bluuebunny/crossref_metadata_2025 huggingface dataset:
Extrato de orégano como aditivo em rações para frangos de corte
Authors: Fukayama Ellen Hatsumi , Bertechini Antonio Gilberto , Geraldo Adriano , Kato Reinaldo Kanji , Murgas Luis David Solis
Published: April 2006

Os objetivos neste experimento foram avaliar os efeitos da inclusão de extrato de orégano (EO) como aditivo promotor de crescimento nas rações sobre o desempenho, o sistema imune (peso e tamanho da bursa de Fabricius, peso do baço e do timo), as características anatomo-fisiológicas do trato gastrointestinal (altura de vilosidade, profundidade de cripta e suas relações), a microbiologia do ceco e o pH do duodeno e do ceco de frangos de corte. Foram utilizados 1.440 pintos de corte machos Cobb 500, em duas fases de criação (1 a 21 e 1 a 42 dias de idade), distribuídos em delineamento inteiramente casualizado, com seis tratamentos e oito repetições de 30 aves. Utilizou-se ração basal (RB) para as três fases de criação (1 a 21, 22 a 35 e 36 a 42 dias de idade), constituindo os seguintes tratamentos: T1 - RB; T2 - RB com antibiótico (25 ppm de bacitracina de zinco); T3 - RB com 0,025% EO; T4 - RB com 0,050% EO; T5 - RB com 0,075% EO; e T6 -RB com 0,100% EO. Observou-se que os tratamentos não influenciaram o desempenho e os pHs dos conteúdos duodenal e cecal das aves nas duas fases de criação. As variáveis de imunidade e avaliação anatomo-fisiológica do trato gastrointestinal aos 21 dias não apresentaram diferenças. Apenas o peso do baço e a altura de vilosidade aos 42 dias de idade foram influenciados pelos tratamentos. Houve redução no número de bactérias no ceco das aves à medida que se elevou o conteúdo do extrato de orégano nas rações, indicando que houve ação antimicrobiana dos componentes deste extrato. Na condição em que foi realizado o experimento, o uso do extrato de orégano como aditivo promotor de crescimento não ocasionou efeito diferente dos demais tratamentos (antibiótico e testemunha).
Efeitos de fontes protéicas na dieta sobre a morfologia intestinal e o desenvolvimento pancreático de leitões recém-desmamados
Authors: Scandolera Antônio João , Thomaz Maria Cristina , Kronka Rodolfo Nascimento , Fraga Alessandro Luís , Budiño Fábio Enrique Lemos , Huaynate Rizal Alcides Robles , Ruiz Urbano dos Santos , Cristani José
Published: April 2006

Objetivou-se neste trabalho analisar os efeitos do uso de hidrolisado protéico do conteúdo celular de levedura (HPCCL), da proteína isolada de soja (PIS), do hidrolisado protéico de mucosa intestinal de suínos (HPMIS) e do leite em pó integral em substituição parcial ao farelo de soja sobre a morfologia do intestino delgado e o desenvolvimento pancreático de leitões aos 7 e 14 dias pós-desmame. Foram utilizados 44 leitões desmamados aos 21 dias de idade, com peso de 5,5 ± 0,6 kg, alimentados desde o desmame com as seguintes dietas isonutritivas: FS - ração à base de milho e farelo de soja; LPI - ração FS + leite em pó integral; LPI+HPMIS - ração LPI mais HPMIS; LPI+PIS - ração LPI mais PIS; LPI+HPCCL- ração LPI mais HPCCL. Os tratamentos não influenciaram a morfologia intestinal dos leitões, evidenciando que nenhuma das fontes protéicas utilizadas foi capaz de minimizar os efeitos deletérios da mudança da alimentação sobre a vilosidade intestinal. Os animais alimentados com LPI+PIS e LPI+HPMIS apresentaram, aos sete dias pós-desmame, o maior desenvolvimento pancreático. Concluiu-se, portanto, que todas as fontes protéicas estudadas foram igualmente adequadas para a formulação de dietas de desmame.
Efeito de diferentes níveis de proteína bruta na ração sobre o desempenho e as características de carcaça de cordeiros terminados em creep feeding
Authors: Ortiz Jessé Siqueira , Costa Ciniro , Garcia Cledson Augusto , Silveira Liciana Vaz de Arruda
Published: April 2006

O experimento foi realizado com os objetivos de avaliar o efeito dos níveis de proteína bruta (15, 20 e 25%) na ração concentrada sobre o desempenho e as características de carcaça de cordeiros Suffolk alimentados em creep feeding e analisar economicamente esse sistema de produção. Foram utilizados 15 cordeiros inteiros, nascidos de partos simples, alimentados ad libitum com as rações experimentais duas vezes ao dia. Estimaram-se o consumo de médio diário de ração, pelo cálculo da quantidade fornecida e das sobras; o ganho de peso, pela pesagem dos animais a cada 14 dias; o peso vivo ao abate (PVA) dos cordeiros em jejum (16 horas); e o rendimento de carcaça quente, após abate e evisceração. O ganho médio diário foi influenciado pelos níveis de proteína, quando considerada a idade de abate como covariável. Não houve efeito significativo dos níveis de proteína sobre as características de carcaça. No sistema de alimentação e terminação de cordeiros Suffolk em creep feeding, a ração deve ser balanceada com 25% de proteína bruta, uma vez que esse nível proporcionou maior ganho de peso médio diário e não alterou as características de carcaça.
Tempo de latência e exatidão para leitura e nomeação em crianças escolares: estudo piloto
Authors: Stivanin Luciene , Scheuer Claudia Inês
Published: April 2006

O objetivo deste estudo foi verificar o tempo de latência e o número de acertos para estímulos equivalentes em nomeação de figuras e leitura de palavras isoladas em voz alta, considerando os atributos do material escrito (freqüência de ocorrência e extensão da palavra). Os participantes foram crianças de 2ª a 4ª séries do ensino fundamental de uma escola pública e municipal da cidade de São Paulo, sem alterações gerais de desenvolvimento, de linguagem e escolares. A prova de leitura foi constituída por 32 palavras, balanceadas por freqüência de ocorrência no material escrito e extensão da palavra. A prova de nomeação foi constituída por figuras com nomes equivalentes às palavras da prova de leitura. Os estímulos foram apresentados individualmente na tela de um computador com software específico para análise do tempo de latência e das respostas. Foram analisados o número de acertos e o tempo de latência para as respostas. Para o tempo de latência, foi observada a influência das variáveis do material escrito, ou seja, palavras de baixa freqüência e de maior extensão foram acessadas mais lentamente por todas as crianças. Quanto ao número de respostas corretas, não houve diferença estatística entre as séries escolares na prova de leitura. Porém, com a idade e a escolarização, as crianças tornam-se mais rápidas para iniciar a leitura de palavras isoladas e para nomear figuras equivalentes.
Óbitos neonatais: por que e como informar?
Authors: Pedrosa Linda Délia Carvalho de Oliveira , Sarinho Silvia W. , Ordonha Manoelina de Albuquerque Rocha
Published: April 2006

Os óbitos neonatais se constituem no mais importante componente da mortalidade infantil (MI) no Brasil, tendo como principais causas a asfixia, o baixo peso ao nascer, as afecções respiratórias do recém-nascido, as infecções e a prematuridade. São situações vinculadas a falhas de prevenção e a ampla rede de determinantes desses óbitos precisa ser conhecida a partir das informações disponibilizadas pelos sistemas nacionais de informação. Uma boa cobertura do sistema, agilidade e coleta de informações confiáveis em todos os níveis e o controle do fluxo dessas informações, asseguram a validade dos indicadores gerados, permitindo a escolha da melhor abordagem preventiva. Neste artigo, são apresentadas as diversas fontes de pesquisa em óbitos neonatais, seus usos e limitações ressaltando o papel dos profissionais de saúde na geração de dados confiáveis. Foram consultados manuais técnicos do Ministério da Saúde, teses, dissertações e livros sobre o tema e realizada uma revisão nos bancos de dados eletrônicos Medline, LILACS, SCIELO e PAHO em artigos disponíveis de 1980 a 2004, a partir dos descritores "mortalidade infantil", "mortalidade neonatal", "mortalidade neonatal precoce", "causa básica de óbito", "sistemas de informação", "informação em saúde", "registros médicos", "registros de mortalidade".
Limnological study of a Pantanal saline lake
Authors: Medina-Júnior P. B. , Rietzler A. C.
Published: April 2006

Limnological studies involving physical, chemical and biological aspects, with emphasis on the zooplankton community, were carried out in a saline lake of the Pantanal floodplain, in the subregion of Nhecolândia (Mato Grosso do Sul, Brazil), during the dry and wet seasons of the local hydrological cycle. The results show that the lake is not directly affected by the flood-pulse through superficial coalescence, probably receiving groundwater instead. Most of the measured variables showed extremely high values, particularly dissolved salts, pH, conductivity, nutrients and chlorophyll a. These values were highest during the dry period due to the system's low water volume. The zooplankton community was basically represented by Metacyclops mendocinus, which displayed high population densities throughout the periods studied. The low diversity recorded is congruent with other studies on continental saline water-bodies.
Spatial distribution and abundance of nonindigenous coral genus Tubastraea (Cnidaria, Scleractinia) around Ilha Grande, Brazil
Authors: Paula A. F. , Creed J. C.
Published: April 2006

The distribution and abundance of azooxanthellate coral Tubastraea Lesson, 1829 were examined at different depths and their slope preference was measured on rocky shores on Ilha Grande, Brazil. Tubastraea is an ahermatypic scleractinian nonindigenous to Brazil, which probably arrived on a ship's hull or oil platform in the late 1980's. The exotic coral was found along a great geographic range of the Canal Central of Ilha Grande, extending over a distance of 25 km. The abundance of Tubastraea was quantified by depth, using three different sampling methods: colony density, visual estimation and intercept points (100) for percentage of cover. Tubastraea showed ample tolerance to temperature and desiccation since it was found more abundantly in very shallow waters (0.1-0.5 m), despite the fact that hard substratum is available at greater depths at all the stations sampled. At most sites, 1 to 5 colonies per 0.25 m² were found most frequently, but occasionally more than 50 colonies were found per 0.25 m², indicating a somewhat gregarious spatial distribution for this coral. The coral Tubastraea was found to occupy slopes of every possible angle in the Canal Central of Ilha Grande, but more colonies were found occupying slopes of 80 to 100°. Therefore, its insensitivity to angles of recruitment and its tolerance for different depths makes it an organism with great ecological tolerance, with a potential to colonize new areas and increase its current range in Brazil's coastal waters.
Fisioterapia respiratória no empiema pleural: revisão sistemática da literatura
Authors: Britto Murilo Carlos Amorim de , Duarte Maria do Carmo Menezes Bezerra , Silvestre Silvia Maria Mendes da Conceição
Published: April 2006

Alguns dos recursos utilizados em fisioterapia respiratória não são baseados em evidências científicas comprovadas. A má utilização desses recursos pode ser nociva do ponto de vista de efeitos adversos, ou levar a um custo-benefício não favorável. Os autores fizeram uma revisão sistemática da literatura, através das bases de dados Oldmedline, Medline, Cinahl, Lilacs, e nos registros de ensaios clínicos da Biblioteca Cochrane e do National Institutes of Health, dos EUA, visando a encontrar ensaios sobre a eficácia da fisioterapia respiratória no empiema pleural em crianças, adolescentes ou adultos. Nenhum ensaio sobre o assunto foi encontrado. Os autores concluem que faltam evidências sobre a eficácia da fisioterapia no empiema pleural. Ensaios clínicos são necessários para responder a esta questão.
Occlusal caries diagnosis in permanent teeth: an in vitro study
Authors: Angnes Gisele , Angnes Vivian , Grande Rosa Helena Miranda , Battistella Márcio , Loguercio Alessandro Dourado , Reis Alessandra
Published: April 2006

The reduction in caries prevalence has not occurred uniformly for all dental surfaces. As the occlusal surfaces are still the most likely sites for the development of lesions, new methods of diagnosis are still being evaluated. This study compared a laser fluorescence (LF) system (DIAGNOdent) with the Ekstrand’s visual system for in vitro detection of occlusal caries. A total of 57 extracted molars with macroscopically intact occlusal surfaces were selected. Two-examiners assessed 110 sites by visual inspection (VI) and LF. After ten days from the first measurement, all teeth were re-evaluated through the same methods by each examiner. Caries extension was histologically assessed (X 40). The methods were compared by means of sensitivity, specificity, intra- and inter-examiner reproducibility and area under the ROC curve. The kappa’s test showed good intra- and inter-examiner reproducibility for both methods. VI and LF showed similar sensitivities for both examiners, however, VI showed higher specificities than LF. The overall analysis, as demonstrated by the area under the ROC curve, showed that VI had a better performance than the LF device. It was concluded that the Ekstrand’s visual system is more reliable than the LF device. LF should be considered only as an adjuvant for occlusal caries diagnosis.
Influence of activation modes on diametral tensile strength of dual-curing resin cements
Authors: Fonseca Renata Garcia , Santos Juliana Gomes dos , Adabo Gelson Luis
Published: April 2006

In metallic restorations, the polymerization of dual-curing resin cements depends exclusively on chemical activation. The effect of the lack of photoactivation on the strength of these cements has been rarely studied. This study evaluated the influence of activation modes on the diametral tensile strength (DTS) of dual-curing resin cements. Base and catalyst pastes of Panavia F, Variolink II, Scotchbond Resin Cement, Rely X and Enforce were mixed and inserted into cylindrical metal moulds (4 x 2 mm). Cements were either: 1) not exposed to light (chemical activation = self-cured groups) or 2) photoactivated through mylar strips (chemical and photo-activation = dual-cured groups) (n = 10). After a 24 h storage in 37ºC distilled water, specimens were subjected to compressive load in a testing machine. A self-curing resin cement (Cement-It) and a zinc phosphate cement served as controls. Comparative analyses were performed: 1) between the activation modes for each dual-curing resin cement, using Student’s t test; 2) among the self-cured groups of the dual-curing resin cements and the control groups, using one-way ANOVA and Tukey’s test (alpha = 0.05). The dual-cured groups of Scotchbond Resin Cement (53.3 MPa), Variolink II (48.4 MPa) and Rely X (51.6 MPa) showed higher DTS than that of self-cured groups (44.6, 40.4 and 44.5 MPa respectively) (p < 0.05). For Enforce (48.5 and 47.8 MPa) and Panavia F (44.0 and 43.3 MPa), no significant difference was found between the activation modes (p > 0.05). The self-cured groups of all the dual-curing resin cements presented statistically the same DTS as that of Cement-It (44.1 MPa) (p > 0.05), and higher DTS than that of zinc phosphate (4.2 MPa). Scotchbond Resin Cement, Variolink II and Rely X depended on photoactivation to achieve maximum DTS. In the absence of light, all the dual-curing resin cements presented higher DTS than that of zinc phosphate and statistically the same as that of Cement-It (p > 0.05).
Compressive strength and compressive fatigue limit of conventional and high viscosity posterior resin composites
Authors: Brandão Letícia , Adabo Gelson Luis , Vaz Luís Geraldo , Saad José Roberto Cury
Published: April 2006

The purpose of this study was to compare the compressive strengths and compressive fatigue limits of three posterior composite resins (Filtek P-60, Surefil and Prodigy Condensable) and a universal restorative composite (Z-100). Cylindrical specimens (8 mm in length x 4 mm in diameter) were used. The dynamic test was performed using the staircase method, and the ratio between compressive fatigue limit and compressive resistance was also calculated (n = 15). The compressive strength and compressive fatigue limit data were analyzed by Anova and Tukey’s test. The Z-100 composite demonstrated higher compression strength (307.20 MPa) than Surefil (266.93 MPa) and Prodigy Condensable (222.08 MPa). The resistance of Filtek P-60 (270.44 MPa) was similar to the resistances of Z-100 and Surefil, while Prodigy Condensable presented the lowest compressive strength. In the compressive fatigue limit tests, Filtek P-60 demonstrated a higher value (184.20 MPa) than Prodigy Condensable (155.50 MPa). Surefil (165.74 MPa) and Z-100 (161.22 MPa) presented limits similar to those of Filtek P-60 and Prodigy Condensable. The compressive fatigue limit/compressive strength ratio was 70.01% for Prodigy Condensable, 68.11% for Filtek P-60, 62.09% for Surefil and 52.48% for Z-100. It was concluded that the Z-100 universal composite was more sensitive to the dynamic test than the high viscosity materials.
Single-Point Mooring System for an Offshore LNG Import Terminal
Authors: Krekel M. H. , Leeuwenburgh R. , Bishop W. M. , Davis J. F.
Published: April 2006

This paper describes the conceptual design of an offshore liquidified natural gas (LNG) import terminal based on the "Bishop Process," sited on Vermilion block 179, offshore Louisiana. The Bishop Process comprises direct regasification of LNG in the dense phase and storage of the gas thus produced in salt caverns. (For conversion factors of units commonly used with LNG, please refer to Table 1.) The operating principles of this process are discussed, as well as the design considerations for the regas, storage, and send-out facilities. The single-point mooring (SPM) system for the offloading of LNG carriers is described, as well as the verification process thereof. The foreseen marine operations at the terminal are explained, and the work done confirms the technical and economical feasibility of the concept.
Effect of GOR, Temperature, and Initial Water Saturation on Solution-Gas Drive in Heavy-Oil Reservoirs
Authors: Tang G.-Q. , Firoozabadi A.
Published: April 2006

We have carried out an extensive set of tests on solution-gas drive for a heavy oil to study the effects of initial water saturation, temperature, and gas-oil ratio (GOR). The viscosity and the API gravity of the stock-tank oil from Hamaca field (in Venezuela) used in our tests are 560,000 cp (at 24°C) and 8.7, respectively. The solution-gas drive tests were conducted using live oils with solution GOR of 6.5, 9.0, and 12.2 (vol/vol at standard conditions). In two tests, initial water saturations of 4.0 and 5.2% were established. Five tests were conducted at a temperature of 35°C; one test was conducted at 46°C. The duration for each test was approximately 3 months. The following conclusions are drawn based on the results from all the tests. Initial water saturation decreases gas-bubble density. The recovery efficiency decreases because of an increase in gas mobility with increase in initial water saturation. As the temperature increases from 35 to 46°C, the gas relative permeability increases one order of magnitude, which in turn results in a reduction of recovery efficiency. The temperature effect on recovery is in agreement with our previous work with temperature increase from 24 to 35°C. Increase in solution GOR has a significant effect on the gas-bubble nucleation process, mainly because of change in interfacial tension. For all the tests conducted, the oil recovery by solution-gas drive at test termination was approximately 16% and higher.
A Comparison of Techniques for Coupling Porous Flow and Geomechanics
Authors: Dean R. H. , Gai X. , Stone C. M. , Minkoff S. E.
Published: April 2006

This paper compares three techniques for coupling multiphase porous flow and geomechanics. Sample simulations are presented to highlight the similarities and differences in the techniques. One technique uses an explicit algorithm to couple porous flow and displacements in which flow calculations are performed every timestep and displacements are calculated only during selected timesteps. A second technique uses an iteratively coupled algorithm in which flow calculations and displacement calculations are performed sequentially for the nonlinear iterations during each timestep. The third technique uses a fully coupled approach in which the program's linear solver must solve simultaneously for fluid flow variables and displacement variables. The techniques for coupling porous flow with displacements are described and comparison problems are presented for single-phase and three-phase flow problems involving poroelastic deformations. All problems in this paper are described in detail, so the results presented here may be used for comparison with other geomechanical/porous-flow simulators.
An Experimental Study at an Abu Dhabi Reservoir of Asphaltene Precipitation Caused By Gas Injection
Authors: Negahban S. , Bahamaish J. N. M. , Joshi N. , Nighswander J. , Jamaluddin A. K. M.
Published: April 2006

This paper discusses experimental work associated with the evaluation of asphaltene precipitation for a field in Abu Dhabi, UAE. This reservoir is in the early stages of development and will be put on production using a combination of gas-, water-, and water-alternating-gas- (WAG) injection schemes in early 2006. The field has not shown operational problems resulting from asphaltene precipitation during primary production.

Laboratory experiments using the transmittance of an optimized laser light in the near-infrared (NIR) wavelength (≈1600 nm) were used to first confirm the stability of asphaltene in the reservoir fluid. Two cases covering the expected extremes in terms of the field gas/oil ratio (GOR) were evaluated. Isothermal depressurization tests were also conducted at reservoir, wellhead, and separator temperatures (250, 190, and 130°C, respectively).

Several additional light-transmittance experiments were conducted to evaluate the asphaltene-instability regions resulting from reservoir-fluid contact with various concentrations of rich gas and carbon dioxide (CO2). Measurements using high-pressure filtration were also collected to quantify the bulk precipitation of asphaltene with various molar concentrations of gas.

Finally, tests were conducted using state-of-the-art technologies to evaluate the consistency of the initial NIR runs. These technologies involved the use of a spectral-analysis system (SAS) to evaluate asphaltene-particle size and growth rate and high-pressure microscopy (HPM) images to visually confirm the measurements.

Results indicated that rich hydrocarbon gas in contact with reservoir fluid destabilizes asphaltene. The amount of the bulk precipitation increased with higher concentrations of rich gas in the reservoir fluid. Particle sizes were estimated to be in the range of 0.5 to 1 µm. The effect of CO2 was found to be less severe with regard to asphaltene instability.
Correcting for Frictional Pressure Drop in Horizontal-Well Inflow-Performance Relationships
Authors: Archer R. A. , Agbongiator E. O.
Published: April 2006

This paper presents the development of a correlation that corrects for error in single-phase horizontal-well productivity calculations made by neglecting frictional pressure drop in the wellbore. Frictional pressure drop within the wellbore is frequently a controlling factor on the performance of long horizontal wells. Frictional pressure drop could be especially significant in wells completed with screens and slotted liners. This pressure loss is neglected in traditional inflow-performance (IPR) calculations, such as those developed by S.D. Joshi and by D.K. Babu and A.S. Odeh. This study develops a correction that can be added to these analytical IPR relationships to account for friction. This correction is based on a dimensionless group that combines well and reservoir information. It is easy to evaluate and can be readily used in nodal analysis.

The correction was developed on the basis of more than 5,000 finite-difference-simulation runs, using a simulator with the capability to model wellbore friction. These runs spanned a wide range of well and reservoir parameters. The results are presented in terms of productivity errors (PEs); that is, the flow rate without friction minus the flow rate when friction is included in the model, divided by the flow rate reported without friction. The study found PEs as high as 90% in some cases (usually long wells with a small wellbore radius). These errors could lead to poor decisions on field development and production facilities. This paper presents a simple way to improve well-productivity predictions without requiring a reservoir-simulation model to take account of frictional pressure drops in the wellbore.
Single-Phase Model for Electric Submersible Pump (ESP) Head Performance
Authors: Sun Datong , Prado Mauricio
Published: April 2006

This paper presents a new incompressible single-phase model for ESP head performance. Sachdeva (1988, 1994) and Cooper and Bosch (1966) developed models for ESP channels and for inducers, respectively. The model presented in this paper is based on 1D approximation along an ESP channel. The new derived pressure ordinary differential equation (ODE) for frictionless incompressible flow (Bird 1960) is consistent with the pump Euler equation. New models for pump frictional and shock losses have been proposed. Finally, a comparison between the predicted pump performance and the pump performances derived from the affinity law for different rotational speeds is presented. The single-phase model can predict ESP performance under different fluid viscosities and also is the basis of a gas/liquid model for ESP head performance.
Evaluation of Special Enzymes as a Means To Remove Formation Damage Induced by Drill-in Fluids in Horizontal Gas Wells in Tight Reservoirs
Authors: Siddiqui M. A. , Nasr-El-Din H. A.
Published: April 2006

Drill-in fluids contain biopolymers such as xanthan gum, cellulose, and/or starch, along with bridging agents like sized calcium carbonate particles. These polymers are used to enhance the carrying capacity of the mud and to form a filter cake to minimize leakoff of the drilling fluids into the formation.

Proper removal of drilling-mud filter cake is essential to minimize formation damage. The damage becomes more intense in tight formations, especially in horizontal gas wells in which the drawdown is not high enough to dislodge the filter cake. Another source of damage is the mud filtrate where fines migration and water blockage can occur in tight formations, especially in sandstone reservoirs.

A thorough laboratory investigation of formation damage induced by drill-in fluids (water-based) was conducted. A mini-flow loop was used to assess formation damage induced by polymers present in the drill-in fluid. Various cleaning fluids were examined and their effectiveness in removing the filter cake was determined. These fluids included acidic brines, surfactants, mutual solvents, specific enzymes, and combinations of these fluids. The retained permeability of reservoir cores was determined for each cleaning system. This paper presents results obtained from the laboratory and recommendations made to remove drilling-mud filter cake from horizontal gas wells in a deep sandstone-gas reservoir.
Upscaling and 3D Streamline Screening of Several Multimillion-Cell Earth Models for Flow Simulation
Authors: Samantray Ajay K. , Dashti Qasem M. , Ma Eddie D. C. , Kumar Pradeep S.
Published: April 2006

Nine multimillion-cell geostatistical earth models of the Marrat reservoir in Magwa field, Kuwait, were upscaled for streamline (SL) screening and finite-difference (FD) flow simulation.

The scaleup strategy consisted of (1) maintaining square areal blocks over the oil column, (2) upscaling to the largest areal-block size (200×200 m) compatible with 125-acre well spacing, (3) up-scaling to less than 1 million gridblocks for SL screening, and (4) upscaling to less than 250,000 gridblocks for FD flow simulation. Chevron's in-house scaleup software program, SCP, was used for scaleup. SCP employs a single-phase flow-based process for upscaling nonuniform 3D grids. Several iterations of scaleup were made to optimize the result.

Sensitivity tests suggest that a uniform scaled-up grid overestimates breakthrough time compared to the fine model, and the post-breakthrough fractional flow also remains higher than in the fine model. However, preserving high-flow-rate layers in a nonuniform scaled-up model was key to matching the front-tracking behavior of the fine model. The scaled-up model was coarsened in areas of low average layer flow because less refinement is needed in these areas to still match the flow behavior of the fine model. The final ratio of pre- to post-scaleup grid sizes was 6:1 for SL and 21:1 for FD simulation.

Several checks were made to verify the accuracy of scaleup. These include comparison of pre- and post-scaleup fractional-flow curves in terms of breakthrough time and post-breakthrough curve shape, cross-sectional permeabilities, global porosity histograms, porosity/permeability clouds, visual comparison of heterogeneity, and earth-model and scaled-up volumetrics.

The scaled-up models were screened using the 3D SL technique. The results helped in bracketing the flow behavior of different earth models and evaluating the model that better tracks the historical performance data. By initiating the full-field history-matching process with the geologic model that most closely matched the field performance in the screening stage, the amount of history matching was minimized, and the time and effort required were reduced. The application of unrealistic changes to the geologic model to match production history was also avoided.

The study suggests that single realizations of "best-guess" geo-statistical models are not guaranteed to offer the best history match and performance prediction. Multiple earth models must be built to capture the range of heterogeneity and assess its impact on reservoir flow behavior.
An Analytical Model for Production Decline-Curve Analysis in Naturally Fractured Reservoirs
Authors: Li Kewen , Horne Roland N.
Published: April 2006

Decline-curve-analysis models are used frequently but still have many limitations. Approaches of decline-curve analysis used for naturally fractured reservoirs developed by waterflooding have been few. To this end, a decline-analysis model derived on the basis of fluid-flow mechanisms was proposed and used to analyze the oil-production data from naturally fractured reservoirs developed by waterflooding. Relative permeability and capillary pressure were included in this model. The model reveals a linear relationship between the oil-production rate and the reciprocal of the oil recovery or the accumulated oil production. We applied the model to the oil-production data from different types of reservoirs and found a linear relationship between the production rate and the reciprocal of the oil recovery as foreseen by the model, especially at the late period of production. The values of maximum oil recovery for the example reservoirs were evaluated with the parameters determined from the linear relationship. An analytical oil-recovery model was also proposed. The results showed that the analytical model could match the oil-production data satisfactorily. We also demonstrated that the frequently used nonlinear type curves could be transformed to linear relationships in a log-log plot. This may facilitate the production-decline analysis. Finally, the analytical model was compared with conventional models.
Self-Learning Reservoir Management
Authors: Saputelli L. , Nikolaou M. , Economides M. J.
Published: April 2006

In this work, we present an industrial automation framework for control and optimization of hydrocarbon-producing fields while satisfying business and physical constraints. The all-encompassing reservoir-management problem is decomposed into a hierarchy of decision-making problems at different time scales.

We exemplify the proposed approach through a case study on a multiple-layer reservoir with a classical waterflood problem, in which a numerical reservoir model is used as a virtual field. A model-predictive control (MPC) strategy is used to regulate well and field instrumentation at economically optimal set points determined by an overlying supervisory control level. The study demonstrates significant reduction in water-handling costs and increased oil recovery.

This work is a starting point for further development in automatic intelligent reservoir technologies, which capitalize on the abilities of permanent instrumented wells and remotely activated downhole completions.
Pt. McIntyre: A Case Study of Gas Enrichment Above MME
Authors: Moulds T. P. , McGuire P. L. , Jerauld G. R. , Lee S.-T. , Solano R.
Published: April 2006

Pt. McIntyre field operates an enriched-gas-injection scheme that displaces oil in a multicontact miscible (MCM) displacement achieved through a combined condensing/vaporizing (C/V) mechanism. A range of miscible-injectant (MI) compositions, varying from the minimum miscible enrichment (MME) to substantially above the MME, is available to the project. Field-scale numerical-simulation studies for the Pt. McIntyre field show that incremental oil recovery is nearly doubled when using the richest available MI composition.

At the MME, dispersion can act to substantially reduce oil recovery by reducing the concentration of enriching components in the near-miscible zone. Increasing enrichment above the MME compensates for this action. Accurate predictions of incremental oil depend on the numerical dispersion in a simulator being able to match the impact of physical dispersion. We show how compositional core data from an MI-swept interval provide confirmation of the impact of dispersion at field scale and demonstrate the appropriateness of the simulation model. The benefit of enrichment appears to be robust to the variation of reservoir description found at Pt. McIntyre and to whether the MI application targets incremental oil through liquid- or vapor-phase recovery.

Previous studies into MI enrichment have reported that for a four-component system, the mechanism changes from C/V to purely condensing as the enrichment level approaches first-contact miscibility (FCM). We show that with the addition of a small amount of heavy component, the C/V behavior is retained with increasing enrichment until transition into FCM. This makes it unlikely that a transition to a purely condensing mechanism will occur in real reservoirs.
Integration of Seismic Anisotropy and Reservoir-Performance Data for Characterization of Naturally Fractured Reservoirs Using Discrete-Feature-Network Models
Authors: Will Robert , Archer Rosalind , Dershowitz Bill
Published: April 2006

This paper proposes a method for quantitative integration of seismic (elastic) anisotropy attributes with reservoir-performance data as an aid in characterizing systems of natural fractures in hydrocarbon reservoirs. This method is demonstrated through application to history matching of reservoir performance using synthetic test cases.

Discrete-feature-network (DFN) modeling1 is a powerful tool for developing fieldwide stochastic realizations of fracture networks in petroleum reservoirs. Such models are typically well conditioned in the vicinity of the wellbore through incorporation of core data, borehole imagery, and pressure-transient data. Model uncertainty generally increases with distance from the borehole. Three-dimensional seismic data provide uncalibrated information throughout the interwell space. Some elementary seismic attributes such as horizon curvature and impedance anomalies have been used to guide estimates of fracture trend and intensity (fracture area per unit volume) in DFN modeling2 through geostatistical calibration with borehole and other data. However, these attributes often provide only weak statistical correlation with fracture-system characteristics.

The presence of a system of natural fractures in a reservoir induces elastic anisotropy that can be observed in seismic data. Elastic attributes such as azimuthally dependent normal moveout velocity (ANMO), reflection amplitude vs. azimuth (AVAZ), and shear-wave birefringence can be inverted from 3D-seismic data. Anisotropic elastic theory provides physical relationships among these attributes and fracture-system properties such as trend and intensity. Effective-elastic-media models allow forward modeling of elastic properties for fractured media.

A technique has been developed in which both reservoirperformance data and seismic anisotropic attributes are used in an objective function for gradient-based optimization of selected fracture-system parameters. The proposed integration method involves parallel workflows for effective elastic and effective permeability media modeling from an initial DFN estimate of the fracture system. The objective function is minimized through systematic updates of selected fracture-population parameters. Synthetic data cases show that 3D-seismic attributes contribute significantly to the reduction of ambiguity in estimates of fracture-system characteristics in the interwell rock mass. The method will benefit enhanced-oil-recovery (EOR) program planning and management, optimization of horizontal-well trajectory and completion design, and borehole-stability studies.
Completion and Well-Performance Results, Genesis Field, Deepwater Gulf of Mexico
Authors: Pourciau Robert D. , Fisk Jill H. , Descant Frank J. , Waltman R. Bart
Published: April 2006

The Genesis project was Chevron Corp.'s first Gulf of Mexico deepwater development project and the first industry project to use spar technology for drilling, completion, and production operations.1,2 This paper discusses the unique results and lessons learned through the first 4 years of the Genesis project in the areas of integrated teams, organizational learning, spar operations, completion practices, well performance, and reservoir management.
Natural Polymer-Based Compositions Designed for Use in Conformance Gel Systems
Authors: Reddy B. R. , Eoff Larry , Dalrymple E. Dwyann , Brown David
Published: April 2006

This article describes a crosslinking material derived from natural sources that can be used with a variety of polymers over a broad temperature range to produce gels for conformance applications. Delayed crosslinked polymer systems have been used for many years in conformance applications. For the past decade, the most widely used system has been based on chromium (+3) crosslinked polyacrylamide. Organic crosslinkers, such as phenol/formaldehyde and polyethyleneimine (PEI), have also been used with a variety of polymers. However, these systems are being scrutinized by regulatory agencies and have now been scheduled for phase-out in some countries. Because of these issues, a single, environmentally friendly crosslinker that could be used with a variety of polymers over a broad temperature range was selected for study.

This article details the laboratory development of an environmentally friendly, natural polyamine crosslinker system, namely chitosan. This crosslinker can be used with a variety of polymers, such as polyacrylamide, AMPS/acrylamide (AMPS/AA), or alkylacrylate polymers. Gels ranging from stiff and "ringing" type to "lipping" have been obtained. Additionally, this article summarizes results from recent efforts targeted toward designing chitosan-basedgel compositions with improved environmental rating for potential field use. These efforts included using chitosan as the base polymer in combination with asynthetic polymeric crosslinker, as well as developing gels derived completelyfrom natural polymers.
The Use of Lightweight Cement Slurries and Downhole Chokes on Air-Drilled Wells
Authors: Brown Devin , Ferg Thomas
Published: April 2006

The success of a primary cement job is often measured according to effective zonal isolation, achieving the designed top of cement, and avoidance of remedial cementing. In the San Juan and Rio Arriba counties of New Mexico, many Mesa Verde and Dakota wells are air-drilled because the Mesa Verde formation is subnormally pressured and naturally fractured. This combination makes the Mesa Verde easy to hydraulically fracture during normal drilling and cementing operations. Therefore, meeting the primary-cement-job success criteria is particularly challenging.

Cementing of casing within an air-drilled wellbore allows the slurry to free fall. Cement free fall can cause severe surge pressures at the bottom of the hole, leading to hydraulic fracture initiation and loss of lift. Theuse of a downhole choke (DHC) can be employed to prevent these processes from occurring.

Because mud filter cake does not exist in an air-drilled hole, the lead water spacer and cement must wet the casing and wellbore rock surfaces. Loss of the lead water spacer, in conjunction with cement water loss, can produce dehydration of the cement column, leading to an increase incement viscosity and equivalent circulating density. Careful control of cement-free water and fluid loss are required to prevent this from occurring. Further more, placing cement across targeted completion intervals that have low fracture gradients requires the use of ahigh-compressive-strength, low-density cement that is competent and capable of maintaining zonal isolation during the completion and production phases of well construction.

This paper will outline the evolution of the cementing practices used forthe Mesa Verde and Dakota wells drilled in the 29-6 Unit (T29N−R6W, New Mexico) from 1998 to 2002. It will illustrate how cementing changes enabled the primary cementing to be successfully completed in a single stage instead of two, which has translated into cost savings for both the drilling and completion phases of a well. The impact of using a DHC for the pumping and placement of these primary cement jobs will be illustrated and discussed. The function of the cement additives on slurry properties will also be discussed as they pertain to these cement jobs.
The Small-Drillhole Minipermeameter Probe for In-Situ Permeability Measurement
Authors: Dinwiddie C. L.
Published: April 2006

Laboratory measurement of permeability using a Hassler cell is the industry standard; however, consistently removing undisturbed rock samples from friable outcrops is difficult. Although various conventional surface-sealing mini-permeameters are developed as an alternative for permeability measurement, these devices generally suffer from difficulties in maintaining optimal forces on the tip seal when dealing with outcrop irregularities in the field; outcrop weathering is also problematic. Because a reliable field method is needed for studies of friable geological units, this paper presents an innovative technique for measuring permeability in situ. The design of the small-drillhole minipermeameter probe is discussed, as well as the accompanying analytical technique and the size and shape of the instrument's averaging volume. Small-diameter holes [i.e., 1.8 cm (0.7 in.)] are drilled into an outcrop with a masonry drill, followed by drillhole vacuuming, probe insertion, seal expansion, gas injection, and calculation of the intrinsic permeability through measurement of the injection pressure, gas-flow rate, and knowledge of the system geometry. Advantages of this approach include access to a nonweathered surface, an operator-independent sealing mechanism around the air-injection zone, and the potential for permeability measurement at multiple depths below an outcrop surface. To date, data have been collected from four diverse porous media: upper and lower shoreface sandstone (Escalante, Utah), saprolitic soils (Clemson, South Carolina), nonwelded and sintered ignimbrite (Bishop, California), and fluvially reworked tuffaceous sedimentary rock (Bishop, California). The probe has proved durable and robust, with a single probe sufficient for making thousands of measurements in a variety of environments. Data quality supports the conclusion that the drillhole probe is a practical field instrument.
In-Situ Diagnosis of Formation Characteristics in Horizontal Wells
Authors: Cui H. , Dong Y. , Kalita R. , Sinha S. , Jalali Y.
Published: April 2006

A method is presented for estimating the distribution of a parameter related to the productivity index along the length of a liner-completed horizontal well, using measurements of well flowing pressure at multiple points along the path of flow in the wellbore. This is the concept of near-wellbore diagnosis with multipoint pressure measurements, which in principle can be made with fiberoptic sensors. The deployment mechanism of the sensors is not modeled in this study, although the temperature version of such sensors has been deployed in horizontal wells on an extended-tailpipe or stinger completion. (The temperature sensors also have been deployed in horizontal wells with sand-screen completions, in direct contact with the formation, but that configuration is not investigated in this study.)

The parameter that is estimated is known in reservoirsimulation terminology as the connection factor (CF), which represents the hydraulic coupling or connectivity between the reservoir and the wellbore (between formation gridblocks and well segments). Parameter CF has units of md-ft, similar to flow capacity, or productivity index multiplied by viscosity. Specifically, the parameter is directly proportional to the geometric mean of the permeability perpendicular to the horizontal axis of the well and is inversely related to skin. No attempts are made in this study to estimate these parameters individually, which may require recourse to other methods of well diagnosis (e.g., dynamic formation testing, transient analysis, and production logging).

The method applies to flow under constant-rate conditions and yields estimates of the CF, which represents the quality of the formation in the vicinity of the well and the integrity of the completion along the well trajectory.

The quality of the inversion is determined by the spatial density and accuracy of the multipoint measurements. Inversion quality also depends on knowledge of the wellbore hydraulic characteristics and the relative permeability characteristics of the formation. The basic configuration investigated in this study consists of a five-node pressure array in a 2,000-ft horizontal well experiencing a total pressure drop of approximately 60 psi when produced at 10,000 STB/D. A reasonable estimate of the distribution of the parametric group CF is obtained even when allowing for measurement drift and errors in liner roughness and relative permeability exponent. Also, the inversion can be rendered insensitive to knowledge of the far-field permeability through a scaling technique. Therefore, good estimates of the near-wellbore CF profile can be obtained with uncertain knowledge of the reservoir permeability field. This is important because the technique can be applied not only to early-time but also to late-time data. The application of the multipoint pressure method is illustrated through a series of examples, and its potential for near-wellbore formation evaluation for horizontal wells is described.