Abstract

The West Natuna Sea gas development called for the delivery of 325MMscfd of natural gas from Indonesia to Singapore via a 500km subsea pipeline. To deliver Pertamina - Conoco Indonesia Inc. Ltd.'s part of the contracted gas volumes required production and compression of associated gas from Belida and non-associated gas from new reservoirs over a wide area. As reserves become depleted and new fields are brought on stream, the compression facilities are to be relocatable.

This paper describes the evaluation process that led to the selection of a new-build self-installing steel gravity platform. This is believed to be the first major production platform to be designed from the outset for ease of re-location.

The development of the suction gravity base design, the jacking system employed and the offshore installation of the platform are described.

Background

The South Natuna Sea Block B Production Sharing Contract (PSC) is located in the West Natuna Sea area approximately 1000km North of Jakarta and 360km North East of Singapore. Block B exploration started in 1968, and while the initial focus was on finding oil, in the course of exploring for oil, several gas fields in the range of 70 to 300 BCF were discovered.

Efforts began in 1985 to commercialize this gas and, after extensive studies, it was concluded that the most attractive way to recover the value of these gas reserves was to adopt a phased development approach. The commerciality of this approach was made possible by Pertamina, Indonesia's national oil and gas company with its three West Natuna Sea production sharing contractors joining forces to market gas from Block A and Kakap Block together with Block B. Discussions began in earnest in early 1997 culminating in the April 1999 execution of a Gas Sales Agreement with Singapore.

The first step in meeting the gas sales commitments was the construction of the gas export trunkline from the West Natuna Sea to Jurong Island in Singapore, known as the West Natuna Transportation System (WNTS). The pipelaying for WNTS started in January 2000, and the system was successfully commissioned in January 2001.

For the Conoco operated Block B another important step was the design, construction and installation of a Movable Offshore Gas Production Unit (MOgPU), to provide flexibility in the development of scattered pockets of dry gas located over a 1600kmÂ2 area in water depths ranging from 70 to 100m.

What is a MOgPU?

The MOgPU acronym is simply an extension to the common industry designation "MOPU" meaning Movable Offshore Production Unit. The lower case "g" was added to recognize the specific application of the West Natuna MOPU as a gas processing unit, not to create a new class of production units. The Hang Tuah MOgPU provides all the benefits of a bottom-founded structure with the ability to be relocated to other areas of the Natuna Sea any time during its 25-year design life.

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