Synthesis of sodium silicate from South African coal fly ash and its use as an extender in oil well cement applications

In this work, the use of sodium silicate derived from South African coal fly ash (CFA) in oil well cement (OWC) applications is reported. Silica (SiO sub(2)) was extracted from the CFA and used to synthesize CFA-derived sodium silicate (CFA-Na sub(2) SiO sub(3)), a typical OWC slurry extender. The p...

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Bibliographic Details
Published in:Journal of the South African Institute of Mining and Metallurgy 2015-12, Vol.115 (12)
Main Authors: Kaduku, T, Daramola, M O, Obazu, F O, Iyuke, S E
Format: Article
Language:English
Subjects:
Cements
Coal
Crude oil
Fly ash
Fourier transforms
Silicon dioxide
Slurries
Sodium silicates
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Summary:In this work, the use of sodium silicate derived from South African coal fly ash (CFA) in oil well cement (OWC) applications is reported. Silica (SiO sub(2)) was extracted from the CFA and used to synthesize CFA-derived sodium silicate (CFA-Na sub(2) SiO sub(3)), a typical OWC slurry extender. The physico-chemical properties of the CFA-Na sub(2) SiO super(3) were compared to those of a commercial sodium silicate (com-Na sub(2) SiO sub(3)) using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. OWC slurries with varying proportions of cement, distilled water, and 2% CaCl sub(2) by weight of water (BWOW) were prepared and extended using the CFA-Na sub(2) SiO sub(3) and the com-Na sub(2) SiO sub(3) at compositions ranging from 0.25-2.5% by weight of cement (BWOC). Rheological properties of the slurries were evaluated using American Petroleum Institute procedures and compared. The physico-chemical properties of the CFA-Na sub(2) SiO sub(3) are consistent with those of com-Na sub(2) SiO sub(3), indicating the purity of the CFA-Na sub(2) SiO sub(3). A comparative study of the OWC slurries indicated that the slurries extended with CFA-Na sub(2) SiO sub(3) have slightly lower densities, lower viscosities, and higher compressive strength than those extended with com-Na sub(2) SiO sub(3). This indicates that CFA-Na sub(2) SiO sub(3) slurries would be easier to pump and preferable where early strength development is critical. This report could be instrumental in providing a way for the beneficiation of South African CFA in the petroleum, oil, and gas industry.
ISSN:0038-223X
2411-9717
DOI:10.17159/2411-9717/2015/v115n12a5