Block NC-41, Mediterranean Sea
The Bouri field lies in water depths between 145m and 183m, offshore the Libyan coast, in the Mediterranean Sea. The field is located in the block NC-41, which contains one oil reservoir and two gas reservoirs.
The field is operated by ENI (30%) in partnership with state-owned National Oil Corporation (70%), with the two partners jointly setting up Mellitah Oil and Gas Company to manage the field.
Production from the field started in 1988 through two production platforms and Sloug floating storage and offloading (FSO) vessel. In 2012 it was announced that the existing FSO will be replaced by a new FSO named Gaza. Built at a cost of $424.78m, the new vessel reached the Libyan field in May 2016.
The Bouri oil reservoir is considered to be the biggest of its kind in the Mediterranean region and its development represented Libya’s first subsea project.
Consisting of 38 wells, the field was developed using two platforms, a central processing platform (DP4) and a satellite platform (DP3) to produce 150,000bopd of crude oil for export.
The two platforms are located four miles (6.5km) apart with the DP3 platform secured to the central facility, which is moored to the FSO vessel.
Degassing and dehydration of the crude oil is performed by the field’s facilities with the treated oil being sent to the FSO for further processing. The oil is transported through two 16in sea lines to the FSO, which is secured to a single point mooring (SPM) system. A floating hose is used to ship the processed oil to a shuttle tanker for export.
The replacement of the existing Sloug FSO with the Gaza FSO in the Bouri field involved detailed design, engineering, procurement, fabrication, construction, installation and commissioning of the associated offshore facilities.
The work on the field’s offshore facilities comprised laying of a new subsea pipeline tied-in to DP4 platform and the new FSO, a single point mooring system, and separate power cables connecting DP4 to the new FSO vessel.
The new subsea pipeline includes the loading line to the new FSO from the platform and all other components associated with it. It is further segmented into three divisions, including a tie-in to the DP4 platform, as well as new risers, a pipeline connecting the DP4 platform to the new SPM, and a tie-in joining the subsea pipeline to the pipeline end manifold.
The new SPM system will comprise an external turret mooring system for the new vessel, a system to transfer crude oil from the pipeline and the pipeline end manifold, and a pile system for securing the vessel’s mooring legs.
The Gaza FSO is an ultra-large vessel with a length of 324m and a width of 51m. It is equivalent to approximately 3.5 football stadiums and has the capacity of 1.5 million barrels of crude oil storage. The hull size of the FSO is approximately 210,000DWT.
STX Offshore & Shipbuilding was selected by Mellitah Oil and Gas Company to construct the FSO vessel along with the designing, manufacturing and installation of the subsea pipeline system. The company also conducted test-runs for the offshore facilities.
EMAS AMC was sub-contracted by STX O&S to provide project management and detailed engineering, construction, procurement, construction, installation and commissioning services. The company will work on the FSO turret, moorings, subsea facilities and associated operations.
EMAS will also provide services on the subsea facilities, including the design, procurement, transportation and installation of nine leg mooring systems, three flexible risers and flowlines, as well as pre-commissioning activities.
A contract was awarded to First Subsea for the provision of diverless bend stiffener connectors for risers and umbilicals. A three-year contract was awarded to Houlder for project management services regarding the design, construction, delivery and hook-up of the new vessel and related infrastructure.
Upsyde International was also contracted to provide project management services for the replacement project. For post-lay trenching and backfilling activities, James Fisher Subsea Excavation was selected.
Medserv received two logistics contracts including one from STX and the other from EMAS AMC, which will be serviced from the company’s Malta Base facilities and their Libyan Branch.
Mooring, tether chains and shackles will be supplied by Sanmar Chain International to EMAS AMC. Rana Diving has been selected by EMAS to provide diving services during the installation and hook-up using its mobile saturation diving system AF01.
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