This paper Outlines the principal factors which influenced the design and construction of Tarsiut Island in the Canadian Beaufort Sea. The intent of the paper is to provide an insight into the rationale behind the design and construction of the island.
Constructed of four concrete caissons, arranged in a square, backfilled and standing on top of a submerged sand berm, Tarsiut Island represents a considerable advance Tent in Arctic offshore technology. Prior to Tarsiut, islands were constructed with sacrificial beaches or sandbag protection. These 'artificial' islands were limited to relatively shallow water, due to the vast fill volumes required and their susceptibility to damage from summer storms, especially during construction. The deepest 'artificial' type island is Issungnak, which was constructed in 60 feet of water in two summer seasons by Esso Resources Canada. Tarsiut Island, on the other hand, is located in 70 feet of water and required just one construction season to complete. Although less susceptible to summer storms than conventional islands, Tarsiut still sustained wave damage during installation.
The Tarsiut Island project was initiated to meet the following objectives:
Drill an exploration well.
Prove that caisson structures can withstand the harsh winter environment in the Beaufort Sea.
Gain experience in design and construction of offshore Arctic structures so that future developments can proceed efficiently.
The first objective was successfully achieved in Apr11, 1982, when the first Tars iut well produced oil at a rate 0 f 800 barrels per day. The success of this first well generated sufficient interest to drill a second well. The Island was upgraded to meet summer operating conditions and a second well was successfully drilled in the spring and summer of 1982. The results of this well have indicated oil reserves of about 350 million barrels.
With respect to the second objective Tarsiut proved itself very resilient to winter ice loads. It's safe to say that Tarsiut proved, beyond any doubt, that caisson structures can withstand winter ice loads.
The third objective can best be judged by the application of the Tarsiut Island experience to following caisson islands. Subsequent to Tarsiut Island, one steel caisson has already been installed at Uviluk (Dome's SSDC), and two others are under construction-one for installation in 1983 (Esso'S caisson-retained island) and one for installation in 1984 (Gulf's Mobile Arctic Caisson 'MAC'). Certainly, Dome's SSDC project could not have been completed in its nine month design/construction schedule without the experience gained at Tarsiut.
The purpose of this paper is to describe the Tarsiut Island concept, design and construction methodology. Since the topic is broad and the paper is short, the subjects will not be dealt with in depth; however, it should give the reader a good overall appreciation.
In order to meet the project objectives, it was necessary to design an island that had the following principal characteristics.
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