Large amounts of water can be produced during the production of hydrocarbons from underground reservoirs. Salts are always dissolved in these produced waters. The concentration of dissolved salts can be as high as 400 g/l. For the first time, the effect of salt concentration on uniform hydrogen sulfide (H2S) corrosion of carbon steel in aqueous solutions is studied. Linear polarization resistance (LPR) and potentiodynamic polarization (PD) experiments were conducted in aqueous solutions at 20°C and pH 5.00 saturated with an H2S/N2 gas mixture with a total pressure of 1 bar and H2S concentration of 100 ppm(v). Two NaCl concentrations were tested: 1 and 20 wt.%. A rotating cylinder electrode with a rotational speed of 1000 rpm was used as the specimen. LPR corrosion rates indicated that H2S corrosion rate decreased with increasing salt concentration. PD results showed that the corrosion process was under mixed control. Increasing salt concentration retarded both the anodic and the cathodic reactions, and thereby, decreased the rate of uniform H2S corrosion.
Large amounts of water can be produced during extraction of hydrocarbons from underground reservoirs.1 It is well understood that produced waters usually contain high amounts of dissolved salts, up to 28 wt.%.2 In addition to salts, dissolved corrosive gases (CO2 and H2S) are present in produced water, which make the mixture a complex corrosive environment for metallic parts and equipment used throughout the production process.
Internal H2S corrosion of carbon steel tubulars often occurs in the oil and gas industry, particularly when drilling deeper to search for new oil and gas reservoirs.3,4 In contrast to CO2 corrosion, a limited number of studies exist for H2S corrosion. And, to the best knowledge of the authors, no study has been done on the effect of salt concentration on uniform H2S corrosion. It is necessary to understand H2S corrosion mechanisms in high saline solutions to develop a correct corrosion prediction. For the first time, the effect of salt concentration on uniform H2S corrosion of carbon steel in aqueous solutions is presented as part of a wider mechanistic study.