Save well with internally cemented drillpipe
After a failed cementing job in one of its exploration wells in
Colombia, Pacific Rubiales found that cement had accumulated on the ID of the
drillpipe at a depth of 3,305 ft [1,007 m]. However, initial cement
displacement calculations indicated that annular cement had reached a depth of
4,665 ft [1,422 m], which was 300 ft [94 m] below the casing shoe.
Because of the wells 90° deviation, backoff or cutting
operations on wireline were not feasible, and there was no chance of restoring
circulation with wireline toolscoiled tubing was the only option. Pacific
Rubiales sought a solution to recover the cemented pipe section and
successfully perform an openhole sidetrack to save the well.
Use TT milling and TT underreaming tools for effective hole
Schlumberger recommended running a TT mill, a TT underreamer, and a 2
1/8-in TT motor on 1 1/2-in coiled tubing for effective hole cleaning. For the
milling operation, low- and high-rheology pills were also chosen to help
recover the cement that accumulated on bottom and to render motor
The TT underreamer selected is designed to pass through borehole
restrictions and to hydraulically open to a preset diameter of 3.34 in, the
drillpipe body ID. The TT underreamer effectively removes cement, scale, and
hard debris from the liner below the production string.
After milling with a 2 5/16-in junk mill, a cake of cement would remain
on the pipe wall and anchoring would not be properly performed. An
underreaming-only run was completed above the last tool joint to remove the
cake using the 2 1/8-in TT underreamer dressed with milling knives that open to
3.30 in. Cement was also cleaned below the tool joint to ease the opening of
the cutter knives.