Demonstration of optimized baseline seismic monitoring network for the Horda Platform region (H-Net project)

Background
As operator of the full-scale project Northern Lights together with partners Shell and Total, Equinor wishes Norsar to demonstrate cost-effective monitoring technologies within the framework of the Norwegian storage regulations. For the past 10 years, Equinor has been an industry partner for several CLIMIT projects to mature the technology around micro-seismic monitoring, and is / has been a partner in the FME centers NCCS, BIGCCS and SUCCESS.

Relevant projects that Equinor has been involved in are DEMODA’s “Distributed seismic monitoring” led by CHRISTIAN MICHELSEN RESEARCH AS and “Induced seismicity geomechanics for controlled CO₂ storage in the North Sea”, led by NGI. Together with NORSAR, Equinor has supported the MIMOSA project for In Salah, the CLIMIT KPN projects SafeCO₂ and SafeCO₂ II. NORSAR has also received support from the CLIMIT demo for the CO₂CAP project and the ACISM project. Through these projects, NORSAR was also involved in the Longyearbyen CO₂Lab activities. HNet is based on the recently completed SNS-NET as well as the idea study “Preliminary study for monitoring the background seismicity for Smeaheia”.

The project is divided into five phases, with decision gates between the phases. Phase 1 (SNS-NET Project) was completed in the period August 2018 to July 2020. Phase 1 has been completed. In the DG1 meeting with Northern Lights, it was decided not to continue with the original proposal for an offshore array distribution. The reason for this is the changed storage location from Smeaheia to Aurora, the modified time frame for the NL project and the costs associated with the offshore node development plans

Phase 2 (this project) takes the concepts further with the implementation of the instrumentation on land and the use of PRM nodes on the seabed and the initiation of data collection and reporting.

Phase 3 will be a pre-operational background seismicity monitoring that forms the basis for all natural, tectonic seismic activity before CO₂ is injected into the ground.

Phase 4 is the last phase, which includes continuous real-time monitoring of the injection process.

Phase 5 is information and reporting and runs in parallel from Phase 3 starts. An audience portal is proposed here.

Project goals:
CO₂ storage project Northern Lights is the world’s first, dedicated large-scale offshore CO₂ storage project. It is important for future projects that the concept is documented safely; that there can be no uncertainty that CO₂ will remain in the subsoil. The monitoring solution in the project is new, but it reuses as much as possible of the partners’ knowledge from offshore oil and gas, from onshore CO₂ storage monitoring and automatic collection and processing from nuclear test blast monitoring. The technology gap that is closing is to establish the world’s first continuous monitoring of an offshore CO₂ storage. A balance between cost and quality becomes important so that one can show the world that this is feasible elsewhere as well.

In every CO₂ storage facility, it is crucial that the security of the storage site and the control over where the CO₂ is located is adequate at all times. Real-time monitoring of seismicity is one of the few monitoring methods that are suitable for continuously confirming the risk of leaks. The Northern Lights project is subject to “Regulations on the utilization of subsea reservoirs on the continental shelf for storage of CO₂ and on the transport of CO₂ on the continental shelf” and the relevant section in relation to the project applied for is § 5-4.

Monitoring (https://lovdata.no/forskrift/2014-12-05-1517/§5-4).

Development of the technology in the project is important to meet the requirements of the paragraph: “The choice of monitoring techniques shall be based on best practices available at the time of design. The following options shall be considered and used if possible: j) Technologies that can detect presence, location and migration path for CO₂ in the subsurface and on the surface, k) Technologies that can provide information on the evolution of pressure and volume and area / vertical saturation of the CO₂ cloud (plumen) to improve numerical 3D simulations related to 3D geological models of the storage formation established according to § 1-10 of the regulations and appendix I, l) Technologies that can cover a wide area to retrieve information about previously undiscovered potential leakage paths over the area dimensions of the entire storage complex and above, in case of significant irregularities or migration of CO₂ out of the storage complex ”