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.

Background. The interest of many oil companies is focused on the under-discovered but highly potential prospects of arctic regions of the Enisey-Khatanga oil and gas bearing region. There are practically no other comparable oil and gas bearing regions within Russian onshore. The interest of present paper covers the area of twelve Zapadno-Taimyrsky licenses and six Nizhnepurinsky licenses which Gazprom Neft owns with opportunity for prospecting and exploration surveys on the right side of the Enisey bay. Company owns two other license areas named Leskinsky and Pukhutsayakhsky on the left side of the Enisey bay where the exploration program
has been realized since 2019.
Aim of present research is to assess the prospects of oil and gas potential of the Paleozoic series of the West Taimyr that represented by Ordovician, Silurian, Devonian and Carboniferous deposits based on new geological data.
Materials and methods. The assessment of the Paleozoic resources prospects was held based on the result of pre-stack time migration reprocessing of the entire set of available 2D seismic surveys, drilling results of first exploration well, results of geochemistry data analysis, core data description and petrophysical results of laboratory test accomplished with paleoreconstructions and other regional data considered as primary methods of research.
Results. Complex approach for available geological data analysis makes possible to identify main oil and gas prospects of the Paleozoic series and highlight the driver of the project. All elements of petroleum system were defined and estimated for each complex such as a potential source rock, the intervals of carbonate reservoirs, regional and local seals, traps and preservation. The influence of dissolution, fracturing and other diagenetic processes on the formation of void space were evaluated.

Background. Nowadays, West Taimyr as a part of Enisey-Khatanga trough is considered to have a highly potential petroleum play which lead to arising exploration interest of Gazprom Neft. The first exploration well was drilled on the left bank of the Enisey Bay in 2021 and reached a Middle Ordovician of the Paleozoic Series. Exploration well results significantly expanded the understanding of region’s paleogeography and depositional environment of Ordovician, Silurian and Devonian times.
Aim of present paper is to highlight the results of paleogeographic reconstructions based on drilling results and seismic data interpretation.
Materials and methods. 2D seismic data, core based sedimenthological analysis and well log interpretation were used to restore paleogeography of the studied area. Seismic correlation of main horizons VIa, VII, VII_bot, top_D1_carb, VIIa, VIIa_bot, top_O_carb, VIII allowed to map several thickness complexes for different seismic units within a stratigraphic interval from Middle Ordovician to Upper Devonian. Thickness maps together with integrated dataset of seismic, well log and core data interpretation allowed to build a base for paleogeographic reconstructions.
Results. As a result of performed paleoreconstructions, a set of paleogeographic maps of the West Taimyr potential oil and gas bearing area was prepared.
Conclusion. Performed paleoreconstructions provide a necessary basis for further exploration works within a potential oil and gas bearing area and enable geoscientists to create a new basin model.

Background. The Paleozoic sedimentary rocks of the Enisey-Khatanga oil and gas bearing region remain one of the most poorly studied depositional sequences from the margin of the Siberian craton so far. Gazpromneft is now conducting geological exploration in the western part of the region, in the area of Enisey Bay. In 2021 the first exploration well was drilled here. The well penetrated the Paleozoic series up to the Middle Ordovician deposits.
Aim. The goal of this work is to present the results of biostratigraphic studies based on the new materials of drilling.
Materials and methods. Core from well served as the basic material for the production of representative complexes of fossils. Traditional laboratory methods were used to extract fossils from sedimentary rocks and study them. All available regional data were attracted to determine the taxonomic position of fossils and their stratigraphic significance.
Results. The Darriwilian Stage of the Middle Ordovician, the undivided Sandbian and Katian Stages of the Upper Ordovician, the Telychian and Homerian Stages of the Lower Silurian, the Emsian Stage of the Lower Devonian are distinguished in the section of first exploration well as a result of conducted research. Complexes of fossils (conodonts, graptolites, Ostracoda) are given for each of the listed stratigraphic subdivisions.
Conclusions. The age of the Paleozoic units was determined as a result of biostratigraphic analysis. The stratigraphic position of regional seismic reflectors have also been clarified. Previously existing ideas about the stratigraphic structure of the Paleozoic series of the West Taimyr potential oil and gas bearing area have been significantly adjusted.

Introduction. The Paleozoic sedimentary series of the Enisey-Khatanga oil and gas bearing region has undergone a complicated geological history. Carbonate rocks composing significant volume of the strata show various traces of the secondary alterations that have both positive and negative effects on the reservoir properties of the carbonate rocks. Of particular importance in the exploration of oil and gas in carbonate depositional systems is the study of post-sedimentary changes in carbonate reservoirs and linking these changes with the stages of tectonic evolution of the region. This allows to solve the questions of reservoirs genesis and make conclusions about their spatial distribution. During the studies of the carbonate rocks in the first exploration well (Leskinsky license area on the left bank of the Enisey Bay) unique information was obtained on the composition and secondary transformations of Paleozoic carbonate reservoirs of the West Taimyr potential oil and gas bearing area.
Materials and methods. In the well the secondary dolomite reservoir rocks were described within several stratigraphic units; samples from that section were obtained for the detailed studies using a complex of instrumental methods. The samples were studied using standard optical (petrography and cathodoluminescence) microscopy, SEM-EDX, microtomography, data on stable isotope composition and thermobarometry of the twophase gas-liquid inclusions was obtained.
Results. The main intervals of the dolomite reservoirs were found in the Silurian — Lower Devonian and Emsian — Upper Devonian seismostratigraphic units (between reflecting horizons VII_bot и VIIa, VIa и VII, respectively). Silurian secondary porous and cavernous dolostones are dedicated to reef series. A system of well-connected secondary voids has formed over primary porous and well-permeable reef limestones. In the Emsian strata low-permeable limestones of shallow-deep subtidal were replaced by dolostones with separate vug porosity. Pore space here was formed due to fracturing and leaching of corals and stromatoporoid skeletons. The Upper Devonian dolostones were formed during the replacement of low-permeable microbial bindstones of the peritydal flat. For all the intervals diagenetic history was reconstructed and paragenetic diagrams were put together.
Conclusion. The results of the study of diagenetic dolomite reservoirs contain important information for predicting their distribution within the West Taimyr potential oil and gas bearing area.

Introduction. The Gydan Peninsula is located in the junction zone of three large regions — the West Siberian plate, the Enisey-Khatanga trough and the Taimyr orogen which determines the multi-stage tectonic development and the diversity of structural styles in the region.
The purpose of this paper is to update the existing ideas on the tectonic development of the studied region based on the new data obtained from the study of well on Leskinsky license area.
Materials and methods. The study was based on 2D seismic data and a detailed study of the well core.
Results. Based on a comprehensive interpretation of the data, the main stages of the tectonic evolution of the region have been established: Late Proterozoic-Early Carboniferous — passive margin of the Siberian continent; Late Carboniferous-Early Permian — Hercynian orogeny with fold-thrust belt development in the west and foredeep in the east; Early Cimmerian tectonic event — reactivation of Late Paleozoic structures, uplift and significant erosion of Paleozoic-Early Mesozoic deposits.
Conclusion. The results of the study of the well section on Leskinsky license area clarifies the age of the sedimentary cover of the northeast Gydan Peninsula and the seismostratigraphic model of the West Taimyr potential oil and gas bearing area. Based on published and new data, an updated model of the geological development of the region has been proposed.

Introduction. Silurian graptolitic shales represent a source of oil and gas in various petroleum basins of the world. They are also widely distributed in the northern Eastern Siberia within the Lena-Tunguska basin, Folded Taimyr and, probably, in the adjacent parts of the Enisey-Khatanga and West Siberian oil and gas basins. Stratigraphically, they are confined to the Llandovery deposits, although in various areas characterized by elevated sea depths (in particular, in Taimyr), they are also common in the Wenlock and Ludlow deposits.
The aim of this paper is to present the results of geochemical and coal petrographic studies performed on the basis of a new well drilling data.
Materials and methods. Graptolitic shales in the well on Leskinsky license area were drilled in the 140-m interval of the Ust`-Enisey Formation (S1ue) of the Telychian Stage of the Llandovery and the Homerian Stage of the Wenlock, Lower Silurian. Petrographic and geochemical studies, including pyrolytic, bituminological, chromatomass-spectrometry and isotope studies of samples, and their complex interpretation were carried out.
Results. Comprehensive studies of graptolitic shales made it possible to establish that they are characterized by a high content of organic matter; marine, predominantly algal, type of organic matter accumulated in suboxic, possibly, freshwater conditions; a high degree of organic matter maturity complicated by local heating in the upper part of the studied section.
Conclusions. The obtained data allow us to consider the Lower Silurian graptolitic shale units as one of the main sources of hydrocarbons in the lower part of the section of the study area.

Introduction. The article discusses the results of geochemical studies based on the results of drilling the well on Leskinsky license area, which became the basis for revising the prospects for the oil and gas potential of the region within the perimeter of the Gazprom-neft LLC projects.
The purpose of this work is to generalize the Paleozoic petroleum system regional data of the West Taimyr potential oil and gas bearing area of the Enisey-Khatanga oil and gas bearing region.
Materials and methods. According to the results of exploration drilling, a Paleozoic series were discovered up to the Middle Ordovician deposits. The source rocks of the Permian, Devonian and Silurian ages are characterized. Permian source rocks of III type and the previously unstudied Ust-Enisey formation (S1 ue) containing the organic matter of I-II type from graptolitic shales of the Llandoverian and Wenlock series of the Lower Silurian have been confirmed. Upper Devonian source rock (Domba Formation D3 dm) identified earlier in West Taimyr outcrops has not been confirmed on Leskinsky license area.
Results. The obtained data about the properties of source rocks and the results of extracts analysis of the core and cuttings made it possible to significantly revise the conceptual model of the prospects for the oil and gas potential of the Paleozoic series on the territory of the West Taimyr potential oil and gas bearing area. The maturity of organic matter was evaluated, the main erosion events were studied for the presence of catagenetic unconformities, and the extract — source rock was correlated.
Conclusions. The data obtained made it possible to revise the prospects for the oil and gas content of the Paleozoic in such regions as the Lena-Tunguska, Enisey-Khatanga oil and gas bearing regions, and the Taimyr independent potential oil and gas bearing region.

Introduction. The article presents the results of the 1D basin modeling in the territory of the West Taimyr potential oil and gas bearing area.
The purpose of this work is to generalize ideas about the development of petroleum systems in the West Taimyr potential oil and gas bearing area.
Materials and methods. As input information for building a 1D basin model, the results of drilling the first well on Leskinsky license area and geological and geochemical information on petroleum systems identified within the study area were used. The constructed model is calibrated to the actual data characterizing the thermal regime of the study area.
Results. The basin modeling technique within the territory of the West Taimyr potential oil and gas bearing area is described. The processes of hydrocarbon potential realization by the main source rocks were modeled in accordance with all available geological and geochemical information for the region.
Conclusions. The results of the study made it possible to assess the development of petroleum systems within the territory under consideration, identify the main uncertainties and outline the directions for future exploration.

The article presents for the first time the study of igneous rocks in the section of well on Leskinsky license area of the West Taimyr potential oil and gas bearing area. Fragments of igneous rocks from the Early Silurian to the Early Triassic age were studied from samples of drill cuttings and core.
Aim. Characterization of igneous rocks from the well section based on drill cuttings and core samples and interpretation of their nature and structural position in the section based on petrological and geochemical data.
Materials and method. The material was studied by electron microscopy, microanalysis and analysis of the trace elements content by mass spectrometry.
Results. Igneous rocks in the section of the well on Leskinsky license area can be interpreted as lava and dolerites re-deposited as conglomerates and gravelites in the upper part of Lower Triassic deposits, and in the lower part as lava flows overlain by a pack of conglomerates and gravelites with a thickness of 40-50 meters. Individual dolerite sills with a thickness not exceeding several meters are marked below the section in the Lower Silurian, Middle-Upper Devonian and Lower Carboniferous intervals.

Introduction. The West Taimyr potential oil and gas bearing area is one of the major Arctic exploration clusters of Gazprom Neft. The lack of comprehensive research work in this area, including hydrogeological studies, does not allow to reliably evaluate the hydrocarbon resource potential.
Aim. Analysis of hydrogeochemical research materials obtained within the Leskinskaya well drilling stage, which is a low-studied but the high potential productive region of the West Taimyr.
Materials and methods. We used an integrated solution for the complex characterization of formation water using both core and cuttings samples. The workflow includes the free and bound water content measurements by the evaporation method (EM) with isotopic analysis (δ18O and δD) of the released water and the formation of water salinity estimation using a modified method of aqueous extracts. The results of the cutting using core data were accurately verified by direct analysis of the formation water composition.
Results. For the first time, a chemical composition of the formation waters of the Mesozoic-Paleozoic deposits along the Leskinskaya well of the West Taimyr potential oil and gas bearing area was obtained.
Conclusion. The complex interpretation of the obtained results shows that there is direct hydrogeochemical zoning with the formation water total salinity increasing down the section. The upper part of the section (up to the Lower Devonian) is washed out by the surface infiltration waters. The deeper part of the section has low hydrogeological connectivity with the overlying aquifers and includes the ancient relict waters of varying degrees of metamorphization stage and with a heavier isotopic composition.

Aim. Paper presents the results of implementation “Computational Rock Physics” tool.
Materials and methods. As a pilot program, core samples from Kharyaga carbonate D3-III were investigated and tested with the tool. One of the main advantages of using this tool is that it is less time consuming compared to laboratory tests. This becomes more obvious when core has permeabilities of 1mD or even less. In laboratory in can take from 1 to 3 months to estimate relative permeabilities or displacement coefficient, compared to desktop calculation — depending on CPU from 1 to 10 days. Another possible advantage of the tool is lower costs for one experiment. General procedure in applying tool is done in two steps: first one, initially samples go through high-resolution tomograph, second step, with application of the tool, relative permeabilities and displacement coefficient are calculated.
Results. This paper shows following calculations/injection schemes performed: injection of surfactant/polymer composition in oil saturated sample, injection of surfactant/polymer analogue composition in oil saturated sample, injection of gas in oil saturated sample. Attempt was made to compare achieved results with laboratory data, however it has some limitations.
Conclusions. Next step in developing technology is to include such options as: connate water saturation set up, simultaneous calculation for 3 phases — air, gas and water, miscible gas injection (CO2).