Introduction

IEAGHG currently runs five international research networks on CO₂ geological storage, namely Risk Assessment, Wellbore Integrity, Monitoring, Modelling and Social Research. These networks meet on an annual basis, bringing together experts from industry, research institutions and regulatory agencies to discuss technical issues in the context of Carbon Dioxide Capture and Storage (CCS) deployment. Membership of the networks is open to those with a professional or academic interest in the particular network theme, and allows access to past network reports and presentations through the IEAGHG website, www.ieaghg.org.

The purpose of this report is to describe the Wellbore Integrity Network, summarise past meetings, outline key findings and identify current state of knowledge.

Conclusions

• The network has provided a valuable international forum for discussion of wellbore integrity issues pertinent to CO₂ geological storage since its inception in 2005. The network meetings have presented detailed information from industrial analogues to storage, especially from the oil and gas industry including North American CO₂-EOR and acid gas disposal projects. Statistics on wellbore leakage and failure rates have been presented and discussed, whilst best practice guidelines have been debated.

   

  Research over the last 6 years has greatly improved our understanding of processes linked to potential alteration and degradation of wellbore materials, especially cements. Much of the relevant research is included within presentations made at network meetings.

   

  Presentations and discussions at network meetings have indicated that wellbore integrity issues for new, purpose-built CO₂ injection and monitoring wells should be manageable with appropriate use of best practice guidance, backed by experience from the oil and gas industry. The presence at some storage sites of existing or abandoned wells remains a more complex risk management issue that will require effective monitoring programmes and possibly remediation works, as have been applied at some CO₂-EOR sites.

   

  Quantitative prediction of wellbore integrity over longer timescales, and integration into risk modelling for storage sites, remains challenging and will require continued research effort as the number of large scale storage projects associated with CCS deployment increases over the coming decade.

   

  Although recent network meetings have continued to attract significant numbers of delegates, the steering committee has found increasing difficulty in setting agendas that incorporate new research. This was particularly problematic in 2010, and led to the decision to hold the 2011 meeting in combination with the more recently instigated Modelling Network, which has attracted greater numbers of delegates and volunteers for presentations. On the other hand, there is continued recognition that there remain important research questions in wellbore integrity that create uncertainty in the long-term storage of CO₂.