Background. The results of well tests in fractured oil and gas reservoirs are characterized by a wide range of responses on the diagnostic plot of the pressure derivative. Detailing of the responses makes it possible to evaluate the fracture structure and its variability during well operation and due to well interventions. Objective. To assess the nature of changes in the fracture structure of a carbonate reservoir at different stages of the cyclic geomechanical treatment. Materials and methods. Fractured oil and gas reservoirs. Interpretation methods, analytical and numerical simulation of pressure buildup curves. Comparison with literature data. Results. Based on the analysis of actual well test results, their comparison with literature data and model simulations, the possibility is justified to analyze changes in the fracture structure when applying geomechanical treatment methods. As an example, interpretation of pressure buildups recorded at different stages of the cyclic geomechanical treatment on a carbonate reservoir is considered. The use of an integrated methodology made it possible to assess the nature of changes in the extent of developing fracture zones and their structure. Conclusions. An integrated approach to performing and interpreting well tests in fractured reservoirs, detailing responses and assessing their changes based on repeated test data, enables monitoring of the fracture structure during well operation and after well interventions.
Background. Low-permeability reservoirs and reservoirs containing high-viscosity oil are increasingly becoming objects of development due to the deterioration of the reserve structure and a number of negative factors. As a result, the time for the logarithmic derivative of pressure to reach radial flow conditions significantly increases, making it impossible to interpret the pressure buildup curve within an acceptable research time. Objective. To develop and summarize recommendations for the pressure transient analysis in reservoirs with low mobility coefficients. Materials and methods. To solve the set task, known and author-developed methods of interpretation and hydrodynamic research were used. Results. It is shown that the most optimal methods are the following: the drawdown curve instead of pressure buildup curve, the usage of flow models preceding radial flow when interpreting pressure curves for wells with complex geometry and the already traditional interpretation of long-term pressure data using pressure downhole gauges. Conclusions. The proposed methods allow for a reduction in the scheduled shutdown time of well during well test and consequently reduce losses in oil production when solving the problem of determining the filtration parameters of the reservoir and the near-wellbore zone.
Background. Achimov sediments of the north of Western Siberia have a complex geological structure, which together with extremely low filtration-capacity properties creates problems in understanding the spatial distribution of oil- and water-saturated intervals in an oil deposit. Objective. Construction of a conceptual reservoir model describing the uneven distribution of oil- and water-saturated reservoirs along the section. Materials and methods. The object of the study was sandy-clayey layers of clinoform structure of one of the fields in the north of Western Siberia. The methods of studying sedimentological, lithological-petrophysical, capillary pressure and filtration characteristics of the reservoirs and the results of well logging were used. Results. The problem of obtaining water-saturated oil inflows from intervals at the top of formation within the expected zone of single-phase oil filtration was analyzed. A complex capillary-filtration model of the reservoir describing the structure of such deposits is proposed. Conclusions. The constructed model of the studied object explains the presence of intervals of water-saturated reservoir (subreservoir) at the top of formation and allows to establish the cause of high initial water cut during testing and operation of wells.
Background. Assessment of abnormal pressures during well drilling operations still remains an urgent task, as it allows ensuring accident-free well drilling and increasing drilling efficiency. Objective. To assess and forecast abnormal pressure conditions in areas of abnormally high reservoir pressures in terrigenous sediments, considering pressure growth with depth. Materials and methods. The research is based on the following materials: advanced logging while drilling and well logging data, exploration geophysics surveys, core material analysis results and drilling operation data. Results. The research findings, their detailed analysis and generalization for over 400 wells are applied in well planning, design and drilling operations across various regions. The main trends in the variation of abnormally high pressures across the area and stratigraphic section are described. The study presents the main characteristics and application possibilities of advanced logging while drilling and well logging data, as well as exploration geophysical methods (electrical prospecting and seismic surveys) in the analysis and forecasting of abnormally high pressures. Furthermore, the principal methods and methodologies for pressure determination and forecasting are reviewed. Conclusions. The relationship between pressure and depth follows a universal pattern, demonstrating a global planetary character. The main reason for abnormal pressures is rock compaction. However, deviations from this general principle exist in the form of localized areas with abnormally high formation pressures shaped by distinct influencing factors. Any alterations in rock properties, whether due to technological processes or geological factors affecting fluid volume in a sealed reservoir, result in pressure changes within these rock formations.
Background. The research topic is relevant due to the need to clarify the geological structure and assess the oil and gas potential of the Bazhenov Formation in Western Siberia. Objective. To present a method for estimating the component composition and the total organic carbon content of the Bazhenov Formation, as well as to verify the convergence of the test results of the methodology with core data by calculating a volumetric sediment model. Materials and methods. Results from an extended suite of well logging operations conducted in the final logging interval; results of laboratory core analysis from the Bazhenov Formation interval (density, acoustic, pyrolysis and X-ray diffraction studies). Results. A method was developed for determining components of the Bazhenov Formation deposits, based on calculating clay and total organic carbon content using a hydrogen-index petrophysical model. The obtained results enabled the creation of a detailed 3D model of the anomalous section of the Bazhenov Formation of the survey area, identification of the most promising development intervals, and conclusions about saturation characteristics. The findings were confirmed by pilot production tests of productive formations in well X of the survey area. Conclusions. The proposed method for calculating the content of sediment components of the Bazhenov Formation makes it possible to determine with a high degree the filtration and capacity parameters of the medium with the release of solid organic matter from the pore space, which is necessary to isolate permeable intervals containing mobile oil.
Background. In view of the introduction by the Federal Agency for Mineral Resources of the new regulations of well testing from 1 October 2023, the article considers the issues of technological support of the requirements for the coverage and frequency of instrumental control of the production of recoverable oil reserves during the development of raw hydrocarbon deposits, provided by the regulations. Objective. To develop recommendations to oil companies and subsoil users on fulfillment of the requirements of the new Regulatory Document in conditions of development of highly watered fields under conditions of oil displacement by low-mineralized waters. Materials and methods. The use of logging and production logging methods is shown using the examples of typical Neocomian deposits in Western Siberia. Results. The problem of low quality of hydrodynamic models due to nonuse of well surveying data is analyzed. In conditions of low mineralization of invading waters, low reliability of carbon/oxygen logging is shown. It is proved that oil companies have the opportunity to rely on the on the information content of “active” neutron logging (with artificial injection of mineralized salt solutions), as well as on the interpretation of logging complexes in newly drilled wells. Conclusions. The cardinal solution to the problem of controlling the development of recoverable reserves and, as a result, ensuring the oil recovery factors approved in the new regulations should be observation nonperforated wells with fiberglass or metal liners under conditions of their monitoring by logging and production logging methods.
Background. Formation evaluation and well testing are key to meeting the challenges associated with oil and gas field development. Selection of the most efficient and informative method always involves consideration of technological and process specifics for each particular case. Objective. To present a comparative analysis of the efficiency of well testing methods to identify the optimal conditions for application of each method in terms of several criteria: test period, scope of information obtained, production losses, reservoir pressure and productivity index estimates. Materials and methods. The paper presents the results of two well testing methods: pressure buildup analysis and inflow performance relationship curves. These tests were conducted as prescheduled and according to developed test design in 16 wells equipped with sucker rod pumping unit. Results. Beneficial and negative factors for well testing procedure and performance were determined. Conclusions. The present research is based on practical field test results with comparative analysis of technological and process factors influencing well testing methods and can be used as basis for selection of tests for a particular well.
Background. When designing the field development and clarifying the geological and hydrodynamic model, information about the conductivity of identified faults using seismic studies is needed to assess the interaction between wells located in different blocks. Considering the complex structure of the reservoir (with numerous faults), the long distance between wells and the variability of solutions in response to signals reflected from multiple boundaries, solving this problem by using well testing methods is significantly more difficult. Objective. To develop approaches that significantly reduce the uncertainty in assessing the configuration and conductivity of faults in the well influence zone. Materials and methods. The information obtained from long-term monitoring of flow rate and bottomhole pressure in two wells was used. The presence and conductivity of faults was assessed using well testing methods and specialized software for their interpretation. Criteria for quality were introduced, according to compliance/noncompliance with which a decision was made on the correctness of using a particular model. Results. Using two wells as an example, the application of factor analysis to exclude the least probable models of fault configuration and conductivity is shown. The method of excluding inappropriate or less reliable interpretation models solved the problem of confirming the presence of faults, their number, distance from the wells to them, and their conductivity. Conclusions. The presented approach demonstrates the possibility of significantly expanding the scope of application of analytical models for solving complex geological and hydrodynamic problems.
Background. The article presents the results of analyzing pressure stabilization and recovery curves in multibranched horizontal wells. It has been noted that the diagnostic graphs of bottomhole pressure derivatives in such wells are complicated by sections of V-shaped form. Such specific features of actual measurements require mandatory consideration during their subsequent interpretation. Objective. To identify the circumstances that cause the presence of V-shaped sections in the diagnostic graphs of bottomhole pressure derivatives. Materials and methods. The primary tools for analyzing the initial data included methods of systematization and generalization, as well as processing techniques using mathematical statistics and numerical modeling, including with the use of KAPPA Workstation software version 5.40. Results. It was determined that the number of ranges with V-shaped behavior of the derivative corresponds to the number of drainage outlets from the main horizontal borehole, and the distance between them is controlled by the length between lateral branch connections. The possibility of mathematically describing these sections using available analytical models “Fishbone” and “Multi-branch” was assessed. Conclusions. The calculations show that these models, given the current set of active functional options, do not provide an acceptable match between calculated and actual stabilization and recovery pressure curves, as they do not fully reflect the features of real measurements. As an alternative, a numerical model reproducing the dynamics of bottomhole pressure in stopped and closed multibranched horizontal wells is presented. Comparison between recorded data from deep instruments and model curves demonstrated the adequacy of the created digital analogs of pressure response, which can be used for developing algorithms to assess reservoir properties.
Background. The modern oil industry is paying more and more attention to increasing the oil recovery of hard-to-recover reserves. The results of a few field tests without application of geological and technical measures for flow stimulation limit the possibility of substantiating criteria for selecting promising areas for development and pilot operations. The study of the rock features of the Khadum Formation (Р3hd) of the East Pre-Caucasian oil and gas region was carried out using data from core samples with ultralow filtration and capacitance properties. It is proposed to substantiate and use certain geochemical properties of rocks and organic matter and pyrolytic parameters as indicators of oil content. Objective. To study the variability of the geochemical properties of the Khadum deposits and identify the dependencies between them for the subsequent identification of the most promising oil and gas zones according to a group of geological and geochemical criteria. Materials and methods. The paper presents the geochemical characteristics and comparison of the main pyrolytic parameters for rocks of the Khadum Formation. Pyrolysis data (by the Rock-Eval method) from core and field information from oil fields were used. Results. The predominance of two types of kerogen was established and two types of rocks with different hydrocarbon potential were identified. The distribution schemes of the main geochemical characteristics of the Khadum Formation and the distribution of established rock types with different hydrocarbon potential within the Eastern Pre-Caucasus are compiled. Conclusions. A new approach to identifying the most promising oil- and gas-bearing areas within the Khadum Formation on the basis of geochemical criteria is proposed, based on the identification of two types of reservoir rocks with different hydrocarbon potential in terms of S1, S2, Тmax, HI and OSI parameters.
Background. Currently, when solving the tasks of exploration of territories, the possibility of using the 3D seismic survey method and modern interpretation of its results for increasing efficiency in the development of oil and gas fields is becoming increasingly important. There is a problem in the fields related to the forecast of promising zones of reservoir rock development based on borehole data and the results of interpretation of seismic exploration. Objective. To increase the reliability of the forecast of effective thicknesses in the studied area of the deposit. Materials and methods. The work uses the results of interpretation of borehole and seismic data, multiple regression methods, machine learning technologies and neural networks. Results. Several algorithms for obtaining predictive maps were compared. The comparison results were compared with the values of the borehole data, and the most reliable result was selected based on the correlation between the borehole data and the forecast map based on the root mean square error. Conclusions. The chosen approach made it possible to obtain a reliable and refined thickness forecasting result to increase the efficiency of field development. The obtained data are planned to be used in the further development of the field.
Background. The article considers the problem of oil production from the Bazhenov Formation, the recoverable resources of which are estimated to reach 20 billion t. Objective. To analyze the known methods of enhancing oil recovery in the Bazhenov Formation and to consider the prospects for using the technology of ultrahigh frequency electromagnetic action on the formation. Materials and methods. The object of the study is one of the lithotypes of the Bazhenov Formation – black bituminous argillite. Experiments were carried out on thermal and electromagnetic action of ultrahigh frequency with recording of changes in the qualitative and quantitative characteristics of the experimental samples. Results. Changes in the structure of the void space are documented using digital models. According to the results of laboratory studies, it is noted that the structure of the void space can be affected by such geochemical characteristics as bitumen and organic carbon – their spatial distribution and quantity. The prospects for using ultrahigh frequency electromagnetic action on the formation, the advantages and disadvantages of other methods are presented. Conclusions. The potential effects of enhanced oil recovery methods will be controlled not only by the time and degree of energy impact on the reservoir, but also by the geochemical characteristics of specific deposits. The industrial technology of microwave impact on target reservoir intervals is proposed to be developed, as it appears to be more environmentally friendly and energy efficient.
The article considers the problem of isolation of water and gas inflow in horizontal wells of carbonate fields, especially in the Kuyumbinskoye oil and gas condensate field. Objective. To develop a new silicone composition for sealing in the conditions of fractured reservoirs. Materials and methods. Laboratory and field studies were carried out, including compatibility tests with formation water and oil, as well as strength and filtration tests. Results. The studies showed high chemical compatibility of the formulation with fluids and rapid formation of an isolating mass. In the field, the composition proved its effectiveness when injected into wells with water and gas inflows. Pre- and post-treatment monitoring confirmed flow reduction. Conclusions. The composition enhances insulation durability, lowers operating costs and minimizes environmental impact.
Background. The paper examines the possibility and features of implementing the geostatistically consistent history matching of a reservoir model using reservoir flow simulation software. This approach assures maintaining the principles of the geological model creation during the solution of the inverse problem. For comparison purposes, a previously known test model is used implementing similar approach using author-developed algorithms. Objective. To analyze features and limitations of the geostatistically consistent automated history matching of a 3D model using a commercial simulator. Materials and methods. Synthetic 3D model of a heterogeneous reservoir, tNavigator reservoir flow simulator with built-in automation and history matching tools, geostatistical methods. Results. The geostatistically consistent automated history matching procedure is implemented in tNavigator on a synthetic model of a five-spot waterflooding element. The errors in the recovered values of the synthetic model parameters are analyzed depending on the final value of the objective function (measurement accuracy) and initial guess. Conclusions. It is possible to implement the geostatistically consistent history matching procedure using the automation tools of modern reservoir flow simulators. However, the built-in automated history matching algorithms do not provide enough efficiency for application to real reservoirs without using proxy models.
Background. When using geological hydrodynamic models for analysis and engineering, phase permeabilities are of key importance in field development. Traditional approach to determining these parameters through laboratory core tests often does not display sufficient accuracy, so an alternative technique for determining phase permeabilities is proposed. Objective. This study is intended to clarify the phase permeability relationships in the forecast calculations of field production and assessment of the success of geological and technical measures (bringing-in of infill wells, repeated hydraulic fracturing) without using irrelevant data from core studies. Results. A technique was formulated for obtaining relative phase permeabilities from field development data, deciphering the results of hydrodynamic testing of the corresponding wells and forming a numerical model for the development object. This technique was tested on a real development object (the southern part of the Priobskoye field). Conclusions. The technique can be used to model oil fields. In comparison with the classical approach of determining relative phase permeabilities by core, this method allows us to get rid of the scaling effect and get relevant dependencies for the entire development object.
Background. The paper analyzes the geomechanical processes that cause the destruction of the bottomhole zones of wells and their annular space during the operation of underground gas storage facilities. The destruction of rock in the bottomhole zones of wells leads to the intensive removal of particles of destroyed rock (sand) into the wellbore and further to its mouth, reducing well productivity and leading to intensive wear of well equipment. The destruction of cement stone in the annular space of the well leads to its depressurization, gas ingress into the upstream permeable layers and to the Earth’s surface, which, in addition to the loss of hydrocarbon raw materials, can lead to environmental problems. Objective. To analyze the mechanisms of rock destruction during gas injection into underground gas storage facilities and develop approaches to reducing the intensity of such destruction. Materials and methods. The work uses methods of mathematical modeling of the stress-strain state of rocks. Results. It is shown that the processes of rock destruction occur most intensively during the period of gas injection into underground gas storage facilities, characterized by extremely high values of reservoir pressure in the bottomhole zone of the well. The growth of reservoir pressure initiates the process of development of destructive stresses in the rock and in the cement stone in the annulus of the well, as a result of which there is a loss of adhesion of the cement stone to the rock and the development of cracking processes in the vicinity of the uncased part of the wellbore, which is a prerequisite for intensive sand removal during further operation of the well. Conclusions. It is established that in order to reduce the intensity of excess destructive stresses in the rock and cement stone, it is advisable to gradually increase the gas injection pressure into the storage facility, with the duration of each stage determined by the time it takes for the injection process to reach a quasi-stationary mode. It is shown that installing a cemented spring centralizer in the roof above the productive formation during well construction during the operation of underground gas storage facilities will also contribute to a significant reduction in the intensity of destructive stresses in its near-wellbore zone.
Background. In the absence of a geologically sound mechanism for the introduction of water into a gas reservoir and a confident a priori localization of potential flood zones, the adaptation of hydrodynamic models has to be carried out based only on borehole data, which entails a high degree of uncertainty, and therefore high prognostic risks. Objective. Reduction of prognostic risks when choosing a pilot production site to increase the component recovery of a field (including by extracting the “matrix” oil of its gas part). Materials and methods. Analysis of the geological and technological prerequisites for massive premature (compared with early design documents) water occurrence in gas wells of the Orenburg oil and gas condensate field from the perspective of modern geodynamic processes developing in a carbonate reservoir with a high degree of bituminosity, principle hydrodynamic modeling. Results. Understanding the geological diversity of the mechanisms leading to water occurrences in the gas wells of the Orenburg oil and gas condensate field makes it possible to create a set of fundamental hydrodynamic models for various reservoir sites. This reduces the uncertainty in the identification of remaining locally trapped gas volumes and the level of risk in the event of an improper selection of a site pilot production for increasing the component recovery. Conclusions. It is assumed that various mechanisms of well flooding were triggered by the attempts to create a gas condensate storage by an explosive method on the eve of development, at the stage of oil and gas condensate field development, in the Kungur salts of the caprock of the Central Dome.
Background. Hydrogen is given the role of a clean energy carrier in the energy transition. Objective. To identify relevant research topics based on pooled bibliometric data of the International Journal of Hydrogen Energy publications from 2022–2024, collected from The Lens and ScienceDirect platforms. Materials and methods. 10,928 bibliometric records were exported from The Lens database and 10,857 records were exported from ScienceDirect. Keywords clustering and visual data analysis were performed using the following programs and algorithms: VOSviewer, Scimago Graphica, Inkscape, FP-growth utility. Results. The study showed the feasibility of merging bibliometric records from the open platforms ScienceDirect and The Lens, which complement each other. The “Fields of Study” data of The Lens was interpreted as system keywords similar to Scopus Index Keywords. The possibility of using “Fields of Study” data in a method similar to bibliographic coupling is shown. The practicality of using an alluvial diagram to show the co-occurrence of the four terms was demonstrated. The study also emphasizes the advisability of joint use of VOSviewer and Scimago Graphica programs for complex visualization of bibliometric analysis results. The study identified two dominant publication topics in the International Journal of Hydrogen Energy for 2022–2024, which can be described in terms of: “Catalysis, Hydrogen, Physical chemistry, Chemical engineering, Nanotechnology, Electrochemistry, Organic chemistry, Materials science” and “Electrical engineering, Hydrogen production, Renewable energy, Environmental science, Hydrogen economy, Hydrogen, Engineering”. Conclusions. Joint use of metadata of different open abstract databases allows to compensate partial representation of their data.
Background. Increasing the profitability of oil and gas fields at the late stages of their life cycle requires the involvement of additional technological solutions for the development of the mineral and energy potential of the geological environment. One of the affordable, low-cost, geologically and economically justified solutions may be the extraction of strategically important components from groundwater infiltrating the deposit in the course of reservoir pressure drop. Objective. To analyze the hydrogeological conditions of the Mirny arch as a region within which combined extraction of hydrocarbons and industrially valuable components of formation waters is possible. Materials and methods. The study drew on the factual data on formation pressures, hydrochemical composition of groundwater of the Mirny arch, which has a high oil and gas potential, as well as the possibility of developing hydromineral resources. Standard methods of processing hydrochemical materials, hydrochemical modeling, calculations of hydrodynamic potentials were used. Results. The main features of the dynamics and composition of groundwater in the Mirny arch, which can be used as hydromineral raw materials, were identified. The waters of the Vendean complex were noted to contain iodine (up to 13.5 mg/dm3) and bromine (up to 5,260 mg/dm3), lithium (up to 10 mg/dm3), strontium (up to 2,500 mg/dm3) and rubidium (up to 3 mg/dm3) in commercially viable concentrations. Conclusions. Significantly, the hydrocarbon fields of the Mirny arch exhibit sharp geofluid dynamic heterogeneity due to tectonic blockiness. This allows simultaneous independent production of hydrocarbon and hydromineral raw materials, as well as solving the problem of utilization of waste water in local conditions. For a full scientific substantiation of the prospects for using the groundwater of the Mirny Dome deposits as hydromineral raw materials, it is necessary to develop and implement a program of detailed work to clarify the hydrochemical and hydrodynamic parameters of the reservoir systems, as well as geological and economic assessment of the profitability of extraction of industrially valuable trace elements.
