Report focusing on best practice methods to establish baseline levels post operational activity. SECURe - Subsurface Evaluation of Carbon capture and storage and Unconventional risks. D3.2

Establishing a post-operational monitoring baseline for detection of induced/triggered (anthropogenic) seismicity is not straight forward. Ideally, a baseline of natural seismicity is established in the undisturbed subsurface and before any operational deployment. If not the case, an alternative approach should be pursued to compensate for lack of pre-operational data.

The present report suggests the approach, to establish a micro-seismicity post-operational baseline by measuring in similar geology under a similar tectonic regime and compare the undisturbed site with the site in operation. The method might however, only be applicable in areas with a relative high level of natural seismicity in order to minimize uncertainties in noise levels.

The approach is tested in the SECURe project, where ongoing micro-seismic data acquisition is deployed around an operating natural gas storage facility in Denmark. The acquired data can be compared with an existing pre-operational micro-seismic baseline obtain at a drilling test site for shale gas. The drilling site is approximately 200 km from the gas storage facility, but the geology is similar. Data acquisition will be continued throughout the SECURe project.