Influx observed while drilling an offshore deepwater HPHT well in the 12 ¼” hole section using MPD
IOGP Well Control Incident Lesson Sharing #24-4
While drilling offshore with a Drillship in the 12 ¼” hole section at 4174m MDRT with 1.63 sg SBM, observed a 7 bbl gain. Drilling operations were stopped, however circulation was continued to maintain BHP with MPD. The MPD mode was switched to ‘Flow Control’ Mode. Observed SBP increasing from 90 to 500 psi and with that, an additional influx. The total Influx volume exceeded the 10 bbl limit that could be handled via MPD (11 bbl gain detected). The well was then Shut-in on the Upper Annular. Both the SICP / SIDP were recorded at 350 psi. Perform well kill with 1.71 sg kill weight mud while keeping the BHP constant using MPD in “P@D” mode. This lesson sharing shows how important is to determine the best estimate of pore pressure during well planning and also, how to use the proper MPD modes while drilling and when taking a kick.
The 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 mail to share it further within their organization.
What happened?:
Drilling 12 ¼” section @4174m MDRT with 1.63 sg SBM, using MPD (‘’Surface Back Pressure’’ mode, 90 psi), noticed active pit level increasing - 7 bbl gain.
Stop drilling, kept circulation to maintain BHP with MPD. Switch MPD to “Flow Control” Mode (maintaining a flow in vs. flow out constant).
Observed SBP increasing from 90 to 500 psi and additional influx. Influx volume exceeding defined 10bbl limit that could be handled via MPD (11 bbl gain detected).
Shut-in the well on Upper Annular.
Circulate influx out of riser with MPD and booster (Max gas: 2.2%), while observing with Up Annular closed.
Circulate influx out of the well via BOP (Up Annular) Record SICP/SIDP 350 psi – Estimated PP 1.70+ EMW – MAASP: 1460 psi.
Equalize using MPD and open UAP. Displaced 1.71 sg kill mud into the string and the well keeping BHP constant: use MPD in “P@D” mode.
What Went Wrong?:
- Pore pressure > CC prognosis.
- Incorrect MPD mode selected: ‘’flow control’’ instead of ‘’SPP mode’’ (maintain de pumping pressure constant) / Procedures implementation.
- Confusion in the decision making process during the influx management.
- First MPD experience on the rig.
Corrective Actions and Recommendations:
- Review MPD mode selection during well control situation.
- Recovery plan: hand over between conventional WC & MPD operations
safety alert number: 366
IOGP Well Control Incident Lesson Sharing http://safetyzone.iogp.org/
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