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Flaring: operational (non-continuous production)

Topic last reviewed: 10 April 2013

Sectors: Downstream, Midstream, Upstream

Operational (non-continuous production) flaring may occur on a planned or unplanned basis due to a number of causes (see the template for Flaring classification). In many cases, non-continuous flaring occurs due to the lack of availability of rotary machinery, such that there is insufficient power available at the facility to export or inject the produced gas. This document outlines some good practices to reduce non-continuous flaring as a function of its root cause. Flare mitigation actions cover both organizational and process modification aspects.

Organization
There are a number of organizational programmes that can be implemented as good practice to avoid non-continuous flaring:

  • Flaring policy: Develop and implement a flaring policy document that sets out the maximum flaring duration, volumes and mitigation measures consistent with the basis of the availability study and the emissions and discharges calculations. When an unplanned flaring situation occurs, analyse the situation immediately, find the cause and implement measures to return conditions to normal. It is also important to learn from these situations so that they may be avoided in the future. Follow flaring policy regarding maximum flaring duration and volumes and mitigation measures.
  • Maintenance philosophy and programme: Adequate maintenance of equipment that can fail and induce a flaring event is considered vital:
    • Implement a spare parts regime (taking into account transport and custom clearance issues).
    • Use preventative maintenance.
    • Vendor support should be aligned with the results of availability studies and emission / discharge calculations.
    • Maintenance and modification operations must be planned in such a way that flaring is minimized. When a modification or maintenance operation will lead to higher flaring, an evaluation should be conducted to determine whether the maintenance could be done when oil and gas production is stopped, or when gas production is reduced.
  • Training: Sensitize and train operation and maintenance personnel on flaring issues, CO2 emissions and the energy equivalent of flared volumes (see the template for Flaring: continuous production).
  • Root cause analysis: After each restart of the plant, analyse the causes that are responsible for delaying the time it takes to return to normal operation with low flaring, for example:
    • compressor pressurization duration
    • fuel gas system temperature stabilization
    • glycol regeneration system temperature stabilization
    • lack of reliability of compressors
    • training of production operators / maintenance team.

Addressing the root cause of flaring events will lead to lowered flaring and increased oil production through reduction of downtime and restart duration, and prevention of future flaring events.

  • Restart of plant: To minimize start-up flaring, the order for restarting plant unit operations should be documented and followed stringently by operators. The maximum instantaneous flared volumes per restart should also be set, and instructions given for actions to take when the maximum is reached (e.g. opening of wells on standby, or reducing production from some wells (with priority to high gas-to-oil-ratio (GOR) wells).
  • Restart of oil wells: For wells that are not difficult to restart, the Full Control of Well (FCW) tool (used to automate the restart sequence of wells, where implemented) should start wells with a low GOR first, and also consider flaring avoidance. Review the FCW set-ups periodically to ensure that they are in accordance with the evolution of wells, proper restart sequence and flare reduction goals. If applicable, first restart the HP wells, which do not need compression for export. For wells requiring compression, a portion of the gas would be flared at start-up at lower compression stages, but most of the gas would be recovered. Flare avoidance approaches should consider an alternative fuel gas source during start-up to drive compressors.

 

Process modifications

The following are examples of process modifications that can be implemented to avoid non-continuous flaring:

  • Equipment replacement: Identify obsolete equipment and plan its replacement. The equipment could be considered as ‘obsolete’ when one of the following criteria is met:
    • The equipment has operated for more than 25 years.
    • Spare parts are becoming difficult to obtain from the manufacturer.
    • The equipment is no longer supported by the manufacturer.
  • Choke-down high GOR wells: If an extended duration compressor shutdown is anticipated, the decision has to be taken as to whether some high-GOR sensitive wells (i.e. well that are difficult to restart) should be shut down. Note that an incorrect determination of GOR would have a significant impact on flaring and oil production during long duration compressor unavailability.
  • Compressor flow: Reduce flaring / maximize production following single compressor shutdown by increasing the flow through the remaining compressor (fine-tuning pressure and temperature upstream of the compressor).
  • Optimize separator conditions: Fine-tune pressures and temperatures in the process, in order to flash less gas in the separator where gas is flared. For example, if gas is flared from the MP separator, decrease pressure in the HP separator to flash more gas in the HP separator and subsequently flash less gas in the MP separator. This would also increase mass flow into the remaining compressor that compresses gas from MP to HP separator because the head to be provided would be lower. All possible side effects of operating outside normal operation conditions should be carefully considered.
  • Passing valves: Passing valves (blow-down valves, process safety valves, process valves,  flow valves) to the flare can be significant contributors to site flaring. The production team should check all valves connected to the flare every three or six months. Valve inspection should be carried several months in advance of a planned shutdown so that any spare parts that may be required to repair leaking valves can be made available (See the template for Passing valves (leakage))
  • Compression system: Install compression system for gas recovery from offloading wells. 

Technology maturity

Commercially available?:   Yes
Offshore viability: Yes 
Brownfield retrofit?: Yes 
Years experience in the industry: 21+ 

Key metrics

Range of application:  Process units routed to flare system
Efficiency: Losses due to non-continuous flaring can be significantly reduced by implementing good practice measures
Guideline capital costs: Low
Guideline operational costs: Cost savings from gas recovery
Typical scope of work description: The typical scope of work to avoid non-continuous flaring would entail the development and execution of a Flare Minimization Plan that: identifies potential flaring events, causes and abatement measures; establishes goals and performance indicators; and integrates root cause analysis and continual improvement concepts.

Decision drivers

Technical:   Life of equipment
Operational:
Optimize separator and compressor
Sequence of process unit restart
Training of operators
Commercial: Saving energy and fuel cost
Environmental: Reduction in air emissions of nitrogen oxides, sulphur dioxide, mercury, particulate matter, and GHGs
Working environment: reduced noise, heat and radiation from flare

Alternative technologies

The following are technologies that provide similar benefits and may be considered as alternatives to non-continuous flaring minimization:

  • Passing valve inspections
  • Compressors/drivers
  • VOC recovery

  

Operational issues/risks

Issues and risks are few and known. Flare reduction technology has been used for many years. If good practices are not followed, the risk of significant flaring during process upsets or equipment restarts may lead to environmental and safety concerns.


References:

  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. CAPP (2006). ‘Best Management Practices for Facility Flare Reduction’. Publication no. 2006-0018, Canadian Association of Petroleum Producers, Dec. 2006.
  3. OGP (2000). ‘Flaring and venting in the oil and gas exploration and production industry: An overview of purpose, quantities, issues, practices and trends’. Report no. 2.79/288, International Association of Oil and Gas Producers, January 2000.