�ݺ�ߣ

Saeed Moosavi
Sr. Process Safety Engineer                South Pars Gas Field Development

Petroleum Industries and Research Engineering Consultant (PIRECO)

► Overview of the Project
The South Pars Facilities are developed to produce gas and condensate from the South
Pars Field, located offshore, around 100‐km South West of Assaluyeh, Persian Gulf, Iran.
National Iranian Oil Company (NIOC) is going to develop South Pars Phase 17&18 of the
Field, which will allow a gas production of 1000 MMSCFD per phase.
Each phase will have two unmanned Wellhead Platforms (WHPs) equipped with
required Production Facilities. The processed gas and condensate in SPD25 and SPD26
(Satellite Platforms) will be directed to SPD24 and SPD23 (Main Platforms) respectively
via Infield Pipelines 18" and 20" which collectively will be transferred to Onshore
Facilities with two 32" Subsea Pipelines to transfer the Offshore Gas Production from
Wellhead Platforms to the Onshore Gas Treatment Plant in Assaluyeh.

► Onshore Facilities
The Onshore Facilities will treat the processed gas and condensate to produce the
following main products:
— Treated lean gas for the domestic gas network.
— Ethane as petrochemical feed stock.
— Treated C3/C4 LPG.
— Stabilized hydrocarbons condensate for export by marine tankers.

► Offshore Facilities
The offshore development consists of four similar Wellhead Platforms (WHPs) SPD23,
SPD24, SPD25 and SPD26 (15 slots each, 11 producing and 4 futures). SPD23 and SPD26
form Phase 17 and SPD24 and SPD25 form Phase 18 of the field exploitation.
Each wellhead outlet is equipped with a hydraulically actuated Choke Valve to reduce
the pressure of the reservoir fluids from the wellhead flowing pressure at the beginning
of production.
The purpose of the Topside Process Facilities is to separate Free and Condensed Water
from the produced fluids, reducing the water content and hence the corrosiveness of the
exported hydrocarbon stream entering the Sea Line to onshore and hence try to limit the
demand for MEG and Corrosion Inhibitors.

I

Saeed Moosavi


► Safety Concept
The Safety Systems were designed to satisfy the following requirements:
— Achieve the maximum natural ventilation and/or proper mechanical ventilation of
any area in order to minimize possible gas accumulation.
— To identify the classification of electrical equipment to be employed in Hazardous
and Non‐Hazardous Areas. Isolate potential ignition sources by means of Area
Classification and the use of Certified Equipment.
— To detect any escape of hazardous products in a prompt and efficient manner,
using Fire and Gas Detection and Safety Alarm System in order to monitor and
control possible gas accumulation and any potential fire event.
— To provide Fire and Gas Detection and Safety Alarm Systems able to give an
immediate warning of fire and gas event and to start ESD/PSD actions. Activate
specific shutdown actions (e.g. HVAC Shut‐Down, Fire Damper Closure, and Inert
Gas System Activation).
— Minimize release of hazardous products by automatic Emergency Shut‐Down and
Process Shut‐Down.
— To provide an adequate Fire Fighting System to bring under control and/or
extinguishing any moderate fire, so preventing its escalation.
— To provide at least two alternate means of escape from all areas throughout the
WHP.
— To check that the integrity of the primary structures and support equipment are
adequate to meet the statutory requirements, independently of the protection
systems activation.
— For each threat to a hazard identified, there must be at least two Safety Barriers, so
that only the failure of both the barriers could cause a potential incident.
The Safety Engineering activities for the Project included the following Safety Studies:
— Hazard Identification Study (HAZID)
— Hazard and Operability Study (HAZOP)
— Consequence Analysis
— Escape Evacuation & Rescue Analysis (EERA)
— Emergency System Survivability Analysis (ESSA)
— Flare Location Study
— Safety Integrity Level (SIL) Determination Study
— Safety Integrity Level (SIL) Verification Study
— Noise Study

II

Saeed Moosavi


► Platform Orientation
The platform orientation was selected as the best compromise between the following
criteria:
— Prevailing wind direction through the year;
— Supply Boat approach;
— Jack‐up approach;
— Helicopter approach;
— Emergency use of Survival Raft/Life Boat.

► Plant Layout
The Plant layout was designed according to the following safety criteria:
— To separate process areas (composed by equipment containing flammable and
toxic gas) from utility areas (composed by Utility Service, Control and Safety
Equipment) by means of Firewall in order to protect personnel and safety
equipment from fire.
— To minimize the possibility of accumulation of flammable or toxic gases by
maintaining ventilation without any danger to personnel.
— To minimize the possibility of accumulation of liquid hydrocarbons by the
provision of an adequate Drain System throughout the WHP.
— To ensure at least one of the Escape or Evacuation Routes is always available.
— To provide an easy evacuation by Boat or Helicopter for both Emergency
Evacuation and General Platform Emergency.
— To ensure safe approach, landing and take‐off of the Helicopter during normal
operation.

III

Saeed Moosavi


  ► Escape Routes
Design of Escape Routes will provide easy and safe access ways (Walkways, Corridors,
Ramps and Stairways) to direct personnel from any region of the platform to the
following areas:
— Muster Point;
— Boat Landing;
— Helideck.

Each deck is provided with at least two Escape Routes (Primary and/or Secondary).
Primary Escape Routes are situated along the outboard edge of the platform making it
easy to reach the Muster Point.
These Escape Paths access to stairways located on platform extremities interconnecting
all deck levels. Thus it is possible to escape from any areas of the platform to the Muster
Point by two alternative routes.
Primary Escape Routes will be 1200 mm wide and 2500 mm high with the exception of
Drain Deck for which Escape Route height will be 2100 mm and free of obstructions in
order to assure a quick departure.
Secondary Escape Routes will have an unobstructed width and height of 800 mm and
2200 mm respectively.

► Life Saving Appliances
In case of platform emergency, all personnel would be advised by PA/GA
announcements (following a platform alarm) to return to their Muster Point, where
numbers and names of personnel would be checked.
The installation will be provided with:
— Life Boat;
— Life Rafts;
— Life Buoys;
— Life Jackets.

Personnel Safety Equipment will also be provided on the WHP.

IV

Saeed Moosavi


► Process Safety Philosophy
All process and production equipment and systems were designed such that under
normal operating conditions the safety of personnel, equipment and the natural
environment would not be jeopardised.
All emergency control and accident prevention equipment were designed to limit, as far
as practical any losses or damage to personnel, equipment and the environment.

► Shut‐Down Philosophy
The Shut‐Down Systems will be installed to detect any abnormal situations on the
platform and to bring the installation back to lower energy level in a safe controlled
manner.
Five classes of Shut‐Down were envisaged, in ascending level of emergency:
— Local Shut‐Down limited to equipment or package (LSD)
— Process Shut‐Down (PSD)
— Emergency Shut‐Down for gas (toxic and/or flammable) presence resulting in
isolation and DEPRESSURIZATION (YELLOW ESD)
— Emergency Shut‐Down for fire presence resulting in isolation and DEPRESSURIZATION
(RED ESD)
— Abandonment Shut‐Down (ASD) – total power isolation including UPS except
NAVAIDs, Escape Route lighting and Helideck perimeter lighting.
— Except for LSD level, all Shut‐Down levels will automatically cause all lower levels
and the highest level of alarm will take priority. LSD level will be independent from
the higher hierarchical Shut‐Down Systems.

► Relief and Blow‐Down Systems
The Relief and Depressurising Valves to be installed on WHP topside will function as a
Safe Relief and disposal device for vapour, gas and liquids to the Blow‐Down/Flare
Systems. Pressure Relieving devices will be installed to ensure that the Process System
or any of its components are not subjected to pressures that exceed the equipment
design pressure. Blow‐Down or Depressurising Valves will be provided in order to
achieve a rapid reduction of inventories in equipment and systems.

V

Saeed Moosavi


► Flare‐Vent System
The Flare System includes:
— LP (Low Pressure) Flare System;
— HP (High Pressure) Flare System.

During normal operating condition the flare will burn continuously, with H2S rich gas
from the Water Degassing Drum.
In an emergency situation the Flare System will be capable of handling the full flow
released from the PSVs installed on the well flow lines. It will be capable of burning gas
from an emergency depressurisation of process equipment should a platform ESD occur.
The waste gas and liquid collected in the system headers are piped to the Flare K.O.
Drum located on wellhead platform. The gas coming out from the K.O. Drum will be
piped to the HP Flare Stack Tip.

► Field Control System
The instrumentation system was designed to guarantee the continuity of the production
in a safe manner, continuous remote monitoring, perform adjustments, modify specified
control parameters and to anticipate hazardous situations or interventions by local
protection systems.
The control system will comprise a redundant microprocessor unit to perform control
functions.
For safety, automatic control of the SDVs is autonomous through the logic of the
platform ESD system.

VI

Saeed Moosavi


► Fire and Gas Detection System
The WHP will be equipped with a Fire and Gas Detection and Protection System, which
covers the entire facility (wellhead, process, utilities areas and survival shelter).
The Flammable and H2S Gas Detectors will be employed and located in those parts of
installation where a gas accumulation is possible in case of hydrocarbon leak.
Flammable Gas Detectors will be mainly IR Open‐Path Type. Where clear line of sight
was not available; IR Point Type Detectors were used.
The produced gas on the platform contains a high concentration of H2S gas. Hydrogen
Sulphide Fixed Gas Detectors of Electrochemical Cell Type will be installed with
particular care in order to obtain the earliest possible detection to protect people during
normal operation, drilling and maintenance phases.
Hydrogen Gas Detector will be located in Battery Room if hydrogen accumulation is
expected.
The followings Fire Detector types have been employed:
— Fusible Plugs
— Flame Detectors
— Heat Detectors
— Smoke Detectors
— Manual Alarm Call Points

► Telecommunication Systems
The telecommunications links will be provided by a Fibre Optic System.
The telecommunication equipment will be able to perform in a safe and reliable mode
the following tasks:
— Mandatory and operational communications within platform and manned centers;
— Transmission of the main process and safety data to the remote control systems.

VII

Saeed Moosavi


► Public Address and General Alarm System
An Audible Alarm System will be available on the WHP, which will be audible at all decks
with a tone at 450 Hz.
A number of Loudspeakers will be placed in the plant. The Loudspeakers will permit
audible alarm as well as the voice communication to the Loudspeakers System. These
Loudspeakers will reproduce four different audible alarms plus voice and will be located
on all levels of the WHP.
Visual Alarm will be provided on Helideck (Beacons) to alert about the platform alarm
status. Flashing Beacons will be also provided on all decks of the WHP when the ambient
noise exceeds the 85 dBA.

► Electrical Systems
Electrical Systems were designed according to IEC Codes. The Wellhead Platforms
consist of two load categories:
— Continuous Loads: identified as the consumers necessary for production operation,
as well as the essential and safety loads.
— Maintenance Loads: identified as the consumers necessary for maintenance
operation and living accommodation.

The Electrical System of the platforms was designed to cover all load categories and
include
— Main Power Generation to feed both Continuous and Maintenance Loads.
— Emergency Power Generation.
— Safety System, with dedicated Battery System, for safety users.
— Distribution System, with separated sections for Continuous and Maintenance
Loads.

Hazardous Area Classification were developed in accordance with IP Code, Part 15 3rd
Edition.
The Navigation Aids (NAVAID) System has a proper Battery System at 24V ensuring 96
hours operation after Abandonment Shut‐Down.

VIII

Saeed Moosavi


► Passive Fire Protection
Firewalls will be provided in order to protect utility, control and safety equipment from
the process area. For this purpose J‐60 Class (suitable to resist Jet Fire for 60 minutes)
divisions will be specified for Firewalls located at the following levels:
— Cellar Deck
— Lower Deck
— Upper Deck
The Fire Partitions for enclosures were assessed based on potential fire scenarios and
SOLAS guidelines. Fire Ratings of the walls and enclosures were recommended as per
the Analysis of Fire Hazards.

► Blast Protection
The facilities design provides natural ventilation to areas where flammable gases may
build‐up thus minimising explosion potential. This is achieved by maximising grated
decks and open platform construction. These two approaches combine to provide
overall explosion mitigation for the project facilities.
Based on analysis, explosion risk can be considered a low frequency event.

► Active Fire Fighting Systems
The following Fire Fighting Systems will be provided on the WHP:
— Fire Water System comprising Firewater Ring Main, Deluge Systems, Hydrants and
Hose Reels;
— Inert Gas extinguishing Systems; (stand alone system in Generator And Technical
Rooms);
— Portable and Wheeled Fire Extinguishers (CO2, Dry chemical Powder, AFFF and
AR‐AFFF);
— Helideck Fire Fighting System (AFFF, Pre‐mixed System) and Dry Chemical Powder
System.



IX

�ݺ�ߣ

South Pars Gas Field Development ~ Phases 17/18 Project - Offshore Platforms

More Related Content

South Pars Gas Field Development ~ Phases 17/18 Project - Offshore Platforms