Bazhenov Formation Research Articles

Features of the geological structure of the Achimov complex of the Yarudeisky megaswell (Western Siberia)

This work is devoted to the peculiarities of sedimentation and geological structure of clinoform deposits of the Yarudeisky megaswell (Western Siberia). The main feature of the clinoforms under consideration is that the sediments are confined to the marginal regional clinocyclite of the western dip of the area of oncoming clinoforms, formed in relatively shallow sea conditions and differing from deep-sea clinoforms by pinching out not onto the Bazhenov formation or the early underlying clinoforms of the western dip, but by stopping their spread along the path of movement of the oncoming clinoforms eastern dip. The study of the counter clinoforms of the Yarudeisky megaswell is based on a regional analysis of the structure of cross-layered deposits in conditions of extremely poor knowledge of the study area. Within the framework of western dipping clinoforms, possible oil and gas potential prospects for the Achimov complex within the boundaries of the Yarudeisky megaswell are identified. As a result of the analysis of geological and geophysical data, the boundaries of the distribution of opposing clinoform complexes in the study area were determined. The existing paleo-geomorphological conditions that contribute to the accumulation of sandstone with improved properties in the designated seismic complexes are presented. The fields of the Nadym oil and gas bearing region with the proven productivity of the Neocomian clinoform complex are indicated, which confirms the oil and gas potential of the region and suggests favorable conditions for the accumulation of hydrocarbons in the study area.

First Results of U–Th/He Dating of Epigenetic Pyrite from Rocks of the Bazhenov Formation, Western Siberia

The U–Th/He method has been applied for the first time to determine the age of epigenetic pyrite from the oil source rocks of the Bazhenov Formation, Western Siberia. The possibility to date the post-sedimentation processes in a sedimentary basin by authigenic pyrite using the U–Th/He method is shown. The U–Th/He isochrone age of pyrite (n = 7) from the dolomites of the Bazhenov Formation within the Frolovskaya megadepression is much younger than the sedimentation age and corresponds to the Santonian–Cenomanian stages of the Upper Cretaceous (90 ± 8 Ma).

Differentiation of the Bazhenov Formation Bitumoids in the North-Surgut Region during Generation and Migration

Abstract —The Bazhenov Formation of the Western Siberian oil-and-gas province is currently one of the key objects of potential growth in oil reserves and production. Here we present results of a geochemical study of the Bazhenov Formation according to the methodology developed at Trofimuk Institute of Petroleum Geology and Geophysics, Novosibirsk (IPGG SB RAS) for rocks highly enriched in organic matter. The features of the group and hydrocarbon compositions of the bitumoids that are filling open and closed pores of the Bazhenov Formation rocks from the North-Surgut region were considered. It has been established that most of the naphthides are in a free (phase-segregated) or sorbed state in a closed pore space. The open pores contain the most mobile components of bitumoids, redistributed from closed pores during the primary migration and remained after the secondary migration of naphtides from the Bazhenov Formation to the Berriasian–lower Aptian reservoirs (A and B strata groups). The methodology used in this work allows determining intervals with increased open porosity and oil saturation in the section of the Bazhenov Formation (silicites and carbonates) by the volume of pore space occupied by open-pore bitumoids.

REVIEW AND CRITICAL ANALYSIS OF THE CURRENT STATE AND WAYS OF DEVELOPING THE TECHNOLOGICAL PROCESS OF OIL PRODUCTION BY AN ELECTRIC DRIVE IN INTERMITTENT MODES OF OPERATION OF LOW- AND MEDIUM-RATE WELLS

Link for citation: Kladiev S.N. Review and critical analysis of the current state and ways of developing the technological process of oil production by an electric drive in intermittent modes of operation of low- and medium-rate wells. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 8, рр. 220-231. In Rus. Relevance. The Russian Federation is one of the world leaders among oil-producing countries in terms of proven oil reserves. Historically, industrial oil production in the Russian Empire began in the area of the Caspian Sea on the territory of modern Azerbaijan. The energy strategy of the Russian Federation for the period up to 2035, as one of the measures to ensure the energy security of the country, provides for the introduction into economic circulation of hard-to-recover oil reserves (including from the Bazhenov formation) based on innovative domestic technologies and equipment. The main problem of the oil industry in Russia, as well as throughout the world, is the decline in the quality of the resource base. In oil-producing regions, there is a depletion of active oil reserves. Significant residual reserves of developed fields are expected to be brought into active exploitation using new oil production technologies. Ways of growth in oil production are possible in accordance with three different scenarios: innovative – it is supposed to increase the contribution to the total indicators of Russian oil production from new provinces, such as Eastern Siberia, the Republic of Sakha (Yakutia), as well as new fields in Western Siberia and the Krasnoyarsk Territory and the development of the shelf northern seas; forced scenario – in case of more active introduction of new technologies and incentive measures that reduce the cost of the production process, it is possible to increase the efficiency of oil production in offshore and hard-to-recover fields; extensive scenario of oil production is possible only at high market prices for oil. The main volume of production is carried out and will continue to be exclusively electrically driven. The purpose: a review and critical analysis of the current state and ways of developing the technological process of oil production by an electric drive in intermittent modes of operation of low- and medium-rate wells. Object: theoretical substantiation of the introduction of cyclic or short-term operation of electric centrifugal pump installations with an electric drive method of downhole oil production into practice. Methods: geophysical research to develop a concept for the operation of a marginal well stock, ways to increase the profitability of oil production, methods for optimizing the stock of medium and marginal wells, putting them into economic circulation. Results. Based on a critical analysis of literary sources and a feasibility study, it is shown that the most promising way to extract hard-to-recover oil reserves on the example of the Bazhenov formation is the electric drive of a submersible centrifugal pump according to the scheme «ground power converter – submersible cable – submersible electric motor – electric centrifugal pump». The technology of cyclic operation of wells in oil production shown that it is economically feasible for low- and medium-rate wells and is widely implemented in wells that cannot be operated in a continuous mode.

A model of a shear landslide wedge with subsequent hydraulic rupture as an explanation for the formation of an anomalous section of the Bazhenov formation in the north of Western Siberia. Part 2. Description of the mesostructural complexes in the core and the model of the anomalous section formation

A new anomalous section of the Bazhenov formation was described on the territory of the Urengoydeposit in the northern part of Western Siberia. This article presents descriptions of mesostructural complexes in the core, on the basis of which a new model for the formation of the anomalous section of the Bazhenov formation was proposed. It was found that the formation of the mesostructural complexes occurred at different stages of the landslide and when its body moved along the uneven surface of the detachment. In the formation of large injection “sand veins” in the studied section, the main role was probably played by the landslide-induced grain flow from the coastal shallow water area. The penetration of its sandy material into the rocks of the Bazhenov formation and, to a lesser extent, the Achimov formation occurred due to the energy of hydraulic shock and hydraulic fracturing along layer-by-layer and secant fractures.

A Model of a Shear Landslide Wedge with Subsequent Hydraulic Rupture as an Explanation for the Formation of an Anomalous Section of the Bazhenov Formation in the North of Western Siberia. Part 2. Description of the Mesostructural Complexes in the Core and the Model of the Anomalous Formation of the Section

A Model of a Shear Landslide Wedge with Subsequent Hydraulic Rupture as an Explanation for the Formation of an Anomalous Section of the Bazhenov Formation in the North of Western Siberia. Part 2. Description of the Mesostructural Complexes in the Core and the Model of the Anomalous Formation of the Section

Гидротермально изменённые породы – индикаторы зон разгрузки углеводородов Красноленинского свода (Западная Сибирь)

Our own research data as well as numerous publications of recent years on modern problems of oil potential in the West Siberian oil and gas province were used in this study. Based on the Palyanovskaya, Talinskaya and adjacent areas of the Krasnoleninsky arch, the issues of deposits structure and confinement to certain regional levels of the section, the problems of unconventional reservoirs formation in the zones of tectonic deformations and hydrothermal-metasomatic changes in pre-Jurassic basement rocks (Paleozoic granites), as well as problems of highly permeable “supercollector” (the lower horizons of the Jurassiccomplex – Sherkalinskaya formation) and an almost impermeable reservoir with difficult to recover huge hydrocarbon reserves (its upper horizons – Bazhenov formation) are discussed. The oil deposits distribution in the Jurassic part of the section was shown to comply with the fluid migration model with the participation of deep hydrocarbon fluid. New types of unconventional reservoirs have been identified in the basement granites and in the unloading zones in the Jurassic deposits of the sedimentary cover.

Geological structure and occurrence conditions of the Bazhenov formation within THE South Tambey gas condensate field

Background. In the 21st century, exploration works in the previously discovered Jurassic deposits has been launched in the north of the Yamal Peninsula. The South Tambey field was no exception, where 3D seismic surveys and exploration drilling have been carried out over the past 10 years to study of Jurassic sediments and rocks of the Bazhenov formation. Due to the lack of a data sufficient sample in the northern regions of the Western Siberia, formation was poorly studied. The main ideas were formed on wells scattered at great distances from each other without the possibility of a clear correlation. After receiving new drilling materials, it became possible to examine the deposits of the Bazhenov formation in more detail.Aim. Determination of the structural features and occurrence conditions of the Bazhenov formation.Materials and methods. The research was based on the logging data of exploration and production drilling. A detailed correlation of well sections was performed, which was compared and analyzed with the core description and interpretation of seismic survey materials.Results. The lithological characteristics of rocks obtained by core description are presented, the atypical neighborhood of stromatolites and radiolarians in the section is noted. Based on a detailed correlation, the Bazhenov formation was divided into three intervals with characteristic geophysical logging values and distribution features over the area. The clinoform occurrence with development in the north-west direction is determined. Based on the areal variability, it is proposed to distinguish two types of the Bazhenov formation, and approaches to their tracing are considered.Conclusion. The study of the Bazhenov formation revealed a co-directionality of the spatial orientation of the faults, the progradation of the Achimov clinoforms, and changes in the thickness of the Bazhenov formation. A hypothesis has been put forward about a single tectonic regime that prevailed in the Upper Jurassic and Lower Cretaceous. It is proposed to consider flower (keyboard) tectonics as the main factor that determined the structure and occurrence conditions of the Bazhenov formation.

A model of a shear landslide wedge with subsequent hydraulic rupture as an explanation for the formation of an anomalous section of the Bazhenov formation in the north of Western Siberia. 1. Section description, lithology, palynology

А new anomalous section of the Bazhenov formation was described in the territory of the Urengoy oil and gas condensate field in the northern part of Western Siberia. Article 1 presents the results of the lithological description of the core, the division of the main rocks into lithotypes, the results of granulometric and palynological analyzes. It was revealed that gray-colored sandy-clay deposits and sandy vein-like bodies are younger than the host rocks of the Bazhenov Formation, represented by black kerogen-siliceous-clay rocks. On the basis of palynological studies, as well as the similarity of the mineral and granulometric compositions of the studied sandstones with the sandstones of the Achimov strata, it was assumed that the studied clastic rocks belong to the Achimov deposits, which were intruded into the deposits of the Bazhenov Formation.

A Model of a Shear Landslide Wedge with Subsequent Hydraulic Rupture as an Explanation for an Anomalous Section of the Bazhenov Formation in the North of West Siberia. Article 1. Section Description, Lithology, and Palynology

A Model of a Shear Landslide Wedge with Subsequent Hydraulic Rupture as an Explanation for an Anomalous Section of the Bazhenov Formation in the North of West Siberia. Article 1. Section Description, Lithology, and Palynology

Development of a Zonal Model for Forecasting the Oil and Gas Potential of the YUS1 Formation by Geochemical Parameters

The distribution of geochemical properties of rocks of the Bazhenov Formation (BF) by area and section has been refined, regularities have been searched, and conclusions have been obtained that have predictive power. Due to the high cost of continuous core sampling and pyrolysis of samples from BF intervals, the fragmentation and heterogeneity of the accumulated information, as well as the high value of knowledge about the oil-generating properties of BF rocks and their changes over the area, there is a need to increase the information content of the database of geochemical core studies and adapt its application in conditions of limited data. To solve this problem, a database of results of geochemical studies was collected and analyzed, consisting of 5272 samples from 123 wells of 32 fields. As a result of the analysis, conclusions were obtained about the oil-generating properties of BF within the study area and the degree of maturity of the organic matter of the rock. Two regression models were developed to predict the geochemical parameters of free hydrocarbon content, residual generation potential and total organic carbon from well logging data. An algorithm was implemented in the Python programming language to automate the calculation process. Using this algorithm and the resulting regression equation, the calculation of geochemical parameters was carried out in 390 wells in the study area that were not presented by core data, which significantly increased the detail and information content of predictive maps of the distribution of parameters over the area. Using the data obtained, a geological and mathematical model was developed for predicting oil content by geochemical parameters. The developed model reflects the probability of oil content depending on the oil source properties of the rocks of the Bazhenov formation in the study area. The developed forecast model included the parameters of the organic carbon content in the rock, the current reservoir temperature and the thickness of the rocks of the Bazhenov formation.

Wellbore Stability in the Bazhenov Formation Considering the Anisotropy of Elastic Properties of Composing Strata

Wellbore Stability in the Bazhenov Formation Considering the Anisotropy of Elastic Properties of Composing Strata

Problems of oil and gas potential realization in Bazhenov-Abalak play in Khanty-Mansi Autonomous Okrug – Yugra

This research aims to analyze problems related to resources, reserves and development of Bazhenov-Abalak oil and gas play and to find geological and technological solutions for bringing reserves into development commercially. This should stabilize oil production in Okrug on the level 210–215 million of tons. Geological, field and statistical data from V.I. Shpilman Research and Analytical Centre for the Rational Use of the Subsoil and Department of Subsurface Management & Natural Resources of Khanty-Mansi Autonomous Okrug – Yugra were retrospectively analyzed during this research. Oil production from Bazhenov-Abalak play using conventional technologies is still sub economic. Running experimental areas and test ranges for industrial approval of development efficiency enhancement technologies for Bazhenov-Abalak play are created on producing fields. Unfortunately, accumulated experience ends up inside oil companies. Undoubtedly, single initiatives of oilmen will not solve a problem of development of huge resources in Bazhenov formation.

Loading diagrams and parameters of the model of elastic-pseudoplastic deformation of black shale rocks of the Bazhenov formation

The results of the analysis of experimental data on pseudotriaxial loading of full-size samples of black shale rocks of the Bazhenov Formation are presented. The experiments were carried out under conditions of uniaxial loading and at lateral compression pressures of 20 and 40 MPa. It is shown that in the considered load range, the deformation of the rock beyond the elastic limit proceeds in different modes: dilatancy and compaction. Despite the low porosity of the rock, the transition from dilatation to compaction occurs at a pressure not exceeding 34 MPa. Based on the analysis of the obtained data, the stages of deformation in the loading diagrams are distinguished and the parameters of the mathematical model with a combined limiting surface are determined, which describes the deformation process in dilatancy and compaction modes.

Wellbore Stability in the Bazhenov Formation Considering the Anisotropy of Elastic Properties of Composing Strata

This paper offers a general approach to the modelling of the wellbore stress state in the Bazhenov formation. In modelling, strata are presented as transversely isotropic objects with a set direction of the anisotropy axis that does not coincide with the vertical line. The paper also presents results of the laboratory Bazhenov formation core analysis. The analysis of core materials yielded correlation dependences for reconstructing stress-strain parameters of a transversely isotropic medium in selected wells. Parameters of the rock anisotropy were analyzed on the basis of standard and non-standard laboratory tests. The solution of the stress state problem in a deformation bounded medium was used to suggest an algorithm of calculating the components of the regional stress state along the well path. RN-SIGMA software tools were used to construct borehole stability models for wells penetrating anisotropic rocks. The effect of the anisotropy of elasticity on a safe drilling mud density window is demonstrated. The results of the calculations show that the anisotropy effects are crucial for calculating a safe drilling window. Examples are given to demonstrate potential effects of the anisotropy in image interpretation as well as in selecting horizontal wellbore drilling directions.

Evaluation of Mineralogical Composition and Organic Matter Content of Oil Shales by IR Microscopy

Sedimentary rocks with different contents of organic matter (oil shales of the Bazhenov Formation and sandstones of the Tyumen Formation) from the West Siberian oil and gas province were used to demonstrate the simultaneous study of the mineralogical and structural-group composition, as well as semi-quantitative evaluation of mineral and organic matter contents in rocks by Fourier transform infrared (FTIR) microscopy. The following bands characterizing the stretching vibrations were used: Si–O and Al–O–Si of clay minerals (990–1090 cm–1), Si–O–Si of quartz (798 cm–1), CO2−3 of carbonates (1460 cm–1), as well as aliphatic C–H stretch (2800–3000 cm–1) and C=C ring stretch (1600–1650 cm–1) of organic matter. The obtained results are in good agreement with data obtained by traditional methods of bulk rock analysis: programmed pyrolysis, X-ray diffraction (XRD), and X-ray fluorescence (XRF) analyses. FTIR-ATR (attenuation total reflection) microscopy also provides the possibility of the distribution analysis of sample surface with color mapping, demonstrating the heterogeneity of the rock composition using the Bazhenov Formation as an example of unconventional reservoir. In addition, the method makes it possible to estimate the organic matter maturity and the rock residual generation potential based on the ratio of stretching band intensities of aliphatic and aromatic fragments.

Numerical Simulation Study of Huff-n-Puff Hydrocarbon Gas Injection Parameters for Enhanced Shale Oil Recovery

Gas injection has already proven to be an efficient shale oil recovery method successfully tested all around the world. However, gas-enhanced oil recovery methods have never been implemented or tested for the greatest Siberian shale oil formation yet. This article proposes numerical simulation of a hydrocarbon gas injection process into a horizontal well with multiple hydraulic fractures perforating Bazhenov shale oil formation in Western Siberia characterized by ultra-low permeability. A complex field-scale numerical study of gas injection for such a formation has never been performed before and is presented for the first time in our work. The hydrodynamic compositional simulation was performed utilizing a commercial simulator. A sensitivity study for different operating parameters including cycle times, bottom-hole pressures for the production and injection period, and injected gas composition was performed after the model was history matched with the available production data. Some uncertain reservoir properties such as relative permeability curves were also sensitized upon. Two different ways of accounting for multiple hydraulic fractures in the simulation model are presented and the simulation results from both models are compared and discussed. Eventually, huff-n-puff injection of a hydrocarbon gas resulted in a 34–117% increase in oil recovery depending on the fracture model.

Case Studies and Operation Features of Long Horizontal Wells in Bazhenov Formation

Summary In this study, unique field data analysis and modeling of operating wells with an extended horizontal wellbore (HW) and multistage hydraulic fracturing (MHF) in the Bazhenov formation were conducted. Moreover, a large amount of long horizontal well data obtained from the Bazhenov formation field was used. Wells with extended HW drilling and MHF are necessary for commercial oil production in the Bazhenov formation. Problems can occur in such wells when operating in the flowing mode and using an artificial lift at low flow rates. This study aimed to describe the field experiences of low-rate wells with extended HWs and MHF and the uniqueness of well operations and complexities. It was also focused on modeling various operation modes of such wells using specialized software and accordingly selecting the optimal downhole parameters and analyzing the sensitivity of fluid properties and well parameters to the well flow. The flow rates in wells with extended HW and MHF decrease in the first year by 70–80% when oil is produced from ultralow-permeability formations. Drainage occurs in a nonstationary mode in the entire life of a well, leading to complexities in operation. A comprehensive analysis of field data [downhole and wellhead pressure gauges, electric submersible pump (ESP) operation parameters, and phases’ flow rate measurements] and fluid sample laboratory studies was conducted to identify the difficulties in various operating modes. For an accurate description of the physical processes, various approaches were used for the numerical simulation of multiphase flows in a wellbore, considering the change in the inflow from the reservoir. The complexities that may arise during the operation of wells were demonstrated by analyzing the field data and the numerical simulation results. The formation of a slug flow in low flow rates in a wellbore was caused by a rapid decline in the production rate, a decrease in the water cut, and an increase in the gas/oil ratio (GOR) over time. Based on the results, proppant particles can be carried into the HW and thereby reduce the effective section of the well in case of high drawdowns in the initial period of well operation. Consequently, the pressure drops along the wellbore increased, and the drawdown on the formation decreased. Other difficulties were determined to be associated with the consequences and technologies of hydraulic fracturing (HF). These effects were shown based on the field data and the numerical simulation results of the flow processes in wells. In addition, corrective measures were established to address various complexities, and the applications of these recommendations in the field were conducted.

Combining pyrolysis and molecular parameters to improve reliability of assessment of Organic Matter maturity level in Bazhenov Formation (north-western part of Khanty-Mansi Autonomous Okrug – Yugra)

Combining pyrolysis and molecular parameters to improve reliability of assessment of Organic Matter maturity level in Bazhenov Formation (north-western part of Khanty-Mansi Autonomous Okrug – Yugra)

УРАН И ТОРИЙ В СИСТЕМЕ ВОДА – ПОРОДА (НА ПРИМЕРЕ НЕФТЕГАЗОНОСНЫХ ОТЛОЖЕНИЙ СЕВЕРНЫХ РАЙОНОВ ЗАПАДНОЙ СИБИРИ)

The paper presents the first data on the distribution of uranium and thorium in the underground waters of Mesozoic sediments of northern regions of the West Siberian oil and gas basin. The studied waters are very diverse in chemical composition and the amount of total mineralization (from ultrafresh to weak brines). The contents of natural radionuclides vary in a wide range (mg/cu dm): U (4,90•10–7–5,14•10–3), Th (1,90•10–6–8,93•10–3). The Th/U ratio varies from 0.07 to 93.1 and its maximum values characterize the waters of the Valanginian aquifers. The Th/U ratio in water – resistant rocks is in a rather narrow range, it amounts to 1.82–5.24, with an average of 3.56. Against this background, rocks of the Bazhenov Formation are distinguished by the lowest values of Th/ U = 0.07–1.71, its nature of radioactivity is associated with uranium. The formation of the radionuclide composition of underground waters of oil-and-gas-bearing deposits with high Th/U ratios took place in a sharply reducing medium, where thorium has a greater migration capacity than uranium. The evolution of the sedimentary rock basin has led to the widespread development of erosion processes and the redistribution of U and Th in the water-rock system.