Stage Separator Modification

Transkript

1 Njord 1 st Stage Separator Modification TEKNA seminar: Separation Technology oil/gas/water/sand Quality Airport Hotel Stavanger 26 th - 27 th September 2007 Rolf Torvik Operation Engineer Njord Oil & Energy

2 Njord where and what? Block 6407/7 and 6407/10, 130 km North West of Kristiansund Two installations: - Njord A: Drilling, production and living quarters. Oil export to Njord Bravo - Njord Bravo: Manned during maintenance and loading. Njord Kristiansund Fram Gjøa Troll B - C Bergen Production start 30. Sep % of commercial reserves produced Hydro operator with 20% Partners: - E.On Ruhrgas (30%), GdF (20%), ExxonMobil (20%), Endeavour (2.5%) og Petoro (7.5%)

3 Overview Njord gas export Topside - New gas dewatering system - New metering facilities (gas) - Using existing compression process on Njord Subsea - New 10 riser and new riser balcony - New 12 gas pipe - Tie-in to Draugen PLEM on Åsgard pipeline

4 Njord main process

5 Njord 1 st stage separator Existing Design

6 Njord 1 st stage separator Existing inlet design Company 3: Proposed utilising a snail-housing inlet device. Cannot be undertaken within RS Various technical concerns regarding issues of mechanical support of such a device and practicality with regard to size and manhole limitations Proposed simplifying current inlet by removing crossbars as shown below

7 5th stage scrubber (summer 2003)

8 Historie Kompressorhavari i 2000 som resulterte i utskiftning av samtlige scrubbere i 2001 Lekkasje i 5. trinns kjøler 1999, avdekket mye voks Forsøkt med vokshemmer (PI-780) oppstrøms 5. tr. kjøler, liten effekt Voksproblemer i 5. tr. kjøler, hvor det i 2002 ble satt i gang et prosjekt for å finne årsakene - Måling på skumnivå i separatorer - Måling på væskeinnhold i gassen fra 4. og 5. tr. væskeutskillere - Skumdemper test - Task force

9 Historie forts. Injeksjon av skumdemper med marginal virkning på avvoksingsfrekvens. Stoppet sommeren 2003 Problemer med LV-reguleringsventil nedstrøms 5. trinn siden dag 1. Registrert 34 WO i SAP (fra 1998) Fortsatt voksproblemer i ventiler i 2004

10 Historie forts. Inspeksjon 1.tr. sep. sommer 2003 avdekket at gassutløpet (dråpefanger) var snudd feil vei. Etter kontakt med leverandør skulle ikke dette ha så mye å si for utskillelse av væske fra gassen Rengjøring sommer 2003 avdekket mye voks i kjølerere og i 5. trinn væskeutskiller Innmat i 4. trinn væskeutskiller byttet sommer 2003, avvoksing meget sjelden etter dette Stopp vinter 2004 ble strainere oppstrøms 4./5. tr. kompressor fjernet, ikke avdekket voks. Nytt kompressorhavari april 2006 voks i seal-olje

11 Njord 1 st stage separator Identified problems with existing vessel - High mixing in inlet section - Short distance from inlet to vane pack - Drainage capacity of downcommer small compared to drainage capacity of the Vane Pack - Poor gas distrbution across vane pack - Possible foam creation in the inlet section High mixing in inlet Short distance from inlet to inlet demister

12 Njord 1 st stage separator Changes to the separator - New inlet section that lowers the mixing in the inlet - Perforated plates to isolate the high velocity section across the inlet - Mesh pads in the full cross sectional area of the vessel - Foam breaking - Coalescence of droplets - Optimised mesh pad with dual layer - Turning of the vane packs to better utilise the vessel volume for settling - Mesh pads in front of the vane pack - Coalescence/Agglomoration of droplets into the Vane Pack - Improve gas distribution across the Vane Pack - Increase the liquid capacity of the downcommer to match the capacity of the Vane Pack by increasing the diameter of the downcommer New inlet section Internals in vessel

13 Njord 1 st stage separator Stage 1 modification Company 1: Alternative design with shortened installation time including 1 off Inlet Vane Distributor 2 off single perforated plates in the gas phase 2 off mesh pads in the gas phase 2 off mesh pad infront of the vane packs Increased area downcommers for the vane packs

14 Njord 1 st stage separator Stage 2 modification Company 2: Proposed inlet cyclonic device, removal of distribution plate and liquid outlets move to separator ends.

15 Njord 1 st stage separator Stage 2 modification Company 1 Extend the cyclones to the end of the vessel remove plate - Cons -May create maldistribution in inlet -Has to move the demister towards the center of the vessel Have cyclones central with a bucket - Cons -Solid accumualtion in the bucket -Possible short circuiting from inlet to outlet through bucket -Has to keep the horizontal plate that reduces the available gas volume Extend the outlets to the end of the vessel - Cons -Current level detector is located at the center of vessel needs to be moved

16 Njord 1 st stage separator Tracer study HP Production 1 Manifold Injection point 8 Ring of 4 detectors N/E/S/W Ring of 4 detectors N/E/S/W detector 14 (control) To 4 th stage suction cooler 6 Produced water 7 To 2 nd stage separator

17 Tracer study results Before modification - 1 st stage separator: The trials conducted in August 2006 show that there was between % (relative to oil rate) carryover from the 1st stage separator ( m3/h) The measurements were carried out at varying gas through-put from 9.0 to 9.6 MMSm3/d. No foam breaker chemicals were used. No foam layer was observed using a scanning technique. - 4 th stage scrubber: Carryover measured to 8-10 m3/h i.e. scrubber efficiency of about 80-85% After modification -Verification - No carryover was measured during trials conducted at 10.1MMSm3/d (February 2007)

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