Thunder Horse Field, Gulf of Mexico, United States of America
British Petroleum (BP) is planning to start-up additional production from Thunder Horse North field in the first half of 2009. In December 2008, BP started production from its third and fourth wells at the Thunder Horse field with production now in excess of 200,000 barrels of oil equivalent per day (boed).
Thunder Horse production-drilling-quarters (PDQ) is the world's largest production semi-submersible ever built. The platform's topside area is the size of three football fields. It is packed with equipment and systems capable of processing and exporting a quarter of a million barrels of oil per day. This structure aims to realise oil and gas production in one of the largest hydrocarbon locations in the Gulf of Mexico.
The floating platform operates under critical conditions. It pumps out oil and gas from the reservoir which is three miles beneath mud, rock and salt, and topped by a mile of ocean, and works under pressures over 1,200 bar and temperatures of 135°C.
The platform has a dual derrick. The main rig has a hook load capacity of 1,000t while the second derrick is an auxiliary which saves time making up drill strings and supports completions and workover operations simultaneously. The helideck is sized for an S-61 with another S-61 parked.
In 2005, the platform was severely disrupted by a hurricane. The floating platform was due to reschedule oil and gas production by the end of 2008. However, following a failure during pre-commissioning checks, there was a need to repair and replace components in the subsea system. The subsea equipment had remained in a cold state since 2005 hurricane and it could not perform the intended high pressure and high temperature service.
The Thunder Horse field is located in Mississippi Canyon Blocks 776, 777 and 778, in the Boarshead Basin, 125 miles south-east of New Orleans. It is the largest field in the Gulf of Mexico and lies at a water depth of 6,000ft. The field was discovered in 1999. BP operates the development (75% interest), with co-venturer ExxonMobil owning the balance. The reservoir consists of Upper Miocene turbidite sandstones 6,000m beneath the seabed in 1,900m of water.
The Thunder Horse discovery well was drilled in 1999 on Mississippi Canyon Block 778. It was drilled to a depth of 25,770ft, from the drillship Discoverer 534 and found 520ft net of pay in three intervals.
Thunder Horse 2 was drilled in Block 822. It reached its total depth of 29,060ft in November 2000. The well was drilled by the Discoverer Enterprise in 6,300ft of water, 1.5 miles south-east of the discovery well. It encountered 675ft net of pay in three primary intervals.
In February 2001, a new field - Thunder Horse North - was drilled in Block 776, 5 miles northwest of Thunder Horse. The discovery encountered 581ft net of accumulated hydrocarbons in three intervals. It was drilled in 5,640ft of water by the Discoverer 534 and reached a total depth of 26,046ft.
The development consists of 25 wet-tree subsea wells tied into a floating platform.
In May 2000, BP contracted Mustang Engineering to provide preliminary front-end engineering / design services for the PDQ (production drilling quarters) semi submersible platform. It weighs more than 50,000t and will produce from some of the deepest wells in the Gulf. The semisubmersible has a displacement of 130,000t.
The facility is designed to process 250,000b/d of oil and 200mmcf/d of gas per day. The topside construction was carried out by J Ray McDermott in Morgan City, Louisiana, while the 15,000m³ hull was built by Daewoo Shipbuilding at its Okpo yard in South Korea.
The hull weighs 60,000t and displaces 129,000t. It consists of four columns - two 22m x 26m x 36m and two 22m x 23m x 36m. They are connected by 11.5m pontoons. In construction, 330 blocks were required for the hull's regular pontoons as well as the four corner boxes. A 10m-deep deck box spans the columns.
The topsides will handle a HP/HT wellstream and export 250,000b/d of oil and 5.6 million m³/d of gas. It will also treat 140,000b/d of produced water and inject up to 300,000b/d of mixed produced water and seawater for reservoir support. The layout is based on three production / utilities modules for production, compression and power generation with topside modules with lift weights of 21,000t. The main power generation capability is 90MW.
It has accommodation for 229 persons.
Oil and gas transportation
Oil and gas produced by Thunder Horse is transported to existing shelf and onshore pipelines via the Proteus and Endymion oil pipeline systems and the Okeanos gas pipeline system. These pipelines are part of the Mardi Gras Transportation System. BP has an equity interest in both the pipeline systems, with 75% ownership interest in the Proteus and Endymion pipelines and a 66 percent stake in the Okeanos pipeline system.