Siberian Oil Fields Research Articles

Influence assessment of shut-in duration and well startup sequence in different geological and field conditions

During 2019-2021, about half of well stock at West Siberian oil fields were shut down for a long period (up to one and a half year) due to oil production restrictions under the agreement between Russia and OPEC (Organization of the Petroleum Exporting Countries). There have never been such large-scale and prolonged shutdowns before. After starting from a long-term shutdown, the flow rate of some wells increased, while others decreased.The main aim of research is to assess the geological and technological factors affecting the results of starting wells after a long shutdown. Statistical methods were used, including multivariate regression analysis, assessing the influence of parameters on each other using trend lines on cross-plots, as well as constructing and comparing maps of geological and technological parameters.As a result, the influence of the duration of downtime, the simultaneity of shutdown of production and injection wells and compensation of production by injection was determined. That will help to reduce losses in case of repeated production restrictions by selecting optimal candidates for shutdown.

Updating the processes of long-term monitoring of production wells

The development of West Siberian oil and gas fields in conditions of total horizontal completion of wells showed that technologically our industry was not sufficiently ready for this challenge. To quickly build high-tech horizontal wells, to carry out multistage hydraulic fracturing in them and at the same time effectively manage the operation of high-tech horizontal wells, to ensure the required degree of reserves development, unfortunately, is not the same thing...Despite the fact that the actual coverage of well-testing, production logging and alternative long-term distributed monitoring based on stationary information and measurement systems in Russia in recent years has been extremely insignificant, a cumulative analysis of the data obtained in the industry on the leading vertically integrated oil companies speaks about the following negative trends identified by diagnostic methods: the existing domestic technologies do not allow to regulate and manage the inflow and intake profiles in horizontal wells, horizontal wells with multistage hydraulic fracturing, multibarrel wells, thereby initially ensuring uniform production of recoverable oil and gas reserves in the drainage zones of wells with horizontal completion; the undesirable breakthroughs into the borehole of a horizontal well of water and gas detected by means of borehole diagnostics were eventually not isolated by field services, as a result of which the wells were decommissioned prematurely, without ensuring the achievement of the project accumulated indicators of hydrocarbon production; according to measurements in the horizontal wells, incomplete confirmability of multistage hydraulic fracturing designs was found (both in estimates of crack lengths and in terms of determining the places and forms of their initiation in holes); finally, the profiles of the inflow and the composition of the inflow studied in dynamics, as a rule, changed quite quickly in time from the moment the wells were launched for the selection of products, which usually led to unpredictable production losses (flow deterioration was usually recorded from the toe and the central parts of the boreholes of horizontal wells); the most typical reason for the decrease in productivity in horizontal wells and horizontal wells with multistage hydraulic fracturing should be recognized as the clogging of boreholes with sand and proppant, as well as the lack of the ability of producers to promptly clean the boreholes without creating repression on the formation; all these problems are certainly aggravated for objects of the category of hard-to-recover initial-recoverable reserves of hydrocarbon raw materials. The fixation and justification of the above conclusions were largely obtained due to the gradual transition of oil and gas producing and service companies from traditional one-time complex measurements by production logging and well testing to permanent long-term stationary monitoring of well testing and production logging parameters in production wells using various types of point-distributed and distributed modular means of stationary information and measurement systems. This progressive high-tech direction of borehole research can potentially be significantly developed and spread in the industry in the near future (which will objectively contribute to the achievement of higher oil and gas recovery coefficients), provided that the state bodies supervising the development of hydrocarbon raw materials (Rosnedra, Ministry of Energy of the Russian Federation) will involve measures to motivate a deeper and more detailed study of the state of development of residual recoverable reserves at the developed fields.

Deep-Learning-Based Noniterative 2D-Inversion of Unfocused Lateral Logs

Abstract —The work deals with the development of methodological and algorithmic tools for the quantitative interpretation of oil well resistivity logs. We review the results of applying the neural-network-based approach to the inversion of resistivity logs measured at thinly bedded high-contrast environments. The capabilities of the proposed approach are demonstrated by the example of the algorithm for noninterative express inversion of unfocused lateral logs (BKZ). BKZ is the unfocused array logging method widely used in the Commonwealth of Independent States for oil well studies. BKZ logs are known for their complexity: The signals of unfocused gradient probes are highly affected by the medium properties below and above the measuring point. The developed algorithm is based on the inversion of full logs into the parameters of a 2D axisymmetric model of the medium, which allows naturally taking into account the influence of surrounding rocks and borehole conditions. Transition from the “layered” parametrization conventional for BKZ logs interpretation to a quasi-continuous change of properties along the well axis allows extracting meaningful information at every measurement point and constructing high-resolution geoelectric models of the sediments. The noniterative nature of the algorithm provides a high computing efficiency. This opens up the possibility of using the 2D inversion advantages to increase the reliability of the initial express interpretation results. Testing the algorithm on the practical data from West Siberian oilfields has revealed the field of its maximum efficiency, namely, study of impermeable and low-permeability sediments, such as the complex shaly caprocks and bituminous deposits of the Bazhenov Formation. With high-quality input data, the approach is also efficient for studying permeable terrigenous sediments.

West Siberian Oil and Gas Field – Metal Content of Oil and Processed Products

The paper aims to figure out the West Siberian oil and gas field- metal content of oil and processed products. By using the descriptive method for primary model, synthesis methods and process analysis and analysis of difficulties and discussion, The study of this problem point that, to assess the environmental impact of hydrocarbons on the biosphere, an accurate knowledge of the physical properties and chemical composition of oil and gas. Numerous tragic examples of accidents, such as those associated with a leak of hydrogen sulfide gases. Hydrogen sulfide, due to its higher density relative to air settles in the lowlands of the relief, accumulating in calm weather in concentrations up to lethal. This leads to the death of animals and the death of people. The latter could be avoided by going to elevated windward areas, i.e., knowing the physical properties of this toxic gas.

Improving the Efficiency of Managing the Development of the West Siberian Oil and Gas Province Fields on the Basis of Differentiation and Grouping

Abstract —Using image recognition methods (principal component method (PCM) and discriminant analysis) made it possible to group and identify more than 500 research objects developed in five oil and gas areas of the West Siberian oil and gas province (WSOGP), which are confined to 13 large tectonic structures and 10 productive horizons. The grouping was made according to 19 parameters characterizing the mode of oil and gas occurrence and the geologic–physical and physicochemical properties of the reservoirs and hosted fluids exerting a prevailing influence on the recovery of oil reserves and used on projecting the development of research objects. The performed study has identified 19 relatively homogeneous groups of objects, each having a specific set of geologic–physical properties. It is shown that the parameters reflecting the geologic–physical and physicochemical properties of the reservoirs and fluids within the identified groups of objects exert different effects on the recovery of oil reserves. This requires differentiation and grouping of the objects during the solution of various development problems. It has been established that the specific features of groups of objects are determined primarily by areal, tectonic, and stratigraphic factors and that grouping must be performed separately in each stratigraphic system. Algorithms are proposed for grouping the developed oil and gas fields and for searching for groups of analogous objects in fields out of exploration that are most similar to the developed ones. The performed grouping and the results obtained provide the necessary information about the research objects and increase its reliability, thus making it possible to improve the efficiency of managing the oil company assets, i.e., the WSOGP oil fields.

ONCE MORE ABOUT THE PALEOZOIC OIL IN WEST SIBERIA

In this article, the prospects of Paleozoic oil in the regions of West Siberia are considered. After a brief historical essay on the discovery of Siberian oilfields, the author suggests a new paradigm in petroleum geology and gives his recommendations on the further development of petroleum industry.

On the nature of Paleozoic oil deposits and their exploratory "reflection" in the geophysical section of the Jurassic layers (southeast of Western Siberia)

Commercial significance of the majority of Western Siberian oil fields is concerned with the Senomanian, Neocomian and, above all, Upper Jurassic horizons. For now, oil fields are at the late development stage and resource potential of the Jurassic horizon is strongly expired. Commercial potential of the pre-Jurassic (Paleozoic) rocks has been brought out throughout all territory of oil and gas province. Extensive work on estimation of the pre-Jurassic rocks oil and gas potential is performed in southeast, in the territory of Tomsk Region, within which 13 hydrocarbon deposits have been discovered in the Paleozoic. Original hypothesis of anomalousness of geophysical and petrophysical characteristics of the Jurassic layers — uniqueness of «indication» the Paleozoic deposits in geophysical parameters of overlaying Mezozoic-Cenozoic section was stated as a foundation of new prospecting criterion for the Paleozoic deposits. The Paleozoic formations are accepted as a complex with its own oil generating potential, which results in upward migration of hydrocarbon fluids. Additionally, downward direction of vertical interstratal hydrocarbon migration from the Jurassic source rocks into the pre-Jurassic complex is brought out. It was accepted as a conception that as in case of upward, so in case of downward fluid migration, processes of superposed epigenesis perform and lead to secondary epigenetic transformations of rocks of transit Jurassic layers, which result in their anomalous geophysical and petrophysical characteristics. This paper analyzes and compares geophysical and petrophysical characteristics of the Jurassic layers of different field types in Tomsk Region: without oil and gas potential in pre-Jurassic section, with commercial inflows from the pre-Jurassic complex and unknown type. Results of exploration electrical resistivity and carbonatization in the Jurassic layers of 200 wells and also spontaneous potential variation, electrical resistivity and natural radioactivity in Bazhenov suite confirm anomalousness of geophysical and petrophysical parameters of Jurassic rocks in case of pre-Jurassic deposits. This paper determines 6 geophysical and petrophysical characteristics of the Jurassic layers as predictive indicators for oil and gas potential estimation in pre-Jurassic section. Efficiency analysis of using predictive indicators for bringing out fields with and without deposits in the pre-Jurassic complex was performed for different prospecting cases in the research territory with account taken of possible complexing of indicators, their rank and actual availability. This paper states preference of indicators complexing. Application of a new prospecting criterion will improve efficiency of searching in new prioritized stratigraphic horizon — the Paleozoic, which contains unconventional oil.

Means to Solve the Problems of the Development of Helium Resources in Eastern Siberia

The article reviews the problem of effective development of helium resources of East Siberian oil and gas fields in the medium and long potential. It is noted that porous deposits of a gas field of small reserves appear to be the cheapest and the most reliable choice for the organization of underground helium concentrate storage (UHCS). In the medium term, it is proposed to consider the Otradninskoye gas condensate field (GCF), which is located in close proximity of the gas pipeline “Power of Siberia”. In the long term, the need to survey for a promising structure for the organization of UHCS is indicated. The basic requirements for the prospective structure are indicated by location, lithological section and by features of its development. As an example for the organization of UHCS, the Nizhne-Dzherba structure of the Predpatom trough is considered

Об одном методе классификации нефтяного месторождения с использованием комплекса геолого-промысловых данных и машинного обучения

In machine learning, k-means unsupervised model is used for classification analysis. In this paper k-means model is applied for productivity prediction of giant Western Siberian oilfield. An essential condition for method’s application is availability of digital databases with representative results. Complex method allows combine different reservoir and production parameters: rates, porosity, saturation, frac parameters etc. The method can be particularly useful in complicated reservoirs, e.g. in dual porosity ones, where the relationship between formation parameters (permeability, porosity, saturation) and production rates is unclear and cannot be set by traditional development analysis, particularly in frac environment.

Combined Approach Improves Fault Description for Horizontal-Well Geosteering

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 191695-18RPTC, “Complex Approach to Fault Description While Geosteering for Maximization of Reservoir Contact in Horizontal Wells in West Siberia Oil Fields,” by Vladislav V. Krutko, Tatyana A. Yurkina, SPE, and Dmitriy Y. Kushnir, Baker Hughes, a GE Company, and Valery B. Karpov, RITEK, prepared for the 2018 SPE Russian Petroleum Technology Conference, Moscow, 15–17 October. The paper has not been peer reviewed. This paper presents an interdisciplinary approach to the description of tectonic dislocations made on the basis of interpretation of seismic data, petrophysical analysis of well-logging data in horizontal wells, and inversion of a multifrequency propagation tool. A consistent approach to fault identification and description is presented on the basis of seismic surveys and logging-while-drilling (LWD) data in horizontal wells in a western Siberian oil field. Seismic Methods of Tectonic-Fault Interpretation Estimation of seismic methods of fault detection was performed on materials acquired from one of the fields in the Frolov oil-and-gas district. The observed territory of the oil field is characterized by complex geological structure—namely low effective reservoir thickness, thin layering of sandstones and silts, low porosity, low-permeability reservoir zones, and tectonic block structure. When drilling in reservoirs of low thickness, knowing the precise position of the horizontal wellbore relative to the structure is critical. The basis of drilling planning is a structural map of the reservoir top. After field jobs were complete and the results of the wide-aperture 3D seismic survey of the considerable refinement of the top structure of the reservoir were obtained, the morphology of all earlier identified structural forms was completed. A faulted and blocked principal model of the reservoir was created that formed the basis for a well-pad positioning scheme, as well as for usage in horizontal-well drilling. Horizontal Well 2301G was planned in the northwest region of the field. For reservoir-model construction, a structural map prepared from seismic-survey interpretation was used. An outcrop of the structural map with Well 2301G in place is presented in Fig. 1. A rare well network in the drilling area led to high uncertainty regarding structure parameters and risk of penetrating a fault. As an offset, Well 75B3 was used (Fig. 1). In this offset well, the horizon AC3 represented a thin layering of silt, shaly sandstone, and tight rocks. The thickness of the AC3 horizon was 13.2 m. During the drilling of the transport section, the wellbore of Well 2301G penetrated the top of the AC3 horizon at 1912.12-m true vertical depth, which coincided with the structural surface prognosis made on the basis of seismic data. The blocked model of the AC33 horizon is complex; the vision of the structure of the target reservoir can change significantly while drilling and penetrating the reservoir. According to seismic data, the possibility exists of crossing three faults along the planned horizontal section of Well 2301G.

USE OF OIL AS LUBRICANT ADDITIVE IN DRILLING MUD FLUID (ON THE EXAMPLE OF THE YARAKTINSKY OIL-GAS CONDENSATE FIELD)

The influence of the fractional composition of oil on the characteristics of the salt-saturated polysaccharide drilling mud used in drilling wells in Eastern Siberia was studied. As a lubri-cant it is better to use oil with a normal density, a small gas factor, low-paraffin, low-sulfur and resinous. In this regard, the results of the study of oils from West Siberian and East Siberian oil fields are given: Samotlor oil-gas condensate, Verkhnechonsk oil-gas condensate, Yurubcheno-Tokhomskoye oil-gas condensate, and Kuyumbinsk oil-gas fields. There pre-sented the experience of oil influence on drilling mud parameters, and also lubricity depend-ence on its fractional composition. The above mentioned oils exhibit lubricating properties, however, Samotlor oil contain more light fractions than all other oils , that is typical for West Siberian oils. High quality lubricat-ing oils can be produced from it. The friction coefficient has the smallest values, and decreas-es with increasing its concentration. While testing, oil was introduced into the solution in a concentration range from 0.1 % to 5 %. It was revealed that the oil of the Verkhnechonsk oil-gas condensate field has a signifi-cant influence on the density and rheological parameters of the solution. The density value increases at a concentration of up to 1 %, then decreases, while the rheological parameters increase in proportion to the increase in oil concentration in the drilling fluid. The oil of the Yurubcheno-Tokhomskoye oil field, as the concentration increases, reduces the density and increases the rheological parameters. With the increase in concentration in the oils of the Kuyumbinsk and Samotlor oil fields, rheological parameters increase. None of the oil sam-ples has a noticeable effect on the values of the hydrogen index. The presented oil of the Samotlor field can be used as a lubricant additive in the fields of Eastern Siberia, but final conclusions can only be made after an industrial test at the Yaraktinsky oil-gas condensate field.

SOLUTIONS FOR THE SYSTEM RELIABILITY OF FIELD FACILITIES OF WEST SIBERIAN OIL FIELDS

The issue of reliability assurance while constructing the oil field facilities by the example of West Siberian oil fields is considered. In particular, attention is paid to the problems that arise during the stage of mechanized crude oil production in case of high water cut of well produce, in severe natural and climatic conditions areas. The whole field development technological chain from the stage of crude oil production to the stage of crude-oil gathering and transportation was analyzed. For every stage the major factors, decreasing the system reliability, were determined and the suggestions for the elimination of these factors or reducing their negative influence were made. A number of possible measures for improvement field facilities construction reliability and profitability are indicated.

Dynamics of water separation in destruction of water-in-oil emulsions

The dynamics of drop formation and settling processes in breaking water-in-oil emulsions of the West Siberian oil fields was experimentally studied. The investigation results of drop formation in the water-in-oil emulsions were presented. The residual water content in oil was determined after the settling process at the varied initial water content, temperature, and hydrodynamic conditions of emulsion formation.

Pyritization effect on well logging parameters in Jurassic reservoirs within S-E Western Siberian oil fields

Authigenic sulfide mineralization in hydrocarbon-saturated reservoirs distorts the electrical and density properties of rocks. The correlation between volumetric density, electro-conductive minerals and open porosity in 300 samples were determined. This fact made it possible to develop a nomograph in evaluating oil saturated reservoirs and could be applied in well geophysical survey data interpretation.

Technology Focus: Mature Fields and Well Revitalization

Technology Focus In last year’s Technology Focus concerning mature fields, I highlighted safety, well integrity, and digital technology as the three enablers for achieving sustainable returns. In light of the challenging environment our industry is facing, I would suggest that JPT readers become familiar with refracturing techniques, technology/methodology that improves efficiency, and opportunities that achieve positive financial impact and exceed environmental responsibility. First of all, the surge in unconventional completions over the last decade has created ample candidates for hydraulic refracturing. With the proper implementation of new and improved techniques, followed by diligent economic analysis, refracturing has been demonstrated to be a viable alternative to the more expensive endeavor of drilling and completing new wells. There are numerous informative and enlightening SPE publications on this topic. Speaking of technology and methodology that improves efficiency, these are the technologies that will be embraced and adopted quickly by the industry, especially in this challenging environment. One of the examples is a methodology that precisely and effectively locates the remaining oil in mature reservoirs. In addition to identifying potential opportunities, it also serves to derisk project investment and allows key decisions to be made in a timely manner. The other example is a stimulation technique that is designed to deliver pinpoint accuracy. These are technology enablers that, when combined, could significantly improve well performance through precisely addressing isolation, diversion, and placement, for example. The last point is about achieving investment returns and, at the same time, exceeding corporate environmental responsibility. It seems unlikely that we can have our cake and eat it, too. However, I have witnessed enough examples (mostly outside of our industry) to realize that this certainly can be achieved. The journey will not be easy. Some examples take more than 15 years of persistence and investment to become established. I sincerely encourage JPT readers to incorporate this aspect into their professional responsibility and continue to challenge themselves and their teams. In this editorial, I talked about refracturing, efficiency, and environmental responsibility. Therefore, I have selected several papers on these topics to share with you. We all know 2016 will be a challenging year for our industry; however, I am sure this is the driving force that we need to take our industry to the next level. JPT Recommended additional reading at OnePetro: www.onepetro.org. IPTC 17718 Successful Restimulation of Western Siberian Oil Fields With Channel Fracturing Technique by Alexey Yudin, Schlumberger, et al. SPE 173340 Refracturing in Eagle Ford and Bakken To Increase Reserves and Generate Incremental NPV—Field Study by YagnaDeepika Oruganti, Baker Hughes, et al. SPE 173601 Reduced Emissions and Increased Production Through Gas Compressors: Pilot Case in Colombia by J.C.M. Escobar-Remolina, Ecopetrol, et al.

Firmicutes is an Important Component of Microbial Communities in Water-Injected and Pristine Oil Reservoirs, Western Siberia, Russia

ABSTRACTThe dominant microbial components of fluids from wells in pristine and water-injected, high-temperature, Western Siberian oil fields, were analyzed by PCR-DGGE. Particular emphasis was placed on sulphate-reducing organisms, due to their ecological and industrial importance. Bacterial phylotypes obtained from the non-water-injected Stolbovoye oil field were more diverse than those from the Samotlor field, which is subject to secondary oil recovery by reinjection of recycled production water. The majority of phylotypes from both sites were related to Firmicutes. The low similarity to their closest relatives indicates unique bacterial communities in deep underground production waters and crude oil. Archaeal phylotypes detected only in the Samotlor samples were represented by Methanosarcinales and Methanobacteriales.

Description of fracture zones based on the structural inhomogeneity of the reflector deformation field

The role of fracture and faulting zones in the filtration inhomogeneity of productive formations in oil and gas fields has been considered. The absence of fracture or faulting zones from geological and, consequently, hydrodynamical models reduces the flooding efficiency and the oil recovery factor in general.The current situation results from the underdevelopment of methods for the mapping and classification of fracture zones based on seismic-prospecting data. For example, the use of the seismic-horizon gradient method makes it possible to describe only complete rock fracturing at tectonic-block boundaries.We propose to use the structural inhomogeneity of the deformation field of seismic horizons for a more complete description and classification of fracture zones by the faulting regime. This parameter is suitable not only for late but also for early stages of faulting and describes block-boundary deformations more accurately than gradients. The example of a West Siberian oil and gas field showed that the production wells from the J1 productive formation in the faulting zones with the calculated post-Cenomanian structural inhomogeneity of the deformation field have considerably higher discharges owing to fracture permeability.

Keeping the Pipeline Full

Large infusions of money and new technology will be needed to fill the oil gathering systems in the West Siberian oil fields. The owner of this field, Salym Petroleum Development, hopes to increase the output of its fields using chemically enhanced oil recovery and by producing oil from the Bazhenov formation. Russia Considers Its Unconventional Options To search online for the story of how Russia became one of the world’s top oil producers, try the keywords “West Siberia.” For the future, try “Bazhenov.” The Bazhenov is the source rock for the prolific West Siberian fields that still yield about two-thirds of Russia’s crude oil production nearly 50 years after the oldest of those fields went into production. The formation covers an enormous area—conservative estimates put it at more than 1 million km2, which is 1.5 times as large as the US state of Texas. The low-end estimate of the total reserves in the Bazhenov by a national agency that estimates Russian resources in the ground, Rosnedra, is 182 billion bbl, according to Platts, an oil industry trade publication. The high end is double that total. Now, some of the biggest oil companies in Russia, and the world, are trying to figure out how to convert that resource into reserves. Bazhenov wells have been drilled for decades, and have earned the formation a reputation for unpredictability. The drive to take what has been learned about unconventional oil production in the US and use it in West Siberia was a key theme at the recent SPE Russian Oil & Gas Exploration and Production Technical Conference and Exhibition in Moscow. Another theme was the growing list of techniques being employed to extract more oil out of conventional formations: from using advanced seismic analysis, to new drilling and completion methods to tap unproductive formations, to enhanced oil recovery (EOR) using chemicals. An example of all of the above is Salym Petroleum Development (SPD). The 50/50 joint venture between Shell and Gazpromneft, a Gazprom subsidiary, has been investigating the Bazhenov in its fields in West Siberia, where it has also been drilling hundreds of wells based on advanced seismic studies to reach unproduced zones. And it is testing chemical EOR. Based on lab work and a single-well field test, using alkaline surfactant polymer (ASP) treatments could significantly increase its ultimate production, Simon Durkin, chief executive officer of SPD, said in an interview during the Russian conference. Using chemicals to free more of the oil from the formation and improve the sweep of a waterflood could add more than 100 million bbl of incremental production over 30 years, according to company estimates.

High resilience in the Yamal-Nenets social–ecological system, West Siberian Arctic, Russia

Tundra ecosystems are vulnerable to hydrocarbon development, in part because small-scale, low-intensity disturbances can affect vegetation, permafrost soils, and wildlife out of proportion to their spatial extent. Scaling up to include human residents, tightly integrated arctic social-ecological systems (SESs) are believed similarly susceptible to industrial impacts and climate change. In contrast to northern Alaska and Canada, most terrestrial and aquatic components of West Siberian oil and gas fields are seasonally exploited by migratory herders, hunters, fishers, and domesticated reindeer (Rangifer tarandus L.). Despite anthropogenic fragmentation and transformation of a large proportion of the environment, recent socioeconomic upheaval, and pronounced climate warming, we find the Yamal-Nenets SES highly resilient according to a few key measures. We detail the remarkable extent to which the system has successfully reorganized in response to recent shocks and evaluate the limits of the system's capacity to respond. Our analytical approach combines quantitative methods with participant observation to understand the overall effects of rapid land use and climate change at the level of the entire Yamal system, detect thresholds crossed using surrogates, and identify potential traps. Institutional constraints and drivers were as important as the documented ecological changes. Particularly crucial to success is the unfettered movement of people and animals in space and time, which allows them to alternately avoid or exploit a wide range of natural and anthropogenic habitats. However, expansion of infrastructure, concomitant terrestrial and freshwater ecosystem degradation, climate change, and a massive influx of workers underway present a looming threat to future resilience.

Effect of oil temperature on paraffin waxing of oil field equipment

Analysis of paraffin-waxing of oil field equipment at West Siberian oil fields has shown that the number of wells troubled by wax deposits has been going up every year. Wax deposition causes fall in oil recovery and entails additional cost for deposit removing. Many researchers have studied the distinctive features of the process of wax deposit formation from model solutions [1‐3]. Analysis of the obtained data has revealed that they are highly inconsistent even for such simplified systems as artifi cial mixtures of wax and solvent. That is why, to prevent resin-wax deposits (RWD), it is essential to study their formation process in real oils. Until now, this process has been poorly studied because of wide diversity of properties and compositions of oils. In view of development of new oil fields characterized by heightened bed temperature and substantially increased wax content as well as of oil fields located in regions having permafrost soils, there is a pressing need for investigating the composition and properties of deposits formed in a wide range of temperature gradients. The reagents under development generally act selectively on the oil or a group of oils distinguished by a definite ratio of waxes, resins, and asphaltenes. It was therefore necessary to conduct further research into the composition and properties of the formed resin-wax deposits as a function of the difference in the temperatures of the oil and the metal rod being cooled ⌉t that reached 60°C. It covers the temperature variation range in which wax deposition on well equipment occurs. In the experiments, we used in-situ oils with diverse component compositions, which were collected from four clusters of wells located in various corrosion-active areas of the Samotlor field (Table 1). An aliquot of the oil was heated to 7 0°C and held at this temperature for 30 min. Next, the vessel containing the oil was placed in a water container and a cylindric steel rod filled with ice was dipped into the oil. The oil temperature was monitored by a thermocouple. The RWD formation process continued for 1.5‐2 h, after which the deposits formed were extracted and submitted to thorough analysis. The deposit composition was studied by using well-known procedures [4], which made possible identification of waxes, resins, and asphaltenes. The composition of the identified waxes was determined by gas-liquid chromatography, the surface activity of the resins separated from the deposits was determined from the acid number (GOST 11362‐76), and the carbon dioxide content in their pyrolysis products was determined by a procedure described in [1]. The properties of the RWD were determined by using conventional procedures described in [5, 6]. As evident from Fig. 1a‐c, the mass fraction of the deposits from the well clusters III and IV is 2.0‐6.2 mass %. The variation in the mass fraction of the deposits with temperature gradient has a maximum in the temperature region where the oil is saturated with wax. This maximum is assignable to crystallization of the wax at a temperature lower than the saturation temperature [7]. For the oils from the well clusters I and II (these oils are relatively high in viscosity), a 10‐15%