In this paper, key aspects of constructing a hydrodynamic model of high-pressure air injection into Bazhenov source rocks were highlighted. Most of them are associated with the choice of pseudo-components of kerogen required to describe thermal decomposition and oxidation of kerogen and needed for construction of a kinetic model. Sensitivity analysis was carried out. As a result, high sensitivity of output to the change in the content of components reflecting the presence of kerogen in the formation and its participation in oxidation processes and thermal decomposition was confirmed.
Based on the above, a list of experimental studies was formulated, which must be carried out to determine the parameters of numerical simulation and to evaluate the effectiveness of the high-pressure air injection method.
High-pressure ramped temperature oxidation of kerogen was carried out. As a result, temperature profiles, gas composition, and volume of generated/displaced fluids were obtained. 24.8 g of water-oil emulsion were generated from 92 cm3 of rock. Kerogen in the sample was completely converted, which was confirmed by the results of conducted pyrolysis studies.
Isaev, A. A. (Sheshmaoil Management Company LLC) | Takhautdinov, R. Sh. (Sheshmaoil Management Company LLC) | Malykhin, V. I. (Sheshmaoil Management Company LLC) | Sharifullin, A. A. (Sheshmaoil Management Company LLC)
The PDF file of this paper is in Russian.
Currently the well casing is performed for different purposes:
strengthening of borehole walls in the intervals of unstable rocks;
isolation of zones of disastrous lost circulation of flushing liquid and zones of possible crossflows of formation fluid along the borehole;
separation of intervals where geologic conditions require implementation of flushing liquid with very different densities;
Separation of productive horizons and their isolation from aquifers;
formation of a reliable channel in a well for extraction of oil or pumping a fluid into the formation;
creation of a reliable foundation for installation of wellhead equipment.
The cement rock behind the casing string should be sufficiently strong and impermeable, have good adhesion to the surface of a casing pipe and to the walls of a wellbore.
Analysis of the complications regarding well strengthening shows that about 30% of wells contain water cut products due to incorrect determination of oil-water contact (OWC); 20% of the complications are due to the absorption of the grouting slurry and, consequently, insufficient lifting of cement mortar; interlayer crossflows account for about 25%, of complications, fluid kicks - 10% and 15% are associated with insufficient running of strings. Liquidation of interlayer cross-flows require significant costs that reach the average of 16% of the well cost (as regards the well stock of Sheshmaoil LLC), therefore the quality of well casing is of significant importance.
Shchetinina, N. V. (Tyumen Petroleum Research Center) | Malshakov, A. V. (Tyumen Petroleum Research Center) | Basyrov, M. A. (Rosneft Oil Company) | Zyryanova, I. A. (Rosneft Oil Company) | Ganichev, D. I. (Rosneft Oil Company) | Yatsenko, V. M. (Rosneft Oil Company)
The article addresses the evolution history of interpretation of logging data from horizontal wells in Russia and abroad. Key problems of interpreting logging data are analyzed. It also describes the application of new technologies and approaches that have increased the validity of logging interpretation. The authors substantiate the need to integrate the full spectrum of geological and geophysical information. Further ways to develop approaches are proposed.
The work deals with the problem of choosing the optimal of gas and gas-condensate wells pattern. Numbers of three-dimensional hydrodynamic models based on multi-variant calculations and economic analysis select the optimal wells pattern. However, creating a full-scale models is not always appropriate, for example, in case of low exploration at the initial development stage, the lack of investigation methods of reserves difficult to recover. In this case justification of the wells pattern should be based on other principles.
The article suggests a method of justification of the pattern arrangement, based on sectoral hydrodynamic models calculations. The advantages of sectoral models in case of low-data are the creation of local geological model based on the exploration wells data, little calculation time, interactive model changes. However, sectoral modeling has a several questions, for example the size of the sector or the boundary conditions. In the solution of the well location problem the modeling sector size determines the distance between the wells, which influences on the dynamics of wells technological parameters, the development time, cost effectiveness of the project.
The main idea of the proposed methods is to analyze of wells production in non-stationary filtration models (the maximum production rate in a minimum development time). The pseudo-stationary radius is based on the economic analysis.
Anokhina, E. (Immanuel Kant Baltic Federal University) | Zhegalina, L. (Immanuel Kant Baltic Federal University) | Erokhin, G. (Immanuel Kant Baltic Federal University) | Demidova, E. (Immanuel Kant Baltic Federal University) | Strokov, V. (Immanuel Kant Baltic Federal University) | Kozlov, M. (Immanuel Kant Baltic Federal University)
The work purpose - application of microseismic monitoring in the process of technological actions. They are directed to intensification of hydrocarbon production, by identifying fracturing zones to control the fracturing, identifying zones of emission activity in the reservoir when injecting liquid in injection wells.
A feature of this technology is the possibility of determining fracture zones using surface observation antennas, without observation wells. This distinguishes it from traditional well monitoring technologies. Also, this significantly reduces the cost of work, since there is no need to stop the wells at the time of monitoring and additionally bear the costs of lowering special equipment. This technology, in addition, has a high resolution mapping.
This paper demonstrates the approach to field development that involves geomechanical expert analysis at early stages of planning and development. One of the most important problems raised today by geomechanics experts is late involvement of geomechanical analysis and review in the field lifecycle and its usual occurrence only at the development stage. Such approach might lead to a significant reduction in the spectrum of solutions and opportunities to be used in drilling and subsequent production.
The need for geomechanics was identified early at the stage of the field development plan preparation for the V. Filanovsky Field, the largest in the North Caspian Region. Mindful of the complexity of the geological and drilling conditions of the field area, geomechanical modelling was conducted a 3D geomechanical model was built that made it possible to estimate the borehole stability of the designed wells.
The 3D geomechanical model served as a "foundation" for preparation of a field Basis of Design. It helped to identify the key elements: well design, optimized well paths taking into account the geology and unstable intervals, potential risks, multilateral well sidetracking points, drilling mud type and mud weight, etc.
As a result of an extensive multi-year study, the drilling was performed based on pre-selected and pre-computed parameters along the optimized trajectories planned as per the 3D geomechanical model. To additionally reduce potential risks, the drilling process is accompanied by real-time geomechanical calculations, the purpose of which is not limited to update of safe mud weight window model on the basis of real time data but also includes control of borehole stability, hole cleaning, differential sticking risk, cavings morphology, controlling of equivalent circulation and static density within the safe window, well path update for drillability in case of adjustments. Logging while drilling provides of critical information for permanent update of the geomechanical model and improvement of functions, which allows further optimization of well paths and the most accurate parameters of the "safe mud weigh window".
Geomechanics involvement at the Basis of Design project preparation allowed early exclusion of instability risks and identification of well drilling features that would be impossible to implement at the development drilling stage. The result currently achieved by the above effort is the possibility of drilling absolutely all wells, including extended reach (ERD) wells, without any wellbore instability-related problems. Further changes in the modelling approach will be associated to improvement of related functions to ensure still safer and faster drilling.
A reservoir optimization group has currently been formed to support the field development. The next step in the development of the geomechanical model of the V. Filanovsky field will be coupled geomechanical and reservoir modelling to make it possible to assess the impact of production on the strain-stress state of the formation and, therefore, on the reservoir properties. Updated model will also be used for planning multi-stage hydraulic fracturing in relevant wells.
Kadet, Valeriy Vladimirovich (Gubkin Russian State University of Oil and Gas, National Researsh University) | Kravchenko, Marina Nikolaevna (Gubkin Russian State University of Oil and Gas, National Researsh University) | Pavlovich, Tsybulskiy Sergey (Gubkin Russian State University of Oil and Gas, National Researsh University) | Bogdanov, Andrey Vladimirovich (LLC, Gazprom VNIIGAZ)
The development of methods of the reservoir properties laboratory determination is the current task in the complex anisotropic formations development. Current condition of the computational and experimental base allows us to develop new research algorithms that could significantly update the field standards for the study of core material with the inclusion of refined data in reservoir simulators. This paper provides generalization of core research methods developed by the authors in previous works, and improvements that clarify the characteristics and structure of the anisotropic formation have been proposed.
The obtained results of experiments with Achimov core samples permitted to specify the type of the reservoir symmetry, to modify the obtained model which provides with more qualified adaptation to history of field development and then to specify fluid filtration different directions patterns as well as stagnant zones. This method can be used for any other formations.
The essence of the experimental method is based on the analogy of the filtration and elastic properties of the porous matrix of the reservoir. The study of the motion of elastic waves along the axis of a full-size core makes it possible to establish the presence of anisotropy and to refine the type of symmetry of the properties. According to the method modified by the authors, five standard size samples (30x30 mm) were taken for the study.
Three of the five previously produced samples are used to determine the filtration-capacitive properties along the principal directions of the absolute permeability tensor, the fourth sample allows to control properties along any direction, which could experimentally show the tensor nature of permeability. This new method requires additional fifth sample, which is necessary to use in the filtration properties symmetry type experimental determination. Similar experiments were not conducted earlier. To determine the type of symmetry on five samples, high-speed gas filtration studies were performed with an output to the nonlinear filtration law and permeability was determined under the given conditions. It was necessary to carry out measurements in the forward and backward directions. Obtained data analysis made it possible to determine the filtration properties symmetry type.
The developed complex method includes creation of an algorithm for experiments carrying out and core samples filtration-capacitance properties determination and this method is generalization of previous researches. It allows determining the anisotropy type and taking this condition into account when formation modeling is in progress which was impossible previously. If this methodology is included in the modeling standards, it will let to obtain a higher degree of future development periods accurate forecasting.
Yalalova, V. (LUKOIL Uzbekistan Operating Company) | Zhukov, A. (LUKOIL Uzbekistan Operating Company) | Volnov, I. (LUKOIL Uzbekistan Operating Company) | Khakimov, A. (LUKOIL Uzbekistan Operating Company) | Ermilov, A. (LUKOIL Uzbekistan Operating Company) | Djumaev, V. (IGIRNIGM.) | Abdullaev, G. (IGIRNIGM.)
The PDF file of this paper is in Russian.
Nowadays most of the world's hydrocarbons are extracted from carbonate reservoirs and this trend will continue in the next century. However, despite a significant number of publications and scientific papers, reserves estimation and planning of carbonate reservoir development still involve a significant level of uncertainty.
Complexity of the study of carbonate reservoirs is due to the heterogeneity of pore structure media, which reduces the reliability of porosity determination and also explains the ambiguity in predicting permeability.
The problem of evaluating the pore structure of carbonate reservoirs is solved by attracting actual measurements on the core. According to the accepted techniques for preparing and examining core samples, only absolute permeability values are estimated and not effective values in reservoir conditions. For gas wells, the only reliable method for estimating the effective permeability is based on analysis of well test data and production logging data (PLT).
This article highlights the experience of applying the proposed approach to assessing the permeability and porosity of carbonate reservoirs while gas field development.
The purpose of this work is to determine the effective reservoir properties of the investigated deposits and to estimate the amount of gas initially in place.
To assess the reservoir quality heterogeneity, the analysis of well test data and production logging data were performed and intervals with effective permeability were identified. For each perforated interval the effective permeability value is determined on the basis of the actual gas production and inflow rate. To calculate the porosity of net pay intervals, the relationship between the core plug permeability and porosity was applied. Thus, to evaluate effective reservoir parameters, well test data and production logging data are used the entire life of the well, and the calculation results represent the range of porosity and permeability variation for each production interval.
The practical importance of the work is that this approach to the assessment of effective porosity and permeability allows us to identify and assess the gas reserves that will be effectively involved into the development.
Gerke, Kirill M. (Institute of Geospheres Dynamics of Russian Academy of Sciences, Schmidt's Institute of Physics of the Earth of Russian Academy of Sciences, Dokuchaev Soil Science Institute of Russian Academy of Sciences) | Karsanina, Marina V. (Institute of Geospheres Dynamics of Russian Academy of Sciences, Schmidt's Institute of Physics of the Earth of Russian Academy of Sciences, Dokuchaev Soil Science Institute of Russian Academy of Sciences) | Sizonenko, Timofey O. (Institute of Geospheres Dynamics of Russian Academy of Sciences, Schmidt's Institute of Physics of the Earth of Russian Academy of Sciences, Dokuchaev Soil Science Institute of Russian Academy of Sciences) | Miao, Xiuxiu (Key Laboratory of High-efficient Mining and Safety of Metal Mines Ministry of Education, University of Science and Technology Beijing) | Gafurova, Dina R. (Lomonosov Moscow State University) | Korost, Dmitry V. (Lomonosov Moscow State University)
Pore-level imaging and modelling were shown to be robust and useful techniques, at least if applied to conventional rocks such as sandstones. This type of modelling directly within the pore space of the imaged samples provides valuable insights into rock heterogeneity, estimates local single and multi-phase flow properties, and serves as a key tool for upscaling and parameterizing Darcian models. Yet, numerous problems are still to be solved related to rocks with complex and hierarchical structure, such as carbonates, shales and coals. These rocks possess pore sizes in a wide range of values which has to be imaged with different resolutions in order to capture all relevant pore scales. This is due to so-called sample size/imaging resolution trade-off. To develop a detailed 3D structure model, such rocks are imaged using different resolutions and even using different imaging techniques. The problem lies with combining all these multiscale images into a single 3D digital structure model. In this work the recently developed multiscale image fusion technique was tested on complex carbonate samples with hierarchical structure. For two samples we performed a detailed structural study on two different scales: 3D XCT scanning (2.7 µm resolution) and 2D SEM imaging (0.9 µm pixel size). These two scales were fused to represent carbonate rocks structure with the predefined resolution of 0.9 µm and volume of 15003 voxels combining structural features discernible on both XCT and SEM images. Fused 3D images were used as input data to a hybrid median axis/maximum inscribed ball pore-network technique with subsequent modelling of permeability. Resulting simulated values were compared with laboratory measurement on the cores with dimeter of 5 cm. For the Sample 1 micropores visible on XCT scan were not connected, thus, preventing any flow simulations. After fusion with SEM image simulated permeability agreed favourably with the measurements. For the Sample 2 micropore network was percolating, but simulated permeability was lower than the experimental one. Incorporating sub-resolution porosity in this sample by adding SEM finer porosity structure resulted in higher permeability value very close to the laboratory measurement. In this contribution we also discuss why simulated and measured permeability values do not agree perfectly, which is most likely due to the scale difference between the volumes of simulated and measurement domains. We also covered all major drawbacks of the multiscale image fusion techniques and discussed possible solutions. Current study clearly showed the potential of this novel approach to facilitate pore-level modelling of flow and transport in rocks with complex and hierarchical structure such as carbonates, shales and coals. We believe that after some improvements and rigorous testing multiscale fusion technique may become a core tool in imaging and pore-level modelling of flow properties for complex rocks with hierarchical structure.
The PDF file of this paper is in Russian.
The structure is one of the main parameters that significantly influences the reserves at additional exploration of poorly studied deep horizons of complex deposits. The results of seismic interpretation, the quality of which is affected by each stage of seismic work, are the basis for the structural framework. For deep horizons the seismic error increases, that makes the problem of taking into account the structure variation is relevant.
In this article the methodology for estimating structural uncertainty from seismic and well data is described using the example of the unique offshore oil, gas and condensate field in the Azerbaijan sector of the Caspian Sea, which is characterized by an extremely complex tectonic structure.
The deposit is associated to a ridge of anticlines of the South Caspian oil and gas basin. The target interval is deep-lying horizons of the underexplored lower interval, penetrated by only a few exploration wells on an area of more than 1000 km2. The pool altitude reaches 1,5 km, which caused a spread in the assessment of reserves of more than 50%. The uncertainty assessment of the structure was based on seismic volumes, VSP and well data.
In the process of work, a methodology has been developed that takes into account the errors in data processing, velocity model and interpretation of seismic data. The uncertainty maps are obtained differentially, then combined and taken into account at the stage of constructing the multivariate structural model.
To reduce errors in the lower interval, the data of the upper production interval were involved, the structural model of the target horizons was constructed by adding thickness maps to the reference surface taking uncertainties into account. The seismic interpretation of the upper, high-drilled production interval, located above the target at 250-1000 m, and the use of information on production wells in the upper layers, reduced the structural uncertainty for the target horizons of the lower interval by more than 2.5 times.
The analysis of uncertainties has shown that the quality of the resulting surfaces is strongly influenced by the velocity model, where the main error comes at the expense of horizons above the target interval. Using upper layers well data, construction of a structural model by adding thicknesses to the reference surface with the transformation depth errors in the thickness errors, made it possible to significantly reduce the error in the velocity model, which in turn reduced the uncertainty of the structure of deep low-drilled horizons and reduced the variance in the amount of reserves under probabilistic estimation.
As a result, was developed methodology for estimating the structural uncertainty for poor investigated deep deposits based on the differentially obtained data errors used in the interpretation. The application of this approach in additional exploration of deep reservoirs with a complex tectonic structure has allowed to reduce the spread of reserves with a probabilistic estimate of more than 20%, reliably predict the efficiency of field development and reduce risks in making reservoir management decisions.