Injection into Saline Formations     

                                                                               Image Courtesy of:  Harald Pettersen / Statoil

Deep brine or saline formations have great capacity for sequestration. These areas are composed of porous rock that contains brackish water with naturally high salt and contaminant levels. For a brine formation to be suitable for sequestration, it must have a layer of nonporous stone, called a caprock, which helps to contain the CO2 in the saline formation. 

 

Over time, injected CO2 becomes trapped inside the rock that comprises the saline formation. Initially the CO2 is stored in the pores through the capillary pressure. Eventually it dissolves into a liquid, and over longer periods of time, hardens into solid calcium carbonate.

 

Sites for geologic carbon sequestration can be located on land, off shore or under the ocean. 

 

Other formations, such as coal beds that cannot be mined and basalt structures, may also be able to sequester CO2. However, the geochemical and geophysical trapping mechanisms are different and less well understood.

 

 

 

Geologic sequestration sites around the world have demonstrated that CO2 can be safely injected into unpotable saline aquifers.

 

  • In the U.S., the Denbury Cranfield Mississippi, boasts nearly 3 million metric tons of CO2 injected into the saline brine leg of a producing structure since 2008. 

 

  • Norway’s Statoil has injected 1 million metric tons (mmt) per year of CO2 at their Sleipner natural gas field for a total of 17 mmt since 1996.

 

  • In Statoil’s Snohovit project, injections of 0.7 mmt/ yr are now underway.

 

  • In Algeria, BP and Statoil and others are injecting 1.2 mmt/yr for 30 years.

 

  • At a demo plant in the Midwest US, American Electric Power captured and sequestered CO2 at a pilot 20 MW emissions slipstream at its Mountaineer WV plant. The project is now closed.

 

  • In Decatur IL, 1 mmt/yr CO2 from an ADM ethanol plant is being injected as a test of the Mt Simon formation.

 

  • In Alabama, Alabama Power/Southern Company’s plant Barry is the site of a fully integrated CCS project. The project is in operation and has the capacity of injecting 150,000 tons of CO2 per year.

 

The Intergovernmental Panel on Climate Change has estimated there is sufficient global geologic capacity to sequester 10,000 billion tons of CO2.

 

Department of Energy estimates for CO2 sequestration capacity are shown below.

 

Formation Type

Billions Metric Tons of CO2 Sequestration

Saline Formations

919–3378        

Unmineable Coal Beds

156.1–183.5

Oil and Gas Formations

8.24

 

The U.S. power sector currently emits 1.9 billion metric tons of CO2 annually.

 

To move saline sequestration to the commercial stage, there will need to be several large-scale saline sequestration sites developed during the pioneer phase.

 

 

These projects should provide valuable experience dealing with critical issues with this technology such as:

 

  • Scale: The largest saline formation injection sites in the world average 1 million tons of CO2 injection per year. A large coal plant, in contrast, emits around 6 million tons of CO2 per year. Developing saline injection sites at this scale is important.

 

  • Site selection, characterization, and monitoring protocols: The tools needed for the development and operation of saline sequestration have been used in EOR and other sub-surface commercial activities, but they have not been fit-to-purpose for this specific use except in some early demonstration projects.

 

  • Experience: While industry experience provides a solid foundation of knowledge in this field, we still lack essential institutional and professional expertise in dealing with the long-term geophysics, geochemistry, and geomechanics of saline sequestration.

 

There are also non-technical issues that introduce additional uncertainties for initial development of saline sequestration projects, such property rights, pore space, and permitting. Read more about CATF’s  recommendations  to overcome these barriers in our  recommendations to the Obama Administration’s Interagency CCS Task Force:“The Carbon Capture and Storage Imperative:

 



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