This chapter investigates the critical challenges associated with achieving long-term zonal isolation in wells undergoing permanent plug and abandonment (P&A). As global regulations evolve to mandate safe and environmentally secure well closures, ensuring the integrity of P&A operations has become a top priority for both industry and regulators. This chapter presents a detailed assessment of failure pathways, material degradation, and design limitations that compromise permanent isolation over decades to centuries. The chapter begins by reviewing regulatory requirements and industry standards (e.g., API, NORSOK, ISO) governing P&A practices, including barrier placement, verification, and abandonment design life expectations. It then explores the physical and chemical mechanisms that can lead to loss of isolation, including micro-annulus formation, casing corrosion, cement shrinkage, and long-term geochemical reactions in the wellbore environment. Special attention is given to the unique challenges posed by legacy wells, orphaned wells, and deep high-pressure/high-temperature (HPHT) wells, where uncertain construction histories and degraded materials complicate effective isolation. Case studies highlight instances of post-abandonment gas migration and fluid leakage, emphasizing the consequences of incomplete barrier coverage or improper verification. To address these challenges, the chapter evaluates advanced abandonment materials, such as self-healing cements, expandable materials, bismuth alloys, and polymeric gels, comparing their sealing capabilities and long-term stability. The role of formation behavior (e.g., subsidence, creep, fault movement) is also addressed through geomechanical models, underscoring the importance of site-specific design. Barrier placement and verification techniques are critically assessed, including ultrasonic logging, cement bond logging, temperature and noise tools, and pressure testing. The limitations of these tools in detecting subtle failure mechanisms or verifying zonal isolation beyond casing strings are discussed. The chapter concludes with forward-looking recommendations for smart abandonment strategies, including digital monitoring of plugged wells, machine learning-based failure prediction, and the integration of sustainability and lifecycle risk into abandonment planning. Together, these insights promote safer and more effective P&A operations that protect groundwater, surface ecosystems, and public safety over geological timeframes.

Failure Modes of Seals, Packers, and Valves

章节
发表日期：

2026年

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Ahmed Alsubaih,
Kamy Sepehrnoori

摘要

This chapter investigates the critical challenges associated with achieving long-term zonal isolation in wells undergoing permanent plug and abandonment (P&A). As global regulations evolve to mandate safe and environmentally secure well closures, ensuring the integrity of P&A operations has become a top priority for both industry and regulators. This chapter presents a detailed assessment of failure pathways, material degradation, and design limitations that compromise permanent isolation over decades to centuries. The chapter begins by reviewing regulatory requirements and industry standards (e.g., API, NORSOK, ISO) governing P&A practices, including barrier placement, verification, and abandonment design life expectations. It then explores the physical and chemical mechanisms that can lead to loss of isolation, including micro-annulus formation, casing corrosion, cement shrinkage, and long-term geochemical reactions in the wellbore environment. Special attention is given to the unique challenges posed by legacy wells, orphaned wells, and deep high-pressure/high-temperature (HPHT) wells, where uncertain construction histories and degraded materials complicate effective isolation. Case studies highlight instances of post-abandonment gas migration and fluid leakage, emphasizing the consequences of incomplete barrier coverage or improper verification. To address these challenges, the chapter evaluates advanced abandonment materials, such as self-healing cements, expandable materials, bismuth alloys, and polymeric gels, comparing their sealing capabilities and long-term stability. The role of formation behavior (e.g., subsidence, creep, fault movement) is also addressed through geomechanical models, underscoring the importance of site-specific design. Barrier placement and verification techniques are critically assessed, including ultrasonic logging, cement bond logging, temperature and noise tools, and pressure testing. The limitations of these tools in detecting subtle failure mechanisms or verifying zonal isolation beyond casing strings are discussed. The chapter concludes with forward-looking recommendations for smart abandonment strategies, including digital monitoring of plugged wells, machine learning-based failure prediction, and the integration of sustainability and lifecycle risk into abandonment planning. Together, these insights promote safer and more effective P&A operations that protect groundwater, surface ecosystems, and public safety over geological timeframes.