The paper analyzes main problems of Rock-Physics (or petroelastic) modeling of fractured carbonate rocks. These problems include the choice of method of effective medium theory (Rock Physics) for connecting the parameters of the mathematical model of effective elastic properties of a reservoir rock with the elastic wave velocities obtained in experiment. It is shown that even in the case of a simple model of a fractured reservoir rock, the difference in the velocities of elastic waves obtained by different methods can reach 40 %. Another problem of Rock-Physics modeling is a construction of a model medium that adequately reflects characteristics of the internal structure of rock in the scale under consideration. In this regard, attention is paid to carbonate reservoirs of a complex structure, in which the neglect of specific features in a distribution of isometric porosity leads to a change in the velocity of elastic waves, which can be mistakenly attributed to the influence of fracturing. These types of reservoirs include oolitic limestones and rocks containing cavities. A problem exists of the correspondence of scales on which the Rock-Physics model is constructed, and its elastic properties are measured. It is shown that the difference of impedances (both acoustic and shear) obtained at the same depth but at different scales (logging and seismic), can reach 20 % и even more. An important problem of petroelastic modeling of fractured reservoirs is the allowance for the anisotropy of both the host matrix and the resulting elastic properties. The problem of differences in petrophysical dependencies (e.g., porosity-velocity) obtained on cores and from logs is analyzed. In this relation a carbonate reservoir of the Yurubcheno-Tokhoma zone is analyzed whose internal structure is rather complex. Particular attention is paid to the problem of detecting and characterizing fluid-conducting cracks on a seismic scale. To solve this problem, an approach is presented that relies on the results of geomechanical and Rock-Physics modeling. This approach makes it possible not only to reveal fluid-conducting fracture systems, but also to characterize them quantitatively in terms of orientation, volume concentration, relative opening, and degree of connectivity.

In unconventional reservoirs with oil deposits formed under syngenetic conditions during the generation of hydrocarbons from kerogen, the stratum of the reservoir rocks was reformed, leading to the formation of various forms of empty space, filled with a liquid phase. An example of such unconventional reservoir is the stratum of rocks of the Bazhenov formation, which occurs over a large area in Western Siberia. An important feature of its structure, which does not allow it to be actively developed for 50 years, is the lack of reliable knowledge about the structural and textural features of the reservoir structure, types of empty space and its location in the reservoir. Therefore, there are still no unambiguous ideas about the form of deposits, about highly productive zones in the reservoir, about recoverable reserves, about the technology which is necessary to involve the reserves into the development. Since the development of oil reservoirs confined to the deposits of the Bazhenov formation is carried out under an elastic regime, hydrodynamic studies of reservoirs and wells and monitoring of the energy conditions of the reservoir are very informative means to obtain information about the reservoir. These studies allow us to investigate the characteristics of filtration in the reservoir rock and, in particular, to estimate the volumes of the fluid involved into filtration. For deposits of the Bazhenov formation, which do not contain water and are developed under the elastic regime, such information will be very valuable. Diagnostics of pressure build-up curves recorded in the wells completed in Bazhenov deposits of a number of oil fields in Western Siberia indicates that the reservoir is a layer of dual permeability. Such a reservoir model is diagnosed if the reservoir consists of two media with drastically different permeability. During the production of a well, which is completed in two differently permeable but not isolated from each other formations, the most active production takes place from a more permeable formation, which leads to an advance pressure drop in this formation. A differential pressure is formed between the layers, resulting in a flow of fluid from the low-permeable formation to the high-permeable one. Thus, the reservoir of the Bazhenov formation behaves in the development process as a reservoir consisting of two layers with different permeability and with different current reservoir pressures.

The article is devoted to the problem of modeling the fractures emerging in carbonate rocks in vicinity of amajor fault. The influence of the fault on the main tendencies in preferable spatial orientation and distribution of natural fractures is considered. The possibility of distinguishing hydraulically conductive fractures among all the variety of fractures is particularly studied. Such a distinction is carried out based on the hypothesis of a relationship between hydraulically conductive and critically stressed natural fractures, used in geomechanical studies. An algorithm for using the results of three-dimensional geomechanical modeling may be used for determining the relative amount of hydraulically conductive fractures and their preferable spatial orientation is presented in the paper. According to this algorithm, the stress state parameters are directly used to calculate the possible values of azimuthal and dip angles of fractures, which are hydraulically conductive under the current stress state. The effectiveness of the suggested algorithm is demonstrated for an array of synthetic models of reservoirs with a major fault in presence. The effect of the fault’s spatial orientation and geodynamic type on the tendencies of changes in preferable spatial orientation and distribution of hydraulically conductive fractures while approaching the fault is particularly studied. It is shown, that as long as distance to the fault decreases, the relative amount of hydraulically conductive fractures increases, while their preferable spatial orientation appears to be closely related to fault’s spatial orientation with respect to the directions of principal tectonic stresses. It is also shown that faults of varied type have different effects on tendencies in spatial orientations and distribution of hydraulically conductive fractures. The obtained results appear to be in a good agreement with the results of analogous studies carried out for one Russian oil field. The proposed algorithm of using the results of geomechanical modeling for constructing a fracture model with a possibility of distinguishing hydraulically conductive fractures broadens the possibilities of geomechanics for increasing the efficiency of fractured reservoirs’ development. The found tendencies of fracture zones’ dynamics make it possible to increase the accuracy of forecasting the preferable filtration directions, increasing the quality of hydrodynamic model.

The article highlights the problem of oil bearing of the Domanic Formation within the territory of the Republic of Tatarstan. The rocks of the Domanic facies should be considered as accumulation or accumulation-generation system, oil deposits of which were formed due to oil systems generated in other sources. New methods of search are needed that allow us quickly asses the content of migratory hydrocarbons and syngenetic organic matter. An analysis of the spatial distribution of migratory hydrocarbons will allow localizing oil migration channels.

Improving the profitability of oil field development and optimization of all business processes is the urgent task,
facing the entire oil and gas industry of Russia. Trends towards digitalization of the oil industry have predetermined
the creation of a computer algorithm for the selection of candidate wells for water injection profile leveling, capable
of automating most of the routine manual work and thereby eliminating the possibility of errors.
The algorithm developed and implemented in the work allowed to achieve the following results. The most part
of the process of forming programs for water injection profile leveling is automated, the risk of emergence of errors
is excluded. The algorithm of selection of candidate wells for water injection profile leveling has been fully updated.
Productivity of the process of selection of candidate wells increased by 47% compared to manual analytical methods.
It is possible to make timely adjustments to the programme of activities taking into account technical and
technological limitations. Stability of the technological efficiency forecast increased. Availability of work with any
size of the basic fund of wells of the oil field is reached.

Reducing CPU simulation time is essential for simulation of huge reservoirs and multivariant calculations. One
of the industry’s approaches is ‘coarsening’. Due to geometric constraints of enlarged regular cells, this approach
does not allow generating an optimal cells size mesh.
In this paper we propose an “Advanced Coarsening” approach, which is based on the available dynamic
model and allows building a reduced size complex grid with irregular enlarged cells and speeding up the calculations.
For this purpose, an auxiliary smoothed triangulation mesh is constructed with refined (near wells, faults) and
coarsened (within aquifer) cells. The enlarged cells are assigned mesh nodes by an upgridding procedure. The
grid properties are to be upscalled accordingly. The connection transmissibility factors, connection coefficients of
the well productivity and the aquifers require special calculations.
This algorithm has been successfully implemented as a feature for in-house reservoir simulator designed for both
Corner Point and Irregular grids. Numerical tests were carried out on several models of oil and gas reservoirs with
different dimensions and phase state. The test showed good solution stability and convergence with results received
on the initial regular grid.
This approach can be used for large model simulations and multivariate calculations which arise in history matching
procedures, when the matching error (discrepancy of actual and calculated data) is higher than the solution
discretization error.

This paper is devoted to flow behavior prediction in carbonate reservoirs with complex tectonic disturbances.
The special technique of fluid flow numerical simulation longwise and crosswise of highly conductive faults was
developed. The conventional fault gridding method, that was used herein, describes faults by using of the cornerpoint
geometry and a set of non-neighbor connections (NNC). The flow modeling along the faults was based on
numerical simulation of fluid physics corresponding to flux equations in the reservoir.
Considering the irregular faults allocation, the numerical algorithm for solving the fluid equations matrix was
optimized. Due to a substantial increase in the number of NNC flows, introducing off-band elements into the matrix
equations, numerical convergence problems arise and simulation run time increases, therefore additional techniques
and algorithms for solving irregular matrixes are proposed. To preserve the efficiency of the conventional numerical
algorithm under the conditions of NNC and high flux rates, the faults system is excluded from the regular
grid into the selective modeling object, which is be successfully solved within fully implicit simulator by preconditioned
iterative methods.
The efficiency of the technique implementation is presented on a full-scale Black Oil model of one of the Iraqi
fields. The advantages of proposed approach are shown for improvement of history matching procedure and forecast
production in a case study of the carbonate oil field with an intensive system of faults that divided the reservoir
into many semi-isolated areas.
The proposed approach of targeted dynamic modeling of highly conductive faults is a very promising in order
to improve the simulation of hydrocarbon recovery mechanism in complex faulted reservoirs.

The short overview of the mathematical models used in commercial simulators of hydraulic fracturing is provided in work. At the heart of considered mathematical model the PKN statement describing single vertical crack lies. Process of forming of crack of hydraulic fracturing at injection in well of viscous liquid with impurity of particles is shown. The model of development of crack taking into account fluid losses on leakage in porous medium and falling of suspended particles by gravity is offered. The detailed analysis of growth of the deposit caused by fluid seepage of hydraulic fracturing in porous medium is carried out. It is shown that availability of particles significantly influences process of disclosure of crack. Crack growth in the presence of particles is limited, its final shape depends on blend composition and way of downloading — inlet pressure, the volume maintenance of particles, bank volume (pure liquid of hydraulic fracturing without impurity). All these factors are considered in the offered model. The solution of task on calculation of parameters of vertical crack of hydraulic fracturing for real-life well is described. Comparison with results of the calculations received on foreign analog is made. Results of calculations allow to characterize residual form of crack or to pick up technology parameters for achievement of desirable results at formation fracture.

One of the relevant problems in hydrocarbon production is drilling waste generation. A temporary sludge tank and/or waste pit arrangement is provided for drilling waste accumulation and/or disposal within a well pad. It is generally known that according to the Control and Supervision Service for Environmental Protection, Wildlife Resources and Forestry Affairs of the Khanty-Mansiysk Autonomous District-Yugra (KhMAD-Yugra), 507 waste pits (308.6 ha) were surveyed in the KhMAD-Yugra over 2015, among which 481 areas (284.3 ha – 95 %) were recognized as statutorily compliant. In 2014, a commission of the Yugra Service for Supervision of Natural Resource Usage surveyed 168 recultivated areas earlier occupied by waste pits, among which 148 (88 %) were recognized as statutorily compliant. Thus, a timely return of disturbed and reclaimed soils earlier occupied by waste pits to the forestry fund lands in the KhMAD-Yugra territory is a vital task for all gas producers. 

The purpose of work is a comprehensive appraisal of the state of vegetation and topsoil formed in the territory of recultivated waste pits in the license areas of LUKOIL-West Siberia LLC. 

The main objectives of appraisal of the vegetation and topsoil reclamation state are: 
– studying of the chemical composition of drilling cuttings in waste pits recultivated more than 20 years ago; 
– appraisal of the vegetation reclamation level in the disturbed territory (projective cover of soils); 
– description of the vegetation species diversity with growing of dominating species; 
– development of proposals towards the measures for recultivation of waste pits. 

From 2015 to 2016, employees of the V.V. Dokuchaev Soil Science Institute performed field, cameral and laboratory works to survey disturbed areas at the locations of waste pits (hereinafter—WP) in the license areas of LUKOIL-West Siberia LLC. 

The waste pits to be analyzed were recultivated in the period from 1989 to 1992. Burial of wastes was accepted as the method for drilling waste management. 

Geochemical criteria such as chemical pollution by heavy metals, acidity, agrochemical characteristic of soils under study, content of oil products as well as geobotanical survey on anthropogenic sites were used to appraise the state of soils. 

Based on the results of conducted analysis, the following conclusions can be made.Drilling cuttings without additional treatment (sanding, sorbents, aluminosilicates) cannot serve as soil-forming material and be suitable for reclamation of disturbed lands.Integrated chemical analysis of drilling cuttings is a necessary stage of works involving drilling waste management.The amount of reagents required for drilling waste disposal should be determined in accordance with the outcomes of integrated chemical analysis. The most accurate and correct selection ensures minimization of the effects of wastes on environment and favors reclamation of disturbed lands at an accelerated pace.

One of actual problems at operation of horizontal wells is selection of technology for bottom-hole zone treatment in the conditions of permeability heterogeneity. The article discusses problems of acid treatments in horizontal wells at the fields of LUKOIL-West Siberia LLC. The purpose of work is the assessment of efficiency of acid treatments in horizontal wells and search of technologies for the selective processing of bottom-hole zone. The horizontal wells of AV productive formation were studied. These wells account for the bulk of the treatments. The analysis of efficiency of processing of bottom-hole zone of formation in horizontal wells for 2015-2017 on Ltd. «LUKOIL-West Siberia» fields is carried out; the low performance of processing is revealed. The possible reasons of low effect are that the hydraulic formation fracture in considered wells were carried out «blindly» without multistage hydraulic fracturing configurations owing to what the assumption of influence of availability of high-permeability cracks on efficiency of «blind» acid treatments have been made. We carried out an efficiency analysis in section of wells in which the hydraulic formation fracture, and in wells in which hydraulic fracturing was not carried out before processing of bottom-hole zone. This assumption indirectly was confirmed by higher performance of acid treatments in wells with no cracks. It is noted the absence of technologies for effective selective acid treatments in horizontal wells. Directions of search for technologies of acid treatments in horizontal wells are offered. The technology of acid treatment of bottom-hole zone with preliminary downloading flow diverting composition for isolation of high-permeability cracks is proposd.

Currently, the Orenburg region is actively working on the search and development of deposits in reef sediments. In the South of the Orenburg region there are about 20 open deposits with confirmed reef nature. These reservoirs are characterized by a complex structure, facies heterogeneity, a variety of cracks and pores. 

The analysis of the properties of reservoir rocks and fluids saturating them in order to assess their compliance with the parameters of objects whose reserves should be classified as hard-to-recover. Although reef deposits are traditional hydrocarbon reservoirs, the strata have degraded geological and commercial characteristics. Void space in reef reservoirs of complex structure: cracks occur in all facies of the reef core, and their number increases from top to bottom. This feature negatively affects the performance of the development of deposits. 

The timely implementation of effective development systems at the reef deposits of the Orenburg region will increase the oil recovery factor, ensure the growth of geological oil reserves and extend the life of deposits.

The paper highlights the results of a core sample taken from the upper part of the granite massif. In the sedimentary cover – basement contact zone, the rocks of the massif are intensively tectonized and represented by apogranite tectoniteswith oil saturation. Complex and multilevel study allowed to visualize the section of the object and the boundaries of the productive zone, describe the nature of rocks in the tectonization zone and their structural- material transformation into a reservoir. Unambiguous HC-origin was detected in grains of alkali-feldspars in the transition zone granit – tectonogranite. The main capacitive volume is contained in grains of modified feldspars of apogranitic tectonites. The degree of oil saturation is directly related to the degree of dynamometamorphism. Initial tectonization of granites gives rise to hydrocarbons, the next generates, and the final promotes migration. The study confirmed the authors’ assumption about the origin of HC in the process of shear and stress metamorphism. The studied object is an example of a mineral oil birthplace.

The direction of sawing plays a special role in the informative value of lithological study of core. According to the rules prescribed in the Surgutneftegas’s guidance, longitudinal sawing in the standard order is carried out in one direction of the joined core, the plane of the saw cut is oriented orthogonally to the direction of the main texture (macrostructure) elements. Direction changes are allowed in non-standard situations, for example when it is difficult to choose it, or when you need to saw in different directions. The sawing process was given attention in many papers written by the team of the research laboratory of lithology. This paper provides examples when correct core sawing has significantly expanded field of geological knowledge of the subsoil. Several objects of preJurassic complex core study are considered as examples. Examples are given to show «manifestation» of new important data obtained by meaningful sawing of core from different objects of research. The role of sawing direction is reflected in photos, scans and micro images, in the core description, in schematic reconstructions, in the assessment of the texture character of rocks at the mega-level.

Qualitative and detailed geological model allows to increase reliability and accuracy of development indicators calculations, and at the same time to determine fully and reliably the shortcomings of the development system, to make reasonable decisions on its improvement. The following goal has been set as part of geological monitoring: to improve the exploration and operating drilling efficiency. The main objectives of the study were interpretation of new wells logging data based on existing petrophysical models; building or updating digital three-dimensional geological models of deposits; clarifying the conception of objects geological structure according to the results of new wells drilling, seismic and other studies; geological risk assessment. In this study, as a part of an integrated approach, on the basis of exploration and production drilling, as well as seismic exploration data, geological model monitoring of mineral resources user fields is presented. By the example of deposits, located in Samara and Volgograd regions, as well as in the Republic of Tatarstan, it is shown the effectiveness of this approach, which allows you to make prompt decisions on adjusting exploration and operating drilling, to take into account and assess geological risks and the uncertainty of geological objects structure, as well as to increase the coverage of relevant geological models of deposits for user of mineral resources.

Modern methods of well flow test in open borehole include a complex of interrelated technologies which differ in theoretic basis and implementation. They are aimed at reliable oil and gas reserve estimation, enhancement of geological informative value for prospecting and exploration works, choosing of well lower completion, optimization of wells operation and field development.The application of modern well flow tests in open borehole allows undertaking the following tasks: simple pressure measurements at different depths; determination of reservoir pressure at each point of measurement, depth and interval pressure gradient; gas-oil / gas-water / oil-water contact diagnostics; potential productivity estimation and flow rate forecast; recovery of representative reservoir fluid samples.  

The article considers methods and algorithms of modern well flow tests in open borehole used by LUKOIL-Nizhnevolzhskneft LLC, Oil Company Priazovneft LLC, Caspian Oil Company in the course of carrying out and interpretation of well studies in open borehole.

The capabilities of the integrated model are not limited to solving classical problems, such as calculating the selection rates or the technological regime. The integrated model allows to solve non-trivial tasks within the production process. The object of research of this work is the existing integrated models used in the framework of fields pilot development. 

The purpose of the work is to consider the practical application of integrated field models in the production process. Solving operational problems related to risk assessment and analysis of well performances is considered. This calculations on an integrated model gives the possibility to evaluate the used downhole equipment for compliance with the planned operating conditions, recognize in advance the possible risks of stopping gushing, complications during well operation and take measures for its further stable operation. Assessment of the impact of the collection and transport system on production is made. It helped to find the best direction of flowwithout reducing production and increase daily oil production by redistributing flows and changing pressure in the system. Field production scenarios are discussed. Wells interference and influence of neighboring fields is determined. Estimation of field development scenarios on the integrated model allows to identify the most profitable field development strategy. 

Results of this work were implemented and applied in fields development

Careful calculation and selection of the gas-oil ratio (GOR) in laboratory conditions during PVT research is necessary for a reliable estimation of the predicted amount of associated petroleum gas (APG). It is very important to choose a correct separation type for oil with GOR of more than 300 m3/m3. It is noteworthy that GOR values obtained by differential degassing can significantly differ from the results of separation test and field measurements. Significant discrepancy between the predicted amount of APG and that measured at the field can lead to a violation of the Decree of the Government of the Russian Federation of November 8, 2012 No. 1148, according to which Russian petroleum companies must dispose of at least 95% of APG. In the authors’ opinion, the results of reservoir oil separation test are preferable in terms of predicting the volume of APG. In the case of absence of the separation test data, authors suggest creating a mathematical model of the reservoir oil phase behavior, which will provide additional information on the properties of the reservoir fluid and help in solving local problems arising during the development of oil fields. These problems include estimation of the gas volume released from oil at actual thermobaric separation conditions of the current moment, calculated with seasonal temperatures and possible changes in field equipment taken into account.

All over the world there is a tendency to reserves deterioration of hydrocarbon fuels. The share of fields with hard-to-recover reserves is growing, the largest part of which are low-permeable reservoirs. In addition to problems with the development of this type of collectors, there is a difficulty in building of hydrodynamic model of the field. All hydrodynamic simulators are based on the linear law of Darcy flow, so it is difficult to correctly adapt this model to the history of development, because this kind of objects observed nonlinear filtration. The construction of the hydrodynamic model is carried out in the simulator. Therefore, to adapt the model, it is necessary to select the parameters of the filtration medium, which are often far from the real studies of collectors. Tempest MORE of ROXAR, in which there is a possibility of modeling nonlinear filtration for high-viscosity oil with using «locking a gradient filter and a multiplier on the flow». The first one limits the well drainage area; the second reduces the fluid filtration rate multiple times. In the presented paper the possibility of using this method of adaptation of the model for low permeability reservoirs is described. Analytical methods for determining these critical pressure gradients are presented. Critical pressure gradients were analytically determined by using analytical methods on the example of the V.N. Vinogradov oil field with low-permeability reservoir.