One of the bleakest scenes of man-made destruction is the strip mining of oil sands in the forests of Alberta, Canada. The sand is permeated with natural bitumen, a type of petroleum with the consistency of peanut butter. Once dug from the surface, the sand is hauled to an extraction plant where it is mixed with lots of hot water and chemicals to liberate the oil and make it flow into pipelines or be taken by tankers to refineries. Not all of the water can be recycled and what remains is a goopy toxic waste contained in some 170 square kilometres of man-made ponds.
It is hardly surprising that environmental campaigners want to restrict or shut down the growing “tar sands” industry, as it is also called (as tar is a man-made substance, the industry uses the term oil sands). But the commercial stakes are high. Only Saudi Arabia and Venezuela have greater proven oil reserves than Canada, but 97% of Canada’s 174 billion barrels are in oil sands, mostly in Alberta.
In the past decade high oil prices have made the oil sands profitable to exploit. But the oil industry, whose reputation for protecting the environment is already poor, has come under pressure to find more efficient and cleaner ways to extract the oil. The results of that innovation are now starting to be deployed.
Many operators now extract the bitumen without strip mining. “In-situ” production, as it is called, involves injecting high-pressure steam, heated to more than 300°C, into deep boreholes. The steam, emerging from millions of slits in a steel borehole liner, liquefies the bitumen and allows it to be pumped out.
Using steam extraction means that nine-tenths of the land above a reservoir can be left intact. There is no need for waste ponds because the sand is left underground and most of the water recovered from the bitumen can be cleaned with distillation for reuse. Steam can also produce bitumen from a reservoir half-a-kilometre underground, whereas strip mining is only economical for deposits less than 70 metres or so from the surface.
The proportion of bitumen produced with steam now stands at 53% and will continue to grow, says the Alberta Energy Regulator (AER), a government agency. One of the newer methods, steam-assisted gravity drainage (SAGD), has proved particularly effective, says Ken Schuldhaus of the AER. SAGD involves drilling two horizontal wells through an oil-sands reservoir, one about five metres below the other. Steam is then released from the top well and over a few weeks can melt bitumen as far as 50 metres above and to the sides of the bore. The bitumen then percolates down and into the lower well, from which it is pumped to the surface.
All that gas