target reservoirs are at a true vertical depth SAGD programs often employ large pads The selection of drilling mud, directional
between 200 metres to 500 metres, and stemming multiple well pairs, in what is tools and drill bits is also important for
Husky engineer Wilson says some are even sometimes called a “batch drilling effective SAGD. As well, operators must
closer to the surface. The depth of the wells process.” This essentially allows operators employ magnetic ranging technology to
determines what kind of rig is required, says to drill a number of wells at the same ensure the two wells stay parallel in the
Precision Drilling’s Charles Gowler. time, methodically drilling each section of reservoir.
the well in an assembly-line process.
“Wells having a true vertical depth of less
than 160 metres require rigs with slant
capability,” he explains. “Current
technology enables wells to be started at
any angle, but spud angles from 45
degrees to vertical are most popular
because of rig availability.”
“This is more like a manufacturing line
than your conventional oil and gas
exploration situation,” says Tenaris’ Ryan
“The technology that allows us to drill
the injector well above the producer is
very complicated,” Wilson explains.
Schoenhals. “Reliability, repeatability and Rotating magnetic ranging (RMR) is the
cycle times are becoming very important new alternative to the method currently
in SAGD drilling.” in use, says Mark Stevens with
Directional Plus. Instead of placing the
magnet in the liner of the production
well, it can now be placed in the open
hole of the injector. RMR employs a
permanent magnet directly behind the
bit to generate a time varying magnetic
field as the bit rotates, a signal that is
detected by sensors in the other well.
“RMR has been successfully tested in
SAGD projects and has shown to be
capable of correctly positioning new
injectors above previously drilled and
cased production wells,” Stevens says,
adding that in these operations the
sensor package is either pumped down
tubing installed in the producer or run
in the hole using the tractor method.
“Whatever we’re doing in the injector,
we can see in the producer,” Wilson
says.
After the wells are drilled, they must be
cased and cemented. Cement plays a
vital role in SAGD wells, as it is what
keeps the operation stable when
dealing with steam temperatures as
high as 300 degrees Celsius, and
temperature fluctuations. In target
formations, Suncor’s Mack Kay says the
bitumen bearing sands generally lie
below a layer of shale, which acts as a
sort of seal. However, when a wellbore is
drilled through it, that seal is broken.
“You can’t let the steam come to the
surface,” he says. “That’s the importance
of having a good cement job. Once you
bring the thermal element into it, it’s a
whole different ball game.”
SAGD wells not only have to withstand
high temperatures but also intense
swings in temperature. When steam
injection begins, the formation quickly
goes from ground temperature to very
hot, and when operations are shut
down for activities like maintenance, the
temperature shifts the other way.
Tenaris’ Schoenhals says it is the change
