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Previous issue date: 2009-04-30 / Several problems related to the loss of hydraulic seal in oilwells, causing gas migration and/or contamination of the production zone by water, have been reported. The loss of the hydraulic seal is a consequence of cracks which can
be occasioned either by the invasion of gas during the wait on cement or by the expansion of the casing causing the fracture of the cement sheath. In case of the pressure of the formation is higher than the pressure in the annulus, gas
can migrate into the slurry and form microannulus, which are channels where gas migrates after the cement is set. Cracks can be also occasioned by the fracture of the cement sheath when it does not withstand the thermal and dynamic loads. In reservoirs where the oil is heavy, steam water injection
operation is required in order to get the oil flowing. This operation increases the temperature of the casing, and then it expands and causes the fracture of the cement sheath in the annulus. When the failures on the cement are detected,
remedial cementing is required, which raise costs caused by the interventions. Once the use of cement in the construction civil sector is older than its use in the petroleum sector, it is common to bring technologies and solutions from the civil construction and apply them on the petroleum area. In this context, vermiculite, a mineral-clay widely encountered in Brazil, has been used, on its exfoliated form, in the civil construction, especially on the manufacture of lights and fireproof concretes with excellent thermal and acoustical properties. It has already been reported in scientific journals, studies of the addition of exfoliated vermiculite in Portland cements revealing good properties related to oilwell
cementing operations. Thus, this study aimed to study the rheological behavior, thickening time, stability and compressive strength of the slurries made of Portland cement and exfoliated vermiculite in 5 different compositions, at room
temperature and heated. The results showed that the compressive strength decreased with the addition of exfoliated vermiculite, however the values are still allowed for oiwell cementing operations. The thickening time of the slurry
with no exfoliated vermiculite was 120 min and the thickening time of the slurry with 12 % of exfoliated vermiculite was 98 min. The stability and the rheological behavior of the slurries revealed that the exfoliated vermiculite absorbed water
and therefore increased the viscosity of the slurries, even though increasing the factor cement-water. The stability experiment carried out at 133 ?F showed that, there was neither sedimentation nor reduction of the volume of the cement for the slurry with 12 % of exfoliated vermiculite. Thus, the addition of exfoliated vermiculite accelerates the set time of the cement and gives it a small shrinkage
during the wait on cement, which are important to prevent gas migration / Muitos problemas relacionados ? perda do isolamento hidr?ulico em po?os de petr?leo, causando migra??o de g?s e contamina??o da zona produtora por migra??o de ?gua, t?m sido reportados. A perda do isolamento hidr?ulico ?
conseq??ncia de trincas que por sua vez s?o conseq??ncias de uma cimenta??o mal feita, onde houve invas?o de g?s durante a pega da pasta gerando trincas tamb?m chamadas de microanulares que s?o os caminhos por onde a migra??o de g?s ocorre. Essas trincas tamb?m s?o ocasionadas pela
fratura do cimento quando este n?o suporta as cargas t?rmicas e din?micas, as quais o cimento ? submetido durante sua vida. Em reservat?rios onde o ?leo encontrado ? bastante viscoso, opera??es de inje??o de vapor de ?gua s?o
requeridas a fim de facilitar o escoamento do ?leo. Essa opera??o aumenta a temperatura da malha de po?os, fazendo com que o revestimento dilate e frature o cimento no anular, ocasionando a perda do isolamento hidr?ulico. Uma vez detectada falhas no isolamento hidr?ulico, opera??es de corre??o s?o requeridas o que acaba gerando custos, perda de tempo com a interven??o e lucro cessante. Como o setor de constru??o civil trabalha com cimento a muito mais tempo que o setor de petr?leo, ? comum lan?ar-se m?o de tecnologias e solu??es apresentadas na constru??o e aplicar com os devidos ajustes no ramo do petr?leo. Nesse contexto, a vermiculita, um argilomineral encontrado em abund?ncia no Brasil, tem sido aplicado, na sua forma expandida, na
constru??o civil para confec??o de concretos leves, resistentes a fogo e com excelentes propriedades de isolamento t?rmico e ac?stico. J? tem sido reportado em revistas cient?ficas, estudos de sua adi??o em cimento portland com boas propriedades relacionadas ? cimenta??o de po?os de petr?leo. Dessa forma o presente trabalho objetivou estudar o comportamento reol?gico, tempo de pega e a resist?ncia a compress?o de pastas com vermiculita
expandida e cimento portland classe especial em quatro composi??es diferentes, fazendo um comparativo com as propriedades existentes da pasta padr?o contendo apenas cimento portland e ?gua, em duas temperaturas, ambiente e aquecida. Os resultados mostraram que a resist?ncia ?
compress?o dos corpos de prova diminuiu com o aumento da concentra??o de vermiculita, por?m ainda dentro da faixa permitida para cimenta??o de po?os de petr?leo. Os ensaios de consistometria indicaram que o tempo de pega para
a pasta padr?o foi de 120 min, enquanto que para a pasta com 12% de vermiculita expandida foi de 98 min. Os ensaios de estabilidade e a avalia??o do comportamento reol?gico das pastas mostraram que a vermiculita expandida por absorver ?gua, aumenta a viscosidade da pasta, mesmo aumentando o fator ?gua-cimento. O ensaio de estabilidade realizado ? 133 ?F mostrou que n?o houve rebaixamento e nem sedimenta??o para a pasta com 12% de vermiculita expandida. Logo a adi??o de vermiculita expandida ? pasta cimentante favorece a cura r?pida e a baixa retra??o do volume da pasta durante a pega, importantes para evitar migra??o de g?s
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/12683 |
| Date | 30 April 2009 |
| Creators | Lima, Fernando Antonio de Melo |
| Contributors | CPF:06117988320, http://lattes.cnpq.br/3318871716111536, Melo, Marcus Ant?nio de Freitas, CPF:04514998320, http://lattes.cnpq.br/5840621182000517, Martinelli, Ant?nio Eduardo, CPF:15724520800, http://lattes.cnpq.br/0022988322449627, Barros, Joana Maria de Farias, CPF:85239658404, http://lattes.cnpq.br/1016070459137884, Melo, Dulce Maria de Ara?jo |
| Publisher | Universidade Federal do Rio Grande do Norte, Programa de P?s-Gradua??o em Ci?ncia e Engenharia de Materiais, UFRN, BR, Processamento de Materiais a partir do P?; Pol?meros e Comp?sitos; Processamento de Materiais a part |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Format | application/pdf |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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