CO2 storage: Location, location, location!
by Sidsel Lindsø // CEO of ExploCrowd
There is a race going on right now, but most of it happens in the shadows. Why?
Right now, it is possible to access business opportunities in CO2 storage just by moving fast and getting ahead. The situation is of great strategic interest to competing companies. And just as in real estate, CO2 storage is all about location, location, location.
Nerd alert
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Nerd alert –––
Just so you know: It pains a scientist to see CO2 written without the subscript! Carbon dioxide consists of 1 coal molecule and 2 oxygen molecules, and the correct way to communicate this structure is CO-subscript-2. CO2 doesn’t exist. That would be all from the nerd department. Please continue reading!
Virgin reservoirs vs exhausted oil and gas fields
Whereas Norway has solely focused on injecting CO2 in so-called virgin reservoirs for now, other countries such as UK, Netherlands and Denmark have until recently focused only on repurposing old infrastructure to store CO2. One of the obvious benefits of re-using depleted oil and gas fields is that one can delay the decommissioning cost, and because this cost billions of dollars it is clearly a motivating factor to test alternatives.
The advantage of repurposed infrastructure
Injecting CO2 in depleted oil and gas fields, you usually know your reservoir very well through years of production from many wells. This means good confidence in the reservoir properties such as porosity, permeability, temperature, and pressure.
The major challenge: The steel in well bores is created for withstanding oil, gas, and brine water, but CO2 is incredibly corrosive. This means that when old steel meets the CO2 it starts to corrode, and it can go fast. The consequence is that the steel, designed to ensure that whatever is in the ground stays safely in the ground, will be eaten up by rust.
Jeopardising well integrity
Another aspect that many have not yet fully understood when repurposing depleted oil and gas fields is that CO2 also affects existing cement that is used to create a seal in the well bore around the steel pipe, and thereby jeopardise well integrity. Many of the old wells we have investigated in our work have been compromised.
Imagine injecting CO2 at the high rates (which are required for an economic business case) into an existing oil or gas field, building pressure in the reservoir and then the CO2 starts leaking out through one or more of the existing wells that were drilled into the reservoir decades ago? It just cannot happen.
As far as our understanding goes, this challenge has not yet been solved.
Katrine Wienberg, Associated Expert in Drilling Engineering says:
"Oil and gas wells are typically not designed for high concentrations of CO2, and after +30 years of production/injection activity the actual state of the well must be re-assessed, and likely re-completed with higher-grade tubulars, if CO2 injection is considered.
For example, sustained annular pressures is a well-known problem for many producing fields, indicating compromised well integrity.
In addition to this, the long-term effect of dense-phase CO2 on cement is unknown, and special recipes for CO2 wells are being developed and tested as part of new developments."
The advantage of virgin reservoirs
The main advantage with virgin reservoirs is that few wells have been drilled into these reservoirs. This means that you don’t have to worry as much about potential leakage through wells as one has to only secure one or two wells with new well interventions to ensure that leakage doesn’t happen.
The main challenge with virgin reservoirs is that few wells have been drilled into these reservoirs. They can be mapped and identified on seismic data, which is representing an image of the geology in the deep, but there are usually very few well data points to give confidence in the interpretations by geologists and geophysicists. The consequence is that there is equally low confidence in the reservoir simulation models created by the reservoir engineer based on the geological model of the deep underground.
Testing and verification
The inherited uncertainty is the main reason why it often is necessary to drill an exploration well or an appraisal well to:
test and verify that the reservoir and aquifer planned to be used for CO2 storage is as good as you have modelled
test and verify that the seal can hold the pressure that you plan to create with the modelled injection rates.
A well to get these data points costs between 50 and 100 million dollars, so going ahead with a decision to drill such a well is not something that is settled in a short lunch break in the canteen.
Moving towards virgin reservoirs … and from offshore to onshore
As mentioned, Norway has focused on virgin reservoirs. This summer, they were accompanied by UK and Denmark who opened their first CO2 licencing rounds. These have now closed and received 26 and two applications, respectively. The licence round in Denmark was announced with a very short notice and with a very short deadline, allowing only those who already had subsurface expertise and data in the area to work up the area and submit applications for potential future CO2 storage. The licence is however planned to be a yearly event, and more companies can be expected to play a role in the future.
Denmark is also opening up for screening for potential storage of CO2 onshore, which will by far provide the best economic business case, rather than transporting the CO2 far offshore. Onshore CO2 storage has not previously been considered an option by any of the European countries, so this is an interesting development. New actors have already announced their interest.
Will there be onshore CO2 storage in Norway?
For those curious about the opportunities of onshore storage in Norway, I am sorry to disappoint you. It is not possible. Here is why: The mountain chain of Norway pretty much consists of solid rock onshore. The mountains were once as high as the Himalayas, up to eight kilometres, but the six to seven kilometres have been removed by ice, wind and moving water through hundreds of millions of years. Today, leftovers from this erosion forms perfect reservoirs for CO2 storage elsewhere, if they have a solid seal rock.
How easy is it to find a CO2 storage location?
Believe us when we say: Finding a CO2 storage location is not that complicated for geologists who know their backyard.
To identify a CO2 storage location that makes economic sense in a business case is a whole different story, but that explanation will come in the next chapter of our series on CO2 storage.
For those who want to learn more: These are the main CO2 storage projects in northern Europe
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CO2 injection in virgin reservoirs has been used for decades, where the gas and condensate in the Snøhvit and Sleipner fields had too high CO2 concentrations. The solution was to inject CO2 into nearby virgin reservoirs, consisting of good quality sand.
Norway: Sleipner East since 1996
Visit Equinor fact pageNorway: Snøhvit Gas Field since 2008 | 1.9 million tonnes from 2008 to 2013
Visit Equinor fact pageNorway: Northern Lights part of Longship
Visit Northern Lights -
Denmark: Greensand Project focusing on the sand reservoirs of the Nini Field |
Visit GreensandDenmark: Bifrost Project focusing on the chalk reservoirs of the Harald Field | 3 million tonnes in total
Read Offshore Energy articleUK: Acorn
Visit AcornNetherlands: Porthos | 2.5 million tonnes per year
Visit Porthos -
As of autumn 2022:
Denmark: New CO2 licensing round targeting virgin reservoirs and existing fields
Read Ocean 24 article
UK: New CO2 licensing round targeting virgin reservoirs and existing fields
Visit North Sea Transition Authority