Environmental statement - Flyndre and Cawdor - Maersk Oil

Flyndre and Cawdor Environmental Statement
Section 2 Proposed Development
flow meters for measuring gas and liquid hydrocarbon flow respectively will be utilised. A new
coriolis flow meter is proposed for the measurement of the PW.
A new oil metering station shall be provided on the oil outlet stream from the Clyde 2 nd stage
separator and a new connection between the Orion flowline and the existing Clyde test separator
shall also be provided. It is anticipated that the oil metering station will consist of 2 × 100% coriolis
meters in parallel, complete with sampling facilities.
2.8.3. WATER TREATMENT
The majority of PW in the Flyndre and Cawdor reservoir fluids is expected to separate from the oil
stream in the Orion production separator. In order to measure the water produced by the Flyndre
and Cawdor development the water will be treated in a dedicated treatment package and discharged
overboard. Any water carry over will pass to the Clyde third stage separator, which in turn ties into
the crude oil dehydrator which has a long residence time and is provided to remove the last few
percent of water from the oil stream to achieve the oil export specification of 0.2% basic sediment
and water.
2.8.4. FLARE SYSTEM
As part of the development of the Flyndre and Cawdor fields there will be limited modifications to the
Clyde as existing equipment is to be reused, however pipeline operations will increase flaring from
the platform. Should the pipeline shutdown (planned or unplanned) extend beyond a defined ‘no
touch time’ the pipeline will cool down to a temperature where hydrates may form. To mitigate this,
the pipeline pressure requires to be reduced thus requiring flaring of the pipeline inventory. Restart
of the pipeline will require a period of low pressure production to ensure the pipeline temperature
rises above the hydrate potential limit prior to pressurisation. During this low pressure phase, gas
flaring will be required from separation as operating pressure will be too low to access the HP gas
compressor. The potential to minimise flaring by utilising LP compression will be considered as an
option during FEED.
If restart of the pipeline can be achieved within the ‘no touch time’ limit, gas flow direct to HP
compression will be possible and so no additional flaring will be required. If the nature of the
shutdown causes the pipeline to pack above normal settle out pressure, then the pipeline pressure
will require blowdown to a safe level prior to restart.
At the time of writing this ES, the specific operating requirements to accurately determine flaring
limits had not been defined. An additional annual flaring load has been calculated on the following
basis;
24 hour ‘No Touch Time’
one of the annual Clyde planned shutdowns extending beyond no touch time
six of the annual Clyde unplanned shutdowns extending beyond no touch time
50 bar gauge pipeline settle out pressure
120 bar gauge to 80 bar gauge pipeline pressure pack blow down required once per year
24 hour flaring required to warming pipeline at a flowrate of 12 MMscfd
On this basis the annual additional flaring load as a result of Flyndre and Cawdor development is
estimated at 2,750 tonnes of gas. 17,755 te of gas were flared on the Clyde platform in 2010 (EEMS,
2010).
It should be emphasised that the data presented for anticipated additional flaring load is preliminary
and subject to change as the design develops.
2‐ 20 D/4114/2011