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Risk Assessment and Blowout Intervention for Platform Survivability - Part 3

Published on 16 Jul 2016 by Tadd Pham


This Part 3 is a continuation of Part 2 - Sample “What-if” Assessment Pre-prepared Questions.

Sample Recommendations to “What-if” Assessment

Loss of buoyancy

  • Ensure a flooding risk assessment study for blowout scenarios is conducted for the platform
  • Investigate the use of remote level and motion monitoring and/or tendon tension monitoring in the pontoon to provide early flood and tilt warning for the platform
  • Ensure an emergency response plan is in place to deal with any effects to the FPSO from the platform sinking/instability
  • Ensure the decision tree is properly defined as part of the emergency response plan
  • and appropriate preparedness is in place in event of platform instability
  • Develop an appropriate emergency response plan and communication protocol to
  • the field support in event of platform instability
  • Perform a study to assess the need for disconnecting FPSO in the event site conditions become hazardous (e.g. platform instability, subsea blowout leading to extreme metocean conditions, fire and explosion risks from surface blowout).
  • Ensure that platform sinking on the FPSO mooring lines is considered as part of Marine Hazard Study

Response protocol

  • Conduct a study to determine suitable response package equipment type and availability for the event of a well blowout
  • Ensure that response protocol deployment equipment is available for well blowout scenarios
  • Ensure capping stack is available and suitable for the platform well configuration to evaluate proper capping stack requirement
  • Evaluate local logistics for well blowout response protocol deployment
  • Ensure that contracts are in place to aid mobilization of the necessary equipment and personnel for rapid response in the event of a well blowout
  • Develop a well control plan with memorandum of agreement for emergency response for well blowout scenarios
  • Ensure that a provision is made that a back-up ROV support vessel is available when normal ROV is unavailable
  • Ensure plans for relief well drilling are in place for commencement as soon as site conditions become acceptable
  • Ensure required relief well equipment and supplies are readily available
  • Ensure competency training is established and performed for personnel involved in responding to a well blowout and recovery from such an event

Rig sharing

  • Consider the need for agreements to be in place with other drilling operations for shared use of well blowout response equipment
  • Evaluate the possibility of rig sharing agreements for relief well drilling

Well layout

  • Evaluate well casing design for containment capacity. If necessary, evaluate the cap and flow logistics requirements
  • Utilize Bureau of Safety and Environmental Enforcement (BSEE) well containment screening tools to ensure casing design can contain system pressures
  • Ensure sufficient and correct information and data regarding the platform well configuration/layout, etc. is included in the emergency response plan
  • Investigate the use of a Subsea Isolation Device (SID) for the drilling riser. Note: on SID by Rick Thety of 2H Offshore - SID is large and likely will not fit through the well bay tensioners. Hence, the SID will need to be pre-installed and 'jumped' from well to well during drilling. Jumping between wells will likely cause interference with existing production risers and may lead to a larger seafloor arrangement. Consideration on how to run and retrieve for maintenance and inspection will also be necessary. The guide-wire system may need to be increased to accommodate the loads and large size of the SID. The large mass at the base of the drilling riser will need to be considered in the conductor analysis (this was shown to be critical in past analysis with a MODU)
  • Investigate options to maximize riser accessibility as part of layout design
  • Ensure adequate well spacing is incorporated in the design to allow for capping stack activity
  • Ensure lessons learned from others are incorporated into the facility design, procedures and emergency response plans

Platform offset

  • Evaluate the possibility of cutting the platform tendons to achieve required offset
  • Evaluate the necessity for lateral intervention using the Heave Compensated
  • Landing System (HCLS)

Unstable Metocean

  • Wait for suitable metocean conditions to resume activity in event of unsafe site conditions
  • Evaluate the applicability of dispersants for well blowout scenarios

Additional recommendations for the “What-if” Assessment includes:

  • Fire and explosion risk assessment for the platform for blowout scenarios
  • Temporary refuge study in the Emergency Evacuation Risk Assessment (EERA) for platform sinking scenarios
  • Flooding Risk Assessment Study for the platform for blowout scenarios
  • Drilling sequencing study for well blowout recovery efforts
  • Explosive Safety Self Assessment (ESSA) for the platform for blowout scenarios
  • Suitable well blowout response package equipment study
  • Well casing design for containment capacity and cap and flow logistics requirements
  • FPSO dis-association study in event of blowout scenarios
  • Applicability for the use of dispersants during well blowout events
  • Rig sharing agreements for relief well drilling
  • Possibility of cutting the platform tendons to achieve offset for accessibility to well
  • Site metocean conditions for working windows that allow equipment installation and performing work under the platform
  • Lateral intervention using the HCLS
  • The use of a SID for the drilling riser
  • Possibility of flowing back to the FPSO in the event of inability to shut-in or kill the well
  • Options to maximize riser accessibility as part of the layout design
  • Vessel/platform SIMOPS coordination
  • Options to prevent the platform from landing on the wells in the event of it sinking
  • Soil conditions for the use of suction piles
  • Marine Hazard Study including the event of platform sinking on FPSO mooring lines
  • Worst case discharge study for the well

Developing Plans

  • Recommendations from the “What-if” Assessment include developing various plans such as:
  • Contingency plans for well shut-in including capping stack option in event of well blowout
  • An appropriate emergency response plan for well blowout scenarios including fire fighting from support vessels, response procedures and communication to the field support
  • A well control plan with Memorandum of Agreement for emergency response for well blowout scenarios
  • An emergency response plan with the local authorities
  • An emergency response plan to deal with any effects to the FPSO from the platform sinking/instability
  • A contingency plan for well blowout and platform instability scenarios
  • A communication plan for emergency situations
  • Plans for relief well drilling to commence as soon as site conditions become acceptable.
  • An appropriate emergency response plan and communication protocol to the field support in event of platform instability
  • A contingency plan for a second and potentially a third relief well

Checklist

Recommendations from the “What-if” Assessment include considering the need for developing a checklist of items during the site assessment survey to ensure that the correct location and information can be transferred.



Tags: intervention blowout assessment

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