The Johan Castberg FPSO · The FPSO is designed to resist loads from extreme and abnormal wind, wave and current (open water conditions) • The robustness in case sea ice or icebergs

The J oha n Ca stberg FPSO -sea ice a nd iceberg risks

Presentation prepared on behalf of the Johan Ca stberg license to the PSA Construction Da y

Open 27 August 20 18

The J oha n Ca stberg Fie ld Development

• PL 532: Equinor 50 %, Eni 30 %, Petoro 20 %• Discoveries ma de in 20 11 a nd 20 12 – proven volumes between

40 0 a nd 650 mill. ba rre ls of oil• Approxima te ly 10 0 km to the north of Snøhvit fie ld a nd 240 km

a wa y from Melkøya• Wa ter depth 360 – 390 m• Consist of a n FPSO a nd subsea structures• Pla nned production sta rt 20 22

2 | The J oha n Ca stberg FPSO - sea ice a nd iceberg risks

Open 27 August 20 183 | The J oha n Ca stberg FPSO - sea ice a nd iceberg risks

Physica l environment a t J oha n Ca stberg

Figure ba sed on a rticle published by Institute of Ma rine Resea rch


Frequency of occurrence – Sea ice


Ice be lt

Very close drift iceClose drift ice

Open drift ice Open drift ice

Very open drift ice

https://www.google.com.hk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwiMtNq3yYrMAhXJupQKHXtxBEcQjRwIBw&url=https://www.nasa.gov/topics/earth/features/arctic-seaice-study.html&psig=AFQjCNES-WvtfehH8lf-g37hg_oXcrygzg&ust=1460601085679505


Frequency of occurrence – Sea ice



Frequency of occurence – Sea ice


From Fritzner & Sa gerup, 20 16

• Severa l studies ha ve a ddressed extreme a bnorma l ice extend in the Ba rents Sea .

• Equinor conclusion: • The a nnua l proba bility of sea ice a t J oha n

Ca stberg is 10 -4 or less

Source : DNV GL 20 14


Frequency of occurence - icebergs

• Frequency of iceberg impa ct estima ted to be in the ra nge 10 -4 to 10 -5

per yea r


From J orda a n e t a l, 20 14

Figure prepa red by MultiConsult ba sed on ma ps in Abra mov Atla s of Arctic Icebergs (1996)


Adressing the ice risks

• Since the frequency of ice intera ctions is very low, the ice risks a re ma inly mitiga ted by opera tiona l mea sures• Production shut down• De-ma nning• Increa se dra ft

• The FPSO is designed to resist loa ds from extreme a nd a bnorma l wind, wa ve a nd current (open wa ter conditions)

• The robustness in ca se sea ice or icebergs intera ct with the hull ha ve been checked



FPSO in sea ice - a pproa ch

• Ana lytica l models + empirica l da ta (ISO 1990 6)• Ta nk model tests• Numerica l simula tions• Historica l full sca le da ta

• Identify fa ilure modes• Define a ccepta nce crite ria• Eva lua te results from ta nk tests a nd simula tions



Critica l fa ilure modes a nd a ccepta nce crite ria

Hull• Globa l loa ds

• Inta ct hull – wa ter ingress not a ccepted

• The hull sha ll resist the combined effect of sea ice , winds, wa ves a nd currents

• Loca l loa ds• Inta ct hull – wa ter ingress not a ccepted

• Pla stic deforma tions of pla tes, fra mes, a re a ccepted but not loss of integrity due to loca l ice pressures

• Loss of sta bility• Inta ct sta bility in the ca se sea ice ca use loa ds equiva lent to ma x ca pa city of the mooring system

• Ma x FPSO motions under a sea ice event sha ll be within a ccepta nce crite ria of motions a s dicta ted by wa ve induced motions.



Critica l fa ilure modes a nd a ccepta nce crite ria

• Turret• Sea ice under the turre t is not a ccepted• Ice loa ds tra nsferred from hull to turre t sha ll be within the ca pa city a s dicta ted by metocea n loa ds (a bility to va ne sha ll rema in

inta ct)

• Mooring system• The mooring system sha ll resist loa ds tra nsferred from hull due to sea ice• The mooring system sha ll resist combined effects from sea ice , winds, currents a nd wa ves

• Risers• The risers sha ll not be directly exposed to sea ice• Loa d effects from sea ice sha ll not ca use da ma ge to riser ba se• Da ma ge to riser ca used by loa d effects from sea ice a re tolera ble

• Requires tha t production is shut down prior to ice encounter a nd inspection of riser/repla cement prior to production resta rt.



Ta nk model tests


Note of ca ution: Due to sca ling effects a nd presence of ta nk wa lls, observa tions a nd recorded loa ds ca nnot be interpre ted a s the a bsolute truth!


Numerica l simula tions


Note of ca ution: Simula tion tools a re still imma ture a nd not sufficiently well documented. Results a re therefore not interpre ted a s the a bsolute truth


Loca l pressures

• Ma x pressures estima ted by use of a proba bilistic model described in ISO 1990 6

• Exposure time ta ken into a ccount• Severa l da ta sources for ice pressures recordings a va ila ble but da ta from the

Bering Stra it wa s a pplied for J oha n Ca stberg (considered more representa tive tha n other da ta se ts).

• From studies of the recorded da ta a number of importa nt findings were ma de:


• Side longitudina ls in High Pressure Zone increa sed from 12 mm to 15 mm due to possible ice pressure

• No other cha nges triggered by ice risk


Summa ry of key a ssumptions – sea ice



Iceberg loa ds

• Some simple a ssessments re la ted to impa ct between FPSO a nd icebergs ha ve been ma de• Wha t is the iceberg loa d exceeded with a nnua l proba bility 10 -5?

• Sta tistica lly 3 impa cts in 10 0 0 0 0 yea rs (when growlers a nd bergy bits a re included)• The kinetic energy ha ve been ca lcula ted a nd compa red with a ccepta nce criteria for ship impa cts

• 10 -5 iceberg < 10 MJ• Visiting supply vessels 40 MJ• Visiting shuttle ta nkers 10 0 MJ

• Iceberg impa ct forces ca lcula ted during a J IP with C-Core a nd DNV GL a nd is a lso found to be significa ntly less tha n design forces for other compa ra ble insta lla tions.

• Significa nt uncerta inties re la ted to iceberg impa cts a nd the risk is further reduced by increa sing the knowledge ba se• Study on iceberg a rea l densities• J IP study on iceberg impa cts with C-Core a nd DNV GL

• If new knowledge shows tha t iceberg loa ds a re more frequent a nd more severe tha n expected, use of physica l ice ma na gement (iceberg towing) will be considered to reduce the risks further.



Summa ry

• Design of the J oha n Ca stberg FPSO is driven by tra ditiona l metocea n conditions

• Substa ntia l efforts ma de to investiga te robustness in ca se the FPSO is exposed to ice

• Robustness seems well documented• An ice risk ma na gement system sha ll be implemented in order to

keep ice risks a s low a s rea sona bly pra ctica l• Surveilla nce – Alerting – Shut down a nd down ma nning

• In pa ra lle l with the fie ld development Equinor continues to strengthen the knowledge ba se re la ted to the Ba rents Sea ice conditions a nd ice-structure intera ctions.

• The possibility to colla bora te with others on these subjects is a pprecia ted


© Equinor ASAThis presentation, including the contents and arrangement of the contents of each individual page or the collection of the pages, is owned by Equinor. Copyright to a ll ma teria l including, but not limited to, written ma teria l, photogra phs, dra wings, ima ges, ta bles a nd da ta rema ins the property of Equinor. All rights reserved. Any other use , reproduction, tra nsla tion, a da ption, a rra ngement, a lte ra tion, distribution or stora ge of this presenta tion, in whole or in pa rt, without the prior written permission of Equinor is prohibited. The informa tion conta ined in this presenta tion ma y not be a ccura te , up to da te or a pplica ble to the circumsta nces of a ny pa rticula r ca se , despite our e fforts. Equinor ca nnot a ccept a ny lia bility for a ny ina ccura cies or omissions.

Kenneth J . Eik – Advisor Pla tform Technology – Metocea n & Arctic Design

The J oha n Ca stberg FPSO - sea ice a nd iceberg risks


Ba ckup slides



Fysiske vurderinger - 1• Opprinnelig a nta tt a t la ngva rig periode med nordlige vinder

på krevd for å bringe is ned til J oha n Ca stberg.• Ona rheim et a l. (20 15) dokumenterte sa mmenheng mellom

innstrømming a v va rmt va nn til Ba rentsha ve t og a rea l a v sjøisdekke på følgende å r.

• Unnta ket er å r med dominerende nordlige vind (20 0 3)• Studier a v iska rt viser imidlertid a t sjøis ikke va r spesie lt næ r J C i

20 0 3.

Både langvarige nordlige vinder og redusert influks av varmt vann nødvendig for å trekke is ned til JC!

1 juni 20 1720


Fysiske vurderinger - 2• Betra ktning a v fysisk miljø i å r med stor isutstrekning; ACSYS 1850 -99

• Liten va ria bilite t i isutstrekning sør for Bjørnøya• Avsta nd JC til næ rmeste is omtrent som ved da gens forhold• I å rene 1886-87 ha ng Vestisen sa mmen med Østisen

1 juni 20 1721


Fysiske vurderinger – 2 forts.• Historiske endringer

• Utstrekning a v Vestisen omtrent dobbelt i forhold til da gens forhold• «Den lille istid» (1550 - 1850 ) førte a nta gelig til store isma sser i polha vet som ble fra kte t

sørover i Fra mstredet.

• Hypotese: Framherskende vestlige vinder har ført ismasser fra Vestisen sammen med Atlanterhavsvann som har fraktet isen videre østover

• Hvis hypotese er korrekt så vil ikke forutse tningene for sjøis til J C væ re tilstede i fe lte ts levetid.

1 juni 20 1722


Fysiske vurderinger – 3 • Hva er sa nnsynlig effekt a v Atla nterha vsva nn og bølger på sjøis som fra ktes sørover?

• Sjøtempera tur 4-5°C va rmere enn isens frysepunkt også i e t ka ldt å r.

• Hs 2.2 m i snitt gjennom vinteren

• Simulering a v isfje lldrift viser a t isfjellmed L=10 0 m, B=50 m og H=20 m vil væ re brutt ned til en 1 m la ng isklump fra Ba r0 3 til J C

1 juni 0 17


Fysiske vurderinger – 4 • Hva skjer med fla kstørre lse nå r sjøis eksponeres for bølger over tid?

• Bølger vil brekke opp is minst 50 km inn i isdekket potensie lt opp til 20 0 km dersom is driver fra Ba r0 3 til J C.

1 juni 20 1724

Documents

The Johan Castberg FPSO · The FPSO is designed to resist loads from extreme and abnormal wind, wave and current (open water conditions) • The robustness in case sea ice or icebergs