The Troll Olje Platform

ABSTRACT The Detail Engineering of the Troll Olje Platform commenced in May 1992 with the objective of developing an optimum platform solution both economically and technically within a time constraint of 44 months measured up to and including start of oil and gas production offshore. The challenges as given by the Troll Olje Field Characteristics are a large water depth in combination with difficult soil conditions, oil reserves contained in thin layers and a shallow formation covering a wide a real extent and finally the time limit for first oil determined by reduced recovery in the event that gas production from Troll Phase 1 is started first. The objectives have been challenged by seeking new approaches within the project execution principles and a platform concept based on a catenary anchored self contained concrete semi-submersible with modularised topsides including maximized onshore/atshore work resulting in a completed platform prior to tow out. INTRODUCTION This paper gives a presentation of the Troll Olje Platform concept, project execution strategy and activity sequence as a solution to the challenges governed by the field characteristics and inherent time constraint due to Troll Phase 1 start-up schedule. Included is a brief review of the design considerations followed by a description of the main platform elements, i.e. the topside facilities, concrete substructure and the mooring system. A special design feature is the topsides structural concept which is emphasized and discussed separately. Finally fabrication, installation and platform completion prior to first oil are presented. The development concept for Troll Olje is based on a single floating self-contained production and quarters (PO) platform as a field centre with associated subsea system. The substructure is a concrete semi submersible. The Floating Production Unit (FPU) will be connected to four subsea clusters with a capacity of 26 production wells from the Troll West Oil Province (TWOP). Stabilized oil and dehydrated gas is trans- ported through pipelines to shore with the gas routed via the Troll Phase 1 platform. Continuous gas injection and artificial gas lift are provided for. The Floating Production Unit is shown in figure 1. The project schedule from start detail engineering to production start-up is 44 months. Although the development project includes production from the TWOP the FPU will be designed also to cater for future tie-in of up to five clusters having a capacity of up to 32 oil producing wells from the Troll West Gas Province (TWGP). PLATFORM PROJECT EXECUTION Execution Principles The development phase of the Troll Olje Platform Project refers to the phase of the work execution which concludes with the facilities being ready to commence production of oil and gas offshore. The project shall be executed in accordance with the basic philosophy of engaging contractors to carry out the following main activities;Detail Engineering DesignEquipment and Material ProcurementFabrication, Construction, Mechanical Completion and CommissioningAtshore Installation, Hook-up and CommissioningOffshore Installation, Hook-up and Commissioning The exception, however, being the commissioning execution which will be undertaken by the Operator with assistance from a hook-up contractor working in an integrated team.