Corrosion Management Challenges of Non-Piggable Pipelines, Sections & Dead Legs

Abstract

Abstract Most operating oil and gas companies possess pipeline assets and In-line Inspections (ILI) are the most effective ways to assess the integrity of a pipeline. However to carry out ILI the pipeline should be piggable. Asset integrity audits have identified that while main pipelines are piggable most inter connectors, branches and by-passes are not in the pig’s path. Some sections while no longer in use, are still connected with the live system. These sections may be used rarely and therefore not an operational priority. However these ‘weak links’ pose a major threat to overall system integrity. Many of these non-piggable pipelines do not have a corrosion control strategy and the technical integrity of most is unknown. This has been identified as a high integrity risk to operating companies with respect to loss of production, high cost of failure/degradation and high failure safety risk. As part of the technical integrity drive and risk management strategy, a need was identified to develop the strategy to assure the integrity of non-piggable pipelines / sections. A thorough technical analysis made with advantages and limitations of available integrity assessment methods for non-piggable pipelines, such as: Hydrostatic Pressure Testing, External MFL Survey, Long Range Ultrasonic Thickness (LRUT) and Corrosion Direct Assessment (CDA). Based on the analysis, the most effective and techno-economic solutions were recommended and adopted by Dolphin Energy for its on-shore pipeline network in the UAE namely LRUT. Dolphin Energy operates approximately 750 Km of gas transmission and successfully completed an LRUT inspection project - Phase-1 in 2012 comprising 9 locations and Phase-2 in 2014 - comprising 52 locations throughout the UAE. Post project assessment was made where LRUT inspection and corrosion direct assessment results were analyzed together. Post assessment specifically addressed the effectiveness of methods used, corrosion root cause analysis, a corrective action plan, remaining life calculations and determination of re-assessment interval of each non-piggable pipeline. This paper addresses the new strategy developed and successfully implemented by Dolphin Energy to address the challenges associated with these non-piggable pipelines, sections and dead legs. Through this paper other operating companies who face similar challenges will benefit from the experiences of Dolphin Energy.