Output SO2 from Temporary and Test Flaring

Plant Output SO2

What do facility operators do with output SO2 (sulfur dioxide) from short-term gas releases?  If you operate a petroleum-industry facility and it undergoes testing, servicing, cleanup, underbalanced drilling or various blowdowns resulting in planned temporary flaring, it will need appropriate permits from one or more of the governing agencies.  

The hierarchy you use for decision-making should be quite straightforward, or even familiar:  avoid or at least reduce flaring by justifying and minimizing volumes (if possible) or else meet minimum performance requirements (if not).  To reduce incidents of odours, no raw venting should be allowed if the gas can burn.

In-line testing is strongly preferred and plants must consider any feasible choices for using this option.  Otherwise, licensees need to design their programs to keep output SO2 emissions at a minimum and comply with regional ambient air quality standards.  Since this industry dominates in Alberta, Canada, we will use references to the governing bodies and regulations in this region, such as the Alberta Ambient Air Quality Objectives (AAAQO).  

Testing procedure shall follow details outlined in the Alberta Energy Regulator (AER) Directives 56, 60 (Section 3) and 71 if emergencies are involved.  If the facility intends to sweeten gas, it will probably require an Alberta Environment and Parks (AEP) sour gas plant approval even if it eliminates output SO2.

The AER has placed limits on flaring durations corresponding to facility type:

  • 72 hours for gas and crude oil sites,
  • 3 months for bitumen sites at 900 m3/day or over,
  • 120 hours for dry (less than 1 m3 water per day) coalbed methane development wells,
  • 336 hours for dry coalbed methane nondevelopment wells and
  • wet coalbed methane wells should consult the AER or Directive 60 for their specific situation.
Also, if any facility should need more time, the board (former nickname for the AER) might allow it if the cleanup is not complete, good flow not realized or certain other problems have occurred.

Temporary flaring permits and Output SO2

Temporary flaring permits involve a different process.  See Figure 4, included in Section 3.3 of AER  Directive 60.  When is one of these needed?

  1. Anytime a gas with at least 5% H2S (hydrogen sulfide), prior to the addition of fuel gas, is flared
  2. When any gas flared volume becomes greater than the volume allowance threshold for the site, excluding fuel
Flare Modelling

Now, how to determine that threshold.  AER Directive 60 outlines three tiers - Tier 1 at 600,000 m3 or less, Tier 2 at 400,000 m3 or less and Tier 3 at 200,000 m3 or less.

The permit request must include information about the activity used to fill the AERflare.xls and AERincin.xls worksheets, include a cover letter with the permit request (listing objections or concerns from the public), Lahee classifications and maps, comparisons of testing options, type of unit, reason for the request, dispersion modeling and an air quality management plan if exceedences of the AAAQO beyond those allowed in the AER low-risk criteria are expected.

A similar set of data needs to be supplied if the Volume Allowance Threshold needs to be exceeded. Also, the reason for flaring, economic analysis, gas volume justification and comparisons to similar wells shall be sent to the Technical Operations Group.

The AEP risk-based criteria allow a few predicted exceedences of the one-hour SO2 AAAQO of 450 µg/m3 to be excluded from the application, provided that:

  • refined complex terrain modelling has been conducted
  • the one-hour ground-level predicted SO2 concentration never exceeds 900 µg/m3 more than 0.1% of the time
  • the 450 µg/m3 value is not excceded more than 1% of the time
  • measured exceedences of the AAAQO do not occur

Sites should keep air dispersion modelling assessments on file for at least a year afterward.  Please call Barry at Calvin Consulting, (403-547-7557) if you need this work completed.

Blanket Permits

For simplicity, a site may receive a blanket permit for multiple sites when they are located in close proximity to each other. These permits are good for a certain period of time, may have physical and flow limitations, can only go to licensed wells, must include the Excel spreadsheets mentioned above and usually require refined dispersion modelling.

They are given to sites limited to 100,000 m3 and 10 tonnes of sulphur per event, however the group may allow exceptions in rare cases.

They will also need the surface and bottomhole locations and related information and a Sour Gas Flaring/Incineration Data Summary Report for each well. Even with all this, the awarding of requested alterations is not automatic. The AER considers additional things such as air quality issues, nearby residences (Section 3.9 of Directive 60 goes into detail), ways to avoid this flaring and/or minimize output SO2 emissions.

If the site already has an ongoing threshold, the AER allows an additional 200,000 m3 for testing, subject to the conditions spelled out in Section 3.3. If the gas exceeds neither the 5% H2S nor the appropriate volume criterion above but has at least 1% H2S, output SO2 dispersion modelling is still required.

Small volumes of gas containing less than 5% H2S may be flared with permit exemptions if:

  • they can defend their flow data,
  • do not emit more than 1 tonne of sulphur per day,
  • do not flare at more than 10,000 m3/day,
  • do not exceed 50,000 m3 in total for the flaring event,
  • have completed output SO2 dispersion modelling and
  • communicate this information to the AER Technical Operations Group.
Do licensed facilities need temporary permits when using permanent flares? Not if they keep the volumes, H2S content and rates under the licence limits and volume allowance threshold and then design the flaring operations to comply with the AAAQO. What about emergencies? They are handled on this page, but the Board understands that something unplanned can occur, as outline in Section 7.

Underbalanced Drilling

ERCB Flaring Information

Companies like to employ underbalanced drilling techniques when it is safe to do so.  It means the pressure near the drill is lower than the pressure in the formation below.  This way they can reduce water pollution in the formation, drill faster, conserve mud and still reduce friction but the method can result in dangerous kicks and blowouts and incur higher safety costs.  

The AER has special information requirements for this situation, especially if flaring exceeds the Volume Allowance Thresholds.  How did the company determine the flaring rates?  How long will the drilling take?  How much testing time is required?

Refer to AER https://www.aer.ca/rules-and-regulations/directives/directive-036 for additional regulatory information regarding underbalanced drilling.

Well Flaring - What are the Performance Requirements? Section 7 states that facilities need to use eliminate output SO2 flaring equipment in accordance with the rules provided; engineering and design must be completed properly and adhered to afterwards.  

Official methods exist for determining H2S concentrations; they include gas chromatography and/or Tutwiler gas analysis apparatus.  One important thing is to suspend operations if an H2S concentration of greater than 5% is found.  You are to prevent raw sour gas from escaping to the atmosphere and follow AER Directive 55 for proper storage maintenance regulations.

Facilities shall submit reports and information regarding flaring and testing as outlined in Section 3.10.  It refers the reader to requirements in AER Directive 40 as well as other bulletins and documents.  Section 3.11 sets out provisions for temporarily setting up a well with no output SO2 flaring prior to the start of production, with some exceptions for emergencies. 

Calvin Consulting Group Ltd. specializes Alberta ESRD and AER applications and dispersion modelling.  If your facility needs professional assistance with these matters, please call Barry J. Lough at Calvin Consulting Group Ltd. at at 403-547-7557 for help with questions you might have.  See a bit more about Calvin services here: 

Air dispersion modelling

Flaring and incineration

Government applications

Benzene emissions

Thank you.

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