STUDY OF CORROSION PATTERN IN GAS DEHYDRATION SYSTEM HANDLING SOUR GAS

摘要

The Gathering Centers (GCs) process crude oil from the oil wells to separate out gas and produced water. Some of the GCs handle very sour crude that is flowed from certain sour oilfields. The separated gas in the GC is compressed in multiple stages and then processed in various parallel trains of glycol dehydration units to remove the moisture before being exported. Recurring failures due to severe corrosion were reported in some of the heat exchangers in carbon steel material in all the trains of the dehydration units in two of the Gathering Centers. When further investigated, it was found that trains had undergone significant deterioration due to corrosion and some equipment were found choked with enormous amounts of black powder deposits. Accordingly, failure investigation was initiated to find out the causes of these failures in the dehydration units of the GCs. Corrosion products were collected for chemical composition analyses. In addition, fluid analysis was carried out. A corrosion pattern was established along the gas dehydration circuit, which revealed mainly the presence of iron sulphides with varying stoichiometry along with elemental sulphur, iron sulphate, iron oxide and hydroxides. This paper presents few of the findings based on the analysis of the corrosion products deposits within the failed components and discusses the possible corrosion mechanisms.