Enhanced Oil Recovery (EOR)  

 

Over Three Decades of Experience in Deep CO2 Injection Technology.                              

Image courtesy of: Flickr

 

A Blueprint for Geologic Sequestration

For over three decades, the EOR industry has injected over 850 Mt of CO2 into petroleum reservoirs, paving the way for permanent deep geologic sequestation of anthropogenic CO2 from power plants and other industrial sources. Deep carbon dioxide injection is a mature technology initially developed in the 1970s to produce stranded oil from petroleum reservoirs depleted during primary and secondary (water flooding) production.

 

Since the 1970s over a billion tons of CO2 have been injected in the West Texas Permian Basin alone. In the U.S., CO2-EOR produces approximately 250,000 barrels of oil per day. A total of 1.3 billion barrels of oil has been produced by CO2-EOR since the mid-1980s.

 

 

 

EOR Can Store Billions of Tons of CO2

EOR can play an important role in deploying early CCS projects because it offers substantial potential storage capacity. DOE has estimated 33 billion metric tons, enough for several decades worth of today's coal plant CO2 in the U.S.

EOR builds pipelines and surface injection infrastructure that could later be used for CO2 storage once the oil is depleted. When petroleum reservoirs are depleted, they can be filled to capacity, and additional CO2 may be stored in other saline aquifers stacked in the same geologic section.  

 

EOR sites offer the advantage of:

 

  • Existing infrastructure such as surface facilities, pipelines, injection and monitoring wells,
  • Well-understood geology and geologic seals,
  • Proven capacity to hold volumes of CO2,
  • Additional "stacked" storage in saline reservoirs below the hydrocarbon production zone.

 

Moreover, revenues from the sale of anthropogenic CO2 to EOR operators will offset the costs of carbon capture and compression while provided much needed CO2 to exploit new resources with next-generation EOR such as residual oil zones. Sequestration in EOR fields will, at a minimum, require greenhouse gas monitoring, and a determination that wells in the field are fully plugged so that CO2 will remain permanently trapped.        

 

 

Current U.S. Injection Sites

Today, the U.S. petroleum industry is successfully injecting into deep rock formations  approximately 35 million metric tons of CO2 per year for EOR-- the equivalent of eight coal fired power plants --where it remains today.

 

  • The town of Seminole in West Texas sits over one of the country’s oldest and largest EOR facilities, where oil recovery operations are currently injecting one million tons per year, with no known harmful releases of CO2. 
  • In Saskatchewan Canada, approximately 13 million metric tonnes of CO2 from a coal gasification plant in North Dakota have been injected at the Weyburn-Midale field for EOR.
  •  Approximately 175 million metric tonnes of CO2 have been injected and sequestered over the past 37 years at the West Texas SACROC EOR field.
  • In the Texas Permian Basin alone, approximately 850 million metric tons have been injected to date. Whiting's EOR North Ward Fort Estes facility in the Permian Basin (image above) is slated to receieve CO2 from the Summit 400 MW IGCC-CCS-fertilizer plant to be constructed near Odessa Texas.

 

 

How CO2-EOR Works

Carbon dioxide is more effective than water in sweeping out and recovering stranded oil from reservoirs because unlike water, it mixes with oil. In CO2-EOR, carbon dioxide is compressed to a semi-liquid, semi-gaseous ""supercritical" state and then injected into the reservoir rock. The super-critical CO2 can then penetrate the tiny pores in the reservoir rock, typically sandstone or carbonate rock like limestone or dolomite.

 

During the injection process, a significant fraction of the injected CO2 volume remains trapped in the rock where it may be sequestered by several processes: trapped in solution, by capillary processes in the tiny pores of the rock or by lateral and horizontal impermeability barriers. Because CO2 is a valuable commodity, the CO2 produced with the oil is recaptured and separated from the oil at the surface, then reinjected for futher EOR. Over time, the original "purchased" volume of CO2 becomes progressively trapped and sequestered in the formation. 

Diagram of how EOR works

 

Because EOR is undertaken in a largely closed system, very little CO2 is released as fugitive emissions—a small amount may remain in the oil or gas produced and CO2 could be temporarily flared and lost during a shutdown.  That amount has not typically been reported publically but by some estimates may be on the order of a few percent.            

 

Other industries have long-term experience with underground storage of fluids. For instance, natural gas has been safely and routinely in deep geologic formations for 80 years, in some cases under major urban areas.

 

Surprisingly, the United States disposes of more fluids by deep well injection every year than the quantity of CO2 emitted by the nation’s power plants.          

 

 

Residual Oil zones (ROZs)

ROZs are a "next generation" EOR frontier that promise to unlock substantial new Lower-48 oil resources and pore space for the storage of CO2. A residual oil zone is typically in the lower portion of a reservoir, below the producing zone where water has naturally swept out the oil in place. The oil saturation is much lower in the ROZ--on the order of 30 percent--but using CO2 much of the remaining oil can be produced. ROZ production will require large volumes of new CO2 supply which can be supplied from anthropogenic sources. By one estimate, 19.5 billion tonnes of CO2 could be needed for next-generation EOR in the U.S.

How residual oil zones work



Fact

CATF is working to

  • Establish carbon capture and storage as a major global industry.
  • Create a new generation of technologies and institutions capable of removing carbon dioxide that has already been released to the atmosphere.
  • Work directly with industry on getting more federal and state money to support these projects. 
  • Communicate with national and international news outlets, seeking to be seen as an honest arbitrator in coal and climate factual disagreements