doctoralThesis
Nanocristais de celulose de resíduo de algodão e aplicação em pastas de cimento para poços de petróleo
Fecha
2021-09-20Registro en:
LIMA, Mailon Aguimar de. Nanocristais de celulose de resíduo de algodão e aplicação em pastas de cimento para poços de petróleo. 2021. 80f. Tese (Doutorado em Química) - Centro de Ciências Exatas e da Terra, Universidade Federal do Rio Grande do Norte, Natal, 2021.
Autor
Lima, Mailon Aguimar de
Resumen
There are 3 (three) main characteristics for a good durability of the cement sheath coming
from the primary cementation: low porosity, low permeability and high mechanical
strength. Cellulose nanocrystals (CNC) have been widely applied as reinforcement
material in cement matrices, as small amounts of this nanomaterial considerably improve
these 3 properties. For this reason, the objective of this research was to obtain
nanocrystals from a cotton waste and to evaluate the influence of their addition, in
different concentrations, on the compressive strength, porosity and permeability of
Portland Casse G cement pastes. Cellulose nanocrystals were obtained from a cotton fiber
residue from the sanding process, through acid hydrolysis (H2SO4 65% m/m). The
stability of the resulting suspension was measured by the zeta potential, in addition the
NC characterization was performed by transmission electron microscopy (TEM), TGA
and DRX. Concentrations of 0 to 0.3% of NC were evaluated in the compressive strength,
porosity and permeability of the specimens. The results show that the resulting
nanocrystal suspension was well dispersed, with needle-shaped nanocrystals
(nanowhiskers) with a diameter and length of approximately 17 and 175 nm respectively.
The mechanical tests show a rapid gain in compressive strength (after 24 hours of curing),
around 45% for the formulation containing 0.2% of CNC. Even after 28 days of curing,
pastes reinforced with CNC still show better results when compared to the standard, with
a gain greater than 30%, also for formulation 0,2%. The porosity and permeability tests
show that even standard pastes (without the addition of CNC) have low permeability.
Even so, the addition of nanocrystals reduced porosity by approximately 27% and paste
permeability by 25% after adding any concentrations of CNC. The results indicate that
there is a great potential in the use of CNC to improve the mechanical strength of oil well
cement, as well as reducing its porosity and permeability, thus enabling a more effective
sealing of the annular space, preventing gas migration through the cement sheath and,
consequently, improving well integrity.