bluuebunny/crossref_metadata_2025 huggingface dataset:
Absence of 232,230,228Th enhancement decay by ultrasound exposure
Authors: Aupiais Jean , Cousin V. , Nikitenko S.I. , Pflieger R. , Moisy Philippe
Published: January 2013

We report on our attempt to reproduce the 228Th decay enhancement under the effect of power ultrasound claimed recently in the literature. The evolution of natural thorium isotopic composition (232Th, 230Th, and 228Th) in various aqueous solutions submitted to 20 kHz power ultrasound (0.18 W mL−1, 20 ºC, Ar). The radioactivities of the three isotopes of thorium (232Th, 230Th and 228Th) were followed by α liquid scintillation counting technique. No change was detected during ultrasonic irradiation. Our results demonstrate that under the studied conditions the rate of Th isotopes radioactive decay is not modified under the effect of ultrasound on aqueous solutions of thorium salts.
Benzoquinone-Hydroquinone Couple for Flow Battery
Authors: Nawar Saraf , Huskinson Brian , Aziz Michael
Published: January 2013

At present, there is an ongoing search for approaches toward the storage of energy from intermittent renewable sources like wind and solar. Flow batteries have gained attention due to their potential viability for inexpensive storage of large amounts of energy. While the quinone/hydroquinone redox couple is a widely studied redox pair, its application in energy storage has not been widely explored. Because of its high reversibility, low toxicity, and low component costs, we propose the quinone/hydroquinone redox couple as a viable candidate for use in a grid-scale storage device. We have performed single-electrode tests on several quinone/hydroquinone redox couples, achieving current densities exceeding 500 mA/cm2, which is acceptable for use in energy applications. We fabricated a full cell using para-benzoquinone at the positive electrode against a commercial fuel cell hydrogen electrode separated by a Nafion membrane. We evaluated its performance in galvanic mode, where it reached current densities as high as 150 mA/cm2. The results from these studies indicate that the quinone/hydroquinone redox couple is a promising candidate for use in redox flow batteries.
Ab-initio Calculations to Model Anomalous Fluorine Behavior
Authors: Diebel Milan , Dunham Scott T.
Published: January 2013

Implanted fluorine has been observed to behave unusually in silicon, manifesting apparent uphill diflusion [1]. We are further motivated to understand the behavior of implanted fluorine in silicon by experiments which suggest that fluorine reduces boron diflusion [2, 3, 4, 5] and enhances boron activation in shallow junctions [2, 3]. In order to investigate fluorine behavior, we calculated the energy of fluorine defect structures in the framework of density functional theory (DFT). Besides identifying the ground-state con.guration of a single fluorine atom in silicon, a set of energetically favorable fluorine defect structures were found. The latter strongly suggests a distinct fluorine diflusion mechanism, which was implemented in a continuum diflusion simulation and compared to experimental data.
Large-Scale Molecular Dynamics Simulations of Interstitial Defect Diffusion in Silicon
Authors: Richie David A. , Kim Jeongnim , Hennig Richard , Hazzard Kaden , Barr Steve , Wilkins John W.
Published: January 2013

The simulation of defect dynamics and evolution is a technologicaly relevant challenge for computational materials science. The diffusion of small defects in silicon unfolds as a sequence of structural transitions. The relative infrequency of transition events requires simulation over extremely long time scales. We simulate the diffusion of small interstitial clusters (I1, I2, I3) for a range of temperatures using large-scale molecular dynamics (MD) simulations with a realistic tight-binding potential. A total of 0.25 μ sec of simulation time is accumulated for the study. A novel real-time multiresolution analysis (RTMRA) technique extracts stable structures directly from the dynamics without structural relaxation. The discovered structures are relaxed to confirm their stability.
Alimentação na escola e autonomia - desafios e possibilidades
Authors: Barbosa Najla Veloso Sampaio , Machado Neila Maria Viçosa , Soares Maria Cláudia Veiga , Pinto Anelise Regina Royer
Published: January 2013

Este estudo tem por objetivo evidenciar a alimentação na escola como importante política na promoção da autonomia dos estudantes por meio de uma educação alimentar e nutricional desenvolvida de modo curricular, integrado pelos diferentes atores e sob a ótica da cidadania. Retomar conceitos fundamentais no contexto da alimentação escolar, refletindo sobre eles por meio de pressuposições teóricas para identificar possíveis estratégias na promoção de cidadania e da autonomia na escola. As estratégias envolveram educação alimentar e nutricional com a presença cotidiana de qualidade e adequação na alimentação escolar, de debates sobre as diversas dimensões da alimentação no currículo vivido e com integração da alimentação no projeto pedagógico estendido a vários âmbitos do sistema de ensino. A alimentação na escola suscita que haja integração das ações, dos atores e dos diversos espaços sociais interessados pelo tema alimentação, como ministérios, sistemas de ensino, secretarias e escolas, de modo que se possa enfrentar, de modo integrado, sistemático, consistente e eficiente, as demandas da realidade contemporânea.
Alimentação escolar nas comunidades quilombolas: desafios e potencialidades
Authors: Sousa Lucilene Maria de , Martins Karine Anusca , Cordeiro Mariana de Morais , Monego Estelamaris Tronco , Silva Simoni Urbano da , Alexandre Veruska Prado
Published: January 2013

O Programa Nacional de Alimentação Escolar (PNAE) é uma estratégia de Segurança Alimentar e Nutricional (SAN) para estudantes de escolas públicas. Este artigo tem por objetivos discutir os desafios e as potencialidades da alimentação escolar nas comunidades quilombolas e relatar a experiência do Centro Colaborador em Alimentação e Nutrição do Escolar da Universidade Federal de Goiás e Região Centro-Oeste (CECANE UFG/Centro-Oeste). Relato de experiência associado à sistematização da literatura sobre o PNAE, SAN e outras políticas. O acesso permanente e adequado às políticas sociais é um desafio para as comunidades quilombolas. Identificam-se na execução do PNAE entraves de ordem econômica, estrutural e social. Neste contexto, a Lei 11.947/2009 incentiva o desenvolvimento local, por meio da aquisição de alimentos da região e determina valor per capita diferenciado, traduzido em cardápio com alimentos da cultura negra e que atenda no mínimo 30% das necessidades nutricionais diárias. O CECANE UFG/Centro-Oeste no projeto alimentação, saúde e qualidade de vida de escolares quilombolas realiza ações em SAN. O campo da alimentação escolar mostra-se sensível às necessidades locais e apoia o desenvolvimento e a promoção da qualidade de vida.
Qualidade de vida de professores de Instituições de Ensino Superior Comunitárias do Rio Grande do Sul
Authors: Koetz Lydia , Rempel Claudete , Périco Eduardo
Published: January 2013

Qualidade de vida é a percepção dos sujeitos sobre sua posição perante a sociedade, permeada por sua cultura, valores e cotidiano e com vistas a seu objetivo e expectativas de vida e as formas de pensar sobre sua vida. O estudo investigou a qualidade de vida de docentes de instituições de ensino superior comunitárias não confessionais, com mais de 40 anos de atuação e com mais de dez mil alunos no Rio Grande do Sul. A pesquisa, com perfil quali-quantitativo e de corte transversal, ocorreu em agosto e setembro de 2011, através de um questionário de perfil profissional e do questionário WHOQOL-bref. Participaram 203 professores, perfazendo 17% do total de docentes das três instituições analisadas. Quando analisado o índice de qualidade de vida de acordo com a titulação dos docentes, os 22 especialistas apresentam o maior escore no domínio psicológico (72,1 ± 3,1) e o menor no domínio social (69,3 ± 4,4), entre os 125 mestres e os 43 doutores os maiores escores foram no domínio físico (74,8 ± 1,3 e 75,7 ± 2,1 respectivamente) e os menores no domínio ambiental (69,4 ± 1,0 e 70,8 ± 1,8 respectivamente). Conclui-se que o índice de qualidade de vida dos docentes foi enquadrado como bom em todos os domínios analisados e sem diferença estatística significativa entre eles.
A endogamia explicaria a elevada prevalência de deficiências em populações do Nordeste brasileiro?
Authors: Santos Silvana Cristina dos , Melo Uirá Souto , Lopes Simone Silva dos Santos , Weller Mathias , Kok Fernando
Published: January 2013

Apesar da inexatidão conceitual e de métodos de aferição, a OMS estima que cerca de 10% da população mundial apresente alguma forma de deficiência. Com a finalidade de investigar a prevalência e a etiologia das deficiências e verificar se elas estariam associadas à endogamia, foi realizado um estudo epidemiológico transversal com uso do método do informante envolvendo cinco municípios do Estado do Rio Grande do Norte, no Nordeste brasileiro; nos quais foram estimadas frequências de casamentos consanguíneos que variam de 9 a 32%. A prevalência média estimada para deficiências nos cinco municípios amostrados foi de 4,53%, obtida por meio de entrevistas envolvendo 37,87% de uma população de 39.054 habitantes. Em média, 25% dos casais consanguíneos e 12% dos não consanguíneos apresentaram um ou mais filhos com alguma deficiência. A elevada prevalência de pessoas com deficiência no Nordeste brasileiro pode ter associação com a manutenção da tradição de casamentos consanguíneos nessas populações e parte dessas deficiências pode ser causada por doenças genéticas.
Novel Methods of Identifying Hydrocarbon Bearing Formation with Low Resistivity Contrast from Conventional Logs in Tight Sandstone Reservoirs of North Ordos Basin
Authors: Deng Jiang-Min , Liu Xiao-Peng , He Kui , Hu Xiao-Xin
Published: January 2013

It’s difficult in identifying hydrocarbon bearing formation from conventional logs in tight sandstone reservoirs due to the low resistivity contrast caused by the complicated pore structure and high water saturation in north Ordos basin. The experiment of relative permeability illustrates that the water saturation of the target Chang 6 Formation mentioned in this study reach to 58%. To identify hydrocarbon bearing formations from water saturated layers, a method, which is the minimal resistivity method is introduced. To obtain the minimal resistivity of hydrocarbon bearing reservoir, two novel methods, which are formation simulation and rock resistivity experiments, are proposed in this paper. The results shows that the minimal resistivity of hydrocarbon bearing layer in Chang 6 Formation is 40Ω.m. Field examples shows that the proposed methods are effective in obtaining the minimal resistivity and identifying hydrocarbon bearing formations with high water saturation, they can be extended widely in other tight sandstone reservoirs.
Development of Water-Dissolved Gas in Nishikambara Gas Field and Calculation of Land Subsidence Induced by Water Pumping
Authors: Higuma T.. , Fujii H.. , Horikawa K..
Published: January 2013

Water-dissolved gas is a natural gas resource dissolved in groundwater. The gas mainly consists of methane gas and has been produced in many parts of Japan since the 1930’s. Although it is considered as an unconventional resource on a global standard, about 20 % of gas production in Japan comes from the water-dissolved gas fields. The resource is considered important in Japan since the R/P ratio of the water-dissolved gas is larger than one hundred years. In addition, iodine is commonly produced with the groundwater as a byproduct in a water-dissolved gas fields, which makes Japan as one of the largest iodine producers in the world.

Although water-dissolved gas is an attractive resource, its development often causes significant land subsidence due to the need of pumping large amount of groundwater. In Nishikambara water-dissolved gas field in Niigata, Japan, the target field of this research, a maximum 200 mm/year of land subsidence was observed at the early stage of the development in the 1950’s. As a countermeasure, all produced water has been re-injected into each reservoir since the early 1970’s, which enabled the gas production without any land subsidence for many decades. In this research, numerical models of water-dissolved gas reservoirs and the method to calculate the magnitude of the land subsidence were developed to investigate the mechanisms of gas production and land subsidence performance for the further development of the field. The numerical reservoir simulation models were developed using a black oil simulator, ECLIPSE100, on the basis of the field data. The land subsidence performance was calculated using a linear equation based on Hooke’s law. The reservoir pressure calculated by the numerical reservoir simulation models were used to calculate the magnitude of the land subsidence. Through the history matching, good agreement between the observed and calculated land subsidence was obtained.
Multidisciplinary Insights from Analysis of Borehole Microseismic Data from the Cotton Valley Tight Gas Formation in East Texas, U.S.A.
Authors: Gangopadhyay Abhijit , Rodrigues Victoria , Malayalam Atif , Liu Shujie , Plemons Patricia , Faz Ignacio
Published: January 2013

Microseismic data were acquired during the hydraulic fracture stimulation of a horizontal well in the Cotton Valley tight gas formation in east Texas, U.S.A., using a borehole observation array. The ~3700 feet horizontal well was successfully stimulated in six stages using slickwater cross-linked treatment at 80 – 88 barrels/minute. The resulting microseismic events were recorded in a vertical observation well using an array of seven sensors spaced at 100 feet intervals, spanning ~600 feet along the wellbore, and ~125 feet above the target reservoir. Based on 148 microseismic events, the inferred, dominant fracture orientations range between ~S59°W and ~S65°W, consistent with the regional orientations of SHmax. At least one ~N-S oriented fracture intersected the dominant orientations. Using all microseismic event locations, the derived fracture lengths are between ~2,257 feet and ~2,529 feet, independently confirmed by observed inter-well fracture hits in the area. Calculated fracture heights range between ~125 feet and ~387 feet indicating that the stimulations were contained within the ~400 feet target reservoir. The dominant linear fractures initiated in intervals within the tight sand where gamma ray log values are < ~70 gAPI units, thereby indicating a potential diagnostic range of frac-ability, consistent with independent field-wide rock typing study within the Cotton Valley formation. While the number and size of microseismic events varied amongst stages, treatment pressures and proppant concentration >~4,000 psi and ~1.3 ppg respectively, influenced stimulation of the reservoir, resulting in larger and more frequent microseismic events. Production characteristics of the treatment well, and tracer data collected from it, indicate that only part of the inferred fracture network volume from microseismic events, is effectively stimulated. These multidisciplinary insights guide improvements in future horizontal well stimulations in tight gas formations.
Practical Insights and Benefits of Integrating Technology into Exploration, Appraisal and Development of Unconventional Gas and Liquid Rich Shale Reservoirs
Authors: Oz Bora , Braun David , Vitthal Sanjay , Okouma Mangha Viannet , Molenaar Mathieu M , Peringod Chandran , Kazakoff Sergei , Li Yongyi , Asgar-Deen Michele , Langille David Lindsay
Published: January 2013

Abstract

In the current high oil / low gas price North American environment, and considering the new options available for well completions technology in unconventional reservoirs, recent industry activities have turned their focus to the areas of Liquid Rich Shales (LRS) and Light Tight Oil (LTO) along with unconventional tight and shale gas (UG).

Integrated workflows are important to the successful execution of this portfolio, i.e. systematic methodologies to screen and appraise opportunities, and cutting edge integrated technologies must be viewed as key enablers. It is also important to maintain a life-cycle mindset and leverage economies of scale to execute projects faster and more efficiently.

This paper will discuss some of the advances and best practices that Shell has in each of the following disciplines, the value of R&D and applied technologies as well as integrated workflows used for exploration, appraisal and development of UG, LRS, and LTO plays: • Geological screening and sweet-spotting • Geomechanics evaluation and modeling • Reservoir engineering, including PVT sampling and characterization • Completions, stimulations and diagnostics • Artificial lift and operational considerations
Case History of Using Integrated Reservoir Modeling Workflow for Tight Gas Reservoirs
Authors: Abacioglu Yafes , Sebastian Herbert M. , Bonney Kyle E.
Published: January 2013

As the demand for energy increases, more and more low-permeability reservoirs are being developed with the help of advancements in hydraulic fracturing and horizontal drilling technologies. Integrated reservoir modeling studies become increasingly important to understand and improve reservoir management of such reservoirs for optimum depletion planning.

This paper presents the approach used for applying an integrated reservoir modeling workflow to the tight gas sands of the Cotton Valley reservoir. The main objective of the study is to understand well performance for horizontal infill wells with multiple hydraulic fractures.

In order to accurately simulate gas flow in hydraulically fractured wells (HFW) in full-field or regional models of unconventional gas reservoirs with many HFW, it is critical to appropriately represent these wells in the simulation models. Various methods have been used in the industry to numerically simulate hydraulic fractures in large reservoir models. In this paper, we will also review these methods and show that almost all the methods require calibration with fine grid models in which the hydraulic fracture is explicitly gridded. For homogeneous models calibration is relatively easy, but it is almost impossible for heterogeneous models. Therefore, we used local grid refinement (LGR) as the solution for modeling hydraulically fractured wells in coarse grid simulation. Our approach is different than other LGR approaches presented in the literature in that we only refine the coarse gridblocks that contain the fractures and wells.

Finally, since it is very time consuming to generate LGRs manually for models with many wells a software tool was developed to generate LGR gridding automatically for HFW for commercial simulators.
On Simulation of Flow in Tight and Shale Gas Reservoirs
Authors: Darishchev A.. , de Nancy E. N. , Lemouzy P.. , Rouvroy P..
Published: January 2013

Applicability of existing numerical simulation methodologies to unconventional reservoirs is questionable and requires investigation and research.

We have focused on gas flow simulation of a highly heterogeneous fractured reservoir with extremely low matrix permeability. First of all we have considered the key roadmap components, natural gas composition, rock properties, critical elements and the main features inherent in tight and shale gas reservoir engineering. Using field reference data and a reservoir simulator, different scenarios of gas production have been modelled. This paper presents results from a sensitivity study of the dimension of hydraulic fracturing stimulated reservoir volume (SRV), matrix and propped fracture permeability which is spatially varied as one of the most realistic approaches, and of the bottom hole pressure. The approaches "dual porosity -single permeability", "dual porosity -dual permeability" and key reservoir properties have been reconsidered for specific geological and technological conditions in order to support decision making in unconventional reservoir management. Assuming pseudo-steady state gas flow, the simulation time step and gridblock size have been adjusted with a sector model represented by a logarithmically refined grid. In comparison with previous studies, it has been stated that the proposed approach of discrete fracture network modeling can be used in cases where the dual medium approach is questionable or inappropriate. The simulations of flow that have been performed, showed that the contribution of unstimulated reservoir volume (in the vicinity of the SRV) to gas production is non-negligible and can be a significant part of gas production to be taken into account in some field cases.

The results of this study can be used in unconventional reservoir modeling and flow simulation to identify development, stimulation, and completion strategies aimed at optimization of gas production, reservoir performance and gas recovery. The proposed approach also supports risk and uncertainty analysis, revenue estimation and economic performance evaluation.
Unconventional Gas Stimulation by Creating Synthetic Sweetspot
Authors: Al-Nakhli Ayman R. , Abass Hazim , Al-Ajwad Hassan A. , KwaK Hyung T. , Al-Harith Abdullah , Al-Otaibi Ahmad
Published: January 2013

Unconventional resources are considered to be the game changer of near-by future energy. The huge resources of unconventional gas worldwide along with the increasing oil demand make the contribution of unconventional gas to be critical to the world economy. However, major challenges that operators face to produce from unconventional resources are due to the need for identifying a sweetspot, commercial stimulation technique that creates sufficient stimulated reservoir volume, very low permeability and different damage mechanisms such as water blocking, filtrate invasion during drilling, completion, stimulation or production.

This paper describes a new stimulation technique that creates synthetic sweetspot by thermal and mechanical energies. An energized fluid was used to generate localized heat and pressure in tight core samples and therefore create microfracturing. Created microfractures significantly increased permeability, porosity, and stimulated reservoir volume. A synthetic sweetspot nearby a wellbore or fracture area can be created by the new treatment mechanism. Permeability of tested cores was measured by Coreflood system and showed significant increase with new treatment technique. Communication between micro and macro pores was also found as a result of the treatment.

The treatment doesn't utilize any hydrocarbons and have no lift overs or potential damage. The generated high temperature and pressure can remove any damaging material or condensate banking near wellbore or fracture area. The new treatment technique was evaluated using Coreflood system with actual tight core samples collected from tight reservoirs in Saudi Arabia. NMR and CT-Scan analysis were used to show creation of microfracturing and permeability porosity changes.
Microseismic Leads to Improved Understanding of Hydraulic Fracturing in a Sultanate of Oman Tight Gas Well
Authors: MacKenzie Alasdair , Clark Robert Alfred , Al Anboori Abdullah
Published: January 2013

This paper details the successful downhole microseismic monitoring of a number of hydraulic fracture treatments in a horizontal well drilled in the Barik reservoir, integrating the results with treatment data. The treatment well was drilled in a direction of 312°, at 90° to the assumed maximum stress direction, with a horizontal section of 1000m.

The well was placed such that it passed within 300m of the well to be used as the observation well. The observation well was plugged immediately above the topmost reservoir perforations to minimize disturbance in micro-seismic data. The maximum geophone array length from the top of the plug to the production string was therefore 60m.

A number of fracture treatments were monitored, with the results giving understanding of fracture placement, direction, length, and height. The early results impacted immediate decision making on perforation strategy. Orientation of the maximum principal horizontal stress was confirmed. Overall frac height appears to demonstrate effective coverage of the Barik reservoir interval. This key data will strongly influence future completion design and the overall development plan of the field.
Optimal Design of Nonuniform Multiple Transverse Fractures for Horizontal Wells in Tight Gas Reservoirs
Authors: Gao Sunhua , Yao Jun , Sun Zhixue , Lu Ranran , Li Longlong , Wang Yuhang
Published: January 2013

A new comprehensive approach for designing the optimal nonuniform multiple stage/cluster transverse fractures intercepting horizontal wellbores is proposed. The proposed approach relies on the Genetic Algorithm (GA) method. Its aim is to optimize nonuniform transverse fracture spacing, number of fracture stages and clusters, nonuniform half length of fracture and fracture conductivity in order to achieve maximum net present value (NPV). The advantages of this method include: 1) The automated and comprehensive process makes it easier and more precise to find the optimum design than most previous works. 2) The design is based on a new configuration of nonuniform transverse fractures in a horizontal well. 3) The optimization of cluster spacing considers the effect of stress shadowing (Nicolas P. Roussel 2011) e.g. the opening of a fracture causes a reorientation of stresses in its neighborhood affecting negatively the efficiency of treatment. 4) It is based on NPV maximization, not just the initial production rate and cumulative production. 5) The procedure concerning well productivity also considers the effect of non-Darcy flow.

A field example in Sulige gas field is presented to demonstrate the application of our method for optimal design of multiple patterned transverse vertical hydraulic fractures intercepting horizontal wellbores. It is showed that this approach enable operators to achieve maximum reservoir productivity and NPV.

The multi-stage and multi-cluster per stage fracture treatments in horizontal wells have proven successful in tight gas recovery, by creating a large stimulated reservoir volume (SRV). In order to avoid sub-optimum fracture design relying on historical databases of hydraulic fracturing and personal experience, this new systematic method considers various factors affecting the optimal fracture spacing and length, and thus helps to get close to the optimal fracture pattern.
Transverse Fracturing of Horizontal Well - A Unified Fracture Design to Stimulate Tight Gas Sands
Authors: Rahman M. M. , Yu H.. , Sarma H. K.
Published: January 2013

Unconventional tight gas reservoirs offer an enormous opportunity towards fulfilling our energy demand, and hence, they have been subject to significant R&D activities these days. Although the tight gas sands may not be a major focus today in UAE, their potential, however, must be recognized; for, UAE has several deep tight reservoirs that need to be fully exploited for their gas reserves. For such reservoirs the conventional approach of simply fracturing the formation to stimulate the horizontal well is inadequate. This is because most currently available commercial software may lack proper optimization tools in them with several key parameters and realistic constraints. Even the systematic design methods for fracture treatment parameters with constraints are not well presented in the literature.

There are optimal number of transverse fractures and optimum treatment parameters when real field constraints and economic aspects are considered. An integrated model to optimize multistage transverse fractures has been developed to maximize gas production and net present value (NPV) with minimum treatment cost. Model couples both the industry experience and unified fracturing design parameters based on hydraulic fracture mechanics. Unified fracturing design defines the optimal compromise between the fracture width and fracture length for a given mass of proppant. Model integrates unified fracture geometry, reservoir in-situ parameters, treatment parameters at every stage, realistic design constraints, and production and economic modules. The integrated model has been successfully applied to a hypothetical deeper and tight gas sands to demonstrate its merits. A simple analytical approach has been used for evaluating and optimizing the productivity. The design indicates a significant incremental production. Effect of mass of proppant on production rate and NPV is also presented. Authors are working further to couple this integrated model with an optimization algorithm (genetic and polytope) to optimize the treatment parameters globally. This model could also be used to study the potential of the deep UAE offshore tight gas sands.
Rod-shaped Proppant Provides Superior Proppant Flowback Control in the Egyptian Eastern Desert
Authors: Edelman Jeff , Maghrabia Karim , Semary Mahmoud , Mathur Anil , Zaki Ahmed Samir , Bernechea Jose Maria
Published: January 2013

The Arta field in the Egyptian eastern desert produces mainly from the Nukhul formation that is characterized as a complex, thin-bedded sequence with heterogeneous laminated siltstone. Typical reservoirs show low-to-average permeability, low temperatures and moderately heavy oil in the 17-24 degree API range. Hydraulic fracturing is the technique traditionally employed to produce hydrocarbons from these marginal reservoirs. However, proppant flowback following the fracturing treatment is a major concern because of the relatively low formation stresses and high viscosity fluids, that results in damaged completions and impaired proppant pack permeability. Proppant flowback control therefore, became an essential requirement to maintain economical production rates from the field.

The rod-shaped proppant product was introduced in the Egyptian western desert in 2009. Published results illustrated excellent proppant flowback control as demonstrated by zero proppant flowback.1 Prior to this, several conventional proppant flowback techniques and products had been tested but they had limited application due to low reservoir temperatures. The rod-shaped proppants are inert and have no limitations on application from the reservoir or pumping equipment standpoint. Since introduction, more than 100 wells have been hydraulically fractured using this rod-shaped proppant product.

This paper describes the application of the rod-shaped proppant in the Arta field to control proppant flowback and enhance near-wellbore conductivity. The details of the evolution of rod-shaped proppant applications are presented for more than 20 wells in the Arta field, including the effects on the fractured well performance and production, as well as proppant flowback control. Results continue to demonstrate excellent proppant flowback control. In addition, cost savings result from reduced workovers, rig time savings and reduced damage to completion equipment and surface facilities.
An Integrated Approach to Rock Typing & its Impact on Well and Reservoir Performance in a Middle East Tight Gas Field
Authors: Southworth Adrian , El Hadidi Kareem , Miller Jessica
Published: January 2013

The Risha field is located in the North East region of the Hashemite Kingdom of Jordan approximately 370 km from Amman and is bordered by Iraq to the East, Syria to the North and Saudi Arabia to the South. Risha was discovered in 1987 and production started in 1989. The field consists of a predominantly tight gas reservoir but seismic and core data indicate the presence of faults and fractures. The Risha reservoir is late Ordovician, and is interpreted as a marine proglacial outwash fan setting. 45 wells have been drilled to date with mixed success and only 15 wells demonstrated some degree of production capacity. Historic well performance trends indicate a range of well types with some illustrating high initial rates, recoverable volume, and slow decline without need for stimulation. Others suffered from very low rates and sharp declines even after undergoing hydraulic fracturing. To date, high rate and recovery wells have been associated with fracture presence making fracture the key reservoir drive mechanism.

This paper attempts to analyze other potential reasons and factors causing well deliverability variation to date. It discusses the integrated approach followed to categorize the Risha rock types and determine whether they could be linked to historic reservoir performance. In this paper the reservoir units were loosely grouped according to petrophysical cutoffs, based on gamma ray, and compared with core data. The defined rock types along with well control were used to create a 3D simulation to model the rock quality variability and match the production and pressure history, with the ultimate aim of trying to understand if history performance is a reliable indicator of future behaviour.
Integration of Fracture, Reservoir, and Geomechanics Modeling for Shale Gas Reservoir Development
Authors: Gupta Jugal K. , Albert Richard A. , Zielonka Matias G. , Yao Yao , Templeton-Barrett Elizabeth , Jackson Shalawn K. , El-Rabaa Wadood , Burnham Heather A. , Choi Nancy H.
Published: January 2013

Fracture nucleation and propagation are controlled by in-situ stresses, fracture treatment design, presence of existing fractures (natural or induced), and geological history. In addition, production-driven depletion and offset completions may alter stresses and hence the nature of fracture growth. For unconventional oil and gas assets the complexity resulting from the interplay of fracture characteristics, pressure depletion, and stress distribution on well performance remains one of the foremost hurdles in their optimal development, impacting infill well and refracturing programs.

ExxonMobil has undertaken a multi-disciplinary approach that integrates fracture characteristics, reservoir production, and stress field evolution to design and optimize the development of unconventional assets. In this approach, fracture modeling and advanced rate transient techniques are employed to constrain fracture geometry and depletion characteristics of existing wells. This knowledge is used in finite element geomechanical modeling (coupling stresses and fluid flow) to predict fracture orientation in nearby wells.

In this paper, an integrated methodology is described and applied to a shale gas pad as a case study. The work reveals a strong connection between reservoir depletion and the spatial and temporal distribution of stresses. These models predict that principal stresses are influenced far beyond the drainage area of a horizontal well and hence can play a critical role in fracture orientation and performance of neighboring wells. Strategies for manipulating stresses were evaluated to control fracture propagation by injecting, shutting-in, and producing offset wells. In addition, we present diagnostic data obtained from the pad that demonstrates inter-well connectivity and hydraulic communication within the pad. The workflow presented herein can be used to develop strategies for (1) optimal infill design, (2) controlling propagation of fractures in new neighboring wells, and (3) refracturing of existing wells.
Case Studies for the Fracturing of Highly Diverse Gas Reservoirs
Authors: Ajao Omobola , Iwu Chijioke F. , Economides Michael J.
Published: January 2013

Hydraulic fracturing, which has emerged as the premier well completion technology in the petroleum industry, is applied to almost all natural gas wells, worldwide, but for different reasons. It may sound trite but all gas fields should be considered as "unconventional, compared to oil wells." In higher-permeability reservoirs (> 5 md) the remediation of reservoir-to-well turbulence is the main motivation. In lower-permeability reservoirs the main rationale is similar to oil- stimulation- but with significant adjustments. In much tighter reservoirs, including shales, the purpose is to inundate the formation with a very large number of parallel fractures, executed transversely from horizontal wells. This would lead to the effective draining of the Stimulated Reservoir Volume (SRV).

We present here two complete field studies, one in a 17 md dry gas well in Siberia, and the second from a 0.0001 md shale formation in the United States. The shale formation is assumed to have a number of similar properties with the field data from the 17md gas well. The first study shows the impact of turbulence and its removal via hydraulic fracturing. We also show the management of inside-the-fracture turbulence through the adjustment of fracture geometry and the selection of higher permeability proppant. The design approach uses the Unified Fracture Design (UFD), which is the only way to adjust fracture geometry based on expected flow performances. The drainage shape and the irregular ratio between reservoir length and fracture spacing are important considerations in SRV.

We also conduct a parametric study on the turbulence effects inside the fractures for a range of reservoir permeabilities. Which design/execution constraints are necessary at very low or very high permeabilities?

For the shale reservoir, while turbulence effects appear to be inconsequential, the length of the fracture, the spacing among fractures and the actual number of fractures are the critical variables for the physical production optimization. Such a study is also presented in this paper.
Extended Well Test Facility Unlocks Tight gas Resources in The Sultanate of Oman
Authors: Adil Imtiaz , Husain Ali , Al Shidhani Ruqia , Al Lawati Hussain , Chowdhury Ahmed
Published: January 2013

BP installed an extended well testing (EWT) facility to perform extended flow tests for appraisal of the tight gas reservoirs in the Sultanate of Oman. The EWT facility is a "mini-gas-plant" that processes appraisal well gas and delivers it into the national grid. It helps avoid excessive flaring of significant volumes of gas while providing valuable long term history matching data used to predict full field production profiles.

Middle East tight gas reservoirs are typically Pre-Cambrian to Ordivician in age situated in a high pressure and high temperature environment. A comparatively complex diagenetic history makes prediction of rock quality and fluid distribution very challenging. Key depletion planning uncertainties identified at the outset of appraisal were: the long term decline in gas production rates, the connected hydrocarbon volumes, the impact of condensate banking and the long term trends in water gas ratios. The EWT data gathering is helping to reduce these uncertainties to a level sufficient to inform an investment decision.

Four appraisal wells, ranging from good to poor quality, were tied into the EWT for long term testing for up to 2 years to date. The combination of this production history and downhole pressure data has markedly improves confidence in predictions of production profiles for the range of full field development wells.

The EWT operations have also revealed several potential full field development design and startup concerns. These were related to formation of hydrates due to gas expansion at the wellhead along with other potential integrity risks due to high chlorides content and the presence of minor H2S levels. The changing fluid chemistry was also identified which helped in redefining the fluid basis of surface facilities design to optimize operability of the full field development.
Water and Bromide Dynamics in a Soil Amended with Different Urban Composts
Authors: Chalhoub Maha , Coquet Yves , Vachier Pierre
Published: January 2013

Urban waste compost additions to soil can increase soil organic matter content and improve soil physical conditions, leading to agronomic and environmental benefits. The need for information still exists to evaluate more precisely the effects of urban waste compost on soil physical properties. Three types of urban waste composts, a biowaste compost (BIO), a municipal solid waste compost (MSW), and a co‐compost of green waste and sewage sludge (GWS), were applied once every 2 yr on a loamy soil for 10 yr. The effects of the three composts on soil water and solute transport dynamics were tested. Soil water matric head and water content were monitored using tensiometers and time domain reflectometry probes, respectively. A Br− tracer experiment was also conducted to evaluate the effect of compost application on nonsorbing solute transport. Water content measurements showed that the application of composts significantly (P < 0.05) affected soil water content in the plow layer, with average increases of 0.03 cm3 cm−3 for the GWS and MSW compost, and 0.015 cm3 cm−3 for the BIO compost compared with a control without organic amendment. Bromide tracing during the wetting period showed that the application of urban waste composts did not affect the soil's potential for leaching. The application of composts did reduce soil evaporation during the spring, however, which in turn favored downward Br− migration in the soil.
Global Automated Quality Control of In Situ Soil Moisture Data from the International Soil Moisture Network
Authors: Dorigo W.A. , Xaver A. , Vreugdenhil M. , Gruber A. , Hegyiová A. , Sanchis-Dufau A.D. , Zamojski D. , Cordes C. , Wagner W. , Drusch M.
Published: January 2013

The International Soil Moisture Network (ISMN) was initiated in 2009 to support calibration and validation of remote sensing products and land surface models, and to facilitate studying the behavior of our climate over space and time. The ISMN does this by collecting and harmonizing soil moisture data sets from a large variety of individually operating networks and making them available through a centralized data portal. Due to the diversity of climatological conditions covered by the stations and differences in measurement devices and setup, the quality of the measurements is highly variable. Therefore, appropriate quality characterization is desirable for a correct use of the data sets. This study presents a new, automated quality control system for soil moisture measurements contained in the ISMN. Two types of quality control procedures are presented. The first category is based on the geophysical dynamic range and consistency of the measurements. It includes flagging values exceeding a certain threshold and checking the validity of soil moisture variations in relation to changes in soil temperature and precipitation. In particular, the usability of global model‐ or remote sensing–based temperature and precipitation data sets were tested for this purpose as an alternative to in situ measurements, which are often not recorded at the soil moisture sites themselves. The second category of procedures analyzes the shape of the soil moisture time series to detect outliers (spikes), positive and negative breaks, saturation of the signal, and unresponsive sensors. All methods were first validated and then applied to all the data sets currently contained in the ISMN. A validation example of an AMSR‐E satellite and a GLDAS‐Noah model product showed a small but positive impact of the flagging. On the basis of the positive results of this study we will add the flags as a standard attribute to all soil moisture measurements contained in the ISMN.
Multiscale finite element coarse spaces for the application to linear elasticity
Authors: Buck Marco , Iliev Oleg , Andrä Heiko
Published: January 2013

We extend the multiscale finite element method (MsFEM) as formulated by Hou and Wu in [Hou T.Y., Wu X.-H., A multiscale finite element method for elliptic problems in composite materials and porous media, J. Comput. Phys., 1997, 134(1), 169–189] to the PDE system of linear elasticity. The application, motivated by the multiscale analysis of highly heterogeneous composite materials, is twofold. Resolving the heterogeneities on the finest scale, we utilize the linear MsFEM basis for the construction of robust coarse spaces in the context of two-level overlapping domain decomposition preconditioners. We motivate and explain the construction and show that the constructed multiscale coarse space contains all the rigid body modes. Under the assumption that the material jumps are isolated, that is they occur only in the interior of the coarse grid elements, our numerical experiments show uniform convergence rates independent of the contrast in Young’s modulus within the heterogeneous material. Elsewise, if no restrictions on the position of the high coefficient inclusions are imposed, robustness cannot be guaranteed any more. These results justify expectations to obtain coefficient-explicit condition number bounds for the PDE system of linear elasticity similar to existing ones for scalar elliptic PDEs as given in the work of Graham, Lechner and Scheichl [Graham I.G., Lechner P.O., Scheichl R., Domain decomposition for multiscale PDEs, Numer. Math., 2007, 106(4), 589–626]. Furthermore, we numerically observe the properties of the MsFEM coarse space for linear elasticity in an upscaling framework. Therefore, we present experimental results showing the approximation errors of the multiscale coarse space w.r.t. the fine-scale solution.
Independence of the axiomatic system for MV-algebras
Authors: Kolařík Miroslav
Published: January 2013

We prove that the well-known axiomatic system of MV-algebras is not independent. The axiom of commutativity can be deleted and the remaining axioms are shown to be independent.
An extended Stickelberger ideal of the compositum of a bicyclic field and an imaginary quadratic field
Authors: Trnková Veronika
Published: January 2013

We consider certain extension of the Stickelberger ideal of the compositum of a bicyclic field and a quadratic imaginary field, obtained by adding new annihilators to the Stickelberger ideal. We compute the index of this extension, from which we get some divisibility properties for the relative class number of the compositum.
Properties of transformation matrices between the normal bases in orders of cubic field
Authors: Divišová-Václavíková Zuzana
Published: January 2013

In this paper, the properties of transformation matrices between the normal bases in orders of algebraic number fields of degree 3 are shown.
Influence of In2O3 Addition On The Magnetic And Electrical Properties of Iron  Deficient Ni-Zn Ferrite
Authors: Akhter Shireen , Choudhury Md Amanullah , Rahman J
Published: January 2013

The influence of low melting In2O3 addition on the magnetic and electrical properties of irondeficient  ferrites of composition. Ni0.65Zn0.35Fe1.96O4 + xIn2O3(x = 0, 0.005, 0.01, 0.015, 0.02,  0.025, 0.03 and 0.035) was investigated. Single phase spinel structure of all sintered samples were  confirmed by X-ray diffraction. The lattice parameter of the samples increased with the increment  of In2O3. The effect of In2O3 (melting point 680°C) can be explained by the formation of liquid  phase on the grain surface due to reaction of In2O3 with the spinel phase at 1250°C sintering  temperature. Saturation magnetization decreased almost linearly and Curie temperature linearly  with the increasing addition of In2O3. The decrease in magnetization was possibly due to diamagnetic In3+ ions occupy B-sublattice ( octahedral sites) and replace Fe3+ ions keeping the  magnetization of A-sublattice (tetrahedral sites) unchanged. When indium ions occupy B-sites and  replace Fe3+ ions, the magnetization of B-sublattice (MB) decreases keeping the magnetization of  A-sublattice (MA) constant which in turn weakens A-B exchange interaction (M = MB-MA). The dc  resistivity of the samples increased almost linearly with the addition of In2O3. With the increasing  addition of In2O3, In3+ ions occupy B-sites which reduces Fe2+ to Fe3+ electron hoping conduction  in octahedral sites and contributes to increase in resistivity. DOI: http://dx.doi.org/10.3329/jbas.v36i2.12957 Journal of Bangladesh Academy of Sciences, Vol. 36, No. 2, 153-158, 2012