Characteristics of polycarboxylate-based dispersant suitable for medium and low temperature oil well cementing

•PW1010 improves the dispersion of cement paste at medium and low temperature.•The dispersion mechanism of PW1010 is steric hindrance.•PW1010 delays the early hydration of oil well cement.•PW1010 promotes the early compressive strength and reduces the permeability. The rheology and hydration properties of oil well cement paste at medium and low temperature are of great importance for cementing marine shallow formation. This paper studies the effect of one kind of polycarboxylate-based dispersant (PW1010) on the performance of oil well cement paste and compares it with sulfonated aldehyde-ketone condensation polymer dispersant (SAF). The influence of PW1010 and SAF on the rheological properties of oil well cement paste is investigated, and is analysed by adsorption isotherm and Zeta potential tests. The influence of PW1010 on the hydration of oil well cement is conducted by compressive strength measurements, isothermal calorimetry (ICC), X-ray diffraction (XRD), thermogravimetric analyzer (TGA), mercury intrusion porosimetry (MIP) and permeability. The results show that an oil well cement paste containing PW1010 has better rheological properties at medium and low temperature than that containing SAF, because PW1010 has comb-like structure, which provides stronger steric hindrance effect. Moreover, even though PW1010 delays the hydration of oil well cement, it increases the early-age compressive strength and reduces the permeability at medium and low temperature. This is mainly because PW1010 improves the dispersion of cement particles and reduces the porosity and large pores of the hardened cement. This study has important significance for ensuring the well cementing proceeding smoothly and improving cementing quality.