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Home > Alberta's Resource Inventory > Hydrocarbons > Oil Sands Resources > Heavy Oil Characteristics > Algae, Bacteria and Bitumen

Resource Inventory

Algae, Bacteria and Bitumen

Rock sample from the Canadian Petroleum Interpretive CentreLike all crude oil, Canada's bitumen and heavy oil resources started as living material. Hundreds of millions of years ago, the remains of tiny plants and animals—mainly algae—were buried in sea beds. As the organic materials became more deeply buried, they slowly "cooked" at temperatures between 50 and 150 degrees Celsius. Eventually, this process converted the materials into liquid hydrocarbons (compounds of hydrogen and carbon), as well as sulphur compounds, carbon dioxide and water.

The hydrocarbons then migrated up through sedimentary rocks until they reached the surface or something blocked their progress. Conventional light crude oil is usually trapped in porous rocks under a layer of impermeable (non-porous) rock. In such reservoirs, the oil is not in an underground "lake" but rather held in the pores and fractures of rock like water in a sponge.

Oil sands are different. Fifty million years ago, huge volumes of oil migrated eastward and upward through more than 100 kilometres of rock until they reached and saturated large areas of sandstone at or near the surface. Bacteria then feasted on the hydrocarbons and slowly turned the oil into bitumen. While the Athabasca oil sands are the world's largest known hydrocarbon resource, geologists point out that the volume of original crude digested by the micro-organisms was at least two or three times greater than what now remains as bitumen.

Bacteria always eat the simplest hydrocarbons first and convert them into carbon dioxide and water, while ignoring the big hydrocarbon molecules like asphalt and the non-hydrocarbons, such as sulphur and nickel. As a result, there are more heavy hydrocarbons, sulphur compounds, and metals in bitumen than in conventional crude oil. This makes processing more difficult and expensive.

The challenge of the future lies in continuing to develop these oil sands and heavy oil resources to meet the fuel needs of North America in a way that is economical and sensitive to the needs of regional residents and the quality of the natural environment. 

Petroleum Communication Foundation. Canada's Oil Sands and Heavy Oil. Calgary: Petroleum Communication Foundation, 2000. With permission from the Centre for Energy


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