From the air, the landscape surrounding Fort McMurray in northeastern Alberta is a patchwork of boreal green stitched together with brown-grey surfaces from mines, refineries and tailing ponds full of oily, clay-filled water. The ponds — containing residue created when bitumen is separated from sand — cover more than 170 square kilometres, up from 50 square kilometres just seven years ago. An eyesore as well as an environmental blight — 1,600 waterfowl died after landing in one pond in 2008 — mounting public pressure has secured pledges from government bodies like the Energy Resources Conservation board (ERCB) to halt the proliferation of tailing ponds by 2016. Unfortunately, these targets are not being met, ERCB reported this past June. So far, only one tailing pond has been successfully reclaimed and replanted: Suncor’s 220-hectare Wapisw Lookout, or Pond 1, in 2010.
Oil sands companies may not be meeting targets, but they are making efforts to speed reclamation and improve their green credentials by reducing the amount of water and energy used to extract oil. Experiments include the use of flocculants — substances that promote clumping — to help settle out tailings ponds more quickly, as well as solvents instead of water to ‘dry clean’ bitumenous sands or bring deep oil up to the surface more easily. “No matter what you do you’re harming the environment, but we want to lower this footprint,” says Jalal Abedi, head of the Solvent Heat Assisted Recovery Processes (SHARP) research consortium at the University of Calgary. “The companies are all trying really hard to make this happen,” says Abedi, who is also an associate professor of chemical and petroleum engineering at U of C.
There are currently two types of oil sands extraction in Alberta: surface mining and in situ, each requiring different technologies. Surface mining, historically accounting for slightly more than half of oil sands production, has drawn the majority of complaints about environmental impacts. After being dug out of the oil sands by 400-tonne trucks and shovels, the bitumen is separated from the sand by mixing it with warm water. The resulting froth is skimmed off and processed, leaving behind large amounts of watery waste that fills up tailing ponds. Although only 10 per cent of Alberta’s oil resources is shallow enough to be mined this way, the Canadian Association of Petroleum Producers (CAPP) reports that production from surface mining is rising quickly, and expected to increase by 50 per cent by 2020.
To clean up surface mining, the idea is to replace water for washing with solvents, preventing the creation of new tailings ponds. Almost any kind of solvent will work but some are better than others, says Murray Gray, director of the Centre for Oil Sands Innovation (COSI) at the University of Alberta. A good solvent, Gray says, needs to reduce bitumen viscosity enough to beat the 90 per cent recovery rate achieved by water washing alone. It also needs to have a boiling point lower than water so it can be recovered easily. Ideally, the solvent would be non-toxic and biodegradable. Solvents currently used in lab settings, such as toluene and xylene, can’t be used due to high toxicity, Gray adds.
The tough thing is getting a solvent that will leave the fine solids or clays — mostly particles of silicon dioxide and iron minerals — with the sand, rather than pulling them out with the bitumen, says Gray. Those fine particles, which end up in tailings ponds, also gum up devices used to transport and refine the extracted oil, so the less of it that is extracted, the better. COSI is also looking at the environmental effects of the solvents by studying how well they are consumed by microbes. There’s no shortage of data for that, Gray says, thanks to fuel storage tank leaks. “There have been a lot of experiments inadvertently across North America and worldwide on gasoline release into the environment.”
COSI has partnered with Imperial Oil, which is now deciding whether to launch a full-scale, $50 million pilot project using solvents in their surface mining efforts. “We are advancing plans for a potential field pilot plant,” says Imperial Oil spokesperson Pius Rolheiser.
The other type of oil sands extraction — in-situ production — has an entirely different set of problems. Ninety per cent of Canada’s reserves are too deep to surface mine, so oil must be encouraged to flow up through a pipe. The challenge is the bitumen’s viscosity: on a cold day it flows like molasses. For regular oil, a well is drilled into the deposit and it flows up the pipe on its own. As a well starts to dry up, the remaining oil can be forced out by injecting water, natural gas or carbon dioxide (CO2). Later, steam can be injected or some of the oil burned, aiding in recovery by heating the remaining oil. But tarry oil sands take more effort: lots of 200 C steam is required to make the oil flow well enough to reach the surface. This doesn’t create tailings ponds, but it does use a lot of water and energy. In-situ production is expected to double by 2020, according to CAPP.
To reduce the environmental impact of in-situ sites, the idea is to reduce the need for hot steam by using a solvent like methane, ethane or naphtha to dissolve some of the carbon chains and make the oil less viscous. “Companies can often double their rate of extraction, which means using half as much steam, thus dramatically cutting energy costs,” says Gray.
Researchers face significant technical challenges trying to reduce the environmental impact of bitumen extraction. Photo credit: Julia Kilpatrick, Pembina Institute.
To find out which solvents work best, Abedi’s SHARP research consortium has funding from 14 industry partners as well as NSERC. They aim to answer basic questions about how oil sands behave when mixed with different solvents at the high temperatures and pressures found at in-situ deposit depths. SHARP’s researchers have designed a custom-built system that allows them to easily detect which carbon-chains are separated out by which solvents in these conditions.
The data produced helps companies predict how much bitumen can be recovered using specific solvents and how refined it will be when it gets to the surface. A variety of solvents separate out contaminants to different extents. These contaminants include heavy metals like mercury and arsenic, as well as sulphur and asphaltene, a tarry substance that gums up pipelines and machinery. By using a solvent at low temperature, instead of steam at high temperature, some of these problematic compounds never become mobile and remain under ground.
So far, results have been inconsistent for companies that have tried solvents in their in-situ extraction. “Some companies have done it and it has not succeeded,” says Mohammed Al-Murayri, head of the industry advisory group for SHARP and a technical manager for the oil and gas company Nexen, which is planning its own solvent trials in 2014. Back in 2002, Canadian oil company Cenovus Energy undertook a trial of a Solvent Aided Process (SAP) using butane and saw a 30 per cent reduction in its need for steam. How it worked was controversial. “Some people thought they were only displacing their steam-exposed bitumen, rather than diluting it,” says Al-Murayri. Still, he says, “it was a step in the right direction.”
In 2005, Imperial Oil started adding solvents to its project at Cold Lake, Alta. Its Liquid Addition Solvent for Enhanced Recovery (LASER) process used both propane and steam, Rolheiser says. Although it didn’t reduce the amount of water needed by much, LASER did recover up to 30 per cent more bitumen than by steam alone. Now Imperial is investing $100 million in a field pilot test at Cold Lake that uses all solvent (primarily butane) and no steam at all, says Rolheiser, potentially reducing energy requirements enough to chop greenhouse gas emissions by 65 per cent.
Technology company N-Solv Corp. has a similar project planned for Suncor’s Dover, Alta. site. This fall, it started pumping 50 C butane vapour down a well, says N-Solv vice-president of business operations Alexander Stickler. Stickler predicts this should lower the lifecycle CO2 emissions of the oil by 85 per cent.
Unless all oil companies switch to using solvents instead of water in surface mining, tailings ponds will still be a problem for a while to come. Companies are using a variety of technologies to speed up the separation of sediment from the tailings, making it faster and easier to reclaim the land. This includes simple filtering. Since 2012, for example, Syncrude has run a commercial-scale demonstration of a centrifuge to accelerate the tailings separation process. Other creative ideas include zapping ponds with a current to force negatively charged clay particles over to one side, or letting off explosives to help shake sands into a more-compact mass. However, these haven’t proven economical yet.
Chemical processes stand a much better chance than physical ones of cheaply accelerating tailings separation, concludes a 2010 report by consultant BGC Engineering for the independent Oil Sands Research and Information Network (OSRIN). There are plenty of options. Suncor Energy, for example, mixes its tailings with a polymer flocculent before spreading it over sand ‘beaches’ with shallow slopes on the shores of its tailings ponds. This Tailings Reduction Operations technology reduces the time needed for tailings pond reclamation to 10 years from 30 years, reports Canada’s Oil Sands Innovation Alliance (COSIA). The clay-with-polymer waste can also be used in construction materials, says Suncor.
Calgary-based Canadian Natural Resources Ltd. has inventively used waste CO2 as a flocculent. Since 2009, the company reports it has injected more than 58,000 tonnes of CO2 into tailings at its Horizon Oil Sands facility, 70 kilometres north of Fort McMurray.
It isn’t clear whether any of these new technologies will generate environmental concerns; the creation of dry, solvent-based wastes might also be problematic. “I am uncomfortable about whether we know enough about these as an alternative to tailings ponds,” says U of A ecologist David Schindler, who worries about the possible presence of sulphuric acid in these tailings. “There’s potential to reduce the energy intensity, but there are potentially other issues in terms of disposal,” agrees Simon Dyer of the Canadian environmental advocacy group the Pembina Institute.
Whether any of these innovations will happen at a scale and speed necessary to meet targets for tailings ponds reduction is also still in question. “Despite all the buzz about new technologies that companies are trying, actual performance has been a complete failure,” says Dyer. For Dyer and others concerned about the rapid growth of oil sands mining, the best solution would be to slow down. At the current rate, Dyer says, clean-up and pollution mitigation will find it hard to keep pace with industry growth. “We support innovation,” he says, “but many of these innovations are going to be too late.”