Four Decades of Success Using CO2 EOR
As much as two thirds of the nation’s known oil resource remains “stranded” and may not be recoverable without the development and use of advanced EOR technologies.
EOR is a way to squeeze out additional, hard-to-recover barrels of oil remaining in older fields following conventional production operations.
It can also be used to permanently store carbon dioxide (CO2) underground.
Thanks in part to innovations supported by the Office of Fossil Energy’s National Energy Technology Laboratory (NETL) over the past 30 years, the United States is a world leader in the number of EOR projects (200) and volume of oil production (over 350,000 barrels daily) from this method. This represents nearly 14 percent of total U.S. production. Although there are other methods (such as steam and chemical injection), CO2 injection is responsible for the largest single portion (40 percent) of U.S. EOR production.
CO2 EOR is a mature (40+ years) and proven technology for increasing oil production and safely transporting and storing carbon dioxide permanently in underground reservoirs.
While there are literally 100s of thousands of old oil wells and oil fields in the USA that could benefit from CO2 EOR, the vast majority of these EOR-worthy oil field are located far away from a CO2 pipeline that could cost-effectively transport CO2 on-site to their wellbores.
Primary, Secondary and Tertiary EOR
During primary recovery, the natural pressure of the reservoir or gravity drive oil into the wellbore, combined with artificial lift techniques (such as pumps) which bring the oil to the surface.
But only about 10 percent of a reservoir’s original oil in place is typically produced during primary recovery.
Secondary recovery techniques extend a field’s productive life generally by injecting water or gas to displace oil and drive it to a production wellbore, resulting in the recovery of an additional 20 percent of the original oil in place.
However, with much of the easy-to-produce oil already recovered from U.S. oil fields, producers have attempted several tertiary, or enhanced oil recovery (EOR), techniques that offer prospects for ultimately producing 30 to 60 percent, or more, of the reservoir’s original oil in place. Three major categories of EOR have been found to be commercially successful to varying degrees:
- Thermal recovery, which involves the introduction of heat such as the injection of steam to lower theviscosity, or thin, the heavy viscous oil, and improve its ability to flow through the reservoir.Thermal techniques account for over 40 percent of U.S. EOR production, primarily in California.
- Gas injection, which uses gases such as natural gas, nitrogen, or carbon dioxide (CO2) thatexpand in a reservoir to push additional oil to a production wellbore, or other gases that dissolve inthe oil to lower its viscosity and improves its flow rate. Gas injection accounts for nearly 60 percentof EOR production in the United States.
- Chemical injection, which can involve the use of long-chained molecules called polymers to increase theeffectiveness of waterfloods, or the use of detergent-like surfactants to help lower the surface tensionthat often prevents oil droplets from moving through a reservoir. Chemical techniques account for aboutone percent of U.S. EOR production.
Each of these techniques has been hampered by its relatively high cost and, in some cases, by theunpredictability of its effectiveness.
Fossil Bay’s EOR skids allow oil lease operators to skip secondary water-flooding (because injected water can “stuff” reservoir pore space and prevent injected gases from making contact with the hydrocarbons in the pore space) by implementing water-less gas injection CO2 EOR + Thermal EOR + Chemical Solvent EOR all-in-one high-temperature and high-pressure exhaust gas injection stream (with vapor-phased chemical solvents in gaseous form) reaching the farthest reservoir pore space with the highest contact efficiency.
EOR Information and pictures courtesy of U.S. Energy.gov website