With temperatures up to 350 degrees C and multiple heating-cooling
cycles, thermal oil production presents down hole tubulars
and connections with the most severe conditions found in the
industry. As a result, it is critical that operators of SAGD (Steam
Assisted Gravity Drainage) and CSS (Cyclic Steam Stimulation)
projects, popular in Canada’s heavy oil reservoirs, have complete
confidence in the casing and connections they install in their wells,
as the potential consequences of failure are severe.
Previously, no recognized industry standard existed to evaluate
candidate connections for thermal operations where stresses
beyond the elastic limit of the steel tubulars are generated.
Operators were left to rely on internally developed qualification
guidelines for specific projects, and in this rapidly growing and
fast moving segment, there was a clear need for a detailed,
globally recognized standard.
Together with several thermal well operators, other manufacturers
and industry resources, Tenaris participated in a multi-party project
that resulted in the development of the Thermal Well Casing
Connection Evaluation Protocol (TWCCEP) in May, 2010.
TWCCEP is now a recognized industry standard and voluntary
qualification process to evaluate connections for thermal operations
where maximum temperatures range from 180°C to 350°C.
Since the inception of TWCCEP, Tenaris has tested and qualified
three TenarisHydril Blue® connections.
Establishing an industry protocol
Major CSS projects have been operating in Canada for more than
25 years, and the newer SAGD application has been implemented
at several projects in the last 10 years.
The industry has been witness to serious failures that have
occurred intermittently in the past, but with massive expansion of
thermal projects planned in the future, there was a clear need to
implement a qualification protocol to ensure that the risk of casing
connection failures was minimized.
Through a multi-party project, the TWCCEP was established.
The protocol requires testing of connections under worst-case
scenarios for a particular design considering the assemblage in
the well and the operation during both steaming and producing.
Connections shall undergo mandatory and optional tests to
determine whether they are suitable for thermal well service.
Mandatory tests assess galling resistance, structural strength and
sealability. These characteristics are determined through make-up
and break-out cycles, thermal cycling and tensile testing at
increasing temperatures. Additional, optional, testing can be
conducted to assess the performance of connections in loading
conditions that are not consistent with all thermal well
applications. Optional testing shall include a bending test and a
limit-strain test. In all cases, test specimens shall comply with the
very demanding seepage thresholds representing the operation
in the well.
The next step following the release of the testing protocol was
to conduct a full-scale physical test of a casing connection in
accordance with the new TWCCEP guidelines.
A 9 5/8” TenarisHydril Blue® connection was chosen, as this
casing size is utilized in several SAGD projects. Additionally,
the TenarisHydril Blue® connection was deemed an appropriate
connection for testing due to its suitability for intermediate
casing applications, where thermal wells endure the most
rigorous demands. The testing was undertaken at Tenaris’s
R&D facility in Campana, Argentina from August 2010 through
Subsequently, Tenaris selected two additional sizes, 11 3/4” and
13 3/8”, of TenarisHydril Blue® connection for evaluation.
In all three qualifications, six specimens were tested and, in
accordance with the protocol, four were subjected to ten thermal
cycles each in various specification combinations. To ensure
the simulation represented the “worst case scenario”, different
combinations of thread interference and seal interference were
The 9 5/8” TenarisHydril Blue® connection was the first connection
to successfully complete a testing program in accordance with the
new protocol. The test results exceeded expectations, with seepage
rates well below the requirements of the protocol. A Canadian
thermal operator participated in the testing program and had
third party inspectors monitoring all test activities, with no nonconformances
being noted. Subsequent successful tests of two
other sizes of TenarisHydril Blue® connections demonstrate Tenaris’s
dedicated response to its customers’ most demanding application
With nearly 2 million meters / 6.5 million feet of TenarisHydril
Blue® connection run as intermediate casing in thermal operations
since 2004, TenarisHydril Blue® serves as the foundation of Tenaris
participation in the thermal segment in Canada.