677 research outputs found

    Use of a transient model for studying kick migration velocities and build-up pressures in a closed well

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    The objective of the paper is to show that using pressure build-up curves for estimating kick migration velocities can be unreliable. This will be demonstrated by using a transient flow model where different flow patterns including suspended gas are considered. Suspended gas will occur in Non-Newtonian drilling fluids. This can also be the reason why there is reported large discrepancies in literature about what the gas kick migration velocities can be. A transient flow model based on the drift flux model supplemented with a gas slip relation will be used. The model will be solved by an explicit numerical scheme where numerical diffusion has been reduced. Different flow patterns are included i.e. suspended gas, bubble flow, slug flow and transition to one-phase gas. Kick migration in a closed well will be studied to study how pressure build-ups evolve. A sensitivity analysis will be performed varying kick sizes, suspension limits and changing the transition intervals between the flow patterns. It is seen in literature that the slope of the pressure build-up for a migrating kick in a closed well has been used for estimating what the kick velocity is. It has been reported earlier that this can be an unreliable approach. In the simulation study, it is clearly demonstrated that the suspension effect will have a significant impact of reducing the slopes of the pressure build-ups from the start of the kick onset. In some severe cases, the pressure builds up but then it reaches a stable pressure quite early. In these cases, the kick has stopped migrating in the well. However, in the cases where the kicks are still migrating, it seems that the bulk of the kick moves at the same velocity even though the degree of suspension is varied and gives different slopes for the pressure build-up. Hence, it seems impossible to deduce a unique gas velocity from different pressure build-up slopes. However, abrupt changes in the slope of the pressure build-up indicate flow pattern transitions.acceptedVersio

    Otimização do processo de obtenção e tratamento de dados de clientes telecontados

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    A conjuntura energ√©tica global espelha o enorme desafio de responder √† crescente necessidade energ√©tica com a utiliza√ß√£o crescente de fontes de energia renov√°veis. Tendo em conta a depend√™ncia atual em fontes de energia tradicionais, e considerando a emiss√£o reduzida de poluentes e o baixo custo do g√°s natural, o papel desta fonte de energia √© fundamental na transi√ß√£o para um cen√°rio energ√©tico mais limpo. Em Portugal, o sistema de g√°s natural √© recente e a tend√™ncia √© para um aumento de consumo. Decorrente da liberaliza√ß√£o do mercado de g√°s natural, face √† necessidade de disponibilizar informa√ß√£o aos consumidores e atingir uma melhor rela√ß√£o com os consumos, surgiram os sistemas de telecontagem. Estes sistemas de medi√ß√£o s√£o capazes de integrar a recolha, processamento e transmiss√£o de dados, e gerar um vasto conjunto de informa√ß√£o √ļtil a an√°lises. Com a quantidade de informa√ß√£o gerada, o presente trabalho pretende otimizar o processo de obten√ß√£o e tratamento de dados de clientes telecontados de uma organiza√ß√£o, promovendo a monitoriza√ß√£o e a automatiza√ß√£o da decis√£o do processo para efeitos de an√°lise e fatura√ß√£o. Inicialmente, o estudo procurava analisar o processo original e caracterizar o mesmo no que diz respeito √†s inefici√™ncias das regras de valida√ß√£o implementadas e √†s falhas globais do processo. De seguida, foi necess√°rio otimizar o fluxo de dados, e desenvolver e implementar uma solu√ß√£o que permitisse realizar um tratamento di√°rio e constante aos dados, com base em condi√ß√Ķes favor√°veis √† disponibiliza√ß√£o de relat√≥rios auxiliares ao processo de decis√£o. Primeiramente, de forma a cumprir com o objetivo inicial, foi realizada uma contextualiza√ß√£o √† telecontagem e de toda a arquitetura do sistema de medi√ß√£o que lhe √© inerente, de forma a compreender e analisar o processo original. De seguida, derivado do estudo realizado a processos de tratamento de dados, regras impostas e metodologias presentes na ind√ļstria, o diagrama de fluxo foi elaborado e a solu√ß√£o para a ferramenta estabelecida em Microsoft Excel¬©, com recurso √† linguagem Visual Basic for Applications (VBA). Com o desenvolvimento de algoritmos capazes de validar e estimar os dados, foi poss√≠vel identificar clientes validados e gerar relat√≥rios que fomentaram a fatura√ß√£o com base em consumos reais e antecipa√ß√£o de anomalias. Com o prop√≥sito de perceber o sucesso da implementa√ß√£o da ferramenta foi calculado o r√°cio entre os clientes validados e invalidados. O r√°cio m√°ximo de 18,42, atingido com o processo atual, comparativamente ao r√°cio m√°ximo de 3,13, atingido com o processo anterior, permite concluir que o processo de obten√ß√£o e tratamento de dados foi otimizado.The global energy situation reflects the enormous challenge of meeting the growing energy need with the increased use of renewable energy sources. Given the current dependence on traditional energy sources, and considering the reduced emission of pollutants and the low cost of natural gas, the role of this energy source is crucial in the transition to a cleaner energy scenario. In Portugal, the natural gas system is recent and the trend is towards an increase in consumption. As a result of the liberalisation of the natural gas market, given the need to provide information to consumers and achieve a better relationship with consumption, telemetering systems have emerged. These measurement systems are capable of integrating the collection, processing and transmission of data, and generate a vast set of information useful for analysis. With the amount of generated information, this work aims to optimise the process of obtaining and processing data from telemetry customers of an organisation, promoting the monitoring and automation of the process decision for the purposes of analysis and invoicing. Initially, the study sought to analyse the original process and characterise it regarding the inefficiencies of the implemented validation rules and the overall process failures. It was then necessary to optimise the data flow, and to develop and implement a solution that would enable the daily and constant processing of the data, based on conditions favourable to the availability of reports auxiliary to the decision-making process. Firstly, in order to meet the initial objective, the telemetering and the entire architecture of the measurement system that is inherent to it were contextualised, in order to understand and analyse the original process. Then, derived from the study carried out on data treatment processes, imposed rules and methodologies present in the industry, the flow diagram was prepared and the solution for the tool was established in Microsoft Excel¬©, using the Visual Basic for Applications (VBA) language. With the development of algorithms capable of validating and estimating the data, it was possible to identify validated customers and generate reports that promoted invoicing based on real consumption and anticipation of anomalies. In order to understand the success of the implementation of the tool, the ratio between validated and invalidated customers was calculated. The maximum ratio of 18.42, reached with the current process, compared to the maximum ratio of 3.13, reached with the previous process, allows concluding that the process of obtaining and processing data was optimised

    Genes coding for enterotoxins and verotoxins in porcine Escherichia coli strains belonging to different O:K:H serotypes: Relationship with toxic phenotypes

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    Seventy-four E. coli strains isolated from piglets with diarrhea or edema disease in Spain were serotyped and examined for production of heat-labile (LT) and heat-stable (ST) enterotoxins (LT-I, LT-II, STaH, STaP, and STb) and verotoxins (VT1, VT2, and VT2v VTe) by phenotypic (Vero cell assay and infant mouse test) and genotypic (colony hybridization and PCR) methods. In general, an excellent correlation was found between the results obtained with a PCR approach and those determined with biological assays. DNA probes used in the hybridization also showed a very good agreement with phenotypic results, with the exception of a VT1 probe that initially produced 10 false-positive reactions. The gene coding for STb (58 strains) was the most prevalent gene detected by PCR, followed by those coding for STa (46 strains), LT (19 strains), VT2v (11 strains), and VT1 (1 strain). Apparently, in Spain three seropathotypes are predominant: (i) 0149:K91:H10 K88(+) LT-I+ STb+ (ii) 0141:K85ab:H- P987(+) STaP+, and (iii) 0138:K81:H14 or H-STaP+ VT2v(+). We conclude that PCR is a fast, specific, and practical method for the identification of enterotoxin and VT genes in clinical and epidemiological studies.35112958296
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