Design and Installation of the Malmapaya Depletion Compression Platform

Leon Lorenti, Andrew J. Grime, Brian Raine

    Research output: Chapter in Book/Conference paperConference paper

    Abstract

    The Malampaya Depletion Compression Platform (DCP) was conceived by Shell Philippines Exploration B.V. (SPEX) to provide additional gas compression to account for the future expected decline in well pressure from the Malampaya field. The Malampaya project is very important to the ongoing prosperity of the Philippines, with the exported gas feeding three power stations which provide up to 45% of the power needs of Luzon, the largest and most populous island in the Philippines.

    The DCP consists of a sealed barge structure which is rigidly connected to four cylindrical legs, each of which is supported on individual strut-linked hexagonal pad footings. The DCP arrangement uses cylindrical rather than truss legs and the base comprised a series of linked pad footings rather than a skirted baseplate. The leg configuration was selected in an attempt to simplify the leg fabrication; whilst the use of pad footings was a result of the site geotechnical conditions.

    One of the key structural innovations on the project was to design a barge to leg connection which could accommodate both the required vertical movement of the circular leg during installation, as well as form a rigid moment connection at the final design level of the barge without excessive offshore works.

    One of the key geotechnical innovations was to eliminate the need for a dedicated scour protection layer around the footings, yielding savings in procurement and offshore placement. This was achieved by selecting a foundation fill material capable of resisting self-scour in the 100-year return period cyclonic storm. The use of this larger sized material was agreed in advance with potential offshore Contractors to ensure that the required surface tolerances could be readily achieved.

    Offshore work prior to the arrival of the DCP consisted of seabed excavation to remove the in-situ carbonate sand and reef limestone, and replacement with the engineered rock fill to form a sufficiently level surface for placement of each of the four pad footings.

    Installation of the DCP at the Malampaya site commenced after a 3 day wet-tow from the fabrication yard in Subic Bay. Base lowering commenced on the morning of 12 February 2015, with touchdown occurring on the seabed some 26 hours later. Barge raising commenced immediately thereafter with the barge clearing the water around midday on 13 February 2015. Barge raising to the final elevation was completed in the early hours of 14 February 2015, less than 2 days after initial touchdown.

    As well as providing a general overview, this paper will describe some of the geotechnical and structural innnovations which ensured a successful outcome of the project.
    Original languageEnglish
    Title of host publicationProceedings of the 48th International Offshore Technology Conference
    DOIs
    Publication statusPublished - 2016

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