Who Dat Field, Gulf of Mexico, United States of America

The Who Dat oil and gas field is located in the Mississippi Canyon (MC) blocks 503/504/547 of the Gulf of Mexico (GOM). It lies in a water depth of 945m. Estimated life of the field is 30 years.

LLOG Exploration is the operator of the field with a 67.5% working interest. First production is expected by 2012.

Discovery and geology of the Who Dat oil and gas field

The Who Dat field was discovered in December 2007 by the OCS-G 27277 Well A1 in the MC block 504. The well was drilled by Diamond Offshore's Ocean Victory semisubmersible drilling rig.

Two more wells were drilled in 2010 to further appraise the field by the Noble Lorris Bouzigard and Noble Amos Runner semisubmersible rigs. The additional wells expanded the field into blocks 503 and 547.

The Who Dat field is made up of ten stacked reservoirs of the Pliocene and Upper Miocene age. The reservoirs are located at a depth of 10,000-17,000ft with pressures ranging between 6,000-12,500psi.

The three wells drilled at the field have encountered more than 700ft of net pay in the reservoirs. The wells flowed at the rate of 10,000 barrels a day of oil and 60 million cubic feet a day of non-associated gas.

Oil and gas reserves at the Gulf of Mexico-based field

Who Dat is estimated to contain 100-300 million barrels of oil equivalent of which 70% is oil. The oil and gas reserves have low amount of wax and no asphaltene flocculation.

Field development using the Opti-Ex floating production system (FPS)

The field will be developed using semi-submersible Opti-Ex floating production system (FPS). The existing wells will be completed and additional wells will also be drilled.

These wells will be connected to a subsea system capable of handling up to 12 wells. Flexible risers will connect the wells to the Opti-Ex FPS.

The OPTI-EX FPS was acquired by LLOG for operations at the field. It has a production capacity of 60,000 barrels of oil a day (bopd), 150 million standard cubic feet of gas a day (mmscfd) and 40,000 barrels of water a day (bwpd).

The facility was installed at the field in July 2011. It has been specifically designed for operation in the GOM at a cost of $400m. The FPS is designed to withstand a 1,000-year storm.

The OPTI-EX FPS is held onto the seafloor by 12 mooring lines connected to 80ft suction pile anchors. The hull of the FPS is a deep draft ring-pontoon. The FPS is designed in such a way that it can be modified quickly and used at other fields at the end of its operations there.

Subsea systems and exportation

The subsea system for the field includes ten miles of 6in flowlines, six risers, nine jumpers and jumper tie-ins, three manifolds and other equipment.

Oil produced at the field will be transported through a 19-mile long 14in diameter export oil pipeline which will connect to the Mars pipeline system. The pipeline will carry the oil to Shell production facilities onshore where it will be processed.

The gas will be exported through a 17-mile long 10in diameter gas pipeline which will connect with the Independence Trail pipeline operated by Enterprise Field Services.

Contracts awarded to international companies

Exmar Offshore Company was responsible for designing, constructing and installing the OPTI-EX FPS.

Mustang Engineering was contracted to carry out pre-FEED and FEED studies, detailed engineering and design, procurement services and vendor inspections for the topsides of the FPS.

Samsung Heavy Industries constructed the hull of the FPS in South Korea. The topsides of the FPS were fabricated by Kiewit Offshore Services in Texas. Dockwise was contracted by Exmar to transport the FPS hull from South Korea to Texas for integrating with the topsides.

Delmar was contracted to provide engineering, design, fabrication and installation services for the mooring system of the OPTI-EX FPS. Baker Hughes provided drilling and well completion services for the field.

LLOG contracted Expro to provide subsea and slickline services for the field. FMC Technologies was awarded a $40m contract to supply seven subsea production trees and control systems for the field.

Global Industries has been contracted to install the oil and gas pipelines, risers, flowlines, manifolds and other equipment of the subsea production system.