分散剂FDN对G级油井水泥作用机理探讨

STUDIES ON DISPERSION AND SET RETARDATION OF OIL WELL CEMENT G BY DISPERSANTFDN

采用液相电导法和酸度法研究了分散剂FDN对G级油井水泥水化速度的影响。发现FDN促进水泥的早期水化,但吸附-络合作用及磺酸根离子对Ca(OH)_2核晶过程的“毒化”作用使后期水化速度减慢。本研究证实ζ电位升高是FDN广生分散作用的主要因素。当FDN的吸附达饱和时,ζ电位达最大值,水泥浆的分散程度最大。

The mechanizms of dispersant FDN, naphthaline sulfonate-formaldehyde condcnsates, for oil well cement are not clear enough until recently. In this work the effects of FDN on the hydration of oil well cement G are investigated by measuring electrical conductance and pH of liquid phase of the slurry. It is shown that the major factor in dispersing the cement particles can be attributed to the rise in Zeta-potential of the slurry with FDN. A dose of 0.8％(BWOC)leads to the maximum value of Zeta-potential, when the surface of cement particles is fully saturated with FDN molecules adsorpted and zero yield value of the slurry is observed at this FDN concentration. It is also shown that FDN accelerates hydration of the cement at early stage due to contact area enlargemeat, water diffusion promotion and complexing action of sulfonate groups in FDN but finally retards the hydration processes due to hydrophobicity of the adsorpted layer and steric effect of the complexes as well as 'sulfonate poisoning' the nucleation process of calcium hydroxide.