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Abstract The article discusses the generalization of the model proposed in [1] for the calculation of the effective properties of the rock sample (periodicity cell) made of an elastic material, dissected by groups of plane cracks. In the original version of the semianalytic mathematical model cracks are represented by elastic springs with different rigidities in the normal and tangential directions [2]. At the same time, the effects of dilatancy and shear deformations because of normal stresses acting on crack’s boundaries are neglected in the crack’s constitutive relation specified by a relationship between the components of the displacement vector and the vector of forces (stresses on the surface parallel to the crack) in the normal and tangential directions. Further, in accordance with the concept of an equivalent medium for the fractured rock samples proposed in [3], cracks’ effective modules are calculated based on the spacing between the cracks and the stiffness of the elastic springs. In order to calculate the total effective elastic tensor of a fractured rock sample a small deformations assumption is introduced, according to which the full deformations are a sum of deformations of the matrix and the fractures. In this paper, by constructing a three-dimensional numerical model of the periodicity cell, we managed to remove both limitations of the original analytical model: a diagonal relationship between displacements and forces in the crack and small deformations. This generalization become possible by modeling a crack as a thin layer of elastic material with Young's modulus and shear modulus computed from the initial normal and tangential stiffness (the original simplified model is obtained by zeroing Poisson's ratio) and taking into account a geometric nonlinearity in the relationship between deformations and displacements of the fracture’s boundaries. Based on the generalized numerical model a finite element model in CAE Fidesys is built capable of varying the parameters of the cracks: the number, spacing, thickness, hardness, etc. The results of averaging are presented for the periodicity cell, dissected by three groups of plane cracks - the first two groups are orthogonal to the third group of cracks and intersect at a predetermined angle. The results of numerical studies on grid convergence, the impact of the size of the periodicity cell and the thickness of the crack on the results of averaging are given. The coincidence of analytical and numerical solutions for a simplified model and the difference between them in the case of a generalized model, leading, in some cases, to the variation of the effective Young's modulus up to 30%, are presented.
Lithofacies Modeling Application in Reservoir Simulation of Low Permeability Carbonates
Suchok, Sergey (LUKOIL International Upstream East) | Obsharov, Pavel (LUKOIL International Upstream East) | Ermilov, Andrey (LUKOIL Uzbekistan Operating Company) | Volnov, Ignatiy (LUKOIL Uzbekistan Operating Company) | Zhukov, Aleksandr (LUKOIL Uzbekistan Operating Company) | Yalalova, Venera (LUKOIL Uzbekistan Operating Company)
Abstract Nowadays there is observed a global trend of ever-increasing complexity and heterogeneity of hydrocarbon reservoirs. More challenging time makes companies take high-risk decisions based on long-term production prediction. As deterministic approach always gives a single result, it loses its relevance when we deal with risks. Generally probabilistic assessment methodology is coming to the forefront. A new approach called RE-Status (Reservoir evaluation status) has been developed in this study. The methodology is based on probabilistic assessment and along with normal uncertainty technique it includes lithofacies modeling. RE-Status is based on six key parameters that allow us to understand reservoir complexity and level of project definition in terms of reservoir engineering. Geological models were created by combining all geological and geophysical data in order to provide the highest-quality 3D representation of heterogeneous carbonate reservoirs. Evaluation of micro-macro heterogeneities and complex analysis of all core studies were used to derive lithofacies. Systematization of stratigraphic analysis, core descriptions and well logging data allowed us to locate facies in reservoir cross-section. It gave us better understanding of the reservoir and nature of filtration processes. The new approach was applied to two gas fields. Impact of reservoir parameters and lithofacies variability on the dynamics of gas production was described. In the first case RE-Status helped to improve history matching by using facies and uncertainty analysis. In the second case (green field) production prediction based on the results of heterogeneity analysis and facies modeling allowed to locate sweet zones, optimize drilling strategy, increase reliability of forecasting and reduce the uncertainty range. Novelty of the described approach is application of facies modeling to reduce key uncertainties, match the reservoir model to historical data and provide the most accurate forecast of production.
- Europe (1.00)
- Asia (0.95)
- North America > United States > Texas (0.46)
- Overview > Innovation (0.55)
- Research Report (0.34)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.47)
- Geology > Geological Subdiscipline > Economic Geology > Petroleum Geology (0.34)
- Geophysics > Borehole Geophysics (0.89)
- Geophysics > Seismic Surveying (0.68)
- North America > United States > West Virginia > Appalachian Basin > Marcellus Shale Formation (0.99)
- North America > United States > Virginia > Appalachian Basin > Marcellus Shale Formation (0.99)
- North America > United States > Texas > West Gulf Coast Tertiary Basin > Eagle Ford Shale Formation (0.99)
- (8 more...)
Abstract This article considers qualitative and quantitative interpretation of spectral decomposition results on the basis of a deposit in Western Siberia. Spectral decomposition as a method of time-frequency analysis is getting extensively used in geophysical during recent years. This fact makes relevant to consider geological structure prediction algorithms on spectral amplitude characteristics. The study proposes a new approach to the interpretation of spectral data – frequency pseudo-cube, which on the one hand allows to optimize interpretation process, on the other hand, allows to use new analysis technics such as principal component analysis and cluster analysis. Approaches to interpretation discussed on a single case that allows to perform a comparative analysis of the methods and to determine the most informative one within particular subject of study.
- North America > United States (0.28)
- Europe (0.28)
Screening Evaluation of EOR Methods Based on Fuzzy Logic and Bayesian Inference Mechanisms
Suleimanov, B. A. (OilGasScientificResearchProject, Institute, SOCAR) | Ismailov, F. S. (OilGasScientificResearchProject, Institute, SOCAR) | Dyshin, O. A. (OilGasScientificResearchProject, Institute, SOCAR) | Veliyev, E. F. (OilGasScientificResearchProject, Institute, SOCAR)
Abstract The choice of Enhanced Oil Recovery methods for specific reservoir conditions is one of the most difficult tasks for a reservoir engineer. Taber gave informative overview of Enhanced Oil Recovery research history. He also offered technical screening guides for Enhanced Oil Recovery nowadays known as Taber's tables. It should be noted that the approach recommended by Taber could not be taken as strong mathematical ranking of Enhanced Oil Recovery methods. This paper proposes approach for Enhanced Oil Recovery methods selection, based on fuzzy logic, possibility theory and Bayesian inference mechanisms. Ranking made by way of best Enhanced Oil Recovery method selection for every criteria using fuzzy intervals comparison. Final correction of each Enhanced Oil Recovery selection coefficient performs by the generalized Bayesian inference mechanisms. Application of this methodology for reservoir conditions of Alberta oil field allowed choosing the most effective EOR method, confirming the accuracy and feasibility of the proposed approach.
- North America > United States > California (0.28)
- North America > Canada > Alberta (0.25)
- Oceania > Papua New Guinea > Papuan Peninsula > Central Province > National Capital District > Petroleum Retention License 15 > P’nyang Field (0.97)
- Oceania > Papua New Guinea > Papuan Peninsula > Central Province > National Capital District > Petroleum Retention License 15 > Elk-Antelope Field (0.97)
- Oceania > Papua New Guinea > Papuan Peninsula > Central Province > National Capital District > Petroleum Retention License 15 > Angore Field (0.97)
- (9 more...)
Abstract We conducted a practical case study that aims at estimating the shapes and parameters of probability distributions for key cost, time and activity performance inputs required by a risk, resource, and value simulator to conduct a stochastic valuation of a new exploration asset. We analyzed a sample of 73 shallow offshore fields in Australia retrieved from a global field-by-field database that includes reserves, production profiles, financials, valuation, breakeven prices, ownership and other key metrics for global oil and gas fields, discoveries and exploration licenses. The reviewed facilities concepts includes 40 steel platforms, 2 concrete gravity-based developments, 10 projects with extended reach drilling, 4 FPSO, and 17 subsea tie-backs. The aggregate CAPEX of projects in the sample over 1965–2015 is USD 99.1 billion (in nominal terms), which is commensurate with the total asset size of the Australian offshore petroleum industry. We estimate probability distributions for all full-cycle parameters required to generate Monte Carlo CAPEX, OPEX, and production profiles. In particular, these include facility CAPEX per unit peak, development phase duration and scheduling rules, drilling expenditures per barrel of oil equivalent, cost of exploration and appraisal wells, OPEX-to-CAPEX ratio, abandonment cost ratio, fraction of hydrocarbons produced yearly at plateau, fraction of hydrocarbons remaining at end-of-plateau, terminal production rate, and fraction pre-drilled wells. Most of the above were found to be log-normally distributed. The paper presents a simple yet robust workflow relying on real industry data that enabled assessing value, risks, and uncertainties of upstream assets at exploration and early appraisal stages. It can be seamlessly extended to other basins owing to a rich coverage of the online field analogs database. The ultimate outcome of the study—a probabilistic value assessment of new exploration asset—represents a modern appraisal methodology relying on a corporation-wide software platform.
- Oceania > Australia (0.89)
- Europe (0.68)
- North America > United States > Texas (0.28)
- Government > Regional Government > North America Government > United States Government (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Oceania > Australia > Victoria > Otway Basin (0.99)
- Oceania > Australia > Victoria > Bass Strait > Otway Basin > Waarre Formation (0.99)
- Oceania > Australia > South Australia > Otway Basin (0.99)
- (2 more...)
- Information Technology > Artificial Intelligence (0.68)
- Information Technology > Software (0.48)
Abstract This work offers a new approach to forecasting the distribution of filtration properties of a formation taking into account the geological properties of the reservoir. The method is based on spectral decomposition of signal for permeability vertical profile. Permeability profile is the input data and is determined by the following methods: normalizing the results of well log data interpretation against the results of well test data interpretation or against the results of production data interpretation (solving inverse problem for unsteady state). For wells which penetrate several layers, Q-Q transformation algorithm is to be used, which will allow distinction of permeability of the sublayer from the total permeability of the layer, based on well logging data. This approach allows obtaining more accurate permeability values as it integrates data received from different sources (well logging data, well test, production data), whereas spectral simulation permits to take into account geological features of the reservoir structure.
- North America > United States > Texas (0.28)
- Europe > Russia (0.28)
- North America > United States > Texas > Permian Basin > Yeso Formation (0.99)
- North America > United States > Texas > Permian Basin > Yates Formation (0.99)
- North America > United States > Texas > Permian Basin > Wolfcamp Formation (0.99)
- (21 more...)
A Methodology for the Refinement of Well Locations During Operational Drilling in Presence of Geological Uncertainty
Babin, V. M. (Gazpromneft STC) | Vashevnik, A. M. (Gazpromneft STC) | Ushmaev, O. S. (Gazpromneft STC) | Gruzdev, A. P. (IBM Science and Technology Center) | Pozdneev, A. V. (IBM Science and Technology Center) | Semenikhin, A. S. (IBM Science and Technology Center) | Quinones, M. Paredes (IBM Brazil Research) | Flach, B. da (IBM Brazil Research) | Ciaurri, D. Echeverría (IBM Thomas J. Watson Research Center)
Abstract In this paper we present a methodology of automated optimal (in terms of NPV maximization) greenfield development strategy construction that takes into account geological uncertainties of the reservoir. The algorithm is based on ensemble of hydrodynamic models and uses the theory of probabilistic graphical models. The proposed methodology allows making dynamic (in the process of field development) decisions about well grid pattern change on the basis of information obtained from the studies on the oil reservoir carried out with the help of the appraisal wells: appraisal boreholes of the development wells and pre-drilling wells (drilling from current pad to the next one for refining geological targets). The decision of the wells pattern option change does not require any additional calculations. The proposed methodology was applied for creating optimal development strategy for one of the new assets (on production stage) of JSC "Gazprom neft". The reservoir development is complicated by the set of uncertain parameters related to the complex heterogeneous structure of the collector. The parameters have very high influence on the optimal decision choice. As result expected NPV is increased by 15%.
- South America > Peru > Loreto Department (0.46)
- North America > United States > Texas (0.28)
Abstract The development increasingly involves reservoirs with low and ultra-low permeability reservoir. "Traditional" welltest analysis technologies in such reservoirs lose their efficiency (Davletbaev A.Y., Zhylko E. Y. etc. 2015, Loznyuk O.A. etc. 2015) as they require long-time shut-in (about 1 month and more), which causes huge losses in production (Davletbaev A.Y., Islamov R. R etc. 2015). In such conditions, analysis of usual operation data analysis and decline analysis become relevant (Arps J.J. 1945, Fetkovich M.J. 1980, Ilk D., Blassingame T.A. 2013, Doublet D.E. etc. 1994). This method has a lot of limitations, in particular, it is necessary to know the value of the reservoir pressure at the moment of the reservoir operation for interpretation, which is not always possible in the conditions of the operation and maintenance phase. The present work offers the method permitting to increase the informational content of the decline analysis, as well as to determine the value of initial reservoir pressure by combining «short» build-up welltest analysis with decline analysis in the operating well.
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Drillstem/well testing (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring (1.00)
- Data Science & Engineering Analytics > Information Management and Systems (1.00)
The practice of fractured reservoir development suggests that the description of the well-bed system operation would not often conform to the behaving predicted by classical theories of filtration for fractured systems (Warren-Root et al.). It is possible, when the stratum may not be represented as a homogeneous system, and inhomogeneity dimensions significantly exceed the borehole diameter. Under certain conditions, productivity substantiation and forecast of further work are possible, providing conventional well logging methods are used. When the survey target becomes more complicated, e.g., in the course of horizontal well logging, the solution appears to be ambiguous, thus requiring development of a new approach to interpretation. To understand the processes during development of the reservoirs in question, computing model calculations were carried out. Various options of vertical well locations in respect of the joint set system, as well as various combinations of configuration of the fractured reservoir entered by a horizontal well were considered. Obtained forward solutions were compared with actual well test results and demonstrated similarity of the anomalies observed. As the result, a set of parameters most affecting the field response was obtained, recorded during field research, which enable determination of a list of additional information necessary to complement the interpretation process. The above surveys enabled working out and implementing of the approach of sequential interpretation of well testing and logging, based on integration of the results thereof with different-scale data (well log interpretation data, attribute seismic survey interpretation, geotechnical survey) to describe the well stream model. The following results were obtained by implementation of the described approach: Based on application of the proposed set of studies, a refined well stream model was obtained for analyzed deposits, specifically, for more than 15 horizontal wells, taking into account the dominating fracture influence on inflow rate; Based on the results of the refined filtration model, the current sampling levels for wells were justified and further work forecasts taking into consideration new filtration particularities were prepared; Recommendations of targeted geological and technological activities aimed at elimination of negative factors were issued for the wells with production performance inconsistent with the potential level. The following conclusions may be drawn, using the obtained results: The importance of well location (both vertical and horizontal wells) in respect of the natural macrofracture system is proven in practice; Simulation of survey results in a computing model has proven the dominating influence of the number of fractured intervals penetrated by a horizontal well on the well stream profile, and therefore on its productivity; Activities aimed to increase the horizontal well productivity in a fractured low-permeable reservoir shall be focused on search and involvement of the maximum quantity of natural fractures; In case it is impossible to efficiently forecast the fracture position in the stratum, artificial initiation of such fractures is needed. An approach to description of well performance under conditions of ineffective conventional filtration theories for fractured reservoirs has been worked out. Based on the results of practical implementation of the worked out approach, the well stream model for horizontal wells of one of the fields in the Volga-Urals Region was justified. This enabled updating of the current production levels for wells, optimizing well operating modes, issuing recommendations of enhance production operations.
- Overview > Innovation (0.48)
- Research Report (0.46)
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Seismic Surveying > Seismic Interpretation (0.34)
- Well Drilling > Drilling Operations > Directional drilling (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Well performance, inflow performance (1.00)
- (2 more...)
Automatization of Right Drilling Mode Selection and Troubles Prediction While Designing and Constructing Oil and Gas Wells
Lind, Yu. B. (LLC BashNIPIneft) | Gabbasov, B. M. (LLC BashNIPIneft) | Khashper, A. L. (LLC BashNIPIneft) | Khashper, B. L. (LLC BashNIPIneft) | Galeev, S. R. (LLC BashNIPIneft)
Abstract The purpose of the work is development of informational and analytical system which allows to make recommendations on selection of optimum drilling parameters (type and parameters of drilling fluid, type and characteristics of bits and motors) on the base of field data on drilled wells of an oilfield for effective drilling meterage of wellbore and prevention of troubles in drilling new wells.
- Well Drilling > Drilling Operations (1.00)
- Data Science & Engineering Analytics > Information Management and Systems (1.00)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid selection and formulation (chemistry, properties) (0.89)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid management & disposal (0.71)