What's new in production

 Vol. 233 No. 9

The Athabasca River in Alberta starts out clean. Most rivers do, too, I suppose, but this one begins as meltwater from the Athabasca Glacier in the Columbia icefields of Jasper National Park. The water reaches a liquid state for the first time since falling as snow thousands of years ago, and is quite pure and drinkable (you can purchase a bottle of Athabasca glacier water, if so inclined). It’s what happens to that water as it flows downstream—to Great Slave Lake and, eventually, the Arctic Ocean—that has been the subject of so much discussion, because its course runs through the bituminous sands, in and around Ft. McMurray, Alberta.

Canadian synthetic crude production stands at about 1.5 million bpd. Since it takes between 2.0 and 4.5 bbl of water to produce a barrel of syncrude, a lot of the Athabasca is utilized. Currently, the five main companies producing oil from the sands—Suncor, Syncrude Canada, Shell, Canadian Natural Resources and Imperial Oil—utilize about 170 million m3 (1.07 billion bbl) of water from the river. This is less than half the total allowable.

In 2006, the Canadian National Energy Board (NEB) projected that by 2015, 4.4 million bpd of syncrude would be produced, requiring 529 million m3 (2.3 billion bbl) every year. That would equal 2% of the Athabasca’s total flow. Today, that forecast may seem dreamy, but with oil prices above $90/bbl, even the very expensive-to-produce oil looks promising.

Water is used, both for mining extraction and for in-situ recovery of bitumen with steam-assisted gravity drainage (SAGD), about 83% and 17%, respectively. Some saline groundwater is also utilized. The recovered production water is brackish, alkaline and generally toxic to aquatic life. Since there is a zero-discharge policy, none of that water can be returned to the river. Between 80% and 95% of the water is recycled.

Cannons and “bitu-men.” Recycling significantly reduces the amount of river water needed for the oil sands projects, but recycling has its limits. Repeated extraction cycles cause the water quality to deteriorate, which creates problems in bitumen extraction, as the water becomes more foul and corrosive. Eventually, the water must be pumped into tailings ponds. The ponds cover more than 50 sq mi, greater than double the size of Manhattan. They are attractive to waterfowl, but also toxic to same, so companies are required to take aggressive steps to shoo them away. Methods range from horns to flashing lights to noise cannons to scarecrows (“bitu-men”).

“Settling,” the process of returning these ponds to something like normal wetlands, takes anywhere from a few years to as many as 30, and the ponds are still growing. It is the official goal of Alberta’s government to speed up the reclamation process and, eventually, eliminate the tailings ponds altogether. Last February, the government announced a C$50-million/yr monitoring strategy that would significantly increase water, air and ground testing for toxins.

Micro, ultra, nano. Emerging water-treatment technologies can both increase the number of times that water can be used in bitumen recovery, and make it cleaner before discharge. These methods can include, 1) adsorbtion using any number of substances, such as activated carbon, organic material, polymers, clays and zeolites; 2) micro- and ultrafiltration; and 3) nanofiltration and reverse osmosis.

The differences among the micro, ultra and nano varieties of filtration depend on scale. A microfilter removes a particle as small as 0.1 micrometers, and an ultrafilter removes particles down to 0.01 micrometers. Nanofiltration can reject some dissolved minerals, softening the water, while reverse osmosis—water forced against a semi-permeable membrane—can remove up to 98% of dissolved minerals and virtually all pathogens.

GE’s ZeeWeed water treatment system consists of modular components that can be grouped and scaled to clean large amounts of water. The system is comprised of “modules” containing many thousands of vertical membrane fibers, each with millions of micro-pores. Water is drawn into the fibers and filtered through the pores. The modules are grouped to form a “cassette” with various configurations, depending on water quality and volume. Cassettes are joined to form “trains,” and a series of trains forms a treatment plant. To prevent the system from being fouled, the particles are removed periodically using a “backwash” process, where water is reversed through the system and aeration breaks the particles loose. Suncor has been using the ZeeWeed process to treat water for its Firebag and MacKay River in-situ sites.

As an alternative to injection, produced water that is not recycled can be concentrated using reverse osmosis, evaporation or some other liquid-reducing technology, then made into solid residue with a crystallizer. The solidification process may also involve mixing a solidifying reagent with the crystallizer waste slurry to produce solid waste for disposal in a landfill. This is a true zero-liquid-discharge (ZLD) system, as all water becomes vapor.

When water is discharged as steam, it does end up back in the rivers and lakes, when it falls as rain or snow. Some of that may even end up in the glacier where it started. By the time it appears again as liquid water, oil sands production might not even be happening anymore.