The EU Guidance Documents distinguish three different monitoring categories: i) mandatory monitoring that is required for all sites, ii) required site-specific monitoring, and iii) optional contingency monitoring. The EU CCS Directive does not specify which methods or monitoring technologies should be used, but requires that the choice is based on the best practice available at the time of design. A good monitoring strategy should include plans for intensified monitoring in the event of irregularities. Plans are required to be reviewed and updated on a regular basis.

Two examples of site-specific monitoring plans for future potential storage sites are given here:     
Example A is a deep saline aquifer which is a prospective storage site in the south of Romania. Modelling work has indicated that the reservoir can store up to 1.5 Mt CO2 per year for at least 20 years. Site-specific risk assessment has been performed. Monitoring techniques to mitigate the identified risks are proposed. The target compartments for monitoring are ground surface, groundwater, soil, wells, possible faults and air. The suggested methods include logs, seismic surveys, cross-well techniques and microseismic surveys.

Example B is a depleted gas field in Slovakia at the border with Austria. Since this is a depleted field, the present irregular network of 35 old boreholes from hydrocarbon exploration and exploitation and the Láb fault systems need particular attention in the monitoring plan. Geochemical and geophysical monitoring to establish a baseline before injection starts, monitoring during the injection phase and for the post-injection period are recommended for this site. The methodology proposed follows the monitoring plans implemented for depleted natural gas reservoir projects currently in operation, in particular the Otway Project in Australia.

According to Article 13 in the EU CCS Directive, all Member States shall ensure that the operator of a CO2 storage site monitors the injection facilities, storage complex and surrounding environment, based on a monitoring plan. Minimum criteria for establishing and updating the monitoring plan are given in Annex II of the Directive. The monitoring plan should be based on the site-specific risk analysis as required in Annex I of the Directive and provide details for the monitoring during all major stages of the project, including baseline, operational and post-closure monitoring (cf. Annex II of EU CCS directive, 2009). The plan must, inter alia, include details of parameters monitored, technology employed, and sampling frequency in time and space for each project phase.

The monitoring concept for a given CO2 storage site must be chosen according to the environmental and geographical conditions and extent of the underground geological formation, the effects each method may have on infrastructure, environment and human health in short and long term, the effects on existing business and industry in the area and the cost and effectiveness of the methods. Surroundings, surface and subsurface conditions, and local infrastructure vary and site-specific monitoring plans are required. The monitoring plan must be updated regularly to take into account changes related to the assessed risk of leakage, impacts on the environment and human health; new scientific knowledge; and improvements in best available technology. Updated plans shall be re-submitted for approval to the competent authority.

Acquiring baseline data regarding CO2 that may be present in the system before CO2 injection starts is very important. Any natural or industrial CO2 sources and fluctuations in observed CO2 levels at surface must be quantified to establish a baseline. In addition, a good monitoring concept should be flexible and designed to respond to unforeseen events and changes in the project development.

Fig. 4-1 shows a generic workflow for assessment, monitoring and verification in a CO2 storage project that is taken from the eu-funded CO2ReMoVe project (Wildenborg et al., 2009).

FIG 4.1

Fig. 4-1: Generalised workflow for assessment, monitoring and verification purposes (after Wildenborg et al., 2009).


in depth

4.1 Mapping of relevant areas

The EU CCS Directive requires that the storage site operator monitors the injection facilities, the storage complex and,...

4.2 Definition of monitoring objectives and intensity

According to the EU CCS Directive, the main objectives/purposes of monitoring are to: i) assess whether the injected CO2...

4.3 Selection of methods and specification of measurements

The EU CCS Directive does not specify the method or monitoring technology that should be used, but requires that the cho...

4.4 Examples

Whereas general monitoring concepts provide a high-level framework for setting up site-specific monitoring programmes an...