The Alberta oil sands are allocated a total of 8% of total Athabasca River water flow. This applies to both existing and future oil sands facilities, primarily mining facilities. Currently, the oil sands use about 0.5% of the total river flow, representing only a small fraction of their allocated water supply.
On average, a typical oil sands mine requires about 3 barrels of fresh water to produce one barrel of oil from the oil sands. In contrast, in-situ facilities primarily use water for steam generation and have a much smaller need for fresh water (less than 0.3 barrels fresh water per barrel of oil produced).
WATER ALLOCATION IN ALBERTA
The Alberta government allocates water approximately as follows:
- 43% - Farming & Agriculture
- 29% - Commercial Facilities
- 11% - Municipal Water Requirements
- 8% - Oil Sands Facilities
- 2% - Conventional Oil & Gas
- 6% - Other
Note that this figures represent volumes allocation, and not actual volumes consumed. About 60% of the water used in the oil sands is sourced from the Athabasca River.
WATER CONSUMPTION IN THE OIL SANDS
Each oil sands operator is required to apply for a water licence, which outlines their water usage requirements over the life of their facility. The Alberta Energy Regulator allows each operator a maximum yearly water limit, which is required to be metered and reported on a regular basis.
Water licences also stipulate how many weeks per year where fresh water supply may be cut-off during periods of low flow. This is generally reserved for winter operation where the Athabasca River water level can run below normal.
Note that in-situ operators primarily source groundwater aquifers for their fresh water requirements.
WATER RECYCLE RATES
About 80-95% of process-affected water is recycled back into the process. This water is always contained on-site and never allowed to be released back to the river or the environment.
THE ATHABASCA RIVER: WATER QUALITY
The water quality of the entire Athabasca River network is closely monitored by Alberta Environment. The Athabasca River is the largest undammed river in Alberta. Since it flows naturally, the river experiences wide variations in flow, sediment and concentrations of organic (such as hydrocarbons) and inorganic substances (such as heavy metals). This makes interpretation of short term trends very difficult.
Alberta Environment has been monitoring water quality since the early 1950's. Water samples taken all along the Athabasca River network are periodically compared to historical data to determine if the water quality or composition is changing. It is estimated that up to 150,000 people now live adjacent to the Athabasca River. The past 50 years has brought significant growth of populations and industries along the river, including the expansion of the oil sands, which first began operation in 1967. Significant advancements in analytical techniques have also made possible detection of trace elements (down to the parts per billion range) which were previously undetectable by older technology.
Water samples are taken both upstream and downstream of the oil sands and the any municipal waste-water treatment facilities to determine what impact these facilities are having on Alberta's fresh water supply. This data is regularly published by Alberta Environment (a link can be found here).
THERMAL IN-SITU FACILITIES: WATER MANAGEMENT
In-situ oil sands facilities primarily use water for the generation of steam. The quantity required for the process is much lower than mining facilities - only 3 barrels of water are required to produce 1 barrel of oil. A typical in-situ facility recycles about 90% of the water used on site. The remaining 10% (roughly 0.3 barrels per barrel of oil) is made up of fresh water supplied by groundwater aquifers
Water quality is very critical when used for steam generation. Water treatment is therefore a very important component of any in-situ oil sands operation.
OIL SANDS MINING OPERATIONS: WATER MANAGEMENT
Oil sands mining facilities are fairly water intensive. They require copious amounts of water to slurry the oil sands so it can be pumped and gravity separated throughout the process plant. This requires an oil sands to water ratio of at least 1-to-1 (or 50% water) within the slurry stream. A typical oil sands mining facility requires 9 barrels of water per barrel of oil produced. About 80% of this process water supply is recycled from within the process plant. The balance (or fresh make-up water) comes from the Athabasca River. That works out to about 3 barrels of fresh water for every barrel of bitumen produced.
TAILINGS POND WATER QUALITY
Water reclaimed from the tailings pond (normally referred to as reclaimed water) is generally 99+% water with up to 1% fine solids and trace amounts of hydrocarbons. These hydrocarbons normally consist of any unrecovered bitumen and trace solvents or diluents used in the process. The solids are typically very fine clays that do not settle easily in the tailings pond.
Tailings ponds are lined with compacted sand and a layer of very fine clay. This clay has a very low rate of permeability and helps prevent tailings water from seeping into the groundwater. Also, seepage collection and monitoring wells are installed around the perimeter of the tailings dyke (or tailings dam). These wells serve to monitor the quality of the groundwater and any seepage that occurs underneath the dyke. All seepage water any contaminated perimeter water (from rain or melting snow) is pumped back into the process.
Also, tailings pond operators are required by law to keep several meters of freeboard (i.e., the difference between the top of the water level and the top of the dyke). This ensures more than enough holding capacity in the unlikely event of extended heavy rains. It is therefore impossible for a tailings pond to overflow back to the environment.
REDUCING WATER CONSUMPTION: ACTION PLAN
- STORE RIVER WATER ON-SITE: Oil sands mining operators have large on-site river water storage ponds. This enables them to not withdraw from the Athabasca River when river water levels are low.
- USE BRACKISH OR BASAL WATER WHERE POSSIBLE: Both in-situ and mining operators use treated brackish or basal water for steam generation. Brackish or basal water is too saline for use as drinking water or for agriculture. This treated water supply helps offset fresh river water or groundwater.
- TREAT & REUSE TAILINGS WATER: Recycled tailings pond water can build-up elevated concentrations of sulphates, carbonates, salts and electrolytes. At high enough concentrations, these ions can hinder the settling of fine solids. This is detrimental to the gravity separation of bitumen and deteriorate the quality of the bitumen product. Oil sands mining operators are constantly evaluating different methods of large scale water treatment so this water can be reused without compromising the process or the equipment.
- LOWER STEAM-TO-OIL RATIO: Thermal in-situ operators constantly strive to lower the steam-to-oil ratio (SOR) used for bitumen extraction. Using less steam not only lowers the fresh water requirement but also reduces greenhouse gas emissions since less natural gas is required to be burned. Lower steam-to-oil ratios is primarily achieved by improving oil recovery rates from the operating wells. The use of solvents or chemical additives to reduce bitumen viscosity (instead of steam) is also becoming increasingly popular. This is all helping to reduce water consumption rates for in-situ operators.