AMOG Wins Engineers Australia Award of Excellence

AMOG has been awarded the Engineers Australia 2011 Award of Excellence for Infrastructure projects over $20 Million. The award recognises AMOG's involvement in the West Seno Mooring Refurbishment Project.

When the mooring for Asia’s first deep water hydrocarbon development reached the end of its life, earlier than expected, AMOG stepped in to replace it. In a world first, the mooring of an on-stream production facility in 1000m water depth was redesigned, upgraded and replaced; without interruption to operations. Demonstrating Australian engineers have the smarts to support a major oil company from brainstorming through to offshore trouble shooting, AMOG designed, documented, specified and supervised the successful refurbishment, giving the facilities mooring another 20 years’ operation and adding vital knowledge to the engineering community from a JIP and research activities.

This is AMOG's Second Engineers Australia Award for Excellence, having won in 1995, the only other year AMOG has entered the competition.

Project Summary

AMOG was lead consultant for a major refurbishment to the Chevron Indonesia West Seno offshore oil facility in the Makassar Strait near East Kalimantan. The refurbishment ran over 2½ years at a total cost of approximately $70 million. The facility is a major asset within Indonesia's hydrocarbon production infrastructure and the first deep water development in Asia.

This deep water (1,000m) facility began production in 2003. It consists of subsea wells tied into a well head Tension Leg Platform (TLP), with an adjacent Drill Tender Vessel (DTV), with jumper risers across to an oil processing Floating Production Unit (FPU) which is in turn connected by Steel Catenary Risers (SCR) to an export pipeline.

The FPU moorings had experienced higher than anticipated corrosion, dramatically reducing their projected life. AMOG was engaged to design a replacement mooring system for the facility to better resist the warmer tropical waters, to be installed without interrupting production or taking the FPU off station and whilst keeping the FPU within the tight offset limits of the SCRs. AMOG has not been able to identify a precedent worldwide project of this type.

The existing mooring was assessed to identify the current corrosion damage and remaining life of the mooring legs to determine the available time to execute the replacement. This assessment was undertaken using leading edge corrosion models developed within an AMOG-lead Joint Industry Project (JIP) SCORCH (Sea water Corrosion Of Rope and CHains).

AMOG developed a sophisticated hydrodynamic numerical model of the platforms and mooring systems and validated these against the original design calculations. This model was then used to develop a replacement mooring system that replicated the performance characteristics of the original mooring, but adopted a modified geometry to allow installation with the confines of the existing mooring still in place and using different components with better tropical water corrosion resistance. The design included extensive squall loading evaluation; not accounted for in the original design, and accommodated the asymmetric mooring load deflection curves that resulted from the the uneven seabed slope.

AMOG developed procedures for the mooring change out, considering simultaneous operations (SIMOPS) with the adjacent TLP and DTV, maintaining FPU excursions within limits to prevent SCR damage and developed mitigation measures for safety and project risks based on a thorough risk assessment.

AMOG prepared specifications and tender packages for the refurbishment works, performed the design of suction pile anchors for the replacement mooring, identified and liaised with potential component suppliers, prepared CAPEX estimates and installation schedules, and liaised with the classification society to achieve design acceptance.

Finally, AMOG provided on-site and shore-based technical support throughout the installation, including rapid evaluation of necessary design changes to accept variances in as-found site conditions during the course of installation.

This infrastructure refurbishment was achieved without reportable injuries, whilst maintaining the high pollution control standards of the development, and without interrupting production. Samples of the corroded mooring chain and wire were recovered for study as part of the SCORCH JIP into mooring corrosion, which aims to develop updated design guidance for mooring system component corrosion.

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