bluuebunny/crossref_metadata_2025 huggingface dataset:
Paternal Influences on Adolescent Sexual Risk Behaviors: A Structured Literature Review
Authors: Guilamo-Ramos Vincent , Bouris Alida , Lee Jane , McCarthy Katharine , Michael Shannon L. , Pitt-Barnes Seraphine , Dittus Patricia
Published: October 2012

BACKGROUND AND OBJECTIVE:

To date, most parent-based research has neglected the role of fathers in shaping adolescent sexual behavior and has focused on mothers. The objective of this study was to conduct a structured review to assess the role of paternal influence on adolescent sexual behavior and to assess the methodological quality of the paternal influence literature related to adolescent sexual behavior.

METHODS:

We searched electronic databases: PubMed, PsychINFO, Social Services Abstracts, Family Studies Abstracts, Sociological Abstracts, and the Cumulative Index to Nursing and Allied Health Literature. Studies published between 1980 and 2011 that targeted adolescents 11 to 18 years and focused on paternal parenting processes were included. Methodological quality was assessed by using an 11-item scoring system.

RESULTS:

Thirteen articles were identified and reviewed. Findings suggest paternal factors are independently associated with adolescent sexual behavior relative to maternal factors. The most commonly studied paternal influence was emotional qualities of the father-adolescent relationship. Paternal communication about sex was most consistently associated with adolescent sexual behavior, whereas paternal attitudes about sex was least associated. Methodological limitations include a tendency to rely on cross-sectional design, nonprobability sampling methods, and focus on sexual debut versus broader sexual behavior.

CONCLUSIONS:

Existing research preliminarily suggests fathers influence the sexual behavior of their adolescent children; however, more rigorous research examining diverse facets of paternal influence on adolescent sexual behavior is needed. We provide recommendations for primary care providers and public health practitioners to better incorporate fathers into interventions designed to reduce adolescent sexual risk behavior.
Pediatric Chronic Nonbacterial Osteomyelitis
Authors: Borzutzky Arturo , Stern Sara , Reiff Andreas , Zurakowski David , Steinberg Evan A. , Dedeoglu Fatma , Sundel Robert P.
Published: October 2012

BACKGROUND AND OBJECTIVES:

Little information is available concerning the natural history and optimal treatment of chronic nonbacterial osteomyelitis (CNO). We conducted a retrospective review to assess the clinical characteristics and treatment responses of a large cohort of pediatric CNO patients.

METHODS:

Children diagnosed with CNO at 3 tertiary care centers in the United States between 1985 and 2009 were identified. Their charts were reviewed, and clinical, laboratory, histopathologic, and radiologic data were extracted.

RESULTS:

Seventy children with CNO (67% female patients) were identified. Median age at onset was 9.6 years (range 3–17), and median follow-up was 1.8 years (range 0–13). Half of the patients had comorbid autoimmune diseases, and 49% had a family history of autoimmunity. Patients with comorbid autoimmune diseases had more bone lesions (P < .001), higher erythrocyte sedimentation rate (P < .05), and higher use of second line therapy (P = .02). Treatment response to nonsteroidal antiinflammatory drugs (NSAIDs), sulfasalazine, methotrexate, tumor necrosis factor α inhibitors, and corticosteroids was evaluated. The only significant predictor of a positive treatment response was the agent used (P < .0001). Estimated probability of response was 57% for NSAIDs, 66% for sulfasalazine, 91% for methotrexate, 91% for tumor necrosis factor α inhibitors, and 95% for corticosteroids.

CONCLUSIONS:

In a US cohort of 70 children with CNO, coexisting autoimmunity was a risk factor for multifocal involvement and treatment with immunosuppressive agents. Disease-modifying antirheumatic drugs and biologics were more likely to lead to clinical improvement than NSAIDs.
Effects of School-Wide Positive Behavioral Interventions and Supports on Child Behavior Problems
Authors: Bradshaw Catherine P. , Waasdorp Tracy E. , Leaf Philip J.
Published: October 2012

OBJECTIVE:

School-Wide Positive Behavioral Interventions and Supports (SWPBIS) is a universal prevention strategy currently implemented in >16 000 schools across the United States. SWPBIS intends to reduce students’ behavior problems by altering staff behaviors and developing systems and supports to meet children’s behavioral needs. The current study reports intervention effects on child behaviors and adjustment from an effectiveness trial of SWPBIS.

METHODS:

The sample of 12 344 elementary school children was 52.9% male, 45.1% African American, and 46.1% Caucasian. Approximately 49% received free or reduced-priced meals, and 12.9% received special education services at baseline. The trial used a group randomized controlled effectiveness design implemented in 37 elementary schools. Multilevel analyses were conducted on teachers’ ratings of children’s behavior problems, concentration problems, social-emotional functioning, prosocial behavior, office discipline referrals, and suspensions at 5 time points over the course of 4 school years.

RESULTS:

The multilevel results indicated significant effects of SWPBIS on children’s behavior problems, concentration problems, social-emotional functioning, and prosocial behavior. Children in SWPBIS schools also were 33% less likely to receive an office discipline referral than those in the comparison schools. The effects tended to be strongest among children who were first exposed to SWPBIS in kindergarten.

CONCLUSIONS:

These findings provide support for the hypothesized reduction in behavior problems and improvements in prosocial behavior and effective emotion regulation after training in SWPBIS. The SWPBIS framework appears to be a promising approach for reducing problems and promoting adjustment among elementary school children.
Variation in Occult Injury Screening for Children With Suspected Abuse in Selected US Children’s Hospitals
Authors: Wood Joanne N. , Feudtner Chris , Medina Sheyla P. , Luan Xianqun , Localio Russell , Rubin David M.
Published: October 2012

OBJECTIVE:

To describe variation across selected US children’s hospitals in screening for occult fractures in children <2 years old diagnosed with physical abuse and in infants <1 year old who have injuries associated with a high likelihood of physical abuse.

METHODS:

We performed a retrospective study of children <2 years old with a diagnosis of physical abuse and infants <1 year old with non-motor vehicle crash–associated traumatic brain injuries or femur fractures admitted to 40 hospitals within the Pediatric Hospital Information System database from January 1, 1999, to December 31, 2009. We examined variation among the hospitals in the performance of screening for occult fractures as defined by receipt of skeletal survey or radionuclide bone scan. Marginal standardization implemented with logistic regression analysis was used to examine hospital variation after adjusting for patient demographic characteristics, injury severity, and year of admission.

RESULTS:

Screening for occult fractures was performed in 83% of the 10 170 children <2 years old with a diagnosis of physical abuse, 68% of the 9942 infants who had a traumatic brain injury, and 77% of the 2975 infants who had femur fractures. After adjustment for patient characteristics, injury severity, and year of admission, hospitals varied significantly in use of screening for occult fractures in all 3 groups of children.

CONCLUSIONS:

The observed variation in screening for occult fractures in young victims of physical abuse and infants who have injuries associated with a high likelihood of abuse underscores opportunities to improve the quality of care provided to this vulnerable population.
Metformin's Effect on First-Year Weight Gain: A Follow-up Study
Authors: Carlsen Sven M. , Martinussen Marit P. , Vanky Eszter
Published: October 2012

BACKGROUND:

The impact of metformin medication in pregnant women with polycystic ovary syndrome on weight gain during pregnancy and after delivery and the impact on growth of the offspring are essentially unexplored.

METHODS:

This is a follow-up study of a randomized controlled trial (The Metformin treatment in pregnant PCOS women study), conducted in 11 secondary care centers. Women with PCOS were randomized to metformin (2000 mg daily) or placebo from first trimester to delivery. Questionnaires were sent to 256 participants 1 year postpartum. Maternal weight development in pregnancy and the first year after delivery and offspring anthropometry at birth and weight 1 year postpartum were registered.

RESULTS:

Women randomized to metformin gained less weight during pregnancy compared with those in the placebo group. In the newborns, there was no difference between the 2 groups in weight or length. One year postpartum, women who used metformin in pregnancy lost less weight and their infants were heavier than those in the placebo group (10.2 ± 1.2 kg vs 9.7 ± 1.1 kg, P = .003).

CONCLUSIONS:

Women randomized to metformin were heavier in the first trimester, gained less weight in pregnancy, and lost less weight in the first year postpartum compared with women randomized to placebo. Children exposed to metformin weighed more at 1 year of age.
A Technique to Facilitate the Fabrication of Provisional Restorations for ITI Solid Abutments
Authors: Kurt Murat , Güler Ahmet Umut , Erkoçak Ayça , Şanal Fatma Ayşe
Published: October 2012

The aim of this technique report was to present a procedure for the fabrication of provisional restorations for ITI solid abutments using impression caps in the laboratory with a number of advantages over intraoral techniques. There may be no need for cementation, and elimination of cementation may assist tissue healing.
Cell Culture–Based Tissue Engineering as an Alternative to Bone Grafts in Implant Dentistry: A Literature Review
Authors: Boeckel Daniel Gonçalves , Shinkai Rosemary Sadami Arai , Grossi Márcio Lima , Teixeira Eduardo Rolim
Published: October 2012

Several biomaterials and techniques for bone grafting have been described in the literature for atresic bone tissue replacement caused by edentulism, surgical resectioning, and traumas. A new technique involves tissue engineering, a promising option to replace bone tissue and solve problems associated with morbidity of autogenous grafting. This literature review aims to describe tissue-engineering techniques using ex vivo cell culture as an alternative to repair bone maxillary atresias and discuss the concepts and potentials of bone regeneration through cell culture techniques as an option for restorative maxillofacial surgery.
Projeto de observadores de fluxo para o controle por orientação direta do campo em máquinas de indução pentafásicas
Authors: Benavides Micaela , Pereira Luís Fernando Alves , Coutinho Daniel Ferreira , Pereira Luís Alberto
Published: October 2012

Apresenta-se neste artigo a aplicação de técnicas de otimização convexa para o projeto de observadores robustos aplicados a motores de indução pentafásicos, sujeitos a variações na resistência do rotor e a perturbações de carga. É desenvolvido um estimador robusto para os fluxos do primeiro e terceiro harmônico do rotor, cuja validação é realizada junto ao controle por orientação de campo no modo direto admitindo aplicações que exijam elevado desempenho dinâmico e alta robustez frente a variações paramétricas e distúrbios externos.
Localização de faltas em linhas de transmissão com múltiplas derivações utilizando dados de somente dois terminais
Authors: Santo Silvio Giuseppe Di , Pereira Carlos Eduardo de Morais , Zanetta Jr Luiz Cera
Published: October 2012

Um novo método de localização de faltas em linhas de transmissão continuamente transpostas e com múltiplas derivações é apresentado neste artigo. O mesmo é baseado nos fasores de tensão e corrente, pré-falta e pós-falta, medidos em regime permanente nos terminais local e remoto, para determinar as informações de falta, tais como: o trecho de ocorrência, a distância de falta, ou seja, o ponto de ocorrência, e a resistência. A principal caracterstica deste novo método é o processo de varredura da rede, onde a falta é localizada dentro de cada um dos trechos da linha, buscando-se minimizar por meio de uma função objetivo, as diferenças entre as tensões e correntes medidas e calculadas nos terminais local e remoto. O erro calculado pela função objetivo, no caso de a falta estar em um determinado trecho, é comparado com o erro obtido para o trecho anterior, sendo o trecho com o maior erro descartado. No final do processo de varredura, o método de localização de faltas tem como resultado o trecho de ocorrência, a distância e a resistência da falta. Os resultados das simulações mostram a eficiência e a precisão do método proposto frente a variação da distância, resistência e tipo da falta.
Fluxo de potência AC para operação independente de áreas interligadas
Authors: Echeverri Mauricio Granada , Rider Marcos J. , Mantovani José R. Sanches
Published: October 2012

Neste artigo utiliza-se um método de decomposição matemática para resolver um problema de fluxo de carga AC em sistemas de potência compostos de áreas interligadas e administradas por diferentes operadores regionais do sistema elétrico (ORS). A estratégia proposta permite encontrar o ponto de operação de uma determinada área sem conhecer explicitamente os dados da rede das outras áreas interligadas, sendo necessária apenas a troca de informações de fronteira associadas às linhas de interligação. A metodologia baseia-se na decomposição das condições de otimalidade de primeira ordem do fluxo de potência AC que, por sua vez, é formulado como um problema de programação não-linear. Para visualizar melhor o conceito de operação independente de cada ORS, usou-se uma rede neural artificial para simular os cálculos das variáveis de fronteira dos ORS interligados. Um fluxo de carga multi-áreas pode ser visto como uma ferramenta básica que pode ser usada no âmbito de mercados competitivos multi-agentes. O sistema de teste IEEE RTS-96 é utilizado para demonstrar o funcionamento e a eficácia do fluxo de potência AC multi-áreas.
Genetic algorithms applied to a faster distance protection of transmission lines
Authors: Coury Denis V. , Oleskovicz Mário , Souza Silvio A.
Published: October 2012

The main purpose of this paper is to implement a new methodology based on Genetic Algorithms (GAs) to extract the fundamental voltage and current phasors from noisy waves in power systems to be applied to a faster distance protection. GAs solve optimization problems based on natural selection principles. This application was then formulated as an optimization problem, and the aim was to minimize the estimation error. A 440 kV, 150 km transmission line was simulated using the ATP (Alternative Transients Program) software in order to show the efficiency of the new method. The results from this application show that the global performance of GAs was highly satisfactory concerning speed and accuracy of response, if compared to the traditional Discrete Fourier Transform (DFT).
Redes dinâmicas cognitivas aplicadas no controle supervisório de um fermentador
Authors: Mendonça Márcio , Arruda L. V. R. , Neves-Jr Flávio
Published: October 2012

Este trabalho usa redes cognitivas dinâmicas (Dynamic Cognitive Networks - (DCN), como uma ferramenta inteligente para controle supervisório. As DCNs são uma evolução dos mapas cognitivos fuzzy (Fuzzy Cognitve Map - FCM). Os sistemas inteligentes se baseiam no conhecimento de especialistas a fim de construir modelos com capacidade de inferência e/ou tomada de decisão. Uma arquitetura de controle supervisório para um processo de fermentação alcoólica é desenvolvida a partir da aquisição de conhecimento empírico de um especialista. O objetivo do supervisor é operar o processo em situações normal e crítica. Para isto, propõe-se o uso de uma DCN que incorpora novos tipos de conceitos e relações que não apenas as relações de causa-efeito presentes nos modelos baseados em FCMs. Resultados de simulação são apresentados para validar a arquitetura desenvolvida.
A component-based architecture for robot control
Authors: Santini Diego Caberlon , Lages Walter Fetter
Published: October 2012

This work deals with the specification of an open architecture for control of manipulator robots. The architecture defines policies for the use of the OROCOS framework and is specified for a generic manipulator robot with N joints, through the definition of component models to abstract the hardware and each block of the robot controller. To show its generality, the proposed architecture is used to implement two different controllers: an independent PID for each joint and controller with feedforward compensation. The validation is made through the implementation in real-time on the Janus robot.
Lógica nebulosa aplicada à proteção diferencial de transformadores de potência
Authors: Barbosa Daniel , Chemin Netto Ulisses , Coury Denis V , Oleskovicz Mário
Published: October 2012

Este artigo apresenta um algoritmo baseado na lógica nebulosa para a proteção diferencial de transformadores de potência. A abordagem nebulosa utilizada neste trabalho permite detectar os defeitos internos, distinguindo-os de outras situações operativas, como a energização, a energização solidária e a sobre-excitacão. O sistema elétrico de potência, incluindo o transformador estudado, foi modelado utilizando-se do software ATP (Alternative Transients Program) para gerar dados de situações de operação e falta, as quais são empregadas durante a etapa de testes do algoritmo proposto. Cabe comentar que na validação, os resultados foram comparados com um relé digital comercial, mostrando as vantagens do método proposto.
Pré-despacho hidrotérmico de potência ativa e reativa via método dos Pontos Interiores e coordenadas retangulares
Authors: Borges Saimon S , Fernandes Thelma S. Piazza , Almeida Katia Campos de
Published: October 2012

Este artigo apresenta a formulação matemática de um problema de pré-despacho de geração de potência ativa e reativa no qual a função objetivo engloba minimização dos custos de usinas térmicas e minimização das perdas elétricas na transmissão. A representação do fasor tensão é feita em coordenadas retangulares, consideram-se os limites de transmissão utilizando a formulação linearizada e o problema de otimização é resolvido pelo Método de Pontos Interiores versão Primal-Dual. A eficiência da formulação é testada utilizando-se o sistema de 5 barras e o sistema de 291 barras que representa o sistema elétrico reduzido do estado do Paraná.
Influência da dependência de parâmetros do solo com a frequência na modelagem de linhas aéreas de transmissão: caso de condutor único
Authors: Gertrudes J. B , Tavares M. C , Portela C
Published: October 2012

Este trabalho enquadra-se na linha de pesquisa que tem como objetivo a busca de modelos mais precisos para cálculo de parâmetros de linhas aéreas de transmissão na faixa de frequência 0 a 2 MHz. Esta faixa de frequência cobre a maioria das perturbações eletromagnéticas nos sistemas elétricos (manobras, ocorrências de faltas, rejeições de carga, descargas atmosféricas, perturbações harmônicas). Entre 1 Hz e 2 MHz o solo pode ter a condutividade elétrica da mesma ordem de grandeza que o produto entre a constante dielétrica e a frequência angular do sinal incidente no solo, em função da dependência desses parâmetros com a frequência. Consequentemente, as suposições de baixa frequência tradicionalmente adotadas - condutividade do solo constante e permissividade desprezível - podem levar a modelos que não representam de forma adequada a resposta da linha no caso de transitórios rápidos (com espectro de frequência acima de 1 kHz). É apresentado um estudo dos parâmetros de uma linha formada por um único condutor acima de solo condutor imperfeito, - onde a impedância e a admitância de retorno pelo solo são avaliadas através de métodos tradicionais de cálculo e através de integração numérica das formulações de Carson modificadas para inclusão do modelo de solo com parâmetros dependentes da frequência.
Determinação do intervalo de manutenção programada da proteção de linhas de transmissão considerando-se penalidades associadas à indisponibilidade
Authors: Pereira Felipe E. L , Prada Ricardo B , Melo Albert C. G. de , Rodrigues Anselmo Barbosa , Silva Maria da Guia da
Published: October 2012

Atualmente, a ANEEL (Agência Nacional de Energia Elétrica) aplica penalidades nas empresas de transmissão devido aos desligamentos programados e não-programados. O uso destas penalidades tem como objetivo assegurar a confiabilidade do serviço de transmissão em um ambiente competitivo. Este artigo propõe um método para minimizar as penalidades associadas com desligamentos de equipamentos de transmissão através da otimização dos intervalos das manutenções programadas. O modelo de otimização proposto neste artigo se baseia em novo método analítico que é capaz de estimar precisamente os valores esperados das penalidades.
Kinematic control of constrained robotic systems
Authors: Freitas Gustavo M. , Leite Antonio C. , Lizarralde Fernando
Published: October 2012

This paper addresses the posture control problem for robotic systems subject to kinematic constraints. The key idea is to consider the kinematic constraints of the mechanisms from their structure equations, instead of explicitly using the constraint equations. A case study for parallel robots and cooperating redundant robots is discussed based on the following concepts: forward kinematics, differential kinematics, singularities and kinematic control. Simulations results, obtained with a Four-Bar linkage mechanism, a planar Gough-Stewart platform and two cooperating robots, illustrate the applicability and versatility of the proposed methodology.
Design of a general brain-computer interface
Authors: Benevides Alessandro B. , Sarcinelli-Filho Mário , Bastos Filho Teodiano F.
Published: October 2012

This paper presents the classification of three mental tasks, using the EEG signal and simulating a real-time process, what is known as pseudo-online technique. The Bayesian classifier is used to recognize the mental tasks, the feature extraction uses the Power Spectral Density, and the Sammon map is used to visualize the class separation. The choice of the EEG channel and sampling frequency is based on the Kullback-Leibler symmetric divergence and a reclassification model is proposed to stabilize the classifications.
That Old Devil Moon
Authors: Chabner Bruce A.
Published: October 2012

This editorial reflects on the history of cancer eradication efforts, including the most recent announcement from the new president of the MD Anderson Cancer Center, Ronald A. DePinho.
Reliability analysis of beams on random elastic foundations
Authors: GRIFFITHS D.V. , PAIBOON J. , HUANG J. , FENTON G.A.
Published: October 2012

The classical problem of a beam on an elastic foundation has long been of practical interest to geotechnical engineers, because it provides a framework for computing deflections not only of foundations, but also of vertically oriented laterally loaded piles. The supporting soil can be modelled as an elastic medium, which can be calibrated to represent the stiffness of the soils adjacent to the beam (or pile). The objective of this paper is to study the influence of spatially random soil stiffness on deformations of transversely loaded homogeneous piles and beams, using a combination of finite-element analysis, random field theory and Monte Carlo simulations. Following code validation against alternative solutions, the method investigates how the statistically defined soil stiffness (mean, standard deviation and spatial correlation length) influences the mean and standard deviation of pile or beam deflection. The goal of such an approach is to estimate the probability of deflections exceeding some design threshold.
Ecosystem change and the Olifants River crocodile mass mortality events
Authors: Woodborne S. , Huchzermeyer K. D. A. , Govender D. , Pienaar D. J. , Hall G. , Myburgh J. G. , Deacon A. R. , Venter J. , Lübcker N.
Published: October 2012

Nile crocodile (Crocodilus niloticus) mass mortality events in the Olifants River between the Letaba River confluence in South Africa and Lake Massingir in Mozambique have been attributed to pansteatitis: a disease that affects fat depots of the animals. The disease is also found in sharptooth catfish (Clarias gariepinus) in the same area, and the cause of the disease is attributed to pollution. Although the Olifants River Valley is polluted, the impact of interventions such as dam construction on biodiversity receives little attention. We show that the onset of the pansteatitis epidemic in crocodiles and sharptooth catfish at the Olifants/Letaba confluence coincided with back‐flooding of Lake Massingir that changed the Olifants River from a rock and sand substrate river to a clay substrate lake. Isotopic analysis shows that sharptooth catfish shifted from a predominantly vegetarian to a piscivorous diet that is highly correlated with pansteatitis prevalence, and crocodiles and tiger fish (Hydrocynus vittatus) show coincident trophic level increases. The evidence suggests that the ecosystem change altered the structure of the lotic foodweb and that an exotic or extralimital fish has invaded the confluence and is the vector of the pansteatitis epidemic. The invasive fish species is yet to be identified. The pansteatitis epidemic is an unintended ecological consequence of damming this river.
A New High Strength Drill Pipe Maximizing Safety and Performace in Low Temperature Enviornments
Authors: El Bachiri K. , Machecourt P. , Mauries S.
Published: October 2012

Extreme low temperature and hostile drilling environments such as the "Arctic" are driving the industry to adapt their drilling programs to new challenges and to develop fit-for-purpose drilling string solutions. Proprietary arctic grades already exist for temperatures as low as −40°C. However, for high-strength drill pipe it is necessary to meet the drilling loads associated to temperatures conditions as low as −60°C. Arctic drilling is one of the most vivid examples of how the oil and gas industry is called upon to adapt to ever-increasing demand for energy resources. This evolution is driving the industry to develop suitable drill string solutions. VAM Drilling is at the forefront of these developments for these types of environments.

The need for such drill pipe is derived from well topology constrains in active regions such as Russia, Eastern Europe, CIS, Alaska and Canadian. The underlying issues are not uniquely related to the service temperature of these tubulars but rather to the high risks associated with susceptible damages during ground transportation and surface handling and especially in "arctic" fields (permafrost).

Controlling critical manufacturing parameters is a key factor to reach top of the range products. Steel microstructure, chemical composition, cleanliness and heat treatment process control are critical to achieve high impact toughness on high strength drill pipe. Controlling yield strength and hardness are instrumental to achieve the established product performance and allowing drilling contractors and operators to safety and efficiently drill in these environments.

The paper presents the appropriate steel chemistries and manufacturing controlled processes required to meet safe operating industry standards and performance-driven drilling practices. This includes a range of parameters to be considered by managers and drilling engineers involved with specifications when planning wells and designing drilling products for low temperature environments.
Cementing Abnormally Over-pressurized Formations in Saudi Arabia
Authors: Al-Dossary Abdulla Faleh , Jennings Scott
Published: October 2012

Cementing is one of important and crucial issues in oil field especially for high pressure and gas bearing formations. It is difficult to achieve a good zonal isolation in such formation types where pressure is abnormal and formation fluid contains corrosive fluids and gases. A common problem associated with highly over pressurized zones is cross flow after cementing. Fluid flow from an over pressured zone to a low pressure, high permeability zone can lead to deteriorating the existing production hardware. Work over operations that attempt to repair cement voids including perforation, squeezing and use of casing patches or scab liners are not recommended as they do not provide long lasting results. In one of onshore fields in Saudi Arabia there is a persistent problem related to cementing at high pressure zones. Recently, communication between A (abnormally over pressurized zone) and B (low pressure zone) formations is occurring due to long term sea water injection with increasing frequency, and has resulted in production interruption in several wells. This paper addresses the problems through investigating field practices including drilling, cementing, and completion. It also reviews the field reports and cased hole logs. A three-month study was conducted to evaluate the effects of formation-A water on cement, where the cement was exposed to formation-A water under down hole conditions. The tests for permeability, mechanical properties TGA and EDXRF are presented, in addition to discussions of some of the preliminary findings.
Injectivity Profile Monitoring and Hot Water Flooding Optimization for Horizontal Well 2G on Rospan's Russkoe Heavy Oil Field using DTS
Authors: Rodionov A. , Lachugin D. , Muslimov E. , Makarov E. , Brown G. A. , Nukhaev M. , Tyutikov S.
Published: October 2012

Rospan International, a subsidiary of TNK-BP, is developing its Russkoe heavy-oil field located in the Yamalo-Nenets Autonomous District of Russia. Development of this field commenced with several pilot pads of horizontal wells completed with stand-alone sand-screens because of the unconsolidated sandstone formation. To increase oil recovery hot water flooding through horizontal injectors was employed, however because of high reservoir heterogeneity the injection profile was not uniform and this led to early water breakthrough and an inefficient waterflood, leaving unswept oil reserves. The remote location and harsh environment limited the use of the conventional production logging tools (PLT) for monitoring the injection profile. Because of this, Rospan International chose to install fiber-optic distributed temperature sensing (DTS) system in a ¼-inch control line attached to a stinger hung below the injection tubing along the reservoir section, post-completion, to determine the injection profile and optimize water flooding.

This paper is describes the completion technology used to install the fiber in the horizontal injector and shows the data and results obtained. Numerical thermal models of the near-wellbore environment were used to analyze the shut-in cool-back and hot water velocity injection DTS data to calculate the injectivity profile. Comparison of the inflow profile calculated from the DTS and PLT data proved the value of the installed optic fiber system for injection change monitoring over time and water flooding optimization for Russkoe oilfield.
The First Implementation of Elongated Proppant for Hydraulic Fracturing in Russia
Authors: Kayumov Rifat , Konchenko Andrey , Nevvonen Olga , Firsov Vladislav , Kuznetsov Maxim , Titov Ivan , Kaluder Zdenko
Published: October 2012

The Volga-Urals basin is one of the largest oil-producing regions in Russia. Orenburg region, located in Volga-Urals, has more than 100 oil fields with great variety of formation properties. The majority of formation fluids are characterized by high gas/oil ratio (GOR) and high bubblepoint pressure. Today, most reservoirs are depleted and produce at bottomhole flowing pressure below bubblepoint pressure. These factors yield multiphase and non-Darcy flow in propped hydraulic fractures, which drastically decreases production. As a result, hydraulic fracturing treatments with conventional proppant are not effective.

Proppant flowback is another critical problem after hydraulic fracturing. There are a few solutions widely accepted by industry, and one of the most popular is a resin-coated proppant (RCP). Usually the coating is activated by temperature; however, for formations with low bottomhole static temperature (BHST), RCP may not be efficient. Many formations in Volga-Urals have a low BHST, which requires a different technology from RCP to eliminate proppant flowback.

A recently developed rod-shaped proppant was proposed as a solution to both problems specified above. In comparison with conventional proppant, it provides higher fracture conductivity with integrated flowback control due to random alignment of proppant grains while packing. This property results in improved fracture cleanup from treating fluids. The rod-shaped proppant also acts to prevent proppant flowback through specific shapes of grains. The significant benefit over conventional RCP is that rod-shaped proppant does not have any BHST limitations, does not require any chemical activation, and does not have special flowback requirements.

Since the introduction of rod-shaped proppant in Russia, 10 fracturing treatments have been successfully carried out with this new proppant in Vakhitovskoe, Lebyzhinskoe, Vostochno-Kapitonovskoe, and Sorochinsko-Nikolskoe oil fields. Well production analysis proved that rod-shaped proppant was more effective than conventional proppant: productivity index is 26 to 67% higher. Further, no proppant flowback issues were detected on wells fractured with rod-shaped proppant. The first successful implementation of this product in Russia is described in detail with laboratory data, a thorough production analysis, and case histories.
Determining Reservoir Connectivity and Compositional Grading by Mapping Asphaltene Gradients
Authors: Tsiklakov A. , Weinheber P. , Wichers W. , Zuo J. , Zimin S. , Driller A. , Oshmarin R.
Published: October 2012

Many techniques are used in industry to determine reservoir hydraulic connectivity from static data. These can be rock-based techniques such as seismic mapping, well to well correlations and geological modeling. Or they can be fluid based techniques such as pressure and fluid gradients. Fluid pressure gradients acquired with formation testers have long been popular but they are understood to be able to identify a lack of connectivity and cannot necessarily prove the presence of connectivity.

Recent work has shown that mapping fluid gradients can be much more definitive. For light fluids this mapping is based on the gas-oil ratio (GOR). For heavier fluids, with little GOR variation, this technique requires mapping a different parameter. It has been suspected that asphaltene content was the parameter to map, but until recently the science of asphaltene prediction was unclear. Recent advances in asphaltene science have now clarified the mechanism for asphaltene distribution in the reservoir and gradient prediction is now possible. And most fortunately it turns out that the asphaltene gradient is relatively easy to measure in-situ.

In this paper we present the science behind asphaltene gradient prediction and show how fluid gradients are a superior way to infer reservoir connectivity. We then present data from an Eastern Siberia oilfield where asphaltene gradients are determined in-situ with a wireline formation tester. These gradients are verified by later comparison to laboratory measurements. Finally and most importantly, we show also how the asphaltene content is used to predict reservoir connectivity both vertically and laterally.
Improved Hydraulic Fracture Modeling Based on Geomechanical Correlation Functions to Optimize Development of Priobskoe Oilfield
Authors: Nadeev A. , Yudin A. , Sudeev I. , Pestrikov A. , Nikitin A. , Sitdikov S. , Timonov A.
Published: October 2012

Conventional low-permeability sandstone formations with strong shale barriers require hydraulic fracturing (HF), a classical approach to fracture geometry optimization, which is needed to enhance oil production of each well and oil recovery from such fields overall. Unfortunately, in most cases there are insufficient resources to acquire the information to create precise fracture modeling for every suggested well. Rock elastic properties and distribution of in-situ stresses have the greatest influence on fracture geometry. HF modeling without proper understanding of these parameters usually results in loss of the relationship between log or core data and zone properties in the model.

A new, innovative approach provides the ability to extract mechanical rock properties for each well from a standard log dataset. This was achieved by introducing correlation functions based on multiple wells with an advanced log dataset including density and acoustic logs and core analysis to correlate dynamic and static rock properties. Correlation functions were built into a Geomechanical (GM) software module referred to here as the GM Module.

The module can be used with any commercial fracture simulator to automate and link the process to log data during each step of the HF modeling and evaluation workflow. Although a majority of studied wells produce from several separately stimulated layers, an adjustment in the GM Module for one HF treatment allows a continuous model of geomechanical properties and stress distribution to be built along the entire logging interval.

As a first step, the module was integrated into a standard modeling workflow for 60 HF treatments; comparative study of the improved versus conventional approach was performed. Second step will be to introduce the GM Module to a stimulation service company operating in Priobskoe oilfield, one of the world's largest oilfields, which will ensure uniform and reliable control over the fracture optimization process to enhance overall field development and oil recovery.
Extensive Optimisation Analyses of the Piping of two large Underground Gas Storage Ariel compressors
Authors: Eijk A. , Heyer D. , Tenbrock A.
Published: October 2012

Two large identical 6-cylinder Ariel JGB/6 reciprocating compressors each of 7.5 MW, are used for an underground gas storage system in (UGS) plant located in Epe, Germany.

The compressors can be operated at a wide range of operating conditions, e.g. variable suction and discharge pressures, 2-stage mode during gas storage, 1-stage mode during gas withdrawal, capacity control by speed variation and valve lifters.

The system should operate efficient, safe and reliable for the complete range of the operating conditions, which can be guaranteed by an extensive optimization analyses during the design stage of the project. For that purpose TNO has carried out different dynamic analyses according the API Standard 618 to be sure that the system can operate efficient, safe and reliable for the long term. In the present paper a summary of the underground gas storage system is given and the different steps in the optimization process of the system have been indicated. Finally, the results of vibration measurements after start-up of the system are presented, conclusions and remarks are given.
Prediction and Dynamic Operation of Gas Distribution Networks
Authors: Ligterink N. E. , van der Linden R. J.
Published: October 2012

In the Netherlands a dense gas distribution network delivers gas to the majority of households. Traditionally only a few big suppliers deliver gas to the network, but currently there is a growing number of new small green gas suppliers in an increasingly flexible and competitive gas transport market. The gas transport providers, responsible for delivering gas to their customers, are confronted with a much more challenging task in operating the network, especially when confronted with fast changes in supply and demand and during maintenance and incidents. This complexity asks for operator support operating the network. In this paper we show, based on physical models of a typical network, involving hundreds of kilometers of pipelines and thousands of nodes and branches, how a fast and versatile simulation model, can predict the pressures and flows in the network. This gas transport simulation: predicting pressures, flows and mixtures at every location in the network, is the basis of controlling a less robust gas network, through periods of high and low demand. We will simulate a real network with the physical relations between flow, pressure, pressure drop, time-delay and mixing. Due to the nonlinear relations between pressure and flow, the standard techniques of dynamical (electrical) network simulation cannot be applied. They lead to instabilities, numerical inaccuracies and slow convergence. We will show how we solved these problems. We further show how this prediction model fits in an operator support environment that helps network operators in real-time management of operations.
Channel Fracturing in the Remote Taylakovskoe Oil Field: Reliable Stimulation Treatments for Significant Production Increase
Authors: Sadykov A. , Yudin A. , Oparin M. , Efremov A. , Doctor S. A. , Vinohodov M. A. , Chebykin N. V. , Garus I. V. , Katrich N. M. , Rudnitsky A. A.
Published: October 2012

The channel fracturing technique changes the concept of proppant fracture conductivity generation by enabling hydrocarbons to flow through open channels instead of through the proppant pack. The new technique is based on four main components: proppant pulsing at surface with fracturing equipment and software, a customized perforation strategy, a fibrous material to deliver stable channels, and a set of models to optimize channel geometry.

The Taylakovskoe oil field is located in western Siberia—430 km away from the nearest settlements. The Jurassic reservoir in Taylakovskoe field is a sandstone formation with significant net pay (average 25 m) and middle-range permeability (3 to 20 mD). Bottomhole temperatures range between 85°C and 90°C. Fracturing gradient is typically 14 kPa/m. The majority of the wells are stimulated immediately after drilling. Sufficient fracture conductivity and effective fracture length are essential for adequate well performance. The optimization of hydraulic fracturing treatments conducted in recent years was based on improved fluid chemistry and pumping "aggressive" fracture designs; this yielded high-quality results. The new channel fracturing stimulation technique, which allows significant increases in fracture conductivity, became the next technological progression. With channels inside the fracture, fluid and polymer residue flow back faster than with a conventional proppant pack, improving cleanup and increasing effective fracture half-length.

One of the most important advantages of the new technology is a very low risk of screenout events. The fibers make fluid more stable, while the presence of clean pulses around proppant structures promotes bridging-free flow. Reduced risk of premature treatment termination is even more important in remote operations such as in the Taylakovskoe field because of the higher costs of nonproductive time and deferred oil production.

Candidate selection criteria were developed specifically for local conditions. Ten channel fracturing treatments performed in Taylakovskoe wells have already showed significant increases in incremental oil production—average 44% beyond expected production as shown by well performance analyses. We describe the performance evaluation of wells completed with this technology and future plans for applying channel fracturing methods in the Taylakovskoe field.
Addressing Wellbore Position Challenges in Ultra-Extended-Reach Drilling in Russia's Far East
Authors: Poedjono Benny , Rawlins Sheldon Andre , Singam Chandrasekhar Kirthi , Van Den Tweel Alexander , Dubinsky Alexey , Rakhmangulov Rustam , Maus Stefan
Published: October 2012

Drilling in Russia's Far East has always been associated with industry-defining ultra-extended-reach drilling. With the emergence of more powerful drilling rigs and advances in measurement- and logging-while-drilling (MWD and LWD) tools, these wellbores can be designed to reach farther. Therefore, accurately penetrating and exploiting distant reservoirs have resulted in critical dependence on high-accuracy surveying techniques.

Successful target penetration and meeting anticollision requirements without the need for shutting production in nearby wells are key proponents for a geomagnetic referencing service (GRS). Geomagnetic referencing is the technique to minimize the lateral position uncertainties when using MWD. This is particularly important for wellbores that extend the boundary of the drilling envelope with stepouts greater than 13 km. The wellbore azimuth accuracy is highly dependent on the quality of the magnetic data used to produce the geomagnetic reference model. This model characterizes the absolute magnitude and vector direction of the natural magnetic field for every point along the wellbore. Representation of the local crustal magnetic contribution is key to the process since it constitutes a significant error in the lateral wellbore position.

Since 2011, a new, highly accurate geomagnetic referencing methodology has been used in Russia's Far East. Global contributions are accounted for by a high-definition geomagnetic model (HDGM). In addition, the local crustal magnetic anomaly is represented by 3D ellipsoidal harmonic functions tracking the shape and depth of the Earth, thereby providing seamless integration with HDGM and avoiding distortions faced by conventional plane-Earth approximations. A comparison with the previous industry standard shows improvements of 0.5° in azimuth determination. This high-degree geomagnetic technique will serve well for a number of upcoming developments in Russia's Far East, continuing to push the drilling envelope and providing essential, accurate wellbore positioning, while offering significant time and cost savings.
Deliverability Modeling of West Siberia Gas-Condensate Wells
Authors: Dobkine S. , Dewenter W. , Yushkov I. , Nesterenko A.
Published: October 2012

Deliverability of low permeability gas-condensate wells decreases when the flowing pressure falls below the saturation pressure. To some extent the deliverability can be mitigated by high matrix gas velocity. Condensate is stripped off next to the well reducing the fluid saturation and improving the well inflow properties. Non-Darcy turbulence flow in turn decreases the well capacity. With well flowing data only, it is difficult to differentiate between the two effects that act in the opposite direction. Gas condensate relative permeability measurements were designed to distinguish between the Velocity Stripping and Non-Darcy flow effects. The experiments were modeled with the Eclipse compositional simulator and the velocity dependent parameters were adjusted to match the experimental data. With the core experiment derived parameters it was possible to uniquely match the well test results of a gas condensate well. The test interpretation is in accordance with the lab results. In the case investigated the Velocity Stripping effect is very significant and fully compensates the adverse Non Darcy flow effect. A sensitivity analysis has shown that both effects are important for an un-fractured well, but insignificant for a fractured well.