Oil Sands & Extraction Techniques
Oil sands are deposits of crude that are much heavier than other
crude oils; and consist of water, sand, mineral rich clay and
bitumen. The oil sands in Alberta, Canada are considered one of
the largest in the world; located in Peace River, Cold Lake and
Athabasca. The total area covered by these deposits is 54,400
square miles and contain approximately 1.6 trillion barrels of
bitumen - of which 174 billion barrels are proven reserves and
can be recovered using current technology. The vast hydrocarbon
deposits of the Alberta Oil Sands creates additional,
challenging problems for scientists and engineers as they seek
more efficient and economical ways to recover the tar-like
bitumen. Mining and in-situ are the common methods used to
extract the bitumen from the oil sands, and they are discussed
below.
Mining
Oil sand mining is an open pit mining technique that can be done
where the mineable bitumen deposits are located near the surface
of the earth. This process begins by clearing trees, draining
and storing the overburden, and then removing this top layer of
earth to expose the ore body. Oil sands are moved by heavy
equipment such as trucks and hydraulic shovels to a special
cleaning facility where the substances are mixed with hot water
and caustic soda to separate the bitumen from the sand,
minerals, and water. Oil sands mines in operation are located
near onsite upgraders that convert the bitumen to a form of
synthetic crude oil.
In-Situ
For oil sands that are too deep to support surface mining
operations to an economical degree, some form of an in-situ or
in-place recovery system is necessary to produce the bitumen.
This method is used in approximately 80 percent of the ways that
bitumen is eventually recovered. Due to the fact that bitumen
will not flow under normal conditions because of its heavy
viscous nature, numerous in-situ technologies have been
developed that will allow easier movement and flow. In-situ oil
sands production is similar to that of conventional oil
production - where oil is recovered through wells. Two of the
more common methods of In-Situ are listed below.
Cycle Steam Simulation- In order to soften the oil sands before
pumping begins, high-pressure steam is injected into the oil
sand formation for several weeks. The heat softens the oil sand
and the water vapor helps in breaking up the bitumen from the
sand. The pressure that has been created causes cracks to be
formed that assist in moving the bitumen to producing wells.
After a section of oil sands have been saturated the steam is
removed and the area is allowed to sit for several weeks,
soaking up the moisture and steam. The bitumen will begin to
flow more freely and than can be pumped up the well to the
surface, and if the production rates begin to fall the cycle
steam simulation process is repeated.
Steam Assisted Gravity Drainage - This technology requires the
horizontal drilling of two parallel wells through which steam is
pumped into the upper well creating a high temperature chamber
that serves to heat and loosen the thick bitumen. The heated
bitumen is then pumped to the surface via the second horizontal
well. This is one of the most popular and cost effective
methods.