Desenvolvimento de sistemas microemulsionados retardados para aplicação na estimulação ácida em reservatórios carbonáticos
The necessity to make oil wells increasingly efficient, especially in conditions with high production costs, leads to continuous technological development in his area of knowledge. In December 2019, about 67% of Brazil's oil production came from wells in Pre-Salt carbonate rocks reservoirs....
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| Formaat: | doctoralThesis |
| Taal: | pt_BR |
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Universidade Federal do Rio Grande do Norte
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| Online toegang: | https://repositorio.ufrn.br/jspui/handle/123456789/29789 |
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| Samenvatting: | The necessity to make oil wells increasingly efficient, especially in conditions with high
production costs, leads to continuous technological development in his area of knowledge. In
December 2019, about 67% of Brazil's oil production came from wells in Pre-Salt carbonate
rocks reservoirs. Matrix Acidification is a stimulation technique widely used in carbonates to
increase its production as a result of the formation of high conductivity channels around the well,
called wormholes. Several characteristics interfere in acidizing process as anisotropy,
heterogeneity, oil saturation, and effective rock-acid reaction speed, making it complex
technique. Microemulsion systems, formed by thermodynamically stable auto-associative
structures that present low surface tension, can control mass and therefore interfere in reactive
processes. These systems have already been subject of studies. However, this a field of study is
still little explored. This work aims to develop acid oil in water microemulsion systems and test
their applications in standard carbonate rock. These systems used ALKONAT-L100 as a
surfactant, n-butanol as a co-surfactant, xylene as a nonpolar phase and HCl solutions as a polar
phase (1.54 w/w%, 8.27 w/w%, and 15 w/w%). The acid microemulsion systems were
characterized in ter terms of turbity, pH, drop size, conductivity, surface tension and thermal
stability. Different carbonate rocks were tested, and Indiana carbonate, a standard rock in
acidification studies, was chosen to represent the carbonate reservoirs in this study. The core
samples were characterized in terms of composition, porosity, permeability, and reactivity in
acid. In order of evaluate the interaction between the treatment fluids and Indiana carbonate,
studies were carried out, such as the influence of the HCl concentration and the type of treatment
systems on wettability and surface reactivity behavior. Experimental designs were carried out in
different conditions to verify the influence of HCl concentration, temperature, and reaction time
on the reaction speed. To study the technical feasibility of using microemulsified systems, tests
were performed to produce Pore Volume to Breakthrough (PVBT) curves followed by
subsequent dissolution patterns analyses by high resolution microtomography (Micro-CT) and
NMR. The results showed that even at high HCl concentrations, microemulsion systems were
formed close to the polar phase apex, and they were thermally resistant (at least 100 OC). The
treatment systems containing surfactants, especially the microemulsified ones, caused a
significant increase on the rock surface wettability to water and reduced the surface reactivity,
compared with the ones with no surfactant. The speed of acid-rock of treatment systems that did
not contain surfactants is basically limited by the concentration of HCl, regardless of saturation,
whereas for systems containing surfactants, the time factor is also significant. The Micro-CT and
NMR results showed effective wormholes morphologies when microemulsified systems were
used. In this way, the results obtained demonstrate that microemulsified systems have efficiency
and good prospects for application in retard acid-rock reaction in the acid stimulation in
carbonates rocks. |
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