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Previous issue date: 2008-04-25 / Portland-polymers composites are promising candidates to be used as cementing material in Northeastern oil wells of Brazil containing heavy oils submitted to steam injection. In this
way, it is necessary to evaluate its degradation in the commonly acidizind agents. In addition, to identify how aggressive are the different hostile environments it is an important contribution on the decision of the acidic systems to be used in. It was investigated the performance of the Portland-polymer composites using powdered polyurethane, aqueous polyurethane, rubber tire residues and a biopolymer, those were reinforced with polished carbon steel SAE 1045 to make the electrochemical measurements. HCl 15,0 %, HCl 6,0 % + HF 1,5 % (soft mud acid), HCl 12,0 % + HF 3,0 % (regular mud acid) and HAc 10 % + HF 1,5 % were used as degrading environment and electrolytes. The more aggressive acid solution to the plain Portland hardened cement paste was the regular mud acid, that showed loss of weight around 23.0 %, followed by the soft mud acid, the showed 11.0 %, 15.0 % HCl with 7,0 % and, at last the 10.0 % HAc plus HF 1.5 % with just 1.0 %. The powdered polyurethane-composite and the aqueous polyurethane one showed larger durability, with reduction around 87.0 % on the loss of weight in regular mud acid. The acid attack is superficial and it occurs as an action layer, where the degraded layer is responsible for the
decrease on the kinetic of the degrading process. This behavior can be seen mainly on the Portland- aqueous polyurethane composite, because the degraded layer is impregnated with chemically modified polymer. The fact of the acid attack does not have influence on the compressive strength or fratography of the samples, in a general way, confirms that theory. The mechanism of the efficiency of the Portland-polymers composites subjected to acid attack
is due to decreased porosity and permeability related with the plain Portland paste, minor quantity of Ca+2, element preferentially leached to the acidic solution, wave effect and to substitute part of the degrading bulk for the polymeric one. The electrolyte HAc 10 % + HF 1,5 % was the least aggressive one to the external corrosion of the casing, showing open circuit potentials around +250 mV compared to -130 mV to the simulated pore solution to the first 24 hours immersion. This behavior has been performed for two months at least. Similar corrosion rates were showed between both of the electrolytes, around 0.01 μA.cm-2. Total impedance values, insipient arcs and big polarization resistance capacitive arcs on the Nyquist plots, indicating passivity process, confirm its efficiency. In this way, Portlandpolymers
composites are possible solutions to be succeed applied to oilwell cementing concomitant submitted to steam injection and acidizing operation and the HAc 10,0 % + HF
1,5 % is the less aggressive solution to the external corrosion of the casing / Comp?sitos Portland-pol?meros s?o promissores candidatos ? cimenta??o de po?os de petr?leo contendo ?leos pesados submetidos ? inje??o de vapor nos campos do Nordeste do
Brasil. Assim, faz-se necess?rio avaliar sua degrada??o frente aos ?cidos comumente utilizados em opera??es de acidifica??o. Al?m disso, identificar a agressividade dos diferentes meios hostis ? corros?o externa do revestimento constitui uma importante contribui??o na decis?o dos sistemas ?cidos a serem utilizados. Foram avaliados comp?sitos adicionados de poliuretana em p?, poliuretana em solu??o aquosa, borracha de pneu mo?da e um biopol?mero
atrav?s das API Spec. 10, sendo refor?ados com a?o carbono polido SAE 1045 para os ensaios eletroqu?micos. HCl 15,0 %, HCl 6,0 % + HF 1,5 % (soft mud acid), HCl 12,0 % +
HF 3,0 % (regular mud acid) e HAc 10,0 % + HF 1,5 % foram aplicadas como meios degradantes e eletr?litos. A solu??o ?cida mais agressiva ? pasta de cimento Portland
convencional ? a regular mud acid, que apresenta perda de massa em torno de de 23,0 %, seguida da soft mud acid, com perda de massa de 11,0 % e da solu??o HCl 15,0 %, em torno
de 7,0 %. As menores perdas de massa, no entanto, s?o relativas ao meio agressivo HAc 10,0 % + HF 1,5 %, com perdas no patamar de 1,0 %. Os comp?sitos com poliuretana em p? e poliuretana em solu??o aquosa apresentaram maior durabilidade, com redu??o em torno de 87,0 % na perda de massa frente ao regular mud acid. O ataque ?cido ? superficial e ocorre como uma frente de a??o, sendo a camada degradada respons?vel pela minimiza??o da
cin?tica do processo de degrada??o, principalmente no comp?sito Portland-poliuretana em dispers?o aquosa, por ser impregnada por pol?mero quimicamente modificado. O fato de n?o haver, de uma forma geral, influ?ncia do ataque ?cido na resist?ncia ? compress?o e fratografia das amostras, ap?s ataque ?cido, ratifica essa teoria. O mecanismo da maior
efici?ncia dos comp?sitos Portland-pol?meros frente ao ataque ?cido ? regido por menores porosidades e permeabilidades que a pasta de cimento convencional, menor quantidade de
Ca+2, elemento prioritariamente lixiviado para a solu??o ?cida, efeito tortuosidade e substitui??o de massa degrad?vel por massa polim?rica. O eletr?lito HAc 10,0 % + HF 1,5 %
foi o menos agressivo ? corros?o externa do revestimento, com potenciais de circuito aberto superiores ? solu??o simuladora dos poros como eletr?lito, +250 mV frente a -130 mV para as primeiras 24 horas de imers?o, mantendo esse comportamento ao longo de, pelo menos, 2 meses de imers?o. Correntes de corros?o semelhantes entre esses dois eletr?litos, em torno de 0,01 μA.cm-2, e valores de imped?ncia total, arcos incipientes e grandes arcos capacitivos de resist?ncia de polariza??o, indicadores de passiva??o nos diagramas de Nyquist, confirmam
sua efici?ncia. Assim, comp?sitos Portland-pol?meros s?o solu??es poss?veis de serem empregadas em cimenta??o de po?os de petr?leo submetidos concomitantemente ? inje??o de
vapor e opera??es de acidifica??o, sendo a solu??o HAc 10,0 % + HF 1,5 % menos agressiva ? corros?o externa do revestimento ap?s opera??es de acidifica??o
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/12703 |
| Date | 25 April 2008 |
| Creators | N?brega, Ana Cec?lia Vieira da |
| Contributors | CPF:15724520800, http://lattes.cnpq.br/0022988322449627, Melo, Marcus Ant?nio de Freitas, CPF:04514998320, http://lattes.cnpq.br/5840621182000517, Tonholo, Josealdo, CPF:16392398805, http://lattes.cnpq.br/6333407087554681, Bezerra, Ulisses Targino, CPF:45109419434, Melo, Dulce Maria de Ara?jo, Martinelli, Ant?nio Eduardo |
| 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/doctoralThesis |
| 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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