Internal Corrosion Direct Assessment for Hydrocarbon Service Petroleum Pipelines

Abstract

Contaminants such as CO2, H2S and O2 in water-wet liquid and gas pipelines create an aggressive environment conducive to facilitating internal corrosion. During pipeline operations, solids deposition, water accumulation, bacterial activities and improper chemical inhibition aggravate the internal corrosion attack. For assessing the threat of internal corrosion, the petroleum industry currently has only three integrity validation tools at its disposal. These are Pressure Testing, In-line Inspection (ILI) and Internal Corrosion Direct Assessment (ICDA). To enhance pipeline integrity for piggable and non-piggable pipelines, NACE International has developed and published a variety of industry consensus Standard Practices for the ICDA protocols to predict time-dependent internal corrosion threats for various petroleum products in both offshore and onshore under sweet or sour environments. These NACE International ICDA Standards include: • SP0206-2006 “ICDA Methodology for Pipelines Carrying Normally Dry Natural Gas (DG-ICDA)”[1] • SP0208-2008 “ICDA Methodology for Liquid Petroleum Pipelines (LP-ICDA)”[2] • SP0110-2010 “Wet Gas ICDA Methodology for Pipelines (WG-ICDA)”[3] • Multiphase flow (MP-ICDA) is under development with TG-426 and will be released in 2013. • Process Piping (PP-ECDA, Above Ground) is in its early stages of development with the release not likely before 2015. • Process Piping (PP-ECDA, Buried) is in its early stages of development with the release not likely before 2015. • Process Piping (PP-ICDA) for various service environments is in its early stages of development with the release not likely before 2015. All ICDA protocols are a structured, iterative integrity assessment process, consisting of the following four steps: Preassessment, Indirect Inspection, Detailed Examination and Postassessment. Most importantly, unlike ILI and pressure testing, all the ICDA standards require a mandatory root cause analysis and a go forward mitigation plan to arrest the corrosion processes being encountered. This paper reviews the following case studies: LP-ICDA for a crude oil pipeline and WG-ICDA for a high pressure gas pipeline with free water and condensate. ICDA is applicable for dry gas systems too but due to limiting length of this paper, the dry gas case study is not detailed. This paper will be useful for the pipeline operators to provide guidance in identifying locations at which corrosion activity has occurred, is occurring, or may likely occur in the future under a series of pre-defined operating conditions.