Flow Assurance Challenges

  1. Subsea
  2. Production Facilities
  3. Production Engineering
  4. Process Engineering
  5. Production Chemistry
  6. Flow Assurance


Flow assurance analysis is a recognized critical part of the design and operation of subsea oil/gas systems. Flow assurance challenges focus mainly on the prevention and control of solid deposits that could potentially block the flow of product. The solids of concern generally are hydrates, wax, and asphaltenes. Sometimes scale and sand are also included. For a given hydrocarbon fluid, these solids appear at certain combinations of pressure and temperature and deposit on the walls of the production equipment and flowlines.

Solids control

The solids control strategies used for hydrates, wax, and asphaltenes include the following:

  • Thermodynamic control: Keep the pressure and temperature of the entire system out of the regions where the solids may form.
  • Kinetic control: Control the conditions under which solids form so that deposits do not form.
  • Mechanical control: Allow solids to deposit, but periodically removing them by pigging.


Flow assurance has become more challenging in recent years in subsea field developments involving long-distance tie-backs and deepwater. The challenges include a combination of low temperature, high hydrostaticpressure for deepwater and economic reasons for long offsets. The solutions to solids deposition problems in subsea systems are different for gas versus oil systems.

Gas systems

For gas systems, the main concern of solids usually is hydrates. Continuous inhibition with either methanol or mono-ethylene-glycol (MEG) is a common and robust solution, but low-dosage hydrate inhibitors (LDIs) are finding more applications in gas systems. The systems using methanol for inhibition are generally operated on a once-through basis. The methanol partitions into gas and water phases and is difficult to recover. Systems using MEG on the other hand normally involve the reclamation of MEG. If a hydrate plug forms, the remediation method may be a depressurization.

Oil systems

For oil systems, both hydrates and paraffins are critical issues. In the Gulf of Mexico (GoM), a blowdown strategy is commonly used. The strategy relies on the insulation coating on the flowline to keep the fluids out of the hydrate and paraffin deposition regions during operation. During start-ups and shutdowns, a combination of inhibition, depressurization, and oil displacement is performed to prevent hydrate and paraffin deposition. Wax is removed by pigging. The strategy is effective, but depends on successful execution of relatively complex operational sequences. If a hydrate plug forms, it is necessary to depressurize the line to a pressure usually below 200 psi for a deepwater subsea system and wait for the plug to disassociate, which could take a very long time in a wellinsulated oil system.

Flow Assurance Concerns

Flow assurance is only successful when the operations generate a reliable, manageable, and profitable flow of hydrocarbon fluids from the reservoir to the end user. Some flow assurance concerns are:

  • System deliverability: Pressure drop versus production, pipeline size and pressure boosting, and slugging and emulsion.
  • Thermal behavior: Temperature distribution and temperature changes due to start-up and shutdown, and insulation options and heating requirements.
  • Solids and chemistry inhibitors: Hydrates, waxes, asphaltenes, and scaling.

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