Steam assisted gravity drainage (SAGD)
was introduced in the early 1980s as a process for
extracting bitumen from the oilsands. Two horizontal
pipes are drilled into the reservoir parallel to
each other. Steam is injected into the top pipe, and
it heats the bitumen so that it becomes less viscous
and drains into the lower pipe where it is pumped to
the surface to be refined.
SAGD proved to be an effective way of extracting
oil, but the method requires large amounts of energy
and water and can be a major source of greenhouse
emissions. Recently, companies have been forced to
look for ways to improve their efficiency.
Dr. Tawfik Nasr of the Alberta
Research Council (ARC) holds several patents for
inventions that are designed to reduce SAGD’s energy
and water consumption by means of adding a solvent
to the steam injection. The steam-solvent
combination causes more bitumen to drain into the
well and uses up to half as much water, reducing
both energy requirements and greenhouse emissions.
The use of the steam-solvent combination has yielded
a 19 percent increase in oil production over the
standard SAGD, and the product is less viscous and
easier to transport.