A New Geopolymer Well Cementing Gelled Material and Analysis of Its Resistance to Salt Attack

A geopolymer has been proposed to replace the low corrosion resistance gelled material used in cement slurries for cementing deep high salinity wells. Experiments have been done to study the resistance of the geopolymer to salt attack. A mixture of fly ash, metakaolin based geopolymer and class G cement was cured in salt solutions of different salinities for 28 d, and the compressive strength of the mixture was measured. It was found that with an increase in salinity, the loss of the compressive strength of the common set cement is increasing, while the compressive strength of the mixture is increasing with increase in salinity to the contrary. Element analysis with XRF, mineral analysis with XRD and analysis of acidity and alkalinity showed that ion exchange in saltwater environment remarkably changes the hydration environment and hydration product components of cement, resulting in remarkable strength loss of the cement. For the geo-polymerization of geopolymer, however, the effect of the ion exchange process is quite weak. Morphology analysis using SEM demonstrated that in salt water, geopolymer can form much denser microstructure, which is considered to be the main reason for the geopolymer to have an enhanced strength. This study showed that a geopolymer at its early age has superior resistance to salt attack, and can be used to replace cement in cementing deep high salinity wells after being verified with more experiments.