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The Total E&P UK operated Otter Field is located in 184 m water depth in block 210/15a in the Northern North Sea area (partners Dana, Exxon Mobil and Shell Expro). It came onstream on schedule in October 2002, with a plateau production rate of over 30 000 bopd being achieved in May 2003. The economic development of this field has only been possible by using a combination of innovative drilling techniques, production technology and process systems to overcome the technical challenges posed, combined with the maximum use of existing infrastructures, to minimise Capex investment. The three production wells are fitted with dual Electrical Submersible Pump (ESP) systems (a subsea first) and the total tieback distance is 21.5 km (a world record for ESP assisted tiebacks). These dual pump systems will allow significant production acceleration and improved recovery, while retaining lift redundancy and operational flexibility. The Otter oil is exported in multiphase flow via Eider to North Cormorant. Both platforms are fitted with state of the art, minimum facility slug control systems. Eider will continue to operate in "lighthouse" mode (6- 8 personnel on board), a mode of operation developed by the Eider operator to extend field life by minimising field Opex. Prior to the sanction of the Otter project, it was planned to decommission Eider in 2005. Using Eider as a host for Otter has extended field life by around 5 years, increasing reserves recovery and deferring decommissioning expenditures. The Otter development is therefore a successful example of a technically innovative and collaborative approach between the subsea tieback and host platform /infrastructure operators, partners and workforce. It provides a model for the future extension of North Sea Production, by using existing infrastructure, sharing expertise, and minimising costs. The paper describes the Otter Development project and will focus on the technological innovations that have been deployed as part of this project, namely the subsea tie-back with downhole dual ESPs in the wells, the related flow assurance issues and mitigating measures (slug control systems, use of Kinetic Hydrate Inhibition facilities), their installation and other modifications required to accept Otter on the space constrained host Shell platforms. It also discusses the technical, commercial, contractual and risk management methodology employed by Total E&P UK during the project definition and sanction stages to facilitate the successful launch of this pioneering development. |
