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Journal of the Southern African Institute of Mining and Metallurgy

On-line version ISSN 2411-9717
Print version ISSN 2225-6253

Abstract

KADUKU, T.; DARAMOLA, M.O.; OBAZU, F.O.  and  IYUKE, S.E.. Synthesis of sodium silicate from South African coal fly ash and its use as an extender in oil well cement applications. J. S. Afr. Inst. Min. Metall. [online]. 2015, vol.115, n.12, pp.1175-1182. ISSN 2411-9717.  http://dx.doi.org/10.17159/2411-9717/2015/v115n12a5.

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 (SiO2) was extracted from the CFA and used to synthesize CFA-derived sodium silicate (CFA-Na2SiO3), a typical OWC slurry extender. The physico-chemical properties of the CFA-Na2SiO3were compared to those of a commercial sodium silicate (com-Na2SiO3) 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% CaCl2 by weight of water (BWOW) were prepared and extended using the CFA-Na2SiO3and the com-Na2SiO3at 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-Na2SiO3are consistent with those of com-Na2SiO3, indicating the purity of the CFA-Na2SiO3. A comparative study of the OWC slurries indicated that the slurries extended with CFA-Na2SiO3have slightly lower densities, lower viscosities, and higher compressive strength than those extended with com-Na2SiO3. This indicates that CFA-Na2SiO3slurries 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.

Keywords : oil well cementing; coal fly ash; sodium silicate; compressive strength.

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