Banca de QUALIFICAÇÃO: BRUNO LEONARDO DE SENA COSTA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : BRUNO LEONARDO DE SENA COSTA
DATA : 30/11/2017
HORA: 10:00
LOCAL: Auditório do LABCIM
TÍTULO:

Corrosive attack on oil well Portland cement: The phenomenon of carbonation in different approaches

PALAVRAS-CHAVES:

Carbonation; Oil well cement; Cementing; Physical properties; Cement hydration; CO2-supercritical; CO2-saturated.

PÁGINAS: 90
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
RESUMO:

In contact with carbon dioxide (CO2) and in the presence of water, the Portland cement matrix undergoes a deleterious process called carbonation. This phenomenon occurs through chemical reactions between carbonic acid, formed by the reaction of CO2 with water, and some hydrated cement products. Reactions promote transformations leading to changes in the physical properties of cement. The Portland cement matrix exposed in a carbon dioxide environment will inevitably suffer the effects of carbonation, so in both surface and subsurface conditions the material will undergo corrosion. In subsurface due to the increase in temperature and pressure the medium becomes potentially more damaging to the cement, so the oil and gas area, especially the well cementing industry, is very interested in this problem. The topic is the focus of several researches, and much has been studied and developed over the years in order to understand the process and prevent, mitigate and combat the CO2 attack. In this way, this work had the objective of deepening the research on carbonation, having developed and being composed by other studies with the objectives of: evaluating, interpreting and proposing a model to explain the action of carbonation in Portland cement matrix static sedimentation is unstable; to investigate the influence of the hydration time of the class G cement particles before the contact with the CO2, making a parallel between the time of hydration and applied operational scenarios; to analyze the result of the action of the CO2 attack on samples of class G cement exposed in an autoclave where in the upper part of the pressure vessel the samples were carbonated by CO2-supercritical and in the lower part of the vessel the samples were attacked by CO2-saturated in aqueous medium. In the first study, two slurries of Portland cement were intentionally formulated with characteristic and distinct behavior, where one of the slurries has the capacity to keep the particles in suspension producing a stable system, while the other presented particles sedimentation promoting an unstable system. Both slurries were carbonated for 30 days in an autoclave. The carbonate samples were characterized by static sedimentation test, phenolphthalein analysis and X-ray diffraction with Rietveld method. In all the samples the carbonation phenomenon was observed, but the sections of the unstable slurry presented a larger carbonated area. A model was proposed for sedimentation and carbonation behavior in the unstable slurry based on fluid mechanics. In another study, three slurries of the same formulation were investigated, but were cured for periods of 8 hours, 7 days and 28 days before contact with CO2. These differences in curing time were intended to simulate operational situations where there is contact with the compound in subsurface. The results showed different processes, but with similar effects of carbonation at the end. The sample cured for 7 days was more affected and those with 8 hours and 28 days resisted more, but through different preservation mechanisms. And in a final study, samples were exposed at the same time in supercritical and saturated CO2. The analyzes showed significantly different results, where the samples exposed to the saturated medium suffered a major attack. With reference to image analysis and the formation of carbonates identified by the XRD technique and quantified by the Rietveld method, the attack on the samples subjected to saturated CO2 was 35% higher. In the light of the above, this work presents studies that seek to promote a greater understanding of phenomenology and give subsidies for the development of technologies that combat carbonation.

MEMBROS DA BANCA:
Presidente - 349770 - DULCE MARIA DE ARAUJO MELO
Externo ao Programa - 1804366 - JÚLIO CÉZAR DE OLIVEIRA FREITAS
Interno - 6347420 - MARCUS ANTONIO DE FREITAS MELO