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Previous issue date: 2015-02-09 / A cimenta??o ? uma das opera??es mais importantes executadas entre as fases de
perfura??o de um po?o. Quando essa cimenta??o n?o ? bem realizada, h? o risco de ocorrer
falhas e fraturas, tanto na forma??o quanto no pr?prio cimento. Quando os reservat?rios
possuem uma baixa profundidade, eles tendem a fraturar mais facilmente, devido ao seu baixo
gradiente de fratura, por isso, a densidade da pasta de cimento ? de suma import?ncia para
equil?brio das press?es, evitando problemas de fraturas. ? ela que vai garantir a estabilidade
das press?es atuantes entre o po?o e a forma??o. Tendo em vista que s?o necess?rias pastas
mais leves para promover o isolamento, sem que haja esse faturamento, ? necess?rio formular
sistemas cimentantes que reduzam a press?o hidrost?tica da coluna de cimento. Para isso, s?o
adicionados, ?s pastas, materiais com fun??es de reduzir a densidade. Portanto, este trabalho
teve como objetivo otimizar formula??es de pastas de cimento de baixa densidade, contendo
bentonita para aplica??o em po?os rasos e com baixo gradiente de fratura, como tamb?m
comparar a efici?ncia do aditivo estendedor bentonita adicionado a estas pastas, atrav?s da
varia??o das densidades e concentra??es e observa??o do comportamento das propriedades
reol?gicas, estabilidade e resist?ncia ? compress?o. As pastas foram formuladas com os
seguintes valores de densidades: 12,0 lb/gal; 12,5 lb/gal; 13,0 lb/gal e 13,5 lb/gal, com
diferentes concentra??es de bentonita (1,0; 2,0; 3,0 e 4,0 %) para cada composi??o. Os
resultados obtidos atrav?s dos testes reol?gicos mostraram que o incremento da concentra??o
de bentonita proporcionou o aumento das part?culas dispersas no meio, provocando o
aumento dos par?metros reol?gicos para todas as densidades. Nos testes de estabilidade os
melhores resultados obtidos foram para densidades mais elevadas, se tornando mais est?veis
com concentra??es a partir de 3 %, n?o apresentando rebaixamento. Nos testes de resist?ncia
? compress?o, a pasta com densidade de 13,5 lb/gal com concentra??o de 4,0% de bentonita
obteve uma maior resist?ncia mec?nica, por?m, muito viscosa, o que pode ser dificultoso para
o bombeamento. Atrav?s das caracteriza??es de difra??o de raios-X (DRX) da bentonita pura
foi observado a presen?a das fases montmonrilonita e quartzo, caracter?sticos dessa argila. No
DRX das pastas de cimento de 13,5 lb/gal foi observado que houve a presen?a de Etringita,
portlandita, silicato de c?lcio e quartzo. Observou-se tamb?m que nas imagens obtidas por
microscopia eletr?nica de varredura (MEV) a pasta de 13,5 lb/gal com 4 % de bentonita
mostrou notoriamente a presen?a de agulhas de etringita, como tamb?m as fases de
portlandita e silicato de c?lcio, produtos da hidrata??o do cimento. Por fim, pode-se
considerar que as pastas que obtiveram melhores resultados, s?o as pastas com densidade de
13,5 lb/gal, com concentra??es de 2,0 % e 3,0 %, por serem mais est?veis e resistentes
mecanicamente, comparadas com as demais com densidades menores. / The cementing is one of the most important operations executed between the stages of drilling
a oil well. When the cementation isn?t well performed, there?s the risk of to occur failures and
fractures, both in formation as in the cement itself. When the reservoirs have low depth, they
tend to fracture more easily, due to his low gradient of fracture, therefore, the density of the
cement slurry is of utmost importance to balance the pressures, avoiding fractures problems.
It?ll ensure the stability of the pressures acting between the oil well and the formation. Having
in mind that are necessary paste more lightweight to promote the insulation, without there
being this billing, is necessary to formulate cementing systems to reduce the hydrostatic
pressure of the cement column. Thereunto, are added to folders, materials with functions to
reduce the density. Therefore, this study had as objective formulations optimize of a cement
slurry of low density containing bentonite for application in shallow oil wells and with low
gradient of fracture, as well as to compare the efficiency of the bentonite extender additive
added to these pastes, by of variations of the density and concentrations and observing of
behavior of the rheological properties, stability and resistance to compression. The pastes
were formulated with the follows density values: 12,0 lb/gal; 12,5 lb/gal; 13,0 lb/gal to 13,5
lb/gal with different concentrations of bentonite (1,0; 2,0; 3,0 and 4,0 %) for each
composition. The results obtained through the rheological tests showed that the increase in the
bentonite concentration afforded the increase in particles dispersed in the middle, leading to
an increased of rheological parameters for all densities. In the stability tests the best results
were obtained at higher densities, becoming more stable with concentrations from 3 %,
showing no relegation. In the compressive strength tests, the paste with a density of 13,5
lb/gal with concentration of 4,0 % of bentonite got a higher mechanical strength, but very
viscous, which may hinder the pumping. Through the characterization of X-ray diffraction
(XRD) of pure bentonite was observed the presence of montmonrilonita and quartz phases
which are typical of clay. The XRD of the cement pastes of 13,5 lb/gal was observed that
there was the presence of etringite, portlandite, calcium silicate and quartz. It was also
observed that the images obtained by scanning electron microscopy (SEM) the paste of 13,5
lb/gal with 4 % bentonite showed notoriously the presence of ettringite needles, as well as the
steps of portlandite and calcium silicate cement hydration products. Finally, it can be
considered that the paste have worked best, are the pastes with a density of 13,5 lb/gal, with
concentrations of 2,0 % and 3,0 %, because they are more stable and mechanically strong,
compared with the other with lower densities.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/19792 |
| Date | 09 February 2015 |
| Creators | Marques, Jacqueline Ferreira Santos |
| Contributors | 83933212715, http://lattes.cnpq.br/0930845549110627, Fernandes, Maria Roseane de Pontes, 03869604450, http://lattes.cnpq.br/6135213219185858, Freitas, J?lio Cezar de Oliveira, 00957245408, http://lattes.cnpq.br/2357217530716519, Freitas, J?lio Cezar de Oliveira, Vieira, Marcela Marques |
| Publisher | Universidade Federal do Rio Grande do Norte, PROGRAMA DE P?S-GRADUA??O EM CI?NCIA E ENGENHARIA DE PETR?LEO, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| 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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