bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystal structure of the metal-rich phosphide Sm15Ir33P26
Authors: Pfannenschmidt Ulrike , Rodewald Ute Ch. , Pöttgen Rainer 
Published: July 2010

Abstract
The new metal-rich phosphide Sm15Ir33P26 was obtained from a reaction of the elements in a lead flux (1 : 2 : 2 : 30 molar ratio, 1370 K, slow cooling rate). Sm15Ir33P26 adopts a new structure type which was characterized by powder and single crystal X-ray data: C2/m, a = 4720.6(8), b = 392.87(9), c = 1329.2(2) pm, β = 95.478(1)°, wR2 = 0.0376, 3757 F
2 values and 227 variables. The iridium and phosphorus atoms build up a complex three-dimensional [Ir33P26]
δ– polyanionic network in which the samarium atoms fill diverse larger cavities with coordination numbers of 15–17. The seventeen crystallographically independent iridium atoms have between 3 or 4 phosphorus neighbors in distorted trigonal-, square-planar, or tetrahedral coordination. All phosphorus atoms are isolated and most of them fill tri-capped trigonal prisms. The Sm15Ir33P26 structure is an intergrowth variant of ThCr2Si2, SrPtSb, CeMg2Si2, and TiNiSi-related slabs.
Confidentiality and Physicians' Health. A Cross‐sectional Study of University Hospital Physicians in Four European Cities (the HOUPE‐study)
Authors: Løvseth Lise Tevik , Aasland Olaf Gjerl⊘w , Fridner Ann , Jónsdottir Lilja Sigrun , Marini Massimo , Linaker Olav Morten 
Published: July 2010

Confidentiality and Physicians' Health. A Cross‐sectional Study of University Hospital Physicians in Four European Cities (the HOUPE‐study): Lise Tevik Løvseth, et al. Department of Research and Development, Division of Psychiatry (AFFU), St Olavs University Hospital, NorwayObjectiveTo investigate how the subjective burden of confidentiality can act as a stressor that affects physicians' psychological health and wellbeing.MethodCross‐sectional survey data from a sample of university hospital physicians (N=1,956) in four European countries (Sweden, Norway, Iceland and Italy) who participated in the HOUPE (Health and Organization among University hospital Physicians in Europe) study was analysed.ResultsAbout 25% of the participants reported that confidentiality impedes emotional support to a considerable degree. An index of confidentiality as a barrier to seeking support (ICBS) had a negative effect on physicians' health and wellbeing. The effect of ICBS was confirmed and slightly increased when controlled for variables known to buffer the adverse mental and physical effects of stress. Though the physicians in Iceland and in Norway found confidentiality the most challenging, it was the physicians in Italy and Sweden who showed a significant effect of ICBS on their health and wellbeing.ConclusionsWhether confidentiality is a stressor in its own right or an amplifier of stressful situations in medical practice should be further investigated to gain a better understanding of the effect of confidentiality on physicians' coping, stress and health. In addition, there is a need to investigate how physicians can balance coping with the inevitable emotional demands of medical practice and maintaining the ethics of confidentiality in a way that protects both patients' privacy rights and physicians' health and wellbeing.
Prevalence of Spina Bifida Among Children and Adolescents in 10 Regions in the United States
Authors: Shin Mikyong , Besser Lilah M. , Siffel Csaba , Kucik James E. , Shaw Gary M. , Lu Chengxing , Correa Adolfo ,   Congenital Anomaly Multistate Prevalence and Survival Collaborative
Published: July 2010

OBJECTIVE:The goal was to estimate the number of children and adolescents, 0 to 19 years of age, living with spina bifida (SB) in the United States.METHODS:A retrospective study was conducted by using population-based, birth defect surveillance data from 10 US regions, with vital status ascertainment. Birth defect surveillance data were obtained from Arkansas, Georgia (5 central counties of metropolitan Atlanta), California (11 counties), Colorado, Iowa, New York (New York City excluded), North Carolina, Oklahoma, Texas, and Utah. We estimated the numbers of children 0 to 19 years of age who were living with SB in the 10 US regions in 2002, according to age group, race/ethnicity, and gender, and examined a long-term trend in the prevalence of SB among children 0 to 11 years of age in 1991–2002.RESULTS:The overall prevalence of SB among children and adolescents 0 to 19 years of age in the study regions was 3.1 cases per 10000 in 2002. The prevalence of SB among children was lower among male and non-Hispanic black children.CONCLUSIONS:The prevalence estimates of SB among children and adolescents varied according to region, race/ethnicity, and gender, which suggests possible variations in prevalence at birth and/or inequities in survival rates. Additional studies are warranted to elucidate the reasons for these variations and to derive prevalence estimates of SB among adults.
Quantitative comparisons and models of time-averaging in bivalve and brachiopod shell accumulations
Authors: Krause Richard A. , Barbour Susan L. , Kowalewski Michał , Kaufman Darrell S. , Romanek Christopher S. , Simões Marcello G. , Wehmiller John F. 
Published: July 2010

The variation in time-averaging between different types of marine skeletal accumulations within a depositional system is not well understood. Here we provide quantitative data on the magnitude of time-averaging and the age structure of the sub-fossil record of two species with divergent physical and ecological characteristics, the brachiopodBouchardia roseaand the bivalveSemele casali.Material was collected from two sites on a mixed carbonate-siliciclastic shelf off the coast of Brazil where both species are dominant components of the local fauna.Individual shells (n= 178) were dated using amino acid racemization (aspartic acid) calibrated with 24 AMS radiocarbon dates. Shell ages range from modern to 8118 yearsb.p.for brachiopods, and modern to 4437 years for bivalves. Significant differences in the shape and central tendency of age-frequency distributions are apparent between each sample. Such differences in time-averaging magnitude confirm the assumption that taphonomic processes are subject to stochastic variation at all spatial and temporal scales. Despite these differences, each sample is temporally incomplete at centennial resolution and three of the four samples have similar right-skewed age-frequency distributions. Simulations of temporal completeness indicate that samples of both species from the shallow site are consistent with a more strongly right-skewed and less-complete age-frequency distribution than those from the deep site.We conclude that intrinsic characteristics of each species exert less control on the time-averaging signature of these samples than do extrinsic factors such as variation in rates of sedimentation and taphonomic destruction. This suggests that brachiopod-dominated and bivalve-dominated shell accumulations may be more similar in temporal resolution than previously thought, and that the temporal resolution of multi-taxic shell accumulations may depend more on site-to-site differences than on the intrinsic properties of the constituent organisms.
Field Study of Ricinus Viking Formation
Authors: Bu F. , Stemler P. , Cheng A. 
Published: July 2010

Abstract
This field study was based on 50 fracturing jobs at 42 wells that Halliburton pumped from 1977 to 2006 for Petro-Canada Oil and Gas Ltd., producing from the Viking formation in the Ricinus area. Four different fluid systems (Guar-borate, CO2, gelled oil and gelled CO2/oil) were investigated to compare their effects on the skin factor, effective fracture half-length, percentage of screenout jobs and production rate. All available fracturing and buildup data were collected and analyzed. Gelled CO2/oil fracture treatment showed the best results on the effective fracture half-length and production rate, and proved to be the best option among these four systems.
This study was also focused on investigating the reasons for a high percentage of fracture jobs being screened out; 85% of the fractures investigated exhibited pressure-dependent leakoff (PDL) behaviour believed to be the primary characteristic of the unsuccessful jobs. Treating the formation at a pressure lower than the fissure opening pressure was considered to be a possible way to avoid screening out. A field case was used to investigate this possibility with the application of a fracture-simulation model, but it was not possible to pump at a rate low enough to prevent opening the natural fractures. Since July 17, 2002, the service company fractured all wells with gelled CO2/oil at high pumping rates and achieved a 100% success rate. This proved that pumping at a high rate is the only option so far to combat PDL and place the proppant successfully. Economic value to the customer (EVC) analysis showed $460,000 in savings on ten gelled CO2/oil high rate fracture jobs for Petro-Canada Oil and Gas Ltd.

Fluid Systems
Four fluid systems have been used to pump 50 fracture stimulation jobs in 42 Ricinus area wells producing from the Viking Formation. Figure 1 shows the area of these 42 wells. Among these 50 fracturing jobs, six used Guar-borate, 12 used gelled oil, 15 used CO2 and 17 used gelled CO2/oil. These fracture stimulation jobs were pumped since 1977. Figure 2 shows the percentage distribution for the four systems involved in this study.
Phase-Behavior Study of Hydrocarbon/Water/Methanol Mixtures at Reservoir Conditions
Authors: Bang Vishal , Pope Gary A. , Sharma Mukul M. 
Published: July 2010

Summary
This paper presents a study of gas/condensate hydrocarbon mixtures and the effect of water, methanol, and isopropanol on their phase behavior. Only sparse data are available on the phase behavior of hydrocarbon/water/methanol mixtures at the high temperatures typical of these reservoirs. Such data are needed for compositional reservoir simulations of well treatments to optimize the performance of solvent treatments of blocked wells. Constant-composition expansion (CCE) experiments were performed to measure the phase behavior of hydrocarbon/water/methanol mixtures up to 300°F. The effects of temperature, pressure, and water and methanol concentration on the phase behavior were measured. The Peng-Robinson equation of state (EOS) was used to model hydrocarbon/water/methanol mixtures. The binary interaction parameters were tuned to fit the data and were found to show a linear variation with temperature. The binary interaction parameters and temperature-dependent volume-shift parameters are the key parameters to model these complex polar mixtures. Both the classical van der Waals and the Huron-Vidal (Huron and Vidal 1979) mixing rules were used and were found to give good agreement with the data. Phase-behavior experiments performed on hydrocarbon/water/isopropanol mixtures showed that isopropanol decreases the aqueous-phase volume fraction and increases the liquid-hydrocarbon-phase volume fraction compared with the analogous hydrocarbon/water/methanol mixtures. These data are needed to predict the conditions under which methanol/isopropanol treatments can be applied successfully in gas wells to remove water and condensate blockage.
Analysis of Production Data From Hydraulically Fractured Horizontal Wells in Shale Reservoirs
Authors: Medeiros F.. , Kurtoglu B.. , Ozkan E.. , Kazemi H.. 
Published: July 2010

Summary
This paper discusses the analysis of production data from hydraulically fractured horizontal wells in shale reservoirs. The stimulated volume around the well is simulated by a naturally fractured region. A semianalytical model incorporating the key features of reservoir heterogeneity and the details of hydraulic fracture and wellbore flow is used to present production-decline characteristics in terms of transient-productivity index. Production-decline analysis of fractured horizontal wells in shale-oil and shale-gas formations by transient-productivity index is explained and demonstrated by field applications.
Validation of Blowout-Rate Calculations for Subsea Wells
Authors: Oudeman P.. 
Published: July 2010

Summary
Calculating the blowout rate of oil and gas wells is commonly one of the first steps in environmental-impact assessment, contingency planning, and emergency response. The blowout rate is a direct measure for the economic and environmental damage caused by a blowout and an indicator for the effort required to regain control over the well. Hence, a simulator was developed to estimate blowout rates.
This simulator was validated for field cases by comparing calculated blowout rates with estimates based on observable phenomena such as flame length and heat release rates. This limited validation to onshore- and platform-well blowouts, which are usually governed by critical outflow conditions at surface, because ambient pressure is usually considerably less than the wellbore pressure just upstream of the outflow. For subsea wells, blowing out against the substantially higher pressures at seabed, this does not apply. The blowout rate is determined by the total system performance from inflow at sandface to outflow at seabed.
To validate the blowout-rate calculations under these conditions, data were collected on high-rate well flow through an annulus against elevated surface pressures, resembling subsea blowout conditions. A comparison of the measured rates with the calculated rates demonstrated that the rates could be predicted with a high accuracy, provided that the mechanical condition of the tubulars is taken into account properly. Default assumptions for the hydraulic roughness of the tubulars lead to overestimates of the blowout rates and consequently to worst-case estimates for the environmental and economic damage caused by a blowout.
Why We Don't Learn What We Should From HAZOPs
Authors: Duhon Howard J , Sutton Ian 
Published: July 2010

Summary
During the last 15 years, the process industries have made dramatic improvements in occupational safety. Recordable injury rates have dropped by close to an order of magnitude (Pitlblado 2008). Accurate information pertaining to progress in process safety in the same time period is not available. However, it is likely that improvements in process safety are not nearly so great (Sutton 2009).
From its beginnings in the late 1980s and early 1990s, hazards analysis has been a key item in all process safety programs. After all, if hazards are not identified, they cannot be remediated. Of the various hazards-analysis techniques, the Hazard and Operability Method (HAZOP) has probably gained the greatest acceptance. Therefore, if the process industries are to achieve the same levels of success in process safety as they have in occupational-safety improvements, the effective use of HAZOPs is probably going to be of central importance.
This paper discusses some of the cognitive, social, organizational, and procedural factors that limit the effectiveness of projects in general and of HAZOPs in particular. From this discussion, insights can be developed that can provide ideas for improving the HAZOP process and process-safety-management systems in general.
Faster Convergence in Seismic History Matching by Dividing and Conquering the Unknowns
Authors: Sedighi F.. , Stephen K.D.. D. 
Published: July 2010

Summary
Seismic history matching is the process of modifying a reservoir simulation model to reproduce the observed production data in addition to information gained through time-lapse (4D) seismic data. The search for good predictions requires that many models be generated, particularly if there is an interaction between the properties that we change and their effect on the misfit to observed data. In this paper, we introduce a method of improving search efficiency by estimating such interactions and partitioning the set of unknowns into noninteracting subspaces. We use regression analysis to identify the subspaces, which are then searched separately but simultaneously with an adapted version of the quasiglobal stochastic neighborhood algorithm. We have applied this approach to the Schiehallion field, located on the UK continental shelf. The field model, supplied by the operator, contains a large number of barriers that affect flow at different times during production, and their transmissibilities are highly uncertain. We find that we can successfully represent the misfit function as a second-order polynomial dependent on changes in barrier transmissibility. First, this enables us to identify the most important barriers, and, second, we can modify their transmissibilities efficiently by searching subgroups of the parameter space. Once the regression analysis has been performed, we reduce the number of models required to find a good match by an order of magnitude. By using 4D seismic data to condition saturation and pressure changes in history matching effectively, we have gained a greater insight into reservoir behavior and have been able to predict flow more accurately with an efficient inversion tool. We can now determine unswept areas and make better business decisions.
An Alternative Method of Dealing With Pressure: Friction Reducer for Water Packing of Long Horizontal Open Holes in Low-Fracturing-Gradient Environments
Authors: Baser B.. , Shenoy S.. , Gadiyar B.. , Jain S.. , Parlar M.. 
Published: July 2010

Summary
Water packing is the most commonly used gravel-packing technique for openhole horizontal completions. With this technique, the packing of a horizontal well occurs through two sequential events, called the α wave and the β wave. Because the carrier fluid is diverted into and must travel through the narrow annulus between the screen base pipe and the wash pipe all the way to the toe, pressure builds up steadily during the β wave as the packing proceeds from toe to heel because of high friction pressures in that annulus. This rise in pressure may result in exceeding the fracturing pressure of the reservoir, which in turn causes a premature screenout and an incomplete gravel pack.
This is a well-known problem, which in the past, often limited the horizontal well length that can be gravel packed in many deep-water developments because of a narrow operating window. Today, various methods are available to solve this problem, including mechanical solutions that create a short cut for fluid returns and the use of lightweight gravel that allows pumping at lower rates without having to worry about gravel settling in the work string but still having an α-wave height that will cover the screens.
In this paper, we present an alternative method of dealing with the pressure rise during the β wave, reducing the friction pressures through addition of a friction reducer to brine carrier fluid. We first detail the laboratory-scale experiments used for screening of many additives considered, including laboratory-scale friction pressure measurements, compatibility with high-density brines, gravel settling, formation, and gravel-pack damage. We then discuss the results from full-scale friction tests conducted in pipe and annular geometries, using the best-candidate friction reducer selected on the basis of laboratory tests. The results indicate that a drag reduction of 20 to 70% is attained with an environmentally friendly friction reducer, with gravel-pack retained permeability in the range of 75 to 90%, depending on test conditions, and with minimal to no impact on gravel settling and, thus, on α-wave height.
Simulation of Two-Phase Flow in Reservoir Rocks Using a Lattice Boltzmann Method
Authors: Ramstad Thomas , Øren Pål-Eric , Bakke Stig 
Published: July 2010

SummaryWe present results from simulations of two-phase flow directly on digitized rock-microstructure images of porous media using a lattice Boltzmann (LB) method. The implemented method is performed on a D3Q19 lattice with fluid/fluid and fluid/solid interaction rules to handle interfacial tension and wetting properties. We demonstrate that the model accurately reproduces capillary and wetting effects in pores with a noncircular shape. The model is applied to study viscous coupling effects for two-phase concurrent annular flow in circular tubes. Simulated relative permeabilities for this case agree with analytical predictions and show that the nonwetting-phase relative permeability might greatly exceed unity when the wetting phase is less viscous than the nonwetting phase.Two-phase LB simulations are performed on microstructure images derived from X-ray microtomography and process-based reconstructions of Bentheimer sandstone. By imposing a flow regulator to control the capillary number of the flow, the LB model can closely mimic typical experimental setups, such as centrifuge capillary pressure and unsteady- and steady-state relative permeability measurements. Computed drainage capillary pressure curves are found to be in excellent agreement with experimental data. Simulated steady-state relative permeabilities at typical capillary numbers in the vicinity of 10−5 are in fair agreement with measured data. The simulations accurately reproduce the wetting-phase relative permeability but tend to underpredict the nonwetting-phase relative permeability at high wetting-phase saturations. We explain this by pointing to percolation threshold effects of the samples. For higher capillary numbers, we correctly observe increased relative permeability for the nonwetting phase caused by mobilization and flow of trapped fluid. It is concluded that the LB model is a powerful and promising tool for deriving physically meaningful constitutive relations directly from rock-microstructure images.
Support-Vector Regression for Permeability Prediction in a Heterogeneous Reservoir: A Comparative Study
Authors: Al-Anazi A.. , Gates I.D.. D. 
Published: July 2010

Summary
Permeability is a key parameter in reservoir-engineering computation, and the relationship between rock petrophysical properties and permeability is often complex and difficult to understand by using conventional statistical methods. Neural-network-based methods can be employed to develop more-accurate permeability correlations, but the correlations from these methods have limited generalizability and the global correlations are usually less accurate compared to local correlations. In this research, the objective is to build a permeability model with promising generalization performance. Recently, support-vector machines (SVMs) based on statistical-learning theory have been proposed as a new intelligence technique for both prediction and classification tasks. The formulation of SVMs embodies the structural-risk-minimization (SRM) principle, which has been shown to be superior to the traditional empirical-risk-minimization (ERM) principle employed by conventional neural networks. This new formulation deals with kernel functions, allows projection to higher planes, and solves more-complex nonlinear problems. SRM minimizes an upper bound on the expected risk, as opposed to ERM, which minimizes the error on the training data. It is this difference that equips SVMs with a greater ability to generalize, which is the goal in reservoir-characterization statistical learning. This novel support-vector-regression (SVR) algorithm was first introduced in well-logs intelligent analysis. Here, a permeability-prediction model using SVR from well logs in a heterogeneous sandstone reservoir is developed. Also, an attempt has been made to review the basic ideas underlying support-vector machines for function estimation. To demonstrate the potential of the proposed SVM's regression technique in prediction permeability, a study was performed to compare its performance with multilayer perceptron neural network, generalized neural network, and radial-basis-function neural networks. Accuracy and robustness were investigated, and statistical-error analysis reveals that the SVM approach is superior to the other methods for generalizing previously unseen permeability data.