bluuebunny/crossref_metadata_2025 huggingface dataset:
First Four-Lateral Well at the Umseyskoe Oilfield: A Case Study
Authors: Anton Ablaev , Vyacheslav Kretsul , Igor Petukhov , Vitaliy Kiselev
Published: October 2016

This paper describes the experience of the construction of the first Gazpromneft multilateral well on Umseyskoe oil field. The joint work of the operator and service companies applying an integrated engineering approach enabled the successful construction and completion complex wells.

When preparing for the project, two-, three-, and five-lateral well designs were evaluated. As a result, based on economic feasibility and minimization of technological risks, a four-lateral well design was choosen. Drilling of these type of multilateral wells requires greater flexibility in changing the actual profiles and sidetrack depths, taking into account actual lithology, which will reduce the risks associated with BHA (bottom hole assembly) sticking at the sidetrack intervals.

To reduce risk during geosteering of multilateral wells it is extremely important to obtain operational geological and technological information during the drilling process. Obtaining this information is enabled by telemetry systems that transmit data to the surface, providing directional indications of natural radioactivity of rocks and their electrical resistivity.

An RSS (rotary steerable system) was used in combination with a postivie displacement motor (PDM) BHA and special drilling mud to provide high-quality openhole laterals during well construction. As a result, liner completion was successfully run to the final fourth lateral through three upper sidetrack points for other laterals.

A comprehensive engineering approach to solving the well construction issues enabled the successful construction of the first four-lateral well at Umseyskoe oil field.
Engineered Solution Helps Cure Total Losses in Bashkortostan, Russia
Authors: Ivanov Aleksey , Slavich Vladimir , Kharitonov Andrey , Lischuk Vasily , Gnativ Vladimir , Mukhametzyanov Irek
Published: October 2016

Severe losses into the Upper Carbon, Lower Carbon, and Myachkovsky horizons in Bashkortostan, Russia have been a major issue for many years and impact the operator’s ability to reduce well construction time and costs. Well No. 5 experienced total fluid loss while drilling, resulting in no returns while circulating and a fluid level of 160 m rotary kelly bushing (RKB) while static.

Over a period of 30 days, multiple methods and lost circulation materials (LCMs) were used by various companies without significant and/or long-term success. The service company’s previous experience in the area showed that high fluid-loss (HFL) pills work to completely seal troublesome zones or to minimize losses to an acceptable level. After analysis of the approaches used to date and their efficiency, a HFL pill was designed that contained materials with a multimodal size distribution to widen the range of fractures that would be sealed. To enhance the effectiveness of the treatment, reticulated foam material was added to the pill.

Engineering calculations indicated that a total of 15 m3 of the engineered LCM blend should be pumped down hole. The HFL LCM pill was prepared in a batch mixer; it consisted of 280 kg/m3 of the multimodal material and 1.3 kg/m3 of a proprietary reticulated foam material. The blend was delivered into the loss zones, using 89-mm drillpipe at low pump rates of only 10 to 12 L/sec. Full returns of drilling fluid were observed after pumping only 13 m3 of the LCM blend. The pill was left static for several minutes (with pressure applied) and then circulated back to surface. A return rate of 100% of the fluid was reported when circulating at full rate, indicating that the specially designed HFL LCM pill was effective and robust, creating an effective long-term seal that was resistant to erosion.

A 100% return of the drilling fluid was reported for the first time since the losses were observed while drilling the well. Notably, the approach used required minimal time, equipment, and LCM materials. Following the successful application of the HFL pill, the strategy to prevent lost circulation was adjusted to account for this new technology. It has since been extended to other areas in the country.
A Holistic Approach to Improving ESP Reliability and Energy Efficiency at Van-Yogan Field
Authors: Fastovets Andrey , Samoylin Vladimir , Sharafeev Rafael , Yakimov Sergey , Kaverin Mikhail , Firsov Anton
Published: October 2016

The paper describes the methodology and specific action items developed and applied jointly by the operating company and contractor teams to achieve significant improvements in reliability (run life) and reduce power consumption in more than 300 artificially lifted wells equipped with electric submersible pumps (ESPs) in the harsh environment of Van-Yogan field in Russia, Western Siberia. The extended duration of the project, which started in January 2012 and is currently ongoing, offers a unique opportunity to review and analyze the longer-term contribution and efficacy of the various methods presented.

To date, the project has delivered consistent improvements in both energy efficiency and equipment reliability, translating to substantial savings in the lifting costs for the operator. Average pump efficiency increased by 4.3 percentage points (from 60.4% to 64.7%), which is an excellent result considering the average pump flow rate decreased from 240 m3/d to 182 m3/d during the same period due to overall aging of the field. It is widely known in the industry that smaller pumps generally return lower power efficiency figures; therefore more efficient novel pump designs and operating procedures had to be introduced to facilitate this efficiency improvement.

Despite continuously deteriorating well conditions under the adverse influence of scales, corrosion and production of high volumes of free gas and solids through the ESP, average pump run life was extended by 101 days since the project start date (from 335 days at the beginning of 2012 to 436 days at the end of 2015, or by more than 30%). At the same time, Mean Time Before Failure (MTBF) improved by more than 56% over the same period (from 511 to 796 days), decreasing workover costs and deferred production.

The comprehensive approach includes accurate ESP selection to better match well conditions, use of high-efficiency ESP pump and motor designs, flawless field service execution, and continuous monitoring and fine tuning of equipment performance. Inspection of dismantled equipment and failure root cause analysis (RCA) plays a fundamental role to ensure that adverse well factors are properly addressed by ESP design and operating procedures.
Performance Analysis Of Different Formation Testing Technologies In Complex Carbonate Reservoirs Of West Kazakhstan
Authors: Charupa M. , Ramatullayev S. , Mendybaev N. , Zhabagenov M. , Alzhanov A. , Kravets P.
Published: October 2016

Objectives & Scope

The case study presents an application and comparison of different wireline formation testing technology to acquire vital pressure data and downhole fluid samples in tight sub-milidarcy heterogeneous carbonate fields. Examples from Kazakhstan, where tools with different configuration of fluid intake positions and shapes, various flowing areas, are presented to allow us to compare and contrast the performance of each in more complex and challenging reservoir conditions.

Methods, Procedures, Process

First part of the study discusses the comparison between inflatable straddle packer and radial probe in terms of their data quality and efficiency of the acquisition, where both of the tools were deployed to measure formation pressure, conduct downhole fluid analysis and acquire downhole fluid samples. While the second part focuses on comparison between single probe and radial probe, where both of them were deployed in the well together and were intended to get formation pressure measurements in the zones with the lowest porosity.

Results, Observations, Conclusions

Extreme downhole conditions pose a challenge to formation testing, acquisition of accurate reservoir pressure data and representative formation samples have proved difficult in cases of highly heterogeneous low porosity and low permeability reservoirs. In the first part of the study, the performance of the each tool compared with different observations such as: average time to first hydrocarbon, average volume to first hydrocarbon, water fraction content, and sampling and downhole fluid analysis by formation zones and by mobility ranges. In the second part, the study elaborates on pressure survey conducted in tight highly heterogeneous carbonate reservoir, where tool with large flowing area and circumferential flow shows its superiority, thus improving operator's reservoir evaluation. Downhole positions of both tools against formation features, such as vugs, porous spots and anhydrite inclusions, were reconstructed on microimager log.

Novel/Additive information

This case study describes and compares the approaches and methodologies to acquire and perform complex interpretation of critical formation pressure data in heterogeneous carbonate reservoir. The learnings from this successful acquisition and interpretation can substantially improve the reservoir characterization of similar fields worldwide.
Determination of Reservoir Properties and Heterogeneity through Pressure Transient Analysis for a Clastic Gas Reservoir
Authors: Guizada Pablo , Al-Harbi Abdulaziz
Published: October 2016

A clastic gas reservoir, have been characterized of being unconsolidated in nature, as well as its complexity and heterogeneity. Regarding to the ability to transmit fluids, this reservoir is predominantly tight with a wide variation in the permeability range, which confirms its heterogeneity. The depositional environment interpretation suggests the presence of channels running from West to East direction with kind of limited lateral extension. In terms of well completion strategy, most of the wells have been proppant fractured to produce at sustainable rates.

Pressure transient analysis (PTA) has been applied extensively to better characterize and understand the reservoir behavior, well performance and to obtain significant properties of the reservoir. The challenges of this work consisted of performing a critical review of the existing PTA to identify some common behaviors or general trends in the pressure response. Considering the PTA have assessed the same reservoir and that several wells have been completed with similar completion techniques was expected finding similar pressure response behaviors.

This paper presents different cases that have been analyzed through PTA, summarizing common trends, in terms of reservoir behavior and well response that have been observed during the study. The outputs of this study were used as inputs for the simulation reservoir models to narrow the uncertainty in some reservoir and wellbore properties and as inputs for the static model construction to better understand or confirm geological assumptions. The results of the PTA interpretation also helped to successfully drill newer wells away from any geological complexity and achieved the planned target of gas rates.
Wireline Formation Tester Data for Reserves Classification: The Russian Methodology and Experience.
Authors: Khoshtariya V. N. , Martyn A.A. A , Kurdin S. A. , Dmitriev S. E. , Abdrakhmanova L.G. G , Blinov V. A. , Weinheber P. , Ivashin M. D. , Novikov S. V. , Krupeev V. A. , Svikhnushin N. M. , Khaziev M. I.
Published: October 2016

The Russian Federation mandates a Russia-specific reserves reporting and classification system for all operating companies in the country. One of the key classifications thresholds within this system is from C2 to C1. According to the existing definitions moving reserves to C1 category requires 'industrial production' and this has traditionally meant an openhole DST. After much work with operating companies and the regulatory authorities this definition has been expanded to include wireline formation testers. In this paper we discuss some of the recent history behind the efforts that have led to this outcome.
A Methodology for the Refinement of Well Locations During Operational Drilling in Presence of Geological Uncertainty
Authors: Babin V. M. , Vashevnik A. M. , Ushmaev O. S. , Gruzdev A. P. , Pozdneev A. V. , Semenikhin A. S. , Quinones M. Paredes , Flach B. da , Ciaurri D. Echeverría
Published: October 2016

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%.
Palaeozoic Reservoirs Geology Prediction and Exploitation Monitoring Features: Case Study of Tomsk Region Fields, Russia
Authors: Gritchina Vladlena , Kaeshkov Ilya , Nizamov Eduard
Published: October 2016

Paleozoic deposits, characterized by complex geological structure, require a special approach to lateral properties variation prediction. Typical correlation associations and dependencies showed limited relevance of statistical methods and low predictive potential for seismic analysis. Comparable complex structured reservoirs can be confidently predicted by traditional approach of geological similarity.

Regardless of complications mentioned, Paleozoic reservoirs production is effective and close to planned values at the moment

After a logical move beyond slanted well to horizontal ones, it is planned to drill multilateral wells as a next step to reduce uncertainties influence on production and to increase oil production profitability.

Non-conventional informational capacity of exploitation monitoring complex for Paleozoic deposits is shown in the paper in addition. Some examples are introduced and well test data usage for porous and filtration media type selection is demonstrated aiming at hydrodinamic model enhancement.
New Rapid Modeling Technology to Select Optimal Waterflooding Options for Oil Fields
Authors: Rodionov S. P. , Pichugin O. N. , Kosyakov V. P. , Musakaev E. N.
Published: October 2016

The article describes a computational technology to optimize a reservoir development system with known well locations. It includes a number of algorithms for determining the optimal options of setting injection and production wells or well perforation intervals.

The proposed technology is based on a combination of the Lagrange-Pontryagin formalism, the analytical solutions of flow equations, and a "greedy" algorithm. Such an approach to the problem ensures a hugegain in computation time, even for fields with a large number of wells.

The best well perforation intervals were determined in terms of oil recovery or the development system economics, or well perforation intervals in symmetric elements of different well patterns with a nonuniform distribution of flow properties using real fields.

The computational efficiency of the proposed algorithms was studied and their benefits in comparison with existing analogues were demonstrated. It has been found that the algorithms allow to get one of the most favorable options of the development system or well perforation intervals in a practicable time.
4D Geomechnical Model Creation for Estimation of Field Development Effect on Hydraulic Fracture Geometry
Authors: Pavlov Valeriy , Korelskiy Evgeny , Butula Kreso Kurt , Kluybin Artem , Maximov Danil , Zinovyev Alexey , Zadvornov Dmitriy , Grachev Oleg
Published: October 2016

A 3D geomechanical model was constructed to estimate the influence of the initially placed propped fractures and the pressure variation with time in active field development on the stress-state redistribution.

The main task of paper was to research the different parameters influence on stress state condition and especially on possibility of stress reorientation due to field development. In addition, the main purpose of the paper is to fiend impact of acting processes on hydraulic fracturing propagation.

A finite element method was applied to calculate the stress state in a target sector of the oil field. All available seismic data and pertinent well logging data were used to update the geological and hydrodynamic models, and data from hydraulic fracturing, 1D geomechanical modeling, and drilling history were used for verification of the modeling results. In the following paper the reservoir parameters which can be useful for other fields of West Siberia were used.

The 3D geomechanical model was created and used for the stress-state redistribution forecast, taking into account the field development history. The model was built by coupling the geomechanical finite element and compositional numerical reservoir simulator result at two time steps –the initial, virgin state and the current state of the field development.

It has been shown that the change in reservoir pressure has a significant influence on the value of the horizontal stress in the area of interest, whereas the change in stress orientation depends on the reservoir height, layout of wells, field development stage, and mechanical properties of the rock. Near the initial fractures, the fractures themselves have a strong influence on the magnitude and orientation of the horizontal stress.
Plane-Strain Propagation of a Hydraulic Fracture in Porous Media
Authors: Ulkin D. A. , Khodos O. A.
Published: October 2016

Hydraulic fracturing (HF) in a plane-strain environment is addressed by using continuum mechanics. Fracture propagation is expected in quasi-stationary mode (i.e., not account for inertial effects and the fracture width is smaller than its length). Irwin's fracture criterion is used to govern the growth of fracture length. The internal problem of incompressible fluid motion in the fracture is described by Poiseuille's law. Fracture and fluid are propagated independently, so a fluid-free domain (lag) might exist near the fracture tip. The external problem of stress state in the unbounded medium with the fracture is addressed by the linear elastic law. The solutions to the internal and external problems are fully coupled (pressure in fluid is equal to normal stress on the fracture boundary; the half width of the fracture in the internal problem is equal to the displacement of the fracture boundary in the external problem). Fluid leakoff to the media through the boundary of the fracture is addressed by local Darcy's law. Under these assumptions, a system of integral-differential equations is built to address the problem. The equations of the system are analyzed by nondimensionalization and application of the method of similarity. Three modes of fracture propagation are examined, depending on the relative magnitude of the fluid leakoff to the media—no leaks, with predominant leaks, and general. The no leaks and predominant leaks modes are revealed to have asymptotically self-similar behavior to the solution in all physically meaningful cases. In a general case of nonzero in-situ stress, a new self-similar solution exists for the power law fluid injection rate with an exponent 1/3. Symmetry of the system of equations under the group of scaling transformations enables the time dependence of self-similar solutions in explicit form. An implicit conservative difference scheme is used to construct the effective algorithm for a numerical solution to fracturing in a complex plane-strain environment. Verification of obtained results is determined by a qualitative comparison with experimental data and known self-similar solutions.
Modified Approach to Incorporating Hydraulic Fracture Width Profile in Unified Fracture Design Model
Authors: Paderin G. V.
Published: October 2016

Hydraulic fracturing is one of the most effective ways to stimulate oil production. To this end, our study suggests an algorithm of calculating the optimal hydraulic fracturing design based on a modified approach to incorporating hydraulic fracture width profile in the context of unified fracture design (UFD) concept. Vertical propagation of fracture is controlled by the plane-strain problem of brittle fracture mechanics. To determine equilibrium height of hydraulic fracture, we suggest using the Irwin criterion, which implies that stress intensity factor equals the value of fracture toughness in a multi-layered structure. Fracture growth profile is calculated by solving a 2D elasticity problem in the context of three-layer approximation. Calculation of hydraulic fracture length is based on PKN model for power-law rheology fluid and specified proppant concentration schedule based on Nolte model. Injected volume, pumping time and fluid efficiency are determined by iterative solution of material balance equation. Hydraulic fracturing optimization involves selection of parameters of fracturing operation, including injection rate and rheology of fracturing fluid for maximization of dimensionless productivity index.

The proposed model was used to formulate a numerical algorithm for hydraulic fracturing design calculation and its optimization in the context of the above presumptions. This optimization approach further develops the unified fracture design concept and adds to it the advanced model of fracture width profile calculation. The presented algorithm of design calculation and optimization helped to significantly increase the accuracy of hydraulic fracture geometry and net pressure calculations, which is confirmed by comparison with commercial software.
Remaining Oil Characterization through Surveillance Data Analysis for a Mature Giant Sandstone Reservoir in Middle East
Authors: Yong Li , Lihui Xiong , Baozhu Li
Published: October 2016

M reservoir is a mature giant sandstone reservoir in Middle East with more than 60 years' production history, which has been developed via natural aquifer support followed by peripheral water injection of low salinity waters. Understanding of water flooding swept characteristics can significantly improve the understanding of remaining oil distribution. This paper presents a detailed study on remaining oil characterization mainly based on surveillance data.

Firstly, a workflow for remaining oil characterization mainly based on production logs and saturation logs are proposed. Then based on the surveillance data and the proposed method, lateral and spatial distribution of fluid saturation are gained by gridding surveillance data, and a series of predicted saturation maps by layer and by year are generated. And through comparison with saturation maps of different years, habitats of remaining oil are determined, and corresponding development strategies are proposed.

In this study, more than 300 wells with saturation logs and production logs were tested within 5 years for M giant multi-layered reservoir. Maps of every layer of each year between 2012 and 2015in M reservoir for remaining oil saturation and pure oil thickness were generated, and remaining oil spatial distribution are also generated for each year respectively. The remaining oil change of different years illustrate the variability of waterflooding patterns, swept characteristics and waterflooding drive mechanisms. And habitats of remaining oil were also determined, and corresponding development strategy are also proposed.

This study helps determine the locations of new wells and better development and adjustment strategy decision for mature multi-layered sandstone reservoir. Most importantly, the methodology presented can be adopted in other similar multi-layered sandstone fields.
A Novel Cost-Effective Approach for Enhancing Capillary Number while Stimulating Abu Dhabi Tight Carbonate Reservoirs
Authors: Ansari Arsalan , Haroun Mohammed , Rahman Mohamed Motiur , Chilingar George V.
Published: October 2016

Electrokinetic Low-concentration acidizing is one of the emerging technologies where the application of the Low-concentration acidizing is integrated with electrokinetic enhanced oil recovery (EK-EOR) as presented in previous studies [Ansari et al., 2014-2015]. This research focusses on analyzing the effectiveness of the EK LCA-IOR process in Abu Dhabi tight carbonate reservoirs by qualitatively analyzing the improvement in the capillary number and increase in depth of penetration.

Core-flood tests were conducted by saturating Abu Dhabi carbonate core-plugs with medium crude oil in a specially designed core-flood setup at reservoir conditions. After the waterflooding stage, EK LCA-IOR was applied under optimum conditions (1.2% HCl concentration, 1V/cm voltage gradient), where acid was injected and transported by EK to the target producer. Moreover, the capillary number change, Single Energy CT Scan (SECTS) and oil API gravity change results were analyzed in order to observe the effect on rock-fluid interaction to control rock adsorption capacity through interfacial tension and depth of penetration.

Several correlations at reservoir conditions related to acid concentration, displacement efficiency and permeability enhancement have shown that the application of waterflooding on the carbonate cores yields an additional 15-28% oil recovery beyond the waterflooding limit (58%), recording a maximum oil displacement efficiency of 88% and maximum permeability enhancement of 53%.EK LCA-IOR also improves the capillary number by 500% in Water-wet core plugs and 1500% in Oil-wet core plugs, mainly due to a decrease in interfacial tension, increase in crude oil API gravity by 20-40% with an increase in API gravity of about 10-18%. The use of SECT imaging confirmed wormhole orientation and propagation length across core-plugs, precisely delivering the acid front throughout the core-plug and also indicate the decrease in acid adsorption as acid is precisely transported to the targeted production well through the tortuous path.

EK LCA-IOR may offer a feasible option to augment the efficient unswept oil displacement allowing us to save on the OPEX by maintaining decreased power consumption while reducing the acid/water requirement upto 10 times as compared to currently applied conventional EOR methods. This study takes one step forward towards the development of EK LCA-IOR method feasible for complex tight carbonate reservoirs in UAE.
Restriction of Gas and Water Inflow to a Horizontal Oil Producing Well as the Case in the Field of a Name Yu. Korchagin
Authors: Mett D. A. , Suhodanova S. S. , Abraeva T. I.
Published: October 2016

Work is devoted to increase of efficiency of development of subgas oil deposits with the spreading water-saturated horizon. Increase of efficiency is observed due to decrease in volume of intake of gas and water in a production well at preservation enough big rates of selection of oil. The similar effect is reached by side track kickoff in a gas cap and a technology trunk in the water-saturated horizon.

On the basis of the created model, operating modes of the "constraining" trunks, and also an optimum depression in an oil-extracting well have been chosen. At the same time for preservation of equilibrium system the received and drained gas was pumped back in a gas cap, considerable volumes of in passing extracted water were dumped to the water-bearing area.
Development of Reservoir with Gas Cap and Underlying Water on Srednebotuobinskoye Field
Authors: Ivanov E. N. , Akinin D. V. , Valeev R. R. , Nikulin E. V. , Sultanov R. B.
Published: October 2016

The Srednebotuobinskoe Oil Gas Condensate Field (SBOGCF) is one of the largest fields in East Siberia (the Russian Federation). It is characterized by the presence of massive gas cap and bottom water. The analysis of early production data indicated the key challenges in developing formations containing contact reserves: gas coning and early gas breakthrough in producers, as well as small production levels. Development of such fields entails geological risks and uncertainties with drilling and well operation.

The paper looks at the evolution of development approaches: drilling horizontal wells in complex Bt Horizon of the Srednebotuobinskoe Field. System-based geological and production data analysis method is employed in the study.

The solutions envisage the use of various drilling and well operation strategies depending on saturation zones in complex fields, which provides flexibility in regulating the development strategy in the field through the application of horizontal wells.
Modeling Gas Condensate Well Productivity in Consideration of Trapped Phases
Authors: Mikhailov N. N. , Voronich I. V. , Shelepanov S. S.
Published: October 2016

This paper is devoted to the providing more accurate modeling of the hydrodynamic processes in the gas condensate reservoirs and investigates the influence of near-wellbore region on the gas condensate well deliverability.

For increasing of accuracy it was used Forchhamer's equation as filtration law. As opposed to Darcy law this equation simulates properties of flow at high Reynolds numbers that typical to gas condensate reservoir. As the nonlinearity coefficients in Forchheimer equation were taken functions of porosity and permeability, proposed by different authors. In addition, there were simulated such effects as the capillary trapping of phases, the formation compressibility and the mudding of the near-wellbore area. The capillary trapping effect was simulated by empirical dependence of the residual saturation as function of the capillary number. Residual saturations were arguments of the function of relative phase permeability.

The studies showed that the difference in productivity of wells can overcome 50 per cent in case of using in numerical model the nonlinearity coefficients proposed by various authors. The importance of modeling the capillary trapping effects was corroborated. An essential nonadditivity of considered factors affecting the productivity of wells was shown. It was found that a depression increase in hydrophobic reservoirs leads to a greater relative increase of well deliverability in contrast to hydrophilic reserviors. Furthermore, in the research was simulated the change of the wettability in parts of borehole area from hydrophobic state to hydrophilic and vice versa. It was shown that well deliverability as function of a radius of area with modified wettability has extrema. From the analysis of the data obtained it was concluded that the changes of wettability in near-wellbore area can improve well deliverability, but the optimum size of the area with modified wettability depends on the presence in the formation of capillary trapped water. Thus, radius of the area with modified wettability may be optimal for one configuration of the trapped water or lead to a decrease of deliverability in other cases. Such effect should be considered during attempts to increase deliverability by modifying type of near-wellbore area in terms of wettability of the formation.
Complex Research of Bazhenov Formation Samples Using Digital Rock Approach
Authors: Shklover V. Ya. , Artemov N. A. , Rashkovskiy A. I. , Dmitrieva T. G. , Zagvozdin V. P.
Published: October 2016

The rocks of the bazhenov formation are hard to recover reserves. One of the problems related to the calculation of reserves of hydrocarbons confined to deposits of the bazhenov formation is the lack of a comprehensive approach to the detailed study of the properties of these rocks. Challenge of industry is to develop an approach to the definition of the parameters needed for the assessment and calculation of oil and gas deposits related to deposits of the bazhenovfFormation.

In this paper, the authors propose a multiscale approach to the study of the bazhenov formation samples, which allows us to characterize the different levels of the void space, structure and composition.

The aim of the study was to determine the possibilities of modern bulk multiscale microscopy for solving problems on the properties of bazhenov formation samples and improve the accuracy of input data for reservoir properties modeling.

To achieve this goal it was necessary to solve the following problems: Clarify and complement the structural information obtained by traditional methods (X-ray microtomography), by mineral composition and porosity of the core in the micron and submicron scale.Assess the reservoir rock properties in a wide range of scales with division of different types of porosity.

The work served as a multiscale assessment process for bazhenov formation samples.
Selection of Unconventional Core Workflow Depending on Field Goals
Authors: Karpov I. , Mamyshev T. , Kostin D. , Zhukov V. , Strizhnev K.
Published: October 2016

Bazhenov Formation (BF) is a complex study target, not only in terms of getting the flow of oil, but also in terms of studying and parameterization of its implementation on the basis of complex laboratory tests. "Standard" approaches to core studies are not applicable to the BF due to the destruction of rocks over time from exposure to air and liquids. Specialists, who analyze core material, are often encounter a lack of manufacturing capabilities of conditioned samples required for the measurement of physico-chemical and estimation parameters.

The purpose of this work is to optimize the operations with core material from source rocks on the territory of the company Gazprom Neft PJSC, which are aimed at maximum recovery of geological information while ensuring the best preservation of core material.

To address this objective it is required to perform an integrated approach for analysis of the core material at all stages - from the selection of suitable coring technologies, operations with a core "in the well" and transportation of the core to the laboratory to selection of the optimal sequence (algorithm) of the sample preparation and laboratory tests, depending on the set of commercial applications.

It is assumed that the section of the BF can be divided into a series of intervals formed by rocks, differing from each other by physico-chemical and filtration parameters. One group of intervals may be involved in the development by creating a pressure differential in the well-reservoir system, the second - by creating artificial fracture network by applying the fracturing technologies, the third will be the result of thermal effects on the rock. A list of studies was compiled on the basis of the basic assumptions of non-uniform vertical structure of the section of BF, that allows addressing a series of commercial tasks: how intervals with different properties are spread in the sections of the BF, the presence of movable hydrocarbons, filtration-capacity parameters range of intervals. To implement a list of studies, that take into account these features, "a roadmap" for research was composed, including the required handling procedure for core material.

The work shows the influence of the selection of technology, transportation, storage and sample preparation methods on the amount and quality of information obtained from geological core material of source rocks in Western Siberia.
Express-Method of Assessing the Effectiveness of Acid Compositions for Oil Production Stimulation in Relation to Geological and Physical Conditions of Specific Formation
Authors: Silin M. A. , Magadova L. A. , Gubankov V. B. , Tsygankov V. A. , Veremko N. A.
Published: October 2016

As you know, most acid compositions intended for use in oil and gas production stimulation technology contain various surface-active agents (surfactants).

During the filtration experiments the efficiency of surfactant-contained acid compositions is assessed by an increase of core permeability, which may be the result of two processes: dissolution of rock material and washing off the oil from porous medium surface. When both processes are at the same time, it is impossible to estimate the contribution of each of them.

The express-method involves research on single cores. Only in case of the positive result of acid composition application regarding an increase of permeability and porosity of the core sample, you can proceed to the complete simulation on core samples with residual water or oil saturation.

The filtration experiments are performed with a high pressure filtration unit and extracted core samples.

The new approach is to replace a complicated research process of acid stimulation effect in order to select the most effective compositions, and the use of a simple study on a single water-saturated and oil-saturated core. This will reduce the work of testing acid compositions by eliminating the time-consuming research process on a stacked core model, as well as prevent from using the inefficient acid compositions in the field.

In contrast to the experiments to determine the coefficient of oil displacement by water, as well as experiments to determine the curves of phase permeability, in which stacked core models are applied to avoid end effects, in this case a core material single-sample is used, since the main purpose of these experiments is to identify the impact of acid composition on the reservoir properties.

Secondly, the feature of this method is the fact that allows you quickly and without additional expensive studies of the structure and composition of the core material, not only to select, but also to adapt the acid composition to the specific formation and porous medium conditions and characteristics.

Thus, the further research is carried out only with the selected acid compositions excluding the rest of provided testing acids, saving a considerable amount of time and money.
Selection of Adequate Reservoir Models for EOR Laboratory Simulation
Authors: Putilov I. S. , Rekhachev P. N. , Gurbatova I. P. , Barkovsky N. N. , Yakimov O. I.
Published: October 2016

The publication reviews the influence of core samples on reliability of data collected during laboratory simulation of formation stimulation techniques depending on the type of reservoirs.

The analysis has shown that, as opposed to composite models, a full-size core displays the interconnection of pore systems in complex reservoirs in the best possible way, and this makes it possible to draw more correct conclusions on the efficiency of techniques such as assessment of adsorption and mechanical destruction of polymer compounds, strength of the built waterproof barrier, pressure dynamics during injection, etc. When selecting full-size core samples, in order to increase reliability of the laboratory simulation data, it is necessary to consider rock anisotropy that is inherent to carbonate reservoirs and is generally associated with rock fracturing.

Based on the obtained knowledge about improvement of EOR simulation efficiency under complex carbonate reservoir conditions, laboratory analyses have been carried out using core material and METКA thermoreversible polymer compound developed by the Institute of Petroleum Science, Russian Academy of Sciences, Siberian Branch. The usage of a full-size core made it possible to assess the efficiency of METКA technology in terms of involvement in the development of not only low-permeability layers, but also high-permeability formation zones which have not been covered before or lightly covered by water-flooding. The analyses carried out using composite models from a standard-size core showed that the obtained data in terms of assessment of water-flooding coverage had low informative value.

Thus, it was found that core samples of the maximum diameter must be used for testing under complex carbonate reservoir conditions due to low representativity of standard samples.

The obtained findings are of practical importance in terms of correct assessment of EOR parameters for wells during field development.
Tight Oil in Oil-And-Gas Source Carbonate Deposits' Gas Saturation Zones of Gas-Condensate and Oil-Gas Condensate Fields
Authors: Skibitskaya N. , Bolshakov M. , Burkhanova I. , Kuzmin V. , Surnachev D.
Published: October 2016

Research is based on conception about field as not only migrating fluids trap with formed pore volume and shielding cover but as self-assembling oil-gas source system on one or another oil-gas generation stage.

In order to study oil-and-gas source carbonate rocks in detail a core studying laboratory investigations complex was developed. Core samples, salt exhausted but not extracted, were studied by petrophysic, geochemical, electron microscope and physicochemical methods.

Complex treatment to investigations allowed to discover regularities of carbonate oil-and-gas source deposits' catagenetic transformations. These regularities were put into created hearth-clustered algorithm for rock properties modeling. A hearth-clustered conception taking into account oil-and-gas source rocks' transformation regularities would allow to differentially estimate and classify hydrocarbons reserves and also choose directed recovery technologies in hearths' pay zones which correspond to different organic matter and rock-forming matrix catagenetic transformation stages.

Geological hard-to-recover oil reserves in gas-saturated zones of gas-condensate and oil-gas-condensate fields are traditionally not considered in estimation of reserves, nor in field-development program but they represent tremendous unaccounted and not realized resource base of Russian Federation in regions and fields with wholly developed infrastructure. They should be necessarily considered in design estimates as on early so on late field development stages.
Probabilistic Assessment of Single Well Source Rock Oil Recovery in Terms of Geological and Technological Uncertainties
Authors: Nenasheva M. , Demo V. , Zhukov V. , Shevchuk T.
Published: October 2016

The Bazhenov formation contains huge hydrocarbon reserves and covers the most of West Siberia territory. In most cases its productivity is assosiated with the presence of permeable layers ensuring natural inflow of oil. Both global and Russian experience in development of unconventional reserves has shown that the stimulation process is the key method of introducing previously inaccessible reserves into development.

It should be noted that current level of multi-stage fracturing technology development does not provide the cumulative production required for payback of a drilled well. In the near future fracturing technology development should be focused on the increase of stimulated reservoir volume by creating artificial fracture network in relatively ductile source rocks.

The authors believe that Bazhen wells productivity calculations should consider not only geological, but first of all technological uncertainties and risks. This work shows a shift from the deterministic 2D forecast of the well production profile to the probabilistic 3D forecast making it possible to take into consideration a significant range of technological uncertainties related to development of source rock deposits in the Bazhenov formation.

Meeting the technological challenges, such as creating high density fracture network and reduction of the well cost, is the key target for projects of Bazhenov formation investigation.
High-Frequency LWD Electromagnetic Measurements Applied to Studying Macroanisotropic Properties of Thin-Bedded Sedimentary Deposits
Authors: Nikitenko M. N. , Glinskikh V. N. , Eremin V. N. , Epov M. I.
Published: October 2016

This paper discusses the development of interpretation base in case of high-frequency electromagnetic logging-while-drilling (LWD) data acquired from deviated and horizontal boreholes. The aim of the work is to analyze the capability of revealing thinly bedded intervals as potentially hazardous when drlilling highly deviated boreholes and conducting multistage hydraulic fracturing. The main challenges are related to the numerical simulation and inversion of electromagnetic LWD data for determining the electrical macroanisotropy of thinly bedded sequences.

To tackle the problem of detecting such intervals, characterized by the alternation of beds with various lithological compositions, we apply high-frequency electromagnetic LWD. The problem is possible to solve since the interlayers are characterized by different electric resistivities, the high-frequency sondes have fine resolution, and the developed simulation algorithms are highly accurate and effective. The basic model we consider is that of a horizontally layered anisotropic medium, taking into account the tool deviation relative to horizontal boundaries. We perform the numerical analysis of electromagnetic signals in typical models of macroanisotropic layers, as well as the numerical interpretation of practical LWD data from highly deviated boreholes of Western Siberia.

For directional drilling of horizontal boreholes with complex trajectories in thinly bedded intervals and for studying their electric macroanisotropy we have developed highly effective algorithms and software for the simulation, processing and interpretation of high-frequency electromagnetic logs recorded during drilling. To substantiate the possibility of estimation of the electrical macroanisotropy factor we have conducted the numerical simulation and analysis of the electromagnetic signals and their sensitivity functions in typical geoelectric models. In such a way, it is shown that the phase shift and attenuation in a horizontal interval penetrated electrically macroanisotropic section have sufficient sensitivity to the vertical resistivity of a formation, as well as to the locations of its top and bottom. This fact enables revealing thinly layered intervals during drilling. As a result, we have shown that the values of the geoelectric parameters (vertical and horizontal resistivities, positions of boundaries) are determined with high accuracy.

The scientific and practical significance of the work at hand is determined by the necessity of improving the safety of construction of deviated and horizontal boreholes and conducting multistage hydraulic fracturing, as well as the development of interpretation base for high-frequency electromagnetic LWD.
Application of AFR Sensor for the Purpose of Integrated Interpretation of High-Resolution Electrical Images and Geosteering of Horizontal Wells in Carbonate Reservoirs
Authors: Shpilman Evgeniya Sergeevna , Butenkova Anastasia Sergeevna , Kirpischikov Yuriy Vladislavovich , Zaboev Konstantin Olegovich
Published: October 2016

Horizontal wells were drilled for the first time in the survey area. The target formation is mainly composed of dolomites and irregularly dolomitized limestones. Voids in reservoirs include pores, vugs, and fractures. Effective capacity of the reservoir is determined by intergranular and vuggy porosity, while fracturing provides for reservoir properties. In view of insufficient knowledge of the operation area, a decision was made regarding penetration of the target formation throughout the entire thickness and identification of a zone with the best reservoir properties for further positioning of a horizontal borehole in this zone. An azimuthal focused resistivity (AFR) sensor of 4 3/4 in. was used during drilling. This sensor generates high-resolution electrical images of borehole walls, measures at-bit resistivity, and provides laterolog data. This paper describes the process and procedures for interpretation of geological and geophysical logging while drilling (LWD) data for building a petrophysical model of the reservoir, determination of porosity and permeability, calculation of fluid, fracture and mineralogical models, and identification of structural geometry of rock bedding. Electrical microimages were used to update geological and petrophysical reservoir models.