Tension in excess of 10,000 lbf

While the 12 1/4-in section of a deepwater well in the Eastern Mediterranean well was being deepened, the drillstring got stuck. When the operator resorted to a 35° sidetrack, revision of the logging tension simulation predicted that tension would exceed 10,000 lbf. Schedule constraints and the remote location of the well prevented mobilizing a capstan in time to evaluate the 8 1/2-in section to total depth. The high probability of tool sticking occurring favored the alternative approach of drillpipe deployment to convey the wireline tools for a complete petrophysical evaluation, including pressure measurement, fluid sampling, and obtaining sidewall cores. However, this approach would require an additional 7 days of deepwater rig time to conduct.

Efficient cable deployment that also reduces risk

Schlumberger suggested short-notice deployment of TuffLINE 18000 torque-balanced composite wireline cable by airlifting a cable drum from a UK base in time for the 8½-in section. TuffLINE 18000 composite cable integrates the breakthrough technologies of polymerlocked armors and crush-free electrical cable cores to effectively overcome the fundamental limitations of current armored cables. The resulting torque-balanced condition maintains a consistent state of low torque to prevent birdcaging and premature cable breakage. Multiple high-tension operations can be conducted without compromising cable integrity while eliminating the requirement for seasoning of new cable and cable swapping for extended logging operations.

Because the polymer locking of the armors prevents rotation, TuffLINE 18000 cable is effectively in a permanent ends-fixed state, which raises the ends-free breaking strength to 27,000 lbf. That is only 1,000 lbf below the ends-fixed breaking strength and delivers a breaking-strength safety margin of 9,000 lbf above the safe working load. At these values, the risk of cable breakage occurring because of accidental overpull above the safe working load is significantly reduced to greatly improve performance while reducing operational risk compared with deployment on a capstan.

Successful wireline operations at high tension

Despite logging tensions that exceeded 10,000 lbf on all descents, multiple pulls to 16,000-lbf tension, and repeated cable cycling, no tool sticking occurred for all deployments on TuffLINE 18000 cable for petrophysical logging, formation pressure measurement, formation fluid sampling, and sidewall coring.

Additional benefits of using TuffLINE 18000 cable were that:

• full data acquisition was completed in a record 3 days, saving 4 days of rig time and USD 5 million
• capstan mobilization and its associated operational and logistical risks were avoided
• tension cycling successfully prevented fishing, without the risk of torque-related cable breakage
• cable seasoning was eliminated to save 1 day of rig time
• cable maintenance trip was not necessary after the job, which would have been expensive and logistically challenging for this remote operation.