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Subsea Commissioning Philosophy

Published on 26 Feb 2018 by Emma Leoni


This document is to detail pre-commissioning, commissioning, start-up and performance testing requirements for the subsea system.

Drilling and Completion activities related to these requirements are not covered in this document. FPSO activities related to these requirements are not covered in this document.

General

Equipment functionality must support the following pre-commissioning, cold commissioning and commissioning objectives:

  • All activities must be in accordance with project HSE requirements
  • Minimize exposure of personnel to potentially hazardous commissioning activities (e.g. exclusion zones during Nitrogen (N2)/ Helium Leak testing and methanol handling
  • No punch list items on project Final Acceptance (FA)
  • Equipment / systems must be designed with the intent of simplifying pre-commissioning, cold commissioning and commissioning, and facilitating fast, efficient handover. Where required, additional isolation must be included in the design to facilitate these commissioning activities
  • Dewatering methods of production and gas injection flowlines must support N2 purging from FPSO or installation support vessel, pigging (including gel pigs), and/or gas injection back flow with hydrate inhibitor injection

Subsea Mechanical Completion

The functionality of the system must permit the following activities to be performed:

  • Pipeline route survey and verification that the pipeline is installed to procedures and acceptance limits
  • Installation of the subsea system
  • Survey of installed system and confirmation all equipment has been installed to procedures and acceptance limits
  • De-watering and conditioning of:
    • Subsea production system
    • Subsea gas injection system
    • Subsea gas lift system
  • Flooding and system pressure testing of the subsea rigid flowlines, spools and flexible flowlines in accordance with Pre-Commissioning of Submarine Pipelines (DNVGL-RP-F115).
  • System pressure testing of flowlines in accordance with the requirements of Pre-Commissioning of Submarine Pipelines (DNVGL-RP-F115).
  • Flooding and hydrotest fluids must be either discharged subsea, from installation support vessels, or the FPSO.
  • Diverless connection systems needed for commissioning pigging activities and associated pressure caps must allow for installation of temporary pig launchers/receivers.
  • Pressure testing and electrical continuity testing of the umbilical systems.
  • Leak off testing and functional verification of wells, including trees, must be performed via MODU or LWI vessel.
  • Long term preservation of equipment, where required between mechanical completion and start-up. Preservation fluid to be used within trees, structures, rigid spools, flowlines, risers and umbilicals should follow the requirements of the following section.

Subsea Pre-Commissioning and Cold Commissioning

Functionality of the system must permit the following pre-commissioning activities to be performed:

  • Chemicals used for flooding. hydrotesting and preservation of the subsea system must be selected:
    • To eliminate the risk of any type of materials failure
    • To assist with hydrate inhibition during flowline dewatering and start-up (assuming hydrocarbon gas provides a minimum preservation period of 2 years)
  • Chemicals with an Offshore Chemical Notification Scheme (OCNS) ranked Gold or Silver, E or D (non-Chemical Hazard and Risk Management (CHARM)) and with no substitution warnings, are preferred
  • All temporary equipment must be designed and tested in accordance with Pre-Commissioning of Submarine Pipelines (DNVGL-RP-F115)
  • Prepare the subsea system for the introduction of in-service fluid
  • Prior to the introduction of hydrocarbons, verify the subsea system functionality as an integrated system controlled by the FPSO Process Control System (PCS) and Safety Instrumented System (SIS)
  • Subsea power and control system power up and verification against predicted performance to ensure the systems in compliance with the required Engineering Standards
  • Full point to point function testing of subsea valves and instruments, verification of valve timing and interlocks
  • Subsea system process shutdown / emergency shutdown action verified from the PCS / SIS
  • Ensure correct valve positions for ROV operated valves

Subsea Commissioning and Start -Up

Functionality of the system must permit the following Commissioning and Start-up activities to be performed:

  • Displacement of any preservation fluids (flowline dewatering)
  • Pressurization of the subsea system
  • Subsea system shutdown testing
  • Leak testing, equalization and function testing of the surface controlled subsurface safety valve (SCSSV) and subsea tree valves
  • Start-up of the chemical injection system
  • All umbilicals cores (except the spares) purged from FPSO up to all subsea injection point with appropriate fluids
  • Flowline performance testing and Start-up and performance testing of the production, artificial lift and supporting systems

Subsea System Design Requirements

The subsea system must be designed to enable to perform commissioning in accordance with:

Pre-commissioning, commissioning and post-hook-up testing (including system electrical and pressure testing) of the subsea production system must be performed in accordance with Engineering Standard Subsea Production Systems General Requirements (ISO 13628-1 )

Pre-commissioning and commissioning activities for flowlines must be performed in accordance with Pre-Commissioning of Submarine Pipelines (DNVGL-RP-F115)

Pre-commissioning and commissioning activities for flexibles (including risers) must be performed in accordance with the Engineering Standard Subsea Flexible Flowlines and Risers (API 17J, 17B, 17L1 and 17L2)



Tags: subsea pre-commissioning start-up commissioning

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