Tarsiut Island is the first caisson retained island that has been built for drilling operations in the Arctic Offshore. Because of its novelty, a real time monitoring program involving the predicted and observed performance of the island under ice loading was established to ensure safe and efficientdri11ing operations and to satisfy government requirements.
To accomplish this program, an extensive state of the art instrumentation, data acquisition and monitoring system was developed and utilized to collect ice action and island response information. The data was used in real time to assess island stability and provide an alert warning to drilling personnel. The alert levels were related to drilling activities to ensure the integrity of the operation.
This paper describes the methodology, procedures and experiences associated with the Tarsiut winter monitoring program.
Although many artificial islands have been built in the Canadian Beaufort Sea (De Jong and Bruce, 1978), the Tarsiut structure represents a significant new extension to Arctic drilling technology. This island, constructed by Canadian Marine Drilling under contract to Gulf Canada Resources, was the first caisson retained island used for exploratory drilling in ice infested waters (Stenning and Fitzpatrick, 1983). During the winter, spring and summer of 1982, Gulf Canada as operator for the Tarsiut group*, dri11ed the Tarsiut N-44 and N-44A wells from the island as a part of its Beaufort Sea exploration program. The N-44 well, drilled on the same geological structure as the Tarsiut A-25 discovery of 1980, yielded 556 m / day (3500 bbl /day) while the subsequent N-44A delineation well, side tracked from the same well bore, was less prolific yielding 346 m3/day (2175 bbls/day).
In addition to the novel use of caisson technology to reduce the fill requirements for island construction, the Tarsiut structure was located in 21 m of water making it the deepest artificial island ever built in the Beaufort Sea. The island was al so located in an area where dynamic ice motion was expected for at least part of the winter season.
Tarsiut was designed on the basis of theoretical analyses, model tests and full scale experience at other islands (Croasdale and Marcellus, 1978). The design work indicated that under expected ice conditions and loadings, there should be no hazard to the island from the stability or operational viewpoint. However, because Tarsiut was novel, there was a finite probability that the ice conditions might be different than expected or that some interactions not predicted by experience, theory or model tests might occur. This was recognized by Gulf Canada, its partners and the Canadian regulatory agencies and procedures were implemented to ensure that the effects of the ice environment on the stability and operations from Tarsiut Island were known or could be anticipated at all times.
