8/9/2019 OGPWCIAlert14-10

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WELL CONTROL ALERT

The International Association of Oil & Gas Producers (IOGP) Well Control Incident Alert System was established as a means of notifying fellow IOGP members of the lessons learned from well control incidents and near misses. The sharing of these alerts with the IOGP community will help to promote learning and avoid the repetition of similar errors. The result will move the industry to a higher level of well control safety. IOGP is grateful for all contributions and the continued support of the Well Control Incident Database reporting system. All well control incidents and near misses are requested to be reported to the IOGP Well Control Incident Database secretariat ( wp@iogp.org  ). All information received by IOGP is treated with utmost confidentiality and any published data is always anonymous. Further information can be found in the IOGP websitehttp://www.iogp.org .Note: Original alert wording from IOGP Member Company.

The reporting company has authorised unrestricted distribution of this alert.

 Alert #14-10 

Well Control IncidentThe 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 0.9m 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.

Observation:

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 mudClose 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.

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Contributing FactorsFailure 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.

Lessons LearnedNo 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.

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Disclaimer: Neither the IOGP nor any of its members past present or future warrants the accuracy or completeness of this document or will,regardless of its or their negligence, assume liability for any foreseeable or unforeseeable use made thereof, which liability is hereby excluded.Consequently, such use is at the recipient’s own risk on the basis that any use by the recipient constitutes agreement to the terms of thisdisclaimer. The recipient is obliged to inform any subsequent recipient of such terms. This document may provide guidance supplemental tothe requirements of local legislation. Nothing herein, however, is intended to replace, amend, supersede or otherwise depart from suchrequirements. In the event of any conflict or contradiction between the provisions of this document and local legislation, applicable laws shall  prevail.

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