Mississippi Canyon block 252, offshore Louisiana, Gulf of Mexico, USA
Deepwater Horizon rig
The Macondo prospect is situated on Mississippi Canyon block 252 (MC 252), offshore Louisiana, Gulf of Mexico, USA, and is owned and operated by British Petroleum (BP).
The initial exploration plan for the project was submitted by BP to Minerals Management Services (MMS) in March 2009. The plan included drilling and temporary abandonment of two exploration wells over the prospect. The operator took control over the prospect through the Lease Sale #206 by MMS in March 2008.
Deepwater Horizon explosion
Drilling over the prospect was initially planned to be carried out by Transocean’s Marianas rig, but later changed to Deepwater Horizon. Deepwater Horizon caught fire when it was drilling at Macondo in April 2010. The rig sank into water after the accident and is currently lying over the sea floor, around 1,500ft northwest of the well centre and away from subsea pipelines.
At the time of the accident, it was located at 52 miles southeast of the Louisiana port of Venice. The rig was leased by BP for exploration over the Gulf of Mexico until September 2013.
The operator, US Coast Guard and other agencies are engaged in the execution of an oil spill response plan to recover the oil. Transocean’s drilling rig Development Driller III (DD3) is expected to arrive soon at the location to drill relief wells.
A regional shallow hazards survey and study was carried out at the project area by KC Offshore in 1998. High resolution (HR), 2D seismic data along with 3D exploration seismic data of the MC 252 was collected by Fugro Geoservices in 2003. Mapping of the block was carried out by BP America in 2008 and 2009.
Deepwater Horizon rig
The rig is a fifth-generation deepwater semi-submersible rig and is owned by Transocean. It was built by Hyundai Heavy Industries at Ulsan Shipyard in South Korea. The construction of rig started in 1998 and was completed in 2001.
Deepwater Horizon is 396ft long and 256ft wide. It can operate at depth of 8,000ft under water and can be expanded to a maximum depth of 10,000ft under water. The maximum total drilling capacity is 30,000ft.
The rig started drilling a well at a water depth of 5,000ft in MC block 252 in February 2010, but exploded during drilling in April 2010. The rig was on fire continuously for three days.
The well was planned to be drilled to 18,000ft, and was to be plugged and abandoned for later completion as a subsea producer.
As per the plan, the rig was supposed to be drilling the second of the two wells planned. But it faced oil spills over two fronts: one at the wellhead and another at the surface offshore. The wells are located in lease G-32306 over the prospect.
BP started a major oil well intervention and oil spill response (OSR) plan on the sinking of the rig. The OSR team recovered over 1,000 barrels of an oil-water mix, out of which a significant portion is water.
BP is facilitating Transocean work beneath the surface on the subsea equipment with use of remotely operated vehicles to monitor the well. The blow-out preventer is to be mobilised and activated. Relief wells are also planned to be drilled to secure the well.
The drilling rig DD3 will drill a second well to intercept the Macondo well and inject a specialised heavy fluid to control the flow of oil or gas. Further, the well will be sealed permanently.
Equipment including 100,000 gallons of dispersant are ready to be deployed along with 32 spill-response vessels including skimmers, tugs, barges and recovery vessels. Five aircraft will be used for dispersant deployment.