bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Method for Partitioning the Attributable Fraction of Multiple Time-Dependent Coexisting Risk Factors for an Adverse Health Outcome
Authors: Lin Haiqun , Allore Heather G. , McAvay Gail , Tinetti Mary E. , Gill Thomas M. , Gross Cary P. , Murphy Terrence E. 
Published: April 2012

Objectives. We decomposed the total effect of coexisting diseases on a timed occurrence of an adverse outcome into additive effects from individual diseases. Methods. In a cohort of older adults enrolled in the Precipitating Events Project in New Haven County, Connecticut, we assessed a longitudinal extension of the average attributable fraction method (LE-AAF) to estimate the additive and order-free contributions of multiple diseases to the timed occurrence of a health outcome, with right censoring, which may be useful when relationships among diseases are complex. We partitioned the contribution to death into additive LE-AAFs for multiple diseases. Results. The onset of heart failure and acute episodes of pneumonia during follow-up contributed the most to death, with the overall LE-AAFs equal to 13.0% and 12.1%, respectively. The contribution of preexisting diseases decreased over the years, with a trend of increasing contribution from new onset of diseases. Conclusions. LE-AAF can be useful for determining the additive and order-free contribution of individual time-varying diseases to a time-to-event outcome.
Payment Source and Emergency Management of Deliberate Self-Harm
Authors: Marcus Steven C. , Bridge Jeffrey A. , Olfson Mark 
Published: April 2012

Objectives. We investigated whether health insurance type (private vs Medicaid) influences the delivery of acute mental health care to patients with deliberate self-harm. Methods. Using National Medicaid Analytic Extract Files (2006) and MarketScan Research Databases (2005–2007), we analyzed claims focusing on emergency episodes of deliberate self-harm of Medicaid- (n = 8228) and privately (n = 2352) insured adults. We analyzed emergency department mental health assessments and outpatient mental health visits in the 30 days following the emergency visit for discharged patients. Results. Medicaid-insured patients were more likely to be discharged (62.7%), and among discharged patients they were less likely to receive a mental health assessment in the emergency department (47.8%) and more likely to receive follow-up outpatient mental health care (52.9%) than were privately insured patients (46.9%, 57.3%, and 41.2%, respectively). Conclusions. Acute emergency management of deliberate self-harm is less intensive for Medicaid- than for privately insured patients, although discharged Medicaid-insured patients are more likely to receive follow-up care. Programmatic reforms are needed to improve access to emergency mental health services, especially in hospitals that serve substantial numbers of Medicaid-insured patients.
Sudden Unexpected Infant Deaths: Sleep Environment and Circumstances
Authors: Schnitzer Patricia G. , Covington Theresa M. , Dykstra Heather K. 
Published: April 2012

Objectives. We sought to describe the characteristics and sleep circumstances of infants who die suddenly and unexpectedly and to examine similarities and differences in risk factors among infants whose deaths are classified as resulting from sudden infant death syndrome (SIDS), suffocation, or undetermined causes. Methods. We used 2005 to 2008 data from 9 US states to assess 3136 sleep-related sudden unexpected infant deaths (SUIDs). Results. Only 25% of infants were sleeping in a crib or on their back when found; 70% were on a surface not intended for infant sleep (e.g., adult bed). Importantly, 64% of infants were sharing a sleep surface, and almost half of these infants were sleeping with an adult. Infants whose deaths were classified as suffocation or undetermined cause were significantly more likely than were infants whose deaths were classified as SIDS to be found on a surface not intended for infant sleep and to be sharing that sleep surface. Conclusions. We identified modifiable sleep environment risk factors in a large proportion of the SUIDs assessed in this study. Our results make an important contribution to the mounting evidence that sleep environment hazards contribute to SUIDs.
Increasing Cell Phone Usage Among Hispanics: Implications for Telephone Surveys
Authors: Lee Sunghee , Elkasabi Mahmoud , Streja Leanne 
Published: April 2012

Objectives. We examined whether the widespread assumption that Hispanics are subject to greater noncoverage bias in landline telephone surveys because they are more likely than other ethnic groups to use cell phones exclusively was supported by data. Methods. Data came from the 2010 National Health Interview Survey and the 2009 California Health Interview Survey. We considered estimates derived from surveys of adults with landline telephones biased and compared them with findings for all adults. Noncoverage bias was the difference between them, examined separately for Hispanics and non-Hispanic Whites. Results. Differences in demographic and health characteristics between cell-only and landline users were larger for non-Hispanic Whites than Hispanics; cell usage was much higher for Hispanics than non-Hispanic Whites. The existence, pattern, and magnitude of noncoverage bias were comparable between the groups. Conclusions. We found no evidence to support a larger noncoverage bias for Hispanics than non-Hispanic Whites in landline telephone surveys. This finding should be considered in the design and interpretation of telephone surveys.
A Reservoir Analyzer Study of the Woodbine Basin
Authors: Rumble R.C. , Spain H.H. , Stamm H.E. 
Published: April 2012

Abstract
This paper presents a reservoir analyzer study of the performance of the Woodbine formation in the East Texas basin. The study was made possible by the compilation of available information on the configuration, thickness and the pressure drawdown of the formation. The investigation was made of the pressure variations in the basin incident to production from the several Woodbine reservoirs. In addition, the apparent compressibility of Woodbine water was evaluated so that the potential water yield of the formation could be determined. The distribution of permeability of the Woodbine sand and the interference between producing areas were also investigated. In conjunction with this basic study of the Woodbine sand, an acceptable match of the production-pressure relationship in the East Texas Field was established on the analyzer.

Introduction
When production is taken from a reservoir contiguous to an aquifer, the resultant pressure gradient causes a water influx into the reservoir. For some years it has been the practice to predict the performance of water drive reservoirs with mathematical equations that relate the water influx into reservoirs to their pressure behavior. A rigorous solution of these equations is quite complex; hence, the conventional method requires the simplifying assumptions that the formation have constant thickness, permeability and porosity, and that it have a known and regular shape. It is necessary to use performance records of the reservoir in question to determine the equation constants that make the results of the mathematical calculations duplicate the reservoir history. The values of the constants determined in this manner sometimes differ so greatly from theoretical or measured values that the constants appear unreasonable. The equation constants comprise such factors as the thickness, porosity and permeability of the formation, and the viscosity and compressibility of water. Usually the thickness, porosity and viscosity are known within a reasonable degree of certainty, whereas the formation permeability and the water compressibility are known with considerably less certainty. Hence, permeability and compressibility values are arbitrarily selected that will make the mathematical equations duplicate the reservoir behavior. In many reservoir studies the value of the compressibility of water thus selected has exceeded the reported value by a factor of from severalfold to manyfold.
Characterization of Sampling-While-Drilling Operations
Authors: Villareal S.. , Pop J.. , Bernard F.. , Harms K.. , Hoefel A.. , Kamiya A.. , Swinburne P.. , Ramshaw S.. 
Published: April 2012

SummaryThe while-drilling environment poses several potential challenges to acquiring representative formation-fluid samples; in particular, sampling times are expected to be restricted (perhaps severely) and dynamic filtration conditions are expected to predominate. With the aim of formulating effective strategies for sampling-while-drilling (SWD) operations, it is natural to seek answers to at least the following questions: When should samples be acquired—immediately after drilling the formation when invasion is shallowest, or after some time when the mudcake is more mature? What is the effect of circulation rate on sample quality? What levels of sample quality are achievable under while-drilling conditions?The first part of the paper describes the SWD tool used to investigate the questions posed. The tool is composed of the following components: a probe module; a pump-out module, which contains within it fluid-property sensors, including a resistivity cell and a 10-channel optical spectrometer; sample-capture modules; and a power-generation module consisting of a dedicated mud turbine and alternator that provide the required pumping power to the sampling tool.The second part of the paper is devoted to the description and analysis of a series of tests performed to characterize SWD operations. In particular, the following aspects were studied for their effect on sampling efficiency and sample contamination: time after drilling, mud-circulation rate, ceasing and resuming pumping operations as a means of mitigating sticking risk during protracted pumping operations, and the integrity of samples captured under drilling conditions. All tests were performed in water-bearing formations drilled with a water-based mud. A wireline sampling (WLS) tool was run after the while-drilling tests were completed in order to compare the performance of the two sampling tools.The principal conclusions derived from the tests conducted are that present-day sampling technology can be made to survive and operate effectively under drilling conditions, and that there appear to be substantial advantages to acquiring samples soon after drilling a formation.
Prediction of Saturation Pressures for Condensate-Gas and Volatile-Oil Mixtures
Authors: Organick E.I. , Golding B.H. 
Published: April 2012

Abstract
A simple correlation is presented for the prediction of saturation pressures in condensate-gas and volatile-oil mixtures. Saturation pressure is related directly to the composition of the mixture with the aid of two generalized composition characteristics, the molal average boiling point, and the modified weight average equivalent molecular weight. The need for hydrocarbon equilibrium constants is entirely eliminated. Only the values of the two composition parameters need be obtained, and these are calculated in a simple and reproducible manner from the stream analysis of the mixture and the ASTM distillation for the heavy ends.
The correlation is given in the form of a set of 14 working charts in which saturation pressures, either retrograde dew points or bubble points, are plotted vs temperature, forming partial phase envelopes for mixtures having discrete values of the composition parameters, the molal average boiling point, and the modified weight average equivalent molecular weight.A locus of critical states on each chart intersects the partial phase envelopes, distinguishing retrograde dew point pressures from bubble pressures.
A comparison between experimental and predicted saturation pressures reveals that: the probable error of the predicted values, when considering the data as a whole (214 experimental points), is five per cent; for high gas/oil ratio condensate fluids (approximately 40,000 or more cu ft/bbl) the probable error is about 8 per cent. In either case, however, the probable error is comparable with the overall uncertainty of the data from which the correlation is derived.

Introduction
There is a present need for a simplified, yet reasonably accurate method for predicting upper phase boundaries of reservoir fluids. In the case of high gas/oil ratio fluids, namely the so-called highly volatile oils and the condensate gases, no simple method, accurate within 5 to 10 per cent, is now available by which bubble point and retrograde dew point pressures may be predicted.
The Role of Diffusion for Nonequilibrium Gas Injection Into a Fractured Reservoir
Authors: Yanze Yannick , Clemens Torsten 
Published: April 2012

Summary
The Schönkirchen Tief oil field is located in the Vienna basin in Austria. It is a pervasively fractured dolomite reservoir that has been produced for more than 50 years. The field is at the tail end of production, the wells are perforated close to the top of the reservoir, and water is injected downdip. Because of the location of the field close to one of the main gas pipelines in Austria, it is planned to convert the field into high-performance underground gas storage (UGS).
The field is characterized by a highly permeable fracture system and a less-permeable matrix system. It is expected that some incremental oil can be recovered because of gas/oil gravity drainage from the matrix.
In addition to gas/oil gravity drainage, diffusion will have an effect on the oil recovery. The injected gas is leaner than the equilibrium gas in the reservoir. Hence, gas components diffuse from the fracture system into the matrix and components of the oil diffuse toward the fracture system. This results in a modification of the properties of the oil affected by diffusion.
This type of gas injection results in a zone of decreased oil viscosity for gases such as CO2 and CH4 at the interface of the gas and the oil in the matrix. This zone of lower oil viscosity increases the gas/oil gravity-drainage rates.
The results show that the effect of diffusion can increase cumulative oil production up to 25% compared with a case neglecting the effect of diffusion. The effect of diffusion could be determined for various parameters such as permeability, porosity, fracture spacing, and matrix-block height. While for some of the parameters the effect of diffusion scales with the square root of time (e.g., permeability), for others an exponential relationship has been determined (fracture spacing).
The results derived for the example reservoir can be used more generally to screen whether the effect of diffusion should be incorporated into reservoir studies concerning nonequilibrium-gas injection and to determine how large the error could be in the case where diffusion is neglected.
Probabilistic Production Forecasting for Unconventional Reservoirs With Stretched Exponential Production Decline Model
Authors: Can B.. , Kabir C.S.. S. 
Published: April 2012

Summary
Reserves estimation in an unconventional-reservoir setting is a daunting task because of geologic uncertainty and complex flow patterns evolving in a long, stimulated horizontal well, among other variables. To tackle this complex problem, we present a reserves-evaluation workflow that couples the traditional decline-curve analysis (DCA) with a probabilistic forecasting frame. The stretched-exponential production-decline (SEPD) model underpins the production behavior. Our recovery appraisal workflow has two different applications: forecasting probabilistic future performance of (1) wells that have production history and of (2) new wells without production data. For the new-field case, numerical-model runs are made in accord with the statistical design of experiments (DOE) for a range of design variables pertinent to the field of interest. In contrast, for the producing wells, the early-time data often need adjustments owing to restimulation, installation of artificial lift, or other factors to focus on the decline trend. Thereafter, production data of either new or existing wells are grouped in accordance with maximum rates to obtain common SEPD model parameters for similar wells. After determining the distribution of model parameters using the well-grouping approach, the method establishes a probabilistic forecast for the individual wells.
This paper presents a probabilistic performance-forecasting method in unconventional reservoirs for wells with and without production history. Unlike other probabilistic forecasting tools, grouping wells with similar production character allows estimation of self-consistent SEPD-model parameters and alleviates the burden of having to define uncertainties associated with reservoir and well-completion parameters.
Protect and Then inject: Optimized Well Fluids Successfully Drill Depleted Reservoirs To Store Gas
Authors: Vickers Stephen , Bruce Stephen , Hutton Alistair , Nunzi Paolo 
Published: April 2012

Summary
A major operator has initiated the data-acquisition campaign in the southern North Sea for a future storage facility capable of holding 5 billion m3 of gas. It is estimated this venture will double the existing gas supplies stored in the UK and represent more than 5% of its annual gas demand. As North Sea gas production decreases and the UK becomes more dependent on imports, the ability to store gas has become an important part of the UK energy policy.
Drilling into depleted reservoirs for gas storage produces several major technical problems and issues that must be addressed. This field is a pressure-depleted reservoir with a differential pressure equivalent to 7.3 lbm/gal between the drilling fluid's hydrostatic pressure and the reservoir pressure. This differential must be controlled to eliminate the risk of differential sticking, downhole losses, and hole collapse.
Because of the reservoir depletion, it would be impossible to backflow and clean up the near-wellbore region without a postdrill-in treatment fluid to remove the fluid filter cake and water-wet all the surfaces for gas injection. To ensure project success and usable fluid designs, reservoir conditions were simulated in the laboratory and fluid parameters were altered to provide the optimum properties to minimize the future risks.
The paper discusses in full the laboratory design process, the verification of the drill-in and treatment fluids as being fit-for-purpose, and their successful application in the field. Initial well testing suggested that the expected injection rates of 500 scf/min at 300 psi were exceeded, with rates of 750 scf/min at 280 psi reported.
Interwell Tracer Tests To Optimize Operating Conditions for a Surfactant Field Trial: Design, Evaluation, and Implications
Authors: Cheng Hao , Shook G. Michael , Taimur Malik , Dwarakanath Varadarajan , Smith Bruce R. 
Published: April 2012

Summary
Enhanced oil recovery (EOR) by surfactant flooding is the key to unlocking the next billion barrels of oil for Minas, one of the world's largest waterflood fields. An interwell tracer test (ITT-1) was performed before a surfactant field trial (SFT) to ensure well injectivity, demonstrate pattern confinement, quantitatively describe interwell connectivity and sweep efficiency, and provide sufficient data for reservoir evaluation. The tracer test was designed by numerical simulation. The test started in November 2009 and was terminated in February 2010.
Analytical interpretation based on moment analysis and numerical reservoir simulations was conducted to evaluate ITT-1 results. Interpretation of the test results indicated various operational and reservoir properties that would have likely led to failure of the surfactant pilot. Hydraulic control of the SFT pattern was not achieved; in fact, less than 20% of one tracer was recovered. Many small-scale heterogeneities were identified that led to a lower-than-expected reservoir volume contacted. Unexpected communication between the target sand and the underlying sands outside the pattern also contributed to low tracer recovery and low swept volume. The tracer test was history matched, and additional features were incorporated in the reservoir model, and a new tracer design (ITT-2) was optimized to correct low sweep efficiency and poor hydraulic control. New information from ITT-2 will be used to further optimize operating conditions for SFTs.
Failure to conduct the tracer tests would have likely revealed these unfavorable reservoir and operational conditions during the SFT. Had oil recovery been poor (because of low swept volume), it would have erroneously been attributed to a poor SFT rather than to the true causes. ITT-1 is considered successful because it allowed us to redesign injection/hydraulic control during the relatively inexpensive tracer test and thus evaluate the surfactant trial without bias.
Lost Circulation Corrective: Time-Setting Clay Cement
Authors: Messenger J.U. , McNiel J.S. 
Published: April 2012

Abstract
In the drilling of oil wells the control and prevention of lost circulation of the drilling fluid is a problem which is frequently encountered; in many cases existing materials and methods for alleviating this condition have not been adequate. For severe cases of lost circulation in which the simpler methods, such as application of various bridging materials to the mud system, have proven unsatisfactory, a new material and method for applying to the loss zones have been developed which appear to be superior to existing techniques in many respects.
The material, called a clay cement, is capable of being handled as a drilling fluid after initial mixing of the solid ingredients with water and may be pumped down the drill pipe and squeezed into loss zones. After a short period, the material develops a very high gel strength which seals off the zone against further losses of the drilling fluid.
In field tests, the process has been demonstrated to be a very effective method for combatting lost circulation.

Introduction
Methods of treating lost circulation in rotary-drilled wells by the addition of special materials to drilling fluids have long been in the process of development and are continuing to improve. However, the annual drilling costs which can be traced directly to lost circulation difficulties still run into the millions of dollars. The loss of mud materials into highly permeable zones may range up to $50,000 per well in some areas. In addition to mud costs, excessive requirements of casing, cement, rig time, and the attendant blowout hazards further emphasize the importance of the need for improved methods of combatting lost circulation. The shortcomings of presently-used materials and methods have led to the development of a new lost returns material in the form of a timesetting clay cement. In field tests this material has proven very successful in plugging off loss zones, which other more conventional materials had failed to do.