Viewpoint

M. PITTENGER, GHD

Atmospheric carbon dioxide (CO₂) remains high. Climate change is affecting the earth’s weather and climate systems, and there is rising urgency to find solutions to reduce carbon emissions and the greenhouse effect. Carbon capture, utilization and storage (CCUS) is emerging as a sustainable solution for three main reasons:

1. Fossil fuels are essential to life as we know it, now and for the foreseeable future.
2. Industrial processes that produce the goods we need also produce substantial amounts of carbon (FIG. 1).
3. Hydrogen (H₂) is gaining popularity for use as a fuel source because it emits no CO₂ when burned.

Why CCUS? As H₂ gains popularity as an alternative fuel, it can still be a carbon-intensive production process diluting overall carbon reduction benefits. Producing H₂ from coal or natural gas—known as brown and gray H₂, respectively—is a carbon-intensive process. Green H₂, produced from water using renewable energy, is carbon-free but presently very expensive. One interim alternative is blue H₂, made from natural gas, where the byproduct CO₂ is captured before it enters the atmosphere.

CCUS reduces emissions from oil and gas and industrial processes and is the key to allowing blue H₂ to be “blue.” It is the only method to capture and permanently store the carbon emissions produced when natural gas is converted to H₂. To permanently store this captured carbon, wells are drilled down into porous rock formations and CO2 is injected into these formations where it remains trapped by layers of rock deep underground, essentially forever. 

Why not just utilize the CO₂ to produce carbonate minerals, biofuels or other products? While the “U” in CCUS does stand for utilization, the scale of CO₂ emitted today that must be captured and kept out of the atmosphere vastly outweighs the amount that can be utilized with today’s technologies and uses, primarily to manufacture fertilizer. To put it in perspective, the International Energy Agency (IEA) estimates demand for CO₂ to climb to 272 MM metric tpy (tonnes per year) by 2025, while global emissions were estimated to be 36.2 B metric t of CO₂ in 2020.¹ Permanent storage of CO₂ is a necessary and practical technology that has been proven in concept and small-scale demonstration projects. Now, it is imperative for projects to move from the demonstration scale to the industrial scale. 

Much of the necessary technology and knowledge to permanently store captured CO₂ is already available through the oil and gas sector’s knowledge and expertise over the past century. This includes understanding sedimentary rock geology, finding porous rock deep beneath the surface and then accessing it through drilling. The oil industry is also familiar with injecting CO₂ into rock formations to extract more hydrocarbons. Two areas of knowledge discussed here are particularly necessary for enabling CCUS to become the world-changing solution it can be. 

Finding and evaluating CCUS opportunities. The first area of expertise needed is geological expertise to search for and evaluate geological formations suitable for CCUS and to define injection and monitoring plans. The oil and gas sector is quite familiar with this kind of search. It has evolved sophisticated tools, including seismic exploration, to build a picture of the underground environment. Petroleum geoscientists use these technologies to find porous rock formations covered by impenetrable layers of rock, which in some cases, trap hydrocarbons. 

CCUS uses similar technologies to find porous rock bodies situated in such a way that the injected CO₂ will remain in place rather than migrating to the surface. It is oil patch geology, in reverse. 

One good thing about CCUS is that rock formations do not need to contain hydrocarbons for CO₂ storage. Hence, CCUS has the potential to work in sedimentary geology that might not be hydrocarbon sources. This means that if there is a central source of CO₂ (e.g., an industrial complex or a cement-manufacturing facility), a CCUS-friendly rock formation might be available within a reasonable distance. 

Much of the knowledge and technology needed for CCUS is readily available, from geological research performed by governments to existing oil and gas exploration technologies that can be readily repurposed to find CCUS sites. 

CCUS sites require more than suitable geology. One requirement is proximity to sources of CO₂, possibly in a hub layout where pipelines carry CO₂ from various producers to a central site for injection underground. CO₂ is best pipelined in a supercritical state, at higher temperatures and pressures, where it is dense like a liquid but flows more like a gas. Because of this, it is uneconomical to transport for long distances. Other feasibility factors include the availability of electricity from renewable sources to power the pumps and other equipment to reduce the carbon footprint further.

Proving it with measurement, monitoring and verification. Companies undertaking CCUS projects must ensure that their project can sequester the expected amounts of CO₂ at the projected rate and cost. They must also show stakeholders—including financial sources, shareholders, governments and communities—that the project will safely store the CO₂ underground over the long term. Without these assurances, project credibility can be lost. This has led to the rise of measurement, monitoring and verification (MMV) as a discipline. Like site selection, MMV requires a wide range of skill sets and credible work by an independent, trusted third party with the necessary skilled professionals on staff.

To tie the pieces together, a true multidisciplinary team is required: this is not just about having all the specific disciplines working on their piece of the project individually. It requires integration between the disciplines each step of the way, as decisions in one area can drastically alter the outcomes in another area. Professional firms like the author’s can bring together a wide range of skillsets, including sedimentary geology, well engineering, pipeline design, facilities design, and others. Significant help in site selection and MMV can also be provided to guide CCUS projects to successful completion. 

The time for CCUS is now. The future is bright for CCUS. There is an increased sense of urgency, more funding is available, and companies are under increasing pressure to get results around environment, social and governance (ESG) benchmarks. The time for CCUS technology is now, and the need has never been greater.H₂T

LITERATURE CITED

¹ International Energy Agency (IEA), “Putting CO₂ to use—Global Energy Review 2021: CO₂ emissions,” 2021.

MICHELLE PITTENGER is the Lead Geologist for CCUS at GHD. She has 30 yr of experience finding and developing hydrocarbon and CO₂ sequestration resources. She has worked in numerous basins across the U.S., North Africa, the Middle East and Canada. Pittenger spent 29 yr at ConocoPhillips in various positions, including deepwater and unconventional developments, subsurface technology, and carbon capture and storage (CCS). The author can be reached at michelle.pittenger@ghd.com.