Environmental statement - Flyndre and Cawdor - Maersk Oil

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Flyndre and Cawdor Environmental Statement Section 2 Proposed Development designed to reduce the oil in water content (OIW) from typically 100‐500 ppm on the inlet to less than 25 ppm on the outlet. The level of PW in each vessel is controlled by interface level controllers. The position of the interface may be readily adjusted, to suit operating conditions and water cut, to achieve sufficiently clean discharged water. Each PW flow is measured. Each line is also provided with corrosion monitoring probes and a sample point. 2.7.5. FLARE SYSTEM The flare and vent systems are provided to collect releases of hydrocarbon gas from process systems under normal and emergency conditions and dispose of them safely. The flare system collects releases of a significant rate which are burnt, whereas the vent system collects small quantities of gas vented as a result of ‘breathing’ of low‐pressure tanks, and releases these directly to atmosphere without being burnt. Flare gas is burnt at the end of a boom cantilevered from the northeast corner of the platform. Vent gas is released at a point halfway up this boom. In general all relief valves fitted to process systems, which prevent mechanical failure due to overpressure, are directed into flare collection headers. Flared gas is collected, has condensate removed, and is burnt in two separate systems: HP system, which takes gas from all moderate or high‐pressure sources. The gas flows via the HP knock‐out drum, V2501, to the HP flare tip where it is burnt. The HP flare tip is a low emissivity type. It operates at high velocity to burn gas efficiently and without smoke. LP System, which takes gas from low‐pressure users which cannot flow into the higher pressure HP System. It also takes gas releases from blowdown of gas compressors (where a very low final pressure is required to prevent compressor seal leakage). The LP flare gas flows via the knock‐out drum, V2502, to the LP flare tip where it is burnt. The HP and LP flare tips are mounted as a single assembly at the end of a 73.5 m long boom, which is positioned at the north east corner of the platform and angled at 45° to the horizontal. Boom length, position and angle were chosen to take advantage of prevailing wind direction in blowing the flared gas away from the platform, and minimise radiation levels and the effect of hot flare plume on the platform. Total fluids flared on the Clyde platform in 2010 was 17,755 tonnes (EEMS, 2010). 2.7.6. POWER GENERATION AND FUEL USE The main power is generated by seven gas turbine generators. Auxiliary power, produced by two diesel driven generators, is available to maintain supplies to priority services in the event of failure of the main stream. The primary power generation systems on the Clyde platform are outlined in Table 2‐11. A further level of emergency support is provided by the uninterruptible power supplies system. This is battery powered and ensures that life‐support and safety systems are maintained under emergency conditions. The batteries are kept charged during normal operations by the main electrical supply. 2‐ 18 D/4114/2011
Flyndre and Cawdor Environmental Statement Section 2 Proposed Development Combustion Equipment AGT TB5000 Gas Turbine Generator (7 in total) Caterpillar 3516 Drilling Engine A Ruston 8RKC Drilling Engines (2 in total) TAG No. Fuel GZ‐41‐01 A /B/C/D/E/F/G Dual GZ‐98‐01A Diesel GZ‐98‐01B/C Diesel Primary Duty WHR Max. Thermal input (MWth) Rating Max. Load (MW) Peak Thermal efficiency (%) Main power generation No 15 3.6 25 Power Generation Power No 6.20 1.82 29 Generation Mo 6.2 1.82 29 Table 2‐11 Main power generation & drilling power generators in use on the Clyde platform (Clyde PPC permit; Ref PPC34) The total fuel use for power generation on the Clyde platform in 2010 was 8,152 tonnes of diesel and 24,371 tonnes of gas (EEMS, 2010). 2.8. FLYNDRE AND CAWDOR – OVERVIEW OF PROPOSED FACILITIES 2.8.1. PRODUCTION PROCESS One of the main drivers for the development of Flyndre and Cawdor is to minimise the impact on existing Clyde facilities and maximise the re‐use of existing equipment. The pipe‐in‐pipe subsea line will terminate at a subsea isolation valve (SSIV) within the Clyde 500 m zone. An 8" nominal bore (NB) pipeline will be routed from the SSIV to the existing bank of J‐tubes on the west side of the platform. An 8" NB rigid riser will be pulled up through one of the existing spare 16" NB J‐tubes, with the umbilical pulled through the matched spare 10" NB J‐tube. New dedicated Flyndre/Cawdor subsea support systems will be installed on the Clyde platform. The existing Orion separator on the Clyde platform will be dedicated to receive Flyndre/Cawdor fluids and Orion production will be re‐routed to the Clyde 2 nd stage separator. The Orion separator will be converted from a two phase to three phase operation as per the original vessel design. Dedicated produced water treatment facilities will be provided, with the treated water discharged overboard via an existing produced water disposal caisson. The re‐routed Orion production fluids will be commingled with existing Clyde production upstream of the Clyde 2 nd stage separator. The 2 nd stage separator inlet device will be replaced with a vane type device to handle the additional vapour load from re‐routing Orion production fluids. To maximise Flyndre/ Cawdor production, the HP and export compressors will be re‐wheeled, new internals installed in the HP compressor discharge scrubber and the export compressor suction scrubber plus dehydration condensate knock‐out drum will be replaced. The pressure profile and design conditions across the compressor will not be modified. The compressor will operate at the same speed utilising the installed driver. 2.8.2. METERING Flow measurement of the Flyndre and Cawdor production is required to determine the tariff for the use of the Clyde facilities. This will be achieved by the measurement of gas, hydrocarbon liquid and water flows from the Orion separator. It has been determined that the existing ultrasonic and coriolis D/4114/2011 2‐19
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Environmental statement - Flyndre and Cawdor - Maersk Oil

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