{{short description|Semi-submersible drilling vessel}} {{Infobox ship |display_title=ital |section1={{Infobox ship/image |image = |image_caption = }}
|section2={{Infobox ship/career |hide_header = |name =*''Transocean Marianas'' *''P. Portia'' (1996–1998) *''Polyportia'' (1994–1996) *''Tharos'' (1979–1994) |owner = Transocean |operator = Transocean |registry =*{{MHL}}, Majuro *{{GBR}}, Aberdeen 1995-1996<!-- *11 Jan 1995-16 Dec 1996 --> |route = |ordered = |builder = Mitsubishi Heavy Industries |original_cost = |yard_number = |way_number = |laid_down = 13 August 1978 |launched = |completed = |christened = |acquired = 1 September 1979 |maiden_voyage = |in_service = |out_of_service = |identification =*Call sign: V7HC5 *ABS class no: 7904130 *DNV ID: 28301 *{{IMO Number|8757960}} *MMSI no.: 538002209 |fate = Scrapped September 2018 |notes = <ref name=abs/><ref name=dnv>{{cite web | title=Vessel Info: ''Transocean Marianas'' | url=http://exchange-staging2.dnv.com/exchange/main.aspx?extool=myvi&vesselid=28301 | work=DNV Exchange | publisher=Det Norske Veritas | year=2010 | access-date=4 June 2010 | archive-url=https://web.archive.org/web/20110710142128/http://exchange-staging2.dnv.com/exchange/main.aspx?extool=myvi&vesselid=28301 | archive-date=10 July 2011 }}</ref> }}
|section3={{Infobox ship/characteristics |hide_header = |header_caption = |class = American Bureau of Shipping: A1 column stabilized MODU; AMS; ACCU; DP S2 |tonnage = {{GT|20,461}}; {{NetT|61,38}}; {{DWT|10,100}} |displacement = |length = {{convert|91.44|m|abbr=on}} |beam = {{convert|75.8952|m|abbr=on}} |height = |draught =*Operating: {{convert|25|m|abbr=on}} *Transit: {{convert|9|m|abbr=on}} |draft = |depth = {{convert|34.7472|m|abbr=on}} |decks = |deck_clearance = {{convert|12352|mm|ft|abbr=on}} |power = |propulsion = 6 x Electro-Motive Diesel MD-20 3,600hp |speed = 2.0 kts |capacity =*Liquid mud: {{convert|1589|m3|abbr=on}} *Drill water: {{convert|1734|m3|abbr=on}} *Potable water: {{convert|465|m3|abbr=on}} *Fuel oil: {{convert|2941|m3|abbr=on}} *Bulk mud: {{convert|221|m3|abbr=on}} *Bulk cement: {{convert|221|m3|abbr=on}} |crew = 150 |notes = <ref name=abs>{{cite web | title=ABS Record: ''Transocean Marianas'' | url=http://www.eagle.org/safenet/record/record_vesseldetailsprinparticular?Classno=7904130| publisher=American Bureau of Shipping | date=19 October 2009 | access-date=4 June 2010}}</ref> }} }}
'''''Transocean Marianas''''' was an Earl & Wright Sedco 700 design semi-submersible platform drilling unit capable of operating in harsh environments and water depths up to {{convert|7000|ft|m}} using a {{convert|18.75|in|cm|abbr=on|disp=flip}}, 15,000 psi blowout preventer (BOP), and a {{convert|21|in|cm|abbr=on|disp=flip}} outside diameter (OD) marine riser.<ref>{{cite web | title=''Transocean Marianas'' | url=http://www.deepwater.com/fw/main/Transocean-Marianas-77C14.html?LayoutID=17 | publisher=Transocean | year=2010 | access-date=7 June 2010 | archive-url=https://web.archive.org/web/20110709011136/http://www.deepwater.com/fw/main/Transocean-Marianas-77C14.html?LayoutID=17 | archive-date=9 July 2011 }}</ref>
''Transocean Marianas'' has operated under several names: '''''Tharos''''' from 1979 to 1994, '''''Polyportia''''' from 1994 to 1996, and '''''P. Portia''''' from 1996 to 1998.
On October 7, 2009, it began drilling on the Macondo well in the Gulf of Mexico. On November 9, 2009. it was damaged by Hurricane Ida. It was subsequently replaced by the ''Deepwater Horizon'', which was responsible for the Deepwater Horizon oil spill when that rig exploded on April 20, 2010.<ref name="waxman">{{cite web | title = Letter from Henry Waxman to Tony Hayward - June 14, 2010 | format = press release | publisher = nergycommerce.house.gov | date = 2010-06-14 | url = http://energycommerce.house.gov/documents/20100614/Hayward.BP.2010.6.14.pdf | access-date = 2010-06-14 | archive-url = https://web.archive.org/web/20101207021018/http://energycommerce.house.gov/documents/20100614/Hayward.BP.2010.6.14.pdf | archive-date = December 7, 2010 }}</ref>
==''Piper Alpha'' incident== In 1988, as '''''Tharos''''', the vessel operated by Occidental Consortium as a large firefighting, construction, diving support and accommodation vessel equipped with a helicopter and a hospital ship with 22 beds, that rescued survivors from the ''Piper Alpha'' oil platform disaster.<ref>{{cite book | last=Lancaster | first=John Frederick | title=Engineering Catastrophes: Causes and Effects of Major Accidents | location=Cambridge | publisher=Woodhead Publishing | pages=121–122 | year=2000 | isbn=1-85573-505-9 | url=https://books.google.com/books?id=ws-BRoRlelkC&pg=PA122 | access-date=11 June 2010}}</ref> The vessel carried out firefighting on the night of the disaster and supported the fire fighting and well kill operations that led to the extinguishing of the blaze. However, flaws in the design of the vessel's extensible rescue arm prevented it from rescuing crew from the platform, while errors in the operation of the water cannon delayed their use. Divers from ''Tharos'' recovered many bodies from the seabed and from the galley area of ''Piper Alpha''. ''Tharos'''s role in the early hours of the disaster was shown in the 1990 Scottish Television series ''Rescue''.
==2011 Ghana incident== On July 6, 2011, ''Transocean Marianas'' was evacuated due to taking on water off the coast of Ghana.<ref>{{cite news |last1=Dezember |first1=Ryan |title=Transocean Ghana rig stable after taking on water |url=https://www.marketwatch.com/story/transocean-ghana-rig-stable-after-taking-on-water-2011-07-07 |access-date=12 January 2019 |work=MarketWatch |publisher=Dow Jones & Co |date=7 July 2011 |location=New York}}</ref>
==Disposal== In September 2017 Transocean announced that ''Transocean Marianas'', along with five other laid up rigs, would be retired and disposed of for recycling.<ref>{{cite web |title=Transocean Ltd. Announces Retirement of Six Floaters |url=https://www.deepwater.com/news/detail?ID=2302291 |publisher=Transocean Ltd |access-date=12 January 2019 |date=22 September 2017}}</ref>
==References== {{Reflist}}
==Further reading== * {{cite hansard | speaker= Hamish Gray | position= Secretary of State for Energy | url=https://api.parliament.uk/historic-hansard/written-answers/1981/dec/10/emergency-support-vessels-north-sea | house=House of Commons |title= Emergency Support Vessels (North Sea) | date=10 December 1981 | column_start=468W | column_end=469W}} * {{cite hansard | speaker= Peter Morrison | position= Secretary of State for Energy | url=https://api.parliament.uk/historic-hansard/written-answers/1990/jan/16/oil-and-gas-safety | house=House of Commons |title= Oil and Gas (Safety) | date=16 January 1990| column=188W}} * {{cite hansard | speaker= Alick Buchanan-Smith | position= Secretary of State for Energy | url=https://api.parliament.uk/historic-hansard/written-answers/1985/nov/11/semi-submersible-tharos-incident | house=House of Commons |title= Semi-submersible ''Tharos'' (Incident)| date=11 November 1985| column_start=53W | column_end=55W }}
==External links== *[http://www.deepwater.com/ Transocean official website] * [http://www.vesseltracker.com/en/Ships/Transocean-Marianas-8757960.html ''Transocean Marianas'' current position] at ''VesselTracker''
Category:1979 ships Category:Drilling rigs Category:Semi-submersibles Category:Ships built by Mitsubishi Heavy Industries Category:Ships built in Singapore Category:Transocean