason, the interpretation of the geological structure of the shelf of North Kara Sea is a problem to restore the geodynamic history and to determine the hydrocarbon prospects of the region. The problem of the sedimentary cover stratigraphy cannot be solved unique and suppose different options of interpretation. It is very important for subsequent basin modeling to understand hydrocarbon systems of region. Our approach is based on the reinterpretation of several regional seismic lines. We used the main Paleozoic and Mesozoic tectonic events known for Severnaya Zemlya Archipelago and Taimyr Peninsula for interpretation of the age of main seismic complexes and unconformities within the North Kara sedimentary cover. We correlated the sharp angular unconformity in the lower part of sedimentary succession with Cambrian/Ordovician unconformity described earlier on the Severnaya Zemlya onshore domain. It is likely that the pre-Ordovician tectonic event is roughly coeval with the Timanian orogeny. Just above the unconformity we proposed the occurrence of Ordovician-Silurian shelfal sedimentary sequence of ~ 2 km thickness. This strata are overlain by thick (~3-4 km) progradational unit. This sequence should correspond to molassic deposits of Old Red sandstones, related to the regional Caledonian orogeny. We believe that general structural pattern of the North Kara region was formed in Late Carboniferous-Early Permian time as a result of Kara massif/Siberian Craton collision-related Hercynian orogeny of Taimyr-Severnaya Zemlya domain. This event led to gentle folding of the main sedimentary infill of the basin. The deformed Paleozoic strata of the North Kara basin are unconformably overlain by thin post-orogenic Upper Permian(?)-Mesozoic beds. We found almost no evidence for the Mesozoic contractional deformation events known for adjacent Taimyr fold belt. From the other hand we proposed the existence of small transtensional pull-apart basins, superimposed on the Hercynian unconformity coeval with those known for Taimyr fold belt. It is also notable that we did not find any evidence of the existence of deep rift-related troughs filled by Riphean-Cambrian rocks, which were proposed by previous researchers. Nevertheless the occurrence of the Ordovician regional post-orogenic extensional basins is not excluded. Based on the results of seismic data re-interpretation and tectonostratigraphic model the regional forward stratigraphic (sedimentatological) simulation was carried out to predict the stratigraphic architecture and spatial distribution of facies. The subsequent basin modeling results showed that North Kara region may represent highly prospective, but mostly gas-bearing basin due to the high maturity of Lower Paleozoic source rocks.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013