Avoid heat chunking and forming debris debris in long-lateral HT well
A customer in West Texas, USA, needed to bring a completed well into
production. The final stage of the work was to mill out 26 frac plugs
throughout the horizontal part of the 5 1/2-in completion.
The first challenge was that the bottomhole temperature of the
horizontal section was 340 degF, and most elastomer-based thru-tubing motors do
not survive such a high temperature due to premature chunking. A competitor
proposed an option that would complete the job in three runs, milling a maximum
of six plugs per run while anticipating a milling time of at least 30 minutes
per plug. The customer faced a total projected time of 65 hours.
Additionally, the prejob design projected that the horizontal section
was long enough to create several debris beds if the flow was insufficient for
debris removal through the annulus. The third party only offered a motor that
could circulate at peak 3.5 bbl/min—a minimum possible flow rate.
Schlumberger calculated that a successful job should have an optimal flow rate
of 4.5 bbl/min.
Use DynaForce TT motor assembly with NBR-HR elastomer
Schlumberger proposed a BHA combining a 3 1/8-in DynaForce TT motor with
a 7/8 3.3 motor injected with proprietary NBR-HR elastomer and a 3-loose fit,
2US rotor, and 10S stator. This configuration improved elastomer swelling
conditions at bottomhole, providing the necessary torque for milling plugs. It
also enabled the operator to continuously maintain a flow rate of 4.5 bbl/min,
with peaks of 5 bbl/min if additional annular velocity is needed.
Eliminated 2 operation days and reduced costs
The operator completed the job in 12 hours with a single run, saving
more than 2 days of operation compared with a third-party proposal. All the
plugs were milled at an average of 18 min per plug—12 minutes quicker per
plug than calculated during prejob design.
The motor experienced no stalls during the job. Postjob evaluation and
surface testing of the unit revealed that the motor was in condition to
complete a similar job on a subsequent well in the same pad.