bluuebunny/crossref_metadata_2025 huggingface dataset:
Vigilância de Fatores de Risco para Doenças Crônicas por Inquérito Telefônico nas capitais dos 26 estados brasileiros e no Distrito Federal (2006)
Authors: Moura Erly Catarina , Morais Neto Otaliba Libânio de , Malta Deborah Carvalho , Moura Lenildo de , Silva Nilza Nunes da , Bernal Regina , Claro Rafael Moreira , Monteiro Carlos Augusto
Published: May 2008

OBJETIVO: Descrever métodos e resultados iniciais do Sistema de Vigilância de Fatores de Risco e Proteção para Doenças Crônicas não Transmissíveis por Inquérito Telefônico - VIGITEL implantado no Brasil em 2006. MÉTODOS: O VIGITEL estudou amostras probabilísticas da população com 18 ou mais anos de idade residente em domicílios conectados à rede de telefonia fixa de cada uma das capitais dos 26 Estados brasileiros e do Distrito Federal (54.369 indivíduos no total, sendo pelo menos 2.000 por cidade). A amostragem foi realizada a partir de cadastros eletrônicos completos das linhas residenciais fixas de cada cidade, envolvendo sorteio de linhas (domicílios) e sorteio de um morador por linha para ser entrevistado. O questionário aplicado investigou características demográficas e socioeconômicas, padrão de alimentação e de atividade física, consumo de cigarros e de bebidas alcoólicas, e peso e altura recordados, entre outros quesitos. Estimativas sobre a freqüência de fatores de risco selecionados, estratificadas por sexo e acompanhadas de Intervalo de Confiança de 95%, foram calculadas para a população adulta de cada cidade empregando-se fatores de ponderação que igualam a composição sociodemográfica da amostra em cada cidade àquela observada no Censo Demográfico de 2000. Estimativas para o conjunto das cidades empregam fator de ponderação adicional que leva em conta a população de adultos de cada cidade. RESULTADOS: Os cinco fatores de risco selecionados (tabagismo, consumo abusivo de bebidas alcoólicas, excesso de peso, consumo de carnes com excesso de gordura e sedentarismo) tenderam a ser mais freqüentes em homens do que em mulheres. Dentre os fatores de proteção, o consumo regular de frutas e hortaliças foi mais freqüente em mulheres do que em homens, observando-se situação inversa no caso da atividade física de lazer. Diferenças substanciais na freqüência dos fatores de risco e proteção foram observadas entre as cidades, com padrões de distribuição regional diferenciados por fator. DISCUSSÃO: O desempenho do sistema, avaliado a partir da qualidade dos cadastros telefônicos e de taxas de resposta e de recusas, mostrou-se adequado e, de modo geral, superior ao encontrado em sistemas equivalentes existentes em países desenvolvidos. O custo do sistema de R$ 31,15 por entrevista realizada, foi a metade do custo observado no sistema americano de vigilância de fatores de risco para doenças crônicas por inquérito telefônico e um quinto do custo estimado em inquérito domiciliar tradicional realizado recentemente no Brasil.
Aspectos metodológicos de las encuestas de salud por entrevista: aportaciones de la Encuesta de Salud de Barcelona 2006
Authors: Borrell Carme , Rodríguez-Sanz Maica
Published: May 2008

Las encuestas de salud son el procedimiento de elección para obtener información de la población de una determinada zona sobre fenómenos subjetivos relacionados con la salud tales como la existencia de síntomas actuales o pasados, limitaciones o incapacidades generadas por problemas de salud, hábitos personales, exposiciones a situaciones de riesgo. Este artículo tiene por objetivo presentar los pasos seguidos en el diseño de una encuesta de salud y explicar algunos de los instrumentos utilizados en la Encuesta de Barcelona de 2006. Se presentan las novedades de la Encuesta de Salud de Barcelona 2006 relacionadas con: la clase social neomarxista de EO Wright, los trabajos productivo y reproductivo, la inmigración extranjera, la discriminación percibida, la utilización de servicios sanitarios y finalmente, el cuestionario específico para menores.
Epidemiologia e Saúde Coletiva no Brasil: desafios para a formação em pesquisa
Authors: Aquino Estela Maria
Published: May 2008

A pesquisa epidemiológica tem crescido muito no Brasil, o que pode ser atribuído em parte à expansão da formação pós-graduada. Mudanças na avaliação dos programas, conjugando qualidade e eficiência, têm colocado desafios para a formação em pesquisa impulsionando o desenvolvimento de estratégias pedagógicas variadas. Neste artigo, pretendo debater a proposta de "consórcio de pesquisas" do Programa de Pós-Graduação em Epidemiologia da Universidade Federal de Pelotas, destacando algumas implicações pedagógicas deste modelo e apresentando em contraste a estratégia adotada pelo Programa de Pós-Graduação em Saúde Coletiva da Universidade Federal da Bahia para formação em pesquisa epidemiológica. Procuro contextualizar o debate situando-o brevemente no quadro da epidemiologia brasileira, suas principais características de desenvolvimento e pontuando o potencial dos inquéritos domiciliares como ferramenta de diagnóstico de saúde para subsidiar políticas públicas. Após discutir as principais vantagens e limites dos modelos adotados em dois importantes pólos de ensino e pesquisa epidemiológica no país, concluo levantando algumas questões que se colocam como desafios para formação pós-graduada de pesquisadores na atualidade.
Ácaros plumícolas (Acari: Astigmata) em aves do Cerrado do Distrito Federal, Brasil
Authors: Kanegae Mieko Ferreira , Valim Michel , Fonseca Marcelo Andrade da , Marini Miguel Ângelo , Freire Nicolau Maués Serra
Published: May 2008

O objetivo do estudo foi identificar os ácaros plumícolas em aves do cerrado. O mesmo foi realizado na Fazenda Água Limpa (FAL), Distrito Federal, Brasil, entre janeiro e agosto de 2002. As aves foram capturadas com rede de neblina e anilhadas. Foram amostradas 696 aves pertencentes a 83 espécies e 25 famílias de Passeriformes e não-Passeriformes. Foram encontrados ácaros plumícolas pertencentes a cinco famílias: Analgidae, Trouessartiidae, Proctophyllodidae, Avenzoariidae e Psoroptoididae. O presente trabalho contribui com novos registros de ácaros plumícolas nos hospedeiros capturados. A família Proctophyllodidae e o gênero Pterodectes foram os mais prevalentes grupos de ácaros plumícolas coletados. Considerando todas as aves capturadas, a prevalência foi de 44,98%. As maiores prevalências (>50%) de ácaros plumícolas foram encontradas para as famílias Trochilidae, Conopophagidae, Furnariidae, Tityridae, Turdidae, Mimidae, Cardinalidae e Parulidae.
Biologia populacional de Cyphocarax modestus (Osteichthyes, Curimatidae) no córrego Ribeirão Claro, município de Rio Claro (SP)
Authors: Carmassi Alberto Luciano , Silva André Teixeira da , Rondineli Giulianna Rodrigues , Braga Francisco Manoel de Souza
Published: May 2008

Neste trabalho buscou-se um melhor entendimento do ciclo anual de Cyphocarax modestus na área do reservatório de captação de água do córrego Ribeirão Claro. Os parâmetros de crescimento foram estimados através da análise de distribuição de freqüência de comprimento e as relações entre época de menor crescimento, atividade alimentar, acúmulo de gordura e período reprodutivo foram consideradas. Além disso, a taxa instantânea de mortalidade natural foi calculada. Amostragens mensais foram realizadas no córrego Ribeirão Claro, no reservatório de captação de água do município de Rio Claro. Para isso, 50 m de rede de espera foram utilizados, com malhas de 1,5; 2,0; 2,5; 3,0 e 3,5 cm entre nós adjacentes. O método utilizado para a estimativa dos parâmetros de crescimento foi o ELEFAN I e sua aplicação foi feita utilizando-se o programa FISAT, sendo utilizada a versão sazonal da curva de crescimento de von Bertalanffy. Considerou-se que a reprodução de C. modestus é anual e concentrada de dezembro a fevereiro, permitindo assim a identificação de diferentes modas nas distribuições, condição essencial para que esse tipo de análise seja conduzida. Os parâmetros estimados foram: K = 0,34/ano, L¥ = 15,40 cm, C = 0,2, Wp = 0,6 e M = 0,949/ano, com a identificação de quatro coortes. Analisando-se conjuntamente os dados de gordura acumulada na cavidade visceral, índice de repleção estomacal, época reprodutiva e de menor crescimento uma seqüência fisiológica no ciclo anual da espécie pôde ser notada: com o início da maturação das gônadas, os recursos energéticos deixaram de ser investidos no crescimento e passaram a ser utilizados na reprodução.
Borboletas (Lepidoptera: Hesperioidea e Papilionoidea) do campus da Universidade Federal de Santa Maria, Santa Maria, Rio Grande do Sul
Authors: Sackis Gabriel Dorneles , Morais Ana Beatriz Barros de
Published: May 2008

Este trabalho teve por objetivo investigar a composição, riqueza e diversidade das borboletas encontradas na área do campus Camobi da Universidade Federal de Santa Maria - UFSM, Santa Maria, Rio Grande do Sul. As amostragens foram realizadas bimestralmente de setembro de 2005 a setembro de 2006, com esforço amostral padronizado em cerca de sete horas/rede entomológica/ocasião. No total de 113 horas de amostragem, foram registrados 872 indivíduos, distribuídos em 89 espécies. Do total de indivíduos, 575 (65,9%) pertencem à família Nymphalidae, 174 (19,9%) a Hesperiidae, 88 (10,1%) Pieridae, 21 (2,4%) Lycaenidae, 10 (1,2%) Papilionidae e quatro (0,5%) Riodinidae. Do total de espécies, 40 (44,9%) pertencem à família Nymphalidae, 25 (28,1%) à Hesperiidae, 11 (12,4%) Pieridae, oito (8,9%) Lycaenidae, três (3,4%) Papilionidae e duas (2,3%) Riodinidae. As cinco espécies mais abundantes do campus Camobi foram Pyrgus orcus (Stoll, 1780) (N = 78) (Hesperiidae) e os Nymphalidae Hermeuptychia hermes (Fabricius, 1775) (N = 70), Anartia amathea roeselia (Eschscholtz, 1821) (N = 55), Vanessa braziliensis (Moore, 1883) (N = 51) e Heliconius erato phyllis (Fabricius, 1775) (N = 51). Destas, apenas H. hermes e V. braziliensis, consideradas comuns em campos ou ambientes abertos, não são características de ambientes perturbados. Estudos anteriores registraram mais 12 espécies de borboletas, elevando a riqueza local de espécies para 101. Apesar de estar sujeito a forte ação antrópica, o campus Camobi ainda é capaz de abrigar uma fauna expressiva de borboletas.
The parakeet Brotogeris tirica feeds on and disperses the fruits of the palm Syagrus romanzoffiana in Southeastern Brazil
Authors: Sazima Ivan
Published: May 2008

Small psittacids remain unrecorded as dispersal agents of palm fruits in Brazil. I record here the plain parakeet (Brotogeris tirica), an Atlantic forest endemic, feeding on and dispersing the fruits of the palm Syagrus romanzoffiana at Ubatuba, northern coast of São Paulo, Southeastern Brazil. The birds removed the fruit and carried it away from the mother-tree in about 40% of the feeding records. While perched on trees and shrubs of the understorey, the parakeets removed and ingested most of the mesocarp, dropping the partly consumed fruit. As the parakeets damaged no the embryo and may feed at a distance from the mother-tree, they act as primary dispersal agents. This is the first substantiated record of a small Neotropical psittacid as a stomatochorous dispersal agent of palm fruits the size of A. romanzoffiana drupes.
Evaluation of thin‐film photodevices and application to an artificial retina
Authors: Kimura Mutsumi , Shima Takehiro , Yamashita Takehiko , Nishizaki Yoshitaka , Hara Hiroyuki , Inoue Satoshi
Published: May 2008

Abstract— First, conventional poly‐Si thin‐film photodevices, p‐i‐n thin‐film photodiodes (TFPDs) and p‐n TFPDs, were evaluated. It was found that the photo‐induced current (Iphoto) is not simultaneously relatively high and independent of the applied voltage (Vapply). Next, a novel poly‐Si thin‐film photodevice, p‐i‐n thin‐film phototransistor (TFPT), is proposed. It is found that the Iphoto is simultaneously relatively high and independent of the Vapply because the depletion layer is formed in the entire intrinsic region and the electric field is always high. These characteristics are preferable for photosensor applications. Finally, the p‐i‐n TFPT was applied to an artificial retina. The photo‐illuminance profile is correctly detected and the output voltage profile is correspondingly outputted. This artificial retina is expected to be suitable for human beings because it can potentially be fabricated on a flexible, harmless, plastic, and organic substrate.
Bistable SmA liquid‐crystal display driven by a two‐direction electric field
Authors: Chen Hui‐Yu , Shao Renfan , Korblova Eva , Walba David , Clark Noel A. , Lee Wei
Published: May 2008

Abstract— A new operation mode of a bistable smectic A (SmA) display using two sets of electrodes, one without specific features to induce homeotropic orientation of the director and the other with an in‐plane pattern to induce planar orientation of the director, has been demonstrated. Both statements of the director orientation are the stable states of SmA liquid crystals. Compared with the electrical addressing mode of a conventional SmA display, the SmA display mode presented in this study exhibits a high contrast ratio, excellent bistability, and reasonably fast switching under the employment of two crossed polarizers. Moreover, gray level can be achieved by regulating the frequency, owing to the formation of the focal‐conic defect. This operation mode of a bistable SmA device demonstrated great potential for the further application in flexible displays.
Energy‐recycling high‐contrast organic light‐emitting devices
Authors: Yang Chih‐Jen , Cho Ting‐Yi , Lin Chun‐Liang , Wu Chung‐Chih
Published: May 2008

Abstract— It is reported that by integrating OLEDs with solar cells, ambient‐light reflection as low as 1.4% (even superior to that achieved with polarizers) can be achieved without compromising the EL efficiency for high‐contrast display applications. Furthermore, in such a configuration, the photon energies of both the incident ambient light and the portion of OLED emission not getting outside of the device can be recycled into useful electrical power via the photovoltaic action, instead of being wasted as in other reported contrast‐enhancement techniques. These features, we believe, shall make this present technique attractive for high‐contrast display applications and portable/mobile electronics that are highly power‐aware.
Assessment of an MASW Approach Incorporating Discrete Particle Modeling
Authors: Donohue Shane , Long Michael
Published: May 2008

A Discrete Particle Scheme (DPS) consisting of interacting circular particles is utilized to examine a popular Multichannel Analysis of Surface Waves (MASW) approach. Synthetic earth models of various complexity are generated using the DPS and analyzed by selected MASW dispersion and inversion techniques. For simple two layer and multilayer models where velocity increases with depth, inversion using the dominant fundamental mode results in MASW profiles of shear wave velocity [Formula: see text] that closely match the true synthetic [Formula: see text] profiles. Inversion using the default parameters produces gradational increases in velocity, rather than true discontinuities. When tested on a multilayer model containing a low velocity layer (LVL), inversion using a fundamental mode assumption results in a moderate increase in error. MASW field tests at a highly uniform site in Norway (Onsøy) and a site with distinctive layer boundaries in Ireland (Ballinasloe) result in highly repeatable profiles of [Formula: see text]. Resolution of dispersion curves at low frequencies [Formula: see text] is a problem at the Ballinasloe test site, which limits the depth of penetration of the technique. MASW inversion results compare excellently with downhole seismic cone tests at the Onsøy test site and reasonably with a seismic refraction survey at the Ballinasloe site.
Mapping of Average Shear Wave Velocity for Bangalore Region: A Case Study
Authors: Anbazhagan Panjamani , Sitharam Thallak G.
Published: May 2008

Mapping the shear wave velocity profile is an important part in seismic hazard and microzonation studies. The shear wave velocity of soil in the city of Bangalore was mapped using the Multichannel Analysis of Surface Wave (MASW) technique. An empirical relationship was found between the Standard Penetration Test (SPT) corrected N value [Formula: see text] and measured shear wave velocity [Formula: see text]. The survey points were selected in such a way that the results represent the entire Bangalore region, covering an area of [Formula: see text]. Fifty-eight 1-D and 20 2-D MASW surveys were performed and their velocity profiles determined. The average shear wave velocity of Bangalore soils was evaluated for depths of [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text]. The sub-soil classification was made for seismic local site effect evaluation based on average shear wave velocity of [Formula: see text] depth [Formula: see text] of sites using the National Earthquake Hazards Reduction Program (NEHRP) and International Building Code (IBC) classification. Mapping clearly indicates that the depth of soil obtained from MASW closely matches with the soil layers identified in SPT bore holes. Estimation of local site effects for an earthquake requires knowledge of the dynamic properties of soil, which is usually expressed in terms of shear wave velocity. Hence, to make use of abundant SPT data available on many geotechnical projects in Bangalore, an attempt was made to develop a relationship between Vs (m∕s) and [Formula: see text]. The measured shear wave velocity at 38 locations close to SPT boreholes was used to generate the correlation between the corrected N values and shear wave velocity. A power fit model correlation was developed with a regression coefficient [Formula: see text] of 0.84. This relationship between shear wave velocity and corrected SPT N values correlates well with the Japan Road Association equations.
Image Reconstruction in Seismic and Medical Tomography
Authors: Kanlı Ali Ismet
Published: May 2008

Tomography has been used for more than [Formula: see text] in medical science and its success is well known. One of the most important reasons for the success of medical tomography compared to seismic tomography is the data-acquisition geometry. A data-acquisition geometry similar to the one used in medical tomography was designed and tested with synthetic geological models. Geophysical-type data-acquisition geometries were also applied to the geological models, and the resulting images were compared to the medical images. The reconstructed image obtained in the medical case resembled the synthetic geological model and had higher resolution than the geophysical image. Secondary attention is drawn to the determination of the differences between the low- and high-velocity zones in the final image reconstruction of the tomographic inversion process. Therefore, the step-like high- and low-velocity embedded layer models were tested with different spreading systems. The geological models were also tested with one-dimensional (1-D) initial velocity models to understand the effect of the initial velocity model on the final image reconstruction. In the high-velocity layer case, the tomographic process is quite successful in image reconstruction, but cannot achieve the same success in the low-velocity layer case.
Practical 3-D Migration and Visualization for Accurate Imaging of Complex Geometries with GPR
Authors: Radzevicius Stanley
Published: May 2008

Obtaining high-quality three-dimensional images that accurately represent target geometries is crucial for reliable interpretation of ground penetrating radar data. Dense data acquisition, three-dimensional migration processing, and visualization are needed to recognize complex target geometries. A novel implementation of the diffraction summation migration algorithm efficiently images three-dimensional geometries by utilizing the efficient properties of fast Fourier transforms to compute diffraction summations. The algorithm decomposes the diffraction summation calculations into spatial and temporal summations. The spatial summations are computed by convolving the data with two-dimensional convolution kernels computed from the three-dimensional point spread functions. Computation times are reduced by performing convolutions in the wavenumber domain using two-dimensional fast Fourier transforms. The migration aperture is easily adjusted in the algorithm to increase computational speeds and reduce processing artifacts associated with large amplitude spikes. Microsoft Visual Studio.NET and C# are used to create efficient and low-cost applications optimally designed for the processing and display of ground penetrating radar data. Migration algorithms are combined with volume rendering and visualization algorithms that utilize DirectX to visually recognize complex geometries in three-dimensions. A gravel test bed containing buried spheres, letters cut from metal sheets, pipes, and drums is imaged with dense and orthogonal 400 and [Formula: see text] ground penetrating radar surveys. A linear array composed of fourteen variably spaced spheres is used to empirically determine the resolution capabilities of commercial ground penetrating radar systems in favorable soils. In addition, letters cut from aluminum sheets are used to test imaging capabilities similar to those used to test human vision. Observed quarter-wavelength spatial resolutions are consistent with theoretical predictions. While horizontal slices work well for displaying horizontal objects, volume rendering is more effective for visualizing dipping objects. Increasing antenna frequency improves spatial resolution and produces less pronounced polarization differences between data acquired with orthogonal surveys.
Scaling Mitigation and Strategy for First Full Field Steam Injection X Field Oman: History Matching and Modelling
Authors: Nengkoda Ardian , John Walsh , Ahmed Dilshad , Busaidy Ali , Shuely Nasser , Sariry Sameer , Putra Pristiwanto
Published: May 2008

The X Field steam-injection project is the world's first full-field steam-injection project based on thermally assisted gas/oil gravity drainage (TAGOGD) in a fractured carbonate field. The project scope includes drilling some wells and installing facilities to treat water and generate around 18,000 tonnes per day of steam. Additional facilities will be built to process the incremental oil and gas produced at the field as well as disposing of excess produced water in deep reservoirs. The EOR recovery process being applied TAGOGD is based on injecting steam into the formation's fractures to heat the low-permeability oil-bearing rock. This feature of the project allows the number of wells, and hence development costs, to be kept to a minimum. In other hand, the flow assurance issue across the facilities will be challenging, and managing scaling issues and inhibition require a host of solutions especially on the economics of scale management. A history of scaling as a lesson learnt had been gathered during Pilot steam back to a couple years ago and current cold production experiences is captured. At the moment, the incompatibility of various water stream indicated scaling deposition are majority dominated by carbonate and less sulphate. The strategy of integrated mitigation for all possible scaling for the next facilities scenario whether from water treatment and oil production facilities have been implemented and assessed during engineering design, while the type of inhibitor have been identified base on dynamic tube blocking tests and the potential risk have been registered. In the end, win-win economics approach is modeled base on water and fluid composition, various pressure and temperature.
Innovative Use of Kaolinite in Downhole Scale Management: Squeeze Life Enhancement and Water Shutoff
Authors: Fleming Niall , Ramstad Kari , Mathisen Anne-Mette , Nelson Alex , Kidd Sam
Published: May 2008

Applied research has been undertaken to examine the potential of kaolinite combined with a kaolinite fixation agent to; Increase squeeze lifetime through alteration of near wellbore surface characteristics and mineralogy and,Provide water shut off control.

With respect to enhancing squeeze lifetime, it is documented that kaolinite increases the quantity of inhibitor adsorbed. Conversely, clean sandstone with low clay content commonly provides a poor substrate for adsorption. Furthermore, in reservoirs that experience near wellbore formation damage due to kaolinite mobilisation, it has been shown that use of a fixation agent as part of a squeeze treatment can increase squeeze lifetime. Using these facts, research has assessed the feasibility of injecting microcrystalline kaolinite (average particle size 2 μm) combined with the fixation agent and scale inhibitor as a means of mechanically altering near wellbore mineralogy and surface property characteristics within clean, high permeability sandstones. The testing has been designed to mimic the squeeze procedure used in the field for performing such a job and involves no additional steps to that used in a normal squeeze, i.e. Pre-Flush → Main Treatment → Over-Flush. The paper presents the results of coreflood experiments that have been undertaken to demonstrate "proof of concept" for the above along with examples of potential field applications.

A further concept, born from the initial idea, was the use of kaolinite and fixation agent for efficient, low cost, environmentally friendly water shutoff. There are several available products for water shutoff but the disadvantage of these is that they are not acceptable for use in Norway due to poor environmental characteristics. Hence, there was a need to fill this gap by developing water shutoff technology to meet country specific environmental legislation. The paper provides details of coreflood testing, where an excess of kaolinite has been used to form an internal and external filter cake that is attached to the wellbore face and within the near wellbore using the fixation agent.

The paper draws on data from StatoilHydro operated fields in order to highlight the potential of this innovative approach to downhole scale management and water control.
Impact of Successive Squeezes on Treatment Lifetime and Well Productivity: Laboratory and Field Evidence
Authors: Fleming Niall , Ramstad Kari , Nelson Alex , Graham Gordon
Published: May 2008

Over the lifetime of a well it is possible that several squeeze operations will be performed depending on scaling severity. Downhole squeeze operations have been performed for many years and have on the whole been an effective scale management tool. However, the long term impact that successive squeezing has on treatment lifetime and well productivity has received little attention. This paper will address these issues by comparing the results from a unique sequence of long term corefloods that were designed to replicate five successive treatments on the kaolinite rich, Middle Tarbert core from the StatoilHydro operated field, Oseberg Sør. Relatively few squeeze treatments have been performed on this field, and the coreflood results have been up-scaled to provide a potential prediction of the effects of long term squeezing and well productivity on Oseberg Sør. Furthermore, the laboratory results have been cross-checked by comparing with the Heidrun field that has been squeezed for many years. Heidrun is an analog of Oseberg Sør with kaolinite rich producing intervals and similar productivity issues related to kaolinite mobilisation.
Managing Radioactive Scale: Strategic Approach and Success Story
Authors: Ghosh B. , Al-Bemani Ali. S. , Najim Kitany , Al-Hajri Said , Clark James , Boukadi F. H.
Published: May 2008

Radioactive material contaminated, hard crystalline scale deposition on ESP & downhole equipment was resulting in frequent breaking of ESP shaft in a multilateral openhole producer. Extremely high workover cost in frequent replacement of downhole equipment and associated radioactive hazards, necessecitated a strategic MDT approach. Software usage and extensive laboratory backup helped finding the best possible option to mitigate this problem. Three possible well treatment options were investigated. Scale inhibitor squeeze option was studied through reservoir condition core flow and rejected because of probable formation impairment and placement difficulties in a complex well and reservoir geometry. Periodic soaking of ESP with scale dissolver was considered a viable option because of economics and operational ease. Laboratory studies were conducted to design the placement strategy. We developed a xanthan based high viscous self degrading polymer gel coushion which would support the scale inhibitor solution around the ESP for the necessary soaking period to prohibit flow into the pressure depleted formation. However this concept had to be abandoned because of flipping over of the fluids in laboratory observation and uncertainty of optimum soaking period downhole. The last and final option was to wait for the running ESP to fail and during workover the well could be completed with a macroni line for continuous injection of scale inhibitor. Judicial selection and optimization of inhibitor, continious monitoring of well treatment and well behavior has resulted in phenomenal success which is demonstrated by the fact that the ESP run life has been exceeded 700+ days against <100 days average runlife prior to treatment. The treatment also took care of radiation hazard and contaminated equipment disposal problem to a large extent.
Deployment of Real-Time Scale Deposition Monitoring Equipment to Optimize Chemical Treatment for Scale Control During Stimulation Flowback
Authors: Emmons D. , Smith S. A. , Weathers T. , Jordan M. M. , Feasey N. D.
Published: May 2008

A series of three fixed platforms off the California coast produce fluids sourced from sandstone and carbonate formations that individually produce brines with substantial amounts of calcium and bicarbonate, respectively. These fluids are sent to a central facility onshore for processing, requiring that the combined fluids be treated for calcium carbonate scale. During acid stimulation treatments of wells, the fluid flowback from the wells initially has very high calcium levels that greatly increase risk of scale formation for a short period of time. To better understand the dynamic scale risk created during stimulation flowback, a monitoring program using a novel in-line deposition monitoring probe was implemented. The probe was placed in-line at the onshore processing facility to track changes in the production fluids prior to and during the acid stimulation program. The resulting data was correlated to several events that occurred within the process including a process shut-in, deposition of heavy oil residue that fouled the probe during a period of poor separation, and scale deposition upon reduced chemical treatment.

Real-time data obtained during flowback from two acid stimulation jobs is presented, demonstrating how it was possible to optimize the scale inhibitor treatment program such that no scale deposition occurred during these treatments. The value of the real-time monitoring data versus other methods of assessing the risk of scale formation within these fluids is highlighted and the ability to optimize inhibitor treatment rates in real-time demonstrated.

The development and implementation of on-line real-time monitoring for deposition control of an active and changing scaling environment shows the clear value that this technology brings to scale control within process facilities.
Study of BaSO4 Formation Kinetics and Inhibition Effect of Polyphosphino-Carboxylic Acid (PPCA) With Synchrotron X-Ray Diffraction (SXRD)
Authors: Mavredaki Eleftheria , Neville Anne , Sorbie Ken S.
Published: May 2008

Precipitation of barium sulphate from aqueous supersaturated solutions is one of the most well known problems in the oil industry. Precipitation of barite and other insoluble scale types (metal sulphates, calcium carbonate and silicates) propagate to undesirable formations, which adhere strongly in production tubing and in equipment parts. Formation of BaSO4 lead to a decrease in the performance of the petroleum facilities and to inevitable damage in the oil industry.

Barium sulphate is one of the most insoluble types of inorganic scale. It resists many chemical methods of removal. Inhibition of barium sulphate by chemicals is generally recognized as the most appropriate approach for flow assurance.

In this study Synchrotron X-Ray Diffraction was used to investigate the kinetics of barium sulphate formed on stainless steel surface at two different temperatures. For the first time SXRD measurements of BaSO4 formed in the presence of foreign ions (Sr2+, Ca2+ etc) are presented. The in-situ measurements allowed the assessment of the crystallographic nature of the formed scale and the probation into the precipitation mechanisms. Additionally this study focused on the effect of PPCA on the barium sulphate precipitation. PPCA was examined for its inhibition action in two concentrations at both temperatures. The formed barite crystal faces after the treatment with PPCA were recorded.
Control of Silicate Scales in Steam Flood Operations
Authors: Gallup Darrell L. , Hinrichsen Charles J.
Published: May 2008

Water circulating during steam flooding to recover additional oil from reservoirs often becomes enriched in dissolved silica. As the silica concentration increases in the water, silicate minerals become supersaturated. At supersaturation conditions, amorphous silica and metal silicates may deposit in heat exchangers. Scale deposits not only reduce heat exchange efficiency due to fouling, but they may plug tubes resulting in tube failure. Control of these deposits in boilers and co-generation equipment is necessary to reduce down-time for mechanical cleanout.

In the present study at a steam flooded field, steam boiler and co-generation tube deposits consisted of opal-A, pectolite, aegerine, clinamphibole, serpentine-like minerals, iron oxide corrosion products, and apatite. Iron in the silicate minerals appears to derive from transporting incompletely oxygen scavenged circulating water to the boilers and co-generation unit in carbon steel pipe. Increasing the concentration of oxygen scavenger and EDTA-based scale inhibitor in the feed water has significantly reduced scale deposition.

Other methods that may be used to control silica/silicate scaling in steam flood operations include: (a) dilution with fresh water, (b) reducing the pH of the water, (c) treating the water with reducing, complexing and sequestering agents, (d) removing silica from water by lime softening, (e) precipitation of silica in water with metals or cationic surfactants, and (f) treating the water with geothermal silica scale inhibitors/dispersants.
Kinetics of CaCO3 Scale Formation During Core Flooding
Authors: Larsen Tore , Randhol Preben , Lioliou Marianna , Jøsang Leif Olav , Østvold Terje
Published: May 2008

Many oil fields in operation today have major scale control problems, and new insight and know-how in this area are important in order to maximize production at minimal operational costs. The models on mineral precipitation available today are based mainly on thermodynamic data found in the literature. The impact of scale precipitation on well performance, however, is not being accurately modeled due to lack of data on precipitation kinetics. It is therefore important to gain a proper understanding of the kinetics of scale formation and its detrimental effects on porosity and permeability in the near well bore region. A series of core flooding experiments were conducted at 80°C to investigate CaCO3 scale formation. This paper focuses mainly on the CaCO3 precipitation kinetics data obtained at various flow rates, supersaturation ratios (SR) and substrates. However, permeability and porosity alteration due to precipitation during flow are also presented and discussed. Kinetic data were derived from both continuous pH measurements and determination of the remaining calcium concentration in the effluent. The precipitation rate was very dependent on the amount of CaCO3 already precipitated. The combination of residence time and duration of the experiment determined the effluent SR. After a steady state precipitation rate was reached in a Lochaline sandstone, the SR of the effluent changed from the initial 3.00 to ~1.55 and ~1.15 for core residence times of 1 and 4.5 minutes, respectively. With initial SR = 2.00 the corresponding SRs were ~1.25 and ~1.13 for residence times of 1 and 4 minutes, respectively. A permeability-porosity profile was determined showing that the permeability changed rapidly early in the experiment and was followed by a long period with relatively little change as a function of porosity decrease. Towards the end of the experiment a dramatic decrease in permeability, typical to tube blocking test behavior, was observed. Visualization experiments using two dimensional glass porous medium models showed that when crystals had been formed by nucleation, further precipitation occurred preferably on existing crystals.
Development of a Viscosified Scale Inhibitor for Improving Placement in Acid Fractured Limestone Reservoirs
Authors: Heath S. M. , Sim Michael , Archibald Marc , Stalker Robert
Published: May 2008

Scale is a major problem for the oil and gas industry and is often controlled by the use of downhole scale inhibitor squeeze treatments. The placement of scale inhibitor in acid fractured limestone reservoirs presents a particular challenge and effective placement of scale inhibitor cannot be guaranteed when performing conventional low rate (<10bpm) bullhead squeeze treatments. In order to ensure the fluid package is placed over the whole of fractured interval it is necessary to perform high rate scale squeezes (40-60bpm) in conjunction with mechanical divertors. However, these treatments are expensive and limit the amount to treatments that can be performed per day in a scale squeeze campaign.

This paper describes the development of a range of viscosified polymeric scale inhibitors for squeeze application in acid fractured wells. A particular feature of these products is their viscous self diverting nature which means they can be used at low pump rates at rates of <10bpm. This method also precludes the use of mechanical divertors and enables cross flow problems to be overcome and effective chemical placement over the whole of fractured interval. In addition, this offers the benefit of improved scale control and squeeze lifetimes coupled to considerable economic savings by being able to perform more treatments per day using conventional pumping equipment.

A detailed investigation into the rheological properties of selected products has been performed to design the optimal delivery system. Experimental data on the compatibility of a variety of viscosifying agents and chemical breakers different types of polymeric scale inhibitors will be presented. This will include viscosity profiles, shear thinning behavior and breaking times for these systems. Inhibitor performance and core flood studies to evaluate formation damage potential and retention and release characteristics will be also be presented. In addition, the paper will add the results of a computer modelling study to validate the experimental data and aid the placement strategy for optimum field application.
Mechanistic Study of Chemicals Providing Improved Halite Inhibition
Authors: Guan Hua , Keatch Richard , Benson Charles , Grainger Neil , Morris Liz
Published: May 2008

This paper investigates the application of halite inhibitors and the mechanisms associated with salt formation and inhibition. Several new chemistries (two inorganic compounds and one organic nitrogen-based product) have been identified which provide improved halite inhibition. Their inhibition performance was studied and compared with commercially available inhibitors.

Salt deposition in high salinity brines can cause blockages to production and process systems requiring remedial action, often on short notice. Current commercial halite inhibitors are only effective at high concentrations (250 – 5,000 ppm). Therefore, a more efficient salt inhibitor would need to reduce both treatment level and production downtime.

The inhibition performance of three new chemicals and two commercial products were evaluated under static conditions along with performance assessment after aging. Both sea salt and pharmaceutical-grade sodium chloride were used in the tests. All three new chemicals showed improved inhibition efficiency over the two commercially available products. The retention property for one of the three new chemicals was evaluated using two different core materials. The test results showed a satisfactory amount of adsorption under favourable pH conditions. Core floods using field core materials were conducted to evaluate the chemical squeeze packages. No formation damage was observed, both oil and brine permeabilities have recovered following the chemical treatments.

A lower dosage (10–50 ppm) was required for the new chemical as compared with conventional treatment levels. The lower treatment level provides the potential to reduce cost, treatment intervals and production downtime. Moreover, there is the opportunity for the new product to be batch squeezed into the reservoir, providing prolonged protection against salt deposition.
A New Chemical Treatment to Inhibit Iron Sulfide Deposition
Authors: Lehmann Marc , Firouzkouhi Fafa
Published: May 2008

This report documents laboratory studies that display the potential of the new iron sulfide treatment that, instead of preventing the formation of the scale, allows a dispersed iron sulfide to form that is both water wet and deactivated. Evidence has been provided that shows how the treatment keeps the particle size small so that is unlikely to associate and deposit in production systems. The mechanism of control is and the parameters that control the performance are discussed. The dispersant facilitates the transport of the scale with the produced water but prevents the FeS from forming pads at water-oil interfaces. Results from a limited field trial demonstrate the success of the treatment in the preventing the formation of pads in a primary separator, and solids deposition in a heater treater.
Two Year Results of a Breakthrough Physical Water Treating System for the Control of Scale in Oilfield Applications
Authors: Rzeznik Lawrence , Juenke Michael , Stefanini Daniel , Clark Martin , Lauretti Paolo
Published: May 2008

The presence of scale in a well is arguably one of the most difficult and expensive problems facing the production function of the oil industry today and despite many years of concentrated effort to effectively combat it, the problem still exists in a widespread manner. Much of the effort to mitigate the scale problem and render it less of a threat to production has been centered on methods of inhibiting its formation with chemicals or by mechanically removing it, but in many cases the action taken has not met the overall effectiveness sought by industry. A new approach to the problem is indicated but what form might it take? If a method were to exist that would prevent the deposition of scale rather than treating it when it appears, then this would represent a quantum leap forward in production operations.

This paper presents a unique and non-chemical method for the control of oilfield scales using a physical water treating device that was originally developed for industrial water treatment. This patented technology presents an alternative for oilfield scale treatment and control when it is installed at the surface of the well. It functions by inducing a randomly pulsed high frequency signal into the piping system which causes the scale crystals to form in the produced fluid rather than on the walls or surfaces of down hole and topside equipment. Prior to field testing this mechanism was evaluated under laboratory conditions using a dynamic tube-blocking test with concentrated brines that produced calcium carbonate, barium sulfate and combinations thereof. Subsequent field studies encompassed the treatment of oil and gas wells with various forms of lift in four different regions in North America with over ten different companies. The system was designed to overcome the wide range of variables that exists from well to well and specific results from several wells will be reviewed to illustrate the value that this approach is bringing to well management.

The conclusion to be drawn from this work is that physical water treating technology can be effective in controlling oilfield scale deposition and there are many benefits to be enjoyed by an operator including increased production, significant cost savings and a positive impact on the environment. It is these benefits that make continued work in this field of science a worthy endeavor to pursue for the oil industry.
Performance of Scale Inhibitors Under Carbonate and Sulfide Scaling Conditions
Authors: Smith J. Kevyn , Hammons Julie , Boyd Galyn , Fu Qiang
Published: May 2008

This paper compares the scale inhibition efficiencies of a phosphate ester, two phosphonate and two polymer chemistries in the presence of ferrous iron, calcium carbonate, barium sulfate, iron sulfide and iron carbonate scales, as well as combinations therein. The results show that as the scale speciation of the precipitating solids change so does the scale inhibition efficiency. These changes in efficiency were attributed to the cumulative effects of crystal matrix distortion by either exogenuous scale specie or effect of metal complexation to the scale inhibitor chemistry. The ultimate conclusion of this study is that because of the relationship between the scale inhibitor performance and ferrous iron concentration, it is important to consider this relationship when determining the minimum inhibitor concentration (M.I.C.) for the inhibition of scale growth in oilfield production systems.
Scale Challenges in Talisman's Varg Field
Authors: Sorhaug E. , Graham G. M. , Stalker R. , Littlehales I. J. , Kidd S. L.
Published: May 2008

The Varg field (PL038, Block 15/12) is located in the Norwegian Sea. The Varg reservoir is Oxfordian sandstone of Jurassic age, with an upper (1000-2000 mD) and lower (100-200 mD) sand separated by a mud rich sandstone. The field is highly compartmentalized and is located around a salt dome, and contains a number of different formation waters ranging from high salinity, higher barium (up to 280 mg/l) in the West and lower salinity and lower barium (30 mg/l) in other areas. All waters contain naturally occurring dissolved iron at concentrations up to 175 mg/l. Following scaling in several wells, a chemical re-selection and treatment optimisation programme was initiated. Extensive laboratory studies were undertaken to select optimum inhibitors, which was further complicated by environmental requirements. The presence of dissolved iron was shown to have an adverse effect on the incumbent scale inhibitor, leading to the selection of a number of alternative products. Given the highly compartmentalized nature of the reservoir and the large permeability contrast between zones, near wellbore modelling studies, examining chemical placement using both conventional (aqueous) based treatments and also viscosified treatments, were conducted. The potential for poor placement and subsequent poor lifetimes led to further detailed simulation work using up to date PLT logs to further refine the treatments in subsequent wells. Therefore, this paper describes the various challenges facing scale control in the Varg field. The paper presents results from a chemical re-selection exercise showing the controlling influence of dissolved iron, together with coreflood studies used to select the most effective non-damaging product for subsequent field trials. Extensive near wellbore modelling results are presented to illustrate the challenges faced with respect to effective chemical placement, which highlight the challenges faced. Several field trials have now been conducted with a new chemical and the results of these are also discussed.