Project of quantitative risk analysis for designs of permanent abandonment of wells

On the Norwegian Continental Shelf, thousands of wells are approaching the end of their productive lifetime during the coming decades. Permanent well abandonment requires establishing cross-sectional barriers of a certain length that prevent cross-flow of fluids and do so indefinitely. As the condition of the original well cement can be uncertain or difficult to establish, limitations in current technology implies that expensive installations are often required for a considerable part of the plug and abandonment (P&A) operation. Finding more efficient, cost-effective and safer methods for well abandonment is of great importance for the industry and the society. Ideally, a P&A well design should lead to a leakage risk that is as low as possible, while keeping the time and cost of achieving this also as low as possible. A risk-based approach to P&A should reflect the well-specific risk of leakage in the abandonment design, covering both barrier verification and barrier length, thereby allowing optimized abandonment design and the possibility of evaluating alternative P&A well designs and technologies. Risk-based approaches to P&A are under development, but to fully enable such an approach there is a need to better understand well barrier performance, limitations and capabilities of current verification methods, and also a need to define acceptance criteria that consider both performance, verification and possible environmental consequences of leakage. The main objective of this project is to further strengthen the risk-based approach to P&A by addressing these knowledge needs through a close collaboration with Brazilian partners. This project, together with its connected project in Brazil, will develop models supporting a risk-based approach as well as demonstrate and evaluate the applicability of the approach on cases, covering both Norway and Brazil.