The review article disuses about oilfield acidizing procedure. The focus was on HCl solutions and the elevated temperatures usually encountered in the well acidizing procedure. Lower grade steel materials are the most commonly used construction materials for oil and gas wells due to their low cost and high performance. During the acidizing procedure these steel materials need to be inhibited. This review article describes the development of acidizing inhibitor formulation design with the special emphasis on the environmentally acceptable chemicals used in the oilfield industry. It also describes the potential danger of conventional acids commonly employed in the acidizing procedure and the use of methanesulphonic acid as an alternative acid solution for acidizing, due to its beneficial properties. Moreover, most of the developed inhibitors or their formulations no longer meet the Oslo Paris Commission [Fourth North Sea Minister’s Conference’ Esbjerg, Norway, June 8-9, 1995] requirements because their primary active ingredients may be harmful if discharged into the environment. Current research is thus focused on developing alternatives to those currently employed. Currently, this article is the most downloaded and the most cited article in the Corrosion Science journal since 2014.
This study analyses the corrosion inhibition efficiency of certain azoles for C15 grade mild steel in 3 wt.% NaCl solution by employing immersion tests and different electrochemical techniques. The possible synergistic effect of azole inhibitors and metal salts was also investigated. It was found that tolyltriazole is the most effective corrosion inhibitor. Additional surface analyses were performed for specimens inhibited with tolyltriazole. ATR-FTIR analysis confirmed the adsorption of tolyltriazole on the steel surface and 3D profilometry and AFM showed that tolyltriazole reduces surface roughness compared with non inhibited solution. Contact angle analysis showed that tolyltriazole-inhibited steel specimens evidenced a hydrophilic character.
In this work, AISI C1018 lower grade steel material was examined in 20 wt.% methanesulphonic acid (MSA) solutions containing different chemicals to design corrosion inhibitor formulations. These formulations were based on acetylenic alcohol, cinnamaldehyde, 1 dodecylpyridinium chloride, and methanol. It was shown that AISI C1018 steel has to be inhibited in MSA solution and that it is crucial to find the right combination of chemicals to design effective corrosion inhibitor formulations. Electrochemical analyses were carried out in order to test these systems. It was shown that acetylenic alcohol-based formulations significantly improve corrosion inhibition effectiveness compared with the individual corrosion inhibitor components used separately and that they mainly work as mixed-type inhibitors.
In this study, the corrosion inhibition effectiveness of 8 amines, i.e. 2-ethylhexyl amine, aniline, benzylamine, butylamine, ethylamine, isopropylamine, octylamine, and triethanolamine, on C15 grade mild steel in 3 wt.% NaCl solution is reported. The corrosion inhibition performance of the amines was studied using immersion tests at 25 and 70 °C, with and without the addition of KI as a possible intensifier. Among the inhibitors tested at 0.1 wt.% concentration, the lowest corrosion rates were obtained for specimens immersed in solutions containing 2-ethylhexyl amine at 25 °C and triethanolamine at 70 °C. The highest inhibition effectiveness at 25 °C among all amines tested was obtained for 1.0 wt.% butylamine with the addition of 0.5 wt.% KI, while at 70 °C the lowest corrosion rate was obtained for specimens inhibited with 1.0 wt.% isopropylamine. Surface analysis was subsequently performed on specimens inhibited by the most effective inhibitors. Adsorption of the selected amines on the C15 grade mild steel surface was confirmed by ATR-FTIR. 3D profilometry showed a reduction in the surface roughness (less corroded) for the specimens inhibited with these inhibitors compared to the non-inhibited specimens. Contact angle measurements showed that all of the tested specimens are hydrophilic.
In the article the corrosion behaviour of 2205 duplex stainless steel in methanesulphonic acid (MSA) at elevated temperature was investigated. It was proposed that uninhibited MSA could be utilised in acidising procedures in petroleum wells constructed of 2205 duplex stainless steel. It was shown that 2205 duplex stainless steel is highly resistive to corrosion in non inhibited 20 wt.% MSA solution – meaning that it does not contain any corrosion inhibitor. Corrosion rates of 2205 duplex stainless steel in MSA solution with or without 24.13 bar CO2 at 150 °C after 6 h of immersion were lower than what is often required by the petroleum industry. It has to be emphasised that it is uncommon for steel materials to be so resistive in an non inhibited acid solution at elevated temperature, which is the case for MSA.