Corrosion in the Oil and Gas Industry: An Increasing Challenge for Materials

Important reserves of oil and gas, which are left to be discovered and produced, are mainly concentrated in challenging locations and under severe conditions [i.e., high pressure (HP)/high temperature (HT)]. The HP/HT plus the presence of aggressive environments mean a highly demanding scenario for tubes used in producing oil and gas [oil country tubular goods (OCTG)]. Material property requirements include high mechanical properties at ambient and high temperatures (e.g., as high up to 200-250A degrees C). Additionally, if H2S is present, resistance to sulfide stress cracking may be required, depending also on other environmental conditions. Even without H2S, contents of CO2, chlorides, and high temperatures and pressures can represent a risk of high corrosion rates. The improvement of some of the required properties of the materials (e.g., steels) can mean the impairment of other properties. Consequently, a careful balance is required and limits exist for the individual modification of the properties. The present article focuses on the two main environmental deterioration problems in the oil and gas business: (I) sulfide stress cracking and (II) CO2 corrosion. A description of the acting mechanisms and the effect of environmental and material factors are presented. Selection criteria and current material limitations are also discussed.