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The Shtokman gas condensate field lies in the centre of the shelf zone of the Russian sector of the Barents Sea about 600 kilometers northeast from Murmansk. Shtokman Development AG (SDAG, 51% Gazprom, 25% Total and 24% Statoil) is in charge of the integrated development of the phase 1 of the Shtokman Gas condensate field. Exploitation of the gas field will be done through a floating platform that will export gas and condensate to the shore via pipeline. Significant sea ice invasions occur at Shtokman in approximately 3 out of 10 years, on average. Icebergs may also occur in the SCGF area. Ice and iceberg management activities have been planned to support the operations. The ice and iceberg management activities include surveillance, threat assessment and physical management. At this stage, definitions of strategy and philosophies for ice and iceberg management have been developed and preliminary plans for the main tasks have been outlined. The present paper describes the different components of the ice and iceberg management system and the rationales for the main technical choices. 1 INTRODUCTION The Barents Sea is bordered by the cold and icy waters of the Arctic Ocean and the Kara Sea on the North and East sides and by the warm water of the Norwegian Sea on the west side. The Gulf Stream enters the Barents Sea as the North Cape and Spitsbergen branches of the Norwegian current, bringing warm water into the region. The border between warm and cold water varies in location, depending on the oceanographic and meteorological conditions; this change is more sensitive in the Eastern part of the Barents Sea and especially at the Shtokman field. Sea ice does not form at Shtokman (except very thin ice in very cold years) but is exported from the North - Northeast by persistent winds. Thus, the origin of ice which can arrive at Shtokman is North-Eastern Barents Sea and possibly Kara Sea. The presence of drifting sea ice is observed in approximately 40% of the years on the Shtokman field, based on satellite observations from 1974 to 2007. This means that sea ice in the Shtokman area occurs approximately once every 2.6 years. Sea ice arrives rapidly at the Shtokman area and ice concentration may increase from 2/10th to above 8/10th within a few hours. Furthermore, ice may not be continually present at Shtokman throughout any one ice season. Historically, icebergs have been observed near Shtokman (within 75 nm) about once every five years on average. 10% of icebergs observed within 25 nm circle around Shtokman were in ice while 40% of icebergs observed within up to 100 nm north of Shtokman were in ice. With regard to seasonal variation it must be assumed that the probability of encountering icebergs at Shtokman during spring is higher than during late summer / early autumn.

The Shtokman Gas Condensate Field (SGCF) is located 610 km from Murmansk in the Barents Sea. The water depth at location is around 340 m. The offshore facilities of the SGCF Phase 1 development will include ice-resistant ship shape disconnectable turret moored floating platform (FP). Significant sea ice invasions occur at Shtokman in approximately 3 out of 10 years, on average. Icebergs may also occur in the SCGF area. Ice and iceberg management are planned to support the FP operations. The present paper describes the methodology to assess performance, operability and risk of the FP in waters where occasional invasion of sea and glacial ice is anticipated. Introduction Challenges with ice-related design and operating philosophy for the Shtokman FP have been described in [Ref. 1]. In brief, the main challenge is to achieve an appropriate reliability level and at the same time minimize operational downtime at acceptable costs. Table 1 summarizes the main ice-related challenges as identified in the pre-FEED and updated during the FEED, categorized by the accidental scenarios. Actions have been taken in order to address the challenges and quantitatively assess the risks. It shall be emphasised that no attempt was made to target the design of individual components to achieve the target reliability level for the entire system, i.e. floating platform with respect to ice actions. This is simply because it would have been too speculative given all the uncertainties involved. On the contrary, it was decided early to establish challenging but realistic design targets for the main systems (e.g. hull, mooring and disconnection system) and in parallel, work on design of the operational measures, including assessment of their efficiency and reliability. Further, quantitative operability and risk assessments of the entire system have been performed to evaluate potential needs for optimisation. The objective of this paper is to present the approach developed and used for assessing performance, operability and risk of the Shtokman Floating Platform with regard to sea and glacial ice. The content of this paper is based on numerous studies performed to provide input for the Final Investment Decision.

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Several offshore platforms and artificial islands will be constructed in the Caspian Sea for the exploration and production of oil. In some cases, vulnerable structures can be protected against severe ice loading using rock mound barriers. These barriers will be constructed in shallow water on a soft sediment layer. This paper discusses the assessment of ice interaction scenarios and the FEM stability analyses for the design of the ice barriers. In normal winters, rock slopes will cause the thin ice to fail in bending at low forces creating ice rubble. In this scenario, barrier stability has to be checked against local edge failure due to initial interaction of thin ice. Later in the winter, global failure has to be evaluated in the situation when ice rubble has extended only to the toe of the rock slope and thick ice acts against the ice-rubble, rock-mound combination. Various other extreme scenarios require analysis including direct action by thick ice and a frozen-in condition, which prevents edge failure and encourages decapitation if the barrier freeboard is low. The stability of the barriers under ice loading has been analyzed with a FEM program. From the analyses several failure types can be recognized which can also be found in literature.