Flow Assurance

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.

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.

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