CO₂

Removal of carbon dioxide (CO₂) from synthesis gas (syngas) often takes place before further processing. Carbon dioxide can be removed in a variety of ways and for varying reasons. Limits on emissions are looking increasingly likely, so finding a use for produced CO₂ is important. Fortunately, CO₂ is valuable for use in enhanced oil recovery (EOR).

Enhanced Oil Recovery
EOR is the use of CO₂ to recover oil from typically mature fields that are at or near the end of the effective period of traditional oil extraction techniques. EOR is used when primary and secondary methods of oil extraction have ceased being productive. Primary and secondary methods typically leave two-thirds of original oil in-place (OOIP). In all, 600 billion barrels of oil have been discovered in the United States and approximately 400 billion barrels are unrecoverable by conventional methods. Half of that unrecoverable oil (200 billion barrels) lies less than 5,000 feet below the surface, and is therefore a primary target for EOR.

The Great Plains Synfuels Plant/Weyburn Project
In 2000, the Great Plains Synfuels Plant (GPSP) began selling CO₂ emissions, becoming one of the first commercial facilities to sequester CO₂ from a coal process (see Designs for CO₂ Capture for more information). The program began in 1997, when EnCana (formerly PanCanadian Resources) sought a solution to declining production in their Weyburn Oil Fields. Dakota Gasification Company, owners of the GPSP, and EnCana made an agreement to sell CO₂ for use in EOR. Through 2006, the GPSP compressed approximately 105 million standard cubic feet per day of CO₂ and delivered it through a 205 mile pipeline from Beulah, North Dakota, to the Weyburn Oil Fields, located in Saskatchewan, Canada. The CO₂, about 95.5% pure and very dry, is then injected into the mature fields where it has doubled the oil recovery rate of the field. In 2006, a third compressor was installed and an additional agreement was reached with Apache Canada Ltd. to supply CO₂ for EOR to their nearby oilfields. The three compressors increased CO₂ delivery to 160 million standard cubic feet (MMSCF; or 8,000 tonnes) per day, or almost 50% of the plants CO₂ production. To date, approximately 6 million tonnes of CO₂ have been sequestered and over the current expected lifetime of the program, an anticipated 20 million tons of CO₂ will be stored.

This agreement benefits both parties: byproduct revenue and sequestered carbon emissions for the gasification plant and enhanced oil production for the oil field. The use of CO₂ from the GPSP for EOR is predicted to allow an extra 130 million barrels of oil to be produced and enable the oilfields to be productive an additional 25 years. The Dakota Gasification Company expects to see increased net revenue beyond the $100 million initial investment in the pipeline and compressors, with some sources placing the pre-Apache Canada Ltd. agreement at between $15 and $18 million per year.¹

The GPSP benefits from being in relatively close proximity (205-miles) to an area of mature oil fields (the Williston Basin, which extends from northern North Dakota and Montana into Saskatchewan and Manitoba). Relative proximity to a CO₂ buyer is important, as geographical limitations, expensive piping of CO₂, and safety are all key factors. Experts have speculated that the Permian Basin in Texas offers potentially good opportunities for CO₂ use in EOR. In some areas, naturally occurring CO₂ is being used for EOR, and its availability could affect markets for a carbon-separating gasification facility.

For more on the Great Plains Synfuels Plant, please see:
	Practical Experience Gained During the First Twenty Years of Operation of the Great Plains Gasification Plant and Implications for Future Projects [PDF-3.1MB]

1. The Sinor Synthetic Fuels Report. J.E. Sinor Consultants Inc. July 2001.

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