2.1.1 Local environmental risks related to CO2 storage operation

The assessment of local environmental risks, such as: permeable zones in the storage formation seal; leakage through undetected faults; leakage via wells; regional scale over-pressurisation; exceeding reservoir spill point and earthquake induced fractures, are necessary considerations when preparing a monitoring plan, which a major input for a storage permit application (DNV, 2009). During storage operation potential environmental risks are carefully monitored and the interpreted monitoring data is used to determine site performance and compare it to the predicted behaviour.

If the comparison/deviation is within a predefined range, the results are used to update the geological model as well as the monitoring plan (every five years as a minimum requirement). The competent authority reviews the storage permit using the monitoring and performance verification results. However, if any serious deviation from predicted behaviour is detected, in other words "significant irregularity", this must be reported to the competent authority. Preventive and corrective measures, according to the plans in the storage permit as well as on-going consultation with the competent authority, must take immediate action. Monitoring and corrective measures are closely interlinked and the plans and activities should be developed by the operator in a holistic manner along with the risk assessment. The competent authority should seek to ensure close integration between these measures. The deployment of corrective measures is required in the event of leakages or significant irregularities, and these would usually be detected by monitoring results or the interpretation of monitoring data or inspections. In addition, monitoring is used to assess the effectiveness of corrective measures, and additional monitoring activities may be required in event of any leakage or significant irregularities. According to the EU CCS Directive (2009), the occurrence of significant irregularities may result in the withdrawal of the storage permit.