Sour Weight Loss Corrosion Management: An Extensive Review of Present Field Experience

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Abstract A wide review of field experience on Sour Weight Loss Corrosion (SWLC) is summarized in this paper, from 127 distinct field cases documented either from in house experience or external sources covering oil and gas producing facilities, wells and surface facilities. This gives access to a large practical background and to quantitative information which allows better documenting corrosion rates, discriminating corrosion factors and lastly recommending consistent mitigation solutions. It is shown that SWLC is frequently much lower than Sweet corrosion in comparable operating conditions except for the H2S content. Unfortunately there are specific and still not easily predictable conditions which may lead to very severe localized corrosion. Although quite rare, these cases are impressive as corrosion rates are currently above 10 mm/yr, even in apparently mild conditions. Leading and secondary corrosion factors are brought out from this analysis. The flow velocity and flow regime are shown to be the most leading factors of the transition between negligible and intermediate and severe corrosion categories. It is also highlighted that very severe corrosion cases require "pit promoters" (sulfur, oxygen, bacteria…) and a galvanic effect with surrounding non corroding surfaces. It is now needed to better understand key SWLC mechanisms before pretending assuring a reliable SWLC prediction over the whole range of possible operating conditions of our future sour fields. This is now the next step of this long term activity on SWLC. Nevertheless this review already allows defining preliminary criteria to classify any application between the 3 given categories. At the same time it provides a number of possible "analogues" to new developments. The definition of leading corrosion factors is also used along this paper to introduce the most appropriate mitigation solutions. It is particularly outlined that mitigation solutions on C Steel facilities must be as much focused on the avoidance of detrimental factors such as oxygen, sulfur, solids, bacteria, dead legs and on the promotion of sufficiently high flow velocities … as on chemical treatments.