It is not only since the Canadian heavy oil resources have been declared economical that in many other countries around the world this kind of hydrocarbons have been produced for a long time. Heavy oil has been defined to have a dynamic viscosity of more than 10 cP or less than 22.3 ° API, and a high specific gravity. In addition there is ultra-heavy oil (or bitumen) with a very high viscosity or less than 10° API respectively. Further to these unfavourable characteristics for pumping, a considerable content of paraffin and wax with deposit temperature close to the ambience, as well as some gas may be present.
For several decades positive displacement pumps have a proven and excellent track record in such services with the twin-screw working principle being at the forefront of them. Their high efficiency especially with viscous media, but moreover the insensibility against free or entrained gas make them well suitable for such a service.
While transport distances of about 50 km can easily be achieved with a single pumping station, longer pipelines require intermediate ones, depending on diameter, landscape profile as well as capacity required.