The Terra Nova development, offshore Newfoundland, Canada is one of the most challenging offshore oil and gas projects ever undertaken. The remote location and harsh environmental conditions give rise to umque engineering challenges requiring innovative solutions.
Terra Nova is situated in an acme iceberg zone. As such, subsea facilities must protected against scouring icebergs. Wellhead facilities are to be placed beneath the seafloor in large open excavations called 'glory holes'. Subsea flowlines are to be trenched and backfilled to provide thermal Insulation and on-bottom stability. The construction of the glory holes at Terra Nova represents one of the most significant and challenging subsea construction projects in history. Rigorous technical and economic evaluation has resulted in the selection of a novel solution to the challenges faced.
This paper presents an overview of the Terra Nova project and the role of Coflexip Stena Offshore with the Terra Nova Alliance. A summary of the Terra Nova site, as revealed by geotechnical and geophysical surveys, is presented and a geotechnical model of the area is discussed Geotechnical challenges relevant to both glory hole construction and flowline trenching and backfilling are presented and solutions discussed.
An outline of the technical evaluation processes to establish the optimum method of glory hole construction and flowline installation operations is described and key milestones and decisions presented. Throughout, the influence of the geotechnical conditions are highlighted and their impact on the decision making and risk analysis processes reviewed.
Coflexip Stena Offshore is responsible for the installation of flowlines and construction of glory holes as part of the Terra Nova project, offshore Newfoundland, Canada.
Flowlines are to be trenched and backfilled to provide thermal insulation and on-bottom, stability. This will be the first trenching operation to be performed on the Grand Bank. A proven trenching system is to be used for the work, however, the remoteness of the site, the limited amount of site specific geotechnical and geophysical data and the local sod conditions themselves result in a number of significant challenges.
The Terra Nova development is situated in an achieve iceberg zone. As such, subsea facilities must be protected against scouring icebergs. Wellhead facilities are to be placed beneath the seafloor in large open excavations called Glory Holes.
Glory holes are to be constructed using a novel deep water excavation system that has been developed for offshore diamond mining in Southern Africa.
This paper presents an overview of the Terra Nova project, a discussion of geotechnical conditions at the site as revealed by a number of site investigations including the project specific survey in summer 1997 and a description of the process by which the solutions to the challenges have been approached.
The Terra Nova oil field lies within the Jeanne d' Arc Basin on the North Eastern Grand Bank, approximately 340 kilometres South East of St. John's, Newfoundland, Canada (Figure 1). Terra Nova is situated 40 kilometres South East of the Hibernia platform. Water depth in the area is approximately 95 metres.