The Tarsiut Island Monitoring Program

ABSTRACT This paper presents a description of the monitoring programs used during construction of Tarsiut Island and during the drilling of the Tarsiut N-44 exploration well. The objectives of this program were threefold:To ensure that the island was constructed according to acceptable design standards.To ensure that the island performed satisfactorily under the imposed environmental loads throughout the drilling of the Tarsiut N-44 exploration well.To collect data that could be used to streamline the design of future islands. A description of the monitoring strategy and instrumentation is presented. Typical results are reviewed and recommendations for future programs are given. INTRODUCTION Tarsiut Island was the first artificial caisson-retained exploration drilling island constructed in the Beaufort Sea. The island was built during 1980 and 1981 by Canadian Marine Drilling Ltd. on behalf of the operator, Gulf Canada Resources Inc. A description of the design and construction of the island is presented by Stenning and Fitzpatrick (1983). The layout and dimensions of the island are summarized in Figure 1. This drawing represents the island as it was designed for drilling the first exploration well during the 1981-82 winter. The island represents a benchmark in the design of Arctic drilling platforms. It was not only the first caisson retained island in the Arctic, but was also the first island to be built outside the 1and fast ice zone. Furthermore, Tarsiut was regarded as the prototype of possible future production platforms in the Beaufort Sea. With this in mind, Gulf et al committed to an extensive monitoring program, the objectives of which were threefold:To ensure that the island was constructed according to acceptable design standards.To ensure that the island performed satisfactorily under the imposed environmental loadings throughout its design life.To collect data that could be used to streamline the design of future is1ands. A quality assurance program was implemented in order to achieve the first objective. The second objective was satisfied by monitoring the response of the island under ice and gravity loads. This " operational monitoring" program was implemented during the drilling activities on the island and was integrated into the alert and evacuation procedures. A comprehensive research program was put into effect to satisfy the third objective. This work was primarily orientated to collecting data on winter ice forces and island response to these forces. Geotechnical data on caisson "setdown" pressures, island settlements, and ground temperatures were al so collected as part of the research program. The remainder of this paper describes the monitoring strategy and instrumentation for each of the monitoring programs. Examples of typical results are presented and recommendations for future monitoring programs are also given.