bluuebunny/crossref_metadata_2025_split huggingface dataset:
25-Hydroxyvitamin D Status of Healthy, Low-Income, Minority Children in Atlanta, Georgia
Authors: Cole Conrad R. , Grant Frederick K. , Tangpricha Vin , Swaby-Ellis E. Dawn , Smith Joy L. , Jacques Anne , Chen Huiping , Schleicher Rosemary L. , Ziegler Thomas R. 
Published: March 2010

OBJECTIVES:The goals were to determine the prevalence of vitamin D deficiency among minority children in a southern US city, to examine differences in serum 25-hydroxyvitamin D levels between non-Hispanic black and Hispanic children, and to determine dietary sources of vitamin D.METHODS:Low-income, minority children (N = 290; mean age: 2.5 ± 1.2 years) were recruited during well-child clinic visits. Serum 25-hydroxyvitamin D and calcium levels were measured and dietary information was assessed.RESULTS:The mean 25-hydroxyvitamin D3 level was 26.2 ± 7.6 ng/mL, whereas 25-hydroxyvitamin D2 was not detected. Overall, 22.3% of children had deficient serum 25-hydroxyvitamin D3 levels (≤20 ng/mL), 73.6% had less-than-optimal serum 25-hydroxyvitamin D levels (≤30 ng/mL), and 1.4% had low serum calcium levels (≤9 mg/dL). A significantly larger proportion of non-Hispanic black children, compared with Hispanic children, had vitamin D deficiency (26% vs 18%; P &lt; .05). Age and season of recruitment were significantly associated with vitamin D deficiency and low serum calcium levels. Older children (≥3 years) were less likely to have vitamin D deficiency (odds ratio [OR]: 0.89 [95% confidence interval [CI]: 0.81–0.96]; P &lt; .001). Study enrollment during spring and summer reduced the likelihood of vitamin D deficiency by ∼20% (spring, OR: 0.85 [95% CI: 0.73–0.98]; P = .03; summer, OR: 0.82 [95% CI: 0.73–0.92]; P &lt; .01). Fortified milk provided most dietary vitamin D (62%), with Hispanic children reporting greater intake.CONCLUSIONS:Suboptimal vitamin D status was common among apparently healthy, low-income, minority children. Age and season were significant predictors of vitamin D deficiency.
Pediatric Organ Donation and Transplantation
Authors:   Committee on Hospital Care, Section on Surgery, and Section on Critical Care
Published: March 2010

This Policy Statement was revised. See https://doi.org/10.1542/peds.2023-062923.
Pediatric organ donation and organ transplantation can have a significant life-extending benefit to the young recipients of these organs and a high emotional impact on donor and recipient families. Pediatricians, pediatric medical specialists, and pediatric transplant surgeons need to be better acquainted with evolving national strategies that involve organ procurement and organ transplantation to help acquaint families with the benefits and risks of organ donation and transplantation. Efforts of pediatric professionals are needed to shape public policies to provide a system in which procurement, distribution, and cost are fair and equitable to children and adults. Major issues of concern are availability of and access to donor organs; oversight and control of the process; pediatric medical and surgical consultation and continued care throughout the organ-donation and transplantation process; ethical, social, financial, and follow-up issues; insurance-coverage issues; and public awareness of the need for organ donors of all ages.
A New Finite-Volume Approach to Efficient Discretization on Challenging Grids
Authors: Aavatsmark I.. , Eigestad G.T.. T. , Heimsund B.-O.. -O. , Mallison B.T.. T. , Nordbotten J.M.. M. , Øian E.. 
Published: March 2010

Summary
Multipoint-flux-approximation (MPFA) methods were introduced to solve control-volume formulations on general simulation grids for porous-media flow. While these methods are general in the sense that they may be applied to any matching grid, their convergence properties vary.
An important property for multiphase flow is the monotonicity of the numerical elliptic operator. In a recent paper (Nordbotten et al. 2007), conditions for monotonicity on quadrilateral grids have been developed. These conditions indicate that MPFA formulations that lead to smaller flux stencils are desirable for grids with high aspect ratios or severe skewness and for media with strong anisotropy or strong heterogeneity. The ideas were pursued recently in Aavatsmark et al. (2008), where the L-method was introduced for general media in 2D. For homogeneous media and uniform grids, this method has four-point flux stencils and seven-point cell stencils in two dimensions. The reduced stencils appear as a consequence of adapting the method to the closest neighboring cells.
Here, we extend the ideas for discretization on 3D grids, and ideas and results are shown for both conforming and nonconforming grids. The ideas are particularly desirable for simulation grids that contain faults and local grid refinement.
We present numerical results herein that include convergence results for single-phase flow on challenging grids in 2D and 3D and for some simple two-phase results. Also, we compare the L-method with the O-method.
Stress-Corrosion Cracking as an Alternative Time-Dependent Shale-Stability Model
Authors: Park N.. , Olson J.E.. E. , Holder J.. 
Published: March 2010

Summary
Wellbore stability in shale has been a crucial issue for drilling in all kinds of environments. The analysis of time-dependent wellbore stability in shales has largely concentrated on the influence of fluid chemistry and filtrate invasion into the formation to predict compressive failure using poroelasticity and continuum models. This paper presents another possible mechanism for time-dependent behavior—stress-corrosion cracking (subcritical crack growth). Using the discrete-element method (DEM) to simulate grainscale processes, we apply the concept of time-dependent cracking to hole enlargement for vertical wellbores. We use a published example from the North Sea to verify the stress-corrosion model and demonstrate the application to wellbore stability in shale. Laboratory results on rocks indicate a wide range of susceptibility to stress-corrosion cracking related to rock petrology and contact-fluid chemistry. Using laboratory calibrated rock properties, we run 2D, plane-strain simulations of vertical-wellbore stability in shale, where hole enlargement is tracked through time. As a result of stress-corrosion cracking, the numerical models show a time-dependent failure history, with an initial stable period of varying duration (influenced by mud weight, rock properties, and in-situ stress), followed by a brief period of combined shear and tensile failure, and ending with stabilization at an enlarged, elliptically shaped geometry. Time to failure increases with increasing mud weight. Enlarged-hole shape changes from elliptical to roughly circular with decreasing stress anisotropy. These behaviors simulated by the stress-corrosion model coincide with previously reported field experience. This new modeling approach for time-dependent wellbore failure can be readily constrained with straight forward fracture-mechanics tests on rock samples and has the potential to also be applied to time-dependent, intermittent sand or fines generation during production.
Analysis of Control Lines Strapped to Tubing
Authors: Mitchell Robert F. , Ellis S.T.. T. , Siappas G.. , Colyer A.. 
Published: March 2010

Summary
Hydraulic control lines are commonly used to actuate surface- controlled subsurface safety valves (SCSSVs), and new applications include choke operation and the control of more-complex "smart-well" completions. In general, control lines are not subject to routine failures. However, the analysis of worldwide completion failures indicates control lines to be a critical component of failure. In fact, control lines and associated components, such as clamps and fittings, are not engineered with the same rigor as the rest of the well completion.
The first step in understanding control-line failure is predicting the loads and stresses in a control line strapped to the tubing. Tubing movement causes loads in the control line through stretching and bending. To a lesser degree, the tubing is loaded by the control lines. To determine this interaction, a calculation is performed in which the control line and the tubing are treated as a composite, with axial displacement constrained to be the same in both. This analysis provides the average stress state in the control line. Because the control line is fixed at only certain points along the tubing, the variation in stress from the average must be determined between clamps. This paper provides the technical details for both calculations.
Several example cases based on field data are presented that give insight into the potential problems that typical production scenarios create for control lines.
A Mixing Rule of Self Diffusivities in Methane Hydrocarbon Mixtures and the Determination of GOR and Oil Viscosities from NMR Log Data
Authors: Chen Jiansheng , Chen Songhua 
Published: March 2010

Summary
A new mixing rule is described for the prediction of the self diffusivities of gas- and liquid-hydrocarbon molecules in methane/oil mixtures. Unlike macroscopic fluid properties, such as density and viscosity, molecular self diffusivity is a microscopic parameter associated with individual molecular species. Thus, a self diffusivity of a binary mixture of gas and oil is a misnomer. Instead, the self diffusivity of each species in the binary system is affected by the presence of the other species. For that reason, the commonly used log-mean based mixing rule that applies to macroscopic properties of the mixtures is unsuitable for self diffusivity when the reference states are pure Components 1 and 2. We found that it is necessary to introduce two new reference states: One is the infinite dilution of Component 1 in Component 2; the other is the infinite dilution of Component 2 in Component 1. The component can be a single-molecule species or a mixture, as long as its self diffusivity or self diffusivity distribution can be measured. Using this approach, the self diffusivity of each component in the mixture follows the log-mean based mixing rule. This new mixing rule is verified with literature data of methane/hexane, ethane/hexane, methane/octane, ethane/octane, methane/decane, and ethane/decane mixtures over a wide range of temperatures, pressures, and solutiongas concentrations.
The new mixing rule is applied, and a detailed procedure is developed, to determine the gas/oil ratio (GOR) and the live-oil viscosity for in-situ volatile oils from nuclear-magnetic-resonance (NMR) log data. First, the self diffusivities and proton fraction of the methane and oil mixture are determined by fitting the NMR-measured diffusivity distribution with a bimodal distribution. Then, the self diffusivities for the four reference states are calculated using the mixing rule. Finally, the GOR is calculated from the proton ratio, while the live-oil viscosity is calculated from the self diffusivity of pure oil and the GOR. The calculated GOR and oil viscosities are compared to the pressure/volume/temerature (PVT) measurement of the oil sample taken from downhole and show good agreement. GOR and oil viscosities from this new technique can be used for optimizing testing and sampling programs, for reservoir-simulation studies, and for the design of surface production facilities.
A New Look at Wellbore-Collision Probability
Authors: Brooks Andrew G. 
Published: March 2010

Summary
Given the potentially catastrophic human and environmental results of an unplanned well collision, a meaningful estimate of the probability of wellbore intersections provides a valuable risk-management tool. A number of estimation techniques are currently in use in the industry; however, all of these have limitations that may not be clearly understood. For example, many computations currently in use fail when the two wells are parallel; they ignore the fact that the drilled well may have reached its current location without collision, or they return an identical result regardless of whether the drilling well is thought to be approaching or departing from the existing well.
A rational approach to the problem begins by clearly defining the probability to be estimated. This paper presents a method to ascertain the probability that a particular interval of the well being drilled might intersect an existing adjacent wellbore. An overall collision probability can then be obtained by combining the probabilities associated with successive intervals along the reference well. The estimates of probability are based on knowledge of the surveyed well paths and their survey uncertainties, expressed in the form of position covariance matrices.
A body of relevant research exists in the field of astrodynamics concerned with estimating the risk of collision between orbiting satellites. This paper draws on previous work from both the oil field and aerospace in developing a more rigorous assessment of collision probability, overcoming the limitation of previous methods. Examples demonstrate that the new method agrees with analytic results for both parallel and nonparallel well paths in simple cases where both wells are straight in the region of interest.
Probabilistic Aggregation of Oil and Gas Field Resource Estimates and Project Portfolio Analysis
Authors: van Elk Jan F. , Gupta Ritu , Wann David 
Published: March 2010

Summary
Probabilistic aggregation and dependency estimation are essential in portfolio methods, production forecasting, and resource estimation. The use of arithmetic addition understates the true value of the resource estimates within a portfolio of fields. Potentially, this could result in deferral of a project, or loss of lucrative business and commercial opportunities, such as project investment, facilitysizing decisions, or incremental gas-supply commitments.
A statistically robust method for aggregation of resource estimates that appropriately uses expert opinion is presented in this paper. Using two integrated-project examples, this paper introduces new methods for (1) probabilistic aggregation of the resource estimates for multiple fields and (2) estimating a measure of dependency between the resource estimates of individual fields.
The new analytical method for probabilistic aggregation is based on multivariate skew-normal (MSN) distributions, which can model a wide range of skewness through a shape parameter and are used heavily in financial and actuarial applications.
In studies of the fields in which the multiple-realizations approach is used as a basis for the uncertainty framework, tornado diagrams are generated routinely to describe the dependence of the field resources on reservoir parameters. The improved method for evaluating measures of dependency between the resource estimates within a portfolio of fields uses these tornado diagrams as a basis. Incorporating the expertise and knowledge of geologists and petroleum engineers is a critical element of the method.
These methods for probabilistic aggregation and estimating dependencies were developed within the context of the oil industry, but their use is not limited to the oil industry. They are general and can be used in other probabilistic-aggregation problems. Application of these techniques requires limited time and effort, compared to individual-field studies, and can have a profound impact on the uncertainty range of the total resources for the portfolio of fields.
Challenges in Completing Long Horizontal Wells Selectively
Authors: Abbasy Imran , Ritchie Barry , Pitts Michael , White Brendan , Jaafar M. Rushdan 
Published: March 2010

Summary
Although drilling technology is now able to deliver ultra long horizontal wells (LHWs), completion technology has been slower to evolve. Running long liners, effective stimulation, and completions are some of the areas that require more attention. This paper discusses some of the challenges in the development of the Al Shaheen reservoirs offshore Qatar and how they were overcome. Some of these wells have a stepout in excess of 30,000 ft with a total vertical depth of 3,100 to 3,500 ft, and thus, they offer some unique challenges. Running and cementing liners to these depths is difficult, and some of the methods to achieve this effectively are discussed. Perforating guidelines are presented that allow sand control without having to resort to conventional sand-control practices. Stimulation of such long reservoir sections is a particular challenge, and a fine balance must be struck between acid coverage and cost, both for barefoot and perforated intervals. The so-called Q-CAJ technique of acid distribution, which has allowed acceptable stimulation despite these conditions, is presented. The technique also offers opportunities to stimulate long horizontal boreholes more effectively and at lower cost. Some of the wells are completed with multizone selective completions, which push the design limit of equipment. A number of such intelligent wells have been completed successfully, and more aggressive wells are planned. To optimize the development cost, dual-lateral wells have also been drilled with complete control over each lateral. Discussed are some of the underlying completion techniques such as running completion in stages, use of mechanical latches, hydraulic-control-line wet connects, interval control valves, and limitations imposed by control lines. The paper concludes with some of the challenges that have yet to be overcome.
A Guide to Successful Backreaming: Real-Time Case Histories
Authors: Yarim G.. , Ritchie G.M.. M. , May R.B.. B. 
Published: March 2010

Summary
Backreaming is the practice of pumping and rotating the drillstring while simultaneously pulling out of the hole. When reliable topdrive drilling systems (TDSs) on conventional drilling rigs were introduced more than 25 years ago, the practice of backreaming became a popular technique in the driller's toolbox for tripping out of hole initially in deviated wells.
In general, backreaming operations have become a popular solution to poor hole conditions while pulling out of hole, but they are also notorious for causing the very same problems they are supposed to prevent, such as stuck pipe. If backreaming is not performed properly, it may complicate the operations, cause wellbore-stability issues, cause higher equivalent circulating densities (ECDs), and cause stuck-pipe incidents caused by packoffs.
As part of the company's stuck-pipe prevention initiative, it became clear that when backreaming is carried out in a wellbore that has a large amount of cuttings and/or cavings, it can cause problems rather than solve them if it is not done with sufficient care. Also, backreaming and tripping operations were usually occasions when the rig-based team went to a "low-vigilance" level. On the basis of historical cases, it was concluded that in the majority of instances, there were no clear guidelines on when to start, how to do it, when to slow down, and when to stop backreaming operations. A review of industry literature also indicated a lack of procedures generally for backreaming.
As a result of the analysis of the real-time data from several case histories, a plan was put in place to improve backreaming operations, define the situations that require backreaming, and focus on tripping practices to prevent stuck-pipe incidents and tool failures.
This paper focuses on one of the industry's most controversial subjects, reviews the implications of backreaming by using real-time data and case histories, and suggests proven procedures to trouble-free backreaming. It recommends the conditions that require backreaming and also suggests wellbore conditions that are not recommended for backreaming. More importantly, it proposes key drilling parameters that need to be monitored when backreaming. These include pump pressure, torque, hookload, cuttings rate, and downhole measurements (if available) to detect and prevent backreaming-induced operational problems. In addition, this paper provides guidelines for successful backreaming operations and defines conditions that may be resolved without needing to backream. Backreaming guidelines have been developed on the basis of the company's worldwide operations, supported by real-time case histories and an extensive stuck-pipe prevention program.
Miscible Interaction Between Matrix and Fracture: A Visualization and Simulation Study
Authors: Er V.. , Babadagli T.. 
Published: March 2010

Summary
CO2 injection has been applied in naturally fractured reservoirs (NFRs) for the purpose of enhanced oil recovery (i.e., the Wey-burn and Midale fields, Canada; the Wasson and Slaughter fields, USA; and the Bati Raman field, Turkey). The matrix part of these types of reservoirs could potentially be a good storage medium as well. Understanding the matrix/fracture interaction during this process and the dynamics of the flow in this dual-porosity system requires visual analyses. We mimicked fully miscible CO2 injection in NFRs using 2D models with a single fracture and oil (solute)/hydrocarbon solvent pairs. The focus was on the visual pore-scale analysis of miscibility interaction, breakthrough of solvent through fracture, transfer between matrix and fracture, and the dynamics of miscible displacement inside the matrix.
First, matrix/fracture interaction was studied intensively using 2D glass-bead models experimentally. The model was prepared using acrylic sheets and glass beads saturated with oil as a porous medium while a narrow gap of 1-mm size containing filter paper served as a fracture. The first contact miscible solvent (pentane) was injected into the fracture, and the flow distribution was monitored using an image-acquisition and -processing system. The produced solvent and solute were continuously analyzed for compositional study. The effects of several parameters, such as flow rate, viscosity ratio (oil/solvent), and gravity, were studied. Next, the process was modeled numerically using a commercial compositional simulator, and the saturation distribution in the matrix was matched to experimental data. The key parameters in the matching process were the effective diffusion coefficients and the longitudinal and the transverse dispersivities. The diffusion coefficients were specified for each fluid, and dispersivities were assigned into gridblocks separately for the fracture and the matrix.
Gas-Condensate Pseudopressure in Layered Reservoirs
Authors: Singh Kameshwar , Whitson Curtis H. 
Published: March 2010

Summary
This paper presents verification of the Fevang and Whitson (1996) gas-condensate pseudopressure method for layered reservoirs. Layers may be characterized by widely varying permeability and composition, and they may be communicating or noncommunicating. The pseudopressure method is used in well calculations for coarse-grid models with relatively large areal grid dimensions (&gt;50 m), capturing near-well condensate blockage without local grid refinement, thereby reducing run time and model size.
The paper presents examples from several field studies and from two synthetic systems using a commercial reservoir simulator. The field studies include rich- and lean-condensate reservoirs.
The study was conducted using a commercial compositional reservoir simulator. Three-dimensional multilayer, fine-grid (radial and Cartesian) models and equivalent coarse-grid models were used. Both depletion and gas-injection cases were simulated for a wide range of reservoir fluids. Reservoir performance of fine-grid models and coarse-grid models was compared using the gas-condensate pseudopressure method and showed comparable results in all cases studied, including relative permeabilities with capillary-number dependence and high-velocity (β) flow treatment.
The coarse-grid model with pseudopressure is somewhat dependent on coarse-grid size, generally requiring Δx=Δy≈50-100 m for lean gas condensates and Δx=Δy≈100-200 m for rich gas condensates.
The paper verifies for the first time that the gas-condensate pseudopressure method as proposed by Fevang and Whitson (1996) is valid and accurate for layered systems with significant heterogeneity (permeability variation), with and without crossflow, with and without capillary-number modification of relative permeabilities, and for widely ranging fluid compositions in each layer.