Title : Pipeline integrity under challenged operations: Restoring reliability in a 20” main oil line through root cause driven mitigation
Abstract:
Background and Integrity Challenge:
This paper presents a comprehensive pipeline integrity investigation and recovery strategy for a 20” Main Oil Line that experienced severe internal corrosion following prolonged operation in by-pass mode. The objective is to identify the root causes of accelerated metal loss, evaluate gaps in operational and corrosion management practices, and demonstrate how a multidisciplinary, integrity led intervention successfully restored pipeline reliability and fitness-for-service.
Investigation and Systematic Approach:
A structured root cause analysis (RCA) was executed through a Joint Task Force, integrating in-line inspection (ILI/IP) data, operating history, corrosion risk assessment (CRA) limits, chemical performance reviews, and well operation practices. The analysis focused on flow regime deviations, water chemistry (pH), solids and debris deposition, inhibitor delivery effectiveness, and deferred mechanical pigging. Mitigation strategies were then developed and implemented across corrosion management, well operations, and integrity assurance, supported by enhanced pigging technologies, high-resolution inspections, and verification techniques such as AUT on critical features.
Performance Outcomes and Key Findings:
The integrated mitigation program resulted in a dramatic reduction of internal corrosion rates from approximately 3.5 mm/year to 0.1 mm/year, confirming the effectiveness of restoring operation within the defined integrity operating window. Key conclusions highlight that prolonged low-flow operation, under-deposit corrosion, acidic produced water following well stimulation, and ineffective inhibitor distribution were the dominant contributors to the observed damage. Recommendations emphasize strict adherence to CRA-defined operating envelopes, proactive debris management, aggressive cleaning pigging, controlled well fluid diversion, and continuous integrity monitoring to prevent recurrence.
Engineering Significance and Industrial Application:
This case study provides a rare, data driven demonstration of how temporary operational modes when extended beyond their original intent can rapidly compromise pipeline integrity if not governed by robust monitoring and multidisciplinary oversight. The work highlights the critical role of advanced pigging configurations (dual-module brush pigs with magnets), batch inhibition strategies post-pigging, and cross-functional MOC governance. Lessons learned have been formally captured and disseminated across ADNOC group assets, offering a transferable integrity framework applicable to similar brownfield and early-production pipeline systems.
