Carbon Capture and Storage, or CCS, is an important technology for reducing the greenhouse gas emissions from coal-fueled power plants and other industrial sources. CCS is a three part process wherein, CO2, a greenhouse gas, is captured from a plant’s emissions stream, transported in a pipeline, and stored in the subsurface. While the technology holds significant promise, it is many years from being commercially available. As the U.S. Department of Energy (DOE) and its industrial partners undertake efforts to demonstrate the technology, most projects look to CO2 enhanced oil recovery (CO2-EOR) to store their captured CO2.
Basics of CO2-EOR:
Some oilfields that have gone through conventional oil production are amenable to processes that produce additional oil. One such process is the injection of CO2 into the depleted oilfield. Injected CO2 helps produce additional oil by raising the pressures of the formation which holds the oil and by reacting with the oil, making it easier to move. When the oil and CO2 are produced at the surface, the CO2 is separated from the oil and re-injected into the formation. Some CO2 remains in the subsurface permanently. CO2-EOR operations tend to operate like closed-loop system, with CO2 either remaining in the subsurface, or being re-injected instead of being released into the atmosphere. The EOR industry has several decades of experience conducting CO2-EOR operations with CO2 from naturally occurring sources.
Potential for CO2-EOR:
As part of the DOE’s effort to develop CCS technology, it published the fourth updated of their “United States Carbon Utilization and Storage Atlas” (Atlas). The Atlas attempts to quantify the amount of CO2 storage resource in various geologies across the U.S. and Western Canada. DOE estimates that nearly 250 billion tons of CO2 can be stored in depleted oil and gas formations. This estimate does not account for economic or regulatory barriers that will limit the number of fields amenable to CO2-EOR. It is worth noting that around two thirds of this potential is in the southwestern United States.
Regulatory Framework of CO2-EOR:
All injections in the US are regulated under the Safe Drinking Water Act. Pursuant to that law, EPA has promulgated regulations for CO2-EOR operations through their Underground Injection Control (UIC) program. Responsibility for implementing these regulations, commonly referred to as “Class II” regulations, has been delegated to state agencies in most instances. These regulations cover construction and operation conditions, as well as other aspects of CO2-EOR operations. Additional regulation of CO2-EOR operations is part of EPA’s broader effort to quantify CO2 emissions across the economy, the Mandatory Reporting Rule. For each sector of the economy, EPA has developed a different subpart. For CO2-EOR, EPA has promulgated the tiered approach of subparts RR and UU. For conventional CO2-EOR operations, the less rigorous subpart UU applies. Subpart RR requires more robust monitoring for those operators that are required to provide additional monitoring data because they seek to permanently store CO2.
Importance of EOR in Demonstrating CCS:
CO2-EOR is playing an important role in the demonstration of CCS technology at coal-fueled power plants. DOE is supporting five CCS demonstration projects at coal-fueled power plants. Of those five projects, four plan to integrate CO2-EOR as the storage component of the project, including the only project that is under construction. The reason is simple, project developers can be paid by EOR operators for the CO2 that they generate. This economic benefit is important to the technology development because it can begin to reduce the overall cost of implementing a CCS project. The revenue from CO2-EOR, however, is not enough to account for the approximately $1 billion cost of installing CCS on a single 600 MW coal-fueled power plant. In combination with grants and tax incentives, CO2-EOR plays an significant role in demonstrating this important technology.
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