Heavy oil and bitumen are denser than conventional crude oil and considerably more viscous, making them more difficult to recover, transport and refine.
Heavy oil is just slightly less dense than water, with specific gravity in the 1.000 to 0.920 g/cc range, equivalent to API gravity of 10 degrees to 22.3 degrees. Bitumen and extra-heavy oil are denser than water, with API gravity less than 10 degrees.
Extra-heavy oil is generally mobile in the reservoir, whereas bitumen is not. At ambient reservoir conditions, heavy and extra-heavy oils have viscosities greater than 100 centipoise (cP), the consistency of maple syrup. Bitumen has a gas-free viscosity greater than 10,000 cP, equivalent to molasses.
The International Energy Agency estimates the total world oil resources are between nine and 13 trillion barrels, of which just 30 percent is conventional crude oil. The remaining 70 percent is unconventional crude divided:
- 30 percent bitumen.
- 25 percent extra-heavy oil.
- 15 percent heavy oil.
Bitumen and heavy oil deposits occur in more than 70 countries across the world. The global in-place resources of bitumen and heavy oil are estimated to be 5.9 trillion barrels (938 billion m3), with more than 80 percent of these resources found in Canada, Venezuela and the United States.
Western Canada has several separate accumulations of bitumen and heavy oil that together comprise 1.7 trillion barrels (270 billion m3). The Oronoco heavy oil belt is a single extensive deposit containing 1.2 trillion barrels (190 billion m3) of extra-heavy oil. Both regions have extensive world-class source rocks and host substantial conventional oil pools in addition to the considerably larger resources within shallow oil sands.
Other countries producing significant quantities of heavy oil and/or bitumen include Russia, China, Iran, Iraq, Azerbaijan, Mexico, Colombia, Ecuador and Brazil.
Globally there are just over one trillion barrels of technically recoverable unconventional oil: 434.3 billion barrels of heavy oil, including extra-heavy crude, and 650.7 billion barrels of bitumen.
Virtually all of the bitumen being commercially produced in North America is from Alberta, Canada, making it a strategic source of bitumen and of the synthetic crude oil obtained by upgrading bitumen.
Estimated remaining established reserves of in-situ and mineable crude bitumen is 167 billion bbls (26.6 billion m3).
To date, just 5.4 percent of Canada's initial established crude bitumen resource has been recovered since commercial production began in 1967. In-situ production using steam-injection overtook mined production for the first time in 2012 and continued to exceed mined production in 2013.
The Faja Petrolifera del Orinoco (Orinoco heavy oil belt) in eastern Venezuela is the world's single largest extra-heavy oil accumulation. The total estimated oil in-place is 1.2 trillion barrels (190 billion m3), of which 310 billion barrels (49.3 billion m3) is considered technically recoverable.
Four active heavy oil recovery projects operating in the Faja, each begun in successive years between 1998 and 2001, produce collectively about 640,000 bopd of average 8.5 degrees API extra-heavy oil using cold production methods, augmented by solvent-injection.
Currently, the United States is producing commercial quantities of heavy oil from sand deposits in two principal areas, the San Joaquin Basin of central California and the North Slope of Alaska.
California's oil fields, of which 52 each have reserves exceeding 100 million barrels (15.9 million m3), are located in the state's central and southern parts. As of 2012, the proved reserves were 2,976 million barrels (473.2 million m3), nearly 65 percent of which is heavy oil in the southern San Joaquin Basin.
In addition to the heavy oil accumulations that are being produced, California has numerous undeveloped shallow bitumen deposits and seeps, a resource estimated to be as large as 4.7 billion barrels (0.74 billion m3).
Alaska's heavy oil and bitumen deposits on the North Slope are very large (24 to 33 billion barrels, or 3.8 to 5.2 billion m3) and they hold promise for sustained commercially successful development.
In virtually all regions of sustained production, the industry is steadily improving in situ recovery methods and reducing environmental impacts of bitumen and heavy oil production, especially those associated with surface mining.
For additional information on current and developing recovery technologies and efforts at environmental mitigation, see the full commodity report from the EMD Heavy Oil and Bitumen Committee at emd.aapg.org/technical_areas/oil_sands/oil-sands-commodity-report-midyear-2014nov.pdf.