bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mitigation of Formation Damage Caused by Macrormolecular Materials Using "Liquid" Polymers
Authors: Lakatos I. J. , Lakatos-Szabo J. , Szentes G. , Vadaszi M. 
Published: June 2013

Abstract
The biopolymers and synthetic polymers are available as concentrated solutions, gels, crushed powders, beads and partially pre-crosslinked solid microgels. All of them are notorious of their poor solubility and jointly with their incompatibility in porous systems often causes serious formation damage hard to cure. Therefore, searching such formulations, which eliminate the mentioned drawbacks, may contribute significantly to improvement of polymer technologies. One of the possible options is the application of "liquid" polymer.
The "liquid" polymer is a stabilized suspension of bead-like polymers in organic solvent with active content of 40–45%. The polymer beads are monodispersed and have narrow size distribution (2–4 μm). Usually anionic and nonionic tenside mixtures are used to stabilize the dispersion. The laboratory studies focused on dissolution phenomena, colloid chemical, rheological, and flow properties in porous media (sandstone) of polymer solutions prepared by different "liquid" polymers. Based on the experimental findings, it was found that using "liquid" polymers readily and rapidly dissolve in water, the solutions are free of microgels and mechanical entrapment was minimal in low permeable sandstone cores. In addition, they decrease the surface tension to 30–35 mN/m, the interfacial tension lowering was min. one order of magnitude, and they proved to be compatible with other chemicals (e.g. silicates). In additions, the rheological and flow properties were identical or very similar to those data obtained by conventional solid polymers.
The extra beneficial properties of "liquid" polymers may significantly contribute to improvement of polymer-based technologies; meanwhile the surface facilities can be simplified and the chemical cost remains the same. The "liquid" polymer was successfully applied in water shutoff and conformance treatments in oilfields (Oman), but its use is also recommended in smart water flooding and chemical EOR methods.
Experimental Investigation of the Impact of Asphaltene Adsorption on Two Phase Flow in Porous Media
Authors: Hematfar V. , Maini B. B. , Chen Z. 
Published: June 2013

Abstract
While numerous investigations have studied asphaltene precipitation and deposition in porous media and their effects on absolute permeability, there is still a knowledge gap for understanding the changes in two-phase flow behaviour, displacement performance, relative permeability and recovery due to asphaltene adsorption and wettability alternation. The objectives of this work are: 1) to study the effect of brine salinity and asphaltene concentration on adsorption of asphaltene on pore surfaces and 2) to evaluate the effect of asphaltene adsorption on waterflooding performance and oil-water relative permeability. Experiments were conducted in sand-packs and each sand-pack was subjected to a series of flow tests comprising: 1) measurement of absolute permeability, 2) injection of pure toluene to displace the brine down to irreducible water saturation, 3) waterflooding at a constant rate to determine oil-water relative permeability, 4) long-term injection of a solution of asphaltene in toluene to allow the asphaltene to adsorb on sand surfaces and 5) a second waterflood to evaluate the post adsorption performance of waterflooding and oil-water relative permeability. Effluent samples were collected during the injection of asphaltene solution and analyzed with a spectro-photometric technique to determine the asphaltene concentration. The level of adsorption was determined from asphaltene material balance. A back pressure regulator was used to maintain the pressure of the system and the pressure drop across the sand-pack was measured and recorded. Furthermore, the interfacial tensions between asphaltene solutions and brines of different concentration were measured. A history-matching technique was developed to determine the shape of relative permeability curves by matching the production data using a genetic algorithm. The experimental results show that relative permeability and oil recovery were affected by asphaltene adsorption. The effect was more pronounced when the brine salinity was low. Displacement performance and recovery strongly depend on rock-fluid properties which may be affected by asphaltene adsorption.
Novel Combination of Channel Fracturing with Rod-Shaped Proppant Increases Production in the Egyptian Western Desert
Authors: Gawad A. A. , Long J. , El-Khalek T. , Bashandy R. , Mabrouk T. , Shaaban A. , Mathur A. , Yosry M. , Kraemer C. C. , Bernechea J. M. 
Published: June 2013

Abstract
This paper describes the application for the first time of a novel channel fracturing technique combined with rod-shaped proppant in selected production targets in several fields in the Egyptian western desert. The channel fracturing technique introduces channels within the proppant pack that increase conductivity and effective half-length leading to increased productivity (Gillard et al. 2010). Rod-shaped proppant when used as tail-in in fracturing treatments increases near-wellbore fracture conductivity and prevents proppant flowback due to its particular geometry (McDaniel et al. 2010).
The western desert fields in the Qarun concession area in Egypt are characterized as complex, thin-bedded sequences with heterogeneous laminated sandstones producing mainly from the Abu Roash and Upper Bahariya formations. Hydraulic fracturing has traditionally been employed to produce hydrocarbons from these marginal reservoirs. The channel-fracturing technique was first introduced in the Amana fields in late 2012 combined with rod-shaped proppant for flowback control and conductivity enhancement. Early-time normalized production of the wells fractured with this technique increased by 89% over offset wells fractured conventionally, and the application of the channel fracturing technique eliminated the incidence of premature screen-outs in all fields.
The positive results from implementation of this combined stimulation technique have led to a vigorous expansion of its utilization throughout Egypt's western desert area, including a refracturing campaign for older wells where conventional fracturing techniques did not yield the desired results.
Novel Insight into Polymer Injectivity for Polymer Flooding
Authors: Yerramilli Sanjay Surya , Zitha P. L. , Yerramilli Ramesh Chandra 
Published: June 2013

Abstract
A considerable portion of world reserves are located in mature and viscous oil reservoirs having thickness less than 15 m. Polymer flooding is a mature technology and is the most important EOR method based on full field case histories. Accurate assessment of injectibility of viscous polymer solutions into these reservoirs without induced fractures is a major challenge. Therefore, the objective of this study is to experimentally investigate and model polymer injectivity in porous media using unfiltered partially hydrolyzed polyacrylamide (HPAM) solutions for wide range of polymer concentrations (125–5000 ppm) and salinities (5–20 g/L) in high permeability sandstones. Data from rheological measurements and single phase linear core flood studies carried out as a part of this study were utilized for understanding the key microscopic (pore level) mechanisms and for quantifying the injectivity.
Based on the experimental analyses, it was found that viscous nature of polymer solutions and their retention in porous media were the main mechanisms for loss in injectivity. Data obtained from the experiments were used to validate and fine tune the model. Subsequently, with the help of the Langmuir adsorption isotherm, filtration theory, permeability reduction model, Non-Newtonian viscosity and Darcy laws numerical modeling was performed for predicting the injectivity losses during polymer injection. A good quality match was obtained with experimental data. Finally, sensitivity of polymer concentration and salinity on injectivity was studied. Further, the results from this study, will serve as an auxiliary input for field scale simulations, will help operators in the selection, design and execution of the field projects and will stand as guidelines for extending the polymer flooding technology for heavy oil reservoirs.
Optimization of Microemulsion Formulations with Linker Molecules
Authors: Quintero Lirio , Pietrangeli Gianna , Salager Jean-Louis , Forgiarini Ana 
Published: June 2013

Abstract
Applications of microemulsion technology in the drilling and production industry have increased in recent years. Some of these applications include oil-based drilling fluid displacement to water-based fluid, near-wellbore remediation, well stimulation, enhanced oil recovery, flow-back recovery in shale gas wells, and cement spacers.
Microemulsion formulations for these applications need to have high oil solubilization and very low interfacial tension, which is achieved with relatively high concentration of surfactants. High-performance microemulsion systems with lower surfactant concentrations are desired in order to optimize the cost of microemulsion technology applications. The reduction of surfactant concentration and cost could be achieved by introducing linker additives in the formulations. The addition of linker molecules enhances the solubilization property of microemulsions, which increases the hydrophilicity and/or the lipophilicity behavior of surfactants.
Previous studies indicate that addition of a proper linker molecule could significantly increase the solubilization of the oil. The lipophilic linker molecules (e.g. long chain amines, acids, alcohols, phenols) increase the interactions between the surfactant and oil, although with some disorder to avoid formation of highly-organized structures and to decrease the viscosity.
This paper provides a comprehensive discussion of work carried out to determine the influence of lipophilic and hydrophilic linkers in microemulsions formulated with anionic/nonionic surfactant blends. The interfacial tension, fluids compatibility, and return permeability evaluation of microemulsion formulations containing lipophilic linkers prove that these additives bring a significant improvement in water injection or crude oil production.
A Highly Accurate Modified Method of Characteristics for Convection–dominated Flow Problems
Authors: Machmoum Ahmed , Seaïd Mohammed 
Published: June 2013

AbstractHigh-order accurate methods for convection-dominated flow problems have the potential to reduce the computational effort required for a given order of
solution accuracy. The state of the art in this field is more advanced for Eulerian methods than for semi-Lagrangian methods. In this paper, we introduce a new higher
order approach that is based on combining the modified method of characteristics with the gradients computed during solution reconstruction. Special attention is given to
the class of third-order schemes which uses a higher-order method to calculate the departure points and a high-order polynomial reconstruction to interpolate the solution
at the characteristic feet. Numerical experiments are carried out on several benchmark transport-diffusion equations including incompressible Navier-Stokes problems.
The computed results support our expectations for a robust and high-order accurate method.
Numerical Study of Two-grid Preconditioners for 1-d Elliptic Problems with Highly Oscillating Discontinuous Coefficients
Authors: Iliev O. , Lazarov R. , Willems J. 
Published: June 2013

AbstractVarious advanced two-level iterative methods are studied numerically
and compared with each other in conjunction with finite volume discretizations of symmetric
1-D elliptic problems with highly oscillatory discontinuous coefficients. Some of
the methods considered rely on the homogenization approach for deriving the coarse
grid operator. This approach is considered here as an alternative to the well-known
Galerkin approach for deriving coarse grid operators. Different intergrid transfer operators
are studied, primary consideration being given to the use of the so-called problemdependent
prolongation. The two-grid methods considered are used as both solvers
and preconditioners for the Conjugate Gradient method. The recent approaches, such
as the hybrid domain decomposition method introduced by Vassilevski and the globallocal
iterative procedure proposed by Durlofsky et al. are also discussed. A two-level
method converging in one iteration in the case where the right-hand side is only a
function of the coarse variable is introduced and discussed. Such a fast convergence for
problems with discontinuous coefficients arbitrarily varying on the fine scale is achieved
by a problem-dependent selection of the coarse grid combined with problem-dependent
prolongation on a dual grid. The results of the numerical experiments are presented
to illustrate the performance of the studied approaches.
Simulation of Interacting Discontinious Solutions on Dynamically Adaptive Grids
Authors: Breslavsky P.V. , Mazhukin V.I. 
Published: June 2013

Abstract A further development of the dynamic adaptation method for gas dy-
namic problems describing multiple interactions of the shock waves, rarefaction waves,
and contact boundaries are considered. By the test Woodward — Colella problem the
efficiency of the proposed method for solving problems of gas dynamics with explicit
definition of shock waves and contact boundaries is shown. For the problem solution
mechanism of the adaptation of diffusion type is used. A choice of the adaptation coeffi-
cient for obtaining solution in each of subdomains of quasiuniform grid is substantiated.
The discontinuities interaction between each other is solved by the Riemann problem.
Application of the dynamic adaptation method allowed obtaining solution in 420 cells
which practically coincides with the results of WENO5m method in 12800 cells.
Approximation of the Operator Exponential and Applications
Authors: Gavrilyuk I.P. 
Published: June 2013

AbstractA review of the exponentially convergent approximations to the operator
exponential is given. The applications to inhomogeneous parabolic and elliptic
equations, nonlinear parabolic equations, tensor-product approximations of multidimensional
solution operators as well as to parabolic problems with time dependent
coefficients and boundary conditions are discussed.
Fully Discrete Galerkin Method For Fredholm Integro-Differential Equations With Weakly Singular Kernels
Authors: BRUNNER H. 
Published: June 2013

AbstractWe analyze the optimal superconvergence properties of piecewise polynomial
collocation solutions on uniform meshes for Volterra integral and integrodifferential
equations with multiple (vanishing) proportional delays. It is shown that for delay integro-differential equations the recently obtained optimal order is also attainable.
For integral equations with multiple vanishing delays this is no longer true.
Contribution of Agricultural Field Production to Emission of Greenhouse Gases (Ghg)
Authors: Bálint Ágnes , Hoffmann Sándor , Anton Attila , Szili-Kovács Tibor , Heltai György 
Published: June 2013

Abstract
According to global inventories the agricultural field production contributes in a significant measure to increase of concentration of greenhouse gases (CO2, N2O, CH4) in the atmosphere, however their estimated data of emissions of soil origin differ significantly. Particularly estimates on nitrogen-oxides emissions show a great temporal and spatial variability while their formations in microbial processes are strongly influenced by biogeochemical and physical properties of the soil (eg microbial species, soil texture, soil water, pH, redox-potential and nutrient status) and land use management through the impact of the application of natural and synthetic fertilisers, tillage, irrigation, compaction, planting and harvesting. The different monitoring systems and inventory models were developed mostly from atmospheric chemistry point of view and little comprehensive data exist on the processes related to GHG emissions and their productions in agricultural soils under ecological conditions of Central Europe. This paper presents the new results of a project aimed elaboration of an experimental system suitable for studying relationships between the production and emission of greenhouse gases and plant nutrition supply in agricultural soils under Hungarian ecological conditions. The system was based on a long-term fertilisation field experiment. Mesocosm size pot experiments were conducted with soils originating from differently treated plots. The production of CO2 and N2O was followed during the vegetation period in gas traps built in 20 cm depth. Undisturbed soil columns were prepared from the untreated side parcels of the field experiment and the production of CO2 and N2O was studied at 20, 40 and 60 cm depth. A series of laboratory microcosm experiments were performed to clarify the microbial and environmental effects influencing the gas production in soils. The CO2 and N2O were determined by gas chromatography. The NOx was detected by chemiluminescence method in headspace of microcosms. In the mesocosm and soil columns experiments influence of plant nutrition methods and environmental factors was successfully clarified on seasonal dynamics and depth profile on CO2 and N2O productions. The database developed is suitable for estimating CO2 and N2O emissions from agricultural soils.
Use of Artificial Neural Networks in Predicting Direct Nitrous Oxide Emissions from Agricultural Soils
Authors: Kolasa-Więcek Alicja 
Published: June 2013

Abstract
Agricultural greenhouse gases emissions are mainly produced in direct emissions from plant and animal production as well as those associated with land use changes. Agriculture is a major source of atmospheric nitrous oxide (N2O). N2O emissions from agricultural production has the source primarily in soil fertilized by mineral and organic fertilizers. In Poland, agricultural soils are responsible for 77.1% of emissions. Emissions associated with the animal manner farming amount 22.8%. Studies attempt to modeling and predicting of N2O emissions from Direct Soil Emissions in relation to the use of crops and livestock population. In the analysis an artificial neural networks were used. The best values showing the quality of neural regression model were obtained by multilayer perceptrons MLP. Based on the sensitivity analysis, attempts were taken to determine the extent of the contribution of each selected variables on the estimate of the direct emissions of N2O from agricultural soils. The sensitivity analysis of designed network on the structure MLP 9-4-1 shows that the amount of nitrogen fertilizer consumption has the biggest share in the shaping of N2O emissions from Direct Soil Emissions. The sensitivity analysis of network on the structure MLP 16-5-1 pointed to participate cattle and pigs as the most important in the formation of N2O emissions from Direct Soil Emissions. Among the crops in Poland, which may affect the release of N2O stands out rapeseed and rye. The study was conducted using the statistical package Statistica v. 10.0.
Bee Fauna (Apoidea: Hymenoptera) of the Suez Canal Region, Egypt
Authors: Shebl Mohamed , Kamel Soliman , Mahfouz Hatem 
Published: June 2013

Summary
The diversity of solitary bees varies depending on the vegetation, nesting habitats, and nesting fragmentation. The agriculture development in the Suez Canal region is receiving a great deal of attention in Egypt, thus, the diversity of solitary bees are essential for high quality production of seeds, vegetables, and fruit. The objective of this study was to evaluate the biodiversity of solitary bee populations around the Canal region. About 900 - 1000 specimens of bees were collected from different locations of the Ismailia, Suez, and Sinai Governorates. Fifty-five species of bees were identified. With the exception of Melittidae family, all the bee families were present in the Canal region. The total number of species for each family were 7, 9, 11, 13, and 15 species for Andrenidae, Colletidae, Apidae, Halictidae, and Megachilidae, respectively. Lasioglossum mandibularie (Morawitz, 1866) is a newly recorded species collected from Egypt. In the Suez Canal region, the most abundant species found with large populations were Andrena ovatula ssp. ovatula (Kirby, 1802), Ceratina tarsata Morawitz, 1872, and Colletes lacunatus Dours, 1872.
Evapotranspiration changes in the forest-steppe and steppe zones under soil mulching
Authors: Shumova Nadezhda 
Published: June 2013

Abstract
This paper contains the method and results of calculation evapotranspiration and its structure - transpiration and evaporation from traditionally tilled and mulched soil. The data considered indicate that in the arid regions of territory under study the evapotranspiration when soil is mulched does not change significantly and only the relation between the transpiration and soil evaporation changes. In the wet regions, evapotranspiration decreases when the soil is mulched which can result in a certain disturbance of the natural structure of the hydrological cycle and possible overmoistening soils.
Determination of the Temperature Field Using Liquid Crystal Thermography and Analysis of Two-Phase Flow Structures in Research on Boiling Heat Transfer in a Minichannel
Authors: Piasecka Magdalena 
Published: June 2013

Abstract
The paper presents the application of liquid crystal thermography for temperature determination and visualisation of two phase flow images on the studied surface. Properties and applications of thermochromic liquid crystals are discussed. Liquid crystals were applied for two-dimensional detection of the temperature of the heating foil forming one of the surfaces of the minichannel along which the cooling liquid flowed. The heat flux supplied to the heating surface was altered in the investigation and it was accompanied by a change in the color distribution on the surface. The accuracy of temperature measurements on the surface with liquid crystal thermography is estimated. The method of visualisation of two-phase flow structures is described. The analysis of monochrome images of flow structures was employed to calculate the void fraction for some cross-sections. The flow structure photos were processed using Corel graphics software and binarized. The analysis of phase volumes employed Techsystem Globe software. The measurement error of void fraction is estimated.
Examining the Levels of Self-Leadership Perceptions of University Student- Athletes in Terms of Sociodemographic Characteristics
Authors: Türköz Tolga , Mutlu T. Osman , Tabak Akif , Erdoğan Murat 
Published: June 2013

Abstract The purpose of the present study is to determine the difference of self-leadership perceptions for university student-athletes in terms of sociodemographic characteristics. The research involved 167 university student-athletes aged 18-21 years (Muğla and Kocaeli at Turkey). Self-leadership perceptions were measured by the Revised Self-Leadership Questionnaire. The number of strategies of selfleadership was calculated in the distribution of mean scores. It was found that variables such as age, education status of mother, and monthly income of the university students do not cause any difference in the levels of self-leadership perceptions. On the other hand, other factors were determined to create statistically significant differences in the use of self-leadership strategies: gender; dealing with sport outside of school; taking part in teams; branch of interested sport; education status of father; socioeconomic status; personal sport history of athletes. It has revealed that not only the psychical factors but also behavioral, cognitive, and psychological factors of self-leadership have important roles in increasing the performance of student-athletes in sport activities.