Stress field information from seismicity to de-risk large-scale CO2 injections in the North Sea Horda platform region

Abstract

Carbon capture and storage technologies are an essential part of EU’s decarbonisation efforts. Combined with sustainable energy resources, they are necessary to move Europe towards a net zero carbon emissions economy. Currently, several Mt-scale CO₂ storage projects are being developed in the North Sea. Containment risk evaluation includes analysing tectonic earthquake patterns to potentially map faults, reveal their orientation and failure style, invert for stress directions and at later stages, enable the discrimination of natural and induced seismicity. In addition, seismological information may contribute to the geomechanical understanding of the reservoir and caprock response to large-scale CO₂ injection over time.

A wealth of data exists from various European seismological agencies, but much of it has not been analysed collectively. Within the framework of the ACT3 project SHARP Storage, an extensive unique earthquake bulletin was compiled using seismicity data from all relevant data centres serving as a basis for further analysis, including event relocation and magnitude homogenisation. Inverted moment tensors, shear-wave splitting measurements, and stress drop analysis will be compared to and complement a review of borehole stress measurements to better gauge the present-day stress field and provide constraints on geomechanical models. In addition, the seismological data is integrated with geomechanical data, further improving the understanding of the state of stress and how this relates to fault failure and slip tendency.