Oil Sands Product Streams
Bitumen produced from the oil sands contains a significant fraction of complex long chain hydrocarbon molecules known as asphaltenes and a relatively high sulphur content. Asphaltene content can vary from 10 to 18%, depending on the reservoir geology and process used to extract the bitumen.
Due to the high fraction of heavy components and high sulphur content, bitumen cannot be sent directly to a conventional refinery. A lower quality bitumen product (containing more than 1% water and solids) with a higher fraction of asphaltenes must be upgraded into synthetic crude oil (SCO), before it can be sold to a conventional refinery.
Better quality bitumen with a very low water and solids content and about 10% asphaltenes can be diluted and pipelined directly to a high-conversion refinery which has the capacity to accept a heavier crude oil feedstock. Diluted bitumen sold to market must contain less than 0.5% water + solids in order to meet pipeline specifications.
The largest stream of commercial heavy oil produced from the oil sands is Western Canadian Select (WCS), which is a blend of bitumen, conventional oil, synthetic crude and condensate. Canadian Natural Resources is the largest contributor to WCS, with Cenovus Energy a close second.
BITUMEN UPGRADING EXPLAINED
Bitumen extracted from the Athabasca basin contains about 17% heavy asphaltenes, which is far too heavy to be processed in a conventional refinery. Most Athabasca bitumen is therefore upgraded, where a majority of the heavy fractions are removed primarily through the coking process. Upgrading converts the heavy bitumen into SCO, which can then be sold to any conventional refinery.
About 40% of the bitumen produced in Alberta is sent to an upgrader for removal of these heavy fractions and conversion into SCO. This includes most mined bitumen, including production from Syncrude, Suncor, CNRL Horizon and Albian Sands, and a handful of in-situ facilities such as Firebag and MacKay River operations. With the exception of Shell's Albian Sands operations, these upgraders are normally located relatively close to where the bitumen is extracted.
The remaining 60% of the bitumen produced from the oil sands has a lower asphaltene content. This includes in-situ bitumen from the Cold Lake and Peace River basins and partially de-asphalted bitumen from Kearl Lake and the upcoming Fort Hills mining operations. These facilities produce a marketable diluted bitumen blend sold directly to high-conversion refineries without upgrading.
DILBIT EXPLAINED: MARKETABLE DILUTED BITUMEN
About 60% of Alberta's bitumen is diluted and sold directly to high-conversion refineries. These refineries can accept heavy oil streams with up to 10% asphaltenes, as long as the solids and water content is kept low. Over the past decade, most North American refineries have been modified to accept this heavier feedstock, which has seen increased production out from Western Canada, Mexico and Venezuela.
Most of Alberta's marketable diluted bitumen (often referred to as Dilbit) is produced at thermal in-situ facilities located near the Christina Lake and Cold Lake areas, which have a lower asphaltene content (around 13%) versus Athabasca bitumen (roughly 17% bitumen). This bitumen must meet strict pipeline specifications for water and solids content (less than 0.5%) and must contain enough diluent to meet minimum viscosity specifications. This minimizes risks of pipeline corrosion/erosion and ensures adequate flow properties, even at lower temperatures. Examples of in-situ diluted bitumen include the Christina Dilbit Blend, produced near Christina Lake and the Cold Lake Blend, produced in the Cold Lake area.
Some mining facilities, such as Kearl Lake, produce a partially deasphalted bitumen directly at the mine site, where 50% of the asphaltenes are removed from the bitumen, reducing its asphaltene content to less than 10%. This bitumen is diluted with condensate and sold directly to refineries without needing to be upgraded. Diluted bitumen produced at Kearl has a slightly lower asphaltene content (about 8%) than other Dilbit blends (normally closer to 10%) and is sold directly to market as the Kearl Lake Blend.
Partial deasphalting at the mine-site is a low cost alternative to full upgrading, and is the technology of choice at the upcoming Fort Hills Mine, currently under construction north of Fort McMurray. Partial removal of asphaltenes is achieved through Paraffinic Froth Treatment (PFT) directly at the mine site. A PFT facility is significantly cheaper to build than a full upgrader, resulting in significant cost savings. Bitumen produced from a PFT facility also has a lower carbon footprint since it does not go through an upgrading step.