OTC 11920
Terra Nova Vessel Design and Construction
Tom Doyle, John Leitch/Brown & Root Energy Services
Copyright 2000, Offshore Technology Conference
This paper was prepared for presentation at the 2000 Offshore Technology Conference held in Houston, Texas, 1-4 May 2000.
This paper was selected for presentation by the OTC Program Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the Offshore Technology Conference and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the Offshore Technology Conference or its officers. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the Offshore Technology Conference is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of where and by whom the paper was presented.
Abstract
The Terra Nova Floating Production Storage and Offloading (FPSO) is the first such vessel specifically designed for ice infested harsh environments. The development of this unique vessel will be described by presenting the major aspects of the vessel from the initial design by Brown & Root Energy Services (BRES), construction of the vessel by Daewoo Heavy Industries (DHI) in South Korea, through to delivery to Newfoundland Canada. The unique design considerations such as the harsh environment of the Canadian Grand Banks region and the requirement to dis-connect during ice flow/iceberg activity required a completely new vessel design. This paper describes these challenges and the eventual solutions by touching on analyses and the extensive model test program conducted. The vessel construction and delivery phases are also discussed together with shipyard interface and management issues.
Introduction
This paper addresses the development of the Terra Nova FPSO hull, from design through construction to delivery, highlighting the environmental drivers which led to the current design. In addition, the vessel performance in the harsh Canadian environment of the Grand Banks is discussed and an update of the vessel construction and delivery status presented.
The Field. The Terra Nova oil field is the second largest oil field discovered to date in the Jeanne d'Arc basin on the Grand Banks (Fig.1). The first phase of the field development consists of the Graben and East Flank and is estimated to contain recoverable reserves of 47.7-63.6 SMm3 (300-400 million barrels).
The Terra Nova field is located in 94 metres (approximately) of water, 350 km East-Southeast of St. John's, Newfoundland and 35 km Southeast of the Hibernia field.
Field Development. The Terra Nova oil field will be developed using an ice strengthened floating production facility, with ice avoidance capability and subsea wells (Fig.2).
The export of crude will be by tanker. Produced gas will be used as fuel and for gas lift. Excess gas will be re-injected.
Terra Nova is the first FPSO in these waters and the design solution adopted is a marker for follow-on developments in the area.
The Terra Nova development proponents are: Petro-Canada (operator), Mobil Oil Canada Properties, Husky Oil Operations Ltd, Norsk Hydro Canada Oil and Gas Inc, Murphy Oil Company Ltd, Moschober Operating Ltd, and Chevron Canada Resources.
Environmental Considerations
General. The Grand Banks region has a harsh environment, much like the Northern North Sea. Intense storms occur frequently in winter, with winds generally in the northwesterly and southwesterly directions, Table 1.
Seastates produce short period, steep waves with waveheights in excess of 30 metres.
Superstructure icing can occur between December and March because of the temperature, wind and wave conditions.
Restricted visibility is common, especially in the spring and summer months, when warm air masses overlie the cold ocean surface.
Pack ice occurs during the winter season but only reaches the Terra Nova regions one-year in three. Icebergs migrate into the region annually mainly during the months of March to August inclusive (ice season).
Due to the presence of icebergs, the floating production, storage and offloading facility, the FPSO, must have the capability to disconnect and move away without external assistance.
The remote location, incidence of bad weather and extensive periods of fog make it essential that the FPSO has high helicopter operability whenever the weather is clear.
The stability analysis takes into account a considerable ice accumulation of 2000Te. In addition, the vesssel is equipped with a steam ice clearance system, comprising of a steam ring main to which steam lances can be attached. The helideck is further equipped with a portable de-icing unit.
All pipework and equipment exposed to below zero temperature and vulnerable to damage is trace heated and insulated. Most trace heating is electric however the hydrocarbon and ballast systems use steam trace heating.
