The Bahr Essalam Pipelines and the Sabratha Platform are located in the NC-41 field, 110km off the Libyan coast in approximately 220m water depth. Gas from the subsea production wells/pipeline manifold structures passes through a 22" gas and 8" insulated pipe to the Sabratha Platform for initial processing. Products are then exported from the production platform to the Mellitah Onshore Facility via a 107km 36" gas pipeline and a 10" condensate pipeline. Final processed gas is compressed and sent to Europe via the Greenstream pipeline. A 4" service line was also included in the pre-commissioning package.
The work scope was divided into two phases, the first one comprising the simultaneous onshore and offshore flooding, cleaning, gauging and initial hydrotest of all the lines. The second phase involved testing of the pipelines after final tie-ins, including further hydrotesting, dewatering, air drying of the export pipelines, MEG swabbing of the infield pipelines, and the nitrogen purging and packing of all the pipelines.
Given the difficulties in sourcing a reliable supply of cryogenic nitrogen in Libya, Weatherford's membrane nitrogen technology was ideally suited to this project. Based on the Sabratha platform, the Weatherford P&SS membrane nitrogen units take up much less space than nitrogen tanks, and provided an unlimited source of nitrogen for purging and packing of the export and interfield pipelines.
Part of Weatherford's temporary air compression station (TACS), previously deployed for Saipem during the Greenstream project, was used offshore for the dewatering operations, and another part of the TACS was used onshore at the Mellitah terminal for the dewatering of the 36" and 10" export pipelines.
With an ever-growing portfolio of contract awards from Saipem and other contractors globally, Weatherford P&SS is fast becoming a market leader in the provision of pipeline pre-commissioning services. Weatherford's NC-41 Project Manager said: "We are delighted to have worked again with one of our major clients, Saipem, with a successful conclusion to the project.
In addition, on the back of these pre-commissioning operations, Weatherford LAMB Libya has been awarded a smaller value contract, for pigging services during the well and pipelines commissioning operations (Sabratha), commencing around September 2005.
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