The Hoover-Diana field is a deepwater GOM oil and gas development located 160 miles (257 kilometers) east of Corpus Christi, Texas. ExxonMobil, operator, has a 66.7% vested interest; BP Amoco holds the remaining 33.3% interest.

The Hoover field, about 15 miles (24 kilometers) east of the Diana field, was discovered in 1997 on Alaminos Canyon Blocks 25 and 26. Discovered in 1990, Diana is located on East Breaks Blocks 945, 946, 988, and 989.

The fields, in 4,800 feet (1,463 meters) of water, have estimated combined recoverable reserves of 300 million barrels of oil equivalent. Through an integrated development initiative, both fields came on-stream in 2000 with development costs estimated at $1.2 billion.

Field Development

The integrated field development included wells on both fields connected to a Deep Draft Caisson Vessel platform (DDCV), located in 4,800 feet (1,463 meters) of water on the Hoover field. An industry first, the DDCV set the record for water depth and associated subsea development.

The semisubmersible Marine 700 was contracted from Marine Drilling to drill the Diana and Hoover wells. In The six Diana wells were connected through a subsea manifold and flowlines to the DDCV platform 15 miles (24 kilometers) away. With subsea trees on each well, hydrocarbons are transferred from the Hoover wells to the DDCV via vertical risers.

DDCV

The DDCV platform, with drilling and production facilities, is located on the Hoover field at Alaminos Canyon Block 25. In 1999, it was towed to its offshore location, then up righted; and production decks were installed. Aker Rauma Offshore was awarded the DDCV construction.

With a catenary-moored steel cylindrical hull, the 62,000-ton vertically floating vessel is 150 feet (46 meters) in diameter and 1,019 feet (311 meters) tall. The buoyed vessel has air-filled compartments in the upper portion of the hull and is ballasted with seawater in the bottom compartments. A 17,000-ton (15,422-tonne) hull section of the DDCV was fabricated at the Aker Gulf Marine fabrication yard in Corpus Christi, Texas. The second hull section was completed at Aker Mantyluoto in Pori, Finland. The two sections were combined at the US fabrication yard prior to its launch in the GOM.

A three-level deck houses separation, dehydration and treatment facilities for 100,000 bopd, 325 MMcf/d (9.20 MMcm/d), and up to 60,000 barrels of water per day, as well as a drilling rig. The platform's topsides were designed by Mustang Engineering and fabricated by Brown and Root Energy.

Twelve 7,100-foot-long (2,164-meter-long) anchor lines moor the vessel to the seafloor; each line consists of a chain and a spiral-strand wire rope. At the time, the 105-foot-long (32-meter-long), 275-ton (249-tonne) mooring piles were the largest ever installed on an oil and gas platform. Saipem using the Saipem S-7000 vessel installed the topsides, suction pilings, mooring lines, flowlines, steel catenary risers and export lines.

Pipelines

The DDCV does not have storage capabilities to store produced hydrocarbons, instead it pumps oil and gas onshore through pipelines. An 85-mile (137-kilometer) gas pipeline was constructed from the DDCV to the High Island Offshore System, which is an existing gas transmission system off the Louisiana coast. Also, an oil pipeline was built, which extends 150 miles (241 kilometers) to Freeport, Texas. These two pipelines were one of the longest in the GOM.

Commencing production in 2000, Hoover-Diana's current production averages more than 80,000 bopd and 200 MMcf/d (5.7 MMcm/d). The Hoover-Diana project received OTC's Distinguished Achievement Award for Companies, Organizations and Institutions in 2002.

Satellite Fields

The DDCV also ties satellite fields Madison and Marshall to its facility and were developed by three-well remote subsea developments. Both fields are situated about 7 miles (11 kilometers) from the vessel.

ExxonMobil discovered the Madison field, located in 4,900 feet (1,493 meters) of water, on June 25, 1998. The field is situated on Alaminos Canyon Block 24. The Marshall field, located on East Breaks Blocks 948 and 949 and in 4,300 feet (1,311 meters) of water, was discovered on July 30, 1998.

The fields commenced production in 2002.