bluuebunny/crossref_metadata_2025 huggingface dataset:
O cálculo de alta precisão do período do pêndulo simples
Authors: Claudio G. Carvalhaes , Suppes Patrick
Published: October 2010

Apresentamos o método iterativo da média aritmética-geométrica no cálculo preciso do período temporal do pêndulo simples e o comparamos com o método da série de potências. Aproximações analíticas para o período são obtidas pelos dois métodos e comparadas em termos de suas precisões numéricas. Os resultados são amplamente favoráveis à media aritmética-geométrica em virtude de sua rápida convergência.
A note on nonholonomic systems
Authors: Coutinho F.A.B. , Amaku M.
Published: October 2010

This note describes a question that deals with nonholonomic systems, a subject that has been gradually fading away from textbooks and even treated somewhat incorrectly as holonomic.
Os conteúdos das disciplinas de biofísica e a física
Authors: Corso Gilberto
Published: October 2010

Neste trabalho exploramos os conteúdos ministrados nas disciplinas de biofísica oferecidos na graduação de estudantes da area da saúde e da vida. Na mostra dos conteúdos desta disciplina enfocamos três tópicos: a importância de se ensinar biofísica para se entender fisiologia, a relação entre os conteúdos de biofísica e o maquinário médico hospitalar e os pré-requisitos de física necessários ao estudo da biofísica: em especial aos conteúdos que não estão presentes no segundo grau, como a impedância acústica. Neste contexto estabelecemos as diferenças, às vezes sutis, entre biofísica, física médica e bioengenharia. Por fim escrevemos sobre leis alométricas, biologia molecular e dinâmica de populações que poderiam ser abordados nesta disciplina, mas que por motivos diversos não costumam entrar no conteúdo programático da biofísica na graduação.
A New Look at Induction Chemotherapy in Locally Advanced Head and Neck Cancer
Authors: Vermorken Jan B.
Published: October 2010

This editorial summarizes the current state of knowledge of the treatment of locally advanced head and neck cancer.
TPF Sequential Therapy: When and for Whom?
Authors: Budach Volker
Published: October 2010

Concurrent chemoradiation is a standard approach for the treatment of locally advanced squamous cell carcinoma of the head and neck. However, sequentially administered chemotherapy and radiotherapy/chemoradiation may be an effective alternative for some patients. Although chemoradiation is a highly effective treatment approach, it is associated with high incidences of severe acute toxicities, including mucositis. In addition, late toxicities can cause long-term morbidity in a substantial proportion of patients. In a retrospective analysis of three Radiation Therapy Oncology Group trials, pharyngeal dysfunction was seen in 27% of patients and feeding tube dependence and laryngeal dysfunction were each seen in approximately 12% of patients. Sequential administration of chemotherapy and radiotherapy, with a doublet cisplatin and 5-fluorouracil (PF) induction chemotherapy regimen, is associated with less acute severe mucositis than concomitantly administered cisplatin and radiotherapy. The addition of the taxane docetaxel to PF has resulted in the highly active triplet induction regimen TPF. Data from randomized trials indicate that TPF sequential therapy may be an effective alternative to concurrent chemoradiation for some patients. TPF is well tolerated, although it is associated with a higher incidence of hematologic adverse events than with PF, including neutropenia and neutropenia-related complications. This may be managed by the use of prophylactic G-CSF and/or antibiotics. Patients suitable for treatment with a TPF-based sequential administration approach include those with a good performance status, no contraindication to cisplatin or taxanes, and locally advanced oropharyngeal, hypopharyngeal, or laryngeal cancer with a high tumor load.
Larynx Preservation Clinical Trial Design: Summary of Key Recommendations of a Consensus Panel
Authors: Ang K. Kian
Published: October 2010

An international consensus panel was convened to develop guidelines for the conduct of phase III clinical trials of larynx preservation in patients with locally advanced laryngeal and hypopharyngeal cancer. According to their recommendations, future trial populations should include patients with T2 or T3 laryngeal or hypopharyngeal squamous cell carcinoma not considered for partial laryngectomy and should exclude those with laryngeal dysfunction or aged >70 years. Baseline and post-treatment functional assessments should include speech and swallowing evaluations. Furthermore, voice should be routinely assessed with a simple, validated instrument. Regarding endpoints, the primary endpoint should capture survival and function. As a result, the panel created a new endpoint of laryngoesophageal dysfunction (LED)-free survival, which includes the events of death, local relapse, total or partial laryngectomy, tracheotomy at ≥2 years, or feeding tube at ≥2 years. Recommended secondary endpoints are freedom from LED, overall survival, progression-free survival, locoregional control, time to tracheotomy, time to laryngectomy, time to discontinuation of feeding tube, and quality of life/patient-reported outcomes. Future exploratory correlative biomarker studies should include epidermal growth factor receptor, excision repair cross-complementation group 1 gene, E-cadherin and β-catenin, epiregulin and amphiregulin, and TP53 mutation.

Revised trial designs in several key areas are needed to advance the study of larynx preservation. With consistent methodologies, clinical trials can more effectively evaluate and quantify the therapeutic benefit of novel treatment options for patients with locally advanced laryngeal and hypopharyngeal cancer.
Historic canals of Maryland and Virginia, USA
Authors: Kapsch R. J.
Published: October 2010

This paper describes the canals of Maryland and Virginia as a means of capturing the essence of the American canal experience and the beginning of American civil engineering.
John Monash: promoting early reinforced concrete in Australia
Authors: Holgate A.
Published: October 2010

John Monash (later General Sir John Monash) played an important part in the introduction of reinforced concrete (RC) to Australia, initially in partnership with J. T. N. Anderson. From 1897, under the Monier/Wayss licence, they built arch bridges and ran a precast products factory. From 1903, Monash moved into general RC work alone. His knowledge of German, French and patent law gave him an advantage, but his path was not smooth. He depended heavily on textbooks and journals, and learned much from hard experience. He supervised projects throughout Victoria and eastern South Australia. Staff and labour had to be educated as the enterprise expanded. Much effort went into convincing clients that RC was safe and durable. Opposition came from established industries threatened by the new technology. After initial technical and financial setbacks, Monash began to prosper from 1905 onwards. Many of his structures are still in service. He was not a technical innovator, but made a significant contribution in promoting and defending the new technology. His persistence – and his networking, managerial and diplomatic skills – eased the way for others, who offered competition from 1910 onwards. Monash went on to an illustrious career as commander of Australian forces in the First World War and as founding chairman of the State Electricity Commission of Victoria.
Spatially explicit inference for open populations: estimating demographic parameters from camera‐trap studies
Authors: Gardner Beth , Reppucci Juan , Lucherini Mauro , Royle J. Andrew
Published: October 2010

We develop a hierarchical capture–recapture model for demographically open populations when auxiliary spatial information about location of capture is obtained. Such spatial capture–recapture data arise from studies based on camera trapping, DNA sampling, and other situations in which a spatial array of devices records encounters of unique individuals. We integrate an individual‐based formulation of a Jolly‐Seber type model with recently developed spatially explicit capture–recapture models to estimate density and demographic parameters for survival and recruitment. We adopt a Bayesian framework for inference under this model using the method of data augmentation which is implemented in the software program WinBUGS. The model was motivated by a camera trapping study of Pampas catsLeopardus colocolofrom Argentina, which we present as an illustration of the model in this paper. We provide estimates of density and the first quantitative assessment of vital rates for the Pampas cat in the High Andes. The precision of these estimates is poor due likely to the sparse data set. Unlike conventional inference methods which usually rely on asymptotic arguments, Bayesian inferences are valid in arbitrary sample sizes, and thus the method is ideal for the study of rare or endangered species for which small data sets are typical.
Multiple mechanisms underlie displacement of solitary Hawaiian Hymenoptera by an invasive social wasp
Authors: Wilson E. E. , Holway D. A.
Published: October 2010

Variation in invasion success may result from the divergent evolutionary histories of introduced species compared to those of native taxa. The vulnerability of native biotas to ecological disruption may be especially great on oceanic islands invaded by continental species with unique ecological traits. In part because Hawaii lacks native eusocial insects, social invaders may threaten endemic taxa that are ecologically similar but solitary. Using a combination of field manipulations, molecular analyses, physiological data, and behavioral assays, we identify the mechanisms underlying the displacement of two genera of native solitary Hymenoptera in Hawaii by a social continental invader, the western yellowjacket (Vespula pensylvanica). Experimental removal of V. pensylvanica colonies resulted in increased densities of native Hymenoptera. Endemic Hylaeus bees directly suffer through predation by yellowjackets, and perhaps as a consequence, avoid floral resources occupied by V. pensylvanica. Native Nesodynerus wasps also avoid V. pensylvanica but are negatively affected by yellowjackets not through predation, but through exploitative competition for caterpillar prey. Displacement of native solitary Hymenoptera may be heightened by the ability of V. pensylvanica to prey upon and scavenge honey bees and to rob their honey stores, resources unavailable to endemic bees and wasps because of their specialized niches. Our study provides a unique example of an ecologically generalized social invader that restructures native assemblages of solitary Hymenoptera by interacting with endemic taxa on multiple trophic levels.
Methane flux in non‐wetland soils in response to nitrogen addition: a meta‐analysis
Authors: Aronson E. L. , Helliker B. R.
Published: October 2010

The controls on methane (CH4) flux into and out of soils are not well understood. Environmental variables including temperature, precipitation, and nitrogen (N) status can have strong effects on the magnitude and direction (e.g., uptake vs. release) of CH4 flux. To better understand the interactions between CH4‐cycling microorganisms and N in the non‐wetland soil system, a meta‐analysis was performed on published literature comparing CH4 flux in N amended and matched control plots. An appropriate study index was developed for this purpose. It was found that smaller amounts of N tended to stimulate CH4 uptake while larger amounts tended to inhibit uptake by the soil. When all other variables were accounted for, the switch occurred at 100 kg N·ha−1·yr−1. Managed land and land with a longer duration of fertilization showed greater inhibition of CH4 uptake with added N. These results support the hypotheses that large amounts of available N can inhibit methanotrophy, but also that methanotrophs in upland soils can be N limited in their consumption of CH4 from the atmosphere. There were interactions between other variables and N addition on the CH4 flux response: lower temperature and, to a lesser extent, higher precipitation magnified the inhibition of CH4 uptake due to N addition. Several mechanisms that may cause these trends are discussed, but none could be conclusively supported with this approach. Further controlled and in situ study should be undertaken to isolate the correct mechanism(s) responsible and to model upland CH4 flux.
Food webs are built up with nested subwebs
Authors: Kondoh Michio , Kato Satoshi , Sakato Yoshikuni
Published: October 2010

Nested structure, in which specialists interact with subsets of species with which generalists interact, has been repeatedly found in networks of mutualistic interactions and thus is considered a general feature of mutualistic communities. However, it is uncertain how exclusive nested structure is for mutualistic communities since few studies have evaluated nestedness in other types of networks. Here, we show that 31 published food webs consist of bipartite subwebs that are as highly nested as mutualistic networks, contradicting the hypothesis that antagonistic interactions disfavor nested structure. Our findings suggest that nested networks may be a common pattern of communities that include resource–consumer interactions. In contrast to the hypothesis that nested structure enhances biodiversity in mutualistic communities, we also suggest that nested food webs increase niche overlap among consumers and thus prevent their coexistence. We discuss potential mechanisms for the emergence of nested structure in food webs and other types of ecological networks.
Mapped quadrats in sagebrush steppe: long‐term data for analyzing demographic rates and plant–plant interactions
Authors: Zachmann Luke , Moffet Corey , Adler Peter
Published: October 2010

This historical data set consists of 26 permanent 1‐m2 quadrats located on sagebrush steppe in eastern Idaho, USA. During most growing seasons from 1923 to 1957, and again in 1973, all individual plants in each quadrat were identified and mapped. This combination of a long time‐series with full spatial resolution allows analyses of demographic processes and intra‐ and interspecific interactions among individual plants. The data provide unique opportunities to test theory about the effect of environmental variation on population and community dynamics and to describe empirical relationships between climate variables and demographic rates. We provide the following data and data formats: (1) the digitized maps in shapefile format; (2) a tabular version of the entire data set (a table with no spatial information except an x,y coordinate for each individual plant record); (3) a species list, containing information on plant growth forms and shapefile geometry type; (4) a record of changes to species names; (5) quadrat information; (6) grazing treatment information; (7) an inventory of the years each quadrat was sampled; (8) monthly precipitation, temperature, and snowfall records; and (9) counts of annuals in the quadrats.

The complete data sets corresponding to abstracts published in the Data Papers section of the journal are published electronically in Ecological Archives at 〈http://esapubs.org/archive〉. (The accession number for each Data Paper is given directly beneath the title.)
Drilling Automation: Technologies, Terminology, and Parallels With Other Industries
Authors: Thorogood John , Aldred Walt , Florence Fred , Iversen Fionn
Published: October 2010

Drilling automation is a rapidly developing area of technology that is seeing growing interest within the drilling community. SPE set up a new technical section devoted to the subject as it relates to downhole performance, and the IADC has created a committee with a focus on surface processes.

As with any emerging technology, the associated jargon is evolving rapidly, and different terms are used by different groups to refer to similar concepts with the potential for confusion and misunderstanding. Automation efforts are being undertaken by numerous and diverse organizations, and implementation of such interrelated offerings at the rigsite needs consistent interface criteria at each boundary to ensure efficient and safe operations.

The purpose of the proposed paper is to describe some of the concepts already in operation and under development and to classify them into a number of key categories.

The more significant interface requirements will be identified, and key safety concerns will be highlighted. Parallels will be drawn with other industries to demonstrate analogs and suggest where and how further developments might be expected to lead.
A Study of the Effects of Colloidal Gas Aphron Composition on Pore Blocking
Authors: Bjorndalen N.. , Alvarez J.M.. M. , Jossy W.E.. E. , Kuru E..
Published: October 2010

Drilling fluid containing colloidal gas aphron (CGA) microbubbles can bridge the pores of the reservoir rock in the near-wellbore region and reduce the risks of lost circulation and formation damage. The advantage of using CGA systems is that the CGAs can be removed easily during the initial stages of production, thereby reducing the costs associated with stimulation processes such as acidizing.

Although there has been some work performed on the flow of the microbubbles through porous media, little is known about the optimal conditions for blocking the pores. Specifically, the effect of the interaction between microbubbles and reservoir fluid on the microbubble stability and pore-blocking ability has not been determined.

This study is focused on determining effects of CGA composition on the resistance to the flow of microbubbles through porous media. Increasing resistance to fluid flow was observed as more CGA fluid was injected, indicating that microbubbles could effectively block the pores.

Effects of water, brine, mineral oil, and crude oil, as saturating fluids, on the microbubble stability and pore-blocking ability were also investigated.
Net Pay — What Is It? What Does It Do? How Do We Quantify It? How Do We Use It?
Authors: Worthington Paul F.
Published: October 2010

A knowledge of net pay is important for the volumetric estimation of hydrocarbon resources, a practice that underpins the value of the petroleum industry. Yet, there is no universal definition of net pay, there is no general acceptance of its role in integrated reservoir studies, there is no recognized method for evaluating it, and there are disparate views on how to make use of it. Partly for these reasons, net-to-gross pay constitutes a major source of uncertainty in volumetric reserves estimates, second only to gross rock volume. With the aim of improving this unsatisfactory state of affairs, I chart a critical path of net-pay understanding and application to dispel some of the unhelpful myths that abound within the industry and replace them with a defensible rationale to guide the quantification of net pay (thickness). Central to this process is the identification of net-pay cutoffs, themselves the subject of much controversy over the years. The approach is data-driven, in that it uses what we know, and also fit-for-purpose, in that it takes account of reservoir conditions. The outcome is a sounder basis for incorporating net pay into volumetric estimates of ultimate recovery and thence hydrocarbon resources.
Quantifying Monte Carlo Uncertainty in the Ensemble Kalman Filter
Authors: Thulin Kristian , Nævdal Geir , Skaug Hans Julius , Aanonsen Sigurd Ivar
Published: October 2010

The ensemble Kalman filter (EnKF) is currently considered one of the most promising methods for conditioning reservoir-simulation models to production data. The EnKF is a sequential Monte Carlo method based on a low-rank approximation of the system covariance matrix. The posterior probability distribution of model variables may be estimated from the updated ensemble, but, because of the low-rank covariance approximation, the updated ensemble members become correlated samples from the posterior distribution. We suggest using multiple EnKF runs, each with a smaller ensemble size, to obtain truly independent samples from the posterior distribution. This allows a pointwise confidence interval to be constructed for the posterior cumulative distribution function (CDF). We investigate the methodology for finding an optimal combination of ensemble batch size n and number of EnKF runs m while keeping the total number of ensemble members n×m constant. The optimal combination of n and m is found through minimizing the integrated mean-square error (MSE) for the CDFs. We illustrate the approach on two models, first a small linear model and then a synthetic 2D model inspired by petroleum applications. In the latter case, we choose to define an EnKF run with 10,000 ensemble members as having zero Monte Carlo error. The proposed methodology should be applicable also to larger, more-realistic models.
A Comprehensive Modeling Analysis of Borehole Stability and Production-Liner Deformation for Inclined/Horizontal Wells Completed in a Highly Compacting Chalk Formation
Authors: Furui K.. , Fuh G.-F.. -F. , Abdelmalek N.. , Morita N..
Published: October 2010

Numerous casing and production-liner deformation/failure problems have been reported in high-porosity chalk formations in both the overburden and the reservoir sections, causing costly operation problems that prevent workovers and recompletions. This paper presents the results of studies performed to investigate stability of an openhole, cemented liner and uncemented-liner completions in a highly compacting chalk formation. The effects of critical cavity dimensions caused by various acid-stimulation techniques were also investigated.

On the basis of the review of historical caliper-survey data, we ascertain that axial-compression collapse is a major liner-deformation mechanism in the reservoir zones. Axial-compression collapse has been found in both low-angle wells (also in buildup sections of horizontal wells) and horizontal laterals. The casing deformation in low-angle sections is a result of reservoir compaction (i.e., change in the vertical formation strain), while the deformation in horizontal sections is primarily induced by increased axial loading because of cavity deformation. The current completion practice using cluster perforations and high-volume acid treatments causes vertically enlarged cavities, resulting in poor radial constraint.

A series of laboratory triaxial tests was performed on selected reservoir chalk samples to measure the stress/strain and failure behavior of the chalk formation considering a wide range of porosity and water saturation and different levels of confining pressures. Using the chalk-failure criteria and constitutive relations developed from the analysis of laboratory triaxial-compression-test data, a 3D nonlinear poroelastic/plastic finite-element-method (FEM) model was developed for the openhole stability analysis. The simulation results show that the abnormally high ductility of chalks after pore collapse around a borehole could actually enhance borehole stability, with a magnitude beyond expectation.

In this study, analytical and numerical models are also developed for evaluating cavity-induced axial-compression collapse of production liners. Model results indicate that the risk of the cavity-induced axial-compression collapse substantially increases for short perforated intervals stimulated with large acid treatments. However, increasing the perforation-interval lengths along the entire liner axis results in more-uniform acid distribution and will greatly reduce the chance of axial-compression collapse caused by localized cavity deformation. On the basis of these analysis results, key completion design criteria and stimulation strategies were developed for wells completed in highly compacting chalk reservoirs to reduce risk of casing and liner mechanical problems.
Integrated Surveillance Enhancing Quality of Decisions and Reservoir Description in the Harding Field
Authors: Zett Adrian , Webster Mike , Davies Chris , Zhang Pinggang , Mukerji Parijat
Published: October 2010

A key factor in managing mature fields is to establish adequate surveillance in each phase of their life. The complexity increases when the field is developed with horizontal wells. Differences in data quality and resolution should be taken into consideration when planning such surveillance. Current uncertainties in Harding field relate to unreliable well conformance data using conventional production logs (PL) and assumptions in the reservoir description, which are subseismic resolution. We describe the learning from a horizontal well in Harding, where appropriate surveillance enhanced reservoir understanding and quality of decision making.

Based on the initial understanding from the reservoir model, an insert string well work option was proposed to reduce water cut. Historically in this field, conventional PLs provided unreliable well conformance data in horizontal multiphase flow. To improve the characterization at the well scale, an array PL was deployed for the first time on this field.

The flowing results revealed that the insert string solution was inappropriate and would result in lost oil production. The shut-in data identified crossflow between two zones separated by a shale section. In the initial model, this shale was mapped only at local level. Post surveillance, it was remapped on seismic as an extensive baffle having an impact on an area with more mobile oil to recover. There is a potential upside with a new infill target being identified toward the toe of this well.

Most of the initial decisions about the insert string were based on seismic and modeling work. The new array PL data brought additional information into the model, increasing confidence in the results. Data resolution at the well level matters and this highlights the need to take more PL measurements to calibrate the seismic response and improve the reservoir model.
The Equations Archie Forgot: Anisotropy of the Rocks
Authors: Haro Carlos F.
Published: October 2010

Archie's empirical equation is used extensively to estimate hydrocarbons in place. This power-laws combination has stood the test of time with few changes. However, it is still poorly understood and considered an ad hoc relation. Our original analysis will prove these laws rigorously, show how they must be amended, and introduce additional accompanying equations. This comprehensive model, which represents the electrical flow through the intricate conductive paths of the rock, is confirmed with Archie's and Hamada's core data sets. It corrects for Archie's inaccuracies.

A thorough appreciation of the pore-scale physics behind the modified version of Archie's equation is presented. The principles can be applied in clean and complex formations (shaly sands, thin beds, and vuggy or fractured carbonates) to obtain enhanced values of water saturation. The theory sheds light on the role and quantification of anisotropy.

Solving for the elaborate pore geometry, we use the Laplace differential equation (not Ohm's law), appropriate in the analysis of electrostatic fields in charge-free regions. Rock morphology dictates its boundary conditions (Jin 2007; Ghous 2005), characterized as corner angles. The corresponding particular solution (flow around a corner) and modeling tactic delineate the streamlines throughout the pores. The angles establish strong mathematical links among the exponents of Archie's equation, the geometry of the rock frame, and the spatial fluid distribution. This quantitative method is lacking in previous saturation models.

The solution constitutes the basis to solve more-complicated rock layouts. It enables the calculation of equivalent resistivities (normalized resistances) to take advantage of well-established electrical relationships. The extra equations compute the variable exponents and coefficients of Archie's equation at every depth. They obtain the saturation exponent in clean rocks as a function of water saturation, crucial to the quality control of core electrical data and to the quantification of reservoirs under changing saturation (waterflooding). Therefore, improved calculations of original and remaining hydrocarbons are achieved.
Determining Trapped Gas in Foam From Computed-Tomography Images
Authors: Kil R.A.. A. , Nguyen Q.P.. P. , Rossen W.R.. R.
Published: October 2010

Gas trapping by foam is a key mechanism of foam mobility and foam effectiveness in applications such as acid diversion in well stimulation, enhanced oil recovery (EOR), and aquifer remediation. Previous studies have attempted to quantify the extent of gas trapping by injecting a tracer gas within the foam and then fitting the effluent profile to a 1D capacitance model. In this model, at any given axial position along the core, all flowing gas and all trapped gas are each characterized by a single tracer concentration. Computed-tomography (CT) images of experiments using xenon (Xe) tracer show that this characterization is not accurate: Trapped gas near flowing gas comes rapidly to equilibrium with flowing gas long before tracer diffuses into trapped gas farther away.

We introduce a method that uses the CT images directly to estimate flowing-gas fraction. In the CT images, tracer advances in many small channels and diffuses outward into surrounding regions of trapped gas a few millimeters in diameter. The difference between the higher tracer concentration at the center of these channels and the lower concentration at the edge can be related to the diffusion coefficient of the tracer and the flowing-gas fraction within the channel. For the CT images of Xe tracer in one experiment, this method gives flowing-gas fractions one or two orders of magnitude smaller than what is estimated using the 1D capacitance model. The model can be used to estimate flowing-gas fraction in different regions of a core in spite of different average gas velocities in the different regions.
Hierarchical Long-Term and Short-Term Production Optimization
Authors: van Essen G.M.. M. , Van den Hof P.M.J.. M.J. , Jansen J.D.. D.
Published: October 2010

Model-based dynamic optimization of oil production has a significant potential to improve economic life-cycle performance, as has been shown in various studies. However, within these studies, short-term operational objectives are generally neglected. As a result, the optimized injection and production rates often result in a considerable decrease in short-term production performance. In reality, however, it is often these short-term objectives that dictate the course of the operational strategy. Incorporating short-term goals into the life-cycle optimization problem, therefore, is an essential step in model-based life-cycle optimization. We propose a hierarchical optimization structure with multiple objectives. Within this framework, the life-cycle performance in terms of net present value (NPV) serves as the primary objective and shortterm operational performance is the secondary objective, such that optimality of the primary objective constrains the secondary optimization problem. This requires that optimality of the primary objective does not fix all degrees of freedom (DOF) of the decision variable space. Fortunately, the life-cycle optimization problem is generally ill-posed and contains many more decision variables than necessary. We present a method that identifies the redundant DOF in the life-cycle optimization problem, which can subsequently be used in the secondary optimization problem. In our study, we used a 3D reservoir in a fluvial depositional environment with a production life of 7 years. The primary objective is undiscounted NPV, while the secondary objective is aimed at maximizing shortterm production. The optimal life-cycle waterflooding strategy that includes short-term performance is compared to the optimal strategy that disregards short-term performance. The experiment shows a very large increase in short-term production, boosting first-year production by a factor of 2, without significantly compromising optimality of the primary objective, showing a slight drop in NPV of only -0.3%. Our method to determine the redundant DOF in the primary objective function relies on the computation of the Hessian matrix of the objective function with respect to the control variables. Although theoretically rigorous, this method is computationally infeasible for realistically sized problems. Therefore, we also developed a second, more pragmatic, method relying on an alternating sequence of optimizing the primary-and secondary-objective functions. Subsequently, we demonstrated that both methods lead to nearly identical results, which offers scope for application of hierarchical long-term and short-term production optimization to realistically sized flooding-optimization problems.
Oil, Natural-Gas, and NGL Endowment in North, Central, and South America
Authors: Aguilera Roberto F. , Aguilera Roberto
Published: October 2010

This study uses the United States Geological Survey (USGS) World Petroleum Assessment (USGS World Energy Assessment Team 2000) as a starting point. Then, it uses a previously defined variable-shape-distribution (VSD) model for estimating the endowment of oil, natural gas, and natural-gas liquids (NGL) throughout North, Central, and South America.

Use of the VSD model is validated by an excellent fit with actual data, supported by coefficients of determination (R2) equal to 0.98 or greater. The study includes endowments in petroleum provinces not assessed previously by other organizations. Endowment, as defined by the USGS, refers to the sum of known volumes of hydrocarbons (cumulative production plus remaining reserves) and undiscovered volumes. Petroleum is the sum of oil, natural gas, and NGL.

The importance of North, Central, and South America is highlighted by a hydrocarbon output during 2007 that accounted for 25% of the world oil production and more than 31% of the natural-gas production.

It is concluded that there is a large petroleum endowment in North, Central, and South America that will last for several decades and will help to contribute significantly to the energy needs of these regions. It is recommended to actively pursue research and development of this endowment.
Extraction of Dissolved Methane in Brines by CO2 Injection: Implication for CO2 Sequestration
Authors: Taggart Ian
Published: October 2010

The solubility of carbon dioxide (CO2) in underground saline formations is considered to offer significant long-term storage capability to effectively sequester large amounts of anthropogenic CO2. Unlike enhanced oil recovery (EOR), geosequestration relies on longer time scales and involves significantly greater volumes of CO2. Many geosequestration studies assume that the initial brine state is one containing no dissolved hydrocarbons and, therefore, apply simplistic two-component solubility models starting from a zero dissolved-gas state. Many brine formations near hydrocarbons, however, tend to be close to saturation by methane (CH4). The introduction of excess CO2 in such systems results in an extraction of the CH4 into the CO2-rich phase, which, in turn, has implications for monitoring of any sequestration project and offers the possibly additional CH4 mobilization and recovery.
Spoolable Connector Allows Coiled-Tubing Operations Offshore India
Authors: Effiong G.. , Dean G.. , Nayak S.. , Satyarthi R.S.. S.
Published: October 2010

Available footprint on offshore platforms (Fig. 1) can be a significant challenge for coiled-tubing (CT) operations. Many times, platform limitations require that a smaller CT unit be deployed for work that would be faster and easier operationally with CT of a larger diameter. Often the platform's crane capacity dictates the size of CT used, which in turn reduces the working envelope of the CT.

Some wells offshore India are completed horizontally and require intervention using larger sizes of CT in order to gain horizontal reach and manipulate sliding sleeves. When CT is used for these operations, the weight of the CT reel itself is critical to the effectiveness of the overall operation and requires proper management. Traditional methods of managing/reducing CT-reel weight involve spooling the CT string from a boat to the platform or joining CT sections by butt welding on the platform. Bringing the required length of CT onboard in two or more sections and joining them with a spoolable connector provides significant benefits over the traditional methods. The use of just one spoolable connector can reduce the maximum CT-reel lifting weight by typically 30 to 40% while increasing the CT size by one or two gauge sizes.

This paper describes the results of a feasibility study performed to address typical challenges and presents actual case histories in which a spoolable connector was used to connect two CT strings. Required equipment was built and mobilized so that two separate strings could be joined on the platform with the aid of a connecting jig. Several trips were performed safely without the need to change the spoolable connector. Specific benefits of the spoolable connector over the traditional methods are explained. Methods to monitor the usable life of the spoolable connector while tripping in and out of the well (Fig. 2) will also be discussed, as well as new developments currently under way.
Experimental and Numerical Modeling of Three-Phase Flow Under High-Pressure Air Injection
Authors: Niz-Velásquez E. , Moore R.G.. G. , van Fraassen K.C.. C. , Mehta S.A.. A. , Ursenbach M.G.. G.
Published: October 2010

In this paper, an improved characterization of three-phase flow under high-pressure-air-injection (HPAI) conditions was achieved on the basis of experimental results and numerical reservoir simulation.

A three-phase coreflood experiment was conducted at reservoir conditions, using 37°API stock-tank oil, an 84% nitrogen and 16% carbon dioxide flue-gas mixture, and 3% potassium chloride brine. The aim of the test was to evaluate the effects that the highly liquid-saturated front produced by the thermal reactions has on the mobility of each phase. Departing from connate-water saturation and reservoir pressure and temperature, sequential injection of water, gas, and oil was carried out, followed by a final gasflood to residual liquid saturation. Other two- and three-phase tests performed on this rock specimen were published elsewhere (Niz-Velásquez et al. 2009). Numerical history matching was employed to determine oil/water and liquid/gas relative permeability (kr) curves for both imbibition and drainage cases. A combustion-tube (CT) test was simulated using conventional kr curves and a set that included hysteresis. The degree of hysteresis observed during the coreflood test was maintained for the CT simulation.

History matching of the coreflood showed that kr to the gas phase is much smaller during liquid reimbibition than during drainage. The use of gas-phase hysteresis for the CT test allows for a better matching of liquid volumes and pressure drop. Analysis of the simulated data suggests that the reduction in gas-phase mobility encourages an early increase in the oil rate, which is more consistent with experimental data than what is predicted by a model with conventional kr. The analysis also reveals that water distilled below the saturated steam temperature plays an important role in the increase of liquid saturation and oil mobilization.

The improved characterization of relative permeability considering gas-phase hysteresis for simulating HPAI enhances the predictive capability of available commercial simulators, providing a more certain method to evaluate the technical and economical feasibility of a project. The ability to predict an early increase in oil rate, consistent with experimental observations, results in improved economics for the project.
Use of Biodiesel as an Additive in Thermal Recovery of Heavy Oil and Bitumen
Authors: Babadagli Tayfun , Er Vahapcan , Naderi Khosrow , Burkus Zvonko , Ozum Baki
Published: October 2010

Bitumen extraction in oil sands-ore water slurry systems was studied by using lipids and lipid derivatives such as biodiesel (BD) as surfactant additive to promote bitumen recovery efficiency. Performance of BDs (i.e., canola and tall oil, a by-product of pulp mills using the bleached Kraft process) fatty acids methyl ester and food-grade fatty acids monoglycerides were evaluated as surfactant additives. Experimental findings suggest that BDs such as fatty acids methyl esters could also be used as surfactant additives to increase the efficiency of bitumen recovery in thermal in-situ processes such as steam assisted gravity drainage (SAGD) and cyclic steam stimulation (CSS) processes. The required dosage for the surfactant additive is about 0.1% of bitumen by mass. Also, interfacial tension measurements between bitumen and process water (YB,W) and BD and process water (YBD,W) support the surfactant behavior of BD.
Optimization of Liquid and Gas Flow Rates for Aerated Drilling Fluids Considering Hole Cleaning for Vertical and Low Inclination Wells
Authors: Ozbayoglu Evren M.
Published: October 2010

Underbalanced drilling (UBD) is one of the most widely used technologies preferred in depleted and/or low-pressured formations. In order to achieve underbalanced conditions, drilling fluids are usually gasified. Major drilling fluids preferred during UBD are pure gas, gas-liquid mixtures, and foams. This study is focused on gas-liquid mixtures. As the gas is introduced, the behaviour of the drilling fluid becomes hard to explain for many reasons. First of all, gas is compressible and physical properties of gas are very sensitive to changes in pressure and temperature. Second, a multiphase flow phenomenon arises. When there is multiphase flow, flow patterns should be considered. It is known that there is a difficulty to predict hydraulic behaviour of gas-liquid mixtures owing to this flow pattern dependence. During a drilling operation, one of the parameters that should be considered is hole cleaning. Hole cleaning is a challenging task even for a single-phase drilling fluid. Moreover, there is still a lack of information about how the cuttings are transported when gas-liquid mixtures are used as drilling fluids. Flow-rate optimization during UBD operations for liquid and gas phases are usually conducted based on formation pressures only. However, considering only this criterion as the optimization objective is misleading and may cause serious problems during the drilling operation. In this study, gas and liquid flow rates during UBD operations are conducted not only based on formation pressures, but also based on effective hole cleaning. It is assumed that liquid phase is the major contributor for cuttings transport, and gas phase is only influencing the bottomhole pressure. A mechanistic model is introduced for estimating the hydraulic behaviour of gas-liquid mixture drilling fluids under different flow patterns. Based on the bottomhole pressure and effective hole cleaning point of view, an algorithm is proposed for estimation of the optimum required flow rates for liquid and gas phases based on the introduced mechanistic model. Also, the model predicts the required backpressure that has to be applied.
Optimal Parametric Design for Water-Alternating-Gas (WAG) Process in a CO2-Miscible Flooding Reservoir
Authors: Chen S. , Li H. , Yang D. , Tontiwachwuthikul P.
Published: October 2010

A pragmatic method has been developed to efficiently design the production-injection parameters to optimize the water-alternating-gas (WAG) performance in a field-scale CO2-miscible flooding project. The net present value (NPV) is selected as the objective function, while the controlling variables are chosen to be the injection rates, ratios of gas slug size to water slug size (WAG ratio) and cycle time (i.e., the injection time for each gas or water slug) for the injectors and bottomhole pressures (BHPs) for the producers. A hybrid technique, which integrates the orthogonal array (OA) and Tabu technique into the genetic algorithm (GA), is then developed and employed to determine the optimum WAG production-injection parameters. Sensitivity analysis of the WAG parameters on oil recovery is conducted and a field case is finally presented to demonstrate the successful application of the newly developed technique.
Analysis of Air Pollution from Swine Production by Using Air Dispersion Model and GIS in Quebec
Authors: Sarr Joachim H. , Goïta Kalifa , Desmarais Camille
Published: October 2010

Swine production, the second most important contributor to Quebec's agricultural revenue, faces many problems. Intensive piggeries, with up to 599 animal units, are used to raise finishing pigs for slaughter. Among the great number of gaseous species emitted to the atmospheric environment from livestock buildings and manure storage units is NH3, which is one of the most important and most offensive with respect to human health. Under appropriate meteorological and topographical conditions, gaseous contaminants can spread and cause a public nuisance—up to a 1‐km radius around the farm. To mitigate these effects, the Quebec Government adopted regulations that set minimum buffer distances to be observed by any expansion of an existing or new pig farm. The objectives of this study were (i) to assess the efficiency of the current buffer distance prescriptions in Quebec in mitigating effects of air pollution from swine units and (ii) to identify potential areas for establishing pig farm operations that will not be offensive to people. The air dispersion American Meteorological Society/Environmental Protection Agency Regulatory Model (AERMOD) with receptors distributed at 1.6 km around each source was used first, followed by a spatial geographic information system (GIS) model. Results from the dispersion model showed that the highest hourly concentration with a 99.5% compliance frequency for a single farm was 3078.1 μg/m3 and exceeded the NH3 odor criterion hourly standard set by the Quebec Government at 183.4 μg/m3 Thus, for public safety, densely populated areas like housing developments must be located >1300 m from a pig farm. This distance is in the range of setback distances (723 to 1447 m) obtained by using abacuses defined in the L'Erable Regional County Municipality. That is why we can say the current rules established by the Quebec Government, if rigorously applied, can prevent odor nuisance, due to NH3 emission, from swine farms. In the spatial model, buffer zones were established around houses, roads, waterways, and drinking water intakes. By combining layers of information in the ArcGIS Model Builder, potential areas in which pig farms can be installed, without public odor nuisance, were identified.