Reservoir Pressure Maintenance Research Articles

Cyclic regulation of self-induced hydraulic fracturing cracks to improve the flooding efficiency of low-permeability reservoirs

The article is devoted to the topical issue of optimizing flooding in the development of deposits using a reservoir pressure maintenance system. In conditions of low permeability and weak reservoir connectivity, when water is injected into the injection well, when the injection pressure exceeds the pressure of rock rupture, auto-fracturing cracks occur. In order to ensure the maximum coverage factor of the reservoir by flooding during the development of the field, it is necessary to initiate and maintain the optimal fracture geometry of the auto-fracturing. The aim of the work is to analyze the modes of cyclic regulation of injection into the reservoir to maintain the optimal size of man-made cracks during the development of the field. The article presents the results of hydrodynamic modeling of flooding options with varying injection and shutdown times of injection wells, taking into account the geomechanical patterns of the spread of man-made cracks in the formation. Based on the results of the calculations performed, based on the forecast characteristics of displacement and the rate of oil extraction, the optimal modes of cyclic reservoir flooding were determined. The work is of great commercial importance, which is confirmed by the positive effect in the form of additional oil production within the framework of pilot tests of the proposed scheme. Keywords: self-induced hydraulic fracture; low-permeability reservoir; waterflood; water injection system; horizontal well; bottom hole pressure; reservoir pressure; fracture half-length; periodic injection of water.

Integrated approach to determining the effectiveness of the reservoir pressure maintenance system in carbonate reservoirs

Relevance. The need to improve the oil recovery factor from carbonate reservoirs by increasing sweep/displacement coefficients, as well as by searching for ways to improve the efficiency of the reservoir pressure maintenance system. Aim. To increase the efficiency of developing carbonate reservoirs using a reservoir pressure maintenance system through an integrated approach to studying the impact of injected fluid on reservoir systems with natural and man-made fracturing. Objects. Bashkir (C2bsh) and Vereisky (C2vr) Middle Carboniferous objects of the Dachnoe structure of the Dachnoe deposit of the Republic of Tatarstan, tectonically confined to the Ulyanovsk structure of the South Tatar arch. Methods. Seismic, acoustic, radioactive, hydrodynamic methods, as well as methods of ground microseismic monitoring to identify the nature of the activation of natural and man-made fracturing during hydraulic fracturing and cyclic injection into injection wells. Results. The authors have carried out an analysis of the hydrodynamic system of carbonate reservoirs of the Vereiskian-Bashkirian deposits; identified filtration channels; assessed the direction of injected fluid movement; carried out the analysis of the impact of the formation pressure maintenance system on producing wells at various injection modes and compensation levels in carbonate reservoirs. When carrying out hydraulic fracturing in the reservoirs under consideration, it was established that the crack propagates to both objects, thereby forming a single hydrodynamic system. The conclusions obtained from the work indicate the effectiveness of the system for maintaining reservoir pressure in these carbonate reservoirs. Clarification of data on the filtration channels of both the working agent and the oil displaced by it, in combination with knowledge of the rates of movement of the injected liquid and its distribution profiles, makes it possible to effectively manage the oil field development.

Evaluating flue gas geo-sequestration and EOR in fractured reservoirs through simulated synergistic reservoir characteristics and injection kinetics

The global reliance on hydrocarbon resources and fossil fuels has resulted in a significant surge in carbon dioxide emissions, necessitating urgent measures to mitigate greenhouse gas emissions. Integrating CO2 storage with enhanced oil recovery (EOR) presents a promising solution for reducing emissions and enhancing oil recovery by sequestering CO2 within oil reservoirs, especially in fractured carbonate reservoirs. The research utilized the Eclipse simulator to model different gas injection scenarios in a crude oil reservoir, focusing on assessing the effectiveness of CO2 and flue gas geo-sequestration and EOR, performing sensitivity analyses on reservoir characteristics, and evaluating the impact of varying injection rates on gas storage capacity and oil recovery factor. The findings demonstrated a superior capacity to store flue gas (150 MMSCF) in comparison to CO2 (85 MMSCF) and flue gas injection demonstrated better reservoir pressure maintenance than CO2 injection, while CO2 injection resulted in a higher oil recovery factor of 52% compared to flue gas injection at 36%. Additionally, analysis of reservoir characteristics in gas storage revealed that, an augmentation in reservoir porosity, permeability, and injection rate substantiated an increase in gas storage capacity for both CO2 and flue gas injection. Except for CO2 storage, which displayed a normal distribution trend in the permeability analysis. Additionally, it was elucidated that higher reservoir pressure and temperature in flue gas injection resulted in a reduction of gas storage capacity, while these variables exhibited relative stability in the context of CO2 injection. The scrutiny of gas storage in reservoir characteristics unveiled substantial alterations in porosity and injection rate, signifying their pivotal roles in influencing gas storage capacity. In the EOR study, heightened reservoir pressure, temperature, permeability, and injection rate collectively contributed to an amplified oil recovery for both flue gas and CO2, except CO2 injection demonstrated a normal distribution trend in oil recovery within the permeability analysis. Conversely, higher porosity was associated with a decrease in oil recovery. The findings of this research provide valuable insights into the feasibility and effectiveness of employing flue gas geo-sequestration and EOR in fractured carbonate reservoirs.

PHENOMENON OF BACTERIAL RESISTANCE IN OIL PRODUCTION AND GATHERING SYSTEM

In this paper, the active substances of bactericides and the mechanisms of their action are considered. Information on the mechanism of bacterial adsorption to the metal surface, which forms the most corrosive form of bacterial colonies – the adhered one – is presented. Methods of biological contamination control, both physical and chemical, are also considered. The mechanism of bactericidal action of chemical compositions consisting of 3 stages (interaction with water, interaction of bactericide aqueous solutions with bacterial cell membranes, interaction of bactericide with cytoplasmic membrane) is also reviewed. The main types of bacterial resistance common in water circulation systems, reservoir pressure maintenance systems, oil production, transportation, gathering and storage systems are summarized. The mechanisms of occurrence of each type of manifestation and method of spreading resistance between colonies are considered. It is important to note that at the moment, methods to control each of the cases of resistance when using bactericides in oil production have been poorly studied, while constant and non-alternating dosing of reagents leads to bacteria mutation and a decrease in the effectiveness of bactericidal action, which, in turn, leads to significant technological problems and economic costs. Therefore, an important step in choosing bactericides, types and methods of treating an infected environment is to study bacterial resistance. The article accumulates and summarizes information on the methods currently used to prevent bacterial resistance.

Comprehensive justification of the errors at hydraulic calculation of the reservoir pressure maintenance system

Relevance. The need to determine the permissible errors of hydraulic calculations of surface pipelines of the reservoir pressure maintenance system. This must be done, among other things, due to changes in the properties of produced water. As a result of the transition of most fields to the late stages of development, the water content of the extracted products increases, the composition and properties of reservoir waters change due to the breakthrough of the injected water. These circumstances can lead to significant changes in the mineralization, composition and Ph of water, which must be taken into account in numerical modeling. Aim. Creation of a nomogram for estimating the error in the course of changing the properties of produced water for numerical modeling of the operation of pressure pipelines of the reservoir pressure maintenance system. Methods. Hydraulic calculations in the engineering process simulator software, analysis of the properties of produced water samples in the laboratory, assessment of the density of produced water samples in the PVTSim 20 software product. Results. The studies were carried out on samples of produced water taken from seven wells. The value of salinity in the reservoir pressure maintenance system during the year varies from 247.85 to 327.79 g/dm3. The calculated density varies from 1188 to 1255 kg/m3. To calculate the pressure at the mouth of the injection well during water injection, samples with the highest, average and lowest density were taken. Analyzing the obtained data, a strong effect of water properties on the values of wellhead pressures is noticeable. On the basis of the conducted studies, a nomogram was created to determine the degree of influence of changes in water properties in the course of hydraulic calculation, taking into account the specific-injectivity index of injection wells and the length of pipelines. Conclusion. In the course of numerical modeling, it is quite difficult to take into account all the parameters that affect the accuracy of the calculations obtained. To do this, it is proposed to use the created nomogram, which allows estimating the permissible errors of hydraulic calculation taking into account the variability of the properties of water sent to the reservoir pressure maintenance system.

SELECTION OF A MRP SYSTEM FOR OIL AND GAS DEPOSITS

A number of serious problems arise in the development of sub-gas zones of oil and gas deposits due to the joint occurrence of oil and gas. The key problem is gas breakthrough from the gas cap to oil wells. This entails an increase in the gas factor (GOR), a rapid and intense decrease in pressure in the gas cap. If there is a reservoir pressure maintenance system or an active aquifer as a result of a decrease in reservoir pressure in the gas cap, oil may be pushed back into it, which leads to a rise in gas-oil contact, jamming of mobile oil in the «dry sandstones» of the gas cap, which in turn leads to a decrease in reserves of mobile oil and a decrease in the oil recovery factor (ORF). All this together allows us to consider oil in the sub-gas zones as hard-to-recover reserves.Preventing and combating the negative consequences of gas breakthrough from the gas cap to oil wells is a complex task and consists of several areas, such as selection of rational drilling of production and injection wells, selection of optimal operating modes for them, use of inflow control devices or performance of repair and isolation work to limit inflow from intervals with gas breakthrough, periodic shutdown of wells to disband gas cones. The ultimate goal of solving these problems is to increase the oil recovery factor and economic efficiency indicators for the development of sub-gas zones.Due to the variety of ways to optimize the development of oil and gas reservoirs, it is not possible to cover them all in one work, therefore, the tasks associated with optimizing the reservoir pressure maintenance system are considered. It is worth noting that in comparison with the development of oil reservoirs, the presence of a gas cap significantly complicates this task due to the lack of analytical solutions for three-phase filtration. For this reason, the selection of the optimal parameters of the reservoir pressure maintenance system is usually carried out either by multivariate calculations in the hydrodynamic model (HDM), or by the method of analogies or the implementation of pilot tests of various approaches.In this study, an approach based on multivariate numerical calculations using the sector model of the development element of the gas zone was used. As a result of calculations, it was shown that when choosing the optimal parameters of the reservoir pressure maintenance system, it is advisable to use a differentiated approach, which consists in the fact that these parameters must be set individually for zones with different ratios of oil-saturated and gas-saturated thicknesses.

ENGINEERING OF LIQUID-GAS EJECTOR USING NUMERICAL SIMULATION

The article deals with the development and application of the technology of injection of low-pressure associated petroleum gas (APG) into the reservoir through the reservoir pressure maintenance system (RPMS) in connection with the entry into force of the Russian government decree on the mandatory utilization of 95 % of produced APG. The technology under consideration, the key element of which is a liquid-gas ejector (LGE), makes it possible to achieve this level with minimal investment, in the shortest possible time and to stop flaring APG at flares remote from the central oil and gas treatment facilities of oil and gas production facilities. LGEs have a relatively simple and reliable design due to the absence of moving elements.At present, there are known LGEs of classical designs, in which the level of hydrodynamic losses can reach 40–60 %. High hydrodynamic losses make it inexpedient to use such ejectors at small fields operated at a late stage of development, remote from the central oil and gas treatment facilities, due to the limitations of the existing equipment complex and the allowed operation mode of the injection well stock. To ensure the possibility of including LGE in the RPM system it was required to develop a new design of LGE, allowing to reduce hydrodynamic losses up to 30 %, as well as to ensure the maximum possible percentage of APG utilization. The article is devoted to the development, calculation of geometry and operating mode of LGE using numerical modeling in ANSYS environment.Modeling of the flowing part of the main elements of LGE (confuser nozzle, diffuser throat and gas channel width) at different values of parameters directly affecting the level of hydraulic losses is carried out. The results of calculations of numerical simulation of LGE allowed to optimize the dimensions of the internal geometry of LGE, thus it was possible to develop a new device for the required initial data, which will reduce the level of hydraulic losses up to 30 % and ensure the involvement of the maximum volume of gas in the RPM system.

PROSPECTS FOR THE DEVELOPMENT OF THE SHEBELYN GAS CONDENSATE FIELD

The paper provides a brief geological and industrial characterization of the Shebelinsky gas-condensate field, including the height of the gas-bearing layer, the area of gas occurrence, porosity, permeability of collectors, effective gas-saturated thickness of the coppery sandstones, and araucarite strata. The peculiarity of the deposits lies in the low permeability and gas saturation, deterioration of collector properties of productive reservoirs from the lower to the upper and from the central to the peripheral part of the deposit. A structural map of the cover of coppery sandstones and a map of water saturation of all productive horizons are presented. The dynamics of gas reserves and reservoir pressures of the field over the years are shown, along with the authors; forecasts for their future dynamics. Calculations of the volumes of water saturation of horizons and the total volume of reservoir water that has invaded the gas-bearing part of the field have been conducted. An analysis of water saturation and its future prospects has been carried out. Statistical calculations of the dependence of water saturation volumes on time and reservoir pressure have been performed, indicating a decrease in the rates of water saturation at the late stage of field development. A geological section of the Shebelinsky field is presented, indicating the possibility of gas migration through tectonic faults. All factors influencing the maintenance of reservoir pressure within the deposit have been analyzed, including: contour water flooding; surface subsidence; internal waterdrive regime; the elasticity of rock formations, gas, and It is shown that drilling 12 deep wells within the Shebelinsky field did not reveal new deposits or caps but confirmed the presence of gas saturation to a depth of 5.5 thousand meters. The analysis of field development indicates a balance between gas production and its migration from deep horizons as of the year 2023. Approved development indicators and author’s options are provided, supported by actual field development. The conclusion is drawn that, due to migration with a volume of production of 1700– 1900 million m3, the field will operate for another 100 years.

Setup of PVT-models. Modeling of injection wells. Configuring models of collection system and pipelines and reservoir pressure maintenance system

Relevance. The ability to provide more accurate and efficient assessment and management of hydrocarbon production using software products for integrated field modeling. However, this approach requires an analysis of the source data quality, as well as the selection of the correct approach to creating models. Consistent and systematic work makes it possible to reproduce the actual situation with high accuracy in order to use the results obtained in further work. The integrated field model is a completely new approach to field development, when current work is based not on existing solutions, but on potential. Forecasting the behavior of the reservoir, wells and infrastructure, the collection system and the system for maintaining reservoir pressure allows for a comprehensive assessment of the possibilities of obtaining maximum oil and gas production while minimizing possible losses. Aim. Formation and analysis of an approach to setting up PVT-models of fluids, models of injection well stock, collection and transport systems and reservoir pressure maintenance systems by adapting parameters to actual data. Methods. Setting up and adapting injection well models; setting up and adapting collection system and pipeline models; approach to work with the reservoir pressure maintenance system. Results. The results obtained make it possible to adapt the components of the integrated model with an accuracy of over 95 %, which makes it possible to simulate the operating conditions of the field. Because of the analysis, tuning criteria were identified, and the minimum required set of parameters for high-quality adaptation of models was presented. Efficiency and accuracy of predictive calculations on adapted models has also been proven by comparing actual performance data with synthetic data. Based on the work done, we can conclude that the use of an integrated model shows us a high convergence with real data, which allows us to optimally approach the field development regime.

INFLUENCE OF NATURAL FACTORS OF SUPPORTING RESERVOIR PRESSURE AT THE LATE STAGE OF DEVELOPMENT OF GAS CONDENSATE FIELDS

The object of the research is natural factors that can affect both the maintenance of reservoir pressure in the process of developing gas condensate fields and the recovery of depleted deposits. Such factors include: waterflooding of deposits, subsidence of the surface, elasticity of rocks, water and gas, initial gradients of reservoir pressure in deposits, capillary forces. When studying the recovery of reserves in depleted gas condensate fields, it is necessary to take into account the influence of the above factors on the maintenance of reservoir pressure in order to identify the volumes of gas that flow from deep horizons (external sources). The paper shows the dynamics of waterflooding volumes and average reservoir pressures over the years. It is emphasized that waterflooding does not significantly affect the maintenance of reservoir pressure. Correlation dependencies of waterflooding volumes over time and the dependence of waterflooding volumes on reservoir pressure are given. An original system for calculating the volume of the water pressure system is proposed for the purpose of forecasting further waterflooding of deposits. The influences of all the above factors on the process of maintaining reservoir pressure are taken into account. It is shown that for the Shebelinsky GCF, all these factors do not significantly affect the recovery of reserves. The influence of capillary forces and evaporation of water in deposits on the development processes from the point of view of maintaining reservoir pressure at the late stage of GCF operation is studied.

STUDYING THE INFLUENCE OF NEW COMBINED INHIBITORS ON THE PROCESSES OF CORROSION AND SALT DEPOSITION IN OIL-FIELD EQUIPMENT

Aggressive salts contained in formation waters accelerate the processes of corrosion and salt deposition in oilfield equipment, which leads to unforeseen accidents, contamination of soil and groundwater with harmful substances, as a result of which the ecological balance of the environment is disrupted. Corrosion and scaling that occur during oil production create difficulties during the operation of wells, and, consequently, increase the cost of produced oil.This article covers the results of studies concerning two compositions developed from technical phosphatide - an emulsion obtained by hydration of vegetable oils, as well as sodium hexametaphosphate, ammophos and polypropylene glycol bottoms. When vegetable oils are treated with water and steam (hydration process), the phospholipids contained in the oils combine with water and are released in the form of precipitates called phosphatide emulsions. Such emulsions consist of 45–75 % water, and the rest is phospholipids in the vegetable oil sediment.Technical phosphatides are a group of esters that contain a phosphoric acid residue associated with an amino alcohol. They are natural surfactants and are non-toxic.Preliminary studies have shown that each of the chemical compounds included in the developed reagents has certain inhibitory properties, but when formulated, these compounds provide a synergistic effect.Based on the results of laboratory studies, it was found that at an optimal concentration of reagents of 200 mg/l, the developed compositions provide protection of equipment from corrosion destruction by 94–95 %, and from scaling by 87–88 %. The developed mixed-type inhibitors at optimal concentrations equally effectively inhibit both cathodic and anodic processes on the electrode.The use of these inhibitors leads to the prevention of steel corrosion in the two-phase oil-electrolyte system, as well as to a significant reduction in the rate of scaling.The proposed new compositions can be used in oil wells and in-field transport systems, as well as in reservoir pressure maintenance systems to protect against corrosion and scale deposits.Field tests of the corrosion inhibitor were carried out in deep pumping wells at the Bibieybatneft oil and gas production department. Tests have shown that as a result of using the inhibitor, the protective effect at a concentration of 200 mg/l was 89–90 %, and the effect of salt deposition was 70 %.

EFFICIENCY OF COMPLICATED WELL STOCK OPERATION

One of the key problems of the oil industry is the of asphalt-resin-paraffin deposit (ARPD) formation which affects the efficiency of well equipment operation. This leads to significant economic losses during extraction and transportation of products. In conditions of a reduction in the resource base of liquid hydrocarbons, the inability of constant monitoring the well operation process becomes a critical factor for the technical and economic aspects of the activities of oil and gas production departments. The factors influencing the intensity of ARPD formation including changes in the characteristics of productive formations and the use of reservoir pressure maintenance are analyzed. The need to ARPD control within the framework of various systems and geological and technical measures is important for effective control of sediment intensity. Taking into account the nonlinearity of the ARPD formation process is a key point in solving urgent issues of well safe operation. An integrated approach taking into account the peculiarities of the ARPD formation at various facilities to increase the efficiency and durability of downhole equipment is recommended.

Power consumption of electric centrifugal pumping plants under extraction of highly watered oil

Relevance. Currently, oil fields in Russia are mainly developed using the method of artificial maintenance of reservoir pressure to achieve high oil recovery. The use of artificial impact on productive formations by the method of water injection contributes to the premature irrigation of production wells. Water content of productive layers in oil fields significantly complicates the technology of oil production. With the increase in water content of the surface fluid, the power consumed by the engine increases. Minimization of energy consumption is quite relevant, as oil is produced with significant expenditures of electrical energy. It is important to investigate the dependences of the electric energy consumption on the well water cut. Aim. To study the dependence of energy consumption of submersible electric centrifugal units operated in oil production wells on water cut. Methods. Submersible electric centrifugal installations for oil production. Results. In order to study the effects of formation water cut on electrical energy specific consumption, wells with a water cut of more than 90% were selected. Using the formula, the authors have calculated the electrical energy specific consumption for oil production. The analysis of the results of the calculated data showed that in producing wells with a water cut of up to 90 %, the average specific electric power consumption for oil production is within the recommended standards. In wells with the water cut more than 90%, the average specific electric power consumption for oil production exceeds recommended specific norms of electric energy consumption during operation of oil producing wells equipped with electric centrifugal installations. Based on calculated data, the dependence of the specific electrical energy consumption for oil production on the water cut of reservoir products was plotted, and wells with a water cut of more than 90% were selected. The analysis of the graphical dependence showed that in wells with an oil water cut of more than 90%, the specific energy consumption reaches maximum values ​​(the specific energy consumption increases by 40%).

Research of numerical indicators for the development of the Asselskaya area of Orenburg oil and gas condensate field using the material balance method

The purpose of this work is to analyze and forecast the development indicators of the Assel deposit of Orenburg oil and gas condensate field. To complete this task, a large amount of data is required, which was obtained from the technological development project. The calculation is performed using a program written in the Python programming language. The variables for the material balance equation are given, some of them are calculated using intermediate formulas. The average values of the parameters over the last 15 years of development were chosen as the optimized parameters, since small amounts of cumulative production in the first years of development can lead to a significant error in the calculation of the material balance equation. Also, a comparison was made of the estimated forecast for the development of the Assel deposit with the forecast, according to the state plan, presented in the field development project. The comparison was made on the main parameters: cumulative oil production, annual oil production, oil recovery factor and water cut. For a visual comparison of the calculated parameters, dependency graphs are presented that reflect the forecast made by the material balance method, as well as the forecast based on the data of the state plan. The difference in the behavior of the curves shown on the graphs can be explained by the inaccuracy of the parameters describing the reservoir, as well as the inaccuracy of determining the initial recoverable reserves. This is also affected by the difference in reservoir drawdowns for injection and production wells, proposed in the state plan and in the forecast. Of course, the inaccuracy of the injectivity and productivity coefficients of wells, which were selected based on the estimated volumes of water injection and oil production, also affects. Based on the calculation performed, it can be concluded that it is expedient to further exploit the Asselskaya area of Orenburg oil and gas condensate field with the introduction of a reservoir pressure maintenance system until 2079. According to the forecasts, the water cut equal to 96% will be achieved in 2079, while the oil recovery factor will be 0.427.

Design and research of the plunger pump mechanism for pumping liquid in reservoir pressure maintenance systems

Nowadays, plunger pumps have the most advanced designs. In fact, plunger pumps are the only ones of their kind, capable of operating at high pressures and have the best characteristics. Their use is growing in industry, as they cope with the harsh conditions of pumping liquids of various types. To maintain reservoir pressure, pumps require a high efficiency and reliable design. In order to ensure the operability of the system, it is necessary to select qualitative indicators according to the criteria of optimality for the design of mechanism parts and to achieve an adequate workflow. Thus, the study and determination of the possibility of improving the performance of plunger pumps remains a current task. The results presented in this article include an analysis of the operating conditions of each of the components of the mechanism using a mathematical model of the drive based on the differential equations of motion of the plunger pump, the determination of the corresponding production processes and the production of finite elements. In addition, a kinematic force analysis of the functions of the mechanism under study (positions of analogues of speeds and accelerations of links) and the found motion characteristics is carried out when solving the problem of dynamics of the main shaft of the machine. This article presents a test report to verify the correct functioning of the mechanism in accordance with the initial parameters of the system, the design of a gear planetary gearbox with cylindrical wheels, a cam mechanism pusher and their type of assembly to be performed. This research is carried out using software for engineering mathematics: Mathcad and Python.

RESEARCH OF FORMATIONS INJECTIVITY IN ORDER TO ORGANIZE RESERVOIR PRESSURE MAINTENANCE IN THE CARBONATE FIELDS

In this item, the top-priority is organization of reservoir pressure maintenance system and fields development under natural mode in order to maintain reservoir pressure in carbonate fields. Currently, the fields are being developed in a natural drive, and arranging a system for maintaining reservoir pressure is a top-priority. Carbonate fields are complicated by tectonic faults in the separate blocks and HC production reveals disturbance of the balance in the geological environment. Longtime fluid sampling without reservoir pressure maintenance leads to change of stress fields in formation, which initiates creation of deformations of earth surface. In order to prevent from these events, it is required to maintain reservoir pressure. It is necessary to maintain reservoir pressure to prevent these events from happening. When water is injected, migration occurs through a complex ramified system of cracks, caverns and pore channels. The most permeable in the productive thickness layer are karst intervals and zones of increased fracturing, which serve as the main routes for fluid migration. Considering complication of RPM system organization due to high wellhead pressure, field distance from water sources and possible creation of cavity and carst, conception of carbonate fields development is developed within the frame of item.

FORECASTING ORF BY THE MARTOS METHOD AND THE STATISTICAL METHOD USING THE EXAMPLE OF DEPOSIT X

The article discusses the effectiveness of the Martos method and the statistical method for predicting oil recovery factor using the example of the X field. Today's values of oil recovery factors (ORF) for Triassic horizons were determined taking into account the active water pressure regime with artificial maintenance of reservoir pressure (RPM) and the drilling of 16 new production wells. This approach required a revision of ORF values due to the transition to natural reservoir development and the cessation of maintaining reservoir pressure by water injection. The failure to drill new wells has also had a significant impact on ORF. At current production, when 44.7% of the field's reserves have been extracted, and taking into account the remaining reserves, the development period of the field will not exceed 42 years. It is also planned to increase the number of hydraulic engineering measures to expand drainage zones and involve additional reserves in development. Having compared the two methods for calculating ORF, we can conclude that although V.N. Martos’ method is based on reservoir parameters, and the statistical method uses historical data, the results of their calculations differ slightly.

Efficiency improvement of Bactericides and Biostats Application when Using Seawater in a Reservoir Pressure Maintenance System

The article presents materials on the classification of groups of corrosion-hazardous bacteria developing at oilfield facilities, classification of oil fields by microbiological problems, critical points for the development of sulfate-reducing bacteria, as well as classification of methods to combat microbiological corrosion. The effect of UV irradiation on the inhibition of microorganisms is also described. The proposals of the Gubkin Institute on the joint application of biocides, biostats and UV irradiation to combat sulfate-reducing bacteria are given.

About flooding of low-permeable formations

Due to the depletion of hydrocarbon reserves in traditional reservoirs with good filtration and reservoir properties, there is currently increasing interest in hard-to-recover reserves, and the main difficulty in developing such reservoirs is the efficiency of reservoir pressure maintenance systems. When developing low-permeability reservoirs, various mechanisms of oil displacement during flooding can be distinguished. For reservoirs with permeability less than 1 mD, there is no need to maintain high wellhead pressure; moreover, with a large accumulated compensation, stopping the maintenance of reservoir pressure for up to six months does not lead to a drop in production, which creates the prerequisites for organizing cyclic flooding. This will solve a number of problems that arise while maintaining reservoir pressure when working in such conditions.
 The facies structure of reservoirs sometimes has a decisive influence on the performance of wells and their interinfluence. The transition to the development of fields with a complex geological structure, low filtration characteristics of the formation, the existence of geological bodies with different properties requires not only careful formation of a conceptual understanding of the field, but also the creation of detailed facies digital maps taking into account the existence of zones with different sedimentation, which, as a consequence, creates zones with different filtration and capacitance properties, requiring different approaches to development.

Increasing the efficiency of bactericide use when using seawater in a reservoir pressure maintenance system

Rationale: Since 2018, at the Uzen oilfield, in order to study and control the microbiological contamination with sulfate-reducing bacteria (hereinafter referred to as SRB) of oilfield environment, full-scale bactericidal treatment and monitoring of the effectiveness of reagent use have been carried out. At the equipped control points, water samples are taken for the content of SRB cells before and after injection of the bactericide.
 Target: Reduce the intensity of sulfidogenesis at the oilfield and, as a consequence, the concentration of hydrogen sulfide in the associated gas.
 Materials and methods: Since the applied technology of injecting the bactericide in shock dosages did not allow achieving a stable reduction in the concentration of hydrogen sulfide, it was replaced by the technology of constantly injecting the bactericide into seawater at a dosage of 40 mg/l in an experimental mode. This technology showed low efficiency, hydrogen sulfide (H2S) concentrations varied between 352–379 ppm, and the monthly consumption of the reagent increased by 40%. Based on the obtained data on ineffectiveness, the constant injection of bactericide at MPS-4 was stopped and a new technology for injection of bactericide was proposed, aimed at suppressing not only planktonic, but also adherent forms of SRB.
 Results: Results. Injection of the bactericide using the new technology showed significant efficiency, which was assessed by reducing the concentration of hydrogen sulfide in the associated gas by an average of 45% across the oilfield.
 Conclusion: The proposed new technology for injecting a bactericide made it possible to effectively suppress the activity of sulfidogenic microorganisms and reduce the level of biogenic hydrogen sulfide in the oilfield.