Water is used for a variety of purposes at our oil sands operations, including drilling, dust suppression, utility boilers, cooling applications, camps and offices. The majority of the water is used in the bitumen extraction process.
In situ methods typically involve the injection of steam into the oil sands reservoir to heat the bitumen and reduce its viscosity, allowing recovery of the bitumen.
Cyclic steam stimulation (CSS) injects steam into a reservoir to recover oil from the same well over multiple cycles. Warmed lower-viscosity oil is pumped from the reservoir along with the condensed steam and sent to the processing facility. The cycle is then repeated.
Steam-assisted gravity drainage (SAGD) uses horizontal well pairs (one above the other) within the oil sands reservoir. The upper well is used to inject steam into the reservoir, where it rises through the oil sands deposits creating a steam chamber that displaces and heats the bitumen. The bitumen then flows down by gravity and is recovered by pumping the lower well.
For both CSS and SAGD, the water produced along with the bitumen is separated and then either recycled or disposed of. The recycle rate depends on the supply and demand for steam in the operation, the quality of the produced water, and the treatment technology.
Recycle rates are typically greater than 90 percent.
For oil sands mining, the water in the extraction process is used to slurry, transport, and separate the oil from the oil sands ore. Water sources include the recycled tailings water, river water, groundwater, and surface water runoff. By far, the largest overall water source is the recycled tailings water. After startup, it represents approximately 80 percent of the water used.