A4: Risk Mitigation Must be Evaluated
Person responsible:
Morten Laget
Report No.

WE/MoC-6-2022
Approved

Approved
Location/Facility

Internal
No notification
Date Originated

2022/01/08
4 years ago
Deadline Passed

2022/01/08
4 years ago
Closed Date

2022/01/08
Closed 4 years ago [frm-days-diff start='08/01/2022' finish='08/01/2022']

Minor
in Internal

9 5/8" Seal assembly run without lock-ring
9 5/8" casing hanger normally run with seal assembly and lock ring. Decided to remove the lock ring prior to RIH. Reason to remove the lock ring: The lock ring is considered to be a "weak point" in the system. The lock-ring is one of the components of the seal assembly, and it's installed into its profile with a "lock ring retainer" secured by 2 grooved pins and 2 cap screws. From past experience, it is possible that while RIH the lock ring retainer can "snap", and the lock ring can be lost in hole. The adverse weather conditions forecasted at Hemispheres location in the coming days will increase the risk in both loosing the lock-ring and the time spent to eventually fish-it. Risk Assessment: - Sealing capability and integrity of the seal assembly is not impaired by the absence of the lock-ring. - The casing hanger can be correctly landed in the HPH. The weight of the casing string is acting on the landing shoulder. - The lock-ring can easily be removed "on-deck" prior running the CHASART without removing the seal assembly (i.e. no need for a separate trip to run the seal assy). - NO DST performed on Hemispheres. Consequently, significant less temperature development at the wellhead to be expected. - 8 ½” section has low flow rate and the static temperature is low in this location. - The TOC planned in 9 5/8” will never create a trapped annulus between casings.
Risk Mitigation must be evaluated

  • Risk Assessment

    A4
    Risk Not Acceptable
    Risk Mitigation
    Must be Evaluated
    Acceptable Risk

    A

    Term
    Very Unlikely to occur
    Industry Terms
    Never heard of in industry
    Frequency of Occurence
    Once in 10 years

    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.

    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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