14 October 2003

Nigeria: Shell Commissions Offshore Gas Pipelines

Lagos — As part of its determination to stop gas flaring, Shell Petroleum Development Company (SPDC) has commissioned two sets of pipelines in the Offshore Gas Gathering System (OGGS), the 32-inch 265km trunkline and 24-inch 90km Forcados Spurline.

The whole pipeline system has a total capacity of 1200 million standard cubic of gas and will convey associated gas from SPDC's offshore acreage (EA Bonga, H and K Blocks) as well as supply gas from Western operations (Focardos Yokri and South Forcados) and deliver to NLNG at Bonga.

According to Shell's lead Engineer, Innocent Ukejianya: "OGGS is a key infrastructure element in Shell's expansion plans and consists of a user platform near the EA field, sub-sea at H and K locations slug catcher, pressure control and metering facilities and Central Production Coordinating Centres in Port Harcourt and Warri."

It was designed to coat the line pipe locally for corrosion and pipeline stability, but no substitute facilities were available in Nigeria when it was awarded to efficiently undertake the huge requirement for over 400km of line pipes.

The 265-km off-shore pipeline was laid in three different sections because of various water levels along the pipeline corridors. A semi-submersible lay barge B-200, with 300 persons on board laid the deeper end.

"Given the different sections of pipeline, there was need to tie the shallow section to the rest of the pipeline mid-stream. The operation is weather-sensitive and HSE critical and therefore had to be carried out at a particular period to coincide with calm sea conditions.

This above water-tie-in (AWT) operation for the trunkline was successfully performed in the month of February," Innocent explained. The final section of the 32-inch truntline passes through Bonny thick Mangrove Swamp land with 3 major pipeline crossing and 3 mangrove crossings. Mechanical completion of the 7.8km onshore 32-inch trunkline was successfully completed in August.

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