5. Operation and maintenance philosophies

06.04.2016
This section describes the operation and maintenance philosophies for unmanned platforms.

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5.1 General

The Operation and Maintenance (O&M) philosophy shall stipulate the goals for the operation and maintenance of the UWHP.

The philosophy shall be supported by strategies for the operation and maintenance, i.e. which tasks shall be carried out to reach which goal, and also the strategies behind the tasks must be outlined.

More detailed information about the operation and maintenance philosophies for unmanned platforms can be found in the sub-report, ref. /9/.

 

5.2 Design aspects

For the UWHPs, the main issue is that O&M activities shall be designed out of the equation, wherever possible in order to minimise the manning frequency and the hours spent on board. Equipment and systems shall be kept at a minimum, and equipment requiring periodic inspection or re-certification shall to the extent possible be avoided.

Focus should be on using noble materials to considerably reduce the need for Risk-Based Inspections (RBI), furthermore focus shall be on specification and procurement of equipment with proven reliability and high Mean Time Between Failure (MTBF) (and as far as possible a short Mean Time To Repair (MTTR)).

Equipment requiring periodic inspections (fire extinguishers, inflatable life rafts, etc.) can be brought to the installation, when needed.

Generally and not least, for the installations with very rare visits and very short maintenance campaigns, equipment shall to the extent possible be of a modular design. This is to support the philosophy that no repairs take place on the platform, but instead a complete module (e.g. a complete actuator) is simply replaced.

 

5.3 Operation and maintenance philosophy

The philosophy must, depending on the type of UWHP, define:

  • The design lifetime of the platform
  • How the platform shall be operated
  • Requirements for pigging and the pigging frequency
  • Logistics of daily consumables such as chemicals, power, hydraulics, etc.
  • Production and injection figures including goals as regards regularity and uptime
  • How often may the platform be visited / maximum manning hours per year
  • How are well service operations planned to be carried out
  • Whether the platform is to be in operation during visits, or whether it is assumed to be shut down (or maybe only shut down in case intrusive maintenance is to be performed on hydrocarbon-containing systems)
  • How should the platform be manned (helicopter, FRB, W2W bridge, etc.)
  • Is the manning by a crew from the host or by a specialist team from shore

 

5.4 Operation and maintenance strategy

The strategies shall address:

  • The level of automation (needs for remote monitoring and control) including needs for condition monitoring and preventive maintenance
  • Necessary operations (on a task level), which can be performed remotely, and which require manning (including “remote resets”)
  • Which integrity tests need to be performed - and how often - on well-related valves and can such tests be carried out remotely
  • Which well service operations need manning
  • Manning strategy including team background, skills and competencies
  • Should manning be a crew from the host or a specialist team mobilised from shore?
  • Outline of the “Permit-to-Work” (PTW) system (controlled from host)
  • Dedicated strategies for %-scheduled maintenance, application of RCM and RBI, planned preventive maintenance, Safety Critical Element (SCE) checks against performance standards, mandatory tests/inspections/re-certifications, fabric maintenance including preservations, etc.
  • Strategy for spares, tools, workshops and consumables being used during manning – for example container solutions on the OSR or W2W vessel.
  • Campaign strategy.

The O&M strategy will depend very much on the mechanical handling strategy being developed for the platform.

Campaigns and the majority of the required manned operations for the operation and maintenance of the UWHP should take place during the summer time.

 

5.5 Philosophy and strategy

Type 0 platform The Type 0 UWHP was designed with an operation and maintenance philosophy very similar to manned installations. A large amount of unscheduled maintenance is accepted and executed on this type of platform. Typically, there is a 40% to 60% distribution between scheduled and unscheduled maintenance.

Since these installations are equipped with a helideck, the operation and maintenance activities are based on the easy availability of helicopters. The typical manning frequency is in the range from once a week to almost daily, as continuous unmanned operation is actually not allowed for some of the traditional designs and equipment.

The consequence is that these UWHPs are visited very often, and the duration of the visits may be disproportionate to the task to be performed.

This type of platform has a pedestal crane, which is used in the mechanical handling on board, and which also allows chemicals, consumables, spares, tools etc. to be taken on board from the supply boat. Furthermore, some platforms have a crane sized to take coiled tubing equipment on board.

All operation and maintenance work is to the extent possible performed, while the platform is operating.

 

5.6 Philosophy and strategy

Type 1 platform The operation and maintenance activities are reduced as much as possible by keeping the amount of equipment at a minimum, by avoiding equipment needing periodic inspections or re-certifications and by selecting reliable equipment with proven records.

The Type 1 platform will normally be manned by helicopter, and therefore some breakdowns can be accepted due to the easy access. In addition, certain operations need manning, such as bunkering of fresh water or diesel and replacement of chemical tanks. The typical manning frequency is in the range of once every 2-4 weeks.

Elements of Reliability Centred Maintenance (RCM) and Risk-Based Inspection (RBI) are typically introduced in the maintenance strategy. Also, elements of condition monitoring and preventive maintenance are part of the strategy. The typical number of man-hours on the facility is in the range of 5,000-6,000 hours per year.

This type of platform has a pedestal crane, which is utilised in the mechanical handling on board, and which also allows chemicals, consumables, spares, tools etc. to be taken on board from the supply boat. A few platforms have a crane sized to take coiled tubing equipment on board, however, it is more likely that coiled tubing operations are only performed, if a drilling rig or an OSR is present at the platform.

In order to optimise the use of hours on board, all maintenance work is to the extent possible planned to be performed, when the platform is manned due to operational requirements and vice versa.

 

5.7 Philosophy and strategy

Type 2 platform The operation and maintenance activities are reduced as much as possible by keeping the amount of equipment at a minimum, by avoiding equipment needing periodic inspections or re-certifications and by selecting reliable equipment with proven records.

Planned major maintenance work is scheduled to take place during the summer period to ease the manning using an FRB or other access methods from the sea. The typical manning frequency is in the range of once every 3-5 weeks.

Elements of RCM and RBI are typically introduced in the maintenance strategy. Also elements of condition monitoring and predictive maintenance are part of the strategy. The typical number man-hours on the facility is in the range of 1,500-3,000 hours per year.

This type of platform has a pedestal crane, which is utilised in the mechanical handling on board, and which also allows chemicals, consumables, spares, tools etc. to be taken on board from the supply boat, and some platforms have a crane sized to take wireline equipment on board.

Coiled tubing operations can usually only be performed, if a drilling rig or an OSR is present at the platform.

In order to optimise the use of hours on board, all maintenance work is to the extent possible planned to be performed, when the platform is manned due to operational requirements and vice versa.

 

5.8 Philosophy and strategy Type 3 platform

The operation and maintenance activities are designed for the platform and are reduced to a minimum, and equipment and systems are selected to optimise the production uptime and to extend the maintenance intervals.

Planned major maintenance work is scheduled to take place during the summer period (if possible) to ease the manning using a W2W system or other access methods from the sea. The theoretical manning frequency is in the range of once every 6-24 months.

Elements of RCM and elements of condition monitoring and preventive maintenance are part of the strategy. The use of noble materials minimises the RBI requirements. All maintenance work will be carried out in campaigns once every 6 months or every 2 years - depending on the operator’s philosophy. Typically, the campaign will be executed, when the platform is shut down. The theoretical number of man-hours on the facility is below 500 hours per year.

The Type 3 platform does not have a crane. Lifting operations inside the platform can (maybe) take place within some limitations, if portable lifting equipment is brought on board via a W2W bridge. Otherwise, lifting operations to and from the platform will rely on an external crane (drilling rig, OSR or combined W2W/crane).

Well service operations, such as wireline operations and more heavy operations, can only take place, when an OSR or a drilling rig is present.

 

5.9 Philosophy and strategy Type 4 platform

The operation and maintenance activities for this type of installation are reduced to an absolute minimum and often refer to the API recommendation for testing and inspection.

The systems on these installations are also reduced to a minimum. Some breakdowns are expected and will be handled as the installation is visited. All maintenance work is to the extent possible performed, when the platform is manned due to operational requirements. As these facilities are typically located in shallow water close to shore, where access by FRB is relatively easy, the designs have not necessarily been optimised to reduce the number of visits, the typical visit frequency is relatively high - in the range of twice a week to every second week.

The platform may have a small davit for lifting a valve internally on the platform.

Otherwise, all major operations involving lifting and moving items will require an OSR or a drilling rig to be present.