explainer: where can we safely and permanently store carbon dioxide?

Carbon capture and storage (CCS) is an important part of lowering the carbon intensity of our own operations and those of major industries. Captured carbon is stored permanently underground to keep it from reaching the atmosphere.

When we talk about underground storage, we look closely at the geology of the area to find an ideal place to keep the carbon dioxide (CO₂).

Keeping CO₂ out of the atmosphere and permanently stored underground can be a significant factor in achieving the ambitions of the Paris Agreement. According to the Intergovernmental Panel on Climate Change, large-scale CCS technologies are instrumental in achieving such goals.

We look for specific characteristics in a carbon storage site, such as whether it’s cost-effective to inject CO₂, our confidence in the geology to contain it, and our ability to monitor it. When we look for high-quality, permanent storage sites, here are a few factors that make the cut:

• A minimum depth of 800 meters: At this depth, the CO₂ compresses into a denser, “supercritical” fluid. We can store many times more CO₂ in the same amount of space because of the increased density.
• Reservoirs and pores: We look for thick reservoirs with lots of granular fragments and a high capacity for flow, such as sands from ancient, buried beaches. The CO₂ flows between the grains in what is known as pore space and becomes trapped there.
• Impermeable caprock: This naturally occurring barrier is a thick sequence of rocks with low or no flow capacity that covers the top of the reservoir. This “caprock” prevents the CO₂ from migrating up and out of the reservoir rock and leaves it permanently trapped deep underground.

Finding the best-quality sites for carbon storage takes a team of experts with extensive subsurface experience. Chevron has decades of experience in CCS.

“We’re really one of the few companies that have the subsurface expertise and technical capabilities to identify, screen, characterize and ultimately develop, operate and monitor a storage project,” said Mark Korte-Nahabedian, a geologist and Chevron’s lower carbon coordinator for our San Joaquin Valley, California, operations.

Drawing on this depth of experience, we plan and model how a storage site will perform and verify that the CO₂ will stay in place long after we’ve stopped injection. These robust plans help us advance a lower carbon future.