This chapter addresses the final stage of a well’s life—plug and abandonment (P&A)—focusing on the permanent restoration of subsurface and surface barriers to prevent fluid migration, environmental contamination, and future liability. Proper P&A operations are critical for long-term integrity, regulatory compliance, and public trust, especially in the context of increasing attention to orphaned and legacy wells. The chapter begins by introducing the regulatory and environmental drivers for well abandonment, referencing international standards (e.g., NORSOK D-010, API RP 17W, ISO 16530-1) and country-specific regulations. The importance of permanent barriers to isolate permeable formations, prevent crossflow, and ensure caprock sealing is emphasized. Next, the chapter outlines the design philosophy of permanent barriers, including the placement of mechanical plugs (bridge plugs, cement retainers) and the formulation of abandonment-grade cement slurries with long-term durability. Topics covered include: Operational methods for well section milling, cutting and pulling casing strings, and setting cement plugs are explained, along with the conditions requiring section milling versus casing perforation and squeeze. The use of resin-based sealants, bismuth alloys, and geopolymers as novel P&A materials is introduced to address long-term chemical degradation concerns. The chapter also explores challenges in abandoning complex wells, such as those with sustained casing pressure (SCP), inaccessible annuli, or old completion hardware. Risk-based approaches and adaptive designs are discussed to address uncertain well conditions. The chapter further reviews offshore P&A practices, which require severing wells below the mudline and restoring seabed integrity, often with specialized subsea tooling. Finally, the chapter stresses the importance of P&A documentation, regulatory reporting, and post-abandonment monitoring, including the use of surface markers, cement tagging, and environmental surveillance to ensure that abandonment is permanent and verifiable. Through diagrams, case studies, and global best practices, this chapter equips engineers with the knowledge and tools needed to execute effective and compliant P&A operations that protect both the environment and stakeholder interests in perpetuity.

Plug and Abandonment (P&A) for Permanent Integrity

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发表日期：

2026年

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Ahmed Alsubaih,
Kamy Sepehrnoori

摘要

This chapter addresses the final stage of a well’s life—plug and abandonment (P&A)—focusing on the permanent restoration of subsurface and surface barriers to prevent fluid migration, environmental contamination, and future liability. Proper P&A operations are critical for long-term integrity, regulatory compliance, and public trust, especially in the context of increasing attention to orphaned and legacy wells. The chapter begins by introducing the regulatory and environmental drivers for well abandonment, referencing international standards (e.g., NORSOK D-010, API RP 17W, ISO 16530-1) and country-specific regulations. The importance of permanent barriers to isolate permeable formations, prevent crossflow, and ensure caprock sealing is emphasized. Next, the chapter outlines the design philosophy of permanent barriers, including the placement of mechanical plugs (bridge plugs, cement retainers) and the formulation of abandonment-grade cement slurries with long-term durability. Topics covered include: Operational methods for well section milling, cutting and pulling casing strings, and setting cement plugs are explained, along with the conditions requiring section milling versus casing perforation and squeeze. The use of resin-based sealants, bismuth alloys, and geopolymers as novel P&A materials is introduced to address long-term chemical degradation concerns. The chapter also explores challenges in abandoning complex wells, such as those with sustained casing pressure (SCP), inaccessible annuli, or old completion hardware. Risk-based approaches and adaptive designs are discussed to address uncertain well conditions. The chapter further reviews offshore P&A practices, which require severing wells below the mudline and restoring seabed integrity, often with specialized subsea tooling. Finally, the chapter stresses the importance of P&A documentation, regulatory reporting, and post-abandonment monitoring, including the use of surface markers, cement tagging, and environmental surveillance to ensure that abandonment is permanent and verifiable. Through diagrams, case studies, and global best practices, this chapter equips engineers with the knowledge and tools needed to execute effective and compliant P&A operations that protect both the environment and stakeholder interests in perpetuity.