Effects of amphoteric polycarboxylate dispersant (APC) and acetone formaldehyde sulfite polycondensate (AFS) on the rheological behavior and model of oil well cement pastes

Abstract

Two oil-well cement dispersants, Amphoteric polycarboxylate dispersant (APC) and Acetone formaldehyde sulfite polycondensate (AFS) with different dosages (0.10%,0.15% and 0.20% by weight of cement), were used to investigate the rheological performance of cement paste. A simple equipment, six-speed rotational viscometer, was employed to study the relationship between the shear stress and shear rate of the fresh cement paste. Three typical rheological models including Herschel-Bulkley model, Bingham model, and Power-law model, were applied to estimate the yield stress, plastic viscosity and trend of the flow curves. The validity of these rheological models in predicting the rheological properties of cement paste was confirmed by considering the fitting optimization index (R2). Besides, the thixotropic behavior of cement paste with different dispersants was investigated. The results show that the rheological properties of cement paste improve dramatically with either APC or AFS addition. And the APC dispersant with better dispersion behavior is significantly efficient in decreasing the consistency index and increasing the flow behavior index than AFS dispersant. The Herschel-Bulkley model with higher fitting optimization index was found to fit the experimental data best compared with Bingham model and Power-law model. The degree of thixotropy of cement paste with more dispersant addition decreases compared to the reference, which is related to the rheological behavior.