Appomattox Deepwater Development, US Gulf of Mexico

The Appomattox Deepwater Development project involves the initial development of the Appomattox and Vicksburg deepwater fields, located approximately 129km (80 miles) offshore Louisiana, US, at a water depth of about 2,255m (7,400ft).

The Appomattox field is situated in Mississippi Canyon block 392 and straddles Blocks 391 and 348, whereas the Vicksburg discovery is situated in Mississippi Canyon block 393.

The final investment decision (FID) for the project was taken in July 2015, leading to the start of construction. Production from the project began in May 2019.

Appomattox project is a joint venture between Shell (79%, operator) and CNOOC Petroleum Offshore USA (21%), a wholly-owned subsidiary of CNOOC. Peak production from the fields is estimated to be approximately 175,000 barrels of oil equivalent (boe) a day.

Discovery and reserves

The Appomatox field was discovered in March 2010 by drilling the discovery well at Mississippi Canyon block 392. The well was drilled to a depth of 7,643m (25,077ft) and encountered approximately 162m (530ft) of oil pay.

It was followed by the drilling of an appraisal sidetrack well in the same year to a depth of 7,910m (25,950ft). The well encountered approximately 116m (380ft) of oil pay. The field was further appraised in February 2012 by drilling an appraisal well in Mississippi Canyon block 348, at a water depth of approximately 7,257ft and to a total depth of 25,851ft. The well encountered approximately 150ft of oil pay.

The Vicksburg field was discovered in July 2013 by a discovery well at Mississippi Canyon Block 393 that was drilled at a water depth of 2,269m (7,446ft), to a total depth of 8,042m (26,385ft). The discovery well encountered more than 152m (500ft) of net oil pay.

The two fields are together estimated to hold recoverable reserves amounting to 650 million metric barrels of oil equivalent (MMboe) approximately.

Geology of the Gulf of Mexico deepwater fields

The reservoirs of the Appomattox and Vicksburg fields are located in Norphlet play, a geological formation of the Jurassic period (between 150 and 200 million years ago) that extends from onshore to the deep waters, characterised by high pressures and well temperatures.

The third major discovery in the Norphlet play, named Rydberg, located within MC Block 525, was made in July 2014. Another oil discovery was made in the Gettysburg prospect with the Gettysburg W exploratory well, located in the Desoto Canyon Block 398, in the fourth quarter of 2014. The two prospects are located approximately 16km (ten miles) from the Appomattox field.

Appomattox Deepwater Development project details

The development of the Appomattox project included the installation of a semi-submersible, four-column production host platform, a subsea system featuring six drill centres, and the drilling of 15 production wells and five water injection wells. The infrastructure at the project site has a design capacity ranging between 120,000boe/d and 200,000boe/d.

The new production platform is Shell’s eighth and biggest floating platform in the Gulf of Mexico. Shell was able to reduce the project cost by approximately 20%, based on the experience gained from the development of the previous four-column production platforms in the Gulf of Mexico such as the Olympus tension leg platform.

Crude oil produced from the project is conveyed via a new 90mi (145km)-long and 24in-diameter oil export pipeline, named the Mattox Pipeline, to an existing offshore structure in the South Pass area and further supplied onshore using the existing Proteus pipeline system. Owned and operated by Shell Pipeline Company, the Mattox Pipeline has a 300 thousand barrels per day (Mbpd) capacity. It features pre-installed subsea connection points to accommodate future interconnections.

The Gettysburg and Rydberg prospects are currently being reviewed for a possible connection to the Appomattox infrastructure, which will further increase the total estimated discovered resources in the area to more than 800Mmboe.

Appomattox’s living quarters details

Appomattox production platform includes a living quarters module, which is a 40,000ft² building with approximately 50 bedrooms, facility for athletics, conference rooms, professional kitchen, dining room, laboratory spaces and several storage systems.

Contractors involved

In 2013, Delmar provided the mooring design engineering services for the floating platform, which included global mooring analysis verification using its nonlinear polyester stiffness method and mooring analysis software. Some of the exploratory and appraisal wells in the area were drilled employing the Deepwater Nautilus rig.

In September 2015, TechnipFMC was contracted to supply the high-pressure/high-temperature (HP/HT) full-field subsea solution for the project, which included wellheads, 18 subsea trees, four production manifolds, pipeline end termination (PLET) and jumper systems, subsea and topsides controls and associated tooling suites.

Samsung Heavy Industries delivered the hull for the Appomattox platform in 2017. Heerema Marine Contractors was responsible for the transportation and installation of the floating production system (FPS) for the project. The company subcontracted BMT for marine simulation studies, supporting the installation of Appomattox FPS.

The topside and hull of Appomattox FPS were integrated at Kiewit Offshore Services, Ingleside, Texas. Broadmoor constructed the living quarters module for the project.

Other contractors involved in the project were Allseas, Oceaneering, Crowley Maritime, Delmar Systems and Williams Partners.