Volga-Ural Province Research Articles

Fluid-Loss Control Technology: From Laboratory to Well Field

Effective fluid-loss control in oil wells is a critical concern for the oil industry, particularly given the substantial reserves situated in carbonate reservoirs globally. The prevalence of such reservoirs is expected to rise with the slow depletion of hydrocarbons, intensifying the need to address challenges related to deteriorating reservoir properties post well-killing operations. This deterioration results in significant annual losses in hydrocarbon production at major oil enterprises, impacting key performance indicators. To tackle this issue, this study focuses on enhancing well-killing technology efficiency in carbonate reservoirs with abnormally low formation pressures. To address this issue, the authors propose the development of new blocking compositions that prevent the fluid loss of treatment fluids by the productive reservoir. The research tasks include a comprehensive analysis of global experience in well-killing technology; the development of blocking compositions; an investigation of their physico-chemical, rheological, and filtration properties; and an evaluation of their effectiveness in complicated conditions. The technology’s application in the oil and gas condensate fields of the Volga-Ural province showcases its practical implementation. This study provides valuable insights and solutions for improved fluid-loss control in carbonate reservoirs, ultimately enhancing well performance and hydrocarbon recovery.

Geochemical properties of the upper devonian deposits (Semiluk, Mendym and Kynovian horizons) of the Volga-Ural province for improving the Romashkinskoye oil field development efficiency

This paper presents the results of geochemical and petrophysical studies of the Semiluk-Mendym (Domanik) and Kynovian deposits of the Frasnian age of the Devonian system at the Romashkinskoye giant oil field of the Republic of Tatarstan. The biomarker composition of the organic matter of the rocks is shown, its catagenetic maturity and facies conditions of its formation are assessed. In addition, the composition of saturated biomarkers (alkanes, steranes, and triterpanes) of Devonian oils were studied. The correlation «oil-organic matter of rocks» was carried out for oils of the Domanik and Kynovian horizons. It is shown that the differences in the biomarker composition of oils from the Domanik and Kynovian horizons are of practical importance in the field development process, since this allows optimizing the oil production process by evaluating the contributions of oil inflows from different reservoirs. Keywords: Domanik deposits; oil geochemical research; biomarkers; alkanes; terpanes.

Development of methods for increasing oil recovery of hard-to-recover reserves of the Romashkinskoe field

The article discusses the method of petrophysical research, which was developed at the beginning of the XXI century. The study provides data related to the study of the Volga–Ural oil and gas province. Using the example of the Romashkinskoe field, it is shown how the use of petrophysical characteristics made it possible to clarify the interpretation of geophysical studies of wells. The conclusion is made about the relevance of using this method in analyzing the state of mineral reserves in the deposits of the Volga-Ural province.

Oil Potential Prospects of Domanik sediments in the North-East of the Volga-Urals

Due to the depletion of available mineral and raw material resources of conventional sediments there is a need to search for new promising areas of oil and gas exploration in Perm Krai. This article addresses Domanik sediments as a new source of hydrocarbons. Stratigraphically, these sediments belong to the Sargayev, Domanik and Mendym horizons and lithologically they are mainly represented by tight carbonate sediments and shales. These sediments are the main oil-source strata in the Volga-Ural province. The paper analyses the geological structure and distribution of these sediments in the study area. Thereupon, exploration recommendations have been formulated for the next few years. These mainly include subject-matter research, core sampling in the Domanik Formation sediments, special studies of reservoir properties, reactivation and study of discovered oil deposits in the Domanik strata. The main activities should be concentrated in the south and south-west of Perm Krai: in the area of the Bashkir Arch, in the south of the Upper-Kama Depression. The Solikamsk Depression is also of interest in this respect.

Geoecological features of enhanced oil recovery methods and the effectiveness of application in the oil fields of the Volga-Ural province

Geoecological features of enhanced oil recovery methods and the effectiveness of application in the oil fields of the Volga-Ural province

Extraction concentrating of the acid-soluble forms of rare earth elements from oils of the Volga-Ural oil and gas province using rotating coiled columns

Trace elements in oils are the natural markers of the oil origin of and the mechanism of oil genesis. Direct determination of rare earth elements (REE) in crude oils is rather difficult due to their low concentrations (10–6 wt. %). Information about the forms of trace elements in oils is of particular interest. The goal of the study is determination of the content of acid-soluble forms of REE in oils from various fields of the Volga-Ural oil and gas province. Six samples of oils of heavy and medium density and viscosity were analyzed. Extraction of acid-soluble forms of REE was carried out using rotating coiled columns in 0.5 M aqueous solution of nitric acid. Toluene was used to dilute the oils up to the necessary values of the density and viscosity providing the possibility of extraction in the system aqueous acid solution – oil. The content of REE was determined by inductively coupled plasma mass spectrometry on an Agilent 7900 spectrometer. Their content in an acid-soluble form in oil samples under study ranged within 172 – 2173 ng/kg. Such a wide range of values is attributed to the difference in the geology and age of deposit formation. The highest content of acid-soluble forms of REE (2173 ng/kg) was observed in the oil sample from the Novo-Elkhovsky field, whereas the lowest value (172 ng/kg) was measured in the oil sample of the Pioneer field. It is shown that the content of acid-soluble forms of REE depends on tectonic zoning, productive horizons and layers, as well as on the physical and chemical properties of oils. The distribution of acid-soluble forms of light and heavy REE was evaluated. Most of the REE (75 – 99%) determined in the analyzed oil samples are light REE. It is noted that systematization of the data on the properties of oils, geological and geochemical characteristics of the deposits will provide reliable forecasting of the various forms of REE present in oils.

Checklist and Distribution of Calanoida (Crustacea: Copepoda) in Kazakhstan (Central Asia)

This work aims to analyze the zoogeographic distribution of Calanoida in Kazakhstan. Kazakhstan belongs to the Palaearctic region, and its territory is ascribed to the European–Siberian and Nagorno–Asian biogeographical subregions. The European–Siberian subregion includes the Volga–Ural, Irtysh, and Turkestan–Aral provinces. The Balkhash province belongs to the Nagorno–Asian subregion. Studies of the Calanoida fauna were carried out between 1997 and 2019. For this purpose, 7250 zooplankton samples were taken in 130 different water bodies. Findings of 26 species of Calanoida have been documented. The richest in species composition (20) is the Calanoida fauna of the Irtysh province. Ten Calanoida species have been recorded in the Volga–Ural province, 8 in the Turkestan–Aral province, 7 in the Balkhash province, and 5 in the Ponto–Caspian region. The distribution of the species richness of the order is determined by a complex of climatic factors, including the density of the hydrographic network, a variety of hydrochemical conditions, and accidental acclimatization of species. Far Eastern species (Sinodiaptomus sarsi, Neutrodiaptomus incongruens, Neodiaptomus schmackeri) entered the inland water bodies of Kazakhstan, most likely through the introduction of non-native fish species. The Black Sea species Acartia tonsa and Calanipeda aquaedulcis were introduced into the Caspian Sea with ballast waters. Three autochthonous species (Limnocalanus macrurus, Eurytemora grimmi, Eurytemora minor), formerly inhabiting the Caspian Sea, can now be considered extinct. Acanthodiaptomus denticornis, Arctodiaptomus (R.) salinus, Phyllodiaptomus blanci, and Eudiaptomus graciloides are widespread in the region. Endemic species (Gigantodiaptomus irtyshensis, Arctodiaptomus naurzumensis) and species are new for Kazakhstan (Diaptomus (Chaetodiaptomus) mirus, Eudiaptomus transylvanicus, Arctodiaptomus dentifer, A. (Rh.) ulomskyi were found in small waterbodies; they are known only from single occurrence sites as well as Eurytemora caspica. The last one was described from the northern part of the Caspian Sea, in the coastal zone. Further research into small water bodies that are poorly studied may expand our knowledge of the diversity of Calanoida in Kazakhstan. Calanoida fauna of Kazakhstan was closest to the fauna of countries with a continental climate and most strongly differed from countries with subtropical and Mediterranean types of climates.

Theoretical features of improving the oil recovery efficiency from carbonate reservoirs in the Volga-Ural province

Currently, the share of hard-to-recover oil reserves confined to carbonate reservoirs is more than 20% of the Volga-Urals hydrocarbon reserves. The use of traditional acid stimulation in conditions of a complex structure of carbonate reservoirs and low reservoir pressure is ineffective. In order to increase the efficiency of hydrochloric acid treatment, theoretical and experimental studies have been carried out aimed at increasing the efficiency of the work being carried out to stimulate the inflow to production wells that operate carbonate reservoirs. Filtration of the acid solution into low-permeability intervals of the carbonate reservoir involves the use of reverse counter-current capillary impregnation mechanisms. Analytical research methods made it possible to determine that the activation of the impregnation processes is carried out under conditions of nonstationarity of the pressure parameters of the reservoir system. Numerical modeling of the exposure process allowed to optimize the exposure parameters.

Factors of gas accumulations formation in oil-bearing sediments and in casing annulus of wells

Gas component study is one of the important tasks of petroleum geology. Gas component can exist in various forms in sedimentary rocks. Of great interest is nitrogen, the gaseous accumulations of which are formed in oil-bearing strata, causing complications during the oilfield development. The problem of abnormal nitrogen accumulations had great relevance in the fields of the Volga-Ural petroleum province, which is one of the long-term developed with a large stock of wells for various purposes. This article discusses possible sources of gaseous nitrogen and the reasons for its accumulations in oil-bearing reservoirs. The main purpose of the article is to clarify the reasons for the gaseous nitrogen and its deposits formation. The main patterns of the areal distribution of nitrogen gas accumulations in oil-bearing strata are revealed on the basis of field, hydrogeological, geological and geophysical researches data analysis. It has been established that during the gas caps formation, the source of gaseous nitrogen is its dissolved compounds in groundwater and oil, biochemical decomposition of which leads to the dissolved molecular nitrogen accumulation in a liquid medium. The release of free gaseous nitrogen and the formation of its accumulations is associated with the decompression of formation waters for natural (geological) or man-made reasons (hydrocarbons extraction). Disturbance of the natural hydrodynamic regime in oil-bearing formations leads to the release of gaseous nitrogen and the formation of its accumulations under favorable conditions (the presence of reservoirs, structures and impermeable rocks in the top of the formation).

SPECIFICS OF WELL KILLING TECHNOLOGY DURING WELL SERVICE OPERATION IN COMPLICATED CONDITIONS

The process of the well killing operations in the oil and gas condensate field in Volga-Ural province is complicated due to several conditions like fractured carbonate reservoir, abnormally low reservoir pressure, high gas-oil ratio, high hydrogen sulfide content, acid fracturing, and hydrochloric acid treatments requirement. During the well killing process, significant gas breakthroughs and fluid loss are observed in this field, which requires significant usage of blocking compositions (up to 50-100 m3 per single well) and increases the well service costs. The aim of this work was to increase the well killing efficiency during well service by studying the mechanisms that take place near the wellbore zone during this process. The application of statistical and multifactor analysis of well-killing processes were conducted from 2018 to 2019, which allowed highlighting the main reasons for the low success of these works. The calculation results showed that the stress state near the well significantly differs from the regional stress field and varies depending on the generated pressure in the well, which in turn affects the activity of fractures near the wellbore. The revealed mechanisms that take place near the wellbore zone coupled with the laboratory and pilot tests of the blocking compositions can be used to improve the well service operations at the oil and gas condensate field in the Volga-Ural province. In this work, it was concluded that it is important to use the geomechanical approach to increase the well killing efficiency in combination with a complex of laboratory rheological and filtration tests of blocking compositions.

Технология построения плотностной 3D-модели земной коры в ГИС INTEGRO

The work is devoted to the construction of a three-dimensional density model of the territory, which would not contradict the information obtained by other methods (drilling, seismic, etc.). A generalized scheme for constructing such a model is given, its stages and ways of matching with the results of other methods are described. The technology described in the work is based on the tools included in the GIS INTEGRO software package (FSBI "VNIGNI"). The article is illustrated with examples of the technology application in the construction of density models for various parts of the Volga-Ural oil and gas province. Key words: density modeling, 3D density model, inverse problem of gravity exploration, GIS INTEGRO.

About the structure of the Kama-Kinel trough system

Kama-Kinel Trough System (KKTS) — the structure formed in the Frasnian of the Late Devonian in the vast territory of the Volga-Ural province, is distinguished by the Upper Devonian — Lower Carboniferous deposits. The new interpretation of forming conditions of carbonate deposits in the KKTS has been given. The troughs of the KKST were formed in the Late Devonian as basin with gently sloping shelf zones. The deposits of the middle shelf (ramp), gently sinking into the side of the pool, where the layered accumulated precipitation are presented by bioclastic and intraclastic (lumpy) limestones and carbonate breccia, formed under the influence of storms. Three structural-facial zones, central, border and arched, allocated in the structure of deflections of the KKTS, reflect the structure of troughs formed as a result of tectonic restructuring at the beginning of the Visean and reactivated at the neotectonic stage. The uplift of the side zone considered as the reef buildups seem to be horst-shaped structures in fault zones. These features allow us to consider the structure of the KKTS as formed as a result of paleotectonic processes with the appropriate distribution of shallow and deep-water facies, subsequently changed as a result of reactivation of the basement faults.

Petroleum systems formation conditions in the deeply sediments in the south-east part of the Volga-Ural oil and gas province

Petroleum systems formation conditions in the deeply sediments in the south-east part of the Volga-Ural oil and gas province

Features of the composition and properties of crude oil from the Bavly oil field of the Volga-Ural oil and gas province

The article presents the results of a comparative analysis of the composition and physicochemical properties of crude oils produced from different horizons of the Carboniferous and Devonian deposits of the Bavly oil field (Tatarstan, Russia), including the Zavolzhsky and the Dankovo-Lebedyan horizons attributed to the domanic deposit. It is shown that oils from the domanic deposit are similar to Carboniferous oils by composition and properties but have unique features. A cluster analysis of the obtained results was carried out.

Assessment of the Need to Stimulate the Development of Hard-to-Recover Reserves in Carbonate Reservoirs

The subject of research is the process of oil recovery from the Kashira and Podolsky formations of the Volga-Ural Basin. The sites have some specific features including low degree of recovery, difficulties in applying secondary and tertiary methods to increase oil recovery factor and high production costs. Significant resources of these hard-to-recover oil reserves can be considered as a large pool for hydrocarbon extraction. It is important to assess the need to stimulate the development of these fields. The key issue to address herein is the estimation of recoverable oil reserves and the timing of development in primary production. Summing up the experience concerned with the development of separate oil deposits being in operation for a long time, a rapid assessment method for these indicators at the geologic exploration stage is proposed. Further technical and economic calculations make it possible to assess the necessity to stimulate the development of sites similar to those studied against their geological properties. It is proposed to solve these problems in context based on different groups of homogeneous sites not only in the Volga-Ural province but in neighboring oil and gas regions as well.

New methods of assessment, structure, and development of oil and gas resources of mature petroleum provinces (Volga-Ural province)

This study describes a new method for quantification of hypothetical oil and gas resources, which is considered to be an alternative to conventional estimates by analogy to geologically similar plays and is most appropriate for maturely explored provinces. This method is based on the size-frequency distribution of oil accumulations in sedimentary basins and has never been applied to petroleum exploration. The new approach makes it possible to assess the oil resources concentrated in small and smallest oil fields, which may become the main targets for petroleum exploration. This study reviews the discovery and exploration history of the Volga-Ural province and provides estimates of initial and hypothetical oil resources and the size distribution of undiscovered field and the number of their pools. It was shown that given the volume of exploratory drilling of 500-550 thousand m per year, it is expected that more than three billion tons of oil would be produced from small and smallest fields of this province by the mid-21st century, with a stable annual production of 40-50 million tons. It was shown that the development of small and smallest oil fields is performed by small and medium-sized oil companies, which can be delivered through a dedicated government program.

ПРОГНОЗ ФАЗОВОГО СОСТОЯНИЯ ЗАЛЕЖЕЙ УГЛЕВОДОРОДОВ НА ЮГО-ВОСТОКЕ ВОЛГО-УРАЛЬСКОЙ ПРОВИНЦИИ

ПРОГНОЗ ФАЗОВОГО СОСТОЯНИЯ ЗАЛЕЖЕЙ УГЛЕВОДОРОДОВ НА ЮГО-ВОСТОКЕ ВОЛГО-УРАЛЬСКОЙ ПРОВИНЦИИ

On the estimation of shale-oil resources and reserves

At present, the proven oil reserves from traditional Russian reservoirs are decreasing, leading to a steady fall in oil production. One of the possible ways to maintain the oil production at the present level is to produce tight oil, which is regarded as the category of oil from the Bazhenov Formation in the Kanty-Mansiysk region of Western Siberia, Domanik deposits in the Volga–Ural province, and Maikop deposits in the Fore-Caucasus.

Features of the Structure of Zones of Water-Oil Contacts in Carbonate Rocks of the Bashkirian Stage (using Akanskoye Oilfield in the Volga-Ural Petroleum and Gas Province as an Example)

Features of the Structure of Zones of Water-Oil Contacts in Carbonate Rocks of the Bashkirian Stage (using Akanskoye Oilfield in the Volga-Ural Petroleum and Gas Province as an Example)

Frasnian conodonts from the eastern Russian Platform

The Frasnian conodonts of the eastern Russian Platform from the Timan in the north to the Orenburg Region in the south are characterized in detail both paleontologically and stratigraphically. This paper is a continuation of a previously published monograph (Ovnatanova and Kononova, 2001) on the Frasnian conodonts of the shallow-water strata of the central Russian Platform, where polygnathids prevail. The conodont assemblages from the shallow-water and basinal sections of the Volga-Ural province and Southern Timan are analyzed. Problems and difficulties associated with the correlation of the shallow-water and deep-water Frasnian sections of the eastern Russian Platform and their correlation with the existing zonal conodont scales are discussed. The correlation between the deep-water Mendym deposits and the shallow-water Rechitza and Voronezh strata of the Volga-Ural province with the Vetlasyan and Sirachoi deposits of the Southern Timan is substantiated. The stratotype of the Semiluki Regional Stage of the Central Devonian Field contains equivalents of the lowermost beds of the Domanik Formation (unit 1), based entirely on polygnathids. Phylogenetic reconstructions for Palmatolepis and Polygnathus are suggested based on the ontogenetic series for some species of these two genera and the presence of transitional forms between some of the species. Based on these phylogenetic reconstructions, conodont zonal scales for the shallow-water and deep-water sections of the Frasnian Stage of the Russian Platform are proposed and their correlation with the existing conodont zonal scales is also adduced. Some aspects of biofacies control are considered based on the distribution of conodonts in the sections studied. In Systematic Paleontology, 91 conodont species of the genera Ancyrodella, Mesotaxis, Palmatolepis, and Polygnathus are described, including the new species Palmatolepis menneri, P. kaledai, P. acutangularis, and Polygnathus reitlingerae.