Optimizing the performance of a composite corrosion/scale inhibitor for CO2 flooding wells

To solve the corrosion and scaling problems of CO2 flooding wells, a novel composite corrosion and scale inhibitor FIQC-APES was developed in the study. Two agents with high performances were identified from six corrosion inhibitors and five scale inhibitors based on quantum chemical calculations, electrochemical methods, and static scale inhibition tests. After optimizing the reagent ratio, the two agents were devised and combined together to create a new composite corrosion and scale inhibitor for CO2 flooding wells. Finally, the protective performance of the composite agent was evaluated under simulated working conditions. The results revealed that a ratio of corrosion inhibitor (FIQ-C) to scale inhibitor (APES) (2:1) was the optimal ratio for composite corrosion and scale inhibitors. On metal surface and calcite crystal surface, corrosion inhibitor and scale inhibitor molecules could be stably adsorbed. The composite corrosion and scale inhibitor had a good protective effect on H-grade sucker rods, N80 pipes, and P110 pipes under the simulated conditions of CO2 flooding wells (CO2 partial pressure was 4 MPa). The corrosion rate was less than 0.045 mm/y. The corrosion and scale inhibition rates were respectively more than 96% and 95%, suggesting that the corrosion and scale inhibition performances of the composite inhibitor met the requirements for oilfield protection. The study suggested that FIQC-APES could act as a novel inhibitor for controlling corrosion and scale in CO2 flooding wells.