Flow assurance for offshore and subsea facilities

Flow assurance, by definition, focuses on the whole engineering and production life cycle from the reservoir through refining, to ensure with high confidence that the reservoir fluids can be moved from the reservoir to the refinery smoothly and without interruption.

Overview

The full scope of flow assurance is shown in Fig. 1. Flow assurance matters specific to subsea tieback systems are shown in Fig. 2. Flow assurance is sometimes referred to as “cash assurance” because breakdown in flow assurance anywhere in the entire cycle would be expected to lead to monetary losses. A few specific flow assurance issues are discussed next.

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  Fig. 1—Full scope of flow assurance (courtesy of MSL Engineering).

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  Fig. 2—Flow assurance matters for subsea tieback systems (courtesy of BP).

Special considerations

Pressure support consideration

It is necessary for sufficient pressure to be available to transport the hydrocarbons at the required flow rates from the reservoir to the processing unit. Matters that require consideration in this regard include:

• Pressure loss in flowlines
• Separator pressure setpoint
• Pressure loss in wells
• Artificial lift method selection
• Remote multiphase boosting
• Drag reduction
• Slugging in horizontal wells
• Gas lift system stability
• Interaction with reservoir performance

Component and system design consideration

Components and systems should be designed and operated to ensure that flowrate targets are achieved and that flow is continuous. Issues to be taken into account include:

• Hydrate formation
• Wax deposition
• Asphaltenes
• Sand and solids transport
• Corrosion
• Erosion
• Scale deposition
• Interaction of slugging and pipe fittings
• Interaction of slugging and risers
• Relief and blow-down
• Pigging
• Liquid inventory management
• Well shut-in pressure

Multiphase flow considerations

For multiphase flowlines, it is necessary for the process to be able to handle the fluid delivery, and consideration should be given to a number of issues including

• Interaction with facilities performance
• Slugging (steady state)
• Slugging (transient)
• Slug-catcher design
• Severe slugging prevention
• Effect of flow rate change
• Temperature loss prediction
• Piping layout
• Remote multiphase metering
• Gas and dense phase export
• Oil and condensate export
• Separator performance

Technology development

The need for well testing and overall production system optimization contributes to flow assurance issues. Significant advances have been made in this field. Flow assurance will continue to remain critical technology as deepwater developments progress and as longer tiebacks from subsea wellhead systems are considered.

See also

Offshore and subsea facilities

Offshore arctic operations

Subsea systems

PEH:Offshore_and_Subsea_Facilities