Topic last reviewed: 10 April 2013

Sectors: Downstream, Midstream, Upstream

Flaring can occur in the oil and gas industry for many reasons, ranging from initial start-up testing of a facility to unplanned equipment malfunctions. Generally, flaring can be classified in the following categories for the purpose of defining techniques for flare reduction:

  • Initial start-up flaring occurs during the commissioning and initial start-up phases of a plant or process unit, when gas and liquids are introduced into new facilities and equipment to test the production of the products for sale (oil, gas, LPG, condensate, etc.).
  • Continuous production flaring occurs after initial start-up, when the plant or process unit is in production. Continuous production flaring is characterized by a routine, continuous gas stream which is routed to a flare system because there is no economical gas valorization route for a satellite field or for the routine venting of flash gas in upstream production.
  • Operational /non-continuous production flaring may occur on a planned or unplanned basis for a number of reasons.Planned non-continuous production flaring may occur, for example, due to scheduled maintenance, equipment shutdowns, well completions, workovers and liquids unloading, etc. Unplanned non-continuous production flaring may be caused, for example, by mechanical equipment failures, instrument failures, and difficulty restarting well production.

The following table presents some common causes for each category of flaring. The determination of the cause of a flaring event is important to allow identification and evaluation of flare reduction alternatives, e.g. modification projects to reduce continuous or planned non-continuous production flaring, and clear procedures to avoid future unplanned non-continuous flaring events.

Flaring categories




Initial start-up flaring


During the first weeks or months of the plant life, some of the associated gas may be flared before all the gas compressors are commissioned, or for reservoir management reasons.

Continuous production flaring (mainly older sites)

Well with low gas-to-oil ratio (GOR)

Gas is flared because it is not economical to recover the gas.

Gas Utilization Infeasible

Lack of local gas market, remoteness from international markets, lack of gas gathering and compression infrastructure.

Gas release to flare

Gas and liquid are released continuously from the process to flare (e.g. glycol flash drum, glycol gas stripping, compressor seals, storage tanks etc.).

Planned operational flaring

Maintenance and inspection

  • Preventive maintenance (compressors, drivers etc.).
  • Replacement of equipment.
  • Regulatory inspections.

Modifications and construction

  • Work on plant system:
    • Preparation of new plant
    • Tie-ins
    • Change of operating conditions, power distribution, etc.
  • Work in the vicinity of an asset: simultaneous operations

Reservoir and well maintenance

  • Reservoir monitoring (studies, multi-flowrate trials etc.)
  • Gas injector well servicing (acidification, squeeze, wire line, etc.)
  • Flaring due to the offloading of sensitive wells (no facility to recover wellhead low pressure gas), or due to sensitive wells opened to flare in some cases of shutdown

Safety and production operations

  • Plant and well testing
  • Operations testing
  • Safety testing
  • Leak testing

Drilling and workovers

  • Well clean-up after drilling, workovers
  • Well tests

Unplanned operational flaring

Production dynamics

  • Start-up after shutdown
  • Off-spec gas issues
  • Flow assurance problems (slugs etc.)
  • Changes in HC composition, flow, etc.
  • Unavailability of receiving facilities (impossible to export gas)

Mechanical failures in machines

Rotating and alternating equipment (pumps, compressors, turbines, etc.)

Instrument and valve failures

  • Safety, process and equipment protection instruments failures (fire and gas detectors, vibrations protectors, etc.)
  • Process and safety control systems failure
  • Connection and wiring systems failure
  • Signal loss


  • Any type of failure in a gas-injector well
  • Difficulties in restarting a producer well


  • Failures due to erosion or corrosion, internal and external
  • Electrical failures: failure of power generators, power distribution networks, motors, heaters, or other electrical equipment
  • Human factors: any human action resulting in involuntary flaring (lack of preparation and procedures, non-compliance with an existing procedure, etc.)
  • Miscellaneous: causes that have been identified but do not fit into any of the other categories
  • Unexplained: any flared volume for which the exact cause is difficult to identify (except problems with metering)

Safety flaring

Flaring to purge flare lines with hydrocarbon gas, for safety purposes. Includes emergency shutdown with depressurization.

Technology maturity

Commercially available?: No
Offshore viability: No
Brownfield retrofit?: No
Years experience in the industry: <5

Additional notes:

NB: Technology Maturity section is N/A - this document is classification of flaring types only.


  1. Labeyrie, H. and Rocher, A. (2010). ‘Reducing Flaring and Improving Energy Efficiency: An Operator’s View’. Society of Professional Engineers (SPE) Paper 126644.
  2. World Bank (2004). ‘Global Gas Flaring Reduction, A Public-Private Partnership: A voluntary standard for global gas flaring and venting reduction’. Report Number 4, World Bank Group, May 2004. (Publication reference 29555.)

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