Carbon dioxide gas expands to many time's it's liquid volume underground. This, along with the small molecule size forces oil and gas out of tight fissures and pores in a reservoir. CO2 is easy to transport in pipelines from areas where it is abundant and injection of CO2 gas for enhanced oil recovery could also be a solution for getting rid of this greenhouse gas.
Projects are underway to scrub CO2 from coal burning power plants and sell it to the oil and gas industry. However, most CO2 that is sold to the oil industry comes from wells in places like Texas, Wyoming, Mississippi and New Mexico. Major CO2 producers such as Kinder Morgan LLC and Denbury Resources Inc., both of Houston, indicate new investments for expansion and new construction of CO2 drilling and transportation infrastructure this year and next.
Steam and Fireflooding For Enhanced Oil Recovery
Steam and fireflooding techniques usually refer to injecting superheated water into a injection well located near the producing well as seen in the illustration above. The hot steam loosens molecules of oil that are bound to grains of sandstone, limestone and in tiny fissures. Surfactants, which are similar to soap and break down molecular bonds between objects, can be used in addition to steam injection of enhanced oil recovery.
Using Microbes For Enhanced Oil Recovery
The least common but perhaps most promising enhanced oil recovery technique is that of using microbes. Natural or Genetically altered microbes that either eat oil and create surfactants or gas which helps force crude oil out of the reservoir are being developed.
There are few applications in the field since the technology is in the early stages and is expensive. It could be conceivably be used in conjunction with other EOR techniques such as CO2 stimulation in the future.
A couple of projects, one near Four Corners New Mexico and Beverly Hills, California have used microbes to metabolize crude underground and cause it to leach toward the wellbore. As new strains of microbes are developed we will undoubtedly see some exciting uses of them in the oil industry.
Other Promising Secondary Oil Recovery Methods
Researchers in the oil and gas industry are constantly searching for ways to get more oil out of old fields. New technologies being experimented with include ultrasonic stimulation, where a device is lowered into the wellbore and ultrasonic waves penetrate the oil bearing formation, causing more oil to flow into the well bore. Horizontal wells could be used to place strings of ultrasonic vibration devices across several hundred or even thousand feet of the oil reservoir.
The Future: Multiple Methods Of EOR Combined?
Multiple methods, using vibration, steam and surfactants or CO2 and microbes could all be use to extract every drop of oil possible from an old reservoir. With advances in technology we could see many old depleted fields become revisited by oil companies who have developed superior enhanced oil recovery methods.
For more about oil and gas recovery methods and a good explanation of oil production in general see Oil and Gas Production In Nontechnical Language, which is used by many company training programs.