Sales

OVERVIEW
The development of a simple 4 leg jacket with minimum practicable topsides area is the basis of the Camelot CB optimum facilities design. The facility is a ‘not normally manned’ platform located in the Southern North Sea. The platform is designed to export gas, with a minimal condensate content.

The conventional 4 leg jacket, piled through the legs, with minimum topside area and deck levels provides processing, wellhead and metering facilities for a single well operation and a single storey utilities building/emergency shelter and a helideck.

The two main areas of reduced facilities are in the gas/condensate/produced water separation and treatment, the electrical generation and utilities systems. Both measures have been aimed at producing a more cost effective, compact and weight saving topsides facility.

The operating and maintenance philosophy was based on minimizing routine maintenance requirements, endeavouring to combine these on 6 week intervals with refueling/supply boat trips. The current maintenance philosophy, outside of interventions for breakdowns, is currently being reviewed.

CONTENTS

PRODUCTION FACILITIES
Camelot CB produces hydrocarbons from a single well, which is flowed to the production separator where three-phase separation takes place. Gas, condensate and water are separated out by gravity and with the aid of structured and specialized packing within the vessel. Produced water exits the production separator under interface level control and is routed to the free water knock-out spool for final clean-up. The water is degassed in the free water knock-out spool and is routed overboard via the drains caisson with a maximum oil in water content of 40ppm. Gas leaving the production separator is routed via the gas KO drum where any remaining liquids are removed prior to gas metering. The condensate phase exits the production separator under level control and is metered prior to being recombined back into the gas stream. MEG/corrosion inhibitors are injected into the gas/condensate stream prior to export.

Gas flow metering to near fiscal standards is by means of an orifice plate located downstream of the gas KO drum prior to export from the platform.

Gas flow rate signals are pressure and temperature compensated and computed to standard reference conditions before being transmitted.

Condensate and water are metered by coriolis meters in the appropriate lines. These meters are capable of measuring density and will cause alarms to be annunciated should the density fall to a level indicating gas blowby.

Pressure relief, system blowdown and continuous venting from the free water knock-out spool are accommodated by the vent system. Vented gas is released at a safe elevation and distance from the platform by use of a boom structure.

Drains systems are provided; open drains for the disposal of sanitary, waste water and helideck water and a closed drains system for the processing of hydrocarbon liquids and produced water and hazardous waste such as fuel oil spillages from the diesel tank and utility building equipment.

UTILITY SYSTEM
Utilities (sea water, fresh water, diesel) are provided to support all production and maintenance activities during normal production and shutdown conditions.

POWER GENERATION
Three identical generators (54 kW, 415v, 3 phase, 50 Hz) provide the main electrical supply (two main/one emergency). During normal unmanned operation only one generator is required, whilst in manned mode two generators may be required. All three generators are driven by individual closed cycle water cooled diesel engines.

An un-interruptible power system is provided to supply emergency loads for the break period between loss of main power and start-up of the emergency power system. The battery capacity is calculated to provide 3 hours of UPS emergency supply.

PLANT CONTROL
The overall plant will be monitored and controlled from the Central Control Room (CCR) at the onshore terminal via comprehensive telecommunications and ‘supervisory control and data acquisition’ (SCADA) system.

An ESD system is provided in order that production may be stopped and if necessary the equipment de-pressurised should any anomaly occur. An anomaly may be fire and gas detection, an abnormal process condition or some external factor relevant to the platforms environment and well being. The system is in the main automatic, with various levels of action depending on the severity of the anomaly. Manual initiation of the ESD system is available via various pushbuttons and telemetry signal.

An August Systems, CS300 series, triple modular redundant, fault tolerant, safety and control system is utilized for the ESD/fire and gas system.

The system consists of three microprocessor based channels with read only communications between each channel for self checking purposes.

There are four levels of ESD to be provided as detailed below:-

Level 3 - Local process trips

Level 2 - Close well master and wing valves and close all topsides valves excluding diesel supply to the generators. There shall be no de-pressurisation.

Level 1 - Close all well valves including SSSV, close all topsides valves excluding diesel supply to generators and open blowdown valve.

Level 0 - As level 1 plus trip all batteries and generation.

Executive actions from the fire and gas logic to trip and the generation diesel supply valves are routed via the ESD system logic.

There will be a 3 minute delay before a blowdown occurs, this delay being extended to 10 minutes when the platform is manned. As complete removal of power would cause a blowdown, by de-energising the solenoids in the wellhead control panel, this action should be initiated 30 seconds after a blowdown is initiated.

Should a telecommunications failure not be restored within 10 minutes then a level 2 shutdown will be initiated.

In addition to trips caused by adverse process conditions, Levels 0, 1 and 2 can be generated remotely from the onshore terminal via the telemetry and locally from pushbuttons on the ESD/F and G panel. There is a level 0 pushbutton on the helideck.

Full details of all ESD trips are shown on the ESD cause and effect drawings.

All shutdown valves will be hydraulically operated. The ESD system will interface with solenoids mounted in the wellhead control panel which will provide the hydraulic logic and power for the shutdown valve operation.

The fire and gas section of the combined ESD/fire and gas system provides detection and protection facilities for the platform. Fire and gas detection is divided into 6 areas as defined on the cause and effects and interfaces with the HVAC system and RTU/SCADA. Manual alarm points are also provided on each deck, interfacing directly with the fire and gas panel.

The system provides outputs to protection systems, the HVAC, the ESD system, the PA system and the RTU/SCADA.

The interface between the ESD/fire and gas system and the RTU/SCADA system is a serial link. All I/O status will be displayed on the SCADA system and input overrides will be generated from the SCADA keyboard.

There will be a small matrix on the fire and gas panel to cover the extinguishant systems, local ESD pushbuttons and common services.

When a DJU (Drilling Jack Up) is in position the drillers control panel will be connected into the fire and gas system to provide drilling personnel with Level 0 and 1 shutdown facilities, the provision to raise a general alarm, accept alarm and indication of ESD/fire and gas system status.

SAFETY SYSTEMS AND FIRE PROTECTION
The safety philosophy consists of the following essential elements.

a) Segregation of hazardous and non-hazardous areas, as defined in the facilities equipment layout drawings.

b) Provision of fire and gas detection and protection systems.

c) Provision of access, escape routes and safe havens, viz, helideck, sea and control room; coupled with fire and gas warning and alert systems in the process areas, helideck and HVAC inlets.

d) Provision of safety and personnel protective equipment, including life rafts, fire fighting equipment, breathing apparatus and specific clothing and protection can be found located at key sites around the platforms delineated on the safety layout drawing(s).

e) Maximum use of physical separation of process and safe refuge areas, is supplemented where necessary, by the use of blast and passive fire barriers, eg cellar deck to helideck blastwall and fire rated utility building.

f) A water deluge system for external cooling of plant during a fire is supplied when a jack-up drilling rig is ‘working-over’ the platform and connection is made to its fire water supply.

g) A Co2 vent snuffing package, Co2 total flood system for power generation/switchgear rooms and a Halon system for control panel protection.

HVAC System
The HVAC system provides forced ventilation, heating and cooling for the emergency shelter/control room, emergency power room and main power generation room which are located in a non-hazardous area of the platform. A positive pressure of 25 Pa will be maintained in all enclosed areas.

A loss of room pressure switch is provided in the control room, which shall alarm at 25 Pa at the HVAC control and fire and gas panels after a 30 second delay. However as the utility building is a non-hazardous area, the loss of room pressure alarms are for information only and do not initiate any shutdowns.

TELECOMMUNICATIONS SYSTEM
The telecommunications systems provide all the necessary requirements as listed below:-

Weight Data
Topsides 475 Te
Jacket 682 Te
Piles 280 Te
20” caisson 11 Te
30” caisson 23 Te

Architectural 13 Te Doors, cladding, insulation, screeds
Electrical 32.5 Te Generators, cable, racking/trays, DB’s lighting, switchgear etc
Fire and safety 2.3 Te CO2 and vent skids
HVAC 4.24 Te Fans and ducting
Instrumentation 6.5 Te Instruments, tubing, unistrut, control panels etc
Mechanical 60 Te Separator and gas KO drum vessels, diesel, fresh water and drains tanks, deck crane
Piping 23 Te Piping, valves and supports
Structural 315 Te Primary, secondary, blastwall, gratings, plating, handrail, equipment supports etc

Utilities Data
Crane Elec/hydraulical 2 ton @ sea state 1
Air compressor No
Main power generators 2 x 100% @ 54 KW ea
Emergency power 1 x 100% @ 54 KW
Batteries UPS 3 hours
Wireline capability No
Well workover By jack-up
Bedspaces 6 maximum (incorporated with mess)
Firewater pump No
Seawater lift pump Yes
TEMPSC No: structural provision only
Life rafts Yes
Fresh water and diesel tank Yes

CONSTRUCTION CODES AND STANDARDS

Primary Design Codes
Camelot CB was designed and constructed in accordance with the Offshore Installations (Construction and Survey) Regulations 1974, SI 1974 No 289, and the associated guidance notes – Offshore Installations: Guidance on Design, Construction and Certification.

Modifications and additional work to June 1996 were carried out in accordance with these Regulations and the associated guidance notes. From June 1996, SI No 289 has been superceded and replaced by the offshore Installations and Wells (Design and Construction, etc) Regulations, SI 913/1996.

When re-analysed, the structures have been assessed against the contemporary editions of relevant codes and Department of Energy/HSE Guidance Notes.

Piping
All piping has been designed to the requirements of the relevant ANSI code.

Design Data
All design specifications, reports, technical notes, data sheets, lists and schedules are available for review upon request.