in temperature, and not the operating “We need to make sure the behaviour SAGD world, you couldn’t do that
temperature, that presents the challenges. after the yield point is something we can anymore.”
The cement, along with the pipes and predict. Post-yield mechanical properties
connections respond to the heat, and if are important when deciding what kind After the well pairs are constructed,
the well is not designed properly this can of steel to use.” operators must choose which form of
cause serious problems. artificial lift to use. Even though the
bitumen’s viscosity has been decreased, it
still does not flow efficiently on its own.
Selecting the right liners is another
“Over the life of the well pair, it’s not going important aspect of SAGD. Regent
to stay the same temperature. As all of this Control Systems’ Butch Loewen says
steel in the well gets exposed to the steam seamed or slotted liners, which are
it wants to expand,” he says. “The force manufactured from 4.5- to 10.5-inch
that would be generated would be thermal grade casing, have become the
massive.” liner of choice. The liner is slotted using
circular cutter blades for accuracy, and
All materials have a yield point, or a point slots are generally between 0.01 and 0.3
at which they will fail. Schoenhals says it is inches.
inevitable in SAGD operations that the
pipes and connections will be stressed
beyond their yield point.
“There are several lift mechanisms in
place in the SAGD production wells
including electrical submersible pumps
and progressing cavity pumps, but the
dominant lift mechanism is called ‘single
point gas lift,’” says Halliburton’s Wayne
Redecopp.
After cleaning with a hot pig process, the In the world of oil sands production,
liner is seamed, narrowing the slot to a SAGD is an infant, but one that has
keystone shape, which is self-cleaning, proven highly successful and attractive
“No matter what we do, this tubing is going excludes sand and reduces slot plugging. for operators large and small. However,
to fail. It’s such a demanding application. Both the production and injection wells the projects continue to evolve as
Things are going to start to move.” generally employ slotted liners, and operators face challenges like minimizing
Loewen says the application has evolved the need for natural gas and managing
in a relatively short period. water more efficiently.
Because of this, pipe and connection
designers have had to change their
thinking. He explains that while about 96 “For years, there was no science or
per cent of wells are designed for engineering [to slotted liners],” he
optimum strength, SAGD materials have explains, adding the costs and
to be designed for their response to commitment involved with SAGD make
strain. that approach inappropriate. “In the
“SAGD is going to be a major part [of the
industry] for a long time,” says Tenaris’
Schoenhals. “The process now is to
improve, optimize and customize it to a
new level.” ■
