Engineering and geology are key to Carbon Capture, Utilization and Storage project success

CCUS is essential to offsetting many current uses of fossil fuels. It’s also key to “blue hydrogen,” which involves generating hydrogen fuel from natural gas by methane reformation and then sequestering the resulting carbon dioxide, so it does not enter the atmosphere.

Much of the focus of CCUS planning has been around getting carbon dioxide to the injection site and building the surface infrastructure. But the often-missed piece is about choosing underground formations suitable for injection and permanent trapping of carbon dioxide.

Why does it matter? Because some CCUS facilities around the world have failed to sequester the quantities of CO2 that were originally proposed. For example, Australia’s only commercial-scale CCUS project was cancelled at an LNG plant because the amount of carbon dioxide sequestered was well below targets. Likewise, in Wyoming, USA, a CCUS project begun 35 years ago to collect CO2 for enhanced oil recovery (EOR) has consistently failed to reach utilization targets. As a result, it has vented captured CO2 back into the atmosphere when it couldn’t be sold for EOR purposes.

With lessons learned at these and other facilities, it’s becoming clear that a significant factor in the success of CCUS is “pore space” – the spaces between the grains of rock in the underground formation. Therefore, it’s vital to choose a rock formation with the capacity to accept and retain the CO2 being pumped into it.

Pore space is one of the considerations made by GHD in its work with the Alberta Carbon Grid™ (ACG) in the western Canadian province of Alberta. This is a world-scale carbon transportation and sequestration system being designed to serve multiple customers, industries, and sectors. Once fully constructed, the ACG aims to transport and sequester more than 20 million tonnes of CO2 annually – almost 10 percent of Alberta’s industrial emissions. The ACG has an important role in supporting a lower-carbon economy in Alberta.  The ACG was recently invited to move forward into the next stage of the province’s carbon capture utilization and storage (CCUS) process.

GHD’s role at the ACG includes working to retire subsurface risks and uncertainties through an appraisal program. We developed the preliminary static geologic model and dynamic reservoir simulation for the entire Area of Interest, which is used to guide the development of the appraisal program.

Appraisal of the sequestration formation will be done in stages as the ACG is built out. A program for acquiring new seismic data in two, three and four dimensions and core drilling and laboratory analysis is in development.

This appraisal, carried out over several years, will allow the creation of a detailed dynamic reservoir simulation, which will help reduce risk and uncertainty.

Although projects such as the ACG are breaking new technological ground, CCUS is an old idea with a new purpose. For decades, the oil and gas industry has been injecting carbon dioxide underground to force more of the hydrocarbon resource into wells so it can be extracted. CCUS takes this well-developed technology and repurposes it to fight climate change.

The oil and gas industry has a solid understanding of finding and delineating suitable rock formations underground and drilling wells to reach those targets, which may be several kilometres underground. This will help identify rock formations that meet requirements for CCUS, including the aspect of pore space.

There are great opportunities for the oil and gas sector members to reposition the skills learned in finding and producing oil and gas towards CCUS – a technologically and economically viable industry with a bright future.

To succeed, CCUS enterprises depend on making three kinds of promises:

• The ability to build infrastructure, drill or recondition wells and sequester CO2 according to stated projections and budgets
• That they can inject CO2 underground over the decades-long life of the CCUS project, at the flow rates and total volume stated in their projections
• For the future, the CO2 will stay there essentially forever and not migrate back to the surface to re-emerge into the atmosphere

If they can’t make these promises credibly, with the numbers and models to back them up, they may have trouble getting regulatory, political, financial and public support. Moreover, the stories of less-than-successful CCUS projects have demonstrated that many technical issues need to be resolved.

Given the challenges of applying existing technology to new purposes, several success factors have emerged:

• Knowledge of pipeline operation, particularly the transport of CO2 at high “supercritical” pressures, where distinct liquid and gas phases do not exist
• Optimized design of surface facilities, including the application of “green” electrical power, which is important to managing the carbon footprint of the project
• Most important and often missed by current actors in this space – an understanding of reservoirs, including porosity and volume of the formation, including pore space
• Reservoirs must be deep enough that the injected CO2 remains in a supercritical state, but not so deep that the pore space is reduced due to consolidation and is inadequate to contain the volume of CO2 needed
• Sufficient development area (i.e. pore space) to mitigate risks & uncertainties

This requires support from a multi-disciplinary team with expertise in engineering to design surface facilities, reservoir simulation, identifying risks, uncertainties, and mitigations, choosing the best options and presenting ideas to regulators, financial sources, and government leaders.