CO2 Storage – what, why and how?

We asked Gøril Tjetland, our CO2 storage expert to give us some insight on the subject.

Gøril grew up on a farm and learned from early days the value of looking after nature and our surroundings. – It’s all about passing the land on to the next generation in the same or better shape, she says.

Gøril has worked in the oil and gas industry for years, both on the NCS and in the Middle East. She is specialized in Applied Earth Sciences (Civil Engineer/M.Sc. from NTNU).

She has always been engaged in how to contribute to finding a better balance between our oil and gas production and emissions. She has worked for environmental organizations, lobbying emission cuts before she started working with a specific solution to store CO2 in the same types of rocks where we find oil and gas: Called (Geological) CO2 storage.

1. In simple terms; What is CO2 storage and how is it done?

CO2 storage is the only way to remove significant volumes of CO2 from the atmosphere. CO2 is created by burning fossil fuels in the first place. That fossil fuel is carbon that has been buried in rocks for tens of millions of years (in Norway most oil and gas we produce are generated from algae that was buried more than 100 million years ago).

When we inject CO2 into rocks in the subsurface we are using the same technics and technology as when we extract oil and gas from rocks in the subsurface.

2. How are storage sites selected?

Storage can take place both underground on land and offshore. Before selecting a storage site, however, it is necessary to make sure that once injected, the CO2 will not leak out. Safe and effective storage sites are marked by the following characteristics:

• Storage formations, such as sandstone, must be capable of receiving CO2. This requires sufficient pore space, tiny water-filled gaps between the grains of the rock

• Pores in the rock are connected well enough, a feature called ‘permeability’, so that the CO2 can move and spread out within the formation, providing the capacity needed to accept the necessary amount of CO2

• Formations must have an extensive cap or barrier at the top to contain the CO2 for thousands of years and longer (basically forever)

3. What type of stone represents the safest form of CO2 storage?

Deep saline aquifers, which are to be found all over the world, represent the largest potential CO2 storage capacity in the long term.

An aquifer is porous sandstone where water is present naturally in the pores in the sand. If CO2 is injected it can occupy the pores just like water does, or it can even be dissolved into the water.

As time goes by the CO2 will start to dissolve in the water. This naturally occurring process lowers the risk of leakage because the water has already been trapped in the aquifer for millions of years.

After several thousands of years, the CO2 will react with other minerals and form solid rock, which is the safest form of CO2 storage.

4. What are the legal requirements regarding CO2 storage?

EU developed a directive for CO2 storage in 2009 that was implemented in almost all Member States by 2013. These requirements cover everything from the screening and preparation of a storage site to the responsibilities minimum 20 years after you seize operations. After this post-closure verification period the national competent authority take over the responsibility of the abandoned storage site.

In Norway this directive was implemented in 2014: «Forskrift om utnyttelse av undersjøiske reservoarer på kontinentalsokkelen til lagring av CO2 og om transport av CO2 på kontinentalsokkelen».

It is important to note that CCS shares many legal, planning, technical and operational similarities with underground gas storage, a process which has been carried out worldwide for almost 100 years. While underground natural gas storage is safe and effective, some projects have leaked, mostly caused by poorly completed, or improperly plugged and abandoned wells or by leaky faults.

5. How is Ross Offshore an asset to your clients in CO2 storage? What competence to you bring?

Our strengths are our capacity to provide a careful and complete storage design and site selection. Specifically, this means that we build a dynamic model early on to understand the subsurface pressure development and migration of CO2 and we also have a close integration between our subsurface department and our drilling and well department. Often the weakest point of a storage site are pre-existing wells that are plugged and abandoned and these need to be addressed early on.

Ross Offshore has extensive experience from the CCUS (carbon capture use and storage) industry, going back to 2008. Ross Offshore was then awarded the role as Owner’s Engineers for Gassnova SF, which administrates the Norwegian authorities’ interest within CCS. Since 2008, Ross Offshore has been involved in various CCS projects; on both academic and industrial levels, for assessing safe storage of CO2 in aquifers and in depleted oil and gas reservoirs, and as an independent reviewer. We have been involved with clients operating on the Norwegian and UK continental shelf, but also international companies. Typically, the work we do is associated to applications for an official license to store CO2.

There is already considerable experience with injecting CO2 deep underground for storage at a number of CCS projects. These storage sites have been carefully selected and monitoring evidence concludes that the CO2 has been completely and safely locked into the geological formations. Careful storage system design and site selection, together with methods for early detection of leakage (preferably long before CO2 reaches the land surface), are effective ways of reducing hazards associated with diffuse leakage.

6. Who are typical clients for CO2 storage?

Typical clients are oil and gas (or energy) companies.

7. What is the first step in the process?

Addressing the storage capacity of the storage formation and the sealing formations, together with an assessment of the overburden and potential leakage pathways.

Then we tailor the work to document further uncertainties and unknown parameters. We try to get a complete picture of the storage complex in order to address its suitability as a CO2 storage and estimate storage capacities.

8. What is the best part about your job?

Interaction between several disciplines. My colleagues, my fellow Ross Stars ⭐️

9. How do you see the market now and the next couple of years?

Short-term slight halt due to intense focus on increased gas production these days, but medium-term a clear increase. We see a significant increase of new players and clients within CO2 storage. In particular from the UK sector.

International, EU and national climate obligations cannot, realistically, be met without CO2 storage so we see an increased interest also from countries and parts of the world which previously did not consider CO2 storage. If hydrogen production is rolled out on a larger scale the demand for safe CO2 storage will also increase.

10. Gørils fun facts:

⭐️ Did you know that some sorts of paper can hold up to 60% of rocks?

⭐️ Humans can not breathe air that holds more than 5% CO2 or live in temperatures above 43 degrees. And it gets challenging long before that.

⭐️ In a geological perspective, masse death and destruction is not uncommon. 400 million years ago 70-80% of all species died, 65 million years ago 65% of all species died. The globe survives, the people don’t.

⭐️ Gøril is more than a CO2 Storage Expert; She is soon to be a mother of four, loves to climb and has a bachelor in literature.