05.09.2023

HNET: “Live” monitoring of CO₂ storage under the seabed

The HNET project develops a unique method based on knowledge and technology that already exists.

Measuring seismicity in real time is one of the few monitoring methods that can continuously provide a picture of how the stress in and around the storage site may change, and thus can say something about the risk of leakage

What is HNET?

HNET is a CLIMIT supported research and technology development project aimed at developing and demonstrating a baseline seismic monitoring network for offshore CO₂ storage in the Horda platform region of the Norwegian North Sea.

The project is focused on improved assessment of natural seismicity in support of planned CO2 storage projects on the Horda Platform region. t is focused on understanding natural background seismicity before starting the actual injection.

Kystlandskap med hav, holmer og vegetasjon sammen med en liten landbasert lyttestasjon som ser ut som to paneler og en liten boks. Foto — Real-time data collection. Photo hordanet.no

Establishing knowledge of background seismicity

The HNET project is led by Equinor, with partners NORSAR, Shell, TotalEnergies, Northern Lights JV, University of Bergen, Norwegian National Seismic Network (NNSN) and CGG. The project is divided into five phases, with decision gates between the phases (see fact box).

Own onshore seismic array

In the current phase, routine operation of the HNAR onshore seismic array (on land at Holsnøy) will be established. The data from HNAR will be integrated with available data from offshore probabilistic roadmap (PRM) nodes from Grane, Oseberg and Snorre.

In the summer of 2021, seismometers were deployed on the seabed (in the Aurora prospect, i.e., the storage location for the Northern Lights project). They were deployed for a year. The data from these nodes was recorded continuously and then incorporated with other recordings from offshore PRM nodes and onshore arrays.

An important part of this project is seismic risk assessment, data integration and information. This should be made available quickly and in an expedient manner, adapted to others than just the subject experts.

– We are very pleased with the data from the onshore array, says Volker Oye (Research at NORSAR)

Phases in the HNET Project

Phase 1
(SNS-NET Project) was carried out in the period August 2018 to July 2019.

Phase 2
(HNET) took 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 from November 2019 to December 2020.

Phase 3
HNET3 is the ongoing project that will form the basis for the understanding of all natural, tectonic seismic activity before CO₂ is injected into the ground in the Northern Lights project.

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

Phase 5
This phase is an information and reporting phase and runs parallel to Phase 3.