How are oil sands and heavy oil produced? (continued)

Vapour extraction (VAPEX)

VAPEX is a non-thermal technology in which vapourized solvents such as ethane or propane are injected into the formation to create a vapour-chamber through which the oil flows due to gravity drainage. Like steam assisted gravity drainage, the VAPEX process can be applied using paired horizontal wells or a combination of vertical and horizontal wells.

Firefloods

Fireflooding is an experimental recovery method in which air or oxygen is injected into the producing formation and, along with some of the bitumen, ignited to increase the temperature and enable the oil to flow more easily to a production well. Petrobank Energy and Resources Ltd. is using a variation on the fireflood method near Christina Lake, south of Fort McMurray in the Athabasca oil sands region; the system is called “toe-to-heel air injection” or THAITM.

Experimental methods

Other experimental methods have involved the use of solvents, electric currents, microwaves and ultrasound.

Mining

About 20 per cent of Alberta’s economically recoverable oil sands bitumen reserves are close enough to the surface to make mining feasible. Muskeg and overburden are first removed to expose the oil sands and are stockpiled for use in reclamation. Originally, oil sands were mined using draglines to excavate the face of the formation. Bucketwheels and long conveyor belts moved the raw bitumen to on-site processing facilities.

In the 1980s, trucks and power shovels began to replace the bucketwheels and draglines and today, all bitumen mining employs the truck and shovel method.

The power shovels dig out the oil sands and load it into which trucks transport the oil sands to crushers that break up lumps and remove rocks. In a process called hydrotransport, the oil sand is mixed with water at either 35°C or 50°C, depending upon the mine, and is piped to the processing plant. During hydrotransport, the bitumen begins to separate from the sand, water and minerals.

In some operations where conveyors are still in use, the oil sand is dumped into rotating tumblers where it is slurried by steam, hot water and caustic soda and then discharged onto vibrating screens to remove rocks and lumps of clay. This slurry is then blended with material from the hydrotransport process. Some operations have eliminated the use of caustic chemicals in the bitumen extraction process, thereby enhancing the water reuse capability and reducing tailings pond size, minimizing land disturbance.

Separation continues at the plant where the bitumen forms a thick froth at the top of the separation vessel and the sand settles out to the bottom. Material, including water, from the middle part of the vessel is further processed to remove more bitumen, the water is recycled and the sand is used in mine site reclamation. Froth is treated using inclined plate settlers or centrifuges to remove water and solids.

A new system was tested in 2006 and is expected to make ore transportation even more efficient. A mobile crusher, connected to a slurry pipeline, is located next to the power shovel so that the ore can be dumped in directly. Trucks would still be needed to carry overburden and to reach less accessible parts of the mines, but this system could considerably reduce the trucking requirement and related air emissions.

*Recovery rates vary according to the qualities of the reservoir and the recovery method used. Bitumen recovery rates at Cold Lake, where cyclic steam stimulation technology is used, have improved from initial estimates of about 17 percent to more than 25 percent today. At the Mackay River oil sands facility, steam-assisted gravity drainage results in recovery of more than 60 per cent of the original oil in place.