by ExploCrowd CEO Sidsel Lindsø

Moving swiftly is important, but moving with precision is crucial. When it comes to CO₂ storage, we need to do both. What is the best plan for success? An ongoing discussion within our team for years has revolved around the discrepancy between the usage of published CO₂ capacity estimates and their intention.

Let us explain more:

Current challenges

Many of the companies involved in the emerging CCS business and policymakers frequently build their business cases around ‘Play level’ estimates (at best), which represent the least developed phase in the CO₂ storage site maturation process. This phase is often associated with significant uncertainty.
The current timelines for de-risking potential CO₂ storage sites with the best appraisal strategy to narrow the estimated storage capacity ranges, often tend to be overly optimistic. Realistically, the process from advancing a site from the Lead or Prospect stage to operating status often spans between 5 to 8 years. However, in certain cases, there may be possibilities for accelerated advancement.

Proposed solutions

1. Enhanced awareness

Improved understanding within the CCS business regarding the uncertainties associated with geological CO₂ storage, the components an appraisal program usually consists of, associated costs, and establishing realistic timescales.

2. Common language

Facilitating a common communication framework to ensure comprehensive understanding among stakeholders engaged in geological CO₂ storage, regarding a project’s maturation process and confidence in the reliability of CO₂ storage capacity estimates.

3. Classification systems

For the latter, we are fortunate to have existing classification systems managing both uncertainty and maturity, consequently evaluating the feasibility of CO₂ storage projects. These long-standing systems have been used along with independent auditing used by investors and publicly listed companies.

An example of an appraisal program

As an example for what it will take to mature a potential storage site onshore Denmark, below you will find our recommendation. The Gassum Site is currently included in the planned December 2023 licence round, and it is also one of the two sites that the Norne project has included in its ambitions. The Norne project is currently included on the list of projects with special public interest that can apply for EU funding.

Note that the currently available seismic lines the Gassum Site structure is based on are marked in black, which is why the structure may change shape when new seismic data is available. The new 2D seismic lines that have been acquired recently are shown in orange. Also note that the new seismic lines follow the roads in the area, which is a limiting factor when acquiring seismic data onshore in populated areas.

The Gassum-1 well was drilled shortly after the end of second world war, in the hunt for the gas that was recently discovered onshore in Germany.

There were problems during drilling, why the Gamma Ray Log was acquired within the casing, thereby reducing the confidence of log interpretations significantly. Core data is available, but the storage capacity estimates are still associated with significant uncertainties and risk.

In order to reduce risk, our recommendation for an Appraisal program would be as follows:

2D seismic data (in progress).
More 2D seismic data?
Update structure map and capacity estimate ranges with new reduced uncertainty.
Appraisal well near crest No. 1 to test reservoir presence and quality (keeper well for future injection?
Drill Appraisal well No. 2 at flank of structure to test aquifer presence and quality.
Update geological model and simulation model to update economics.
Final Investment Decision for developing site, provided site is suitable for CO₂ injection.
Ensure delivery of CO2 for injection at the right time.
Drill new Injector well(s).
Build surface constructions needed for CO2 injection.
Target achieved: CO2 injection site operational.

To ensure safe drilling operations, a well often takes several years to plan, including tendering for and securing an offshore or onshore drilling rig, getting the required permits in place from specific authorities. An example of what is required in terms of application documents for the Northern Lights | Longship | Aurora project, located offshore, can be found here.

For wells that are planned for being in touch with CO₂, which is extremely corrosive, a special type of equipment is required. Many long leads items have one or two years waiting time. The first well on the Northern Lights project took three months to complete (and cost 1 billion NOK), and the second well took just one month to complete. Onshore wells can be drilled at a fraction of the cost, but environmental permits must be expected to take longer to get into place. It could easily be two to three years prior to securing the drilling permit.

When the data from the well and seismic data are acquired and available, the geological models must be updated with the latest information, and the simulation of how the CO₂ and pressure moves in the reservoir and aquifer updated accordingly. With this in place, it is possible to evaluate the economical aspects of a business case with a relatively good confidence, and it is possible to reach a Final Investment Decision for the remaining part of the project.

A common language for uncertainty and maturation

Classification systems have long played a role in auditing reserves within the oil and gas industry and managing resources on a general basis.

There’s subjectivity in selecting the preferred system, whether it’s the UN based systems, or the classification system adopted from the Petroleum Reserves Management System (PRMS) developed by the Society of Petroleum Engineers, World Petroleum Council and the Executive Committee, American Association of Petroleum Geologists (AAPG). This system, approved by the US Securities and Exchange Commission (SEC) aims to bolster trust in volumetric estimates of oil and gas presented to the markets.

My preference aligns with the CO₂ Storage Resources Management System (SRMS), which is based on the PRMS framework. I was trained with this system during my time with GaffeyCline, making it the most logical choice for me.

Below is a simplified version of the SRMS system. Projects begin at the base level, where the National CO2 storage atlases are found, at the Play maturity levels. Our recent study covering onshore and nearshore CO₂ storage sites in Denmark are ‘Lead maturity level’, because the data available are sparse. Modern data is required to take the Leads to the Prospect maturity level in the SRMS classification.

The CO₂ Storage Resource Management System developed by SPE and others classify potential projects in terms of maturity. It also include ranges of potential storage capacity, e.g. 10 Mt - 100 Mt - 250 Mt as 1U - 2U - 3U ranges for the most immature projects, as mentioned in the example described below. These are the classification systems that are often used for independent audits of CO₂ storage capacity by subsurface experts.

With appraisal of the potential CO₂ storage site with a well and confirmation of reservoir presence, a site can move up to the next level within the classification scheme and enter the Sub-commercial contingent resources category.

As a project is matured over time, with more subsurface insights, it can be ready for the Final Investment Decision – if the reservoir, seal and aquifer turns out to be as good as expected. At this stage, most assumptions have been confirmed by real data. Some uncertainties might still be uncovered, but injection at the site will provide more insights about the reservoir and aquifer, and adjustments to the injection plan can be made accordingly with time.

Hence, it is a lengthy process to mature a potential CO₂ storage site from an idea in a screening project to achieve actual operational status.

Addressing uncertainties

From our perspective as geologists and subsurface experts, employing ranges instead of singular numbers is imperative. While it might seem simpler to communicate a single figure, it often implies an estimate with high confidence, as opposed to saying:

‘The storage potential of this site is likely around 100 million tons of CO₂ but could be as low as 10 million tons. Under optimal conditions, the total storage capacity might reach up to 250 million tons CO₂.’

This example highlights the uncertainty in CO₂ storage capacity estimates, and that is exactly the point. Working with limited data and incomplete subsurface information, it’s essential for all stakeholders to understand the significant uncertainties inherent in predicting what lies beneath our feet.

However, as geologists, navigating uncertainty is an integral part of our work; it’s part of our expertise.

Curious to learn more? Here is what you need to read:

The reflections upon the EU CCS Forum in Aalborg on the 27th and 28th of November 2023 that this blog post is a reponse to: https://www.linkedin.com/posts/sidsel-linds%C3%B8-27a44a2_euccusforum-ccs-ccus-activity-7135688522836918272-Kszg?utm_source=share&utm_medium=member_desktop
The brief version of the SPE SRMS: https://www.spe.org/industry/docs/SRMS.pdf
The longer version of SRMS with description of maturity levels and examples: https://www.spe.org/media/filer_public/3c/21/3c21b6b8-b6fd-4fd5-aa2f-d8551136b085/211021_srms_guidelines.pdf
United Nations Resource Management System (UNRMS): https://unece.org/sustainable-energy/unfc-and-sustainable-resource-management/unrms
2018 Comparison between UNECE classification, SRMS and NPD classification: https://www.npd.no/globalassets/1-npd/fakta/co-to/characterization-and-classification-of-co2-storage-sites-on-the-norwegian-continental-shelf.pdf

Get in touch and we can dive into the details and assist you in the evaluation of the CO₂ storage sites that you are interested in. We are right here, ready to get you to move fast.

We need a common language for CO₂ storage capacity