CO₂ Injection and Storage into the Utsira Formation, North Sea - Risk Evaluation

Helga Hansen¹, Ola Eiken², and Rolf Håkon Holmboe^1
1Statoil ASA, Stavanger, Norway
²Statoil, Trondheim, Norway

The largest gas/condensate field in the Sleipner area, the Sleipner Vest Field, contains 9 mole% CO₂. The excess amount of CO₂, extracted by an offshore amine based plant, has been injected and stored some 800-1000m below sea level and 2.5 km east of the Sleipner A platform in the Utsira Formation - a water-filled aquifer. During the last ten years about nine million tonnes of CO₂have been injected.
The Sleipner licence group have focused on the impacts the CO₂injection and storage may have on the Sleipner area itself, other licences and long term performance.
A group of experts, including independent international expertise, was invited to a risk work shop spring 2006. The objectives of this workshop were to: • Identify risks of CO₂escape, particularly through adjacent wells and across licences boundaries within Utsira Fm. • Identify mitigating measures • Verify that the risk level related to today's injection activity is acceptable based on the risks identified together with the proposed mitigating measures
Some risk factors were identified, and none of them were considered unacceptable. A selection of mitigating measures to reduce risk and improve control of the CO₂plume was identified: • Continue monitoring the CO₂plume using time lapse seismic surveys • Build and history-match a new reservoir simulation model to update the CO₂migration prognosis • Develop a monitoring and action plan for the nearby wells • Continue studies of the cap rocks ability to provide an efficient, long-term seal

 

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece