bluuebunny/crossref_metadata_2025 huggingface dataset:
Reservoir Connectivity and Compartmentalization Detection with Down Hole Fluid Analysis Compositional Grading
Authors: Gusev Sergey , Garaev Azat , Zeybek Murat , Kazakevich Eduard , Tsiklakov Alexander , Charupa Mikhail , Novikov Sergey
Published: September 2020

Kharyaginskoe field is located on the North part of Russia and produced by Zarubezhneft-Production Kharyaga company. The field is on the mature stage, so, it requires the special attention to drilling and production strategies optimization. The field is highly complicated by geological nonconformities (for example, faults), which has the crucial impact on the well productivity, recovery and reservoir management decision. So, the comprehensive understanding the zones complexities such as connectivity and compartmentalization is vital for optimal field development and has always been extremely challenging. The traditional method of using formation pressures for evaluation of reservoir connectivity does not perfectly work for the reservoirs under production as the fluid extraction disturbs the initial pressure equilibrium. This study shows another possible methodology of reservoir connectivity examination based on the analysis of hydrocarbon composition for three zones of Kharyaginskoe field.
Performance Monitoring of a Group of Yarudey Field Wells by Means of an Advanced Diagnostic Including Passive Acoustics and Temperature Modelling
Authors: Naymushin Anton , Zaripov Rustam , Aslanyan Irina , Kirpichikova Elena , Konovalov Stanislav
Published: September 2020

Flow and injection profile monitoring in horizontal wells enhances the oil and gas field development efficiency, which is of particular importance when the target reservoirs have a complex geological structure, as is the case with oil-rim reservoirs located below a gas cap. The objective of this paper is to present the results of multi-well diagnostics carried out in order to estimate the flow and injection rates in Yarudey Field wells (Russia) and assess the downhole completion integrity status.

When developing oil-rim reservoirs, flow and injection profiles need to be closely monitored so that gas and water breakthroughs along the length of thin beds and fractures could be promptly detected and appropriate remedial jobs planned. This task becomes more challenging in completions where multistage hydraulic fracturing was earlier performed, or the wells were cased with uncemented liners equipped with swell packers. To monitor the reservoir performance, advanced downhole diagnostics was performed in a group of wells in the field, where such reservoir-oriented techniques as passive acoustics and high-precision temperature logging were used. Application of the passive acoustic logging technique helped to identify reservoir flow zones and detect crossflows behind casing. The flow and injection rates were estimated through temperature simulations. Both these techniques were found to be useful, including those instances when the integrity of complex downhole completions was to be assessed. On the whole, the obtained results have proved the effectiveness of supplementing conventional production logging (PLT) with reservoir-oriented techniques.
Integrating Experience and Developing Recommendations to Aid in Formation Testing Jobs Planning in Various Geological Conditions
Authors: Chashkov Anatoliy Vasilevich , Shalamov Ilya Pavlovich , Shkunov Evgeny Viktorovich , Bakustina Svetlana Viktorovna , Yarullina Alfiya Ilfatovna , Listoykin Dmitriy Aleksandrovich , Novikov Sergey Vasilevich , Charupa Mikhail Viktorovich
Published: September 2020

The objective of this work is to summarize obtained information during the well formation testing (WFT) jobs completed in open hole at the fields of PJSC NOVATEK. We also conducted analysis of formation pressure measurements, assessment of the saturating fluid type and the quality of downhole fluid samples collected at various geological and well conditions. Now PJSC NOVATEK and its subsidiaries have been actively using various types of WFT to solve a complex geological objective on the fields at exploration and development steps. Thus, an impressive array of data was formed, and detailed analysis made it possible to develop optimal success criteria and recommendations for carrying out such jobs in the wells.

We used data obtained with WFT jobs in the main productive reservoirs of the Cenomanian, Marseilian, Tanopchin and Achimov strata in the northern region of Western Siberia.

We have considered influence of various geological and technological factors on the reliability on formation pressures (FP) measurements with WFT. To assess the quality of downhole fluid analysis (DFA) we tried to compare time to reservoir fluid appearance, reservoir properties, drilling fluid type etc., in dependence of sampling tool type utilized.

Within performed interval pressure transient tests (IPTT) an analysis of the quality of the hydrodynamic parameters of the reservoirs was conducted aiding to plan cased hole well-tests.

We also considered of WFT application for representative downhole sampling to obtain information of the main PVT properties of reservoir fluids.
Experience in the Implementation and Research of Multilateral Horizontal Wells in the Vankor Cluster Field
Authors: Volkov Vladimir Alekseevich , Shirokov Andrey Sergeevich , Grandov Dmitry Vyacheslavovich , Utusikov Yaroslav Vladimirovich
Published: September 2020

The paper presents an assessment of multilateral horizontal wells performance, which is relevant for the conditions of the Vankor Cluster of fields in view of the beginning of active development phase to involve low-productive reservoirs of Nizhnekhetskaya Formation into development.

With the development of the asset reserves, a natural decrease in input productivity is observed in the zones with poorer properties. This circumstance requires the introduction of new promising technologies, such as multistage hydraulic fracturing in horizontal wells (Hz wells with MHF) and drilling multilateral horizontal wells (MHz) which have already proven themselves on the positive side under similar conditions in the fields of West and East Siberia.
Application of the Multi-Stage Hydraulic Fracturing Technology in Horizontal Wells with Large Vertical Outflow to Improve the Development Efficiency of Reservoirs with Deteriorated Filtration-Capacitance Properties at the Sakhalin Shelf Field
Authors: Prudskiy Mikhail Yurevich , Khaliulin Ruslan Rinatovich , Shakirov Roman Akhatovich
Published: September 2020

The article presents the projected results of the offshore development option in the zone of deteriorated filtration-capacitance properties. To involve additional oil reserves in the development, it is proposed to use multi-stage hydraulic fracturing technology at the projected horizontal wells. The analysis was executed using modern methods of geological, hydrodynamic and geomechanical modeling. Method of most favorable zones’ isolation for carrying out multi-stage hydraulic fracturing of formation based on maps of permeability, current formation pressure, density of residual movable oil reserves and cover power is proposed. Taking into account the selected zones and the expected direction of crack development, the trajectories of new horizontal wells with a large deviation from the vertical were optimized. Efficiency assessment was carried out by comparing the technical and economic parameters of the proposed development option (horizontal wells with multi-stage hydraulic fracturing of the formation) with the basic version (horizontal wells with traditional completion). A hydrodynamic model was used to calculate oil production levels according to options.

As a result, it was proved that the use of multi-stage hydraulic fracturing technology will involve additional oil reserves in the development and increase the efficiency of expensive offshore drilling.
Estimation and Localization of Residual Recoverable Oil Reserves by the Complex of Filtration, Optical and Field Research
Authors: Burkhanov Ramis Nurutdinovich , Lutfullin Azat Abuzarovich , Ibragimov Ildar Ilyasovich , Maksyutin Alexander Valeryevich
Published: September 2020

The structure and composition of oil reserves deteriorate in the course of a mature oil field development due to geological and technological factors. The geological factors include vertical and lateral macro-and micro-heterogeneity of the reservoirs under development. At the same time, macro-heterogeneity leads to the formation of bypassed residual oil in low- permeability and stagnant layers, zones and lenses that are not exposed to stimulation, while micro-heterogeneity contributes to the formation of residual reserves of capillary oil and oil films. Technological factors include impossibility to fully account for reservoir heterogeneity when substantiating well spacing, pressure gradient, or flooding technology. The key problem here is the lack of clear understanding of the distribution pattern, quantity and deterioration of the quality of residual oil in water-flooded reservoirs, which makes it challenging to reasonably select a technology for effective oil extraction.

Despite the improvements constantly made to the production logging, hydrodynamic and interpretive, seismic, lithofacies and other methods of exploration and residual reserves modeling, it is often impossible to obtain timely reliable information about the percentage of reserves depletion and their coverage with the development activities. This paper proposes another method — optical — that, in combination with well logging and hydrodynamic surveys as well as geological and hydrodynamic simulation, has been tested to assess the quantity and spatial pattern of residual oil reserves of the Kynovian (Do) and Pashian (D1) horizons at the experimental site of the Romashkinskoye oil field (Devonian formation). From the theoretical and methodological standpoint, this method is underlain by the results of in vitro studies of core columns and involves the selection and research of optical properties of oil wellhead samples, mathematical processing and correlation of the obtained optical and field data. The obtained estimate of residual reserves is compared with data derived from geological simulation, the most promising automated method for identifying, geometrizing and calculating residual recoverable oil reserves (RROR).

The proposed method offers such advantages as ease of use, promptness, reliability, functionality and cost-effectiveness. It uses actual data on cumulative well production and takes into account the current reservoir and fluid porosity and permeability (P&P), which provides the possibility to obtain more precise estimates of the RROR quantity and spatial pattern.
Pressure Maintains System Optimization Recommendations by Integrated Analysis of Well-Tests, Logs and Pulse-Code Interference Tests
Authors: Ganiev Bulat , Lutfullin Azat , Karimov Ildar , Muhliev Ilnur , Gulyaev Danila , Farakhova Rushana , Zinurov Linar , Mingaraev Ramil , Aslanyan Artur
Published: September 2020

In order to efficiently asses pressure support during the field development that bears a complex structure of the void space, it is extremely important to understand how existing wells affect each other, this issue was solved at one of the fields in Tatarstan through unique cross-well surveys.

The conventional way to solve the problem of assessing reservoir connectivity consists of analysing seismic surveys, analysing the tectonics and sedimentology at focus region, conducting tracer surveys, interference tests, and production analysis. However, all of aforementioned methods display substantial deficiencies, for instance: poor seismic sensitivity towards low-amplitude faults, poor degree of detail of tectonic analysis, poor tracers representatives in complex vertical and lateral reservoir heterogeneity, if most permeable thin layer lateral anisotropy differs greatly with the main layer anisotropy, huge production losses during interference test along with receiver well shut-ins, and ambiguity in the estimation of interference with the production analysis. That's why is was decided to use pressure Pulse Code Testing (PCT) (Kamal, M. M. 1983; Ahn, S. et al. 2010; Aslanyan, A. et al. 2015; Aslanyan, A. et al. 2016) that managed to overcome those problems and avoid production deferment. The values of reservoir diffusivity and transmissibility are calculated from the recorded in revisers moment of arrival and the amplitude of the pressure disturbance from rate changes in generators. Based on the registered pressure pulse amplitudes we can estimate the influence of generator monthly injection on the pressure at receivers (Myake-shev, N. 2017). The obtained injector influence on producing well is extremely low, and indicates a poor efficiency of pressure maintains system at the tested area. That implicitly indicates on unproductive injection (Zheng, S. 2010).

In addition to a subsequent production logging it was confirmed that there is in fact a presence of a significant amount of unproductive injection due to cross flow downstairs. That was reducing the efficiency of the pressure support in the study area. This placed the start to a set of extended surveys aimed at selecting of the most appropriate injection targets of the injection wells to improve the efficiency of the pressure maintains system as well as oil production increase.
Missed Net Pay Zones Mature Oilfieds Via Injection Of Expert Knowledge in Deep Learning Algorithms
Authors: Semenikhin Artyom Sergeevich , Shchepetnov Arseniy Andreevich , Reshytko Alexander Alexanderovich , Sabirov Arthur Rustamovich , Osmonalieva Oksana Taalaevna , Egorov Dmitry Vitalyevich , Belozerov Boris Vladimirovich
Published: September 2020

In this work we pursued the goal of an automate cognitive system development capable for searching missed net pay zones within wells to extend a brownfield lifecycle via the involvement of new reserves into the field development. Additional research was dedicated to studying the possibility of knowledge transfer across different fields and the construction of the ranking model allowing fast expertise conduction of proposed intervals and evaluation of the proposed method on mature assesses.

The proposed approach is based on deep learning and artificial neural networks architectures trained in a supervised mode using a provided human well logs interpretation. Our approach also utilizes transfer learning procedures in order to reuse knowledge extracted from the oilfield with sufficient data and improve the predictive qualities of the model on a target oilfield. Additionally, we proposed a ranking model that simulates expert decision-making process and evaluates oil saturation potential of proposed intervals by sorting it by a confidence level.

Developed method was evaluated at the one of Gazpromneft brownfields, located in Western Siberia, Yamalo-Nenets region. The model was trained on a data from this field and its analogues with subsequent reinterpretation of the whole well log volume. Several hundreds of new net pay intervals were proposed and post-processed by ranking model. Then the list of proposed intervals was analyzed by an expert group including number of geologists, petrophysicists and reservoir engineers. Significant part of these intervals after detailed and comprehensive evaluation were marked as missed during previous manual well log interpretation conducted by petrophysicist and taken for the following fieldwork. Produced results confirmed applicability of proposed algorithm and proved its capability for localization of previously unrecognized net pay intervals.
3D Reservoir Model History Matching Based on Machine Learning Technology
Authors: Illarionov Egor , Temirchev Pavel , Voloskov Dmitry , Gubanova Anna , Koroteev Dmitry , Simonov Maxim , Akhmetov Alexey , Margarit Andrey
Published: September 2020

In adaptation of reservoir models a direct gradient backpropagation through the forward model is often intractable or requires enormous computational costs. Thus one have to construct separate models that simulate them implicitly, e.g. via stochastic sampling or solving of adjoint systems. We demonstrate that if the forward model is a neural network, gradient backpropagation becomes naturally involved both in model training and adaptation. In our research we compare 3 adaptation strategies: variation of reservoir model variables, neural network adaptation and latent space adaptation and discuss to what extent they preserve the geological content. We exploit a real-world reservoir model to investigate the problem in practical case. The numerical experiments demonstrate that the latent space adaptation provides the most stable and accurate results.
Tool for Operational Well Stock Management and Forecasting
Authors: Sharifov Anar Rabilovich , Perets Dmitry Sergeevich , Zhdanov Ivan Aleksandrovich , Belonogov Evgenii Valerievich , Margarit Andrei Stanislavovich
Published: September 2020

The purpose of the article is describing a tool for analysis and waterflooding management of large fields with a long development history. The developed tool contains a physical and mathematical model of the reservoir, which is a self-consistent solution of the equations of material balance, filtration and PVT correlation for each waterflood cell. To verify a simplified reservoir model, it is possible to forecast using historical well control parameters with their automatic adaptation. The paper describes the main stages of user interaction with the tool and its functionality. The results of a retrospective forecast for two different development reservoirs has been presented, the lacks and conditions of the model applicability were described. Integration with the tool on the basis of optimization algorithms was made and the results of multivariate calculations for the search for a scenario for developing a large oil and gas field with the best economic effect are presented.
Thomsen Parameters Determination from Synthetic Sonic Logging Data for VTI Formation Using a Convolutional Neural Network
Authors: Bazulin Maksim , Sabitov Denis , Charara Marwan
Published: September 2020

Vertical transverse isotropic (VTI) formations are commonly encountered in sedimentary basins and they are the simplest type of anisotropic formations. However, the inversion of the sonic logging data in such formations is a challenging problem for the case of wells parallel to the axis of symmetry. Most of the conventional processing techniques use only the kinematic characteristics of the wavefield, whereas sufficient information about the anisotropic parameters is contained in the amplitudes of the signal. All the elastic parameters (formation density, compressional and shear wave velocities, Thomsen parameters) cannot be retrieved without rigorous assumptions or additional data (e.g. from deviated borehole). In the present work, we perform a sonic data inversion by using a machine learning approach, more specifically, the convolutional neural network. The main advantage of the method is that the neural network processes the full waveform seismogram taking into account simultaneously the kinematic and the amplitude part of the wavefield. For the network training, a synthetic dataset was generated using the spectral element method. The results of the work demonstrate the feasibility of the method, when a seismogram is fed to the input of the neural network and elastic parameters are given as the output.
Developing Algorithms to Analyze Data Gathered During Drilling Using Big Data Approaches – Features, Limitations, Main Rules
Authors: Zinovyev Alexey Alexeevich , Nechaev Artem Valentinovich , Ocheretyanyy Anton Nikolaevich , Volkov Dmitrii Yurievich , Petrakov Yuriy Anatolyevich , Sobolev Alexey Evgenyevich
Published: September 2020

The paper describes the main approaches used in the development of predictive analytics algorithms, both of a general nature and in the field of well drilling. When describing the algorithms used, the basic assumptions of each and the ensuing limitations of the developed model are explained. The necessity of building hybrid models, involving the full amount of information collected, including calculations carried out during the construction of the well, both from the engineering and geological sides, is shown. The paper discusses the culture of working with data in the oil and gas field in general and in particular well drilling. The current level does not allow companies to create scalable solutions of predictive analysis. As a result of the work done, the basic rules were proposed, the first step was taken towards standardizing the process of collecting and analyzing information flow arising during the construction of wells.
Streaming Machine Learning for an Oilfield Development System Selection Based on a Complex Optimality Criterion
Authors: Sun Daria Vitalievna , Okunev Maksim Vadimovich
Published: September 2020

In this paper we present the methodology to predict the value of the complex optimality criteria from the parameters of the oil field development system such as well spacing, the distortion factor, the type of well completion, the horizontal length of the end of switching time, etc. The method presented in this paper is based on the results of multivariate calculations in a hydrodynamic simulator and the use of correlation models of machine learning (ML).
New Technology for Inverse Problem Solving of Digital Core Model Construction Using Stochastic Modeling and Particle Swarm Optimization
Authors: Markov Pavel
Published: September 2020

The goal of this article is to present a new technology of inverse problem solving for constructions from scratch or parameter clarifications of pore-scale models and parameters of simulated multiphase flow processes, particularly associated with EOR methods. The solution of these problems is relevant because of the increasing use of digital core analysis and pore-scale modeling and the presence of problems associated with determining of missing model and flow processes parameters hindering the further development of these methods.

The technology for solving inverse problems for digital core models contains: the developed method for stochastic generations of pore network models, the simulation method for one- and two-phase flow, the suggested objective functional, and the particle swarm optimization method. The developed model construction method is based on the stochastic generations of all parameters for pores and capillaries according to their distributions: radii and shape factors of pores and capillaries, pore coordination numbers, capillary lengths. The suggested objective functional estimates deviations of calculated parameters from known reservoir parameters for core samples: porosity, permeability, capillary pressure, relative permeability.

The technology solved the following problems, what have been shown on the basis of three practical cases: assessments of local distributions of parameters (e.g., contact angles) what is difficult to estimate experimentally; submicron pore reconstructions which are "not visible" using μCT; model constructions corresponding to the experimental reservoir parameters; models (millimeters) rescaling to sample sizes used for flow experiments (centimeters); digital core model estimations which are typical on reservoir scales for parameter calculations, e.g., for reservoir simulation models.

The developed technology for digital core model constructions based on stochastic modeling was first used for three oil and gas fields. The technology allows to solve a part of problems that hinders wider applications of digital core analysis and pore-scale modeling, particularly in EOR efficiency estimations. One of the problems is the transfer of results of the millimeter sample scale to the centimeter sample scale and, further, to scales of reservoirs where the solution is to build stochastic models.
Geosteering Based on Integration of LWD and Surface Logging Using Machine Learning
Authors: Galkina Alena Vladimirovna , Yalaev Tagir Rustamovich , Lisitsyna Marina Yurievna , Rakhimov Timur Rinatovich
Published: September 2020

This study presents an approach based on machine learning to predict the lithology at the bit while drilling. This is necessary for (near) real-time adjustments of well path while providing reservoir characterization (reservoir rock, non-reservoir rock and tight rocks). The approach is based on an ensemble of decision trees and gradient boosting. Work on this project included analysis and preprocessing of the data, selection of features for training, creation of additional features to improve the quality of the model, comparison of machine learning algorithms to identify the most effective within the task, optimization of the hyperparameters. After that, the final model is built on a training dataset with desired outputs obtained from LWD formation evaluation and the quality of the algorithm is evaluated on a test dataset with the selected metrics.

The computer program developed on the proposed approach receives drilling data as input and provides a reservoir characterization. High quality of the model is necessary for successful geosteering of horizontal wells due to the rapid detection of lithology changes in the reservoir and increasing the efficiency of well drilling by minimizing penetration through the non-reservoir rocks, which can further increase oil production. The proposed approach provides an accuracy of 80-90% for a number of oil fields.
Building a Unified Compositional Model
Authors: Bogachev Kirill , Zhukov Sergey , Milyutin Sergey
Published: September 2020

The construction of unified compositional model is important for modeling of production surface network. The produced streams are described by different multicomponent PVT models, while total production calculation requires a single consistent PVT system. The method for constructing a compositional model which is optimal in terms of components number is proposed.

As a first step, all components from all initial mixtures are split by molecular weight into two groups: light and heavy, which are considered separately from that point on. The basis component set for the light group is constructed from the pure hydrocarbons and inorganic substances. Then the components from the light group are expanded over it using the method of numerical minimization. The objective function used is the sum of the moduli of the relative differences of corresponding parameters of initial components and their decompositions. The parameters considered are critical properties (pressure, temperature, volume) and the acentric factor. The condition of equality of molecular weights is enforced, to ensure the conservation of material balance during decomposition of the initial components. Two methods are proposed for the characterization of heavy components: either proceed the same way as it is done for the light group, with the construction of a corresponding basis, or use fractionation by the number of carbon atoms. All properties of the components of the final set are fully known after the above algorithm has been applied. Each component in the initial mixtures is decomposed using the resulting set of components with uniquely defined coefficients.

The proposed method is successfully used to construct a unified compositional model for production surface networks. The sources (pipelines or wells) with different PVT models are connected in the single production network computed by resulting compositional PVT properties.
Coupled Static and Dynamic High Resolution Modelling on High Performance Computer Clusters
Authors: Absalyamov Artem Vadimovich , Bogachev Kirill Yurievich , Glazkova Ekaterina Alekseevna , Kostin Georgii Aleksandrovich , Telishev Alexey Sergeevich , Tregub Semen Leonidovich , Shimonin Egor Yurievich
Published: September 2020

Significant acceleration of the calculations used to create three-dimensional geological and hydrodynamic models is discussed. Detailed 3D models of large and giant reservoirs requires significant computing power for their creation. All available seismic, geological and hydrodynamic data on the oil and gas field, which must be taken into account in a detailed model, require the construction of a grid from several hundred million to several billion blocks. A method proposed for integrated static and dynamic model calculation allows the most efficient usage of a parallel computing cluster system capabilities.
Development of Acidizing Simulator for Sandstone Reservoirs
Authors: Blonsky Artem Vadimovich , Mitrushkin Dmitrii Aleksandrovich , Kazakov Artem Vyacheslavovich , Filippov Danil Denisovich , Mokropulo Yury Ivanovich , Bazanov Ilya Evgenevich , Shcherbakov Georgii Yurievich , Melnikov Alexander Viktorovich , Roshchektaev Aleksei Petrovich , Maltcev Andrei Andreevich , Morozov Maxim Aleksandrovich
Published: September 2020

In this paper it is described the approach of constructing the design of acid treatment and the tools of the software designed to solve this problem. The developed simulator includes a hierarchy of calculation modules that differ in the degree of detail of the physical effects. In addition, a number of engineering modules was developed as a part of the simulator: well data preprocessing module, history-matching module, optimization module.

The mathematical models in the simulator take into account the multicomponent composition of the liquid, an arbitrary number of minerals in the solid phase, and an arbitrary number of kinetically controlled heterogeneous and homogeneous chemical reactions. Moreover, the models take into account the non-Newtonian rheology of diverters and the thermal effects during chemical reactions. The geometry of the well and hydraulic fractures can be explicitly resolved on 3D Voronoi grid in the framework of developed approach.

The developed algorithms were tested by real data. It is demonstrated that precipitation resulting from secondary and tertiary reactions can have a determining effect on the result of acid treatment. The article presents the results of simulation acid treatment in a vertical well with a colmated hydraulic fracture. It is shown that acid treatment led to complete restoration of the fracture conductivity. The results of the two acid treatments analysis are also presented. When analyzing the first work it was possible to determine the reasons for the unsuccessful treatment by the adaptation model to the production data and to select an acid composition that provided maximum efficiency.

When analyzing the second treatment for the well, an analog was found on which acid treatment was performed. The model parameters were adapted to the results of acidizing for the analog, and the parameters obtained as a result of the adaptation were used to simulate treatment at the original well, which led to the agreement of the simulation results with the real data. Then, it was shown under the result of design optimization that more intensive acid treatment should have been performed on the original well.
Assessment of Non-Equilibrium Phase Behavior Model Parameters for Oil and Gas-Condensate Systems by Laboratory and Field Studies
Authors: Indrupskiy Ilya Mikhailovich , Danko Mikhail Yurievich , Tsagan-Mandzhiev Timur Nikolaevich , Aglyamova Ayguzel Ilshatovna
Published: September 2020

Non-equilibrium phase behavior of hydrocarbons has a great influence on the development of gas condensate and oil and gas condensate deposits, as well as oil deposits after evolution of dissolved gas. The key parameter of mathematical models that take into account non-equilibrium phase behavior is the characteristic relaxation time. The paper presents examples of assessing its value according to the results of laboratory experiments and well tests, which also allow verifying the mathematical model and obtaining input data for the production forecast taking into account non-equilibrium processes.

A model of non-equilibrium phase behavior in a compositional formulation, based on relaxation of the chemical potentials difference, was verified on the data of a laboratory experiment in a calorimeter cell. The numerical algorithm for calculating the dynamics of phase fractions and compositions in a non-equilibrium process was modified to take into account the isochoric condition, which made it possible to directly compare the simulation results to the real experiment. A good match of the experimental pressure-temperature hysteresis curves was obtained without additional adjustment of the characteristic relaxation time as compared with the estimate obtained from processing the measured pressure relaxation curve. Thus, the adequacy of the mathematical model and the possibility of evaluating its parameters directly from the experimental measurements were confirmed.

An example of assessing the characteristic relaxation time from well test data is presented for the pressure buildup (PBU) curve recorded under the conditions of gas dissolution in oil. A sector blackoil-type model was used for the well drainage area. For matching the PBU data, various modeling methods for non-instant gas dissolution were considered, including a model based on relaxation of solution gas-oil ratio (sGOR). The results of simulations with the sector model showed that the traditional options for limiting the sGOR increasing rate do not allow adequate matching of the PBU curve under conditions of gas dissolution. For the model that takes into account the sGOR relaxation, an in-situ estimate of the characteristic relaxation time was obtained which provided a fine match of the PBU data. As expected from theoretical concepts, the characteristic relaxation time for the in-situ process has a much larger order of magnitude than for the laboratory experiments on centimeter-sized cells.

The results of the study show the adequacy of relaxation models for non-equilibrium phase behavior in compositional and black-oil formulations for describing real processes and demonstrate the possibility to estimate the characteristic relaxation time from laboratory experiments and well tests, taking into account its dependence on the process scale.
Assisted Creation and Usage of Material Balance Models for Production Forecasting as a Part of Integrated Field Management
Authors: Bakhty Nikolay , Demin Albert , Tupitsin Maksim
Published: September 2020

For decades, computer simulation has been an inevitable part of hydrocarbon reservoir development. 3D reservoir models of productive reservoirs and gathering system pipeline models exist for almost all operated fields.

The recent concept of digital oilfield relies much upon performing computer simulation in order to automate the development process. Operational field development management is one of the processes that can be automated within this concept. However, conventional computer simulation techniques based on the above-mentioned 3D reservoir models are ill-suited for automation of operational development management. This can be attributed to the fact that creating, history matching, updating, and calculations of such integrated models are very time-consuming.

Integrated models based on simplified models of productive reservoirs can be regarded as a basic means of operational field management. A case in point are models built on material balance equations. However, this approach has its drawbacks. The main problem lies in having to do double the work. One has to have two models for each productive reservoir: one model for operational development management (simplified model) and the other for conventional modeling (3D reservoir model). This paper considers solving the stated problem by transforming a conventional 3D reservoir model of a productive reservoir into a material balance model and provides comparative analysis of both modeling approaches.
West Siberia Jurassic Sediments Rock Typing and Digital Models Creating for Geological Model Refining
Authors: Blotskaya Arina Igorevna , Sardarov German Serderovich
Published: September 2020

The developed transition saturation zone and the presence of free water above the accepted level of OWC, which is usually characterized by undersaturated reservoirs, greatly complicates the development of deposits and requires updating the geological model based not only on the standard partition of the lithotype section according to well log data, but also involving the results of core material research.

The aim of this work is to interpret well logging data using rock typing in the conditions of a developed transitional saturation zone and the presence of free water above the accepted OWC level. The work was carried out in one of the Western Siberia oil fields in the Upper-Middle Jurassic terrigenous sediments. The work is based on a comparison of interpretation algorithms based on a standard approach and on the basis of building flexible interpretation algorithms and creating an interactive system of petrophysical modeling. In addition, intermediate conclusions will be shown, such as the use of a calibrated fluid model based on special core studies data for standard log data for drilling horizontal and pilot shafts. Comparison of the core data results interpretation and the petrophysical model constructed by the volumetric method.
Reservoir Flow Connectivity Estimation and Its Using in Geomodeling: Tomsk Area Case Study
Authors: Popov Victor Lvovich , Zakrevskiy Konstantin Evgenyevich , Podnebesnykh Alexander Vladimirovich , Krasnoshchekova Lubov Afanasyevna
Published: September 2020

The method for quantitative prediction of the reservoir connectivity is given for one of the oilfields of Tomsk area. The studied upper Jurassic reservoir was formed in coastal environment and penetrated with a small number of wells.

The volume of recoverable oil is depend on chosen method for lithology or N/G modelling. The calculations, which were done on geology and simulation models, showed that recoveryg factor changes can reach 35% and related to reservoir connectivity. The Tomsk area reservoirs geomodels, which have production history and total oil production, is higher than 60% of recoverable oil reserves, were studied in order to develop method to predict connectivity coefficient of reservoirs. The relations between reservoir heterogeneity and sedimentology features and log data were found. It allowed making prediction for connectivity coefficient value for case study reservoir.

In addition, production data of two wells of case study reservoir were considered. Analysis of wells from other Tomsk reservoirs with the same completion type shows that connectivity value is related with well production rate drop factor. This regression allows predicting desired connectivity coefficient for case study reservoir in order to provide appropriate heterogeneity to match model with production history data.

Finally, the modeling method with continuous N/G property was chosen for geomodel. This is the only method, which allows achieving heterogeneity level that corresponds to sedimentary environments, log features and production history data. As a result, more accurate geomodel was created which has lower uncertainty lever in prediction of reservoir properties in non-drilled part of the reservoir.
Completion Strategy Alteration on an Overpressured Field Based on Geomechanical Modeling and a Geomechanics Based Fracture Design
Authors: Korelskiy Evgeny Pavlovich , Ochirov Gleb Olegovich , Kosareva Marina Sergeevna , Chernyak Vyacheslav Sergeevich , Peshkov Igor Viktorinovich , Kosarev Taras Igorevich , Sadykov Lenar Alfatovich
Published: September 2020

Hydraulic fracturing as an approach of oil and gas recovery intensification in clastic formations has long been well known and recognized from technological and economical sides. However, in spite of the obvious advantages of hydraulic fracturing procedure, the method has its drawbacks which decrease the final oil and gas productions.

One of these disadvantages is a fracture breakthrough into the adjacent layers with following water cut increase and reduction of cumulative oil and gas production and production rates. Bearing in mind the geological structure of the explorational targets in this paper, the problem becomes more relevant. The presence of an abnormally high formation pressure in the reservoir, which exceeds the surrounding shale's pressure, and the shale barrier, which does not provide a sufficient stress barrier, promotes possible breaks of fractures into the overlying water-bearing zone.

Owing to the simulation of hydraulic fractures based on the geomechanical model, it was possible to implement the hydraulic fracturing strategy and planning, taking into account the understanding of the geomechanical parameters and the stress-strain state of the medium, in which it was possible to avoid breakthroughs of hydraulic fractures into the overlying water-saturated formation. In addition, it is shown that outwardly similar development objects may require radically different approaches to well completion.
Improved Well Construction Enabled by Pore Pressure Prediction While Drilling in Zapadno-Yurkharovskoe Field
Authors: Chettykbayeva Kamilla Nusupbekovna , Grigoriev Maxim Sergeyevich , Shakunov Alexander Anatolievich , Korotkov Stanislav Aleksandrovich , Kovalevskiy Andrey Valer'evich , Bybin Pyotr Valer'evich , Nikitin Ivan Andreevich , Zinovyev Alexey Alexeevich
Published: September 2020

Jurassic deposits of Zapadno-Yurkharovskoe oilfield include laminated sequences of sandstones and shales and characterized by overpressure (up to 830 atm at 4000m depth). The challenging clinoform geology of Achimov layers above the target formation presets the environment where pore pressure can differ significantly even in one statigraphic unit at the same depth. It is of paramount importance to determine the setting depths of production casing and that of the first liner of horizontal wells with respect to quantitative description of pore pressure increase with depth. According to the drilling history in the area, overdeepening the production section can lead to gas kick and the need of weighting up the mud, which can result in extreme losses while cementing the casing; stopping the drilling early can increase the risk of incompatible conditions in the first liner section.

The objective of this study was to assess the pore pressure in real time to determine the best depth of setting the casing in the conditions of high uncertainty, since the field is not yet explored thoroughly neither by 3D seismic nor by drilling.

The drilling analysis and geomechanical modeling revealed that the safe mud window of horizontal wells is extremely narrow: the drilling limits between pore pressure-collapse gradient and mud losses gradient in some intervals do not exceed 0.08-0.10 specific gravity. The established criteria for setting the production casing depth is to stop the drilling when the pore pressure reaches 1.35 g/cc of mud weight equivalent, the next section is to case the shale sequence with the increase of pore pressure from 1.35 to 2.10-2.12 g/cc of mud equivalent, lastly, the production liner cases the gas condensate bearing reservoirs drilled with the heaviest muds of up to 2.15-2.18 g/cc to offset the pore pressure and stabilize the overlying Abalak deposits, which are prone to breakout.

The best drilling decisions are to made in the conditions of extremely complex geology, uneven pore pressure distribution and in the absence of seismic inversion results. The established criteria for well design and the techniques of pore pressure assessment have already proved positive for the well #5. These experience and methodologies can be interesting and useful for other projects managing the overpressured low permeability reservoirs in Western Siberia as well.
Reduction of Accidents During Mine Construction with Geomechanical Modeling
Authors: Melikov Ruslan Fuadovich , Korelskiy Evgeniy Pavlovich , Krasnikov Artem Alexandrovich , Volkov Dmitry Yurievich , Petrakov Yuriy Anatolievich , Sobolev Alexey Evgenievich
Published: September 2020

The uniqueness of this work lies in the application of the approaches and experience of geomechanical modeling accumulated in the oil and gas industry to solve the problems of building mines, which reduced accident rate and, as a result, minimized the cost of eliminating the consequences of complications, as well as accelerating the commissioning of the mine.

The peculiarity of the simulation was to take into account the temperature of the rock mass and freezing wells, which affected the stress state, safe drilling window and cementing parameters during the construction of additional freezing loop wells, as well as during the strengthening of the rock mass.

Based on the results of the well logging, seismic surveys and geomechanical modeling, the stress state of the decompression zone is estimated and the parameters of the cement slurry injection when attaching wells and strengthening the rock mass to isolate the shaft from aquifers are recommended.
Usage of Imitational Geological-Petrophysical Models to Reduce Drilling Risks for Offshore Reservoirs Exploration
Authors: Dubinya Nikita Vladislavovich , Vershinin Anatoly Viktorovich , Pirogova Anastasia Sergeevna , Tikhotsky Sergey Andreevich
Published: September 2020

The paper presents the results of numerical modeling of the stress fields acting in hydrocarbon reservoirs located at Russian continental shelf. The problem of prediction of the zones with the higher drilling risks based on the detailed analysis of seismic data is considered. We focus on the problem of the degree of the influence some factors have on zones of potential drilling risks. These factors include: dependencies between static and dynamic elastic moduli and strength properties; parameters standing for pore pressure distribution and tectonic stresses. Imitational geological-petrophysical models are used as a tool for such analysis. Those are models of mechanical properties, complemented with pore pressure fields and tectonic forces. The dynamic characteristics of seismic data (amplitudes and frequencies) obtained from high quality seismic data interpretation act as a basis for construction of imitational models. The paper describes the creation of such models, the main parameters used for variation of considered factors are highlighted, imitational models are created based on seismic data obtained at Laptev sea shelf. Numerical geomechanical modeling is carried out for these models, quantitative drilling risks analysis is performed with prediction of the zones of potential drilling risks. The problem of possible potential drilling zones prediction based on seismic data interpretation results systematic analysis is discussed.
3D Digital Mineral-Mechanical Modeling of Complex Reservoirs Rocks for Understanding Fracture Propagation at Microscale
Authors: Nachev Victor Andreevich , Kazak Andrey Vladimirovich , Turuntaev Sergey Borisovich
Published: September 2020

Increasing the efficiency of hydraulic fracturing operations in complex reservoir rocks requires creating an extensive network of fractures to improve the drainage zone of the field development. The research aims at understanding the stress-strain conditions required the initiation and propagation of mechanical fractures during well-bore zone stimulation in tight reservoir rocks. We investigate at the microscale, taking into account the mineral heterogeneity, matrix structure, elastic-plastic properties of minerals, and their intergranular contacts. The research relies on experimental data performed on modern laboratory equipment and the use of applied simulation software. We propose an integral physico-mathematical model of the propagation of three-dimensional fractures at the microscale. The model accounts for the granular composition and structure of the sample, its elastic-plastic properties, and conditions at the intergranular contacts. We discuss a set of experimental methods and research necessary for numerical simulation of fracture propagation at the microscale, taking into account the heterogeneous mineral composition of the reservoir rock. The paper shows the results of mathematical elastic-plastic modeling of stress-strain state and fracture propagation in two-dimensional and three-dimensional models with the complex geometry of contacts between minerals. Finally, we make conclusions about the possibility of using the results obtained in optimizing the parameters of hydraulic fracturing.