At the present stage of the hydrocarbon production process, most of the unique and largest fields in the world are at a late stage of development. Despite the active development and policy of a decarbonised economy, the demand for liquid and gaseous hydrocarbons remains high, while of inevitably growing the number of mature fields. The Volga-Ural oil and gas province today is an old oil and gas producing region, most of the fields have already entered the final stage of development. However, through the introduction and development of new technologies for oil extraction, monitoring of production and localization of reserves, the life of the fields can be extended. One of these technologies is geochemical monitoring of well production. Its goal is to optimize the development of mature fields on the basis of promptly obtained information about the state of the wells using geochemical studies of the formation fluid, allowing timely implementation of the necessary measures. Geochemical studies allow identifying the source of fluid entering the well, determining a violation in the wellbore structure, checking the tightness of downhole equipment for separate operation, and performing an area analysis of the area development efficiency. This type of research is relevant both in giant fields with a large stock of production wells, often characterized from a geological point of view by multilayer structure, with technological complexity, packing, wear of equipment and strings, in some cases the impossibility of running gauge for research, and in fields with low depletion. The possibilities of geochemistry for solving local operational problems in wells are shown. Several hydrogeological complexes have been studied, the change in the properties of the produced water during the development process is described. The concepts of the geochemical conditions in the hydrocarbon deposits that existed earlier are changing due to the development of these objects as a dynamic system, continuous injection of different types of water into the reservoir, the use of enhanced oil recovery methods and other technogenic impact associated with the development of reserves. The digital revolution and the modern development of the industry marked the beginning of the creation of the Digital Atlas of Groundwater, the development of specialized algorithms that allow processing large amounts of data.

The study field is located in the Nizhnevartovsk district of the Khanty-Mansi autonomous region. The deposit is located in the Nizhnevartovsk crest zone. The geological section of this deposit features a thick layer (2740-2870 meters) of Meso-Cenozoic era sedimentary rocks starting from the Jurassic period up to and including the Quaternary period, and rests unconformably on the surface of the deposits of the folded Paleozoic basement. The pay zones of study oil and gas fields features mainly sandstone-siltstone reservoirs. The study formation XX11-2 features interleaved rocks with a high clay content. In the west and south-west of the field, the oil-saturated thicknesses vary on average from 5-10 m, and in the north, the thickness increases to 10-20 m. This field has a long-lasting production history as a result of drilling vertical and horizontal wells but is currently at production decline stage. The existing reservoir pressure support system assumes that the water-cut trend at the wells will increase. In recent years, there has been advanced flooding in some areas, resulting in a drop in oil production, while the reasons for the advanced flooding are not always clear. This is often due to the progressing spontaneous fracturing in the injector wells ( Aslanyan, Akimov et al., 2020 ).

The paper presents the results of a study project of 60+ well block of the large (> 1,000 wells) mature (30 year old) oilfield in Western Siberia with objective to localise and characterize residual recoverable reserves and propose the optimal economic scenario for further depletion. Low permeability, heterogeneous reserve structure along the cross-section, numerous induced hydraulic fractures in producing wells and numerous spontaneous fractures in injecting wells with dynamic behavior, aggravated by numerous behind-the-casing crossflows in almost every well have resulted in a very complex conditions of remaining reserves. The conventional methods of production analysis and surveillance (well testing and production logging) do not provide a consistent picture of the current distribution and conditions of the remaining reserves and required a deeper and more complex analysis. Development Opportunities Management workflow was chosen for this particular holistic study, which includes a set of interconnected studies, field surveillance, geological and flow modelling and culminated in field development planning based on the digital asset twin. ( Ganiev, B., 2021 ) Digital asset twin was constructed based on results of this workflow with a full-range economical model, flow simulation over the thoroughly calibrated fine-grid 3D dynamic model and production complication model (dynamic behavior of the fractures and behind-casing channeling). The 3D model has been calibrated on results of the cross-well pressure-pulse surveillance, reservoir-oriented production logging and was validated by the results of the drilling of the transition wells. The digital asset twin was used to find the optimal investment scenario based on multivariate calculations with the help of digital assistants. Due to simplicity of the user interface and client-server design, the digital twin was made available for various corporate engineers and managers without any modelling skills to play around with their own ideas on possible production/investment scenarios which gave another level of validation of the ultimate field development plan. All activities carried out within the digital twin automatically generate a complete package of investment metrics (NPV, PI, IRR, MIRR, Cash Flow and many correlation graphs) to assess the economic efficiency of each package and select the most appropriate solution for further ultimate choice. The approved scenario was based around drilling 6 producing side-tracks in specific locations/trajectories, performing workovers on specific offset injectors and re-scheduling of the production/injection rates in all block wells. The results of the field development's activities implementation will be the subject of a future publication.

The main objective of the study is to compare the results of the cross-well tracers survey against the pulse code pressure interference testing ( PCT ) for the complicated geological structures. The study was based on the numerical simulations on the synthetic 3D models with popular geological complications, such as faults, vertical and horizontal reservoir anisotropy and pinch-outs. The study has set a special focus on quantitative analysis of the reservoir properties estimated by tracers and PCT as against the known values. This provides a text-book examples of advantages and disadvantages of both surveillance methods in different geological environment. Pulse code testing is specific implementation of pressure interference testing by creating a series of injection/production rate changes accordingly to a preset schedule to create a "pressure code" and monitoring the pressure response in the offset wells. The use of high-resolution quarts gauges is highly beneficial in case of large cross-well intervals scanning or poor reservoir quality in case of regular inter-well spacing. The tracer survey is based on injecting a liquid with chemical markers and subsequent capturing the markers at surface samples in the offset wells. The modern markers are relatively cheap and can be captured at very low concentrations thus making the cross-well scanning available even for high inter-well spacing. For synthetic models with vertical inhomogeneity the PCT provides a close estimate for compound dynamic reservoir properties (transmissibility and pressure diffusivity). For synthetic models with lateral inhomogeneity the PCT provides an accurate estimation for effective reservoir thickness and permeability. Tracers survey is not able to assess the reservoir thickness. The popular methods to assess reservoir permeability from tracers survey show a substantial deviation from the true reservoir permeability for synthetic models with vertical and lateral heterogeneity. This leads to conclusion that the most reliable application of racers survey is a qualitative assessment of cross-well connectivity and quantitative estimate of permeability in homogenous reservoirs. The first study of quantitative comparison of tracer survey against pressure pulse-code interference survey. Tracer survey and PCT efficiency was compared on 3D numerical models. Presence of synthetic models, describing geological complications, which may be seen very often on real reservoirs, provides a reliable basis for comparison.

The paper presents a practical case of production performance analysis at one of the mature waterflood oil fields located at the Volga-Ural oil basin with a large number of wells. It is a big challenge to analyse such a large production history and requires a systematic approach. The main production complication is quite common for mature waterflood projects and includes non-uniform sweep, complicated by thief injection and thief water production. The main challenge is to locate the misperforming wells and address their complications. With the particular asset, the conventional single production analysis techniques (oil production trend, watercut trend, reservoir and bottom-hole pressure trend, productivity trend, conventional pressure build-up surveys and production logging) in the vast majority of cases were not capable of qualifying the well performance and assessing of remaining reserves status. The performance analysis of such an asset should be enhanced with new diagnostic tools and modern methods of data integration. The current study has made a choice in favor of using a PRIME analysis which is multi-parametric analytical workflow based on a set of conventional and non-conventional diagnostic metrics. The most effective diagnostics in this study have happened to be those are based on 3D dynamic micro-models, which are auto-generated from the reservoir data logs. PRIME also provided useful insights on well performance, formation properties and the current conditions of drained reserves which helped to select the candidates for infill drilling, pressure maintenance, workovers, production target adjustments and additional surveillance. The paper illustrates the entire PRIME workflow, starting from the top-level field data analysis, all the way to generating a summary table containing well diagnostics, justifications and recommendations.

The objective of this article is to share an evaluation of the background, drilling outcomes and production and reservoir pressure impacts from two years of monitoring the first commingled up-dip SMART water injector drilled in the Piltun area of the Piltun-Astokhskoye offshore oil and gas field, located in Sakhalin, far east of Russia. The unique aspect of this water injector is that it was drilled into the up-dip gas caps of two separate reservoirs to provide pressure support to commingled oil producers, complementing the down-dip water injectors already in place. This article highlights some details of the well maturation decisions and expectations based on output of the dynamic modelling studies. Drilling outcomes and well performance is compared to expectations. Initial results of the surveillance programme and field data analysis based on a two-year monitoring period are discussed to show intermediate outcomes of up-dip water injection in the Piltun area. Finally, remaining questions and uncertainties are shared. Piltun-Astokhskoye is a complex multi-reservoir offshore oil and gas field with sizeable gas caps, significant heterogeneity both between and within reservoirs and a complex production history involving commingled oil producers and water injectors. Limited data is available to assess the impact of development decisions. Integrated analysis using multiple data sources and back-to-basics geology and reservoir engineering is required to understand how the reservoirs are responding to up-dip water injection, in order to predict future performance and make informed decisions to optimise the Piltun development over the long term. Surveillance data shows that up-dip water injection is effective in increasing reservoir pressure and oil recovery in one of the reservoirs, whilst having little impact on the other. Analysis shows that variable impact is due to the influence of gas cap size on up-dip water injection efficiency and the risk of trapped gas volumes due to water injection into the gas cap. The importance of integration between different sources of surveillance data and analytical tools to complete a comprehensive and reliable analysis is shown.

The paper describes the basic features of the East-Messoyahskoe oil field that are important for efficient reservoir development, the key of which are high oil viscosity (111 cP), high heterogenieity and permeability contrast, and the presence of aquifer with a different strength. The review of the experience in proactive breakthrough risks identification is presented. The actual breakthroughs during waterflooding of the PK-13 reservoir of the East-Messoyahskoe oil field are described and analyzed. The backgrounds and regularities increasing the risks of breakthroughs are identified. The analytical calculations have been made and key influencing factors have been defined. Based on the obtained results, the methodology of the proactive breakthrough identification was developed. The methodology has been tested in the real conditions of the East-Messoyahskoe oil field. The first results have been received, which confirm the operational efficiency of the developed methodological approach. All wells were rated according to their breakthrough risk, and measures for operative and proactive breakthroughs risk management has been proposed. All listed are combined into a system which permits minimization of breakthrough risks and manages them for the increase of unconsolidated heavy oil reservoirs development efficiency.

The paper describes a methodology for assessing the impact of wax deposition in reservoir oil during cold water injection into heterogeneous carbonate reservoir D3-III of the Kharyaga field. The main goal is to determine the optimal amount of hot water that must be injected before switching to cold water without affecting the field development. The paper presents the results of laboratory studies to determine the thermophysical properties of oil, samples of net reservoir and non-reservoir rock, as well as the results of laboratory studies to determine the conditions and nature of wax deposition in oil when the temperature and pressure conditions change. Calculations were carried out to describe the physical model of oil displacement by water of various temperatures. A series of synthetic sector model runs was performed, which includes the average properties of the selected reservoir and the results of laboratory studies in order to determine the effect of cold water injection on the development performance.

To reduce inefficient costs and environmental risks, oil companies strive to optimize the process of hydrocarbon production at all stages of field development, including geological and technical works at wells. In particular, it is important to predict fluid production with high accuracy. 3D hydrodynamic modeling is a generally accepted technique for solving this problem. It provides reliable results but requires many input data, computational resources, and time for calculations. Since the decision-making process has to be reactive, it is necessary to develop a simultaneously precise and prompt predictive instrument for quick forecasts of liquid production. The most promising tools for these purposes are proxy models based on solving the material balance equation. They adapt to the existing historical data even without PVT properties and reservoir data. Some of the most popular approaches are proxy models such as Capacitance Resistance Models (CRM). CR-type model is a material balance-based flow model, which provides preferable transmissibility trends, the presence of sealing or leaking faults with compressibility effects in consideration, and dissipation between injector-producer pairs. It is a data-driven model with adjustable time constants and interwell connectivity parameters. Before the model tuning, all parameters must be initialized with analytical or random approximations, and then they can be found by an appropriate optimization procedure. Historical-based Capacitance Models can be applied to poorly studied fields. Besides, they give an opportunity to rapidly optimize field development strategy by making calculations with different well exploitation parameters. They only require historical data of hydrocarbon production volumes, injection profiles, and bottom-hole pressure dynamics as input data. One of the main is that properties in the interwell space are estimated approximately and considered to be constant throughout the entire development history. However, this is a weak assumption in the case of including well interventions and stimulations. Thus, the main goal of this work is to adjust coefficients online to changes in well operation modes, introducing new wells or shut-in the existing ones. Since the governing equation includes the considered CRM improvement, users can perform optimization over different timespans, including "special" intervals. As a result, weighting connectivity parameters of the model can be depicted on a map of well interactions versus time.

In pursuit of efficient oil and gas field development, including hard-to-recover reserves, the key objective is to develop and provide the rationale for oil recovery improvement recommendations. This paper presents the results of the use of the workflow process for optimized field development at two field clusters of the Yuzhno-Vyintoiskoye field using geological and reservoir modelling and dynamic marker-based flow production surveillance in producing horizontal wells. The target reservoir of the Yuzhno-Vyntoiskoye deposit is represented by a series of wedge-shaped Neocomian sandstones. Sand bodies typically have a complex geological structure, lateral continuity and a complex distribution of reservoir rocks. Reservoir beds are characterised by low thickness and permeability. The pay zone of the section is a highly heterogeneous formation, which is manifested through vertical variability of the lithological type of reservoir rocks, lithological substitutions, and the high clay content of reservoirs. The target reservoir of the Yuzhno-Vyintoiskoye field is marked by an extensive water-oil zone with highly variable water saturation. According to paleogeographic data, the reservoir was formed in shallow marine settings. Sand deposits are represented by regressive cyclites that are typical for the progressing coastal shallow water ( Dulkarnaev et al., 2020 ). Currently, the reservoir is in production increase cycle. That is why an integrated approach is used in this work to provide a further rationale and creation of the starting points of the reservoir pressure maintenance system impact at new drilling fields to improve oil recovery and secure sustainable oil production and the reserve development rate under high uncertainty.

In this paper the simplified way is proposed for predicting the dynamics of liquid production and estimating the parameters of the oil reservoir using diagnostic curves, which are a generalization of analytical approaches, partially compared with the results of calculations on 3D simulation models and with actual well production data.

In the context of a comprehensive search for ways to optimize and reduce operating costs for hydraulic fracturing operations, one of the areas to consider is the use of alternative water sources for making-up hydraulic fracturing fluids such as Cenomanian, mixed or produced water. This solution allows to optimize the speed and quality of work without wasting time and financial resources due to no need for heating and remote transportation. The main goal of the study was to create a stable guar-based hydraulic fracturing fluid system with a borate crosslinker, which allows high-quality treatment using high-salinity water. Much attention is paid to the composition of real saline sources, i.e. produced, mixed and Cenomanian water, which were sampled from the Gazpromneft-Khantos fields. Based on the data ranking by composition, the main groups of mineral components, as well as the cut-off criteria that determine the behavior of a hydraulic fracturing fluid in linear and cross-linked forms, were identified. The main stage of working on the fluid system quality included two areas: screening stabilizing components that meet the criteria for performing hydraulic fracturing operations, and assessing the fluid clogging properties based on flow tests. To study and select the composition of a hydraulic fracturing fluid, both standard and extended rheological tests were performed, which included core tests on real samples from target reservoirs and tests of residual conductivity and permeability of a proppant pack. The sand-transport properties of the fluid were measured both in static and dynamic conditions. The study resulted in the development of a fluid system complex including stabilizing additives and criteria for their applicability at real field conditions, taking into account the features of the existing equipment of hydraulic fracturing fleets. Experiments have shown that standard guar fluids based on water from alternative sources, when using a complex of stabilizing components, successfully replace the basic set of additives for fresh water, and are quite competitive not only in rheological properties and the ability to transport proppants, but also in restoring the permeability of a proppant pack and core samples. Each stabilizing component of such fluid makes its own unique contribution to achieving the required parameters of the fluid without losing its quality. An important achievement is the development of methods and criteria for the applicability of stabilizing components that make it possible to work with any source, whether it is produced, mixed, or Cenomanian water. The solution allows in a short time to adjust the fluid system depending on the actual mineral composition in a stationary field laboratory without the involvement of specialized equipment and expensive research.

The paper presents the results of a pilot project implementing WAG injection at the oilfield with carbonate reservoir, characterized by low efficiency of traditional waterflooding. The objective of the pilot project was to evaluate the efficiency of this enhanced oil recovery method for conditions of the specific oil field. For the initial introduction of WAG, an area of the reservoir with minimal potential risks has been identified. During the test injections of water and gas, production parameters were monitored, including the oil production rates of the reacting wells and the water and gas injection rates of injection wells, the change in the density and composition of the produced fluids. With first positive results, the pilot area of the reservoir was expanded. In accordance with the responses of the producing wells to the injection of displacing agents, the injection rates were adjusted, and the production intensified, with the aim of maximizing the effect of WAG. The results obtained in practice were reproduced in the simulation model sector in order to obtain a project curve characterizing an increase in oil recovery due to water-alternating gas injection. Practical results obtained during pilot testing of the technology show that the injection of gas and water alternately can reduce the water cut of the reacting wells and increase overall oil production, providing more efficient displacement compared to traditional waterflooding. The use of WAG after the waterflooding provides an increase in oil recovery and a decrease in residual oil saturation. The water cut of the produced liquid decreased from 98% to 80%, an increase in oil production rate of 100 tons/day was obtained. The increase in the oil recovery factor is estimated at approximately 7.5% at gas injection of 1.5 hydrocarbon pore volumes. Based on the received results, the displacement characteristic was constructed. Methods for monitoring the effectiveness of WAG have been determined, and studies are planned to be carried out when designing a full-scale WAG project at the field. This project is the first pilot project in Russia implementing WAG injection in a field with a carbonate reservoir. During the pilot project, the technical feasibility of implementing this EOR method was confirmed, as well as its efficiency in terms of increasing the oil recovery factor for the conditions of the carbonate reservoir of Eastern Siberia, characterized by high water cut and low values of oil displacement coefficients during waterflooding.

The paper considers the use of a surfactant-polymer composition for the mobilization of light paraffinic oil from the D3-III carbonate reservoir at a reservoir temperature of 62°C, as well as the results of its tests in field conditions. Earlier, the composition showed its effectiveness on model carbonate cores with salinity from current (50-80 g/l) to reservoir (up to 170 g/l), in the presence of surfactants, type III microemulsions according to Winsor with oil were obtained. Based on the results of the filtration experiments performed on our own core from the productive formation D3-III, an increase in the displacement efficiency of surfactant-polymer compositions compared to water was obtained 11–14% (with a total surfactant concentration of 1%), irreversible surfactant losses in water-saturated rock–up to 0, 38 mg/g. Displacement efficiency after water and surfactant-polymer composition flooding was also estimated in the field conditions using SWCTT; its results were interpreted by various methods (analytical, in a hydrodynamic simulator), and also compared with laboratory results. Within a single-well tracer test, an assessment of the residual saturation after water filtration and injection of a surfactant-polymer composition was carried out under the following conditions: the target research radius is 3.5 m; porosity 10%, effective reservoir thickness 38 m. Based on the results of SWCTT, an increase in the displacement efficiency of 16.7% was obtained in comparison with water displacement (total surfactant concentration 1%) using an analytical method of interpretation. The adaptation of the SWCTT results on the hydrodynamic model was carried out, the most influencing parameters on the quality of adaptation were determined. The selection and justification of a pilot area for a multi-well pilot project was carried out, a sector hydrodynamic model of the site was built, and calculations were made to assess additional oil production.

The paper describes the process of evaluation of low salinity water composition to improve the development of hydrophobic carbonate formations of Central-Khoreiver Uplift (CKU) fields with relatively high oil viscosity (5-15 mPa·s) and average formation temperature 70°C. The sources of low salinity water were determined, prospective composition for water injection were analyzed. The efficiency of oil displacement by formation water and low salinity water are observed during the spontaneous imbibition experiments and coreflood tests to compare the efficiency of formation and low salinity water. The expected incremental displacement efficiency for the target carbonate formations can vary widely, from 1 to 10%. Linear models of the completed coreflood tests and a sector hydrodynamic model of the prospective trial injection are built, considering the basic chemical processes while mixing different types of water. We also review the prospects of joint application of low salinity water injection and chemical EOR methods.

In this study, a visualized physical model of artificial oil film was firstly designed to investigate the oil film displacement mechanisms. Numerous comparative experiments were conducted to explore the detachment mechanisms of oil film and oil recovery performances in different fluid mediums with flow rate. In addition, the of influencing factors of oil film were comprehensively evaluated, which mainly includes: flow rate, surfactant behaviors, and crude oil viscosity. The results show that, (1) regardless of the viscosity of crude oil, flow rate presents a limited contribution to the detachment of oil film and the maximum of ultimate oil film displacement efficiency is only approximately 10%; (2) surfactant flooding has a synergistic effect on the oil film displacement on two aspects of interfacial tension (ITF) reduction and emulsifying capacity. Giving the most outstanding performance for two oil samples in all runs, IFT reduction of ultra-low value is not the only decisive factor affecting oil film displacement efficiency, but the emulsifying capability plays the key role to the detachment of oil film due to effect of emulsifying and dispersing on oil film; (3) the increasing flow rate of surfactant flooding is able to enhance the detachment of oil film but has an objective effect on the final oil film displacement efficiency; (4) flow rate have the much influence on the detachment of oil film, but the most easily controlled factor is the surfactant property. The finding provides basis for oil film detachment and surfactant selection EOR application.

A Capacitance Resistance Model (CRM) is an analytical model that only requires production and injection rates to predict reservoir performance. The CRM input is the injection rates and the output is the production rate. The input and output are related by the CRM parameters. The first parameter is the time delay (also called time constant) and is a function of pore volume, total compressibility, and productivity indices. The second parameter is the connectivity (also called gain, or weight), which quantifies the connectivity between producers and injectors (i.e. how much of the input is supporting the output). The CRM was developed for fields with minimum reservoir data, or for small fields not requiring a full reservoir simulation model, which can be time-consuming and expensive. The CRM is a quick, powerful analytical tool that is simple to use and requires readily available data. Most of the time, the injection and production rates are measured accurately and frequently, either weekly or bi-weekly. By solving the continuity equation for a homogenous reservoir (i.e. constant reservoir and fluid properties throughout the reservoir) the solution of the continuity equation can be indicative of the injection and production relation and therefore can be used to optimize injection schemes for higher ultimate hydrocarbon recovery. It is important to recognize that the CRM is not supposed to replace numerical reservoir simulators, which, in essence, are the most accurate means of reservoir performance prediction. Instead, the CRM aims to be a quick and easy way to infer reservoir performance in the absence of full-fledged simulation. The CRM has been used for several purposes as seen in the literature. First, as a tool to optimize waterflooding in oil reservoirs. The CRM can infer inter-well connectivity which will allow the engineer to adjust water injection rates to ensure uniform sweep in the reservoir and reduce the chance of early water breakthrough. The CRM was also used to optimize CO2 sequestration, whereby CO¬2 is captured from the atmosphere and stored in subsurface formations. The main hypothesis in CRM is that the characteristics of the reservoir can be inferred from analyzing production and injection data only. CRM does not require core data, logs, seismic, or any rock or fluids properties. This hypothesis can be challenged easily since most reservoirs have gradients of fluid properties, multi-porosity systems, and heterogeneous formations with different wettability presences. Albeit, several publications have shown that CRM can result in high certainty output. The objective of this report is to explain the concept of the CRM, conduct a critical review of the main CRM publications, compare CRM to other reservoir characterization tools and finally demonstrate some applications of the CRM.

The main technology used to optimize field development is hydrodynamic modeling, which is very costly in terms of computing resources and expert time to configure the model. And in the case of brownfields, the complexity increases exponentially. The paper describes the stages of developing a hybrid geological-physical-mathematical proxy model using machine learning methods, which allows performing multivariate calculations and predicting production including various injection well operating regimes. Based on the calculations, we search for the optimal ratio of injection volume distribution to injection wells under given infrastructural constraints. The approach implemented in this work takes into account many factors (some features of the geological structure, history of field development, mutual influence of wells, etc.) and can offer optimal options for distribution of injection volumes of injection wells without performing full-scale or sector hydrodynamic simulation. To predict production, we use machine learning methods (based on decision trees and neural networks) and methods for optimizing the target functions. As a result of this research, a unified algorithm for data verification and preprocessing has been developed for feature extraction tasks and the use of deep machine learning models as input data. Various machine learning algorithms were tested and it was determined that the highest prediction accuracy is achieved by building machine learning models based on Temporal Convolutional Networks (TCN) and gradient boosting. Developed and tested an algorithm for finding the optimal allocation of injection volumes, taking into account the existing infrastructure constraints. Different optimization algorithms are tested. It is determined that the choice and setting of boundary conditions is critical for optimization algorithms in this problem. An integrated approach was tested on terrigenous formations of the West Siberian field, where the developed algorithm showed effectiveness.

The paper presents the experience of using downhole microseismic monitoring to determine the direction of working agent losses while maintaining formation pressure in Baitugan oil field in Orenburg region. Studies were aimed at history matching and elaboration of the further strategy for formation pressure maintenance (FPM) and field development as a whole. The seismic monitoring method was used in the downhole version, when observations are done from the observation well located nearby the injection one. For reliable recording of weak microseismic events, high sensitivity receivers were used with 4 sensors per component. A special injection program was developed. Its first stage consisted in optimization of modes that ensure the maximum injection into formation of a fluid supplied at the wellhead. During acquisition parameter testing, passive recording of the seismic signal was done at all stages of injection during two weeks in various modes, including a short-term stop of injection with subsequent increase in injection to a maximum injection rate with exceeding the fracture gradient. Fracture growth zones were identified below the target formation. Starting from the second week of recording, fracture propagations to the overlying formations were observed under increased injection pressure. Based on data obtained, a three-dimensional map of microseismic events recorded in the formation was created. It was used for interpretation and allowed to specify geometry of self-induced hydraulic fractures depending on injection modes. Microseismic mapping of self-induced fractures in injection wells was done in Russia for the first time. The results of observations allow to optimize the formation pressure maintenance system through optimizing injection modes depending on local fracture gradients and injection shutting off in the zones with uncontrolled self-induced fractures that develop under minimum wellhead pressures. The obtained data also make it possible to significantly improve quality of history matching for carbonate deposits with reduced formation pressure through determining the injection efficiency. This result directly improves both the quality of forecast analysis and economic impact of formation pressure maintenance.

The paper describes an approach to the analysis of the efficiency of water flooding in relation to the development of the oil rim. The ways of optimizing the existing water flooding strategy are shown based on the actual operation of the wells and the forecast based on the hydrodynamic model. The issues of monitoring and control are considered as well as monitoring the operation of injection wells with the aim of subsequent operational decision-making regarding their operating modes.