Challenges & Solutions
The Wandoo project brought with it both obvious and unforeseen challenges requiring innovative solutions.
The first challenge was to ensure that the project was delivered ahead of time, and under budget. The team was seeking an extraordinary result in all areas. This was the reason for selecting the Alliance approach of project delivery. The alliance team had promised delivery of the project for $375m in twenty seven months when industry standard was around thirty six to forty two months for an equivalent facility. The alliance had to convert what they had promised into results. A synergy was built up between design, construction, installation and production operation functional groups by having them all work as one team. Investments in training techniques to assist cooperative working and technology played a part in the early plans.
An early commitment was made to invest $1.6m in the three-dimensional CAD equipment used for modelling the topside design. This decision greatly assisted the team by eliminating many of the anticipated obstacles whilst providing a quick understanding of the impacts that design changes would have on the structure.
It was critical that the various components such as the CGS and the topside were constructed and transported in the required time frame so that the ‘mating’ of the two at the Wandoo oilfield could take place. This involved careful planning around weather patterns, design and construction of the different elements, and emergency response management and teamwork in the alliance when problems arose.
Excavation of the casting basin commenced whilst the CGS design development continued. Excavation had proceeded smoothly to a depth of seven metres below sea level by late April 1995, when a series of seepages through the sea bund appeared.
These were associated with a zone of weathered limestone and over a short period the flows increased rapidly culminating in a breach of the seawall early on Saturday 29 April 1995. The breach occurred progressively over a 40 metre length of the sea bund and was determined to be "piping" within a layer of weathered limestone below the cut-off wall. The alliance principle of "no blame" was tested for the first time and, by co-operation and replanning of the base construction, the time loss was restricted to three weeks. While the incident delayed progress, it demonstrated a major benefit of the Alliance approach, convincing the team of the greater possibilities of the Alliance approach. Under a traditional contracting arrangement, delays of up to many months were predictable. This set up the alliance to manage future problems that arose throughout the course of the project. Each problem was managed in the same 'no blame' way.
A second example of the Alliance in operation related to decisions regarding the amount of crude oil storage provided in the structure. Over the life of the field the demurrage cost to the client of an oil tanker sitting at the oilfield waiting for oil to be loaded is enormous. This has to be balanced by the optimum parcel size and frequency of tankers needed to offload the oil. Storage is provided in the concrete structure. During the interim alliance the decision was taken by the client to limit storage to 300,000 barrels. Later information concluded this was sub-optimal. Although CGS construction had commenced, innovation by the design and construction team of the CGS enabled a late increase of storage, from 300,000 to 400,000 barrels – an increase of 33%, by converting trim tanks and open cells into oil storage compartments. Flexibility in design and the collaborative effort of all parties achieved this, during construction without disruption to the overall construction programme. This resulted in a significant benefit to the client.
A final example of how the Alliance worked occurred during the tow of the CGS to the field. Despite the best advice from weather experts predicting fine weather, the structure was hit by a storm two days into the tow. The storm was severe and resulted in one of the tow ropes snapping and the structure drifting backwards towards the West Australian coast. This posed serious risks to the structure and raised the possibility of grounding the structure on the shore line. Emergency meetings were held in the middle of the night with the alliance team considering whether to sink the structure where it was, losing it altogether at an enormous cost returning it to shallow water closer to shore so that it could be recovered again once the storm had passed or attaching a tow rope again and continuing on with the program of towing the CGS out to sea. The alliance team decided to re-attach the tow line, which involved abseiling a specialist crew onto the CGS from a helicopter in heavy seas. The second tow rope was successfully attached and the crisis averted.