bluuebunny/crossref_metadata_2025 huggingface dataset:
Análise da equação de Swamee-Jain para cálculo do fator de atrito
Authors: Andrade Leandro , Carvalho Jacinto de A.
Published: April 2006

Objetivou-se, com este trabalho, estudar o comportamento da equação de Swamee-Jain nas mais variadas situações de condução de água em sistemas pressurizados, para isto se desenvolveu um aplicativo computacional para realizar simulações variando o diâmetro interno do tubo, a velocidade de escoamento e a rugosidade absoluta das paredes da tubulação. A base de comparação do estudo se compunha das equações mais empregadas no cálculo do fator de atrito da equação universal de Darcy-Weissbach, respeitando-se seus respectivos regimes de escoamento e limitações. A partir de então, concluiu-se que, para o regime turbulento em conduto liso, a equação de Swamee-Jain apresentou diferenças de valores de f em relação às equações específicas requerendo, para melhor precisão, um fator de correção. Para os outros tipos de escoamento a concordância foi considerada satisfatória.
Análise cefalométrica comparativa das alturas faciais, anterior e posterior, em jovens brasileiros, descendentes de xantodermas e leucodermas, com oclusão normal
Authors: Takahashi Ricardo , Pinzan Arnaldo , Henriques José Fernando Castanha , Freitas Marcos Roberto de , Janson Guilherme dos Reis Pereira , Almeida Renato Rodrigues de
Published: April 2006

OBJETIVOS: avaliou-se cefalometricamente as estruturas esqueléticas da face no sentido crânio-caudal (vertical) para: obter os valores médios de normalidade de jovens brasileiros, descendentes de xantodermas e leucodermas, com oclusão normal; verificar a presença ou ausência de dimorfismo entre os gêneros e investigar a existência de diferenças ou semelhanças entre os grupos raciais estudados. METODOLOGIA: estudo cefalométrico. RESULTADOS: após a obtenção da média e do desvio padrão de cada medida cefalométrica estudada, para ambos os gêneros e grupos raciais, os resultados sinalizaram, em algumas das grandezas cefalométricas, a presença de dimorfismo entre os gêneros para ambos os grupos raciais e diferenças entre os grupos raciais. CONCLUSÕES: verificou-se a necessidade de se utilizar um padrão cefalométrico específico, no sentido crânio-caudal (vertical), para os brasileiros, descendentes de xantodermas e leucodermas.
Evolución de la endemia de la lepra en Brasil
Authors: Magalhães Maria da Conceição Cavalcanti , Iñiguez Rojas Luisa
Published: April 2006

La presente investigación se propone abordar la distribución territorial de la lepra en Brasil con el objetivo de identificar las regularidades de su diferenciación espacial y aportar conocimientos que permitan progresar en la comprensión de los procesos de su producción social. Fueron calculadas las tasas anuales de detección de casos, brutos y específicos, para las regiones y estados del país. La evolución espacio-temporal fue realizada mediante la construcción de series históricas. Se expone como substrato de los análisis una síntese sobre la distribución histórico-geográfica de la endemia en Brasil. La serie histórica del período 1960 - 2002, permite comparar las tasas de detección de las regiones, en la primera década, con las tasas más bajas, a excepción de la región Norte, que se destaca com la mayor detección. Todas las regiones elevan la detección a partir de la década del 70, siendo la Sul la de detección más baja. Las regiones Norte y Centro Oeste, mantienen las más altas detecciones de casos y los mayores incrementos, lo cual evidencia la desigual evolución regional de la endemia en el país. La permanencia histórica de elevada incidencia de la lepra en la región Norte, en el estado de Maranhão y Pernambuco en la región Nordeste, del estado de Paraná en la región Sul, así como relativamente bajas incidencias en el resto de esta última región, sugieren la existencia de contextos geográficos de diferente vulnerabilidad a la producción social de la lepra, y de nuevos componentes en la organización espacial en algunos territorios.
Qualidade parasitológica e condições higiênico-sanitárias de hortaliças comercializadas na cidade de Florianópolis, Santa Catarina, Brasil
Authors: Soares Bolivar , Cantos Geny Aparecida
Published: April 2006

Embora as hortaliças sejam amplamente comercializadas e consumidas no Brasil, o consumo de verduras cruas constitui importante meio de transmissão de parasitas intestinais. Neste estudo, avaliou-se a presença de formas transmissíveis de três tipos de hortaliças (rúcula, agrião e alface-crespa) comercializadas em cinco principais pontos de venda aos consumidores (dois supermercados, dois "sacolões" e em uma feira livre), na cidade de Florianópolis, Santa Catarina, Brasil, no período de junho 2003 a maio 2004. As hortaliças in natura foram lavadas com água e esta foi submetida ao método de sedimentação, durante um período de 24 horas. Concomitante à pesquisa laboratorial, foram avaliadas as condições de cultivo e manipulação de diferentes produtores agrícolas, os quais forneciam as hortaliças que eram posteriormente comercializadas em Florianópolis. A análise parasitológica mostrou alta freqüência de parasitas intestinais na maioria das amostras analisadas (40% a 76%). Entre os fatores envolvidos na contaminação das verduras, destacaram-se a origem das águas de irrigação, o acondicionamento, o transporte e a manipulação destas durante a coleta. Conclui-se que as hortaliças comercializadas nesta região têm relevante papel na transmissão de enfermidades intestinais, havendo necessidade de medidas específicas que evitem a contaminação desses vegetais.
Application of the first canonical variable in the evaluation of animal production trials
Authors: Detmann Edenio , Cecon Paulo Roberto , Andreotti Marcelo de Oliveira , Resende Flávio Dutra de , Sousa Daniel de Paula , Ponciano Niraldo José , Campos José Maurício de Souza , Souza Paulo Marcelo de , Vittori Andrea
Published: April 2006

The objective of this work was to evaluate the inter treatment discrimination according to feed conversion efficiency in several animal performance experiments. The variables investigated were: feed conversion ratio (FCR = intake: production ratio), feed efficiency index (FEI = production: intake ratio) and bio-nutritional index (BNI). The BNI was constructed from the first canonical variable obtained based on the multivariate analysis of variance of the intake and animal production (weight gain or milk production) variables. The results indicated that FCR and FEI reciprocated each other at experimental plot level but did not reciprocate at animal group or treatment level. This fact implicates distortions on the descriptive levels of probability of type I error for hypotheses tests and compromises the statistical and animal production inferences. On the other hand, the BNI index guarantees the maximum discrimination among experimental groups and allows to identify significant differences, which were not observe with FCR or FEI indexes. This fact can be associated to the incorporation of animal production intensity characteristics using BNI.
Pedagogia da pesquisa-ação
Authors: Franco Maria Amélia Santoro
Published: April 2006

A pesquisa-ação tem sido utilizada, nas últimas décadas, de diferentes maneiras, a partir de diversas intencionalidades, passando a compor um vasto mosaico de abordagens teórico-metodológicas, instigando-nos a refletir sobre sua essencialidade epistemológica, bem como sobre suas possibilidades como práxis investigativa. O presente trabalho aprofunda reflexões sobre a pertinência e as possibilidades da pesquisa-ação como instrumento pedagógico e científico, buscando indicativos de respostas às questões: a pesquisa-ação deve ser essencialmente uma pesquisa intencionada à transformação participativa, em que sujeitos e pesquisadores interagem na produção de novos conhecimentos? Deve assumir o caráter formativo-emancipatório? Mediando pesquisas e estudos já realizados, buscou-se estruturar um processo pedagógico para a pesquisa-ação, que organize a questão da coerência entre a ontologia e a epistemologia pretendida na pesquisa. Para tanto, foi necessário estabelecer referências às questões: de que pesquisa falamos quando nos referimos à pesquisa-ação? Ou mesmo, de que ação falamos quando nos referimos à pesquisa-ação? E ainda, como pesquisa e ação se integram na prática pedagógica da pesquisa-ação? O trabalho realça que a pesquisa-ação, estruturada dentro de seus princípios geradores, é uma pesquisa eminentemente pedagógica, dentro da perspectiva de ser o exercício pedagógico, configurado como uma ação que cientificiza a prática educativa, a partir de princípios éticos que visualizam a contínua formação e emancipação de todos os sujeitos da prática.
Aspectos clínicos da fenilcetonúria em serviço de referência em triagem neonatal da Bahia
Authors: Amorim Tatiana , Gatto Sara P.P. , Boa-Sorte Ney , Leite Maria Efigênia Q. , Fontes Maria Inês M. M. , Barretto Junaura , Acosta Angelina X.
Published: April 2006

OBJETIVOS: descrever as características clínicas dos pacientes com hiperfenilalaninemia acompanhados no Serviço de Referência em Triagem Neonatal (SRTN) do estado da Bahia. MÉTODOS: estudo descritivo transversal, tendo como amostra todos os pacientes com diagnóstico conhecido de Hiperfenilalaninemia residentes no estado da Bahia e acompanhados no SRTN até setembro de 2005. Tal população é composta de 46 famílias, num total de 51 pacientes. A análise dos dados foi descritiva, incluindo medidas de tendência central e dispersão. RESULTADOS: houve discreto predomínio do gênero feminino (52,9%). A maioria dos pacientes (78,4%) teve seu diagnóstico estabelecido através da triagem neonatal, tendo, portanto, tratamento precoce. Consangüinidade foi registrada em 32,6% das famílias. A média de início do tratamento entre os pacientes diagnosticados pela triagem neonatal foi de 56,6 37,8 dias, enquanto que entre os pacientes com diagnóstico tardio, foi de 7,1 anos. CONCLUSÕES: o estudo descreve um grupo de pacientes representativo de uma patologia incluída no Programa Nacional de Triagem Neonatal (PNTN), sendo, portanto, de relevância para a saúde pública. Entre os dados clínicos, chama a atenção a média de idade do início do tratamento, superior ao recomendado na literatura, alertando para a necessidade de um maior enfoque no diagnóstico precoce.
A relação entre o avaliador e o objeto avaliado
Authors: Feliciano Katia Virginia de Oliveira
Published: April 2006

Em um contexto onde o desenvolvimento do processo de institucionalização da avaliação da atenção básica requisita a participação dos envolvidos, fazendo crescer as dúvidas quanto à possibilidade de isenção dos avaliadores internos diante dos elementos de fracasso que forem identificados no trabalho cotidiano, este artigo discute uma questão que permeia toda prática avaliativa: a relação entre o avaliador e o objeto de avaliação. Adota-se a perspectiva de que na atenção à saúde o objeto da avaliação não é exterior ao avaliador e está inserido em uma rede simbólica que justifica os interesses e comporta uma interpretação da ação. Na inclusão do monitoramento e da pesquisa avaliativa à rotina dos serviços, a realização de uma análise relativamente distanciada resulta do reconhecimento de que a neutralidade é uma ilusão, ou seja, é a capacidade de aceitar as possibilidades de preconceber os fatos que permite, mediante um exercício prático sistemático, admitir a realidade como ela é, não como se gostaria que fosse. Assim, quanto mais se alcança um equilíbrio crítico e auto-crítico entre condições objetivas e subjetivas, mais se desvela a realidade.
Avaliação da gestão de programas de qualidade de vida no trabalho
Authors: Oliveira Patrícia Morilha de , Limongi-França Ana Cristina
Published: April 2006

A avaliação dos resultados de Gestão de Pessoas é hoje um dos temas mais desafiadores para esta área e que vem recebendo investimentos cada vez maiores. Nas questões relacionadas à Gestão dos Programas de Qualidade de Vida no Trabalho, muitas expectativas de resultados são levantadas: melhor percepção de bem-estar para as pessoas, o que influencia direta ou indiretamente na produtividade e nos resultados financeiros da Organização. Este artigo trata da percepção dos administradores sobre a possibilidade de se avaliar os resultados da Gestão de QVT, com base na pesquisa quantitativa sobre os fatores críticos de gestão. Acrescenta resultados de estudo de caso de uma empresa que pratica a avaliação dos resultados, mostrando seus indicadores para QVT. A partir deste conjunto de estudos, ratifica-se a necessidade de difusão de práticas para avaliação de resultados, e ainda, que tal avaliação pode ser feita de maneira clara, por meio de indicadores. O caso também demonstra que estas ferramentas auxiliam os profissionais a gerir a qualidade dos programas desenvolvidos.
Variações climáticas e uso de serviços de saúde em crianças asmáticas menores de cinco anos de idade: um estudo ecológico
Authors: Saldanha Celso Taques , Silva Ageo Mário Cândido da , Botelho Clovis
Published: April 2006

OBJETIVO: Analisar a variação dos períodos climáticos (seco ou chuvoso) e o uso de serviços de saúde para a asma em crianças menores de cinco anos de idade. MÉTODOS: Estudo ecológico, com coleta de dados secundários, através de análise dos prontuários das crianças com até cinco anos de idade e diagnóstico de asma, atendidas no Pronto-Socorro Municipal de Cuiabá. Obedecendo às características geográficas de Cuiabá (MT), foram considerados dois períodos climáticos: o período seco (maio a outubro) e o chuvoso (novembro a abril). RESULTADOS: O percentual de atendimentos das crianças consideradas com diagnóstico de asma foi de 12,2% (3.140/25.802), sem diferença entre os sexos. A faixa etária mais acometida foi a de três a cinco anos de idade. A taxa de hospitalização por asma foi de 1,3% (336/25.802), sendo de 10,7% (336/3.140) entre as crianças asmáticas atendidas no pronto-socorro. No período chuvoso o percentual de atendimento ambulatorial por asma foi maior que no período seco: 39,1% (1.228/3.140) versus 60,9% (1.912/3.140). Entretanto, no período seco houve maior percentual de hospitalização: 52,3% (176/336) versus 47,7% (160/336). As diferenças foram significativas (p < 0,05). CONCLUSÃO: O período climático seco, associado à maior taxa de hospitalização, parece estar relacionado aos casos mais graves de asma em crianças menores de cinco anos.
Marginal integrity and microleakage of direct and indirect composite inlays: SEM and stereomicroscopic evaluation
Authors: Soares Carlos José , Celiberto Leonardo , Dechichi Paula , Fonseca Rodrigo Borges , Martins Luis Roberto Marcondes
Published: April 2006

The aim of this study was to evaluate the microleakage of direct and indirect composite inlays by stereomicroscopy and scanning electron microscopy (SEM). Thirty bovine incisors were ground to obtain an incisal platform, simulating the occlusal surface of a human molar. Each tooth received two 8° proximal cavities with cervical finishing line prepared in dentine or enamel. One of the cavities was filled with Filtek Z250/Single Bond, using the direct technique, and the other was filled with with Solidex/Rely X ARC/Single Bond, using the indirect technique. The samples were stored in water at 37°C for 24 hours and placed in a 50% silver nitrate solution for 6 hours in a dark container. Next, the samples were washed under running water, immersed in a developing solution and exposed to fluorescent light for 12 hours. The teeth were then severed and evaluated for dye penetration by stereomicroscopy and SEM. There were no significant differences between the direct and indirect techniques for the cervical finishing line in enamel, but for the finishing line in dentin, the indirect technique allowed less microleakage than the direct technique. SEM analysis showed leakage similar to that observed by stereomicroscopic analysis. The use of stereomicroscopic and SEM evaluations improves microleakage analysis.
Stability Analysis of Continuous-Flow Gas Lift Wells
Authors: Poblano E. , Camacho R. , Fairuzov Y. V.
Published: April 2006

Flow instability (i.e., heading) in gas lift wells is examined in this paper. A review of previous work done in this area is also given. A model of a gas lift well was developed and validated using field data obtained in tests of a gas lift well in the Maloob field. On the basis of the model developed and the existing stability criteria, theoretical gas lift stability maps were developed and compared with the field data. The effect of the injected-gas flow rate, the injection-port size, and the tubing diameter on the flow stability was studied using the stability maps obtained in this work. It is shown how the proposed maps can be used as a simple and efficient method for predicting the stability threshold in designing gas lift systems.
Stability of an Open Hole Completed in a Limestone Reservoir With and Without Acid Treatments
Authors: Morita Nobuo , Doi Tomoki , Kinoshita Takanori
Published: April 2006

Because a borehole in a limestone formation is more stable than expected, an openhole completion without a slotted/perforated liner has become popular recently. However, the following three items are not clear: (1) Why a borehole in a limestone formation is so stable, (2) why a borehole in a limestone formation can be completed without a liner regardless to the formation strength, and (3) the question of stability after acid treatments. To answer these questions, two types of laboratory experiments are conducted. One of them is a series of borehole stability experiments using 1.5- and 2.36- to 2.39-in.-diameter borehole in a 10.×5×10.5×17.5-in. limestone blocks with polyaxial confining pressures simulating a horizontal well with three different principal in-situ stresses. Two types of limestones are used with and without borehole acid treatments and two borehole sizes are used to check the size effect. Another type of experiment is the acid squeezing experiment, in which 15% HCl acid solution is squeezed from one end of a cylindrical core and the change of porosity, permeability, and hardness are measured throughout the cores.

The results showed the following new discoveries:

The limestones have two distinct failure envelopes. The failure plastic strain is relatively small for normal shear failure, while it becomes as much as 10 times larger when a shear failure is induced after pore collapse. One of the limestones used in these experiments has only 1,751 psi UCS, yet the borehole was unexpectedly stable. The reason was that the borehole failure is induced by a shear failure after pore collapse. It is well known that pore collapse is induced within a formation during compaction; however, a shear failure after pore collapse has never been observed when one boundary is open like an open hole. The confining stress inducing borehole failure was not significantly different between hydrostatic and directional loadings. According to the Kirsch's solution, the directional load should significantly increase the stress concentration. It is well known that the nonlinearity of rock reduces the stress concentration induced by directional loading; however, the present experiments showed that the magnitude of the reduction of stress concentration was larger than expected. Wormholes stabilize boreholes even though acidizing weakens formation. Therefore, enhancing wormholes is recommended when a borehole in a limestone formation is acidized.

Normally, because limestones are relatively strong, open holes are likely stable; however, the strength must be checked if they need to be completed without a linear protection. To help a reader applying the laboratory results to field problems, a guideline to complete an open hole without a liner protection in limestone reservoirs is provided, with calculation results using a nonlinear finite-element model.
Zero-Damaging Stimulation and Diversion Fluid: Field Cases from the Carbonate Formations in North Kuwait
Authors: Al-Mutawa Majdi , Al-Anzi Ealian , Jemmali Mohamed , Chang Frank , Samuel Elsamma , Samuel Mathew
Published: April 2006

The high permeability contrast seen in the producing zones of the oil wells of the north Kuwait Mauddud formation makes the uniform stimulation of this carbonate formation a challenge. To achieve diversion, polymer-based fluids were used earlier but with limited success. Recently, a nonpolymeric system containing a viscoelastic-surfactant-based (VES) self-diverting acid (SDA) was used to divert and effectively stimulate entire pay zones with great success.

Production logs run before and after the stimulation treatments indicate stimulation of the entire perforated intervals. Stimulation using this new system on the first 17 wells resulted in a production increase of approximately 30,000 BOPD—much higher than that expected from conventional treatments. The wells that were not producing earlier after several conventional treatments are now producing naturally after treatments using this nondamaging system. Nearly 100 wells in the same reservoir were treated with this system after successful introduction of the technology. The use of this technology is now extended to matrix stimulation of gas producers, water injectors, and disposal wells.
Impact of Transient-Flow Conditions on Electric Submersible Pumps in Sinusoidal-Well Profiles: A Case Study
Authors: Noonan S. G. , Kendrick M. A. , Matthews P. N. , Sebastiao N. , Ayling I. , Wilson B. L.
Published: April 2006

Chevron Corp. has 13 wells producing offshore Africa with electric submersible pumps (ESPs) that experienced problems primarily caused by the transient nature of the multiphase inflow through the sinusoidal-well profiles. A study completed in 2002 used a transient multiphase simulator to model the sinusoidal sections of each producer and to calculate the conditions that the ESPs could see over the life of the well for various drawdown conditions and speeds. This paper focuses on how the results from the simulator were validated and used to reduce operational downtime and improve future ESP completion designs. This paper also will demonstrate how severe sinusoidal-well profiles impact production operations.
Investigation of a New Tool To Unload Liquids From Stripper Gas Wells
Authors: Ali Ahsan J. , Scott Stuart L. , Fehn Brad
Published: April 2006

Liquid loading in low-production gas wells is a common problem faced in many producing regions around the world. The techniques available to remove liquids from the wellbore impose significant capital and operational costs. This study investigates a new method for unloading and restoring continuous production of low-rate (i.e., stripper) gas wells. The performance of a patented vortex-flow-modifier tool was examined using a 125-ft vertical-flow loop of 2-in.-diameter clear PVC pipe. The vortex device was found to alter the basic flow structure in the pipe, resulting in improved liquid flow. The tool was observed to reduce tubing-pressure loss by up to 17% and lower the minimum gas velocity required to lift liquids up the tubing string.
Optimal Well Placement in Heterogeneous Reservoirs Through Semianalytic Modeling
Authors: Hazlett R. D. , Babu D. K.
Published: April 2006

The need for accurate well-productivity models with arbitrary well trajectories spurred a revival in analytic solution methodology for fluid transport problems. Analytic formulations often depict single-phase flow throughout the reservoir. The Babu-Odeh horizontal-well solution for abox-shaped reservoir with spatially invariant properties is generalized here toallow closed-form solutions for heterogeneous media. A reservoir is decomposed into interacting regions, each with its own reservoir properties and associated analytic potential flow solution. Using established boundary element techniques, pressure and flux continuity are imposed at selected interface points to solve for the steady material exchange between regions. Constant pressure and zero flux features (fractures and barriers) are easily entertained at region boundaries. The 2D, pseudo steady-state solution for heterogeneous media is embedded within a reservoir performance feedback loop of a powerful gradient search method to produce a robust optimal infill well placement algorithm. Utilizing this approach, new criteria are developed concerning optimal placement of vertical wells for primary production with respect to heterogeneity, asymmetry, and anisotropy. The semianalytic method has been extended to 3D flows to serve as a compute engine for a new generation of reservoir management and optimization tools.
Application of Stream-Conversion Methods To Generate Compositional Streams From the Results of a Multimillion-Cell Black-Oil-Simulation Study of the Shaybah Field
Authors: Al-Awami Bassam , Hemanthkumar K. , Al-Awami Fatema , Mohammedali Mansour
Published: April 2006

Detailed compositional simulation of a giant reservoir with many components is not practical. However, detailed multimillion-cell black-oil simulation of giant reservoirs is now quite feasible. In this work, we apply an efficient method to generate the compositional rates from a black-oil simulation of the giant Shaybah field.

In situations in which the reservoir recovery mechanism is not dominated by compositional effects, an equation-of-state (EOS)-based stream-conversion method can be used. This stream-conversion method relies on the fact that when laboratory pressure/volume/temperature (PVT) data measured on available well-stream compositions are used to generate the black-oil PVT tables, some of the compositional information is lost. The stream-conversion model retains this valuable compositional information and applies it to each producing-well completion in the black-oil simulation at every timestep.

As proof of the concept, the stream-conversion method was applied to a black-oil simulation and to a limited (eight-component) compositional simulation to generate a 17-component compositional stream, and the results were compared to the respective full EOS compositional simulation for a relatively small sector (250,000 cells) of the giant Shaybah field. The compositional stream rates are in excellent agreement with the stream-converted black-oil results. As would be expected, the computational costs of using the EOS-based compositional simulator (with 17 components) are in excess of 40 times the black-oil-simulation time for the small-sector model. In general, the stream-conversion method can be used to generate the dynamically varying compositional streams from any black-oil simulation for use in the design and operation of surface facilities and in calculating the amounts of a certain cut [e.g., natural gas liquids (NGL)] from the production streams.
Simulating Carbon Dioxide Sequestration/ECBM Production in Coal Seams: Effects of Permeability Anisotropies and the Diffusion-Time Constant
Authors: Smith Duane H. , Bromhal Grant , Sams W. Neal , Jikich Sinisha , Ertekin Turgay
Published: April 2006

Coalbed methane now accounts for a significant fraction of domestic natural-gas production. Injection of carbon dioxide (CO2) into coal seams is a promising technology for reducing anthropogenic greenhouse-gas emissions and increasing ultimate production of coalbed methane. Reservoir simulations are an inexpensive method for designing field projects and predicting optimal tradeoffs between maximum sequestration and maximum methane production. Optimum project design and operation are expected to depend on the anisotropy of the permeability along the face-cleat and butt-cleat directions, the spacing between cleats, and the sorption isotherms for methane and CO2.

In this work, a dual-porosity coalbed-methane simulator is used to model primary and secondary production of methane from coal for a variety of coal properties and operational parameters. It is assumed that the face and butt cleats are perpendicular to each other, with horizontal wells parallel to one type of cleat and perpendicular to the other. The well pattern consists of four horizontal production wells that form a rectangle, with four shorter horizontal wells centered within the rectangle. In the limiting case of no permeability anisotropy, the central wells form a "plus" sign within the square of production wells. All wells are operated as producers of methane and water until a specified reservoir pressure is reached, after which the central wells are operated as injectors for CO2. Production of methane continues until the CO2 concentration in the produced gas is too high.

The simulation results predict the optimum lengths of the injection wells along the face- and butt-cleat directions and show how these optimum lengths depend on the permeabilities in the two directions. If the cleat spacing is sufficiently small, and diffusion of the gas through the pores to the cleats is sufficiently rapid, instantaneous sorption may be assumed. Otherwise, the field performance depends on the diffusion-time constant that characterizes the rate of transfer between the cleats and the coal matrix. The pressures at which the injection wells are operated also affect the amounts of CO2 sequestered through the pressures and volumes of the sorption isotherms.
A Simplified Method to Predict and Prevent Asphaltene Deposition in Oilwell Tubings: Field Case
Authors: Al-Kafeef Saad F. , Al-Medhadi Fahed , Al-Shammari Ali D.
Published: April 2006

The natural state of asphaltenes in petroleum fluids is described as a colloidal system stabilized, to some extent, by the resins that act as peptizing agents. Destabilization of colloidal asphaltenes appears to happen as a result of changes in temperature, pressure, and composition. This can significantly affect the production efficiency of a reservoir during oil recovery.

The phenomenon of asphaltene flocculation and deposition in well tubing appears to be influenced by two mechanisms: the fluid-phase (gas/liquid/solid) separation and the well-flow regime. Predictions of the onset of asphaltene flocculation determined by fluid-phase laboratory studies do not necessarily imply that asphaltene deposition will occur during flow conditions. This paper presents a method for predicting the onset of asphaltene deposition under well-flow conditions. This method will allow us to take preventive actions before asphaltenes problems occur by keeping the asphaltenes dispersed in the oil phase.

A well-monitoring technique was used in west Kuwait Marrat (Jurassic) deep wells to monitor the well-flow pressure by use of a programmable data logger. The data gathered from the logger predicted the onset of the flow-regime mechanism that influenced asphaltene deposition in well tubing. The deposition thickness of asphaltenes in well tubing was estimated by the data and was found to agree with the results obtained by the caliper test.
The Value of Cement Innovation: Reduced Cycle Time Saves Money
Authors: Myers Roger , Mack David J. , Kendrick Daniel , Woo George , Matz David , Hina Derek
Published: April 2006

Lightweight, low-compressive-strength cement slurries save Appalachian basin operators thousands of U.S. dollars per well when compared with two-stage cement jobs using a packer-collar tool. The average amount of annular fill-up that is required in the typical southern West Virginia Devonian shale well is 3,000 ft. Because the shale is naturally fractured and has a low fracture gradient of 0.3-0.4 psi/ft, many operators opt to cement the air-drilled, unconventional gas wells with a 12-ppg lightweight silicate cement.

Over the past 5 years, more than 800 wells have been cemented with water-extended cement slurry, pumped at 12 ppg. Interestingly, the cement's compressive strength in 72 hours measures only 500-700 psi, not nearly enough to be "seen" with the cement-bond logging tools most commonly employed. In fact, at least one operator waits a full 7 days before running a variable-density log because that is about the time needed for the cement to develop enough compressive strength and acoustical impedance to be seen.

While solving one problem related to cutting authorized-for-expenditures well costs, the lightweight cement caused another problem: lost production days because of waiting on cement (WOC). Using knowledge of available Portland cements and a proprietary compressive-strength enhancing agent, a new cement blend was developed that could get higher strengths and better acoustical impedance. This paper will document how one large northeast operator successfully solved the problem of cycle-time reduction while maintaining the cement density at 12 ppg. Key aspects related to the solution, including laboratory testing of the cement and cement additives and examples of post-solution cement-bond logs, will be shown. Economics related to lost days of production over a 100-well drilling program will also be discussed.
Silica-Scale Inhibition for Steam Generation in OTSG Boiler
Authors: Pedenaud Pierre , Goulay Caroline , Pottier Fabien , Garnier Olivier , Gauthier Bernard
Published: April 2006

The production of extra-heavy oil or bitumen using the steam-assisted gravity-drainage (SAGD) method entails the generation and injection of a large quantity of steam into the reservoir. A similar quantity of hot water is produced together with the oil. Taking into consideration environmental regulations, it is probable that partial, or even total, recycling of the produced water into steam will be required.

After circulating in the ground, production water may contain high concentrations of silica (up to 400 mg/L). Silica removal is very expensive in terms of investment and operating costs. The risk of silica-salt deposition in the boiler tubes becomes significant when the silica content in the feedwater exceeds 100 mg/L [oncethrough-steam-generation (OTSG) boiler-supplier specifications]. Deposition of silica increases local thermal resistance and can lead to tube failure. The silica-removal process is also an environmental issue owing to the production of sludge.

This paper demonstrates that silica-scale inhibitors can be used in steam generation in an OTSG boiler. The original laboratory test program and results obtained are presented. Test results were corroborated on an industrial OTSG boiler in operating conditions. Results show that use of silica-scale inhibitors instead of silica removal could generate substantial savings in cost. The use of silica scale for steam generation in heavy oil exploitation has been incorporated into French patent 2,858,314-A1 (Gauthier et al. 2003).
Characterization of Partially Formed Polymer Gels for Application to Fractured Production Wells for Water-Shutoff Purposes
Authors: Sydansk R. D. , Xiong Y. , Al-Dhafeeri A. M. , Schrader R. J. , Seright R. S.
Published: April 2006

A laboratory study characterized partially formed chromium(III)-carboxylate/acrylamide-polymer (CC/AP) gels for water shutoff in fractures. These partially formed gels showed much lower effective viscosities during placement than comparable fully formed gels. During placement, leakoff rates through fracture faces were low for gelants and partially formed gels. During the first brine injection after gel placement, the pressure gradient required to breach the gel increased with the increasing polymer concentration. Most gel remained in the fracture and did not wash out. During brine flow through "wormholes" in the gel, stabilized residual-resistance factors (Frr) were large and increased with increasing polymer concentration.
Effect of Drainage Height and Grain Size on Production Rates in the Vapex Process: Experimental Study
Authors: Yazdani Ali J. , Maini Brij B.
Published: April 2006

Interest in the vapor-extraction (Vapex) process for heavy-oil and bitumen recovery has grown considerably as a viable and environmentally friendly alternative to the currently used thermal methods. The potential for the success of the Vapex process is even more attractive in some scenarios that preclude the thermal methods. The presence of an overlying gas cap and/or bottomwater aquifer, thin pay zones, low thermal conductivity, high water saturation, and unacceptable heat losses to overburden and underbur-den formations are some of the limitations with the thermal techniques, which potentially can be overcome by Vapex implementation. However, predicted low production rates by previous researchers for field application of the Vapex technique remain a serious barrier to commercial applications of the process. The scaleup methods that have been used by previous workers for translating the laboratory results to field predictions were based primarily on the reservoir transmissibility. An analytical model developed by Butler and Mokrys1 showed that the oil rate should be proportional to the square root of reservoir transmissibility. The effect of convective dispersion between solvent and virgin heavy oil in porous media was ignored in developing this model.

The main objective of this work is to develop an improved scaleup method for the Vapex process using physical-model experiments carried out in models of different sizes. In this paper, we report the results of a new series of experiments that extend the previously reported results of Karmaker and Maini2 to a significantly wider range of model heights. These new experiments used a new design of slice-type physical models that places the sandpack in the annulus formed by two cylindrical pipes. Combining the new results with the previous data of Karmaker and Maini,2 we show that the transmissibility-based scaling-up method seriously underpredicts the results at larger scales. This observation suggests that much higher rates can be expected in the field implementation of the Vapex process.

A new correlation also has been proposed for scaling up the experimental data to the real field cases. It indicates the height dependency of the convective-dispersion contribution, which can be the dominant mass-transfer mechanism for the process, to be a higher order than previously postulated. Experimental results from this work show that the stabilized rate is a function of drainage height to the power of 1.1 to 1.3, instead of the square-root functionality of the Butler and Mokrys1 model.
Development of Associative Polymer Technology for Acid Diversion in Sandstone and Carbonate Lithology
Authors: Eoff Larry , Dalrymple Dwyann , Reddy B. R.
Published: April 2006

This article describes the use of associative polymer technology (APT) to achieve fluid diversion during an acid stimulation treatment. APT involves the use of a very-low-viscosity aqueous-polymer solution. It reacts immediately with the formation surface to significantly reduce the ability of subsequent aqueous fluids to flow into high-permeability portions of the rock. The first stage containing the APT predominately will enter the most permeable area, diverting the following acid stage(s) to less-permeable sections of the rock. APT has little or no effect on the flow of subsequent hydrocarbon production. Furthermore, in rock containing significant proportions of sandstone-type lithology, the water permeability of the treated zone is decreased permanently, resulting in post-treatment reduced water production from the treated zone.

A general description of associating polymers and their properties, as well as a detailed description of the laboratory development of the current system, are both discussed. Laboratory data will show the effectiveness of APT in reducing the ability of aqueous fluids to flow through porous media. Parallel flow studies using water-saturated and oil-saturated cores are presented that show the ability of APT to divert acid in both sandstone and carbonate cores. These tests also show the ability of APT to decrease water permeability in the water-saturated core while the diverted acid increases the oil permeability of the oil-saturated core.
Simplified Wellbore-Flow Modeling in Gas/Condensate Systems
Authors: Kabir C. S. , Hasan A. R.
Published: April 2006

Predicting long-term reservoir performance with realistic wellbore models is fraught with uncertainty owing to the complexity of two-phase flow. That is because even a calibrated two-phase-flow model departs from its expected performance trend when changes in flow conditions occur. These inevitable changes include gas/liquid ratio, wellhead pressure, and flowline pressure with time, among others. Influx of water further exacerbates the prediction problem.

This study explores the possibility of using simplified approaches to compute bottomhole pressure (BHP) from wellhead pressure (WHP), measured rates, gravity of producing fluids, and tubular dimensions. BHP computations on three independent data sets comprising 167 gas/condensate-well tests suggest that the no-slip homogeneous model applies quite well. Statistical results show the homogeneous model compares quite favorably with mechanistic two-phase-flow models. However, the main advantage of the simplified model is that its recalibration with field data is not required because the gas/oil ratio increases with time, thereby making the model increasingly reliable.

Most field data sets suggest random error in BHP calculations; uncertainty in rate measurements appears to be the most probable cause. High gas/liquid ratio (GLR) systems can tolerate large errors in rate measurements, but low-GLR wells demand greater accuracy because of increasing importance of the hydrostatic head.
Uncertainties in Standard Analyses of Boundary Effects in Buildup Data
Authors: Larsen Leif
Published: April 2006

Boundary effects are often observed in buildup data—or at least that is the conclusion frequently drawn from an observed increase in derivative on a log-log plot or an increase in slope on a semilog plot. Furthermore, if (for instance) it is concluded that the effects of a sealing fault are seen in a given data set, then simple line methods or direct analytical-modeling efforts are normally used to determine the distance to the boundary. A sealing fault is the normal choice of boundary model if a doubling is observed in derivative or semilog slope. If a four-fold increase in derivative is observed, then a model with the well placed somewhere between two sealing faults forming a right angle would be a normal choice. But what if the two faults are not sealing? If the flow capacity on the other side of the faults is only one-third of the value on the well side, what will be the derivative characteristics?

Problems like these are addressed in detail in this paper, with a series of simple rules given for possible combinations that will generate buildup data of a specific type (i.e., with specific "familiar characteristics"). The rules can be used to list alternative interpretations without running separate analyses. For instance, it is shown that the derivative characteristics of any sector model bounded by sealing faults correspond to an infinite number of two-zone sector models with an angle between the boundaries and permeability contrast satisfying a single equation. Other pairs of models with similar characteristics are models with partially sealing faults and specific three-zone sector models, and either of these types of models and radial composite models. This clearly complicates analyses.

Also addressed are problems related to possible differences in the boundary effects observed in drawdown and buildup data for certain models. As one example, U-shaped and sector models can have identical buildup characteristics over a wide time range, although drawdown data from the models have distinctly different boundary characteristics. Radial composite and composite sector models are also of this type, with potentially significant differences between drawdown and buildup data. The reason for bringing up such cases is to emphasize the importance of attempting to collect high-quality drawdown data in addition to buildup data to limit the range of possible interpretation models.

For completeness, effects of uncertainties in basic input parameters on the final analyses are also covered in the paper.
Role of Peripheral Innervation in P‐Chloroamphetamine—Induced Ejaculation in Anesthetized Rats
Authors: Clément Pierre , Kia Hossein K. , Droupy Stephane , Bernabe Jacques , Alexandre Laurent , Denys Pierre , Giuliano François
Published: April 2006

ABSTRACT: The occurrence of ejaculation, which consists of 2 distinct phases (emission and expulsion), requires a tight coordination of peripheral autonomic and somatic nerves. However, some aspects of the mechanism of ejaculation are not clearly defined. To clarify this issue, we used the p‐chloroamphetamine (PCA)‐induced ejaculation model in anesthetized rats and investigated the effects of selective peripheral nerves lesions on seminal vesicle and bulbospongiosus (BS) muscle activities as representing physiological markers of emission and expulsion phases, respectively. In intact rats, ejaculation induced with PCA (intraperitoneal 5 mg/kg) correlated with coordinated increases in seminal vesicle pressure (SVP) and BS electromyographic activity. PCA‐induced ejaculation was still observed in rats with bilateral lesion of hypogastric nerves (HNx), lumbar paravertebral sympathetic chain (LSCx), or dorsal nerves of the penis (DNPx). Conversely, bilateral section of pelvic nerves (PNx) or L6‐S1 dorsal roots (DRx) abolished PCA‐induced ejaculation. The amplitude of SVP increases induced by PCA was reduced in PNx, HNx, and LSCx rats, whereas it was unchanged in DRx and DNPx rats. The time interval between SVP increases and BS muscle contractions induced by PCA was comparable in the different neural lesion groups. In conclusion, PCA initiates both emission and expulsion independently from each other. In this model, afferents conveyed by the pelvic nerves appear to be unnecessary for occurrence of BS muscle contractions but are essential for a complete ejaculatory response.
Cattle and class? Rights to grazing land, family organization and class formation in Msengezi
Authors: Cheater A. P.
Published: April 2006

Opening Paragraph

In studying class formation in rural Africa, many subtleties of this process are initially elusive, even when the process itself appears to be quite straightforward. The elusiveness of reality frequently results, at least in part, from the assumptions made by the researcher. So, for example, in studying one area of freehold tenure in Zimbabwe, in which ‘squatting’ is officially disapproved and where the land is legally inherited by a single heir, the informal allocation to others of rights to arable land for cultivation has obvious importance in the process of class formation. Less obvious, however (at least to me at the time), was the significance of grazing usufruct.
From equal to better: investing the chief among the northern Yaka of Zaïre
Authors: Devisch René
Published: April 2006

Introduction

Among the Northern Yaka of Zaïre the office and function of the chief is thought of as prior to and as the source of all things: the chief represents and surpasses his subordinates by his twofold function. First, he is asovereign rulerwho alone personifies unity, perpetuity and high authority. But the chief fails to live up to these chiefly ideals since his physical body ages and he cannot escape death or transcend the succession of generations and political scenes and factions. This failure seems to be remedied, however, not so much by concealing the chiefs bodily transitoriness through a mystifying cult, but by identifying the chief in his body with the origin of the political institutions. Embodying the founding ancestors, the chief ‘re-presents’ or makes present ‘the primal space–time order’ (yitsi khulu). The ruler thus personifies the legitimate political order: he re-presents and imposes the perennial hierarchical social organisation, territorial unity and moral order. In his enthronement and rule, he must re-enact the founding dramas of conquest and life transmission to renew cultural time by linking it to the ‘primal and permanent space–time order’. Sacrificial death, mortuary ritual, rebirth, purification, etc., re-enact the founding dramas and provide transformative metaphors, linking men and women, life and death, inside and outside, ascendant and descendant, before and after, the local territory and Yaka society.