SAFOP wellhead platform central North Sea

Introduction

MAR Consulting facilitated a Safety and Operability (SAFOP) workshop of the electrical equipment in an offshore wellhead platform for an ultra-HPHT (high pressure high temperature) gas condensate field located in the Central North Sea. The online workshop was attended by discipline experts from engineering contractors and subcontractors as well as the asset operator.

The objectives of this SAFOP were to:

  • Assess and minimize potential hazards to persons around or in the electrical installations;
  • Provide a critical review of the electrical system design and equipment, assess any limitations and their effects on operability, safety and security of the system;
  • Analyse key tasks of operators.

SAFOP methodology

MAR Consulting performed the following three (3) studies as part of the SAFOP:

  1. SAFAN (safety analysis): an area review to ensure electrical equipment will be properly installed and can be operated and maintained safely. Hazards were risk ranked and causes/ consequences assigned to outside personnel (marked as O), non-electrical (NE) and/ or electrical (E) company staff and contractor;
  2. SYSOP (system operability): systematic technical review with focus on integrity, operability, and maintainability of the electrical systems; and
  3. OPTAN (operator task analysis): analysis of key tasks for operators.

Wellhead platform description

The wellhead platform (WHP) is designed as a not permanently attended installation. The WHP will be remotely monitored; remote control from a host and surveillance facilities will also be installed. All power, hydraulic and chemical services are provided on the WHP. The WHP power system is designed as an independent power system. However, maintenance campaigns require the presence of service personnel for 2-3 weeks at a time, when the platform is characterized and designed as a manned unit.

The key electrical parameters are:

  • Main power: 400V/230V AC, three phase + neutral, 50 Hz, TN-S system earthing;
  • Utility power (for lighting, heat tracing and small power etc.): 400/230V AC, three phase + neutral, 50 Hz, TN-S system earthing;
  • Emergency/UPS (for control and instrumentation supplies etc.): 230V AC, single phase + Neutral, 50 Hz, TN-S system earthing.

Estimated consumed loads for the main four electrical operational scenarios (manned, unmanned, cold start-up unmanned, cold start-up manned) were detailed in the electrical load schedule.

The major electrical equipment will be installed in the Living Quarter (LQ) equipment rooms with a controlled atmosphere. Only minor equipment such as junction boxes and end consumers will be installed outside. The UPS system (emergency source of power) will be installed in a separate emergency equipment room to ensure function in the event of fire or other casualty in the main power system. Batteries grouped in racks, will be installed in a dedicated battery room. The dedicated battery room extract fans will ensure ventilation according to IEC 62485-2.

Scope

The SAFOP of the wellhead platform covered:

  • 400V generators (A, B and C) and respective breakers;
  • Bay / circuit breaker for load bank / hook-up tie-in;
  • Main 400V switchboards (A and B);
  • Breakers, MCCs and sub-distribution panels for consumers;
  • Breakers, utility switchboards (A and B) and 400/110V transformers;
  • Batteries and UPS (A and B).

Since the system operates mostly at the same voltage rating and is located in the same area, it was not deemed necessary to breakdown in different nodes/ sub-systems as typical done. The operational modes considered were normal operation, cold start-up and emergency modes of operation, both manned and unmanned. Installation, commissioning and first energisation were excluded from this SAFOP workshop. They should be handled at later project stages (e.g., during constructability/design reviews, installation and commissioning planning).

Conclusions

Based on the attendance, presented material and ensued discussions, it was considered that the SAFOP was successful in reviewing the new facilities, equipment and systems to be installed. The team concluded that, at the detailed design stage of the project, the design is fit for purpose, robust and safe to maintain and operate, when the recommendations from the SAFOP are followed-up appropriately.

MAR Consulting is highly experienced facilitating and recording SAFOPs, E-HAZOPs and similar assessments of electrical equipment, such as https://www.marconsulting.no/2020/09/18/ehazop-wind-power-onshore/, https://www.marconsulting.no/2020/06/26/electrical-safop-e-hazop-lng-project/, https://www.marconsulting.no/2020/05/15/ehazop-offshore-wind-power-transmission-platform/, https://www.marconsulting.no/2018/03/09/ehazop-power-plant-concept/, and https://www.marconsulting.no/2017/07/26/electrical-safop-ehazop-of-us-elng-plant/ . Please reach out if you need support with SAFOP, E-HAZOP or other electrical risk assessments.

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