51313-02663-Evaluation of MIC Contribution to Underdeposit Sludge Corrosiveness in a Heavy Crude Pipeline

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Product Number: 51313-02663-SG

ISBN: 02663 2013 CP

Author: Brendan Crozier

Publication Date: 2013

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Due to their low water contents and high flow rates crude oil transmission lines have generally had a low incidence of internal corrosion problems. Recent experience however has shown that internal corrosion can occur at locations within these lines which facilitate the deposition and accumulation of solids such as at elbows and over bends. The deposits that form often referred to as sludges are composed of varying combination of hydrocarbons sand clay corrosion by-products biomass and water. The composition of the sludges can vary greatly between different pipelines and even within the same line leading to great variation in the severity of underdeposit corrosion from location to location. The sludges are known to accumulate and concentrate water from the oil and often act as substrates for the formation of bacterial colonies creating conditions conducive for Microbial Induced Corrosion (MIC).The role of MIC on the overall corrosivity of sludges is often ambiguous as the sludges rich in water are themselves corrosive.

The results of six-month long term experiments used to determine the influence of microbial populations on the overall corrosivity of a particular pipeline sludge will be presented. Sludge obtained from an uninhibited heavy crude oil transmission line was acquired and characterized. The sludge was used to cover steel coupons recessed in sample holders which were then covered in a heavy crude oil under anaerobic conditions. Sludge and coupons were extracted at 30 day intervals to determine the severity of corrosion on the coupon surfaces and to determine the bacterial activity of the sludge. The sludge was tested in an as-received state in a sterilized state which was done through irradiation with ?-rays and in an enriched state meant to selectively promote the activity of Sulfate Reducing Bacteria (SRB) which are often associated with MIC.