Synthesis, characterization and working mechanism of a novel sustained-release-type fluid loss additive for seawater cement slurry.

Synthetic polymer fluid loss additive (FLA), an important type of admixture, was broadly applied in modern well cementation. However, the filter loss volume and fluidity of cement pastes containing polymer-FLA would deteriorate remarkably when sea water was used in mixing slurries instead of fresh water. In this study, a novel sustained-release-type fluid loss additive(S-FLA) was synthesized by means of anion-exchange intercalation reaction between an anionic type-copolymer and a calcium/aluminum type-Layered Double Hydroxide (Ca/Al-LDH). Based on the fluidity and compressive strength of experiments, it was found that in seawater mixing conditions, this composite material not only utilized its sustained release effect to significantly improve retention fluidity performance, but also the seed crystal effect of the Ca/Al-LDH effectively alleviated the declining in compressive strength of the slurries caused by the carboxyl group in the polymer. More interestingly, the realization of the slow release function increased actual adsorption capacity of the anionic polymer on the surface of cement hydrated particles, which made its controlling water loss effect was also better than that of the conventional FLA. The above advantages of this hybrid materials created the possibility to surmount the negative effect of electrolytes present in seawater, so as to provide some useful references for its practical application in the offshore well cement.