How are oil sands and heavy oil produced?

Conventional methods

Some heavy oil can be produced using conventional means, such as vertical wells, pumps and pressure maintenance; however, compared to other, more sophisticated production methods, this is very inefficient.

Horizontal wells improve efficiency by increasing the length of the wellbore that is exposed to the producing formation. Technologies such as progressive cavity pumps and drilling with coiled tubing further improves the economics of the well, but the limiting factors are still gravity and viscosity of the oil.

Bitumen has been recovered using cold methods where deposits are considered too thin to make steam injection economical.

Cold heavy oil production with sand (CHOPS)

Sand, usually in concentrations of one to eight per cent by volume, is allowed to enter the wellbore along with the oil, greatly improving well productivity. Wells that formerly produced only 20 barrels per day (three cubic metres per day) have been observed to produce more than 200 barrels per day (30 cubic metres per day) with free movement of sand into the wellbore.

This technology, pioneered in Canada, is most suited to heavy oil reservoirs where there is no active bottom water, where the sand grains are not cemented together, and where there are large amounts of gas dissolved in the oil.

Thermal in-situ recovery

About 80 per cent of Alberta’s oil sands are buried too deeply to be mined, and must be developed using in-situ methods.

For both oil sands and heavy oil, steam is often used to facilitate production by softening the bitumen, diluting and separating it from sand grains, and enlarging or creating channels and cracks through which the diluted oil can flow.

Existing in-situ technology uses natural gas-fired boilers to generate steam. The process requires a lot of water – up to three cubic metres for each cubic metre of bitumen produced - but more than 80 percent of the water is recycled.

Current in-situ production technologies recover between 25 and 60+ per cent of the bitumen in the reservoir – a somewhat higher recovery rate than most conventional light crude oil wells.

The two most successful methods are steam-assisted gravity drainage (SAGD) and cyclic steam stimulation.

• Steam-assisted gravity drainage (SAGD) involves drilling two horizontal wells one above the other. Steam is continuously injected through the upper wellbore, softening the bitumen, which then drains into the lower wellbore and is pumped to the surface.

  Pairs of parallel horizontal wells, one for steam injection and one for production, make it possible to recover bitumen continuously from an oil sands formation.

  The McKay River oil sands facility 60 kilometres northwest of Fort McMurray, Alberta, uses SAGD to extract bitumen from an oil-bearing formation more than 100 metres underground. Steam generators at Petro-Canada’s MacKay River site play a key role in producing bitumen using horizontal well pairs. Steam is injected into the first well, reducing the viscosity of the tar-like bitumen. The bitumen flows more freely to the second well where it is collected and piped to the site’s central processing facility. One hundred and twenty-five wells will be drilled over the field’s 25-year lifespan, each lasting an average six to eight years. Bitumen produced by the operation is diluted, then shipped by pipeline to eastern Canadian and U.S. markets.

• Cyclic steam stimulation: a three-stage process involving several weeks of steam injection, followed by several weeks of “soaking,” followed by a production phase where the oil is produced by the same wells in which the steam was injected. As production declines, the injection phase is restarted.

  Steam saturates the oil sands formation, softening and diluting the bitumen so it can flow to the well during the production phase. The high-pressure steam not only makes the oil more mobile, it creates cracks and channels through which the oil will flow to the wellbore.

  This process can involve vertical, deviated and horizontal wells.

  A variation of cyclic steam stimulation was developed by Shell Canada for the Peace River oil sands plant. The “soak radial” technique utilizes a vertical well with four horizontal arms that extend spoke-like into the reservoir. Steam is injected for two months, followed by six to 18 months of reverse action during which oil is pumped to the surface through the same horizontal arms.

  Bitumen produced from Shell Canada’s Peace River complex is blended with locally supplied condensates for pipeline injection. The bitumen is marketed to refiners with heavy oil refining capabilities and is preferred feedstock for producing asphalt.