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Kick while disconnecting for hurricane suspension

IOGP Well Control Incident Lesson Sharing #24-3

During drilling of 8.5” reservoir section, a hurricane was forecast in the area. While POOH BHA for suspension, a combination of insufficient mud weight and well monitoring on tight drilling mud window caused a swab kick. Well was killed with heavy mud riser cap, in order to accelerate abandonment operations. Back on location, used same well killing operation to control well. Post mortem analysis indicated ESD information did not reach mud engineer, which could help mitigate poor fluid treatment/contamination.

The IOGP Wells Expert Committee/Well Control Incident Subcommittee believes that this incident description contains sufficient lessons to be shared with the industry. We further encourage the recipients of this lesson sharing to share it further within their organization.

What happened?:

Drilled 8.5’’ reservoir section to 30,453 ft (9282m) with 15.9 ppg DHEMW.

A hurricane was forecast in the area. Decision to POOH for suspension (storm packer) and be ready for disconnection.

Kick Detection:

• Static one hour flow check on bottom.
• Pump out of hole to top of 11 7/8" liner at 25,000ft, 8ft inside 14" casing (12.36" ID) with 8-1/2" BHA, proper displacement observed. Static 30 min flow check reported.
• Pull 5 stands wet to 22,906 ft and observe 5bbl gain in trip tank. Flow check resulted in 2.2bbl gain per hour.
• Shut in well, recording pressures: SICP 80psi / SIDPP 63psi / Kill 106psi.
• Spot 18.5ppg riser cap with an ESD at TD of 16.1ppg. POOH to pick up, run TA packer and temporary abandon well for upcoming hurricane. Move rig to safe location.

Circulate out kick:

• Back on location: Run BOP and latch on wellhead. Displace riser to SBM and spot 18.5ppg riser cap, recover TA packer, open well and confirm well static.
• Retrieve TA packer, run back to bottom and circulate out kick using Driller's method. Circulate up the choke and kill lines, keeping constant wellhead / BOP gauge pressures. Observed low MW out (15.4/15.5ppg), also highly contaminated mud with mud weight as low as 14.5ppg. No barite sag indication found at bottom.

What Went Wrong?:

• Swab kick.
• Low mud weight/well monitoring.
• Fluid treatments may have caused light spots in the active system.
• Correlation between surface mud weights, when using a manual scale and bottom hole ESDs were not continuously shared with mud engineers and pit hands.
• Post kick investigation showed inconsistent surface MWin values, varying from 15.6ppg to 15.4ppg.
• Tight drilling mud window: MDT measurements taken at a later stage revealed a close to balance MW if not slightly underbalanced.
• Tripping procedure not properly implemented: Post-mortem analysis done with contractor highlighted consistency during pumping out and wet tripping out operations. However, it shows that early gain (1 to 2bbl) were taken during flow checks and were not spotted by the rig crew.

Corrective Actions and Recommendations:

Fluid system maintenance:

• Oil / water ratio adjustments should be closely monitored and should be minimized as much as feasible when dealing with active treatments whilst drilling.
• Reinforced mud weight measurements controls to be in place in critical intervals.
• Rig mud engineers and pit hands to be periodically informed of ESD and MWin / MWout readings trends against requirements.

Rig Tripping Procedure:

• Reinforce well displacement sheet regular checks by driller, mudlogging data analysts and drilling supervisors.

Well Monitoring:

• Add MWin / MWout data in the list of mudlogging data to be displayed and monitored by the mudlogging service, setting alarms accordingly to rapidly take corrective actions (±0.2ppg).
• PWD alarms to be implemented indicating reduction / gain in hydrostatic pressure.

safety alert number: 365
IOGP Well Control Incident Lesson Sharing http://safetyzone.iogp.org/

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