How Enhanced Oil Recovery Or EOR Works.

As the world continues to use more crude oil and world oil reservoirs are depleted, new ways of extracting oil and gas must be developed to get every drop possible from existing sources. In the old days, a vertical well could only extract part of the oil in a reservoir due to the heavy nature of hydrocarbon molecules and their ability to cling to whatever surrounds them, such as rock particles. This left as much as eighty percent or more of the oil still in the ground. Oil fields were abandoned, towns died off and workers moved elsewhere, all with as much as eighty percent of the oil still underground, yet untouchable.

Now with enhanced tertiary recovery methods another twenty percent or more can be extracted, or up to sixty percent of the oil is a reservoir, effectively doubling or tripling the amount of oil produced from the field. Examples of large enhanced oil recovery projects are in the Weyburn Oil Field in southern Saskatchewan, owned by Encana, where over 18 million tons of CO2 have been pumped underground to extract oil.

According to the Department of Energy (DOE) it is estimated that full use of CO₂ enhanced oil recovery in United States could generate an additional 240 billion barrels of oil. That's like finding a whole new major oilfield right inside the United States.

Horizontal drilling has increased the amount of oil that can be extracted but it is not considered enhanced or tertiary recovery. However, horizontal drilling, as described here How Oil and Gas Wells Are Drilled Horizontally, is often used in conjunction with EOR or enhanced oil recovery. Horizontal wells are used as both injection and collection wells.

What Methods of Enhanced Oil Recovery Are Commonly Used?

Co2 Well Illustration From University Of Kansas

CO2 Used For Enhanced Oil Recovery

Carbon dioxide gas is quickly becoming the preferred method of enhanced oil recovery in many fields. This is due to several factors. 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.

Helpful Links: Rigzone.com Rig Count Page Schlumberger Dictionary Baker Hughes

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