BJ Process and Pipeline Services (BJ PPS) has announced that it has completed pipeline pre-commissioning services for the final segments of the West African Gas Pipeline (WAGP) system, on behalf of Willbros West Africa Inc, an Ascot Offshore Services Company.
One of the largest pipeline networks in the region, the WAGP system measures 678km or 421 miles and will gather natural gas from fields in the Escravos region of the Niger Delta, for delivery to customers in Ghana, Togo and Benin.
The pipeline system comprises the existing Escravos-Lagos pipeline, a new onshore pipeline in Nigeria, and a new offshore pipeline together with a recently built compressor station.
Willbros West Africa Inc. selected BJ PPS to prepare the new pipelines for commissioning and start-up, with BJ coordinating the delivery of all primary equipment to commence operations in just two weeks, based on the project's narrow timeframe. The group undertook a wide range of preparatory and pre-commissioning work, displacing more than 100,000 tonnes of seawater and other services including pipeline flooding, hydrostatic pressure testing and filling with nitrogen to make inert.
The scope of the WAGP system required BJ PPS to plan and manage several different phases, including operating the air equipment spread continuously for several weeks.
Lindsay Link, General Manager of BJ PPS, explained, “In addition to operations and management personnel, BJ PPS maintenance personnel were always onsite to ensure that the operation progressed smoothly. The overall success can be attributed to the combined expertise and commitment of everyone involved.”
“We are extremely pleased with the results, and look forward to working for Willbros West Africa in the future,” Link added.
WAPCo, the owner and operator of the pipeline transmission system, is a consortium consisting of partners Chevron, Shell, Nigerian National Petroleum Corporation (NNPC), Ghana's Volta River Authority (VRA). Societe Beninoise de Gaz (SoBeGaz), and Societe Togolaise de Gaz (SoToGaz).
The consortium’s Engineering and Construction Manager, David simons, enthused, “WAGP greatly appreciates the partnership with BJ PPS during the pipeline pre-commissioning phase of the project. In particular, BJ PPS are to be recognised for an exemplary drying programme during which the high levels of equipment uptime and dewpointing capability contributed to a reduced duration of critical path works. Well done to all concerned.”
BJ PPS managed the WAGP operation from its operations base in Port Harcourt, Nigeria, with support from its base in Aberdeen, Scotland. The project commenced in September and was completed in December 2007.
Displacing 100,000 tonnes of seawater
The offshore pipeline, which measures 20 inches in diameter and stretches from the Lagos Beach Compressor Station (LBCS) near Badagry, Nigeria, to Takoradi, Ghana, extends 568 km through water depths to 71m. BJ PPS removed more than 100,000 tonnes of seawater that filled the pipeline before drying it in accordance with strict parameters.
The BJ PPS project team designed a dewatering program using a train of six bi-directional pipeline pigs, with the discharged seawater routed offshore for safe disposal. This dewatering run was completed in less than 19 days and deemed successful when the pigs arrived conveying a clear change from water to air discharge.
To commence the air drying process, pressure was vented at Takoradi, in the same direction as the pigging run, with the offshore pipeline vented in just six days. Special care was taken to ensure all pressure was vented from the long line and that it was safe to remove the pig receiver. The final phase of the operation was to fill the pipeline with nitrogen so that it would be inert in preparation for commissioning with natural gas.
The new onshore pipeline measures 30 inches in diameter and runs 56 km from the Alagbado Tee connection on the Escravos-Lagos line to the LBCS. BJ PPS provided a full range of pre-commissioning services, including pipeline flooding, cleaning, gauging, hydrostatic pressure testing, dewatering, drying, and filling with nitrogen to make inert. BJ PPS overcame challenges associated with the project, including securing a supply of water to flood the pipeline (by pumping from the Atlantic Ocean) and moving equipment in difficult site conditions.