bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Temperature Field in the Formations by Hydraulic Fracture
Authors: Valiullin R. , Sharafutdinov R. , Ramazanov A. , Sharipov A. , Nizaeva I. , Badetz C. , Jaffrezic V.
Published: October 2017

Today, number of fracturing operations (fracturing) is increasing every year due to the development of low-permeability formations classified as hard-to-recover formations. The actual task is to determine parameters of fracture obtained in order to confirm the planned design, toimprove technology of fracturing fluid injection and proppant, toprevent premature watering and to frac non-target reservoirs. The fracture properties do not remain constant over time: under the influence of rock pressure, the proppant is compressed and destroyedandduring production part of proppant is washed out of fracture. Therefore, it is also important to monitor the change of fracture parameters over time.

Technologies are known to determine the fracture parameters [16, 17]. Anywork aiming at developping accessible technologies with high level informativeness is relevant: Temperature transient ananlysis is one of them.

Thermometry method is actively used in borehole geophysics. Unlike well tests (hydrodynamic studies), thermometry allows individual characteristics of each formation (inflow intervals) to be obtained in case of a multi-layer system.

Thefield results and theoretical studies have shown that temperature is sensitive to the presence of fracture: by means of temperature measurements in the well, the fracture height is determined reliably now. An important task is to determine thefracture geometry - length, width, azimuth direction. The complexity of this problem solutionis due tothe fact that thermohydrodynamic processes in reservoir – fracture systemhas not been yet sufficiently studied. Therefore, theoretical studies are needed to study the effect of fracture on temperature and pressure fields in reservoir. In the presented work the problem is solved with help of mathematical modeling:analytical solutions are obtained and numerical model is developed. The results of multivariate calculations and their comparison with field data of temperature recovery in wellbore are presented.
A New Approach to Test Production of Exploration Wells in the Territory of Eastern Siberia
Authors: Dadakin N. M. , Rymarenko K. V. , Nukhayev M. T. , Lavrov V. V.
Published: October 2017

Trial operation of prospecting and exploratory wells tends to be affected by the remoteness of the field from the main transportation routes, weakly developed industry, energy, and transport infrastructures, the lack of a well surface facility system and the oil preparation system to start production.

This report describes an example of a trial operation of a remote prospecting well that includes all pre-development works, a surveying program that allows obtaining the maximum information about the productive horizon in a short time. It also provides recommendations for the adoption of technologies for pilot operation based on the block-modular production complexes for the early production launch of exploratory and prospecting wells or individual sections of the field, and technologies for continuous well monitoring and management, including bottomhole pressure gauges, a distributed temperature sensing system and a system for real-time data receiving and transmitting to the subsoil user.

This approach allows us not only talking about early production, but also solving a number of tasks, e.g. petroleum evaluation, extraction capacities of a deposit, drainage area, formation pressure evaluation, optimal well operation mode identification, gas/oil ratio change estimates, water cut, and other geological tasks. The report also describes the key drawbacks of applied trial operation methods and technologies as compared to the proposed technologies.
Production Logging in Horizontal Wells without Well Intervention
Authors: Ovchinnikov Kirill , Gurianov Andrey , Buzin Pavel , Katashov Aleksander , Dubnov Oleg , Agishev Ruslan
Published: October 2017

For the last decade, the global trend in the oilfield industry is to improve the oil and gas production by drilling as well as by completing horizontal wells and later on, improving the process using multistage fracturing. Though the number of horizontal wells is rapidly increasing, the production of hydrocarbons is not always up to the designed volume. In this regard, acquiring the knowledge on the performance of producing intervals is an important task for operating companies to fully optimize the productivity and maximize the recovery as well. Production logging solutions proved to be efficient in vertical wells, however, encountered various challenges in horizontal laterals as the logged section is often more than 20 times longer compared to vertical wells [1]. Common factors that complicate the production logging are layered flow of formation fluid, deviation and accessibility of wellbore, and changes in fluid velocity moving past or through the tools. Direct transfer of production logging technology and interpretation algorithms from vertical wells to horizontal wells leads to erroneous conclusions about the well performance [2]. Moreover, the quality of well completion and reservoir management decisions for production wells largely depends on the production logging data such as mechanical flowmeter and fluid capacitance surveys.

Until recently, there is no alternative to wireline downhole tools being used to evaluate the placement of fracturing proppant or acids, production rate and zonal water breakthrough. In practice, well intervention in horizontal wells requires implication of coiled tubing or tractor services to deploy logging tools downhole. The success of well intervention depends on several factors and among of these are as follows: well accessibility, completion IDs and length of the horizontal lateral, etc. There are also key aspects to be considered such as the significant cost of well intervention and the availability of wireline and coiled tubing equipment. This article provides an overview of one of the alternative methods of production logging in horizontal wells which doesn't require well intervention using PLT tools, Coiled Tubing or Tractor services. This method employs tracer technology of quantum dot markers placed in the reservoir during stimulation. The method also allows reducing the cost as well as the complexity of acquiring downhole data. Unlike the conventional PLT, the technology described below can provide production logs on demand during one year after well stimulation.
Permeability Anisotropy in the Thinly-Bedded Pokurskaya Formation from Advanced Wireline Logs and Formation Testers
Authors: Zagrebelnyy E. V. , Glushcenko N. A. , Martynov M. E. , Tsiklakov A. M. , Blinov V. A. , Weinheber P. , Karpekin Y. A. , Ezersky D. M. , Bugakova Y. S.
Published: October 2017

Field development planning requires a proper understanding of layer permeability in order to predict production rates. Experience with horizontal production wells in the Pokurskaya formation of the Messoyakhskoye field showed systematically lower flow rates from the B sands versus the C layers even though their petrophysical properties appear similar. It was proposed that differing permeability anisotropy between the layers might be the cause and an upcoming well in the field offered the ability to test this hypothesis. A logging program that included Vertical Interference Tests (VIT) with a Wireline Formation Tester tool (WFT) and advanced petrophysical logs, 3D resistivity, NMR and dielectric scanner was run to estimate the the kv/kh ratio pointwise with VIT and extrapolate these measurements through the entire section.

VIT tests were done at several depths with a dual-packer for the fluid withdrawing and a pressure probe for pressure monitoring. Estimated anisotropy coefficient varies mainly from 0.02 to 0.07 but with both higher and significantly lower values at some depths, which indicate extremely limited connectivity in some intervals. In general, the kv/kh ratio is significantly lower in the upper interval of the PK1-3 formation versus its lower interval. The triaxial induction logging shown the anisotropy of the reservoir electrical properties (Rv> Rh), caused by thin interbedding of the sandy fraction rocks with the interlayers of clays and siltstones, which are several times lower than the resolution of standard logging methods. Similarly, interlayering of thin sand and silty rock types, which have different absolute permeabilities, causes anisotropy of the formation permeability. It is possible to estimate the permeability of the macroanisotropic formation along and across the bedding knowing the water-retaining capacity as well as the laminated sand fraction coefficient. The VIT and the logging results are consistent enough. The VIT test results are the reference measurements while the 3D induction logging results are used for interpolation and extrapolation of these direct measurements through the entire interval and in wells without VIT tests including horizontal wells.

The subsequent analysis showed a significant anisotropy of permeability in the Pokurskaya formation, which varies along the interval of the formation and, probably, laterally. This must be taken into account when calculating the flow rates of the well. The complex of studies makes it possible to perform an express estimation of the permeability anisotropy in the pilot wells in order to select the optimal interval for horizontal wells landing.
Natural Fractured Reservoirs Characteristics Estimation Based on Production Data using Simplified Correlation. Examples from Russia
Authors: Syrtlanov V , Kovaleva E. , Aleev A.
Published: October 2017

This paper suggests the simplified correlation ratios, that are an approximate analytical representation of exact numerical solution, for evaluation of fracturing characteristics of the fractured reservoirs with the use of decline curves. Formalization and automation methods are suggested for finding fractured reservoir approximate parameters and range of uncertainty under the Warren-Root model.
Investigation of a Pressure Barrier at OWC and its Effect on Waterflood
Authors: Stasyuk Bogdan , Camerlo Virginia
Published: October 2017

Understanding the pressure history of a field brings valuable information that could affect decisions regarding future field development. Sequential formation tests (RFT, MDT, XPT, RDT, Stethoscope and other tools) done while drilling a new well can help describe the dynamics of pressure conditions in the reservoir. In the early life of a field, sequential formation tests describe initial reservoir conditions (gradients, contacts, compartments). Sequential formation tests obtained in wells drilled after the start of production can help the understanding of communication within the field (injector to producer; producer to producer; aquifer/peripheral injection effect; barriers; and connectivity across faults).

Historical sequential formation tests performed on a nearly 30-year-old oil and gas field in West Africa were analyzed and used to identify, confirm and describe a significant pressure barrier at the OOWC (e.g. "tar mat" that gives up to 1000psi difference across contact). Systemizing sequential formation test data by time and area allowed estimation of the pressure barrier extent and its effect on communication between peripheral injectors and the oil zone. Pressure breaks were then plotted on well logs and located in conventional core, where possible, to determine a possible geologic explanation for the pressure barriers.

Smaller pressure barriers are attributed to lithologic changes associated with either facies changes or secondary dolomitization. However, the largest pressure barrier appears across the OOWC. Visual inspection of 5 conventional cores across the field, confirms the presence of 6-9 ft. of solid hydrocarbons, interpreted to be a "tar mat," across the OOWC, except in the northwest portion of the field. Core analysis of samples within the tar mat zone shows unaltered, high permeability (as per testing procedure all cores were cleaned with solvent before testing). The pressure barrier is likely due to the presence of soluble, but highly viscous, long chain hydrocarbons that effectively create a no flow barrier across the OOWC.

Wells with a long period of water free production correspond to areas with a predictable strong pressure barrier at the OOWC. Conversely, wells located in an area with a poorly defined barrier at the OOWC had quicker water break-through. Thus, we conclude that peripheral water injection perforated below the OOWC is less effective in areas where the tar mat is present.
Oil Production Enhancement Operations Recommendations by Well-Testing and Decline Analyze
Authors: Lazutkin D. , Gulyaev D. , Morozovskiy N.
Published: October 2017

In the paper, it is shown that the results of the interpretation of measurements of permanent reference gages on the electric submersible pump (ESP) together with the data on the change in the historical production rate of the wells allow carrying out the justification and support of the oil production enhancement operations and also the analysis of the efficiency of the oil production enhancement operations performed by estimating the current skin-factor of the wells and reservoir pressure. In particular, wells have been identified in which worsening of the skin-factor in time is observed. For them, the optimal time for performing repeated well interventions was chosen to improve the skin-factor and increase production from the wells.

Separate results of the work are represented by an express method for selecting the optimal time for transferring production wells to injectors for pressure maintains to optimize the production of a section of the oilfield based on the telemetry gages on the ESP. At the same time, the forecasts were made on the basis of express 2D models in the software "Topaze", which significantly increases the speed of work execution compared to full 3D modeling, and the accuracy of forecasts remains quite high.

The paper shows that the results of the historical flow rate of wells and the telemetry of pumps are a good informational basis for the application of a new method for analyzing cross-wellbore interference – multi-well deconvolution (MWD).

Thus, without a loss of production, a analysis of the results of a production decline was carried out on the basis of the algorithms for interpretation of the well test and recommendations of production enhancement operations were justified to increase production.
Well Index Calculation for Arbitrary Trajectory, Perforation, Hydraulic Fracturing and Geological Properties
Authors: Bakhty N. S. , Bembel G. S.
Published: October 2017

Calculation of inflow to a well and hydraulic fracture in the reservoir simulation is presented in this paper. An algorithm of well index (WI) calculation based on a new numerical-analytical solution is proposed. In simple cases, the proposed method is identical to the classic Peaceman's formula, and surpasses it in accuracy in more complicated cases, taking into account different properties of the perforated grid block and its neighbors, imperfect perforation, location of a well in a grid block, impermeable boundaries next to a well.

Acquired WI coefficients were compared with analytical solutions for imperfect well, five-spot pattern, inflow to infinite and semi-infinite hydraulic fractures and also for the problem presented in [1], in which production rates before and after fracturing are compared. It is shown, that in these cases presented algorithm provides a lesser deviation from the analytical results than Peaceman's formula. Therefore developed algorithm is proved to be more accurate and applicable in more general cases.

Additionally, to demonstrate the effect of using the WI coefficients acquired with different formulas in reservoir simulation both methods were applied to comparison project SPE1 [2], in which it is necessary to account for impermeable boundaries and imperfect perforation. A significant difference of simulation results can be seen in the oil rate of the producing well, gas oil ratio, and pressures.
The Concept of the Complex Carbonate Reservoir Saturation with the Variable Wettability
Authors: Kanevskaya R. D , Budkin K. D , Korobkin S. V , Lubimova O. V , Pimenov A. A. , Isakova T. G. , Markova A. Yu.
Published: October 2017

Rock wettability and its transformation in the process of formation and development of oil deposits is a crucial factor influencing fluid content and many aspects of reservoir performance, particulary in waterflooding and enhanced oil recovery techniques. The saturation concept for the complex carbonate reservoir with the variable wettability is presented. It is shown that rock wettability can significantly affect large-scale fluid distribution processes in the oil-saturated reservoir.

The analysis of the geophysical characteristics of the cross section allowed to separate three geological units with significantly different values of the electrical resistivity. By means of joint analysis of core examination and geophysical well logging it is demonstrated that zones of the «low-resistivity» geological unit are chiefly characterized by hydrophobik type of rock wettability, while zones of the «high-resistivity» unit are typically described by hydrophilic type of rock wettability. The predominantly hydrophobic unit lies between two hydrophilic and less permeable units. Oil saturation model is designed with the assistance of field and core data based on the capillary-gravitaty equilibrium concept taking into account variable rock wettability. The results of the relative permeability experiments and data on the initial water cut of well production are also used to identify initial saturation distribution in reservoir.

In the predominantly hydrophobic unit, the transition zone is insignificant and partially below the free-water level. There is water alone in the hydrophilic units at these depths. At depths corresponding to the transition zones of the hydrophilic units, there is an area of high oil saturation in the predominantly hydrophobic unit.

The presented approach to the creating of the saturation model enabled to consider previously ignored factors (the electrical resistivity of the geological units, the presence of bridges between them) that affect the efficiency of the reservoir pressure maintenance system and recovery of reserves. The identification of the thick lower unit with high water saturation made it possible to determine the source of water encroachment and explain the nature of water encroachment of production wells.

The proposed concept of the complex carbonate reservoir saturation with the variable wettability allowed to connect well log, core and field data to a single consistent model.
Deformation Processes in Reservoir Engineering of the Limestone and their Influence on the Engineering Calculations
Authors: Belanozhka Aliaksei
Published: October 2017

In the process of developing hydrocarbon deposits in terms of changing baric conditions, not only formation fluids are transformed, but also the rock itself, which possesses elastic properties and is capable of deforming. The article presents approaches to identifying, analyzing and interpreting the manifestations of deformation processes in the development of hydrocarbon deposits in the limestones of the Republic of Belarus. The article presents the methods for the justification and calculation of the values of critical pressures at which the deformation processes in the beds or formations appear.

The main methods by which critical pressure values were determined were:

a method for assessing of the critical bottomhole pressure based on the interpretation of well-test (change in productivity during the removal of PC); a method for determining the critical reservoir pressure, taking into account the construction of specific selection curves for closed deposits; a direct laboratory method for determining critical effective pressures, which significantly reduces permeability, which is associated with deformation processes (studies should be carried out at a constant sample crushing pressure and a variable pore pressure).

Deformation processes significantly (by several orders of magnitude) reduce permeability and are not reversible. In this case, the presence of these processes is noted both in the test of individual wells, and in the process of developing the whole deposit. It is noted that according to the results of studies in 63% of cases, the decrease PI with increasing depression is associated with deformations in the bottomhole zone.

Knowledge of these pressure values allows the correct application of the material balance method to assess hydrocarbon reserves and adapt hydrodynamic reservoir models, to plan efficiently and rationally the implementation and modernization of reservoir pressure maintenance systems and also to predict the change depending on the pressure of the productive characteristics of the wells.

The new thing of this work is in identification and systematizing cases of deformation processes in the limestones of the Republic of Belarus, to justify simple methods for understanding and implementing methods for determining the critical values of pressures at which deformation of collectors occurs. A new method for estimating the reservoir type by the capacitive component is proposed, which evaluates the compressibility of the capacitance during the deformation process, as well as the capacitance volume susceptible to deformation.
Effect of Saturation Alteration on Wellbore Stability during WAG Injection
Authors: Bataee M. , Hamdi Z. , Irawan S. , Ashena R. , Ghassemi M. F.
Published: October 2017

Nowadays, enhanced oil recovery (EOR) injection methods are very popular due to its simplicity and effectiveness in increasing the recovery. The water alternating gas (WAG) injection method shows higher sweep efficiency and recovery than the one-phase fluid injection. However, extremely high injection pressure will fracture the wellbore. Moreover, the saturation alteration changes the rock mechanical properties and stress values around the wellbore. The purpose of this study is to study the effects of saturation alteration on wellbore stability. This study has implemented with modelling procedure regarding the obtained experimental results from modified triaxial testing device. The core holder for this device is exclusively designed to prepare the favourable data of rock mechanical properties for different saturation schemes. The parameters of pressures, saturations, and stresses were obtained for the WAG flow using numerical modelling. For the pressures and saturation values, finite difference method (FDM) was used and to solve the rock stress values, finite volume method (FVM) was applied. According to experimental results, the recorded maximum axial stress was higher than the water and oil saturated cases (48.19 respected to 42.33 and 41.28). It indicates that the formation was more resistive to failuire for gas injection. However, after modelling, it was concludedthat the formation was more unstable in the gas injection case because of higher pressure transient. Therefore, the possibility of wellbore failure was higher during gas injection rather than water injection.
Operative Localization Technique of Current Mobile Oil Reserves for Mature Reservoirs Based on Material Balance
Authors: Aleev A. , Syrtlanov V. , Kovalyova Ye.
Published: October 2017

This paper proposes real-time evaluation of distribution of residual oil reserves in mature oil fields developed with water flooding system and localization of zones with higher density of reserves for the selection of areas/wells for well intervention and for optimization of water flooding system. Examples of application of this procedure on the facilities and oil fields in West Siberia are provided below.
Foam Acid Treatment - The Key to Stimulation of Carbonate Reservoirs in Depleted Oil Fields of the Samara Region
Authors: Letichevskiy Alexander , Nikitin Alexey , Parfenov Alexey , Makarenko Vitaliy , Lavrov Ilya , Rukan Gleb , Ovsyannikov Dmitry , Nuriakhmetov Ruslan , Gromovenko Alexander
Published: October 2017

Oil fields of the Samara region are at a late stage of development, which is reflected in declining of their production level and rapid growth of watercut. About 30% of the region's industrial hydrocarbon reserves are concentrated in carbonate reservoirs, which require stimulation. Low reservoir pressure, heterogeneity of the formation and the proximity of water-saturated interlayers significantly complicate the task of efficient field development and exploitation. In such conditions, the use of traditional methods for treating the bottomhole zone of carbonate rocks does not bring the expected results, and the worsening stock of exploited objects makes it necessary to look for new promising methods for increasing oil recovery.

Carbonate reservoirs stimulation in the Samara region is carried out using a spectrum of various technologies of hydrochloric acid treatments, both to extend the life of old wells and to efficiently start new wells after drilling. In order to increase the effect from the performed hydrochloric acid treatments in 2016, the foam diverting technology was applied in the framework of pilot projects. This technology uses a stable non-damaging agent to form a nitrogen foam of 65% quality at the bottom hole. After the treatment, the foam breaks down into liquid and nitrogen, which in turn improves well flow back and helps to restore the natural flow.

Despite the high degree of field development, the use of foam made it possible to achieve a 69% greater initial well productivity index than other methods. At the same time, the starting production rate of wells increased almost 2 times. The technology also allowed to reduce the specific volume of injected acid per meter of oil saturation by 25% without compromising the efficiency of the treatment, what has key importance from the point of view of economic feasibility. Based on the results of the performed pilot operations, nitrogen-foam acid treatments were included in the regular program of wells stimulation.
Reservoir Surveillance Informative Value on Brown Field
Authors: Bogatyreva I. , Metelkina N. , Mustafin R.
Published: October 2017

Matured oil field development poses different set of problems to be solved. As the geological structure is understood by this time, the most important tasks for reservoir surveillance becomes localization of residual reserves and the identification of promising zones for the production enhancement. Considering that the effect of potential geological and technical measures in the matured oilfield will not be that significant, the monitoring methods should be cost effective and at the same time deliver sufficient information. In our case, the main surveillance techniques were measurements of reservoir pressure, joint measurements of bottomhole pressure and well production rate, and targeted well tests. In addition, production logging was widely used to build the inflow and injection profile, identify sources of watering, and commingled production control. Authors implemented technology to assess the current skin factors without stopping such wells for special tests, only on the basis of the results of joint measurements of bottomhole pressure and well production.

The main low-cost method to remove the colmatation of the bottomhole zone was re-perforation, significantly increasing the flow rate of oil wells. In general, a comprehensive production analysis was carried out, including recovery evaluation by the zones of the reservoir and an areal analysis based on facies heterogeneity information. It was possible to achieve stabilization and even an increase in oil production after the suggested well intervention program was implemented in the field.
Mechanism Study on Foam Flooding for Daqing Reservoirs After Polymer Flooding
Authors: Qingfeng Hou , Donghong Guo , Youyi Zhu , Jian Ouyang , Zhe Wang
Published: October 2017

Polymer flooding has been carried out widely in Daqing oilfield. The average oil recovery was 53% and the water cut was more than 90% after polymer flooding. The remaining oil was highly dispersed in distributary channels. New EOR techniques with better profile control ability than polymer flooding need to be applied. The mechanism on foam flooding after polymer flooding was studied based on core flood experiments and X-ray computed technology (CT) in this paper.

The EOR effect for foam flooding after polymer flooding was evaluated employing both 2D and 3D core flood experiments. Artificial three-layer positive rhythm sand-packed cores were employed. The length, width and height for 2D cores were 28.0 cm, 4.5 cm and 4.5 cm, respectively. And the length, width and height for 3D cores were 50.0 cm, 50.0 cm and 20.0 cm, respectively. 1/4 five-spot pattern was employed for 3D core flood experiments. Particularly, the oil saturation profile was monitored with CT during whole 2D flooding process. The fluid distribution and sweep efficiency during the flood were described based on CT images.

EOR effect evaluation with 2 D and 3D models indicated that foam flooding could contribute 11.7% and 16.1% OOIP recovery even if the recovery after polymer flooding was more than 50%, respectively. The obvious increasing in injection pressure during the foam flooding indicated that foam fluid had stronger profile control ability than polymer. The distribution of residual oil in three-layer cores during the flooding was monitored. Firstly, the injected water mainly fingered through high-permeability zones during water flooding. The residual oil after water flooding was mainly distributed in the middle and low permeability layers. Next, polymer flooding could subsequently increase sweep efficiency by the deceasing in mobility ratio. The residual oil after polymer flooding was highly dispersed. In the end, foam could be employed to further recover considerable oil after polymer flooding. Pore blocking effect might play a great role in EOR mechanism for foam flooding. The evolution of fluid distribution was demonstrated clearly during foam propagation. The difference among the CT value of three phases (eliminating the contribution of the rock) was contributed to the addition of sodium iodide in aqueous phase.

Core flooding experiments monitored with CT proved that foam flooding could become a further EOR method for Daqing reservoirs after polymer flooding. Foam demonstrated better pore blocking ability than polymer within middle and high permeability layers. Foam could effectively block thief zone for highly heterogeneous reservoirs and increase sweep efficiency significantly after polymer flooding. It might become a promising EOR method for Daqing reservoirs after polymer flooding due to its profile control ability.
Additional Appraisal Program Optimisation with the Value of Information Aproach
Authors: Asmandiyarov R. N. , Onegov A. V. , Nigamatov S. A. , Vashevnik A. M. , Goncharov A. S. , Mityaev M. Y. , Sizykh A. V. , Fedorov E. G.
Published: October 2017

The work is aimed at the optimum program of additional appraisal for the object with high investment risk level. The investigated object is related to non-structural oil reserves and stands along from the infrastructure nodes with exploitation wells. Therefore, the work consist of the probability based reserves estimation for the all possible project ways and maximum effective way choice with the save of economically profitability.

Optimization program is concerned as to the project realization way as to the additional appraisal program. In the case of additional appraisal program three pilot wells drilling time and expenditures were considered. All three wells planed and calculated with standard well logging tools. As an alternative the exploration wells re-entry were considered. Facies distribution features and petrophysical properties were examined as uncertainties. The main point was haw they influence on the exploitation method. For this point of view, approximately 3000 realizations with different combinations of petrophysical properties, sedimentation facies geometrical sizes and type of exploitation were calculated. Result of optimization shoed that the optimum way is connected with consistent exploration wells re-entry, in spite of possible long term operations because of possible troubles. These optimization calculations give decision tree with probability and parameters values for every decision point for the further operations.

Geologist, reservoir engineers or economists who deals with the high investment risk projects where geology, exploitation and infrastructure uncertainties take place may use similar approach.
Accounting of Stationary Liquid Unloading Criteria in Simulation Model for Downhole Equipment and Regime Optimization and Prolongation of Gas Wells Operation
Authors: Maksimovskiy I. V. , Minikaev F. M. , Mangushev R. R. , Mingazov A. A.
Published: October 2017

The problem of liquid loading in well bores for a great number of gas wells is considered. This problem is observed in the framework of production calculations using the simulation model. It is determined that groundless assignment of wells decommissioning criteria leads to significant errors in the assessment of cumulative gas production and well stop flowing time.

Using the results of data after water breakthrough and wells stop flowing, the liquid unloading criteria in the gas wells were formed. The stationary unloading criteria depend on elevator equipment construction and critical production rates. They were evaluated, based on agreement procedure of calculated and actual liquid unloading parameters, by means of hydraulic well models. At the same time, applicability conditions for this technique were determined.

In this paper, simple and sufficiently reliable methods and algorithms are proposed. They are used for accounting stationary liquid unloading criteria which are needed for right well decommission time. Moreover, the criteria make it possible to improve the predictive potential of the integrated field models and to arrange the operations for prolongation of well life. For instance, technological regime optimization and running additional tubings of smaller diameter made from coiled tubing (velocity strings) can be proposed.
Carbonate Core: Research Features, Complexities, Prospects
Authors: Kovalev K. M. , Grishin P. A. , Gabsia B. K. , Kurochkin A. D. , Kolesnikov M. V. , Levchenko A. C.
Published: October 2017

Carbonate cores require special approaches and techniques to obtain appropriate data from core analysis due to their complex nature.

This paper discusses various challenges faced and presents an integrated approach to the study of carbonate cores.

Comparative analysis of the results obtained from standard and special carbonate rocks core analyses are presented. While carbonate rocks operations key difficulties encountered from core acquisition to long term storage are highlighted.
Mosaic Hydrophobization of the Surface of Organic-Mineral Matrix from Rocks of Bazhenov Formation
Authors: Bogdanovich N. N. , Borisenko S. A. , Kozlova E. V. , Spasennykh M. Yu , Rudakovskaya S. Yu.
Published: October 2017

By data of laboratory studies of mineral composition, analytical estimation of hydrophobicity of rocks by adsorption and NMR methods, pyrolytic studies of organic matter of Bazhenov Formation rocks, dependencies were determined between organo-mineral matrix composition and wettability of the solid surface. Influence of secondary effects on changes in hydrophobization of rocks were revealed. For carbonate minerals, catagenetic substitution of calcium cations for magnesium and iron results in polar changes in attitude of the rock to water fluids. Evaluation was made of the proportion of generated autochthonous and parautochthonous hydrocarbons of the oil series, heteroatomic compounds and kerogen in the overall balance of the organic component of the Bazhenov rocks, and an attempt was made to establish dependency of these proportions versus measured hydrophobicity of rocks. After dissolution of the light fraction of petroleum hydrocarbons, a decrease in combustion rate of the residual organic matter in air flow was observed for hydrophobic varieties. There are no obvious dependencies of surface hydrophobization versus mineral composition and organic matter of a rock in the ‘rock-water-oil’ system.
Investigation of Relationships of Geomechanic Properties of Layered Rocks Depending on Hydrostatical Pressure
Authors: Aliev Mekhrali , Baiburova Minsariya , Ibragimov Ildar , Ismagilova Zulfiya , Lutfullin Azat
Published: October 2017

The paper presents the investigation results to determine the mechanical characteristics of multilayered shales. The results are based on shearing and breaking off tests along certain planes of specimen. The modified Mohr-Coulomb criterion including an alternating angle of internal friction and variable cohesion is used as a strength criterion. Both the angle of internal friction and cohesion are considered as parameters depending on orientation. To determine the transverse strength at different orientations three rock test designs and two equations are proposed. In the case of breaking off the rock another strength criterion proposed by G.Geniev is used. It was investigated by authors of the paper for various anisotropic materials. Here strength characteristics are determined via calculations. They are based on results of two simplified tests (along and across the foliation), that is simple stretching test or the so-called "Brazilian test". Examples of calculations of the rock strength characteristics using the proposed models are given and considered in a critical manner.
Laboratory Modeling of Residual Oil Mobilization in Flooded Reservoirs
Authors: Melekhin Sergey V. , Mikhailov Nikolay N. , Russian Gubkin
Published: October 2017

Currently more and more oil fields reach their final development stage, characterized by increased water cut and decline of the oil production flow. Having said that, the residual oil saturation is still high, which means a presence of significant residual recoverable reserves within the flooded fields. Efficient recovery of these reserves is impossible without a prior analysis of their structure and location within the reservoirs.

Modern approaches to evaluation of residual oil saturation and displacement efficiency are based on determination of only one parameter and its relationship with porosity and permeability. With these methods residual oil saturation values are simulated on the bases of unlimited flow and unified predetermined filtering parameters, which correspond to the reservoir mean values. The methods are also based on maximum injection rates, ten times higher than the average injection rate values. As a result of reservoir development simulation, flooded zones will have the lowest residual oil saturation, while the residual oil saturation will be concentrated within the unflooded areas.

An experimental research was carried out to assess the impact of displacement parameters on oil displacement efficiency. A special test procedure was developed, which involves special core preparation so that the samples retain their surface properties. The obtained data allow for a conclusion, that there is a relationship between capillary and hydrodynamic forces (capillary number) and rate of oil recovery from the core pore space. Conditionally mobile residual oil saturation values and their relationship with the rock surface properties were determined.
Spectral Inversion Methods and its Application for Wave Field Analysis
Authors: Butorin A. V. , Krasnov F. V.
Published: October 2017

The article describes different methods of spectral decomposition on model seismic traces. The main methods are considered: windowed Fourier transform, continuous wavelet transform and algorithms of spectral inversion.

As a result the spectral inversion methods based on the approximation of an input trace in a library of wavelets with the help of Lp-regularization, provide a much more accurate spectral representation of the signal.

Several possible ways of geological interpretation using spectral inversion are shown in the article as a practical result. Considered approaches could be divided into custom – related to the all types of spectral inversion and specific – forwarded to specific features of spectral inversion results.
Growing Legumes in Orchard Alleys as an Internal Nitrogen Source
Authors: Granatstein David , Davenport Joan R. , Kirby Elizabeth
Published: October 2017

The drive alley in modern apple (Malus ×domestica Bork.) orchards often receives enough light to grow plants other than the typical perennial grass cover. By planting leguminous species in this area, it is possible to produce a portion of the nitrogen needs of the orchard by mowing the vegetation and blowing it onto the tree row where it mineralizes and releases available N over the tree roots. Four perennial legume species [alfalfa (Medicago sativa L.), ladino white clover (Trifolium repens L.), birdsfoot trefoil (Lotus corniculatus L.), kura clover (Trifolium ambiguum L.)] were compared with the resident grass cover crop in a mature apple orchard. All legumes were direct-seeded into the alley to avoid any soil disturbance and were successfully established. Legume biomass and tissue N were monitored, along with biweekly monitoring of tree row soil nitrogen with both soil sampling and ion exchange resins using Plant Root Simulator® probes. Four mowings of alfalfa contained ≈43 kg total N/ha that was added to the tree row during the second season (2009), with a dry matter C:N of 10.8. Economically, legume nitrogen appears to be less expensive than other sources of organic N and may be cost competitive with synthetic fertilizer N when prices are high.
Effect of Rice Hull Mulch on Nutrient Concentration of Fertilized Irrigation Water
Authors: Altland James E. , Boldt Jennifer K.
Published: October 2017

Parboiled rice hulls (PBH) have been shown to be an effective mulch for weed control in container crops. As with other mulch products, there is concern that PBH mulch would interfere with nutrient delivery to the crop. The objective of this research was to determine the effect of PBH mulch on nutrient concentration of fertilized irrigation water as it passes through the mulch layer, and the subsequent effect on growth and nutrition of container-grown sunflower (Helianthus annuus). Parboiled rice hull mulch was placed in Buchner funnels at a depth of 0, 0.63, 1.25, or 2.50 cm. Irrigation was applied with a water-soluble fertilizer (20N–4.4P–16.6K) injected at a concentration of 100 mg·L−1 N. Filtrates were collected after passing through the PBH in the Buchner funnels and analyzed for nutrient concentration. In a separate study, sunflower in no. 3 containers were mulched with the same depths of PBH and irrigated with water fertilized similar to that in the funnel experiment. Parboiled rice hull mulch caused a temporary and slight decrease in NO3− and NH4+ concentration. Phosphate and K+ concentrations generally increased with each irrigation event. Calcium and Mg exhibited an inverse relationship where the PBH mulch decreased Ca and increased Mg concentrations in the filtrates. Despite these measured differences in the chemical properties of water passing through the mulch layer, there were no measurable differences in sunflower growth or physical appearance, and only minor and inconsequential differences in plant nutrient status. Rice hull mulches are likely to have very minor effects on container crop nutrition with no adverse effect on plant growth over a 6 week production cycle as used in this experiment.
A Method for Quantifying Whole-tree Pruning Severity in Mature Tall Spindle Apple Plantings
Authors: Schupp James R. , Winzeler H. Edwin , Kon Thomas M. , Marini Richard P. , Baugher Tara A. , Kime Lynn F. , Schupp Melanie A.
Published: October 2017

Pruning is the cutting away of vegetation from plants for horticultural purposes. Pruning is known to reduce apple tree size, increase fruit size and quality, and decrease yield. Methods for studying the effects of varying degrees of severity of pruning on a whole-tree basis have used qualitative descriptions of treatments rather than repeatable whole-tree quantitative metrics. In this study, we introduce a pruning severity index calculated from the sum of the cross-sectional area of all branches on a tree at 2.5 cm from their union to the central leader divided by the cross-sectional area of its central leader at 30 cm from the graft union. This limb to trunk ratio (LTR) was then modified by successively removing the largest branches of ‘Buckeye Gala’ to achieve six severity levels ranging from LTR 0.5 to LTR 1.75, with lower values representing more extreme pruning with less whole-tree limb area relative to trunk area. Pruning treatments were applied for three consecutive years and tree growth and cropping responses were observed for the first 2 years. With increasing pruning severity the following characteristics increased after seasonal growth: number of renewal limbs, number of shoots, shoot length, number of shoot leaves, shoot leaf area, final fruit set, fruit size, yield of large fruit, crop value from large fruit, soluble solids, and titratable acidity. The following characteristics decreased: limb age, number of secondary limbs, number of spurs, number of spur leaves, spur leaf area, the ratio of spur leaf area to shoot leaf area, fruit count per tree, yield, yield efficiency, crop value from small fruit, overall crop value, and sugar:acid ratio. The LTR provides a measurable way to define and create different levels of pruning severity and achieve consistent outcomes. This allows a greater degree of accuracy and precision to dormant pruning of tall spindle apple trees. The use of the LTR to establish the level of pruning severity allows the orchard manager to set crop load potential through regulation of the canopy bearing surface. This metric is also a necessary step in the development of autonomous pruning systems.
Randomized Crossover Trial of Blood Volume Monitoring–Guided Ultrafiltration Biofeedback to Reduce Intradialytic Hypotensive Episodes with Hemodialysis
Authors: Leung Kelvin C.W. , Quinn Robert R. , Ravani Pietro , Duff Henry , MacRae Jennifer M.
Published: October 2017

Background and objectives

Intradialytic hypotension (IDH) is associated with morbidity. The effect of blood volume–guided ultrafiltration biofeedback, which automatically adjusts fluid removal rate on the basis of blood volume parameters, on the reduction of IDH was tested in a randomized crossover trial.

Design, setting, participants, & measurements

We performed a 22-week, single blind, randomized crossover trial in patients receiving maintenance hemodialysis who had >30% of sessions complicated by symptomatic IDH in five centers in Calgary, Alberta, Canada. Participants underwent a 4-week run-in period to standardize dialysis prescription and dry weight on the basis of clinical examination. Those meeting inclusion criteria were randomized to best clinical practice hemodialysis (control) or best clinical practice plus blood volume–guided ultrafiltration biofeedback (intervention) for 8 weeks, followed by a 2-week washout and subsequent crossover for a second 8-week phase. The primary outcome was rate of symptomatic IDH.

Results

Thirty-five participants entered, 32 were randomized, and 26 completed the study. The rate of symptomatic IDH with biofeedback was 0.10/h (95% confidence interval, 0.06 to 0.14) and 0.07/h (95% confidence interval, 0.05 to 0.10) during control (P=0.29). There were no differences in the rate or proportion of sessions with asymptomatic IDH or symptoms alone. Results remained consistent when adjusted for randomization order and study week. There were no differences between intervention and control in the last study week in interdialytic weight gain (difference [SD], −0.02 [0.8] kg), brain natriuretic peptide (1460 [19,052] ng/L), cardiac troponins (3 [86] ng/L), extracellular water–to–intracellular water ratio (0.05 [0.33]), ultrafiltration rate (1.1 [7.0] ml/kg per hour), and dialysis recovery time (0.43 [19.25] hours).

Conclusion

The use of blood volume monitoring–guided ultrafiltration biofeedback in patients prone to IDH did not reduce the rate of symptomatic IDH events.