Fit-For-Purpose Associated Storage

Long-term CO2 storage can be achieved as part of an EOR operation (image not to scale, taken from Klapperich and others, 2013a).

Associated storage projects, which are working toward the objective of achieving low-carbon oil, focus on optimizing storage of carbon dioxide (CO₂) associated with enhanced oil recovery (EOR) operations. Storage of CO₂ in association with EOR offers a means to help offset capture costs and thereby accelerate the implementation of geologic storage. A new, potentially large opportunity for CO₂ storage is associated with residual oil zones (ROZs) and tight oil formations (TOFs).

CO₂-EOR is an active commercial activity, whereas unconventional oil reservoirs, including ROzs and TOFs, present a new opportunity for CO₂ injection for oil production and associated storage. These reservoirs may have as low as five percent oil-in-place primary production.

ROZs are immobile areas of oil located below the oil-water contact of a reservoir, commonly located at the base of oil reservoirs.

The ROZs are often mixed with water and require EOR techniques such as CO₂ flooding to produce the residual oil. Some studies have proposed that ROZs may also occur beyond the bounds of existing oil reservoirs, and are termed “fairways.”

TOFs are oil formations with very low permeability (less than 10 millidarcies) that resist the flow of fluids without assistance from advanced drilling and completion.

TOFs, such as Bakken, Eagle Ford, and other shales, also offer potential opportunities for associated storage in conjunction with EOR. Current research is underway to enhance understanding of "fairways," including the extent of the deposit and amount of hydrocarbon in the resource, and to characterize and determine storage capacity for CO₂ associated with EOR in TOFs.

Associated storage field laboratory projects focused on unconventional ROZs and TOFs will demonstrate their potential as an additional carbon storage reservoir associated with EOR and support deployment of the technology by industry. Field laboratories will also provide data to improve estimates for storage capacity of CO₂ in conjunction with EOR and will provide validation of modeling, simulation, and monitoring tools specific for associated storage in unconventional ROZs and TOFs.

More information about associated storage projects can be found on the Carbon Storage Project Portfolio Page under “Fit-for-Purpose Projects.”