During start-up of sour gas wells methanol is added in order to prevent hydrate formation in the piping. Earlier own results and literature data showed, that SSC is likely to occur at carbon steel if methanol is present in sour wet media. Therefore, the SSC risk of pipeline steel in methanol and aqueous methanolic solutions was tested with tensile probes under 16 bar H2S and 16 bar H2S + 8 bar CO2. In the absence of corrosion inhibitors the steel suffered severe SSC which, however, could be
prevented with selected corrosion inhibitors. The oxgen contained in the technical grade methanol used in the experiment, but also in the service, increases the corrosion severity of the methanolic systems significantly.
Keywords: methanol, wet sour gas, hydrogen sulphide, carbon steel, linepipe steel, hydrogen, sulphide stress cracking, SSC, SOHIC,
inhibitors