Bitumen needs to be diluted so it can flow in pipelines to market; the resulting product is called dilbit. Natural gas condensate (the diluent), especially the naphtha portion, is commonly used to dilute bitumen. CRW, an Enbridge Condensate Stream, is a mix of condensate streams from a variety of sources that is a common diluent. Where there are inadequate condensate supplies shippers can use refined naphtha or synthetic crude oil (SCO – in this case the product is called synbit).
Once the dilbit is received at the upgrader/refinery the diluent can be removed and sent back for re-use. Some dilbit pipelines have a return flow pipeline devoted to shipping diluent back to the bitumen production source; for example the proposed Northern Gateway pipeline would have a 36 inch petroleum products line flowing west for export and a 20 inch condensate line flowing east. Similarly Enbridge ships condensate from Chicago through to Edmonton in the Southern Lights pipeline.
Concerns have been raised by environmental groups that dilbit is more corrosive than conventional or synthetic crude oil, thus increasing the risk of pipeline spills. A study by Alberta Innovates – Technology Futures indicated that the characteristics of dilbit are not unique and are comparable to conventional crude oils, though they did recommend further studies and separate public reporting on dilbit and conventional crude oil pipelines.