Equinor hopes for a dry well near Troll, for potential CO₂ storage

OSLO - For the first time, an exploration well is being drilled in the North Sea where the objective is not to find oil or gas.

The well is being drilled south of the Troll field in the North Sea, and the objective is to investigate whether the reservoir in the deep Johansen Formation is suitable for storage of carbon dioxide (CO₂).

The Northern Lights project, consisting of Equinor, Shell and Total, is drilling wildcat well 31/5-7 Eos. The West Hercules rig is responsible for the operation.

This will be the first well to be drilled in exploitation license 001, and the objective of the well is to prove sandstone and the storage potential for CO₂ in the Cook and Johansen geological formations. The companies also want to examine the sealing properties of the overlying Dunlin shale.

May be suited for CO₂ storage facility. If the well indicates good reservoir properties, and a decision is subsequently made to use the formations for CO₂ storage, the first CO₂ injector will be drilled as a sidetrack from the wildcat well.

“If the well proves sandstone with good flow properties, this part of the Johansen Formation may be well-suited as a storage facility for CO₂”, says Assistant director exploration Wenche Tjelta Johansen.

She says that the Johansen Formation is situated at a depth of around 2700 meters in the relevant area, and that the wells previously been drilled down into the formation are located on the Troll field, far from this well location.

Long experience with safe CO₂ storage. The Troll reservoir is situated around 600 meters higher up in the stratigraphic sequence, and there are many tight layers of shale between the reservoir and the Johansen Formation. It’s important to investigate the tight shale layers in order to be certain that the CO₂ will remain in place.

“In Norway, we have lots of experience and good expertise when it comes to safe storage of CO₂ under the seabed,” says Johansen.

Since 1996, CO₂ has been removed from the Sleipner Vest gas and injected in the Utsira Formation. One million tons of CO₂ are stored in the subsurface every year. Since 2007, 700 000 tons of CO₂ per year has also been stored at the Snøhvit field. It is separated from the gas in the process facility on Melkøya before it is sent by pipeline down into a reservoir located around 140 kilometers from land. Regular surveys are performed to monitor how injected CO₂ fills the storage area.

Storage atlas. The Norwegian Petroleum Directorate has mapped areas that may be suitable for safe, long-term storage, an endeavor which resulted in a CO₂ storage atlas for the Norwegian shelf. Estimates showed that, in theory, the reservoir volume on the shelf could accommodate more than 80 billion tons of carbon dioxide, which is equivalent 1000 years of Norwegian CO₂ emissions at the current level.

The Northern Lights drilling is part of the Norwegian full-scale project for capture, transport and storage of CO₂ (CCS). This project includes capture of CO₂ from two industrial firms in Eastern Norway, as well as transport of liquid CO₂ to a terminal in Western Norway. From there, the liquid CO₂ will be transported via pipeline and pumped into a reservoir at a depth of nearly 3000 meters under the North Sea where it will be permanently stored.

The full-scale project is a result of the authorities’ ambition to demonstrate a full-scale value chain for CCS in Norway by 2024.

A lot of technical work. Since the objective of this well is to store CO₂, it is being drilled according to the CCS regulations for transport and storage of CO₂. The NPD has been involved in the preparations for the drilling, “We have performed a lot of technical work in connection with the storage project, and we have had regular meetings with the operator,” says Johansen.

The authorities gave Equinor and its partners an exploitation license for storage of CO₂ in January this year. According to the plan, Northern Lights will submit a Plan for development and operation (PDO/PIO) in the spring.

If the development plan gets a green light, Northern Lights has made a commitment to store 1.5 tons of CO₂ for the authorities, every year for 25 years.