Synthesis and Performance Study of Salt‐Tolerant Acidizing Retarder Characterized by Ultra‐Long Carbon Chain

ABSTRACT In response to the insufficient salt resistance of conventional polymer‐based acidizing retarders, a salt‐tolerant acidizing retarder (DADN21) with an ultra‐long carbon chain was synthesized. The synthesis conditions were optimized using the single‐factor method. The molecular structures of the hydrophobic monomer (DP) and the retarder DADN21 were characterized by FT‐IR and 1 H‐NMR. The salt tolerance, retarding performance, acid‐rock reaction rate, rheological properties of spent acid, compatibility, and retardation mechanism of DADN21 were systematically evaluated, and the rock surface morphology was observed via SEM‐EDS. The results reveal that DADN21 possesses a lower critical association concentration than short‐chain analogs, thus showing stronger association ability and improved salt‐resistant thickening behavior at the same concentration. In addition, SEM observations combined with viscosity tests demonstrate that the rigid heterocyclic structure of NVP effectively suppresses the excessive curling of ultra‐long carbon chains and enhances the associative thickening effect. Moreover, DADN21 can form an adsorption film on rock surfaces and partially desorb in the late stage of the acid‐rock reaction, which helps reduce formation damage. Additionally, benefiting from the merits of low critical association concentration, remarkable salt tolerance, favorable retarding efficiency, and reduced formation damage, this retarder exhibits promising application potential for deep acidizing in high‐salinity carbonate reservoirs.