bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct growth of LaMnO3 cap buffer layers on ion-beam-assisted deposition MgO for simplified template-based YBa2Cu3O7−δ-coated conductors
Authors: Polat O. , Aytug T. , Paranthaman M. , Kim K. , Zhang Y. , Thompson J.R. , Christen D.K. , Xiong X. , Selvamanickam V.
Published: October 2008

Simplification of the ion-beam-assisted deposition (IBAD) buffer architecture is one of the key issues for reduced manufacturing cost of second-generation superconducting wire production. In this work, we studied various radio frequency magnetron sputter deposition conditions for epitaxial growth of LaMnO3 (LMO) layers, with varying thicknesses, directly on IBAD-MgO without homo-epitaxial MgO layers. Performance of the simplified LMO/IBAD-MgO samples was qualified by pulsed-laser-deposited 1-μm-thick YBa2Cu3O7−δ (YBCO) coatings. Detailed property characterizations revealed that though the growth temperature has a substantial effect on the texture of LMO layers, neither LMO thickness nor different sputter gas compositions had a significant effect on the performance of YBCO films. The superconducting properties of YBCO on LMO/IBAD-MgO are found to be similar to those obtained on templates having homo-epitaxial MgO layers. The present results underscore the strong potential of LMO as a single cap layer directly on IBAD-MgO for the development of a simplified IBAD architecture.
In situ compression tests on micron-sized silicon pillars by Raman microscopy—Stress measurements and deformation analysis
Authors: Wasmer K. , Wermelinger T. , Bidiville A. , Spolenak R. , Michler J.
Published: October 2008

Mechanical properties of silicon are of high interest to the microelectromechanical systems community as it is the most frequently used structural material. Compression tests on 8 μm diameter silicon pillars were performed under a micro-Raman setup. The uniaxial stress in the micropillars was derived from a load cell mounted on a microindenter and from the Raman peak shift. Stress measurements from the load cell and from the micro-Raman spectrum are in excellent agreement. The average compressive failure strength measured in the middle of the micropillars is 5.1 GPa. Transmission electron microscopy investigation of compressed micropillars showed cracks at the pillar surface or in the core. A correlation between crack formation and dislocation activity was observed. The authors strongly believe that the combination of nanoindentation and micro-Raman spectroscopy allowed detection of cracks prior to failure of the micropillar, which also allowed an estimation of the in-plane stress in the vicinity of the crack tip.
Enhanced luminescence and nonlinear optical properties of nanocomposites of ZnO–Cu
Authors: Irimpan Litty , Nampoori V.P.N. , Radhakrishnan P.
Published: October 2008

In this article, we present the spectral and nonlinear optical properties of ZnO–Cu nanocomposites prepared by colloidal chemical synthesis. The emission consisted of two peaks. The 385-nm ultraviolet (UV) peak is attributed to ZnO and the 550-nm visible peak is attributed to Cu nanocolloids. Obvious enhancement of UV and visible emission of the samples is observed and the strongest UV emission of a typical ZnO–Cu nanocomposite is over three times stronger than that of pure ZnO. Cu acts as a sensitizer and the enhancement of UV emission are caused by excitons formed at the interface between Cu and ZnO. As the volume fraction of Cu increases beyond a particular value, the intensity of the UV peak decreases while the intensity of the visible peak increases, and the strongest visible emission of a typical ZnO–Cu nanocomposite is over ten times stronger than that of pure Cu. The emission mechanism is discussed. Nonlinear optical response of these samples is studied using nanosecond laser pulses from a tunable laser in the wavelength range of 450–650 nm, which includes the surface plasmon absorption (SPA) band. The nonlinear response is wavelength dependent and switching from reverse saturable absorption (RSA) to saturable absorption (SA) has been observed for Cu nanocolloids as the excitation wavelength changes from the low absorption window region to higher absorption regime near the SPA band. However, ZnO colloids and ZnO–Cu nanocomposites exhibit induced absorption at this wavelength. Such a changeover in the sign of the nonlinearity of ZnO–Cu nanocomposites, with respect to Cu nanocolloids, is related to the interplay of plasmon band bleach and optical limiting mechanisms. The SA again changes back to RSA when we move over to the infrared region. The ZnO–Cu nanocomposites show self-defocusing nonlinearity and good nonlinear absorption behavior. The nonlinear refractive index and the nonlinear absorption increases with increasing Cu volume fraction at 532 nm. The observed nonlinear absorption is explained through two-photon absorption followed by weak free-carrier absorption and interband absorption mechanisms. This study is important in identifying the spectral range and composition over which the nonlinear material acts as a RSA-based optical limiter. ZnO–Cu is a potential nanocomposite material for the light emission and for the development of nonlinear optical devices with a relatively small limiting threshold.
Cooperative downconversion luminescence in Pr3+/Yb3+:SiO2–Al2O3–BaF2–GdF3 glasses
Authors: Lakshminarayana G. , Yang Hucheng , Ye Song , Liu Yin , Qiu Jianrong
Published: October 2008

Oxyfluoride aluminosilicate glasses with compositions of 50SiO2–20Al2O3–20BaF2–10GdF3–0.5PrF3–xYbF3(x = 0, 1.0, 2.5, 5, 7.5, 10, 15, 20, 25, and 30 mol%) have been prepared to study their thermal and optical properties. From the differential thermal analysis (DTA) measurement, glass-transition temperatures and onset crystallization temperatures have been evaluated and from them, glass-stability factors against crystallization were calculated. Glass stabilities were decreased gradually with fluoride content increment in all the studied glasses. The photoluminescence and decay measurements have also been carried out for these glasses. In these glasses, an efficient near-infrared (NIR) quantum cutting with optimal quantum efficiency approaching 160% have been demonstrated, by exploring the cooperative downconversion mechanism from Pr3+ to Yb3+ with 481 nm (3P0 → 3H4) excitation wave length. These glasses are promising materials to achieve high-efficiency silicon-base solar cells by means of downconversion in the visible part of the solar spectrum.
Dielectric relaxations, ultrasonic attenuation, and their structure dependence in Sr4(LaxNd1-x)2Ti4Nb6O30 tungsten bronze ceramics
Authors: Zhu Xiao Li , Chen Xiang Ming , Liu Xiao Qiang , Li Xiao Guang
Published: October 2008

The dielectric anomalies and their structure dependence were evaluated and discussed in Sr4(LaxNd1-x)2Ti4Nb6O30 ceramics, together with the analysis of ultrasonic velocity shift and attenuation spectra in the low-temperature range. The room-temperature structure was confirmed as the tetragonal in space group P4bm for all compositions. One diffuse ferroelectric peak and three relaxor ferroelectric peaks corresponding to the commensurate/incommensurate modulation of oxygen octahedra, polar clusters of A-site ion ordering, and B-site ion ordering, respectively, were observed in the composition with x = 0.25. With decreasing the radius difference between A1- and A2-ions (increasing x), the dielectric relaxations, especially the one originating from the polar clusters of A-site ion ordering, tended to increase significantly and overlap the diffuse ferroelectric peak, which was completely overlapped for x ⩾ 0.75. This process just reflected the increased disordering degree of both A- and B-site ions, and the analysis of ultrasonic attenuation strongly supported the above conclusions on dielectric relaxations and their structural origins. The ultrasonic attenuation peak at approximately 100 K corresponded to the freezing process of the dielectric relaxations, and the fluctuation with composition of the ultrasonic attenuation peaks between 150 and 260 K suggested the possible structure variation.
Controlling electromigration to selectively form thin metal wires and metal microspheres
Authors: Saka Masumi , Kato Kei , Tohmyoh Hironori , Sun Yuxin
Published: October 2008

Guidelines for selecting the shape formed by metal discharged from a narrow Al line were developed. By controlling electromigration in the line, either relatively large microspheres, thin wires, or relatively small microspheres could be formed. Our starting point was a passivated polycrystalline Al line with a slit and small holes at the anode end of it. In the discussion, we describe how the temperature of a part of a wire, T*, at the moment when the part is completely discharged from the hole, affects the shape of the microstructural feature formed from the metal. High, intermediate, and low values of T* were found to correspond to the formation of large microspheres, thin wires, and small microspheres, respectively. The experimental results are explained in the discussion.
Image analyses of two crustacean exoskeletons and implications of the exoskeletal microstructure on the mechanical behavior
Authors: Cheng Liang , Wang Liyun , Karlsson Anette M.
Published: October 2008

The microstructures of exoskeletons fromHomarus americanus(American lobster) andCallinectes sapidus(Atlantic blue crab) were investigated to elucidate the mechanical behavior of such biological composites. Image analyses of the cross-sectioned exoskeletons showed that the two species each have three well-defined regions across the cuticle thickness where the two innermost regions (exocuticle and endocuticle) are load bearing. These regions consist of mineralized chitin fibers aligned in layers, where a gradual rotation of the fiber orientation of the layers results in repeating stacks. The exocuticle and endocuticle of the two species have similar morphology, but different thicknesses, number of layers, and number of stacks. Mechanics-based analyses showed that the morphology of the layered structure corresponds to a nearly isotropic structure. The cuticles are inter-stitched with pore canal fibers, running transversely to the layered structure. Mechanics-based analyses suggested that the pore canal fibers increase the interlaminar strength of the exoskeleton.
Synthesis and characterization of multiphase bioactive glass-ceramics in the CaO–MgO–SiO2 system with B2O3 additive
Authors: Chen Xianchun , Wei Yan , Huang Zhongbing , Kang Yunqing , Yin Guangfu
Published: October 2008

A glass-ceramic (GC0) with nominal composition of 51.2% CaO–12.1% MgO–36.7% SiO2 (wt%) was synthesized. Then multiphase glass-ceramics of MGC1 and MGC2 were obtained by adding 1 and 2 wt% B2O3 to GC0 followed by thermal treatment. The bending strength of MGC1 was the highest, about 89.46 MPa, and the coefficient of thermal expansion was 10.67 × 10−6 °C−1, closer to that of Ti–6Al–4V alloy (10.03 × 10−6 °C−1). X-ray diffraction analysis confirmed that MGC1 was predominantly composed of akermanite, merwinite, and small amounts of dicalcium silicate crystalline phases. The bioactivity and cytocompatibility in vitro of MGC1 were detected by investigating the bonelike apatite-formation ability in simulated body fluid (SBF) and osteoblast morphology and viability. The results showed that MGC1 possessed bonelike apatite-formation ability in SBF and could release ionic products to significantly stimulate cell growth and viability. Furthermore, osteoblasts adhered and spread well on MGC1, indicating good bioactivity and potential cytocompatibility.
Time-resolved studies of the order–disorder phase transformations in rare-earth–transition metal intermetallics with 2-17 stoichiometry
Authors: Kostogorova-Beller Y.Y. , Kramer M.J. , Shield J.E.
Published: October 2008

High-temperature order–disorder transformations in R2T17 and R2T17-M-C intermetallics with R = Pr, Sm, Dy, Tb; T = Co, Fe; and M = Zr, Nb were studied utilizing time-resolved synchrotron x-ray diffraction at the Advanced Photon Source (APS) at the U.S. Department of Energy’s Argonne National Laboratory (Argonne, IL). High-energy synchrotron radiation provides intense, highly penetrating x-rays, which are ideal for in situ studies of phase transformations. Alloying additions are used to stabilize formation of metastable phases; their influence on order recovery was investigated. The experimental setup utilized Debye–Scherrer geometry; specimens were heated at a rate of 10 K/min. Full-profile diffraction patterns collected every 10 s were refined in sequence using the Rietveld method to track changes of lattice parameters and phase assemblages during heating. Sharp changes observed in the evolution of temperature-dependent lattice parameters suggested formation of ordered structure via nucleation and growth. Both 2-17 polymorphs co-existed in light and heavy rare-earth systems at high temperatures. The presence of alloying additions in the solid solution greatly influenced long-range order formation.
Synthesis of γ-(Al1-xFex)2O3 solid solutions from oxinate precursors and formation of carbon nanotubes from the solid solutions using methane or ethylene as carbon source
Authors: de Resende Valdirene G. , Cordier Anne , De Grave Eddy , Weibel Alicia , Peigney Alain , da Costa Geraldo M. , Laurent Christophe , Vandenberghe Robert E.
Published: October 2008

This work reports for the first time the synthesis of γ-(Al1-xFex)2O3 solid solutions with a high specific surface area (200-230 m2/g) by the decomposition of metal oxinate [(Al1-xFex)(C9H6ON)3] and investigated the potential of these materials as catalysts for the synthesis of carbon nanotubes by catalytic chemical vapor deposition using methane or ethylene as carbon the source. The nanocomposite powders prepared by reduction in H2-CH4 contain carbon nanotubes (CNTs), which are mostly double-walled but also contain a fair amount of undesirable carbon nanofibers, hollow carbon particles, and metal particles covered by carbon layers. Moreover, abundant metallic particles are observed to cover the surfaces of the matrix grains. By contrast, the nanocomposite powders prepared by reduction in N2-C2H4 are not fully reduced, and the CNTs are much more abundant and homogeneous. However, they are multiwalled CNTs with a significant proportion of defects. The powders were studied by several techniques including Mössbauer spectroscopy and electron microscopy.
Reflexões sobre o magnetismo animal: contribuições para revisão da história da psicologia
Authors: Neubern Maurício da Silva
Published: October 2008

Este artigo procura fornecer subsídios para uma alternativa de compreensão histórica sobre o magnetismo animal, de modo a realçar sua importância na construção da psicologia. Nesse sentido, busca-se enfatizar o papel das instituições e práticas sociais que influenciaram de forma decisiva a condenação desta proposta. Na mesma linha de reflexão, visa-se também destacar algumas das incompatibilidades epistemológicas com o projeto moderno de ciência, que também contribuíram significativamente para a rejeição do magnetismo animal. Por fim, o artigo é concluído com uma reflexão sobre a necessidade de revisão da noção de ciência presente nas referências dominantes da história da psicologia, que, geralmente, restringem-se a questões lineares e metodológicas e desprezam os processos intersubjetivos e sociais que atuam na construção desta área de conhecimento.
Duration of the pre-settlement period of the mangrove crab Ucides cordatus (Decapoda: Ocypodidae) under laboratory conditions
Authors: Ventura Robson , Silva Ubiratã de Assis Teixeira da , Perbiche-Neves Gilmar , Ostrensky Antonio , Boeger Walter Antonio Pereira , Pie Marcio Roberto
Published: October 2008

The goal of the present study was to determine the most appropriate time to release the immatures of Ucides cordatus (Linnaeus) produced in the laboratory into the natural environments. Specifically, the time when the megalopae sought the mangrove sediment to excavate the burrows was determined, as well as the time necessary for their metamorphosis into the first juvenile stage. Results indicated that the megalopae of U. cordatus reared in the laboratory took three to ten days (median = 6) after their molt to excavated burrows in the sediment. The average time for the megalopae to molt into juveniles was 12.6 days (SD = 2.3).
IFATS Collection: Adipose Stromal Cells Adopt a Proangiogenic Phenotype Under the Influence of Hypoxia
Authors: Thangarajah Hariharan , Vial Ivan N. , Chang Edwin , El-Ftesi Samyra , Januszyk Michael , Chang Edward I. , Paterno Josemaria , Neofytou Evgenios , Longaker Michael T. , Gurtner Geoffrey C.
Published: October 2008

Evolving evidence suggests a possible role for adipose stromal cells (ASCs) in adult neovascularization, although the specific cues that stimulate their angiogenic behavior are poorly understood. We evaluated the effect of hypoxia, a central mediator of new blood vessel development within ischemic tissue, on proneovascular ASC functions. Murine ASCs were exposed to normoxia (21% oxygen) or hypoxia (5%, 1% oxygen) for varying lengths of time. Vascular endothelial growth factor (VEGF) secretion by ASCs increased as an inverse function of oxygen tension, with progressively higher VEGF expression at 21%, 5%, and 1% oxygen, respectively. Greater VEGF levels were also associated with longer periods in culture. ASCs were able to migrate towards stromal cell-derived factor (SDF)-1, a chemokine expressed by ischemic tissue, with hypoxia augmenting ASC expression of the SDF-1 receptor (CXCR4) and potentiating ASC migration. In vivo, ASCs demonstrated the capacity to proliferate in response to a hypoxic insult remote from their resident niche, and this was supported by in vitro studies showing increasing ASC proliferation with greater degrees of hypoxia. Hypoxia did not significantly alter the expression of endothelial surface markers by ASCs. However, these cells did assume an endothelial phenotype as evidenced by their ability to tubularize when seeded with differentiated endothelial cells on Matrigel. Taken together, these data suggest that ASCs upregulate their proneovascular activity in response to hypoxia, and may harbor the capacity to home to ischemic tissue and function cooperatively with existing vasculature to promote angiogenesis.
Steel-fibre-reinforced concrete coupling beams subjected to monotonic loading
Authors: Kuang J.S. , Bączkowski B.J.
Published: October 2008

An experimental programme on the monotonic tests of large-scale, steel-fibre-reinforced concrete (SFRC) coupling beams is reported in this paper. The ultimate shear strength and post-peak load behaviour of the beams are investigated with the span-to-depth ratio, shear reinforcement ratio, and steel fibre content in concrete as major parameters. The experimental results indicate that the inclusion of steel fibres in the concrete matrix helps to enhance the post-cracking tensile strength of concrete, thus increasing the shear capacity, and to improve significantly the post-peak load behaviour of the coupling beams, where large deformation can be attained without a substantial loss of shear strength, thus providing high damage tolerance that is required in the cases of seismic actions. The ultimate strengths and post-peak load performance of all SFRC specimens are evaluated and compared with the predictions of the design codes BS 8110 and Eurocode 2.
Ain't no mountain high enough: plant invasions reaching new elevations
Authors: Pauchard Aníbal , Kueffer Christoph , Dietz Hansjörg , Daehler Curtis C , Alexander Jake , Edwards Peter J , Arévalo José Ramón , Cavieres Lohengrin A , Guisan Antoine , Haider Sylvia , Jakobs Gabi , McDougall Keith , Millar Constance I , Naylor Bridgett J , Parks Catherine G , Rew Lisa J , Seipel Tim
Published: October 2008

Most studies of invasive species have been in highly modified, lowland environments, with comparatively little attention directed to less disturbed, high‐elevation environments. However, increasing evidence indicates that plant invasions do occur in these environments, which often have high conservation value and provide important ecosystem services. Over a thousand non‐native species have become established in natural areas at high elevations worldwide, and although many of these are not invasive, some may pose a considerable threat to native mountain ecosystems. Here, we discuss four main drivers that shape plant invasions into high‐elevation habitats: (1) the (pre‐)adaptation of non‐native species to abiotic conditions, (2) natural and anthropogenic disturbances, (3) biotic resistance of the established communities, and (4) propagule pressure. We propose a comprehensive research agenda for tackling the problem of plant invasions into mountain ecosystems, including documentation of mountain invasion patterns at multiple scales, experimental studies, and an assessment of the impacts of non‐native species in these systems. The threat posed to high‐elevation biodiversity by invasive plant species is likely to increase because of globalization and climate change. However, the higher mountains harbor ecosystems where invasion by non‐native species has scarcely begun, and where science and management have the opportunity to respond in time.
High-Performance Freshwater Flocculating Drilling Fluid Helps to Increase Efficiency of Extended Reach Drilling Operations and Cut Costs on Uvat Oilfield
Authors: Samarskiy A. G. , Gasparov S. A. , Terentiev V. M. , Terentev A. G. , Samyshkin S. Y.
Published: October 2008

The traditional drilling fluid of choice in West Siberia is a potassium chloride (KCl) low-solids nondispersed polymer system. The use of KCl has been justified by the need to inhibit smectite-rich clays in the Tertiary and Cretaceous formations. KCl inhibits clay swelling and coagulates dispersive clays and does not impair the rheological and filtration characteristics of a polymer water-based drilling fluid. However, there are a number of concerns about the use of KCl in drilling operations. KCl is used in relatively high concentrations (up to 210 kg/m³), requiring significant logistical resources for delivery and handling of the material, especially on remote ice-road locations. High potassium and chloride ion concentrations can also be considered to be hazardous to the environment.

In recent years, regulators and operators have searched for a more environmentally, operationally, and logistically acceptable water-based mud (WBM). This has resulted in the introduction of a new generation of freshwater-based high-performance drilling fluids (Stawaisz et al. 2002). These fluids rely on polymers for clay flocculation instead of KCl. The use of a flocculating high-performance water-based fluid (HPWBF) in the Uvat Field has allowed significant reduction in fluid volumes, fluid cost, and drilling time, as well as helped to reduce logistical costs and control problems such as downhole losses, hole instability, and drilled solids contamination.
Application of Stochastic Prospect Analysis for Shale Gas Reservoirs
Authors: Harding Nathaniel R.
Published: October 2008

The principles of statistical analysis are well-established, but the development and practical application of scalable stochastic shale gas prospect analysis has remained elusive. Development of this integrated software package stemmed from a desire to quantify risk and uncertainty and create a universal program to easily do so for future prospects. An Excel model with Crystal Ball overlay was used for this design. This analysis is both easily implemented, and operates with the seamless addition of scalable Monte Carlo modeling.

Commercial production is a primary uncertainty in unconventional plays. Deterministic solutions do not reflect the uncertainty associated with input assumptions. This discussion presents a stochastic assessment program to evaluate the full range of commercial realization potential. The distinctive aspect is the use of stochastic simulation to calculate the risks of failure and the uncertainty of success for any or all project stages on the basis of subsurface and surface activity performance, cost and duration uncertainties. Land divestitures or acquisitions, monetization, seismic, etc may be modeled.

The results present economic, production, reserves and other performance indicators consistent with commercial software applications, with the additional insight of quantified statistical success uncertainty and failure risk, yielding probabilistic results with associated degrees of confidence. Further work is required to adapt this method for oil reservoirs, and to model tax structures outside of the US. Project-level application is illustrated using a case study from a US shale gas resource play.

This original analysis enables real-world, universal, repeatable application of well-established but theoretical stochastic prospect analysis. Practical application is now possible in-house, and is therefore user-friendly and customizable. Both inputs and outputs will be familiar to any engineer who uses commercial economic analysis software. Most of all, the ability to test the uncertainty of any input or output for any or all project stages grants unparalleled flexibility.
Evolution of Hydraulic Fracturing in Russia
Authors: Pongratz R. , Kuvshinov I. K. , Latkin K. E.
Published: October 2008

Before the mid-1990s, the main goal of hydraulic-fracturing operations in Russia was preventing near wellbore damage. Typical fracturing treatments used a crosslinked polymer-based gel as carrier fluid to place 5 to 20 MT of proppant into the formation. Because of the results, a new phase started, whereby "real" production enhancement treatments achieving skins of well beyond −4 were pumped with proppant volumes from 50 to over 100 MT. Because of Russian oil production practices at the time, it became apparent that the hydraulic fracturing technology combined with drilling horizontal wells increased production and was therefore beneficial to the Russian economy.

When the optimization process started, quality control in the field became mandatory in addition to an enhanced focus on health, safety and environment. Service companies focused on cleaner fluids with less polymer loadings and better breaker systems. Prejob, on-the-job, and postjob quality control procedures were developed specifically for the Russian environment and reached a standard unlike anywhere else in the world. The number of unwanted screenouts was reduced significantly by following proper perforating practices and optimizing the treatments designs in real time. The new goal was a skin of −5, and the design process was optimized to achieve this number by designing each job to achieve optimum production for the given reservoir parameters, especially permeability. Treatments of 300-400 MT are not uncommon these days for low permeability reservoirs with a large reservoir height sometimes covering several zones.

This lead to the optimization process that is currently practiced. Because many sandstone reservoirs, particularly in Siberia, are laminated, the vertical permeability is often an order of magnitude or more lower than compared to the horizontal permeability. Several times, horizontal wells did not yield the expected results. Hydraulic fracturing treatments placed in the horizontal wellbore can be the solution for further production optimization. This paper describes how this can be established through several techniques.

Hydraulic fracturing includes propped hydraulic fracturing in both oil and gas reservoirs, as well as carbonate fracture acidizing. This paper discusses propped hydraulic fracturing in oil reservoirs. Covering propped hydraulic fracturing in gas reservoirs, although still at the beginning stages, could reveal enough material for a paper on its own. However, carbonate fracture acidizing is not frequently used.
Testing and Design of Hydraulic Fractures in Tight Gas Formations
Authors: Soliman M. Y. , East Loyd , Ansah Joe , Wang Hong (Max)
Published: October 2008

Productivity of a tight gas formation is strongly tied to flow area. This fact dictates the creation of enhanced flow area through drilling of multi-lateral wells and/or fracturing.

In the case of fracturing, loss of fracture conductivity near the wellbore can have a drastic and negative effect on the productivity of a fractured well. This is especially true when creating a transverse fracture to intersect a horizontal well. In tight formations, loss of communication between the fracture and the formation could also have a devastating effect on productivity of the well, vertical or horizontal.

In this paper, the following will be discussed:

The effect of completion methodology on productivity of a tight gas formation The effect of near-wellbore damage of fracture conductivity on productivity of a fractured well in a tight gas formation The effect of creating multiple fractures on the productivity of wells Testing a previously fractured well using an injection falloff test, or a pressure buildup test to determine the degree of damage (DED) and depth of damage (DOD) of the fracture conductivity
A Field-Proven Methodology for Real-Time Drill Bit Condition Assessment and Drilling Performance Optimization
Authors: Salakhov Tagir R. , Yamaliev Vil U. , Dubinsky Vladimir
Published: October 2008

The primary objective of the proposed method is to evaluate the current conditions of the drilling system and suggest modifying values of main drilling control parameters to optimize the efficiency of the drilling in whole, while reducing the probability of premature wear of the drill bit.

The fundamental theory behind the proposed approach is based on some elements of fractal analysis as well as artificial neural networks (NN). Many different complicated multi-parameter systems, including drilling systems, frequently discover scale invariance, or "fractality" of spatial-time properties. On this basis, some common engineering approaches to modeling and diagnostic methods have been developed and used.

In our case, the "system" consists of the drilling components (e.g., surface equipment, drillstring, drill bit, mud, etc.), as well as the formation being drilled. Drilling control parameters include both the parameters adjustable in real-time, such as hook load, RPM, or mud flow rate, as well as those that can be modified with some delay (e.g., mud properties or configuration of the bottom-hole assembly).

We consider specific examples of operational situations accompanying the drilling process, in which the fractal performances’ application allows receiving important practical information during a standard operation, i.e., without carrying out a special controlled field experiment.

We present some field examples that we used for gathering required data, training our model, and making an assessment of the current state of the system (specifically, the drill bit conditions) by using the proposed methodology. We also present the results of monitoring the system's response to specific adjustments of control parameters’ values for these cases.

We believe that the proposed methodology opens new opportunities for real-time drilling optimization that can be efficiently implemented within the scope of the existing drilling practice.
Oil Production and Water-Cut in Naturally-Fractured Vuggy Reservoirs
Authors: Li Yangfan , Lin Tao , Li Xinyong , Liu Bo , Ren Xianghai , Li Kewen
Published: October 2008

Naturally fractured oil reservoirs with vugs of size over 5 meters in diameter are few in the world. We developed a method to correlate the decrease in oil production and the increase in water cut. Production data from Tah oil reservoir (China) with big size vugs and high-density fractures were used to test the approach. It was found that the oil production decline and the water cut increase were coupled closely in many wells from this naturally fractured vuggy oil reservoir. The oil production was characteristic of rapid decline and the water cut was characteristic of sharp increase right after water breakthrough in many oil wells. An idea of shutting off water before water enters the production zone was proposed to reduce the decline rate of oil production and the increase in water cut. This approach of water shut off has many advantages compared to the routine measures which are usually taken after water cut is already great.
Technical, Economic and Risk Analysis for a Multilateral Well
Authors: Arcos D. , Zhu D. , Bickel E.
Published: October 2008

Multilateral well technology is considered a development strategy as the oil and gas industry is increasingly approaching more hostile environments. It remains attractive to maintain efficient exploration of oil and gas fields in order to maximize profitability with minimum uncertainty. Some of the non-conventional oil and gas reservoirs currently being drilled are characterized by significant heterogeneity, tight and naturally fractured, faulted/compartmentalized, heavy oil and, depleted reservoirs/mature development. However, sometimes the high risk involved accompanied by economic disadvantages have diminished the ability of multilateral wells to maximize access to reserves without incurring higher development costs.

The objective of this study is to develop a methodology to assist engineers in their decision making process of maximizing access to reserves. The process encompasses technical, economic and risk analysis of various alternatives in the completion of a well (vertical, horizontal or multilateral) by using a well performance model for technical evaluation, and a deterministic analysis for economic and risk assessment.

In the technical part of the decision making process, the flow rate for a defined reservoir is estimated by using a pseudo-steady state flow regime assumption. The economic analysis departs from the utilization of that flow rate data assuming certain pressure decline. Financial Cash Flows (FCF) are generated to measure the economic worth of investment proposals. Net Present Value (NPV), Internal Rate of Return, Profitability Index and payback period are the main economic yardsticks used in the analysis.

Last, a deterministic decision tree is used to represent the risks inherent in geological uncertainty, reservoir engineering, drilling, and completion for a particular well. The NPV generated from the economic analysis is used as the base economic indicator. In addition, the risk associated at each stage of the project is considered with an assigned probability. By selecting a type of well that maximizes the expected monetary value (EMV) in a decision tree, we can make the best decision based on a thorough understanding of the prospect.

The method introduced in the paper emphasizes the importance of a multi-discipline concept in drilling, completion and production technology. The examples presented in the paper will assist geologists, geoscientists, engineers, and managers in collaborating together in a development project.
Unique and Successful Recompletion of Well Kumkol South 1005, Kazakhstan
Authors: Yermakhanov U. , Louviere W. T. , Qingguang Q. , van Gijtenbeek K.
Published: October 2008

The Kumkol South 1005 well was originally drilled and completed in the Cretaceous formation at a depth just above 1100 meters with a 168-mm casing. After watering out, the Cretaceous perforations were squeezed off and the well was deepened to the Jurassic sands with an 89-mm liner set to isolate the upper formation. The well was then completed as a producer in the upper Jurassic formation.

The recompleted well was considered to be a good candidate for a hydraulic proppant fracturing treatment. However, although the liner overlap of the 89 mm into the 168-mm casing had been pressure tested after being cemented in, there was still concern that the applied pressure during a fracturing treatment could result in communication with the Cretaceous formation, which is a formation with a very high water-production rate.

The liner overlap was pressure isolated using a specially constructed mandrel with seal elements identical to what was being used at the end of a wellhead isolation tool. This assembly was run below a retrievable packer assembly. This unique pack-off allowed the Jurassic formation to be successfully treated by means of a hydraulic proppant frac without establishing any communication with the Cretaceous formation. This procedure has been successfully used on several other similar deepened wells in the same field.
Use of Representative Models to Improve the Decision Making Process of Chemical Flooding in a Mature Field
Authors: Costa Ana Paula A. , Schiozer Denis J. , Moczydlower Priscila , Bedrikovetsky Pavel
Published: October 2008

Decision analysis applied to petroleum field development is always strongly related to risk due to uncertainties in the process. An important part of risk evaluation can be accomplished through the evaluation of the impact of uncertainties in the performance of the petroleum fields, yielding higher possibility of success, quantification of possible losses, minimization of sub-optimal development and identification of opportunities.

The objective of the present work is to use the quantification of the impact of uncertainties related to chemical flooding (injection of Alkali-surfactant-polymer) using the concept of Representative Models (RM) integrated with economic uncertainties to improve the production forecast in a Brazilian onshore field with 19 years of production history. The main advantage of this process is to provide a few adjusted models (RM) which are selected based on the integration of objective functions previously defined to the context to represent these uncertainties. These RM are selected to represent all combined models which compose the distribution curve (risk curve) of the process. The distribution curve is obtained through the concept of derivative tree technique, combining the possible scenarios using the numerical simulation to predict the reservoir behavior. The numerical simulation is used to give more reliability to the process and to give a detailed analysis for each model in order to provide integration with economic analysis which is used in the risk mitigation. The importance of this process is to provide a detailed analysis of the impact of the chemical injection in the decision making process. An automated tool and the utilization of a defined methodology to quantify the impact of uncertainties are used to speedup the process and to improve the viability of the procedure with a significant reduction of time and effort, yielding greater reliability of the production forecast with the improvement of the decision making process.
Field Validation Processes for Multiphase Wet Gas Surface Well Testing Solutions: Example from the Yamburgskoe Arctic Gas Condensate Field, Russia
Authors: Theuveny B. , Shumakov Y. , Zhandin A. , Zinchenko I.
Published: October 2008

Surface welltesting of Gas-Condensate with multiphase flowmeters is still considered a challenge for production metering. Traditional means of well testing have been deployed for years and used consistently for reservoir and production management. However, it can be difficult to compare data sets obtained with different measurement devices.

Multiphase flow meters have been proved for multiphase production metering by many operation companies worldwide. However, in artic environmental conditions like those of Yamburgskoe gas-condensate field, with low ambient temperature and production rate regulation restrictions, this process had to be revalidated and the operational capabilities confirmed with all of the logistical challenge of this environment. A number of recommendations to prevent and mitigate the impact of the hydrate and document major benefits of multiphase well testing are based on the accumulated operational experience from the operations of various multiphase flowmeters in the area.

Most of the gas condensate wells in the Yamburgskoe gas-condensate field are flowing with liquid unloading issues in a slug flow regime that can be observed and monitored accurately with multiphase flow meters. The importance of slug flow regime identification relates to the selection of stable flow intervals for surface sampling and further recombination factor determination. This information is also extremely important for well completion design. There is good agreement between the slug frequencies obtained with nodal simulations and the actual dynamic measurements from the meter - an impossible task for conventional measurements based on separator or batch processing of the liquid.

Surface well testing to control changes of reservoir parameters, PVT composition, and production back-allocation performance is one of the key parts of gas-condensate field development in Russia. A number of multiphase welltesting operations have been successfully performed recently that show acceptable performance capability and the benefits of this methodology compared to the parallel production measurement with a traditional gas separator. This novel comparison and qualification process of multiphase flow meters also provides a better understanding of the aptitude of conventional means to collect rate in the case of wet gas wells in Northern Siberia.
TELEMEDICINE in O&G Industry: Our Experience
Authors: Mortara S. , Uberti F. , Gomez G.
Published: October 2008

The activities in Oil & gas industries have always been developed in remote and isolated locations especially in countries where health and hygiene conditions are very poor with difficult access to the advanced medical resources.

The constant development of communication systems allows the implementation of technological resources that maintain the communication between these remote locations with the most advanced hospitals, crossing the world in seconds and providing accurate diagnosis and guidelines for treatments.

Several solutions can be found on the market to help the physician to communicate with a colleague: all of them are valid in specific situations. We will firstly distinguish between vertical and horizontal solutions.

"Vertical" relates to platforms dedicated to medical tele-consultation in individual speciailties: teleradiology, tele-cardiology, tele-pathology, tele-dermatology.

"Horizontal" solutions: All systems that can manage any kind of medical data are grouped under this category: Telephone and fax; Videoconferencing (VC) systems and E-mail messages

The technological and organisational activation of the requesting health centres is a critical factor of success, from the technological viewpoint, a dominant element is connectivity.

Our tele consultation system has been utilised to date by Eni in remote places has provided:

– Support to the doctor with the diagnosis and treatment of routine complaints; – High quality medical assistance in more difficult remote sites, thereby contributing to improve the living conditions of expatriates and local employees; – New approach to handling emergencies, so as to reduce the number of assisted repatriations; – General improvement of healthcare in remote areas.
Sampling with Multiphase Flowmeter in Northern Siberia - Condensate Field Experience and Sensitivities
Authors: Afanasyev Vitaliy , Theuveny Bertrand , Jayawardane Sylvain , Zhandin Alexander , Bastos Vlamir , Guieze Paul , Kulyatin Oleg , Romashkin Sergey
Published: October 2008

Multiphase well testing has been acknowledged worldwide as a state-of-the-art technology for metering stream of oil, gas and water without prior phase separation, and provides in many cases much more accurate picture of the transient evolution of flow and more accurate picture of the volumes and rates especially in cases of condensate and heavy oil environment, where traditional means of measurements are impaired by the difficulty to separate the phases. Furthermore, in-line multiphase flowmetering brings significant benefits to the ease of deployment, especially in harsh regions such as the one encountered in Northern Siberia.

One of the past challenges of multiphase well testing has been the ability to collect representative fluid samples for analysis. The paper presents a solution to this problem and results obtained in number of well tests performed in Russia, complemented with experiences from operations in other countries.

This paper documents new type of sampling device that allows collection of samples, determination of in-situ volumetric ratios and determination of dry gas properties that can minimize an uncertainty propagated by the incorrect input of key fluid parameters in the computation algorithm of multiphase flowmeter.

Not only does this state-of-the-art device allows to capture fluid samples bridging the gap in fluid sampling in a multiphase environment but also supplements for carrying out real-time compositional analysis and basic Pressure-Volume-Temperature (PVT) measurements at wellsite, allowing to compute improved flow rates with MPFM. Hence it provisions two major tasks: the fluid sampling, required for any type of well testing to optimize well tests, and capture of samples for further analyses in a PVT laboratorf after sample recombination using improved phase ratios.

The paper describes deployment of such methodology in Northern Siberia in condensate well tests and offers a number of comparison tests against traditional well testing and fluid analysis methodologies. A recap of lessons learnt captures the best practices of the methodology to ensure optimized utilization of the technique.

The paper focuses on the sampling and fluid analysis aspects and utilization of the fluid information for multiphase well testing. The consistency of the multiprate well test information is not covered in still paper, as the analysis of some condensate to gas ratio between chokes is still ongoing at this stage and will be presented in a separate article.
Structure Features of the Paleozoic Complex of East Siberia Based on Results of Complex Seismic and Well Log Data Interpretation
Authors: Nagaeva Indira , Ahunyanova Elmira
Published: October 2008

In this work, a complex approach to studying a Paleozoic base structure of the East Siberian plate is considered. The area of research is dated to the Nurol trough in the tectonical plane, and despite a significant level of exploration maturity by various geophysical methods and drilling, there are many questions and unresolved problems.

Even a question as to correct mapping of pre-Jurassic surface remained opened until now as the roof of a Paleozoic section is changed by a paleodenudation so that the acoustic properties come nearer to the horizons of the bottom Jurassic complex. Also a seismic picture is complicated by a great number of various amplitude and extent tectonic deformations and the phenomenon of an interference connected with discordant bedding of the Jurassic sedimentary formation on the Paleozoic base.

To create an authentic geological model of reservoir structure, detailed interpretation of 3D seismic data combined with geophysical logging data was required. This interpretation includes structural, paleotectonical, seismic, and facial and dynamic analysis of the data being interpreted. The results of the analysis relate a certain regularity in forming a Paleozoic complex and reveal the most prospective areas of oil deposits.