Regional Palaeogeography and Implications for Petroleum Systems, Severnaya Zemlya

The Severnaya Zemlya Archipelago and the adjacent Barents-Kara-Laptev Region of the Arctic Shelf is a frontier hydrocarbon province with proven and predicted large hydrocarbon accumulations recognized in different hydrocarbon plays. However, despite renewed geological and geophysical investigations during the last decades, many aspects of the geological history of this region, including petroleum geology, are still unclear, as constraints from actual data are generally absent. This paucity of data also compromises attempts to reconstruct the palaeogeography of this region. Most published maps covering the geological history of the Russian Arctic start from the Devonian Period. Palaeogeographic reconstructions for earlier period are sketchy, controversial and out of date. Exploration for hydrocarbons requires a detailed understanding of the spatial and temporal distribution of source and reservoir facies and their position within the regional palaeogeographic framework. Palaeogeographic maps, are therefore an important tool for predicting reservoir quality and distribution in frontier areas.

As part of the CASP’s work on Severnaya Zemlya, a regional reassessment of the early to middle Palaeozoic palaeogeographic evolution of Severnaya Zemlya has been undertaken, the results of which are outlined here.

A set of 29 maps spanning the Cambrian to Devonian have been produced, which synthesise the available published data and incorporate new data obtained from field work carried on Severnaya Zemlya by the authors. The study was carried out using ArcGIS allowing the user to interactively browse depositional environment over time, as well as the location of primary lithology and other observations.

The maps show that Severnaya Zemlya belongs to a single sedimentary basin with a general trend of deepening towards the north-west. During the early and middle Palaeozoic Severnaya Zemlya was dominated by shallow marine environments with carbonate and clastic deposition. The major Telychian transgression in the basin led to formation of organic-rich source rocks. The presence of salt diapirs north-west of Severnaya Zemlya interpreted from the seismic lines is in agreement with the reconstructed palaeogeography. The age of salt deposits is thought to be Late Ordovician (Malyshev et al. 2013), however they could also be Middle Ordovician and Devonian as well. Combined with the on-shore data, the evaporite basin seems to cover a large territory. Marine sedimentation came to the end in the Late Devonian with the development of a widespread hiatus/unconformity. Elevated areas along the south-eastern margin provided source material for clastic sedimentation.