Geologic sequestration represents a cornerstone in our fight against climate change, providing a reliable method for long-term underground carbon dioxide (CO₂) storage. This process involves the injection of CO₂ deep underground into rock formations, effectively preventing its release into the atmosphere and thereby protecting our climate, the planet, and future generations.
The method has a rich history, backed by decades of intensive study and practical application. Experts in geology, seismology, fluid characterization, well engineering, and reservoir modeling have contributed to making geologic sequestration a robust and scalable solution for CO₂ capture and storage.
How Geologic Sequestration Works
The process begins with CO₂ capture, achievable through various means. It could be point-source capture at industrial sites like power plants or manufacturing facilities, or through Direct Air Capture technology, which mechanically extracts atmospheric CO₂. The captured CO₂ is then purified and compressed into a supercritical state, exhibiting both gas and liquid properties.
Next, the CO₂ is injected deep underground, typically more than 5,000 feet down, via high-integrity wells into subterranean reservoirs. Four key mechanisms ensure secure sequestration:
- Structural Trapping: A nonporous, impermeable caprock acts as a massive lid, securely trapping the injected CO₂ below.
- Residual Trapping: CO₂ gets trapped within the tiny pores of the reservoir’s porous rock, similar to a sponge.
- Solubility Trapping: The CO₂ dissolves in the naturally occurring briny fluids in the reservoir, increasing the fluid’s density and enhancing storage capacity.
- Mineral Trapping: CO₂ chemically reacts with minerals in the rock, transforming into stable carbonate minerals and becoming part of the rock itself.
In the United States, such operations use Class VI wells, specifically designed and regulated by the EPA to protect drinking water sources and ensure safe CO₂ storage.
Safety and Regulation
Each sequestration operation undergoes rigorous Monitoring, Reporting, and Verification (MRV), regulated by the EPA. This includes stringent requirements for well construction and operation, comprehensive monitoring of well integrity, CO₂ injection and storage, groundwater quality, and extensive reporting and recordkeeping.
Storage Capacity and Future Outlook
Geologic CO₂ storage is crucial for decarbonizing the energy, industrial, and transportation sectors. The International Energy Agency predicts a significant increase in the demand for CO₂ storage, from 40 million metric tonnes per year today to over 5,000 million metric tonnes by mid-century. The estimated global storage capacity is a staggering 55,000 billion tonnes.
Site selection for geologic sequestration is meticulous, involving an assessment of technical, logistical, and commercial factors. However, potential sites, primarily onshore in saline formations or depleted oil and gas fields, are abundant.
Companies like 1PointFive are pioneering the development of sequestration hubs in the United States, focusing on areas with suitable geology, industrial activity, and existing CO₂ pipeline infrastructure.
Geologic sequestration, with its proven track record and evolving techniques, stands as a pivotal tool in our global effort to mitigate climate change impacts and transition towards a sustainable future.