Covalently bonded AMPS-based copolymerCSH hybrid as a fluid loss additive for oilwell saline cement slurry in UHT environment

The organic/inorganic hybrid fluid loss additive PANI C S H was synthesized to adapt for high salinity cementing at ultrahigh temperatures (UHT, 200–240 °C). Unlike common physical blending, the PANI-C-SH was synthesized by grafting calcium silicate hydrate (C S H) from polycarboxylate copolymer PANI [P(AMPS-NNDMA-IA)] via “peptide coupling” and “sol–gel” reactions. When added into the UHT cement slurry, the hybrid PANI C S H exhibited more pronounced saturated saline cement slurry fluid loss control ability (31 mL at 240 °C) than that of PANI copolymer (68 mL). The three-dimensional spatial morphology of PANI C S H hybrid was able to plug and fill in the micro voids of the filter cake and resulted in effective refinements of the micro-pore structure, which compensated the deteriorated fluid loss control capacity caused by the weakened adsorption of copolymer PANI in saturated saline cement slurry.