production can be obtained by injecting water ("water-flooding") or
natural gas to maintain reservoir pressure and push oil out of the rock. This is
called secondary recovery.
methods are referred to as tertiary recovery. The most common tertiary recovery
method for light and medium crude oil is miscible flooding. In this procedure,
natural gas liquids (ethane, propane and butane) are injected into special
injection wells. When dissolved, these liquids reduce the surface tension and viscosity to help release the oil from the reservoir rock.
has also been used to a limited extent in Canada for miscible floods. This has
the added advantage of using a greenhouse gas that would otherwise be released
into the atmosphere. Three such projects are operating in Alberta and
Saskatchewan. However, this technique is only suitable for certain types of oil
In heavy oil and in-situ bitumen production, enhanced recovery generally involves the application
of heat, most commonly by steam injection. Major improvements in heavy oil and
bitumen recovery have been achieved by SteamAssisted gravity drainage (SAGD)
which uses parallel pairs of horizontal wells for steam injection and oil
Even with all
these techniques, the average recovery in the light oil fields is a little more
than 30 percent of the original oil. The remaining resource represents billions
of cubic metres of oil that has been discovered in Western Canada but cannot be
produced economically with existing technology.
Petroleum Communication Foundation. Our Petroleum Challenge: Exploring Canada's Oil and Gas Industry, Sixth Edition. Calgary: Petroleum Communication Foundation, 1999. With permission from the Centre for Energy.