A. Laine, A. Goffart
Total Oil Marine plc
Aberdeen
A strategy of maximum onshore work saved Total Oil Marine plc at least 20 million ($32 million) on construction and commissioning of its Dunbar platform, a major development on the U.K. continental shelf.
The project team's objective at the beginning of detail engineering in October 1991 was to start producing oil and gas before Dec. 31, 1994, a project duration of only 38 months.
Minimal and fast offshore hookup and commissioning were some of the many challenges. The target was to spend less than 250,000 man-hr offshore for the 900-ton topsides and finish the work in less than 17 weeks, including 3 weeks for connecting a tender support vessel (TSV).
This objective, based on experiences with integrated decks at that time, was seen to be ambitious, not to say unrealistic, by some in the industry. But at the beginning of October 1994, the Dunbar project team had done much better.
The 600-bed Port Regency flotel was disconnected on Sept. 5, 1994, after less than 10 weeks, and less than 150,000 man-hr had been spent by AOC International Ltd. (AOIC), which was in charge of hookup and commissioning assistance. The platform commissioning activities were substantially complete as the Certificate of Fitness for Habitation was delivered on Aug. 26, 1994.
The Certificate of Fitness for Drilling was delivered on Sept. 25, 1994, after mooring and commissioning the TSV, and the platform was handed over to the operations group.
Dunbar - Key Facts and Figures Chart (65882 bytes)
ONSHORE WORK
The Dunbar installation set a record in the North Sea because of the correct strategy defined by Total at the outset of the project and the ambitious intermediate goals and good project control throughout.
Past and recent integrated deck experiences in the North Sea have shown that completing fabrication onshore is difficult for a fast-track project. In the past, a substantial amount of work has been either transferred or, even worse, discovered offshore. This adversely affects project cost and schedule. Throughout the project, Total was determined to take all necessary actions to avoid offshore work.
The major contributing factors that led Total to succeed on Dunbar included:
- Single-lift topsides
- High degree of onshore fabrication
- High degree of onshore commissioning
- Good weather
- Smooth installation
- Thorough onshore preparation of the offshore campaign
- Motivation of the hookup contractor.
Of these, the first three were essential. A single topsides lift reduced the design hookup scope, and up to 80% of the commissioning was done in the yard. Onshore commissioning allowed for extensive testing of utility, drilling, and process systems and for correcting design shortcomings before going offshore.
From the beginning of the hookup, it was also possible to use most of the permanent platform utilities.
ATTENTION TO SCHEDULE
Day-to-day attention from day one is required to obtain minimum work carry-over to offshore.
One of the most challenging objectives for the Dunbar team was to attain a high degree of completion onshore in fabricating the 9,000-ton deck. Failure would have dramatically jeopardized the overall project cost and the schedule.
Total wanted 100% onshore completion within a 22 month fabrication/commissioning program. The chances of failure were numerous and success demanded a high level of work in all aspects of fabrication.
Day-to-day attention by all concerned parties was required long before fabrication began. AMEC Engineering Ltd., in charge of detailed design, adapted its engineering effort to the fabrication requirements. It was successful in delivering design information, main equipment, and bulk materials on time.
UiE Scotland Ltd., awarded the fabrication of the Dunbar topsides, must be credited for the performance achieved.
Total's strategy was to proceed as fast and safe as practicable, identify and quantify the scope on a continuous basis, work according to the initial plan, and mobilize manpower accordingly. In practice, this meant not to waste time in the easy part of structural fabrication, so that enough time remained for the more complex work of outfitting, commissioning, and completion.
COORDINATION
Total's strategy included using its own personnel for managing and executing the commissioning. This strategy is not favored by everyone in the industry but has been proven and used by Total for many years.
On Dunbar, it provided the opportunity to integrate and familiarize future operations and drilling crews in the yard, a critical step for a quick offshore handover and for implementing a minimum manning concept.
Total developed its own methodology called Opercom together with necessary computer applications for management of precommissioning and commissioning activities.
During the year preceding their move to the yard, the commissioning team created a long and detailed plan at the engineering office. This preparation identified the scope of work, a logical sequence of activities, and the temporary personnel and equipment required to maximize onshore commissioning. In fact, it became clear very early on that up to 80% of all commissioning could be done in the yard. Detailed plans were prepared to meet this objective.
One major obstacle to overcome was the interface between commissioning and fabrication. The schedule required about a 6-month overlap between the two activities. To ensure safety and reduce disruption while energizing the various systems, an extreme level of preparation and coordination was needed in the limited space provided for both fabrication and commissioning activities.
By defining a comprehensive set of priorities in the early stages of the project and by interfacing commissioning and fabrication at a very low level, Total succeeded in commissioning 76% of Dunbar onshore.
PREPARATION
Thorough onshore preparation reduced offshore man-hours. Only 12 months elapsed between awarding the hookup contract to AOCI and contract closeout.
Although the last 6 months on the fabrication site were somewhat hectic, with onshore activities in a race against time, it did not distract the Total project team from careful preparation of the offshore operations.
The imperative put upon the Total/AOCI hookup team was to start the offshore work with an accurately defined scope and the relevant planning in place.
All possibilities for reducing the work offshore were studied. The strategy was that if work could be done onshore, there was no reason not to do it. There was a continuous drive against the usual "laxity" of uncontrolled transfer of work offshore.
On the first day offshore, all job cards were available, all materials were allocated and, wherever possible, stored on the platform next to the work area. Temporary air and power distribution was operational. Scaffolding and access had been arranged wherever possible, and all key players from foreman level upwards were familiar with the planned work.
HANDOVER
Handover to operations and drilling teams was completed after less than 3 months of offshore hookup and commissioning.
Because of the onshore commissioning, all essential platform life support was operational a few days after deck installation. This was critical for a quick hookup and commissioning.
This also allowed the offshore team to arrive offshore with the main functions already tested in the yard. Control system simulators and temporary generators or temporary utilities were used for proving out most interfaces with Total's Alwyn North platform, the tender support vessel Sedco 706, and Total's Ellen subsea wells.
As soon as commissioning resumed offshore, hand over to the operations team started progressively of the utility systems commissioned at the yard. Overall, the hand-over process remained trouble-free because most end users were involved in the commissioning activities in the yard.
During September the Port Regency departed and the Sedco 706 arrived, limiting the personnel on board to a maximum 159 from 350 previously.
But because of the team effort and the detailed preparation plans, the target dates were maintained and the platform was ready for drilling on Sept. 25, 5 weeks ahead of schedule.
SAFETY
Not only overall strategy, but also close attention to detail and positive co-operation rendered Dunbar a success.
However, a fast-track program and efficiency, would be meaningless if safety was put at risk.
A comprehensive set of procedures developed by Total, as operational AOCI safety management system and an efficient collaboration between both teams allowed a first in the North Sea-no lost time accident recorded during what is, after all, a substantial hookup.
This is undoubtedly one of many aspects that Total and AOCI are proud to be associated with.
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