Thermal Recovery Methods

The most common in-situ processes are thermal recovery methods. Basically, steam is injected through wells to heat the bitumen and make it mobile enough to flow to production wells. These thermal recovery methods include:

• Cycling Steam Stimulation (CSS)
• Steam Flooding (SF)
• Steam Assisted Gravity Drainage (SAGD)

CSS and SF generally target thicker and deeper bitumen deposits, situated more than 400 metres below surface. SAGD typically targets intermediate-depth deposits, located less than 400 metres below surface, with relatively high sand permeability.

Cycling Steam Stimulation (CCS)

In CSS, steam is injected at high pressure and temperature (as high as 350°C) into the oil sand formation for several weeks. Steam helps recover the resource in several ways. The heat dramatically reduces the viscosity of the oil sands and the water vapour helps to break out the bitumen from the sand that contains it. The high pressure induces fractures to be formed in the formation, through which steam can penetrate the oil sands. After a portion of the reservoir has been invaded and saturated, the steam is turned off and the reservoir is allowed to soak for several weeks. Then, the injection wells are turned into production wells. The mixture of condensed water and mobilized bitumen either flows on its own uphole to surface, or is pumped to the surface using downhole pumps activated by pumpjacks at surface. When the rate of production starts to decline, the injection-soak-production cycle is repeated. It can take between 120 days and two years to complete a single cycle. At surface, the cooling bitumen is typically mixed with diluents to reduce its viscosity and allow its transportation by pipeline.

Canada's oldest and largest in-situ CSS bitumen recovery project is Imperial Oil's Cold Lake in north-eastern Alberta. Imperial also became the first upstream oil and gas site in Canada ever to win Wildlife at Work certification from the Wildlife Habitat Council (WHC).

In 2010 four CCS projects were in production, operated by Imperial Oil, Canadian Natural Resources, Shell Canada and Southern Pacific Resource Corp. Bitumen production averaged more than 37 000 cubic metres per day in 2010 from four projects.

Steam Flooding (SF)

SF is also a steam-based process. It involves continuous injection of steam into vertical injector wells. The steam mobilizes the heated bitumen and drives it towards production wells. However, recovery efficiencies are generally poor due to gravity override of the steam over the bitumen, hence a significant amounts of the oil is bypassed. With bitumen recovery typically less than 20 per cent even in the best bitumen deposits, SF is not a common bitumen recovery process.

Steam Assisted Gravity Drainage (SAGD)

SAGD typically relies on two horizontal wells drilled near the base of the reservoir formation with a vertical separation of several metres. Steam is injected into the reservoir through the upper well. As the steam rises and condenses, it heats up the bitumen, reducing its viscosity. A "heat chamber" is created, which allows the hot bitumen and condensed steam (water) to drain by gravity into the lower producing well. The mobile bitumen then flows or is pumped up to surface.

With the technological advances and economics, the SAGD projects have grown from three in 2007 to fourteen SAGD projects producing a little over 50 000 cubic meters a day in 2010:

• Nexen and OPTI Canada - Long Lake project - is the first project to combine SAGD with onsite upgrading, and is the first commercial application of gasification in Canada. It is also the first in-situ integrated oil sands project in that bitumen will be upgraded in a field processing facility.
• Suncor Energy - Firebag thermal project - uses water from its mining tailings ponds as supply for steam generation.
• Japan Canada Oil Sands (JACOS) - Hangingstone project - is one of the longest running SAGD projects in the Athabasca area.
• Cenovus Energy - Foster Creek project - achieved production exceeding 20 000 cubic metres per day, making it the largest thermal oil sands producer using SAGD.
• Devon Energy - Jackfish project - was the first SAGD installation to rely completely on brackish or non-portable water for steam generation.

New Technologies

New technologies continue to improve project economics and reduce environmental impacts from bitumen recovery operations. Examples of these advanced technologies include:

• Solvent-assisted processes - Imperial Oil has recently applied a solvent-assisted CSS process called LASER, which reduces bitumen viscosity by adding solvent to the reservoir formation.
• ES-SAGD "Expanding Solvent-SAGD" - developed by the Alberta Research Council. This is a steam-based hybrid process involving the addition of a solvent or mixture of solvents to the steam. Advantages include further reduction of bitumen viscosity and reduced steam utilization.
• N-Solv Corporation - employs in-situ solvent extraction of the bitumen from oil sands. The process utilizes heated solvents, without steam injection, in a similar well configuration as SAGD. Without steam, heating requirements and fuel costs are believed to be much lower than SAGD.

In-situ combustion is also a potential candidate for improving project economics and significantly reducing environmental impacts. The most promising is Toe-to-Heal-Air-Injection (THAI). This technique consists of two wells: a horizontal producer situated at the bottom of the producing formation, and a vertical air injector at the toe of the producer. Initially, the formation near the vertical injector is super-heated to the spontaneous ignition temperature. Then air injection is started using the vertical well, resulting in in-situ combustion. The combustion reduces the viscosity of the surrounding bitumen and allows it to drain into the producer. The combustion chamber progresses along the horizontal producer, starting from the toe towards the heel of the producer. The produced CO₂ remains in the reservoir.

• Petrobank - Whitesands project - has received partial approval for a 1 600 cubic metres per day of bitumen production expansion and plans for an eventual expansion to 16 000 cubic metres per day using its toe to heel air injection process.

Thermal Recovery Methods - Resource Center