C3: Risk Mitigation Must be Evaluated
Person responsible:
Not selected
Report No.

WLSY/MoC-4-2020
Approved

Approved
Location/Facility

Schweinsteiger
May Need to be notified
Date Originated

No date set
No date set

Minor
in Schweinsteiger

Revised plan for top hole drilling due to shallow gas
The Schweinsteiger well was planned with 30” conductor shoe at +/- 307 m RKB. A 9 7/8” pilot hole was going to be drilled to planned depth of the surface casing shoe at 632 m RKB to check for shallow gas. The risk of gas was expected to be low ref. site survey. Ran and cemented 30” conductor as per program. RIH with 9 7/8” BHA and drilled to 340 m RKB (33 m below the conductor shoe). At 340 m, the LWD logs showed a drop in GR and spike in the resistivity at drilled depth 331 m. Flow checked well and bubbles were observed by the ROV. Immediately started to pump 1.50 sg kill mud with returns to seabed. Well observed to be killed and stable. Monitored with ROV. Plan will be as follows: Drill 30 m controlled with 9 7/8” pilot hole BHA and 1.25 sg pump & dump and perform new flow check. No new zones identified on logs. Flow check and discuss way further 18:30 28.08.20 with onshore and offshore organization - operator and contractor present. Burst of bubbles observed at wellhead housing during flowcheck. Displace to “new” 1.25 sg mud to see if any air trapped in system. Commence drilling with seawater and pump mud at connections and drill to TD and log formations. This will gather valuable information regarding hole condition and way forward. Only small amount of bubbles observed and able to kill with 1.50 sg MW. Will monitor for GR/Res changes for any new shallow gas sones, if identified, stop and flow check to observe for increasing trend. If yes, kill well.
Risk Mitigation must be evaluated

  • Risk Assessment

    Risk Not Acceptable
    Risk Mitigation
    Must be Evaluated
    C3
    Acceptable Risk

    C

    Term
    Likely to occur
    Industry Terms
    Incident could occur in North Sea Area
    Chance of Occurence
    20% - 50%
    Frequency of Occurence
    Once in 2 years

    3

    • Medium Impact
    • Regular Well Control Incidents
    • Lost Time Incident / Reportable Incident
    • Oil 1m3
      Black 100 litre
      Red 10m3
      Yellow 100m3
      Green 1000m3
    • 3 days lost time - 5 MNOK to 10 MNOK
    • Operator investigated by authorities. No mention of Wellesley.

    Probability and Impact of Event

    PROBABILITY / LIKELIHOOD OF EVENT
    C Term In Industry Terms Percentage Chance of Occurence Frequency of Occurence
    A Very Unlikely to occur Never heard of in industry 5% Once in 10 years
    B Unlikely to occur Has occured in industry 5% - 20% Once in 5 years
    C Likely to occur Incident could occur in North Sea Area 20% - 50% Once in 2 years
    D Very likely to occur Incident could occur during our operations 50% - 80% 2 times per year
    E Almost certain to occur Incident could happen more than once during this operation 80% Once a month
    IMPACT / CONSEQUENCE OF EVENT
    C Term Well Control People Environmental Damage Asset Damage Reputation Damage
    1 Very low impact Negligible First Aid Required Oil 100 litre
    Black 10 litre
    Red 1m3
    Yellow 10m3
    Green 100m3     		1 day lost time
    Less than 1MNOK    		 Information only to authorities. No further discussion.
    2 Low Impact Non Classified Restricted Work Case / Medical Treatment Case Oil 100 litre
    Black 10 litre
    Red 1m3
    Yellow 10m3
    Green 100m3     		1 day lost time
    1 MNOK to 5 MNOK    		 Operator in dialog with authorities. No mention of Wellesley.
    3 Medium Impact Regular Well Control Incidents Lost Time Incident / Reportable Incident Oil 1m3
    Black 100 litre
    Red 10m3
    Yellow 100m3
    Green 1000m3     		3 days lost time
    5 MNOK to 10 MNOK    		 Operator investigated by authorities. No mention of Wellesley.
    4 High Impact Serious Well Control Incidents Likely Permanent Disability Oil 100m3
    Black 1m3
    Red 100m3
    Yellow 1000m3
    Green 10000m3     		14 days lost time
    10 MNOK to 30 MNOK    		 Local media coverage. Wellesley included in coverage or approached by authorities.
    5 Very High Impact Critical Well Control Incidents Single or Multiple Fatalities Oil 1000m3
    Black 10m3
    Red 1000m3
    Yellow 10000m3
    Green 100000m3     		30 days lost time
    More than 30 MNOK    		 National coverage. Wellesley included in coverage.

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