1.3.3 Operational monitoring

For the purpose of storage operation, the focus of monitoring is on the storage reservoir and the caprock. Early detection of leakage may be in time to take actions to prevent leakage to the surface that would cause HSE risks or require monitoring according to the ETS. Therefore, operational monitoring aims at processes of fluid migration at depth. Indications of leakage may be derived from a variety of parameters that can be measured in the subsurface, without measuring actual concentrations or fluxes of substances. Mainly physical parameters are considered, such as pressure or temperature recorded in observation wells or geophysical investigation of larger rock volumes.

The operator faces a variety of risks, in addition to HSE risks that ultimately are financial risks. He may monitor the corrosion of well materials for maintenance and work-over measures or near-well reservoir properties in order to maintain sufficient injectivity for CO2.

The impact of possible disturbances in storage operation is inversely proportional to the chances for precisely localising a problem and to the chances of successful remediation of the problems. For example, leakage through well bores likely could be fixed. Leaking cap rocks would be classified as serious impact that could endanger storage permits.