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CPS430 - Wednesday, July 26, 2017   

What is Flaring?

Flaring is the burning of natural gas that cannot be processed or sold. Flaring disposes of the gas while releasing emissions into the atmosphere. Most flaring performed in Western Canada involves "sweet gas" which is natural gas containing little or no Hydrogen Sulphide (H2S).

Flaring is also used to dispose of sour gas containing H2S and waste gas containing contaminants such as H2S and Carbon Dioxide (CO2). It is a very important safety measure at natural gas facilities as it safely disposes of gas during emergencies, power failures, equipment failures or other "upsets" in the processing. Regulators have established guidelines for flaring reduction. Flare reduction increases the amount of marketable product being recovered and sold while also reducing emissions to the atmosphere.

Where does Flaring take Place?

Flares are used in various types of operations at thousands of locations throughout British Columbia, Alberta and Saskatchewan. These operation types include:

1) Solution Gas Flaring

Natural gas contained in crude oil is called "solution gas". Flaring is used to dispose of natural gas produced along with crude oil and bitumen. If at all possible, this gas is recovered and pipelined to a processing facility. When oil is underground, the pressure of the reservoir holds gas in the oil and the pressure is reduced when the oil comes to the surface. This occurs at facilities called "batteries" where production from one or more wells is produced and stored.

2) Gas Plant Flaring

Gas processing plants remove the water, H2S, CO2 and natural gas liquids from the raw natural gas to produce the market-ready natural gas. Flares are used to dispose of the unmarketable gases. All gas plants have flares to burn off gas safely during emergencies or "upset" conditions that interrupt the normal day-to-day operations. Many of the small plants are licensed to flare H2S rich gas after it has been removed.

3) Well Test Flaring

Well test flaring occurs during drilling and testing of all oil and gas wells. This is a standard practice used to determine the types of fluids the well can produce, the pressure and flow rates of fluids and other characteristics of the underground reservoir. If there are pipelines nearby, operators may be able to direct the test gas to a processing plant and this process is called "in-line testing". This is not a practice that is feasible for some exploratory wells as there may not be any pipelines and processing plants nearby. The pressure, flow and composition of the gas has to be determined before it can be safely handled by the pipelines and processing plants. This information determines the economic value of the well and what type of production facilities will be installed. Also, additional flaring during "under balanced drilling" operations is performed to dispose of the gas that comes to the surface. This process speeds up drilling and reduces the damage to producing formations by the drilling fluids. Some well test flaring may be necessary after certain well servicing operations. The average flaring duration is 2.5 days.

4) Natural Gas Battery and Pipeline Flaring

This type of flaring can occur at producing field facilities such as wells, dehydrators, compressors and gathering pipelines. Flares burn off gas during emergencies, maintenance shutdowns, equipment failures and other upset conditions.

Why do Natural Gas Facilities have Flare Stacks?

Flare stacks are primarily a safety measure to prevent the accumulation of gases that could pose a hazard. They are particularly important at sour gas facilities because H2S is flammable, toxic and slightly heavier than air. Combustion converts H2S into Sulphur Dioxide (SO2) which can be toxic but it is lifted by the hot plume of gases and dispersed into the atmosphere. The amount of SO2 which is released into the atmosphere is regulated under provincial air quality guidelines.

What is Emitted from the Flares?

It has been assumed that flares burn at 99% efficiency. However,1% of incomplete combustion can produce Carbon Monoxide (CO), unburned hydrocarbons, particulate matter (soot and ash), volatile organic compounds (Benzene, Toluene, Xylene), other organic compounds known as Polycyclic aromatic hydrocarbons and small quantities of Sulphur compounds such as Carbon Disulphide (CS2) and Carbonyl Sulphide (COS). Benzene is known as a cancer causing compound and Carbon Disulphide is also classified as a poison affecting the central nervous system. The effects of these depend on the magnitude, duration and frequency of exposure. Many of these compounds are not unique to flaring and are common products of incomplete combustion in emissions from automobiles, forest fires, stubble burning, barbecues and cigarettes.

1) Greenhouse Gases

CO2 is a greenhouse gas that may affect the global climate. Methane (CH4), the main component of natural gas, is more than 20 times as potent per kilogram as CO2. Flaring methane produces fewer net greenhouse gas emissions than would result from just releasing the natural gas. Some Nitrogen Oxides are potent greenhouse gases.

2) Acid Disposition

Nitrogen and Sulphur Oxides may combine with water in the atmosphere to form acids. These are eventually deposited on the earth's surface. Flaring and incineration account for the majority of upstream Sulphur Oxide emissions and a significant portion of the Nitrogen Oxides. Emissions may fall rapidly or be carried for many kilometers before being deposited. The amount of acid disposition to any given area depends on the height of the flare or incinerator stack, the wind and its direction and the precipitation patterns. In most sour gas producing areas, soils are resistant to acidification because they contain a lot of fine particles (mainly, clay and silt). In Alberta, the dry climate and the amount of alkaline dust in the air also moderates the impact of SO2 emissions.


This material was obtained from AER and Petroleum Communication Foundation web sites.