Challenge: Improve the operational efficiency of perforating in the deepwater presalt environment for large pay zones with elevated formation and hydrostatic pressures while reducing operational risk.
Solution: Push through conventional limits by perforating using the XR-Perf expanded-range wireline perforating system pairing 7-in HSD high shot density perforating gun systems with PowerJet Omega deep penetrating perforating shaped charges for conveyance on TuffLINE 18000 torque-balanced composite wireline cable.
Result: Saved 30 h of deepwater drillship rig time— worth USD 1 million—by perforating 40 m in three runs at 18 h of total operating time and with better management of shock transmission to avoid unintentional pull-off.
Deepwater fields have become common but still pose many challenges in terms of risk, cost, and
productivity. An operator sought to improve perforating efficiency in its deepwater presalt wells,
which in turn would positively address these challenges. For long intervals, the perforating guns
were typically conveyed on pipe. Even in wells with known and established reservoir pressure
characteristics and low gas/oil ratios (GORs), pipe-conveyed perforating took several days at
expensive deepwater rig rates. However, perforating on wireline also posed challenges because
multiple runs were required for long intervals, taking into account the maximum payload that can
be conveyed while withstanding the perforating shock. The combination of elevated formation and
hydrostatic pressures can generate high shock loads on the wireline cable’s weakpoint.
Withstanding the intense peak shock loads generated downhole called for the combination of a strong
weakpoint, high-tension logging unit, and ultrahigh-strength cable. The XR-Perf expanded-range
wireline perforating system provides these robust capabilities by integrating the latest industry-leading
cables, units, and perforating accessories to streamline perforating logistics while avoiding
conventional reliance on pipe conveyance.
To address the expected high pull and shock, TuffLINE
18000 torque-balanced composite wireline cable was
specified. Encapsulation of the cable armor in polymer
prevents rotation, effectively permanently fixing the ends
of the cable to raise the ends-free breaking strength to
27,000 lbf. A high-tension offshore logging unit using
TuffLINE 18000 cable can provide instantaneous pull
of up to 18,000 lbf for stick prevention and mitigation
without a capstan. Multiple high-tension operations can
be conducted, including cycling and jarring, without
compromising the integrity of the cable or having to
interrupt operations to balance the torque of the cable’s
inner and outer armors.
Coupling the high-tension unit and TuffLINE cable with
the strongest possible weakpoint specifically designed
for the operation enables the conveyance of heavy gun
strings while still providing the option to release in the
event of a stuck gun situation.
The interval to be perforated was from 5,625
to 5,665 m in a 9.9-lbm/galUS borehole fluid and
9,500-psi hydrostatic pressure environment.
Schlumberger engineers used proprietary modeling to
accurately calculate the maximum payload and number
of guns to be conveyed per trip by the XR-Perf system
for perforating the 40-m interval without compromising
safety or service quality.
The field crew completed the entire operation including
rig-up and rig-down and three perforating runs in a total
operating time of only 18 h. This saved the operator
approximately 30 h of rig time, which is worth
USD 1 million in this deepwater environment.
In addition to greater efficiency, this first perforating
job with the XR-Perf system and TuffLINE 18000 cable
for the operator also reduced risk. TuffLINE cable’s high
stretch coefficient significantly lessened the amount of
shock transferred to the weakpoint in comparison with
conventional 7-48 high-strength cable, improving shock
mitigation and reducing the likelihood of an unintentional
pull-off as a result of gun shock.
Download: Presalt Perforating Using XR-Perf System with TuffLINE Cable Saves 30 Hours of Rig Time, Brazil (0.44 MB PDF)