Geologic storage of CO2 has gained significance, largely due to it being a green-house gas (GHG) and concerns related to impacts on climate from GHG emissions. The literature and experience from industrial analogs indicate that wellbores (both active/inactive or abandoned) may represent the most likely route for escape of the injected CO2 from the storage reservoirs. Therefore, sound injection well design and life cycle well integrity of all wells is of critical importance in such projects, particularly from a storage perspective of 1000 years or more.
Challenges related to safe long-term CO2 storage and its economics, principally in deep saline formations and to a lesser extent in depleted oil and gas reservoirs, can be broken down into two main categories: (1) Well integrity challenges and (2) Injectivity or Regularity challenges. This presentation will present key engineering factors that have to be addressed from a well integrity (primary) and injectivity/injected volume (secondary) perspective to enable a CO2 geologic storage project to be a success.
In a CO2 injection well, the principal well design considerations include pressure, thermal stresses, corrosion-resistant materials (tubulars and cements) and injection rates. Proper maintenance of CO2 injection wells is important to avoid loss of well integrity. Plugging and abandonment procedures (and risks from legacy wellbores) are also important to ensure that the injected CO2 will not escape out of the stored reservoir and are adequately addressed with sound engineering practices and regulatory compliance. Industry experience, particularly with CO2 EOR, natural gas storage and acid/sour gas wells shows that new CO2 storage injection wells can maintain life cycle well integrity if designed, constructed, operated and monitored as per current state-of-the-art design specifications (e.g. use of WELLCATTM, DrillPlanTM, and other in-house proprietary software) and regulatory requirements.
