TECHNOLOGY
Horizontal drilling technology has revolutionized the
oil and gas industry, and has led to exciting technology development in heavy oil production. VAPEX is an
example of leading-edge technology being used in the
heavy oil sector. It is a non-thermal recovery method
that uses gaseous solvents to increase oil recovery
through reduction of oil viscosity, in situ upgrading,
and pressure control.
The basic design of VAPEX uses horizontal well pairs
spaced approximately five metres apart. A gas/solvent
mixture is injected into the reservoir through the upper
VAPEX
well to stimulate the heavy oil. Its viscosity reduced, the
lighter oil then drains via gravity to the lower produc-
tion well. This method is similar to solvent flooding.
VAPEX works best when the dew-point pressure of
the injected solvent is just below the reservoir oper-
ating pressure. This is achieved by co-injection of a
non-condensable gas, such as methane, along with
VAPOUR
the solvent. However, the higher solvent concentration
in the oil results in more methane in the accumulated
gas, which means a reduced concentration of vapour-
ized solvent in the vapour chamber, reducing the
effectiveness of the process. New techniques, such as
the addition of gases like carbon dioxide and sulphur
dioxide, are being developed to control solvent con-
centration in the gas phase.
VAPEX operations are extremely expensive due to
the cost of the solvent and the associated risk of not
recovering the solvent from production. If thermal
EXTRACTION
recovery such as air combustion follows VAPEX, then
significant amounts of the solvent might be recovered.
With that, researchers are investigating the use of
heavier solvents, as they may promote in situ deas-
phalting. The asphaltene residue would then be the
fuel source for in situ combustion.
Although not considered to be fully commercial, a con-
siderable amount of joint industry work has been com-
pleted around VAPEX. Work continues to expand the
use of the technology into heavier oil reservoirs such
as the oilsands. Successful application of VAPEX along
with thermal processes could significantly reduce
greenhouse gas emissions.
Companies currently testing VAPEX technology:
Petro-Canada, Nexen, EnCana, the DOVAP joint
Commercial VAPEX
could substantially
reduce greenhouse gas
emissions.
