Research on Corrosion Inhibitors for Acid Stimulation

Abstract In the Oil & Gas industry, formation treatment with acids is an established method to stimulate carbonates or dissolve fines. Either organic acids such as citric or acetic acid or mineral acids such as HCl or HF are injected into the well at high concentrations. In the absence of corrosion inhibitors, the generalized corrosion rate increases exponentially with acid concentration and temperature. This can be reduced to an acceptable level by adding appropriate concentrations of inhibitor products in order to protect and prolong the useful lifetime of the hardware present in the well. Currently, inhibitor packages demonstrate high efficiency with carbon steels and at temperatures below 150°C. An overview of commonly applied acid corrosion inhibitors will be presented and a comparison is made between published data and data measured in-house. Some common pitfalls associated with the evaluation of acid corrosion inhibitors are highlighted. Weight loss analysis is a widely used method for assessing the efficiency of corrosion inhibitors. The effects of surface roughness and acid volume to metal surface area ratio are reviewed for gravimetric experiments in solutions of 14 and 28 wt. % hydrochloric acid at 78°C. Results on low carbon steel Coiled Tubing (CT) coupons that were either glass bead blasted, pickled or polished are reported. This paper also investigates the inhibiting effect of different classes of corrosion inhibitors in 14 wt. % HCl at 78°C using electrochemical methods (linear polarization resistance and Tafel extrapolation method) and evaluates the synergetic behavior of acetylenic alcohols with quaternary ammonium cations (QUATs).