Efeito da incorporação de diatomita na estabilidade e permeabilidade de compósitos cimentíceos espumados aplicados a poços de petróleo
Lightweight oilwell cement slurries have been recently studied as a mean to improve zonal isolation and sheath-porous formation adherence. Foamed slurries consisting of Portland cement and air-entraining admixtures have become an interesting option for this application. The loss in hydrostatic pr...
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| Formato: | Dissertação |
| Idioma: | por |
| Publicado em: |
Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/12785 |
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| Resumo: | Lightweight oilwell cement slurries have been recently studied as a mean to improve zonal
isolation and sheath-porous formation adherence. Foamed slurries consisting of Portland cement
and air-entraining admixtures have become an interesting option for this application. The loss in
hydrostatic pressure as a consequence of cement hydration results in the expansion of the air
bubbles entrapped in the cement matrix, thus improving the sheath-porous formation contact.
Consequently, slurries are able to better retain their water to complete the hydration process. The
main objective of the present study was to evaluate the effect of the addition of an air-entraining
admixture on the density, stability and permeability of composite slurries containing Portland
cement and diatomite as light mineral load. Successful formulations are potential cementing
materials for low fracture gradient oilwells. The experimental procedures used for slurry
preparation and characterization were based on the American Petroleum Institute and ABNT
guidelines Slurries containing a pre-established concentration of the air-entraining admixture and
different contents of diatomite were prepared aiming at final densities of 13 to 15 lb/gal. The
results revealed that the reduction of 15 to 25% of the density of the slurries did not significantly
affect their strength. The addition of both diatomite and the air-entraining admixture increased
the viscosity of the slurry providing better air-bubble retention in the volume of the slurry. Stable
slurries depicted bottom to top density variation of less than 1.0 lb/gal and length reduction of the
stability sample of 5.86 mm. Finally, permeability coefficient values between 0.617 and 0.406
mD were obtained. Therefore, lightweight oilwell cement slurries depicting a satisfactory set of
physicochemical and mechanical properties can be formulated using a combination of diatomite
and air-entraining admixtures for low fracture gradient oilwells |
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