Temperature-controlled sinking delivery of thermostable alkyl substituted benzimidazole by sodium alginate polymer gel network for efficient inhibition of carbon steel corrosion in acid oilfield solution

A novel imidazole corrosion inhibitor (OBIP) was synthesized by amide reaction using 2-aminobenzimidazole and 4-octadecyloxybenzoic acid as raw materials. Heavy polymer capsules (SA@PAM@OBIP) comprising a temperature-responsive high-temperature corrosion inhibitor were prepared by loading OBIP into an alginate/polyacrylamide (SA@PAM) hydrogel network. The inhibition effects of OBIP on Q235 were investigated through the application of electrochemistry and surface analysis techniques. The results show that when Q235 is immersed in the acidic oilfield solution, the corrosion inhibition rate of OBIP at 8 × 10^-4mol/L is 93 % and that at 90℃ is 85 %. The calculated electronic parameters (energy gap ΔE = 2.4391 eV) suggest that OBIP molecules are more likely to undergo electron transfer with the iron surface, inhibiting metal corrosion. Additionally, the UV spectrum and EQCM test demonstrate that the SA@PAM@OBIP network capsule exhibits temperature-responsive behavior. Upon reaching the high-temperature working area at the bottom of the well at a speed of 14 cm/s, the SA@PAM@OBIP capsule begins to release OBIP, thereby providing targeted protection against high-temperature corrosion. In addition, SA@PAM@OBIP capsules, which release OBIP in stages, have been shown to triple the duration of corrosion inhibitor action, and the composite carrier reduces the redundancy and waste of corrosion inhibitors caused by oilfield water production processes. In this study, a controllable, efficient, targeted, and stable temperature-responsive corrosion inhibition system was established with the objective of providing long-term targeted anti-corrosion protection for metals in the extreme environment of oil and gas fields.