Dilbit

Dilbit is diluted bitumen. Per the Alberta Oil Sands Bitumen Valuation Methodology, "Dilbit Blends" means "Blends made from heavy crudes and/or bitumens and a diluent usually condensate, for the purpose of meeting pipeline viscosity and density specifications, where the density of the diluent included in the blend is less than 800 kg/m3."^[1] If the diluent density is greater than or equal to 800 kg/m3, the diluent is typically synthetic crude and accordingly the blend is called synbit.

Why dilute bitumen?

Bitumen and heavy oils are often produced from remote deposits such as the Athabasca oil sands in Alberta, Canada and the Orinoco tar sands in Venezuela. Before 1980, most produced bitumen was transported by truck, but trucking is seasonally restricted and relatively inefficient and expensive compared to pipeline transport. However, bitumen in its undiluted state is too viscous and dense to be transported by pipeline. To create a fluid capable of transportation by pipeline, bitumen must be mixed with a fluid that has much lower viscosity and will keep bitumen from precipitating out of the mixture. By 1985 and demonstrating the effectiveness of dilbit, Alberta Energy Company was operating dual pipelines to transport diluent from Edmonton to Cold Lake and dilbit from Cold Lake to Edmonton.^[2]

How is bitumen diluted?

The most common diluent used to dilute bitumen is natural gas condensate (NGC), especially the naptha component. Due to insufficient quantity of natural gas condensate, bitumen shippers also use refined naptha and synthetic crude oil (SCO) as diluent. Although SCO requires a higher volume percentage to achieve the same viscosity, at least one study found that SCO provides better blend stability than NGC.^[3] Shippers dilute bitumen before shipment in order to meet viscosity and density requirements found in common carrier pipeline tariff rules. By selecting different diluent types and blend ratios, bitumen shippers attempt to lower component costs, increase blend value, and maintain pipeline transportability. The blend ratio may consist of 25 to 55% diluent by volume, depending on characteristics of the bitumen and diluent, pipeline specifications, operating conditions, and refinery requirements.^[2]

What happens to the dilbit?

Diluent can be removed from dilbit by distillation and reused as diluent. Alternatively, the entire dilbit can be refined. As dilbit contains hydrocarbons at extreme ends of the viscosity range, dilbit can be more difficult to process than typical crude oil. As such, dilbit is normally only a small portion of a refinery's total feedstock.

Alternatives to diluent

• Heated pipelines
• Constructing upgraders closer to production

See also

• Canadian Centre for Energy Information
• Dilbert
• Drill bit
• History of the petroleum industry in Canada (oil sands and heavy oil)
• Syncrude
• Suncor

References

1. ^ (pdf) Alberta Oil Sands Bitumen Valuation Methodology, 2008-9995, Calgary, Alberta: Canadian Association of Petroleum Producers, Dec 2008, http://www.capp.ca/getdoc.aspx?DocId=144465&DT=NTV 
2. ^ ^{a b} Walker, Ian C. (1998) (pdf), Marketing Challenges for Canadian Bitumen, Tulsa, OK: International Centre for Heavy Hydrocarbons, p. 2, http://www.oildrop.org/Info/Centre/Lib/7thConf/19980101.pdf 
3. ^ Rahimi, Parviz; Alem, Teclemariam (10 Feb 2010). "Crude Oil Compatibility and Diluent Evaluation for Pipelining" (pdf). Joint CCQTA/COQA meeting (New Orleans). Devon, Alberta: National Centre for Upgrading Technology. http://geoscan.ess.nrcan.gc.ca/text/geoscan/fulltext/NCUT2009_Paper28.pdf. Retrieved 18 Jun 2011. 

External Links

• Southern Lights Diluent Pipeline