Abstract

The development of the Terang and Sirasun fields is expected to be the largest subsea project in Indonesia and the first to be carried out without the use of divers. These gas fields are in water depths varying from 100 to 300 metres, located some 140 km north of Bali and approximately 120 km southwest of the existing production facilities on Pagerungan Island.

Definition phase engineering was carried out in 1995/96 addressing a number of key technical issues, particularly relating to the subsea facilities:

• Subsea Field Layout: Conventional subsea manifolds have been eliminated in favour of direct tie-ins from each well into the main gathering line. This method significantly reduces the total length of flowlines and the tie-in porches are small enough to be installed with the main gathering line.

• Christmas Tree Design: Horizontal subsea Christmas trees have been specified and the number of valves kept to a minimum. This reduces cost and avoids the requirement for specialized installation and workover tooling.

• Control System Configuration: The electrohydraulic multiplex control system has been carefully optimized for maximum reliability and minimum cost. The use of signal-on-power technology halves the number of electrical connections.

• Installation and Maintenance Philosophy: The current and predicted vessel and equipment capability within the Southeast Area was reviewed in detail to ensure the field scenario developed was compatible with readily available vessels. The use of remotely operated vehicles has been specified for all major intervention tasks including the installation of infield flowlines and umbilicals.

The result is a cost effective subsea development scheme which makes appropriate use of technology and experience from similar field developments elsewhere in the world while considering the special conditions which apply here in Indonesia.