April 2016, Vol. 243, No. 4


Shell Works to Develop Deepwater Gulf Fields

Turritella FPSO for Shell’s Stones field.

With one ultra deepwater floating production, storage and offloading (FPSO) vessel on location and scheduled to come onstream before yearend and a second semi-submersible host platform under construction, Shell is gearing up to increase its deepwater production in the Gulf of Mexico.

Construction was recently completed on the Turritella FPSO for the Stones field, an ultra deep water oil and gas development that will host the deepest production facility in the world. The FPSO for the Stones field set sail from Singapore in November, en route to its final destination in Block 508 in the Walker Ridge area of the Gulf of Mexico, 322 km off the coast of New Orleans. The ultra-deepwater project lies in a water depth of 2,926 meters.

The FPSO is a typical generation two design with a processing facility capacity of 60,000 bopd and 15 MMscf/d of gas treatment and export. The hull will be able to store 800,000 bbls of crude oil that will be transported to U.S. refineries. Gas will be transported via pipeline.

Stones will be Shell’s first FPSO in the Gulf of Mexico, but not globally. Shell is using FPSOs at other locations including the Parque das Conchas (BC-10) project off Brazil with co-owners ONGC and Qatar Petroleum International.

As to construction, SBM Offshore signed contracts with Shell Offshore Inc. in 2013 to supply and lease an FPSO for the Stones project in the Gulf. The contracts include an initial period of 10 years with future extension options up to 20 years. The FPSO for the Stones field is a converted Suezmax tanker.

The Stones FPSO will use a special type of flexible pipe that carries oil and gas to the FPSO for processing and transport, known as lazy wave risers. These were pioneered by Shell and are made of steel with extra buoyancy. An arch bend absorbs the motion of the FPSO and boosts riser performance at extreme depths.

It will also contain a turret with a detachable buoy that allows the vessel to turn in place during normal weather conditions. If a heavy storm approaches, it can disconnect its mooring lines and risers from the well system and sail to a safe area. Shell says this will be the first time a turret and disconnectable buoy is configured with lazy wave risers in order to unlock oil production in ultra-deepwaters.

Shell’s Stones field is estimated to contain over 2 billion boe. Plans call for a phased development scheme starting with two subsea production wells tied back to the FPSO vessel and host facility. In later phases six more wells will be added with multiphase pumping. The reservoir depth is 26,500 feet below sea level and 17,000 feet below the mud line. Production is expected later this year.

Appomattox Development

Computer generated image of Appomattox Development.
Computer generated image of Appomattox Development.

Construction is also underway for Appomattox, a deepwater oil and gas development that will be Shell’s eighth and largest floating platform in the Gulf. The project is located in 7,200 feet in the Gulf 80 miles from the nearest shoreline in Louisiana in the Mississippi Canyon and Desoto Canyon areas, an area where Shell is the first to achieve commercial discoveries.

Shell announced a final investment decision in July for the development that will initially produce from the Appomattox and Vicksburg fields, with average peak production estimated at 175,000 boe/d. The platform and the Appomattox and Vicksburg fields will be owned by Shell (79%) and Nexen Petroleum Offshore U.S.A. Inc. (21%), a wholly owned subsidiary of CNOOC Limited.

The project includes capital for development of 650 MMboe resources at Appomattox and Vicksburg, with startup estimated around 2020. The development of Shell’s recent nearby discoveries at the Gettysburg and Rydberg prospects is under review. These could become additional, high-value tiebacks to Appomattox, bringing total estimated discovered resources to over 800 MMboe.

Shell Pipeline Co. LP made a final investment decision on the Mattox Pipeline, a 24-inch corridor pipeline that will transport oil from the Appomattox host to an offshore structure in the South Pass area and then connect onshore via pipeline.

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