Abstract

Bijupirá & Salema field is located in the Campos Basin offshore Brazil in water depths ranging from 600 to 800 meters. A consortium led by Enterprise Oil and its partners, Odebrecht and Petrobras, is developing the fields. The two fields will be developed as subsea tiebacks to an FPSO with offset distances ranging from 2 to 3 km. The system comprises subsea manifolds, flowlines and risers with capability for round trip pigging. The paper will provide a brief overview of the main flow assurance challenges. Two of the flow assurance challenges highlighted include hydrates management and liquid slugging.

During various production operations, produced fluids can potentially be cooled by the surrounding cold water, resulting in gas hydrates. Such blockages can plug the bore of the subsea tree, tree piping, well jumper, manifolds, flowlines and risers, causing loss of production and inability to open or close subsea valves. The hydrate management philosophy for this project considered the following:

  • Use a combination of chemical injection using either ethanol or methanol and thermal insulation.

  • Thermal insulation on subsea production system to provide sufficient cool down time without operator action.

  • For long-term unplanned shut down, flowlines and risers can be depressurized and displaced.

  • Circulate "dry" hot oil in the flowlines and risers prior to re-start.

  • Hydrate inhibitor injection into the subsea system during start up and shut down.

Liquid slug behavior is another important consideration in the design of the production system. Large liquid slugs arriving at the FPSO can cause several problems, such as exceeding the capacity of the topsides separators, impact loads on topsides piping and swivels, vibration of risers, and erratic well flow behavior. Severe slugging is likely in the Salema flowlines due to the combination of downhill profile from the manifold towards the riser base and the potentially low flow rates expected.

This paper will present an overview of the selection and design process adopted to manage hydrates and liquid slugging for this field development considering system thermal and hydraulic performance, cost and ease of field installation and production operations.

System Overview

Bijupirá and Salema fields are located in the Campos basin offshore Brazil located approximately 250 km East of Rio de Janeiro. Water depth in the field ranges from 600 to 800 meters. The fields combined have estimated recoverable reserves of around 170 million barrels of oil in place and associated gas. The undersaturated reservoirs are at around 2,900 meters below the seabed. It is considered a "lowenergy" reservoir. Therefore, the development includes combination of water injection and gas-lift to produce the wells at the target rates.

Figure 1 shows an overall field layout of the subsea system. Bijupira field is being developed with six producers plus one contingency and four water injectors. Salema field consists of three producers and two water injectors. The FPSO is positioned approximately in the middle of the field with offset distances between the subsea drill centers ranging from 2 to 3 km.

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