bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Socioeconomic Distribution of Adult Mortality during Conflicts in Africa
Authors: De Walque Damien , Filmer Deon 
Published: December 2012

Abstract
We analyze socioeconomic differences in adult mortality in four African countries-the Democratic Republic of Congo, Ethiopia, Rwanda and Sierra Leone-using the adult mortality module in the Demographic and Health Surveys (DHS), calculating mortality based on the sibling mortality reports collected from female respondents aged 15-49. We discuss the advantages and potential issues associated with this data source. While mortality events precipitated by those civil conflicts tend to affect all groups, we conclude that they appear to affect men, and in particular urban and more educated men to a greater extent than the other groups.
In vivo flow cytometry: A powerful optical technology to detect circulating tumor cells and diagnose cancer metastasis in vivo/In-vivo-Durchflusszytometrie: Ein leistungsstarkes optisches Verfahren zur Detektion zirkulierender Tumorzellen und zur In-vivo-Diagnose von Metastasen
Authors: Fan Zhichao , Wei Xunbin 
Published: December 2012

AbstractOptical methods have revolutionized medical diagnoses, therapies and research, and have penetrated many medical disciplines for example, tumor diagnosis and treatment. Tumor recurrence and metastasis are the major obstacles for long-term survival in cancer. The metastasis is reported to be correlated with the presence of circulating tumor cells (CTCs) in the vasculature as a consequence of either advanced tumor growth and invasion, or a therapeutic intervention. Thus, CTCs are considered to be important biomarkers for cancer progress and prognosis. The quantification of CTCs is an emerging tool used to diagnose, stratify and monitor patients with metastatic diseases. A number of methods have been developed to detect CTCs, some of which have been applied in clinical diagnosis. However, conventional methods are restricted by invasiveness, lower sensitivity caused by small blood sample volumes, and difficulty in recording the dynamics of CTCs. A novel technique named
PRORETA 3: An Integrated Approach to Collision Avoidance and Vehicle Automation
Authors: Bauer Eric , Lotz Felix , Pfromm Matthias , Schreier Matthias , Abendroth Bettina , Cieler Stephan , Eckert Alfred , Hohm Andree , Lüke Stefan , Rieth Peter , Willert Volker , Adamy Jürgen 
Published: December 2012

Zusammenfassung
The article describes first results of the research project PRORETA 3 that aims at the development of an integral driver assistance system for collision avoidance and automated vehicle guidance based on a modular system architecture. For this purpose, relevant information is extracted from a dense environment model and fed into a potential field-based trajectory planner that calculates reference signals for underlying vehicle controllers. In addition, the driver is supported by a human-machine interface.
Die Entstehung des modernen Unternehmens: Einführende Bemerkungen
Authors: Banken Ralf 
Published: December 2012

Abstract
The article investigates two issues, currently widely neglected: the fact that enterprises did not become the dominant form of organisation for the production of goods and services in western economies until after 1800; and that these institutions did not play a major role in the Early Modern Age. It argues that the understanding of modern enterprises as industrial-technical organisations and the production of machinery as the sole cause for the evolvement of modern companies – which has dominated up until now – as lacking, as numerous service companies had already developed in the early phase of industrialisation. Based on a functional concept of enterprises, the article attributes the early modern proto-enterprises a major role before 1800 and elaborates on what conditions were necessary to allow for the plentiful occurrence of modern enterprises in the phase of early industrialisation. In so doing it elucidates a clearer understanding of how modern enterprises institutionalised over time.
Dance and the Female Singer in Second Empire Opera
Authors: Parr Sean M. 
Published: December 2012

Abstract
A vogue for coloratura dance arias began in the 1850s. This emerging genre combined melismatic singing with two hugely popular social dance genres: the bolero and the waltz. Scholars have observed an association between these social dances and a certain euphoric feminine sensuality, but the connection between this youthful ebullience in dance and virtuosic female vocality has been largely ignored. Dancing was notorious in the nineteenth century because of its dangerously arousing and vertiginous effects. As dances increased in speed and difficulty, so too did the singing of sopranos in midcentury Paris. In exploring relationships between dance, femininity, and singing, this article situates coloratura dance arias in the Paris of Napoléon III's Second Empire, a city sometimes condemned for its decadent materialism or dismissed because of its political impotence, in spite of its cultural, architectural, and technological importance.
I argue for a connection between coloratura and the female body in precisely the era when the venerable singing style became the almost exclusive domain of the female singer and, simultaneously, reached its apogee in a Paris devoted to all the joy and glamour it could afford. Specific performers such as Marie Cabel and Caroline Carvalho were key to the success and even creation of these dance arias. These sopranos were certainly objectified in a problematic manner, but they were also “envoiced” (Carolyn Abbate's term) as wielders of a compelling musical power: coloratura. In providing virtuosic and luxurious expressions of femininity, these coloratura dance arias established a new sense of female vocality in the aural imagination of the Second Empire.
Modeling Gel Filter Cake Recovery by Flow and Dilution Mechanisms
Authors: Gdanski Rick , Bryant Jason 
Published: December 2012

Abstract
Historical modeling of gel filter cake recovery often predicts relatively fast gel recovery. A common method to slow gel recovery in simulations is to use yield point behavior for the gel filter cake. Recent measurements of concentrated, broken gel exhibited Carreau-type viscosity behavior that could mimic an apparent yield point. A new rheology model built on those measurements was used to upgrade a fracture cleanup and chemistry simulator (FCCS) to study potential cleanup mechanisms of gel filter cake during flowback of fracturing treatments.
Two cleanup mechanisms were explored with the FCCS. The first was a simple dilution mechanism in which the gel filter cake was immediately diluted as water re-entered the proppant pack from the matrix. The method used two-phase flow modeling and predicted excellent cleanup of delinked borate filter cakes and high concentrations of gelling agents in the return fluids—a prediction not observed in well returns. The second mechanism required development of three-phase relative permeability curves for water, gel filter cake, and gas phases in the proppant pack. The simulation studies using this mechanism only modeled displacement cleanup and predicted poor recovery as a result of a combination of filter cake rheology and relative permeability. This affirmed the poor apparent cleanup of some fracturing treatments, but underestimated return gelling agent concentration. The studies also demonstrated the role of gel phase saturation on gas productivity.
This work demonstrates that a proper choice of the operative three-phase relative permeability curves for water, gel filter cake, and gas is important for constraining the premature return of gel filter cake in cleanup simulators. Future laboratory work should consider the direct measurement of the three-phase relative permeability curves in proppant packs.
Predicting Well Performance in Complex Fracture Systems by Slab Source Method
Authors: Lin Jiajing , Zhu Ding 
Published: December 2012

Abstract
Multiple hydraulic fracture treatments in reservoirs with natural fractures create complex fracture networks. Predicting well performance in such a complex fracture network system is an extreme challenge. The statistical nature of natural fracture networks changes the flow characteristics from that of a single linear fracture. Simply using single linear fracture models for individual fractures, and then summing the flow from each fracture as the total flow rate for the network could introduce significant error. In this paper we present a semi-analytical model by a source method to estimate well performance in a complex fracture network system. The method simulates complex fracture systems in a more reasonable approach. We statistically assigned a fracture network of natural fractures, based on the spacing between fractures and fracture geometry. We then added multiple dominating hydraulic fractures to the natural fracture system. Each of the hydraulic fractures is connected to the horizontal wellbore, and some of the natural fractures are connected to the hydraulic fractures through the network description. Each fracture, natural or hydraulically induced, is treated as a series of slab sources. The analytical solution of superposed slab sources provides the base of the approach, and the overall flow from each fracture and the effect between the fractures are modeled by applying the superposition principle to all of the fractures. The fluid inside the natural fractures flows into the hydraulic fractures, and the fluid of the hydraulic fracture from both the reservoir and the natural fractures flows to the wellbore. The finite conductivity of hydraulic fractures is modeled by additional pressure drop inside the fracture, but it is neglected in natural fractures. This paper also shows that non-Darcy flow effects have an impact on the performance of fractured horizontal wells. In hydraulic fracture calculation, non-Darcy flow can be treated as the reduction of permeability in the fracture to a considerably smaller effective permeability. The reduction is about 2% to 20%, due to non- Darcy flow that can result in a low rate.
The semi-analytical solution presented can be used to efficiently calculate the flow rate of multistage-fractured wells. Examples are used to illustrate the application of the model to evaluate well performance in reservoirs that contain complex fracture networks.
Investigation of Horizontal Well Fracture Extension Pattern Based on Downhole Pressure Data
Authors: Daneshy Ali , Herman Daniel , Tymko Dean 
Published: December 2012

Abstract
This paper presents the results of an investigation into fracture growth pattern in three horizontal wells, each fractured multiple times. The completion system was selected such that it allowed recording of the bottom-hole pressure in two critical locations; at the frac port which was being fractured, and, within the previously fractured part of the same wellbore. Downhole cups isolated the two locations from each other.
The data show remarkable results. All fractures initiated axially and re-oriented to become perpendicular to the minimum principal stress (MPS). The re-orientation details varied widely between different fractures in the same well, and also between wells. In-spite of these variations, there was no communication within the formation between the multiple fractures. All fractures in the same well had the same value of MPS, and in fact nearly the same in all three wells. In one of the wells there was obstruction to proppant movement inside the fracture which caused increasing pressures during fracture extension. In one instance this resulted in screen-out very near the wellbore early in the treatment, and in another case inside the fracture and close to the end of the stage. Still, the high pressures encountered during these fractures did not cause communication with the previous fractures. The growth pattern in all fractures can best be described as off-balance, with no evidence of "complexity".
Resource Evaluation for Shale Gas Reservoirs
Authors: Dong Z. , Holditch S. A. , McVay D. A. 
Published: December 2012

Abstract
Many shale gas reservoirs have been previously thought of as source rocks, but the industry now finds these source rocks still contain large volumes of natural gas and liquids that can be produced using horizontal drilling and hydraulic fracturing. However, one of the most uncertain aspects of shale gas development is our ability to accurately forecast gas resources and shale gas development economics. The uncertainty of the problem begs for a probabilistic solution.
The objective of our work was to develop the data sets, methodology and tools to determine values of original gas in place (OGIP), technically recoverable resources (TRR), recovery factor (RF) and economic viability in highly uncertain and risky shale gas reservoirs. Existing approaches for determining values of TRR, such as the use of decline curves or even volumetric analyses, may not be reliableduring early time because there may not be enough production history for decline curves to work well or the uncertainty in the reservoir properties may be too large for volumetric analyses to be useful.
To achieve our research objective, we developed a computer program, Unconventional Gas Resource Assessment System (UGRAS). In the program, we integrated Monte Carlo technique with an analytical reservoir simulator to estimate the original volume in place, predict production performance and estimate the fraction of TRR that are economically recoverable resources (ERR) for a variety of economic situations. We applied UGRAS to dry gas wells in the Barnett Shale and the Eagle Ford shale to determine the probabilistic distribution of their resource potential and economic viability. Based on our assumptions, the Eagle Ford shale in the dry gas portion of the play has more technically recoverable resources than the Barnett shale. However, the Eagle Ford shale is currently not as profitable as the Barnett shale because of the higher drilling costs in the Eagle Ford dry gas window.
We anticipate that the tools and methodologies developed in this work will be applicable to any shale gas reservoirs that have sufficient data available. These tools should ultimately be able to allow determination of technically and economically recoverable resources from shale gas reservoirs globally.
Acid Fracturing: New Insigths on Acid Etching Patterns from Experimental Investigation
Authors: Neumann L F , de Oliveira e Sousa J L , Brandão E M , Oliveira T J 
Published: December 2012

Abstract
Nowadays, it is commonplace to say that acid fracture conductivity depends on the fracture face asperities. Does it really depend on it? Almost thirty years ago, someone wrote, "We believe the conductivity measured in these tests is mainly due to the smoothing of peaks and valleys on the rough fracture faces, and is independent of rock heterogeneities due to the small sample size." Moreover, almost one year ago, one wrote, "More asperities touch and deform as the closure stress increases. The channels become even shorter and fewer openings are left." Between these two extremes, the asperities came to be pointed out as an essential factor to generate acid conductivity. Many published results from small, wet sawed and leveled carbonate rock samples support such claim. We did the same. Our experimental investigation on small scale carbonate samples with sawn faces, both from outcrops and well cores, reconfirm the existence of three main acid patterns namely uniform, channels and roughness. The design of experimental apparatus prevented that those etching patterns were artifact patterns. The acid etching patterns determine different conductivity behavior under confining stress. However, hydraulic fractures are tensile fractures and they are naturally rough. In nature, there is no such thing as a leveled fracture face. Tensile fracture faces could be rougher than fracture face after acid reaction. In fact, the first experimental results show that after acid reaction, linear roughness of tensile fractures can be larger, equal or less than linear roughness before acid reaction. This paper presents experimental results and discusses the asperities paradigm.
Gas Shale Hydraulic Fracturing: A Numerical Evaluation of the Effect of Geomechanical Parameters
Authors: Nagel Neal B. , Sanchez-Nagel Marisela , Lee Byungtark 
Published: December 2012

Abstract
Due to the low permeability of many shale gas reservoirs, multi-stage horizontal well completions are used to provide sufficient stimulated area to make an economic well. Furthermore, access to, and stimulation of, the natural fracture system is often critical to an economically successful well.
During a given hydraulic fracture stimulation, the physical displacement of the fracture alters the stress field around it. Numerous authors have suggested that this altered stress field is beneficial to the stimulation of the natural fracture system; however, other authors have shown the potential to stabilize the natural fracture system - making it less likely to shear - due to the presence of a created hydraulic fracture.
In this paper, we present the results of a detailed parametric evaluation of the shear failure (and, by analogy, the microseismicity) due to the creation of a hydraulic fracture as a function of fracture length within two different fracture networks (DFNs) using the 2D Distinct Element Model (DEM), UDEC. Simulations were conducted as a function of: 1) fracture strength; 2) DFN orientation within the stress field; 3) stress ratio (the ratio of the maximum horizontal stress to the minimum); 4) Poisson’s ratio of the shale; and 5) Young’s modulus of the shale. The results show the critical impact that changes in the hydraulic fracture length and the DFN orientation have on the shear of the natural fracture system. In contrast, the simulations suggest that stress ratio, Poisson’s ratio, and Young’s modulus have, at best, a second-order effect on the shearing - and likely the stimulation - of the natural fracture system.
The results of the study provide a further, quantitative assessment of the critical parameters affecting shale gas completions and aid in the understanding and optimization of hydraulic fracture stimulations in very low permeability, naturally fractured reservoirs.
Prediction And Optimization Of Fracturing In Tight Gas And Shale Using A Coupled Geomechanical Model Of Combined Tensile And Shear Fracturing
Authors: Nassir Mohammad , Settari Antonin , Wan Richard 
Published: December 2012

Abstract
Hydraulic fracturing is a stimulation technique essential for economical development of tight gas and shale gas reservoirs. Analysis of the performance of fracturing jobs and optimization of the treatment design requires modeling which accounts for all important features of the process and ideally covers both the treatment and post-stimulation production of the well. It is now well established that the productivity of the wells is due not only to the classical tensile single plane fracture (SPF), but to the development of an enhanced permeability region (stimulated reservoir volume or SRV) around it due to shear fracturing and/or stimulation of existing dual porosity. The shape and size of the SRV depends not only on the injection process but also on the geomechanics of the reservoir. Current techniques are not able to predict its dependence on frac job parameters, which precludes any meaningful optimization. Typically the SRV size is assumed (e.g., from microseismic) in production forecasting.
In this work we have developed a new coupled geomechanical and flow model for analysis and optimization of tight and shale gas treatments. The formulation includes the propagation of a tensile (SPF) fracture and dynamic development of the shear failure. Non-fractured blocks are assumed to be of linear elastic material; whereas in the failed blocks, fractures and rock compliance matrices are homogenized to form an equivalent compliance matrix. Simple Mohr-Coulomb and tensile failure relationships were used as the criteria for detecting fracture creation. Hyperbolic functions are used to describe the fracture normal and pre-peak shear deformations while the post-peak shear behavior follows an elasto-plastic model. The permeability enhancement during the fracturing process is computed and is the principal coupling between the flow and geomechanics. The model is 3-dimensional and treats both normal and shear behaviour of fractures. The simulation results reveal that shear fracturing will be the dominant fracturing mechanism in cases where the rock cohesion is low and the deviatoric stress is high, whereas tensile fracturing prevails in other conditions.
The new model will be a realistic tool for analyzing the dependence of the well productivity on design parameters such as stage volume and pumping rate, spacing between stages, etc. It can be also used to screen shale plays for the most favorable geomechanical conditions.
Integrated Methodology for Optimizing Development of Unconventional Gas Resources
Authors: Gupta Jugal K. , Zielonka Matias G. , Albert Richard A. , El-Rabaa Wadood , Burnham Heather A. , Choi Nancy H. 
Published: December 2012

Abstract
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 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.
To this end, ExxonMobil has undertaken a multi-disciplinary approach that integrates fracture characteristics, reservoir production, and evolution of the stress field to design and optimize developments 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 using case studies for two shale gas pads. The study reveals a strong connection between reservoir depletion behavior 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 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. Collective interpretation of completion, reservoir depletion and changes in stresses explained varying performances of wells and enabled evaluation of infill potential on the pad. This workflow 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.