Located 190 miles (145 kilometers) offshore New Orleans in the Atwater Foldbelt, the Mad Dog oil and gas field is one of the largest discoveries in the Gulf of Mexico with estimated reserves ranging from 200 to 450 MMboe. Situated in water depths of 4,500 to 6,800 feet (1,372 to 2,073 meters), the field achieved a number of industry firsts through its innovative field development solution.

Operated by BP with 60.5% interest, Mad Dog spans a number of blocks in the southern Green Canyon, including Green Canyon Blocks 825, 826, 738, 739, 781, 782 and 783. Project partners on the field are BHP Petroleum with 23.9% and Chevron with 15.6%.

Exploration

Discovered in December 1998, Mad Dog reservoirs are located below a 6,000-foot-deep (1,829-meter-deep) salt block and within highly mobile tar deposits. The discovery well was drilled on Green Canyon 826, encountering 300 net feet (91 net meters) of hydrocarbons.

The first appraisal of the field, Mad Dog #2 encountered 250 feet (76 meters) of net oil pay in February 2000. Drilled by the Ocean Confidence Semisub two miles north of the discovery well, Mad Dog #2 was drilled to a total depth of 20,268 feet (6,178 meters).

Completed in January 2001, the Mad Dog #3 appraisal well reached a total depth of 21,810 feet (6,648 meters) and intersected 200 net feet (61 net meters) of hydrocarbon sands. A sidetrack was then drilled just southwest of the #3 well, confirming the lateral extent and thickness of the find.

Field Development

Approved by project partners in February 2002, Mad Dog field development included subsea wells tied to a truss spar equipped with an integrated drilling rig, dry trees and 16 wells slots. The overall cost of the development is approximately $1.5 billion.

Permanently moored in 4,300 feet (1,311 meters) of water, the Mad Dog truss spar is located on Green Canyon Block 782. The largest single-piece truss spar, the Mad Dog truss spar is capable of processing 100,000 bopd and 60 MMcf/d (1.7 MMcm/d) of natural gas. With a constant staff of 150, the production platform was designed to both produce and drill at least 12 wells simultaneously. In November 2000, J. Ray McDermott was awarded the construction contract for the facility's topsides, including the production equipment, drilling rig and permanent quarters.

Installed by Heerema Marine Contractors' Balder deepwater construction vessel, the Mad Dog truss spar led the industry with a number of firsts. Weighing in at 8,000 tons, the topsides was the largest single-hook load lift in the Gulf of Mexico. The company broke another industry record for the installation of the first 24-inch-diameter steel catenary riser to the Mad Dog spar. The first polyester rope mooring system approved for use on a permanent facility in the Gulf of Mexico, the mooring system uses the largest diameter polyester rope ever made.

Current field development includes eight dry tree wells tied-back to the production facility. Should the need arise to increase production capacity, the Mad Dog truss spar was built to accommodate more processing equipment, another topsides, water flood equipment, or additional risers from subsea producers. Additionally, the facility boasts an additional 1,000 tons (907 tonnes) of reserve buoyancy to support future growth.

Production

Initial production commenced on Mad Dog on Jan. 13, 2005, ramping up over the year. Oil from the field is exported through the Caesar pipeline, while natural gas is transported through the Cleopatra gas line. With a field life of 20 years, Mad Dog should prove to be a major producer in the Gulf of Mexico.

Field Extended: Mad Dog South

Post production start-up, the Mad Dog field was further extended in March 2005. An appraisal well was drilled on the Mad Dog Southwest Ridge, intersecting 300 feet (91 meters) of net oil pay in the early Miocene formation, as well as hydrocarbons approximately 700 feet (213 meters) deeper on the west flank of the structure than previously encountered. Drilled by the Discoverer Spirit drillship to a total depth of 22,890 feet (6,977 meters) in approximately 5,000 feet (1,524 meters) of water, the well was further delineated by three sidetracks. The well is expected to be developed through the Mad Dog spar development or via a subsea tie-back.

In January 2009, project partners submitted a plan to the US Minerals Management Service, proposing to drill four exploratory wells with the CR Luigs semisub. With drilling procedures occurring in February 2009 through November 2009, the wells are scheduled to be drilled and temporarily abandoned.