Influence of classical and modern superplasticisers on the chemical and rheological behaviour of oil well cement: a comparative study

The need for cements with good workability for oil well drilling purposes makes a systematic study necessary in order to investigate different cement–admixture combinations. In the present study the superplasticising effect induced by third-generation polycarboxylates was benchmarked against conventional melamine-based superplasticisers on oil well cement. Two commercial superplasticisers were studied at five different concentrations. The hydration progress over time was analysed by way of monitoring the crystal growth using a scanning electron microscope. Infrared and ²⁹Si solid state nuclear magnetic resonance spectra were measured. Rheological and surface tension studies were conducted at the early stages of hydration. The results show clearly that the third-generation polycarboxylate under investigation was superior in terms of better cement workability. This superiority was attributed to the multi-branched nature of this compound which induced sterical repulsion on the cement grain surface. Moreover, the superplasticiser–cement complexed phases were found to be thermodynamically unstable as evidenced by infrared and nuclear magnetic resonance spectra. Recommendations are made concerning the application of superplasticisers in the oil industry in order to enhance the performance of the drilling process.