Monday Accident & Lessons Learned: IOGP SAFETY ALERT – KICK TAKEN WHILE DRILLING 8 1/2” RESERVOIR SECTION IN DEEPWATER EXPLORATION WELL
KICK TAKEN WHILE DRILLING 8 1/2” RESERVOIR SECTION IN DEEPWATER EXPLORATION WELL
The event took place on a Drillship while drilling the 8-1/2” section of an exploration well.
Well architecture consists of 36” CP at 939 m, 20” casing at 1274 m, 14” casing at 1666 m and 9-5/8” casing at 2702m.
Drill 8-1/2” section at 2860mMD/RT.
Made connection, resumed drilling.Observed 4.5% connection gas.
Observed gas increase to 27%.
Picked up string off bottom & circulated out gas (reciprocating string).
Observed 0.9m3 gain in active pit while circulating gas out of hole.
Shut in well & monitored for pressure evolution.
Observed increase in SIDPP, SICP & WHP.Continued to monitor pressure evolution.
Pressure stabilized at: SIDPP 480 psi & SICP 320 psi.
Spaced out and hung off string on Middle Pipe Rams.
ECD increase. SPP increase. Possible change in formation.
Sign of under-compaction on the resistivity log. Well Control: (Driller’s Method).
Flush each of Lower, Middle and Upper Choke fail safes. 131 psi (9 bar) back pressure on Choke.
Circulate down string and flush KL. 203 psi (14 bar) back pressure on well.
Open MPR and reduce UAP pressure. Close CMC.
Attempt to strip up and down, negative – string differentially stuck. 40 MT over pull and 36 MT set down weight.
Displace riser through boost line to 1.42sg kill mud. 17.7% max. gas observed.
Displace choke line volume to 1.42sg kill mud
Close MPR, displace KL with 4.5m3 base oil.Open UAP allowing 1.42sg kill mud in riser to u-tube up KL to sweep BOP stack.
Observe 2.5m3 drop in trip tank volume. Close UAP and open MPR.
Displace kill line volume to 1.42sg kill mud through gas relief line.
Perform flow check: well static.
Work drill string free with different parameters.
Circulate down string: FR 380 – 1000 lpm, 624 – 1305 psi (43 – 90 bar). Apply 14KN.m, 36 MT below SOW and 45 MT overpull.
Increase torque to max of 22.5KN.m. Observe drill string free.
Displace Choke, Kill & Boost lines to 1.47sg NABM.
Displace well to 1.47sg NABM.
WHAT WENT WRONG?
- Failure to recognize the potential/risk: Despite warning signs and pre-job meetings alerting on the nature of the activity, crew was not vigilant and sensitive to the nature of the activity (exploration drilling).
- Underbalanced Well Warning signs missed: Mud loggers and Geologist not following properly the gas and resistivity trends and not communicating adequately on gas and under-compaction trends seen.
- Procedure not followed: Established procedure called for reducing BGG to <1% at all times before drilling resumes. Drilling resumed with high BGG.
- Poor supervision : With warning signs of kick, team failed to recognize the appropriate action to take. And signs of entering high pressure zone unrecognized.
CORRECTIVE ACTIONS & RECOMMENDATIONS
- No mud transfer should be done when drilling an exploration well without proper and laid out procedure. Follow mud transfer protocol.
- After each connection and flow check, the corresponding bottoms-up circulation must be monitored.
- Drilling of exploration wells should not have continued with 10% background gas.
- Fingerprint of flow back in active system during pumps shut off should be monitored and analyzed.
- The well site geologist should do more to alert the company man of such observations as decrease of resistivity log.
- As a follow up, drillers should charge the mud loggers to employ more monitoring tools like ROP break, d-exponent….etc, that give direct indication of a kick.
- Consideration should be given to having a manual joystick on the cyberchair for choke control. The buttons on the digital display is too small to operate.
- There was no kill sheet available by the time the kick was taken; not with the drilling contractor or company representatives. Going forward, a kick sheet should be prepared for every phase where a reservoir is to be encountered, compulsory for exploration wells. Kick sheet must be reviewed as operation progresses.
- Communication with base is mandatory in this type of event.
Aafety Alert nNumber: 263
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