bluuebunny/crossref_metadata_2025 huggingface dataset:
Tablas de referencia de condición física en niñas de 10 a 14 años de Chillan, Chile
Authors: Hernández Mosqueira Claudio Marcelo , Fernandes Da Silva Sandro , Fernandes Filho José
Published: April 2016

Elaborar Tablas de Referencia de la condición física orientada a la salud en estudiantes Damas de 10 a 14 años de la ciudad de Chillan.

Método El presente estudio es de tipo descriptivo de corte transversal. La muestra se compone de 250 damas con edades desde  los 10 a 14 años. Para la evaluación de las capacidades físicas orientadas a la salud se utilizaron  los test de Antropometría (IMC), la Formula de Deurengerg (% Tejido Adiposo), Wells y Dillons (flexibilidad), Sargent Test (fuerza miembros inferiores), Test de 1 Milla (resistencia cardiorrespiratoria) y abdominales en 30 segundos (resistencia muscular localizada). Para la confección de las tablas de referencia se utilizó estadística descriptiva y a partir de los resultados se confeccionaron las tablas de referencia; fueron divididas en cinco clasificaciones desde muy malo, malo, regular, bueno y muy bueno, teniendo como parámetro la edad.

Resultados El nivel de condición física en comparación con valores de referencia nacional e internacional, presenta bajos niveles de resistencia cardiorrespiratoria, fuerza de miembros inferiores, flexibilidad, resistencia muscular localizada. Además, que el sobrepeso está asociado a una baja capacidad cardiorrespiratoria y que la cifra  está por encima de la prevalencia a nivel nacional de sobrepeso y obesidad en niñas de 10 a 14 años.

Conclusiones Las pruebas aplicadas en la presente investigación brindan una herramienta fiable y sencilla para conocer el nivel de condición  física orientada a la salud, las cuales pueden ser utilizadas en cualquier institución educativa, ya que no se requiere de gran infraestructura para su aplicación.
Estado nutricional y consumo de alimentos de estudiantes universitarios admitidos a nutrición y dietética en la Universidad Nacional De Colombia
Authors: Vargas Melier E. , Becerra Fabiola
Published: April 2016

Determinar el estado nutricional y algunas características del consumo de alimentos de los estudiantes de pregrado admitidos a primer semestre de la Carrera de Nutrición y Dietética, en la Universidad Nacional de Colombia, Facultad de Medicina, durante el segundo semestre de 2010 y el primer semestre de 2011.

Materiales y Métodos Estudio observacional, descriptivo y transversal.  La muestra fue de 70 estudiantes. Se aplicó una encuesta para determinar características del consumo de alimentos y se tomaron medidas antropométricas. Se utilizó Excel, Access 2010 y Epi-info 2002. Se determinaron medidas de tendencia central estratificadas por género y edad.

Resultados Según el IMC, aproximadamente tres de cada cuatro estudiantes fueron clasificados como normales. La prevalencia de malnutrición fue mayor en hombres que en mujeres.

Aproximadamente 70 % de los estudiantes consumía leche y derivados lácteos y 61 % consumía carnes diariamente. Cerca de la mitad de los estudiantes consumía huevo 2 a 3 veces por semana y sólo un 27 % lo hacía a diario. La mitad de los estudiantes manifestó consumir diariamente fruta en jugo, y sólo un 37 % las consumía enteras con la misma frecuencia. Las verduras fueron las de menor frecuencia de consumo. Cerca del 10 % de los estudiantes consumía diariamente alimentos de baja densidad nutricional (productos de paquete, gaseosa y adición de grasa a los alimentos), y 5 % consumía comidas rápidas. 

Conclusión Los estudiantes presentaron inadecuados hábitos alimentarios que posiblemente se relacionan con la prevalencia de malnutrición hallada.
Comparación de barnices y dentífrico fluorado en la prevención de caries en escolares
Authors: Irigoyen-Camacho Maria Esther , Luengas-Aguirre María I. , Amador-Pedraza Yazmine , Zepeda-Zepeda Marco A. , Villanueva-Gutiérrez Teresa , Sánchez-Pérez Leonor
Published: April 2016

Comparar el efecto preventivo de caries dental de dos frecuencias de aplicación de  barniz fluorado (BF) con un grupo que utilizó instrucciones de cepillado con dentífrico fluorado.

Materiales y Método Se siguieron durante 22 meses a 203 niños de una escuela primaria en la delegación Tláhuac, Ciudad de México, quienes fueron asignados aleatoriamente a uno de los siguientes grupos: 1) instrucciones de cepillado con dentífrico fluorado 3 veces al año, 2) BF semestral, 3) BF tres aplicaciones semanales al año. El BF contenía fluorosilano (1000 ppm F), el dentífrico NaF (1450 ppm F). Se registró el índice de caries CPOD y la presencia de manchas blancas usando los criterios del ICDAS (International Caries Detection and Assessment System).

Resultados Al inicio del estudio, el promedio de edad fue 9,3 (DE 0,76) años, el promedio de lesiones blancas 0,63 (DE 1,48) y del CPOD 0,70 (DE 1,11). CPOD inicial y final en los tres grupos fueron: instrucciones de cepillado usando dentífrico fluorado 0,67 y  1.17, BF semestral 0,77 y  1,46  y grupo BF 3 aplicaciones 0,67 y 1,03, respectivamente.. De acuerdo a los resultados del modelo GEE (Generalized Estimating Equations), no se detectaron diferencias significativas en el incremento de lesiones blancas o en el CPOD para el índice de caries (CPOD) entre los tres grupo; para el CPOD las aplicaciones semestrales mostraron RR=1,24 (p=0,178) y para 3 aplicaciones RR=0,83, (p=0,298), comparando con el grupo de instrucciones de cepillado con dentífrico fluorado, controlando por edad, sexo, cpod  inicial y frecuencia de cepillado.

Conclusiones Los escolares mostraron una baja incidencia de caries utilizando cualquiera de los tres regímenes preventivos aplicados.
Los cuartos oscuros y los hombres que tienen sexo con hombres: haciendo visible lo invisible
Authors: Cardozo Cruz Milton , Ramírez Pereira Mirliana
Published: April 2016

Diseñar un modelo explicativo de las representaciones sociales en los Hombres que tienen sexo con hombres sobre los cuartos oscuros de la ciudad de Santiago de Chile durante el segundo semestre del año 2012.

Método Investigación de tipo cualitativa, exploratoria y explicativa. El enfoque teórico-metodológico escogido fue la teoría fundada. La recolección de información se realizó mediante entrevistas en profundidad.

Resultados En la primera fase de la investigación se realizó la codificación abierta,  se identificaron los códigos y categorías asociados de: concepción del cuarto oscuro, bioseguridad, justificaciones para ingresar a un cuarto oscuro, valoración del cuarto oscuro, prácticas sexuales, orientación sexual y roles y modos de relacionarse.

Conclusiones Es imperioso el desarrollo de políticas públicas en salud que permita afectar los determinantes sociales de la misma. Se identifica tres puntos clave a intervenir para incidir positivamente en la salud de los hombres que tienen sexo con hombres: La discriminación y rechazo social, la ausencia o la disminución de la percepción del riesgo frente a los cuartos oscuros y los sitios de encuentro sexual y la necesidad de realizar inspección, vigilancia y control sobre dichos lugares.
Numerical estimation and HVSR measurements of characteristic site period of sloping terrains
Authors: Diaz-Segura E. G.
Published: April 2016

The characteristic site period, T0, is an essential parameter to estimate the impact of local site effects on ground motion as it is a very useful tool for defining the period of vibration at which greater signal amplification can be expected. For a sloping terrain, unlike what is seen with horizontal terrains or low gradients, the response to a seismic event requires at least a two-dimensional (2D) analysis to determine T0. This study evaluated T0 in sloping terrains with an angle of inclination > 15°. The dynamic response of the terrain was evaluated using 2D and three-dimensional (3D) finite-element modelling. Following the recommendations for recording vibrations in a sloping terrain, different measurements were taken using the horizontal-to-vertical spectral ratio method. From the results obtained with the 2D and 3D models for terrains with different geometrical configurations along with field measurements, it was observed that any point on a sloping terrain experiences two amplification peaks, the maximum values of which are related to the same periods as any other point along the gradient of the terrain. Therefore, on a sloping terrain, it is more appropriate to associate two characteristic periods that depend on the characteristics of the surrounding soil.
The influence of categorization level on inductive reasoning in two and three-year children
Authors: Kotov A.A. , Kotova T.N.
Published: April 2016

Previous studies using the method of successive touches show that children under fifteen years tend to take up the objects from the same category in a row, if they represent categories differing on a superordinate level, but do it at random if the difference between the categories is on base level. These results are considered to be the evidence of an earlier development of superordinate categories, compared to the basic ones. In our experiment, we asked the two and three year old children to fulfill an inductive reasoning task after using the method of successive touches. We found that the two-year children after the categorization of objects with the superordinate contrast performed more successfully on inductive inference task than with contrast at a basic level. The three-year children were successful in the implementation of the inductive inference task after any categorization experience. The results prove that the superordinate category in two year old children appear before the categories of the basic level and facilitate learning a new categorical information.
Precisión diagnóstica de indicadores antropométricos: perímetro de cintura, índice cintura-talla e índice cintura-cadera para la identificación de sobrepeso y obesidad infantil
Authors: Saldívar-Cerón HI , Vázquez-Martínez AL , Barrón-Torres MT
Published: April 2016

INTRODUCCIÓN: la identificación de obesidad durante la infancia es complicada debido a que la talla sigue incrementándose y la composición corporal está cambiando constantemente; actualmente su diagnóstico se realiza por medio de los patrones de crecimiento propuestos por la Organización Mundial de la Salud (OMS); sin embargo, se han propuesto diversos indicadores antropométricos para una detección equivalente. OBJETIVO: determinar la precisión diagnóstica del perímetro de cintura, el índice cintura-talla y el índice cintura-cadera para la identificación de sobrepeso y obesidad infantil. MATERIAL Y MÉTODOS: estudio transversal y analítico con una muestra de 1,001 escolares (9-11 años) de ambos géneros. Se hicieron las mediciones antropométricas (peso, talla, perímetro de cintura y perímetro de cadera) y se calculó el índice de masa corporal, índice cintura-talla e índice cintura-cadera. Se evaluó la correlación de los índices antropométricos vs. el índice de masa corporal y se efectuó un análisis de curvas ROC tomando como variable de estudio el perímetro de cintura, índice cintura talla e índice cintura-cadera y como parámetro de referencia los percentiles de índice de masa corporal (OMS, 2007). Se obtuvieron la sensibilidad, especificidad, las áreas bajo la curva, el valor predictivo positivo y negativo de los indicadores antropométricos y los puntos de corte que identifican sobrepeso y obesidad. RESULTADOS: el perímetro de cintura y el índice cintura talla tienen una alta correlación positiva (r = 0.75, 0.69, respectivamente; p < 0.001), pero la correlación fue débil para el índice cintura-cadera (r = 0.23; p < 0.001). El perímetro de cintura e índice cintura-talla mostraron grandes áreas bajo la curva, sensibilidad, especificidad, valor predictivo positivo y valor predictivo negativo para la identificación de obesidad infantil.CONCLUSIÓN: el perímetro de cintura y el índice cintura talla tienen un alto poder predictivo para identificar obesidad infantil, no así para sobrepeso. Los puntos de corte sugeridos para el diagnóstico de obesidad infantil entre 9 y 11 años son de 70 cm para perímetro de cintura y 0.5 para índice cintura-talla en ambos géneros.
Odvisnost velikosti prevodnih elementov doba (Quercus robur L.) od temperatur na dveh rastiščih Querco-Carpinetum v Sloveniji
Authors: Jevšenak Jernej , Levanič Tom
Published: April 2016

The aim of our study is to fully investigate the relationship between mean monthly temperatures and vessel features. Two vital and one declining groups of pedunculate oak from two Querco-Carpinetum sites in Slovenia are analyzed. Chronologies of mean vessel area and sum of vessel area were developed after previous high quality surface preparation and image analysis with macro EWVA in the ImageJ program. Declining group from Cigonca had the biggest average vessel and the largest amount of conductive tissue, which was linked to the dieback of this group. The analysis of temporal stability of correlation coefficients for declining group explained negative correlations, which were not stable in time. All groups were most responsive to the April temperatures. For all groups, climate signal was the strongest in the mean vessel area parameter. For vital group from Mlače we can expect, in the event of continuous rising of mean temperatures, bigger mean vessels that are more likely to be affected by cavitation. Lower ground water table in 1982 at Cigonca coincides with the reduced climate signal in the vessels.
The Effect of Hydrogen on Precipitation Hardenable Nickel Alloys for Downhole Applications
Authors: McCoy S. A. , Mannan S. K. , Tassen C. S.
Published: April 2016

High strength Nickel alloys are widely used in subsea and downhole O&G applications for their excellent combination of mechanical properties, toughness and corrosion resistance in sour environments. The trend in the O&G industry is for using higher strength materials for high pressure – high temperature service, however as strength increases materials may also become more susceptible to ambient temperature failure mechanisms associated with hydrogen absorption. In recent years resistance to Hydrogen Stress Cracking and Hydrogen Embrittlement as well as sour corrosion resistance have become of increasing interest to the industry due to a number of reported failures of high strength precipitation hardened Nickel alloy grades used in completion tools. The failures of the materials have been attributed to unfavourable microstructures increasing their susceptibility to HSC. A number of factors are known to influence HSC1,2 and this paper reviews previous work and shows laboratory results using different test techniques to demonstrate the influence of yield strength and microstructure on the resistance to Hydrogen Embrittlement of Nickel alloys 718 and alloy 945X (UNS N09946). Tests have been conducted in Hydrogen charging environments while conducting a slow strain rate test and also by pre-charging tensile samples and assessing the effect of hydrogen absorption on the materials' ductility. The resistance of the Nickel alloys to HSC is correlated with microstructure and mechanical properties.
CFD Erosion Prediction in Gas-Liquid-Sand Flow
Authors: Barton Neil , Lewis Mike , Emmerson Paul
Published: April 2016

Sand particle erosion is a significant issue in oil and gas production. There is reasonable evidence to suggest that most wells now produce sand and that erosion accounts for about 10% to 20% of hydrocarbon release events. This is a widespread problem, affecting production both at the start of life and aging assets.

Accurate erosion predictions can be used to improve pipework design, inspection regimes, sand monitor placement and operating limits. There are various approaches to erosion prediction, ranging from simple equations to highly-sophisticated computational fluid dynamics (CFD) simulations. Each method has its advantages. Simpler calculations are generally quick and easy to use but they may be less accurate. CFD modelling can be more accurate and it can detect issues that other methods cannot, but it is a more time-consuming process.

Very little information is available on the relative merits of different erosion prediction methods. Erosion in multiphase pipe flows is a complex process; it is not fully understood, and there is significant scope to improve calculation methods. High-accuracy prediction is particularly important when a system is operating close to its tolerable erosion limit and over-estimates of erosion can lead to unnecessary design changes or overly-conservative production limits.

This work compares erosion predictions using standard erosion calculation methods (such as SPPS and DNV GL RPO501) and conventional CFD simulations against published erosion test data for bends in single and multiphase flow. Essentially, all of the methods produce similar results, with reasonable predictions for gas-sand flows, but significantly over-estimate erosion in the gas-liquid-sand flow regimes, which are more usually experienced in production systems. This comparison provides a useful measure of the overall accuracy of these methods, and hence how the results of erosion calculations should be used to steer engineering decisions.

An extension of previously published work is also included which shows that CFD simulations that explicitly model gas, liquid and sand as separate phases are as accurate as the best conventional erosion prediction methods. This approach has the advantage of being able to model complex geometries and no prior knowledge of the flow regime is required.
Investigation of Severe Tubing Corrosion in a Shale Gas Observation Well
Authors: Purdy Ivan , Pyecroft James , Thomas Lyndsey
Published: April 2016

The Horn River shale gas play has been estimated at 500 TCF. Multiple large slickwater fracture stimulations are applied to horizontal wells to initiate gas production. A typical Nexen Dilly Creek shale gas well pad has 16 to 20 horizontal wells drilled parallel to the principal insitu stress. The horizontal legs are spaced approximately 300 m apart. A typical well receives 16 to 25 fracture stimulations spaced at 100 m intervals along the horizontal lateral. A slant drilled observation well (Dilly Creek c-F1-J) was drilled and completed and between two stimulated wells. The drilling of the well was concluded in early November, 2013. A string of 2-3/8″ tubing was installed and the well was suspended until July 2014 when wells on the pad were fracture stimulated. During the suspension period a gas head from the formation developed. First indication of a well problem occurred during attempts to land data recorders in the tubing in June 2014, seven months after the well was suspended. Tubing joints were recovered, the deposits were analyzed and a casing inspection log was conducted. Lab tests were then conducted on several recovered tubing joints. Drilling, completions and suspension procedures were reviewed and analyzed. It was concluded that the untreated oxygen in the suspension fluid in combination with the 10% CO2 formation gas caused the severe tubing corrosion.
Development of New Laboratory Test Methods for Measuring Top of the Line Corrosion and Assessing Corrosion Inhibitor Performance
Authors: Thomson Hunter , McCall Matthew , Stephens Amy , Simpson Caroline M. , Ray John , Frigo Dario M. , Graham Gordon M.
Published: April 2016

Top of the line (TOL) corrosion presents a major challenge for many oil and gas operating companies, especially those producing or exporting gas. It is known to occur during multiphase flow, such as transport of wet gas, as a result of water vapour condensing on the upper, internal surfaces of the pipe which may not be protected by conventional corrosion inhibitors. The dissolution of corrosive gases present in the gas stream (mainly CO2 and/or H2S) into the condensed water can result in severe general or localised corrosion. The design and testing of inhibitors to protect against TOL corrosion is a key area of development, and as yet no industry standard test methodology is available for measuring TOL corrosion and assessing inhibitor performance under these conditions.

In order to combat TOL corrosion, effective inhibitors are required to possess two somewhat contradictory properties: namely, to establish stable films on the steel surface while also possessing sufficient volatility to be transported to all locations where protection is required. Recently, we have developed a laboratory test method involving a relatively rapid screening stage followed by testing at more field-representative conditions, to determine TOL corrosion rates as well as to qualify the effectiveness of corrosion inhibitors designed to provide effective control against both TOL and bottom of the line (BOL) corrosion.

The method, which includes techniques for ambient-pressure testing as well as alternative techniques for elevated pressures, has been shown to reliably determine the effectiveness of TOL corrosion inhibitor formulations. Both approaches have been validated by comparison with field cases.

The application of this test methodology is already providing improved inhibitor selection for TOL corrosion, complementary to more standard test methods for inhibitor selection for BOL corrosion.
Optimized Exploration Planning
Authors: Back Michael
Published: April 2016

The process of exploration planning in the oil and gas industry has historically been time-consuming and inefficient with limited information and large uncertainties to contend with. How does an oil and gas company take a set of exploration opportunities stored in disparate systems across the organization and combine them into a single, optimized forward exploration plan? This paper will examine the current industry processes in exploration planning and compare these with the benefits of an integrated solution with direct links from the subsurface to commercial to identify and track key parameters over time for business planning decision making.

This paper will first discuss the industry challenges and current practices in exploration planning. The proposed solution will then be defined as a shared repository of opportunities, consistent capture and quantification of subsurface risk and uncertainty linked with the quantification of potential hydrocarbon recoverable ranges, economic analysis across different fiscal regimes and stochastic portfolio optimization. The paper will then look at optimizing a sample set of exploration opportunities and examine the results and benefits gained after deployment at an integrated national oil company.

The integration of risk and uncertainty from the reservoir properties through to stochastic portfolio optimization based on project timing and working interest is a unique solution compared to the "siloed" and disconnected approach common in the industry. During this project, a shared understanding of risk and uncertainty from the subsurface through to the economic evaluation was observed throughout the asset teams and planners.

The implementation and execution of the proposed solution improved the efficiency of the exploration decision-making process and the management of the company’s exploration portfolio. Integrated exploration planning leads to significant improved overall portfolio revenue at reduced risk and costs. The proposed solution is applicable to any mid- to large-sized oil and gas company with a number of exploration opportunities to choose from for inclusion in their portfolio.

The solution’s value lies in the consistent approach to directly link key risks and uncertainties in the subsurface properties of the reservoir all the way through to the commercial evaluation of a portfolio of exploration opportunities. The result of this approach is optimal decision making and increased efficiencies in exploration business planning due to more thorough understanding and mitigation of key risks and uncertainties affecting the success of exploration opportunities.
Maximising the Value of Unconventional Reservoirs by Choosing the Optimal Appraisal Strategy
Authors: Willigers B. J. , Bratvold R. B , Bickel J. E.
Published: April 2016

The choice of appraisal strategy for the decision whether to develop a reservoir largely determines the amount of uncertainty that is carried forward to the development and execution phase of the project. Hence, the selection of an appraisal strategy can indirectly influence later go/no-go decisions. Reservoirs are appraised by drilling and producing wells. In unconventional reservoirs, these wells represent a small subset of possible wells that could be monetised if the decision were made to develop the reservoir, i.e. the appraisal wells sample an underlying population of possible wells.

This study explores how an optimal appraisal strategy can be designed in terms of the number of appraisal phases, the number of wells to be drilled in each appraisal stage, and how long to produce the appraisal wells before deciding whether to abandon the project or to proceed to the next stage. It is demonstrated how the view on the average expected ultimate recovery of a well in an unconventional reservoir can be continually revised as new information surfaces.

Production data from a large well set from the Montney Formation, which straddles British Columbia and Alberta, Canada, is used to assess how accurately initial production predicts the expected ultimate recovery of a single well.
Simultaneous Solution for Ultimate Recovery, Original Hydrocarbon in Place, and Permeability from Production Data Analysis with Application to the Eagle Ford Shale
Authors: Naeem U l , Hussain Dahraj , Khamees Kareem Al , Callard Jeffrey G. , Devegowda Deepak
Published: April 2016

Two parallel objectives, reservoir characterization and reserves validation are sought with this work. Reservoir characterization for multi-fractured horizontal wells leads to economic optimization of fracture spacing along a horizontal wellbore and the lateral spacing of horizontal wellbores. Accurate reserve determinations are important for forecasting revenue and when buying and selling reserves.

The Eagle Ford shale supplies a rich data set with reservoir fluid phase continuity from oil to condensate to dry gas. Contours of reduced temperature (absolute reservoir temperature divided by critical temperature) are shown in Figure 1. Reservoir temperature was based on recorded temperatures from logs. Determination of critical temperature is discussed later in the paper. Note that the scale in the key, while properly depicting gas with reduced temperatures greater than one, does not intend to portray that gas wells are north of oil wells.

Motivation for this study was based on developing an understanding of recovery factors for producing wells transecting the phase envelope from oil into condensate fluids and for recovery factors, in general, for liquids rich shale reservoirs.

Monthly production, completion reports (G-1 and W-2) and well logs are used to perform production data analysis and to determine perforation cluster and stage spacing for the hydraulic fracture stimulation treatments.
The Market for Privately Owned Mineral Rights in the US Shale Context: A Dynamic Approach
Authors: Agerton Mark J.
Published: April 2016

One of the unique aspects of the US shale boom is that firms have purchased most mineral rights from thousands of small landowners. Though several studies have focused on cross-sectional aspects of these leases, none study their dynamics. Incorporating several aspects of the unique US context, I develop and simulate a model of depletable mineral rights that matches several key aspects of data on leasing and drilling in the US Eagle Ford shale.
Comprehensively Valuing an Asset; How a Holistic Value Approach Aligns With Specific Corporate Goals
Authors: Capps Caitlan , Jones David
Published: April 2016

Valuing an asset is not simply taking total potential revenue and deducting from it the estimated cost to produce that revenue. Likewise, an asset with the highest net present value (NPV) is not necessarily the best investment for a company to make. More important than its potential to generate revenue, defining the value of an asset depends on the context of the company portfolio to which the asset belongs as well as the current and future environment and infrastructure surrounding that asset. Too simple an approach in evaluating an asset can cause a distortion of results; for instance, a simple NPV calculation of one particular asset may not factor in a company's overall cash flow, any present long-term investments or existing rig contracts. Similarly, a company must take into account market risk, current interdependencies of the complex network of getting product to market, and future infrastructural and environmental challenges before moving forward with a decision. By approaching the broad term "asset value" and demarcating it to fit a specific company based on the aforementioned items, the company can holistically value an asset. Valuing an asset requires having the ability to isolate specific variables, run several iterations of calculations, and analyze the results from multiple angles, all while using data that is a true reflection of the current state of the market and asset in question. There are multiple ways of measuring value that can have drastically differing implications, and by utilizing a comprehensive approach, an asset's true value can be measured for the company performing the evaluation. In this way, any one asset's value can differ from company to company. By building a comprehensive model which takes into consideration all present and future constraints and characteristics of an opportunity, a company can evaluate numerous variables and analyze them against strategic goals.
Comparing the Results of an Exploration Portfolio Optimized Using Utility Theory Versus the Kelly Criterion
Authors: MacKay James A. , Citron Gary P. , Carragher Peter
Published: April 2016

Both the Kelly Criterion and risk aversion using utility theory are methods that attempt to mitigate the risk of gambler's ruin through capital management by suggesting working interest levels for each project. Utility theory uses an assigned risk tolerance and a natural log utility function to calculate the optimum working interest for a project. The modified Kelly method does not use a utility function but rather a geometric mean-based valuation derived from the ratio of the expected value to the net present value. This ratio, called the Kelly Criterion, is a guide for capital allocation to a project as the percent of the total capital available.

When the total recommended cost of all the projects exceeds the budget, the combined portfolio is optimized by further adjusting the working interest using a linear programming technique, such as Excel’s ™ Solver. This optimization process was described by MacKay (1995) at a previous HEES Symposium (SPE 30043). The objective of this paper is to compare the procedure described by MacKay (1995) to a similar procedure using the modified Kelly method. The Kelly Criterion is currently used for financial investment decisions (Lee, 2006) and described in the book "Fortune’s Formula" by Poundstone (2005).
Screening, Assessing, and Sorting Chinese Oilfields for CO2-EOR Suitability and Potential Economic and Social Benefits
Authors: Meng X. , Zhou H. B. , Luo D. K.
Published: April 2016

The earth environment that human beings rely on is seriously threatened by air pollution and global climate change caused by massive CO2 emissions into the atmosphere. Several studies show that geological storage is an effective way to dispose of CO2. Most oilfields in China have entered middle and late development stages, and a great proportion of them are suitable for CO2-EOR and carbon storage. Enormous economic and social benefits could be brought about by applying CO2-EOR technologies in these oilfields. Therefore, the objective of this paper is to systematically screen, assess, and sort the oilfields in China for their suitability for CO2-EOR and assess potential economic and social benefits for implementing CO2-EOR.

First, the screening criteria of the reservoirs suitable for CO2-EOR used in previous studies by many experts were summarized. Second, the screening of Chinese oilfields suitable for CO2-EOR was first executed based on these screening criteria. Then, a comprehensive assessment and sorting of reservoirs suitable for CO2-EOR was carried out using the fuzzy analytic hierarchy process (FAHP) method. Finally, potential economic and social benefits due to CO2-EOR in China were assessed.

Based on data from 511 onshore oilfields in China, the screening result indicates that 151 oilfields are suitable for CO2 miscible flooding and 1 oilfield is suitable for CO2 immiscible flooding. Using the fuzzy analytic hierarchy process method, the 152 oilfields were synthetically assessed and sorted and their potential benefits were evaluated. Using enhanced oil recovery from 5% to 20%, the resulting incremental production could be 3.45×108t to 13.81×108t, respectively, and the CO2 storage potential could be 8.55×108t to 34.19×108t. Total potential economic benefits could reach $76.15 billion to $710.75 billion, CO2 emission reduction benefits could be $0.35 billion to $64.27 billion, energy security benefits could be $0.84 billion to $3.35 billion, and the total benefits could reach $77.34 billion to $778.37 billion. The implementation of CO2-EOR in China could greatly contribute to the Chinese economy and carbon reduction commitment.

This study conducted a survey of the suitability of Chinese oilfields for CO2 EOR, evaluated and sorting the suitability of different oilfields comprehensively and finally calculated the potential economic and social benefits. This study will provide a foundation for the implementation of a CO2-EOR program in China.
Analysis of Supply and Demand Dynamics to Predict Oil Market Trends: A Case Study of 2015 Price Data
Authors: Rafieisakhaei Mohammadhussein , Barazandeh Babak , Tarrahi Mohammadali
Published: April 2016

Understanding the oil price changes through the demand and supply dynamics is a challenging problem. Traditional models based on stochastic process and aggregated supply and demand have been successful in explaining the price trends in short periods of time where there is no big changes in either supply or demand sides of oil market. However, these models usually failed to capture the big shocks of oil price in circumstances where there are unexpected influential events, such as reports on the economic growth of the non-OECD members.

In this paper, we propose a revised model of oil price based on the supply and demand dynamics. Particularly, we inspect the effects of unconventional parameters on the oil price, many of which have been ignored in the traditional models. Our model investigates the effects of these expectational parameters on the major factors that shape the supply and demand. Particularly, the oil price is still modeled to follow the supply to demand ratio, however, the supply and demand are replaced with their expected trends in the model. In other words, based on the influential events that can happen in either demand or supply sides, related variables are initiated which subsequently affect the expected trend of supply or demand, and the oil price eventually.

Our model is a system dynamic model that mathematically relates the determinants of the oil price based on the underlying causal relations. The whole model numerically solves differential equations relating the marginal parameters and the main factors including the oil price, demand and supply. We separate the oil supply into US, OPEC and other non-OPEC countries supplies whose parameters differ due to conventional and unconventional resources. Moreover, we separate the oil demand into OECD, Brazil, Russia, India, China (BRIC) and non-OECD countries’ demands due to the difference in the dependence on the economic growth and oil consumption in those group of countries. We build our core model based on regression analysis on the historic data of WTI oil price, OECD and BRIC economic growth and demand, US, OPEC and other countries supply data. Then we train other parameters of the model using the historic reactions of the market to unexpected events that have occurred in the past.

Finally, we simulate the model to analyze a case study of the events occurred in the 2015 including the deceleration of the growth in Chinese economy, speculations on American shale productions, speculations on the OPEC’s decisions, and conflicts in the Middle-East region. Our results show that our model can be used to reproduce the price trends compliant with the past data, and provide predicted trends of supply, demand and their influences on the price.
The Consequences of New Sources of Capital for the Oil and Gas Sector
Authors: Wild Emma , Wansbury Natalie , Crudgington James , Andrews Mark
Published: April 2016

In recent years there has been a dramatic shift in the sources of capital available for the acquisition, development and production of oil and gas assets. New entrants include Private Equity firms, Infrastructure Funds, and other ‘non-traditional buyers’ to the sector. The consequences of new sources of capital are investigated.

A statistical analysis of transactions that have occurred globally in the last 3 years across upstream, midstream and downstream is presented. This paper also considers a case study and discusses key value drivers for both the buyer and seller, as well as their strategic rationale. Finally, observations are provided on the impact that new entrants are having on cost and risk management in the E&P sector.

Traditional capital sources are on the decline as the majors look to rebalance their portfolios and divest of non-core assets. Increased shareholder scrutiny, and the reduction in oil price has also forced the majority of E&P companies to reduce capital budgets. Non-traditional investors, in the form of National Oil Companies "NOCs" (including sovereign wealth funds), and financial investors (such as private equity and infrastructure funds) have emerged the dominant players in the M&A buyer population, due either to their large sovereign cash reserves, or the vast sums raised for investment funds.

Whilst this new capital has been welcomed by the industry, as it helps to support drilling and development activity levels (that otherwise would have been in further decline), it has also brought with it additional considerations for existing operators, joint venture partners, and regulators. These include: reduced technical/project management skills and the ability to adequately assess and manage risk; misaligned corporate strategies; uneducated buyers entering M&A processes; and differing abilities to manage costs.

This paper highlights the challenges faced by the oil and gas sector and the requirements for capability and competency; the impact of the new entrants to the sector and the sector's need to drive a step change in efficiency and performance, not just receive an injection of capital. However the most important consideration is risk appetite, and a company's ability to appropriately assess risk. The investors who develop or acquire the expertise to adequately characterize level of risk exposure, and identify assets commensurate with their internal risk appetite, will be the most successful in the long run.
Evolution of Uncertainty Methods in Decline Curve Analysis
Authors: Purvis D. C. , Kuzma Heidi
Published: April 2016

Decline curve analysis has dominated reserve estimation techniques for decades. Ironically, the introduction and expansion of probabilistic calculation techniques largely by-passed these kind of calculations, but not for lack of effort.

Much thought and writing has been dedicated to the unique issue of defining uncertainty in future production trends. Despite two decades of slow evolution, the resulting methods have been partial and prohibitive. Methods like scenario analysis, Delphi forecasting, bootstrapping and Bayesian networks have been proposed and even sometimes utilized. Though they have demonstrated some success, they all suffer from limitations in difficulty and objectivity and aggregation. They have also all utilized smooth model fits and projections. In tandem, other kinds and ways of uncertainty analysis have been applied in the time-domain or dependent sequences using decision trees, Bayesian networks and, more recently, Markov chains.

Newly developed machine-learning techniques combine these two separate streams of uncertainty analysis into a framework that promises to address both the quantification and aggregation of uncertainty in an objective way. What seems like a black-box method is instead a natural and automated extension of well-accepted techniques, and the few published studies of the technique suggest that it may be robust, particularly over the scale of years.
Understanding Shale Resource Production: What are the Key Variables?
Authors: Ikonnikova Svetlana , Vankov Emilian , Gülen Gürcan , Browning John
Published: April 2016

Gradually increasing production of natural gas from shale formations has surpassed the production from all other sources, including conventional, coal-bed, and tight formations in the U.S. (EIA, Monthly Energy Review, Jan. 2016). In fact, thanks to shale, natural gas production in the U.S. increased much faster than demand growth. Lower gas prices since 2010-11 owing to excess supply, has been encouraging more natural gas utilization in power generation and industrial sector, and exports via pipelines to Mexico and the rest of the world via liquefaction facilities. Many of these facilities are still under construction; and demand growth may not be fully felt until 2018 or later. In the meantime, shale drilling has slowed down considerably owing to low oil (and NGL) prices in addition to low natural gas prices. This situation raises concerns about the shale gas resource potential and future production capabilities.

To address these concerns, the understanding of the two key resource characteristics is essential: (1) the total resource-in-place, and (2) the extractability of the resource under the given technological and economic conditions. The Marcellus play is the largest shale gas play in the U.S.; gas production from the play continued to increase despite declining prices and drilling activity. In this study, we focus on the Marcellus play to study these two characteristics.

The resource base estimate for the Marcellus has been provided by geologic studies (e.g. Smye et al., in review). The recovery remains a subject of discussion in numerous engineering studies (Malpani et al., 2015; Xie and Li, 2014; Arogundade and Sohrabi, 2012). These studies, however, are mostly focused on the best drilling and completion practices, rather than looking at changes in productivity over time or comparison of marginal contribution of different inputs to productivity, which is more relevant for economic studies of the resource extraction. The present paper attempts to fill this gap, preparing the base for further economic viability analyses.
Impacts of Price Differentials, Taxation, and Costs on Shale Gas Drilling: A Marcellus Case Study
Authors: Ikonnikova Svetlana , Gülen Gürcan , Browning John
Published: April 2016

We explore the comparative impacts of capital costs, price differentials, and state fiscal policies on economic decision to drill, paying close attention to the decline of shale well production. We use a standard cash flow model for well economics and perform empirical analysis using actual production and completion data for Marcellus wells, cost and tax payments information from Pennsylvania, West Virginia and New York, and basis differentials in different parts of the play. Wells drilled in similar rock quality areas can have different economic value owing to completion choices and associated costs, state fiscal regimes, and market dynamics as reflected in prices realized by the producers at the wellhead.
The Impact of Changing Operational Activities on Unconventional Resource Extraction
Authors: Cherian Bilu V. , Stacey Edwin S. , Bressler Stephen , Chisler Steve , Rifia Rafif , Kublik Kristina , Narasimhan Santhosh , Gray James K. , Olaoye Olubiyi A. , Atkinson Mariah
Published: April 2016

In mid-2000, the North American energy renaissance began to take shape with a boom in unconventional oil and gas production. Within a decade, the combination of horizontal drilling, completion tools and hydraulic fracturing innovations unlocked a vast resource that was previously considered uneconomic. With a large focus of North American operations been around efficiency, a manufacturing model approach was deployed with significant capital efficiencies that further accelerated the learning curve. As these basins now mature and enter the infill development period, long term production results from these unconventional plays are starting to present valuable information in understanding the late time production performance and in-fill well performance (water cuts, production rates and changes due to interference).

This paper presents results from the analysis of well performance by evaluating infill wells, in-fill lease-line wells and relating these interactions to the completion types and job types deployed. The order of the in-fill operations (East-West, Zipper, etc.) on performance is evaluated together with models to demonstrate the impact of fracturing operations and production operations on fracture asymmetry. Fracture models and production models, together with interference data, are utilized to enhance the understanding of the interactions and support hypothesis that demonstrate the importance of understanding operational timing.
Evolution of Shale Production in a Time of Turbulence
Authors: Cui C. J. , Galvin P. K. , Meyet M. P. , Mozur M. W.
Published: April 2016

North American shale oil producers find themselves in the spotlight. Before 2015, much focus was placed on the miraculous growth of U.S. crude production, which ramped up by 1 million barrels per day (MMBbl/d) every year for five consecutive years, a phenomenon often characterized as the "shale boom". But, heading into 2015, these same producers were hit particularly hard by the sharp and rapid decline in crude oil prices. In an attempt to better understand how North American production has reacted to the fall of oil prices, this paper begins with a high-level overview of the key value drivers behind the shale boom. It aims to explain how past drilling activities, ongoing rig count changes and drilled but uncompleted wells influence current and future shale oil production. Although the dynamics of crude supply and demand are highly unpredictable, this paper identifies underlying themes in the North American oil and gas industry that continue to prevail during a highly volatile market.