Lithological and sedimentological characteristics of the Paleozoic of the West Taimyr potential oil and gas bearing area (according to drilling data)

Background. Until now, the Paleozoic sedimentary complex of the western part of the Enisey-Khatanga oil and gas bearing region remains poorly studied. Most often, data from adjacent tectonic regions are used to interpret its lithological structure and depositional history, which leads ones to doubt the reliability of forecast. The results of drilling well at the Leskinsky license block near the Enisey Bay provide unique information on the lithology and sedimentology of the Paleozoic of the West Taimyr potential oil and gas bearing area.
Materials and methods. During drilling of first exploration well, cores were taken in the intervals of several paleozoic seismic complexes. Sedimentological analysis was performed on the core column. Core samples were taken for studies of lithological and mineralogical features of rocks. The complex of laboratory studies included such methods as: standard optical microscopy (petrography), determination of calcite and dolomite content by volumetric method, XRD, XRF, thermogravimetric analysis. In addition, rock studies were performed using сathodoluminescence petrography and SEM-EDX.
Results. Facies of the mixed-siliciclastic-carbonate ramp are identified in the Middle Ordovician. They are represented by rhythmic alternation of carbonate-terrigenous-clay and carbonate rocks with frequent interbeds of carbonate tempestites. Deep-sea graptolitic black shales with a high proportion of organic material are identified in the Llandovery Series of the Lower Silurian. Higher in the Silurian System, a progradation sedimentary sequence from the toe of the slope to the upper part of the reef slope is identified. Rocks at the toe of the platform slope are represented by siliceous limestones with characteristic signs of slope sedimentation — carbonate turbidites, debrites and convolute bedding (slump deposits). Rocks of the upper part of the reef slope are represented by cavernous-porous secondary dolomites with relics of skeletons of reef builders. In the Emsian Stage of the Lower Devonian, secondary dolomites with caverns and cavities are identified. The supposed Upper Devonian interval is represented in the well by facies of the inner zone of the rimmed carbonate platform — limestones and dolomites of the lagoon and peritidal.
Conclusions. As a result of the studies, unique information was obtained on the lithological structure of Paleozoic sedimentary rocks and their accumulation conditions.

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