Routine flaring

Routine flaring, also known as Production flaring, is a method and current practice of disposing of large unwanted amounts of associated petroleum gas (APG) during crude oil extraction.  The gas is first separated from the liquids and solids downstream of the wellhead, then released into a flare stack and combusted into earth's atmosphere; usually in an open diffusion flame.  Where performed, the unwanted gas (mostly natural gas dominated by methane) has been deemed unprofitable, and may be referred to as stranded gas, flare gas, or simply as "waste gas".  Routine flaring is not to be confused with safety flaring,  maintenance flaring, or other flaring practices characterized by shorter durations or smaller volumes of gas disposal.

145 billion cubic meters (over 5 trillion cubic feet) of natural gas is estimated to have been flared worldwide during 2018.  The majority of this was routinely flared APG at thousands of well sites, and is a waste amount equal to the natural gas usage of South and Central America.  The largest seven practitioners since 2014 are Russia, Iraq, Iran, the United States, Algeria, Venezuela and Nigeria.  Activity in remote regions of Russia is greatest, with political conflict elevating the levels in other countries. The U.S. contributed nearly 10% of the 2018 world total. 

Routine flaring, along with intentional gas venting and unintentional fugitive gas emissions, have profound negative consequences.  The wasting of a primary resource provides no present economic or future wealth benefits, while creating liabilities through the build up of greenhouse gases and other harmful pollutants in the biosphere.  With most forecasts showing oil and gas use increasing into the foreseeable future, the World Bank in 2002 launched the international Global Gas Flaring Reduction Partnership (GGFRP); a public-private partnership with the aim of retiring the wasteful practice.  In 2015, it further launched the Zero Routine Flaring by 2030 Initiative; endorsed by 32 countries, 37 companies, and 15 banking institutions by the end of 2019.  Endorsers based in the U.S. were the U.S. Federal Government, the State of California, and the World Bank.  Global data spanning 1996-2018 indicate that flared gas volumes fell 10%, while oil production rose 40%.

Causes 

The routine flaring and venting of APG has been practiced since the first oil wells were commercialized in the late 1850's.  Although liquid and gas hydrocarbons have similar energy densities by mass, the factor of 1000 greater energy content by volume of liquid fuels makes storage and transport more economical. Widespread means for overcoming this relative disadvantage of petroleum gas have only been realized within the last several decades.  For example, transcontinental gas pipelines, linked with regional collection and distribution networks, now spread throughout much of the world.  Flare Gas Recovery Systems (FGRS) for processing APG into liquid or compressed fuels at the wellpad have also become increasingly mobile and varied in their capabilities. 

The decision processes leading to wasting of APG in modern times depend greatly upon regional circumstances.  Generally, the near-term financial and risk management objectives of decision makers will determine the outcome.   Some form of permitting or other regulation of flaring and venting activity exists in most jurisdictions, but details vary widely.  Factors that can increase wasting activity include (not a complete list):

 rapidly expanding oil extraction into regions farther remote from the existing gas pipeline infrastructure.
 increased challenges in logistics, such as delays in expansions of transport capacity.
 oversupply of natural gas leading to low or negative producer prices.
 competition from lower cost and lesser contaminated sources of natural gas.
 more transitory (both temporal and geographical) nature of some oil extraction operations (e.g. tight shale oil).
 lack of on-site alternatives with sufficient agility for integration with differing operations and schedules. 
 weak regulation, as caused by political conflict or instability.

Alternatives 

Similar to crude oil, APG is a primary energy source of both gaseous fuel and liquid fuel commodities that have high intrinsic value in the modern world economy. After APG is extracted, the remaining logistical barriers to consumption are cost-effective refinement and delivery to consumer markets.  Flaring alternatives preferred by the oil companies include those which remove these barriers for associated 
gas without impeding production of higher value oil.

Traditional 
1. transmission to a trading hub for distribution to short-term storage and refinery markets (preferred).
2. re-injection for enhanced oil recovery and/or longer-term storage.

Novel 
The following list includes existing commercially viable alternatives that can be performed on-site or nearby:
1. liquid fuels production with Flare Gas Recovery Systems (FGRS) and trucking to consumption markets.
a. natural gas liquid (NGL) extraction from the flare stream using mobile equipment.
b. portable compressed natural gas (CNG) production.
c. portable liquefied natural gas (LNG) production.
d. small-scale gas to liquids (GTL) conversion.
2. electricity generation with portable engines or microturbines.
3. heat generation for water treatment or other industrial processing at the wellpad.

A 2019 report from the U.S. Department of Energy states a likely reason oil companies may be slow to embrace either existing or advanced FGRS technologies is "legal, regulated flaring is the least risky option and does not require learning how to apply new technologies or modifying existing contracts and operating practices."

Effectiveness 

Gas flares using diffusion flames depend primarily on thorough air-gas mixing throughout the ejected gas stream to achieve complete combustion.  The velocity and pressure drop of the gas as it exits the tip of the flare stack must be maintained within optimal ranges to ensure adequate turbulent diffusion.  Preserving these ranges are key objectives of the engineering design process and accompanying control strategy.  Significant amounts of moisture, nitrogen, carbon dioxide, or other non-hydrocarbons accompanying APG can interfere with combustion.  On the other hand, properly designed and controlled injections of hot air and steam can improve combustion and effectiveness.

APG consists primarily of methane along with lesser amounts of ethane, propane, butane, and other alkanes.  When a flare is operating effectively,  the combustion by-products include primarily water and carbon dioxide, and perhaps small amounts of carbon monoxide and nitrous oxides (NoX).  Such flares thus demonstrate nearly complete combustion and a high conversion efficiency.  When a flare is not operating effectively, substantial amounts of APG can escape.  Also volatile organic compounds (VOCs), toxic compounds, and other damaging pollutants can be created.  VOCs and NoX can act to produce ground-level ozone at levels that exceed air quality standards.  The presence of smoke indicates a poorly operating flare. 

Most other contaminants in the APG stream occur as trace amounts. They can include toxic elements like mercury and radon that are naturally occurring.  Enhanced oil recovery efforts such as hydraulic fracturing may introduce others.   The common natural contaminant hydrogen sulfide enables the creation of sulfur dioxide and sulfuric acid in gas flares.   At elevated concentrations, it can cause corrosion and other air quality challenges, and result in characterizations such as "sour gas" and "acid flare".  As a practical matter,  gas streams with higher sulfur contamination levels are more likely to be flared - where allowed - than utilized due to their lower economic value.

Monitoring 

Available global data on gas flaring volumes are highly uncertain and unreliable until about year 1995.  Following formation of the GGFR in 2002, participating researchers from NOAA and academic institutions harnessed satellite observations to simplify the data collection and improve measurement accuracy.  Despite the scientific and technological advancements, amounts reported by industry participants and used by regulatory officials are still sometimes inaccurate.   Quantifying and locating methane emissions from improperly operated flares, intentional gas venting activity, and other equipment leaks is also a high priority for the GGFR partnership, the Global Methane Initiative, and other groups that embrace both economic and environmental scope.

Satellite Surveys 
Since most flares are operated as open flames, volumes can be inferred during aerial surveys by measuring the amount of light emitted.  The first set of global data extending back to 1995 were generated in 2006 using Defense Meteorological Satellite Program (DMSP) and Google Earth data.   After about 2010, the accuracy of individual measurements was further improved to better than +/- 10% using data from the VIIRS instruments on the NOAA-20 and Suomi NPP satellites, and MODIS instruments on the  Aqua and Terra satellites of the NASA Earth Observatory.    The data analysis continues to be further refined with contributions from other academic and mission-specific groups. Maps of global activity are now automatically generated with advanced methods such as machine learning, and the inferred volumes adjusted for disturbances such as intermittent cloud cover.  

Additional satellites and instruments have, and are scheduled to continue to come online with capability to measure methane and other more powerful greenhouse gases with improving resolution.  The TROPOMI instrument launched in year 2017 by the European Space Agency can measure methane, sulphur dioxide, nitrogen dioxide, carbon monoxide, aerosol, and ozone concentrations in earth's troposphere at resolutions of a few kilometers.    The CLAIRE satellite launched in year 2016 by the Canadian firm GHGSat can resolve carbon dioxide and methane to as little as 50 meters, thus enabling its customers to pinpoint the source of emissions.

Ground Surveys 

Ground detection using specialized handheld imaging instruments from suppliers like FLIR Systems are also capable of visualizing otherwise invisible leaks and emissions from improperly operating flares.  They are somewhat less practical for monitoring methane and other VOC concentrations over extended periods,  but can enable industry repair technicians, government regulators, and other investigators to locate and document sources of emissions in real time.

Reduction Progress 

The United Nations, International Energy Agency, and World Bank recognize routine flaring reduction efforts as low-hanging fruit in consideration of the substantial economic, environmental, and human-health benefits.   The impacts are especially large in developing countries where flaring intensity (i.e. gas flared per unit of oil produced) is often higher, due mainly to their less-developed infrastructure and markets for natural gas.   Some of the key countries targeted for reductions have included Indonesia, Iraq, Kazakhstan, Mexico, Nigeria, Qatar, and the Khanty-Mansi Autonomous Okrug - Yugra region of Russia.

From 1996 through 2018, a 10% reduction in global flaring volume (measured in cubic meters - m3) was realized while global oil production rose 40% (right figure).   It was accompanied by a 35% reduction in global flaring intensity (measured in cubic meters per barrel oil produced - m3/brl).  This was due especially in part to earlier reduction efforts in GGFR partner countries such as Russia and Nigeria.   As of 2018,  Canada, Brazil, and several Middle East nations flared at intensities below 1 m3/brl,  compared to the global average of 4.1 m3/brl. Several African nations continue to flare at over 10 m3/brl, including Cameroon at over 40 m3/brl.  

Just four nations are responsible for nearly 50% of all gas flared:  Russia, Iraq, Iran, and the United States.   Their flaring intensities range from about 3 to 10 m3/brl, and have not improved substantially in the last few years. Each country has extensive infrastructure and access to advanced technologies, but also complex business and political cultures that may be more resistant to change.

Growth in the United States 

Reported flaring and venting in the U.S. declined in the decades following World War 2, based on data from the U.S. Energy Information Administration.  Near the end of the 20th century, it reached lows close to 1.5% of APG extracted, and 0.5% of all gas extracted from both oil and gas wells.   Since about 2005,  the activity has returned to a growth path, as shown in the accompanying charts.  

32 states host and regulate gas flaring and/or venting.  The largest volume changes since about 1990 have been in the Permian Basin of west Texas and New Mexico, the Bakken Formation of North Dakota, and the Eagle Ford Group of southeast Texas. 

The U.S. activity increase exists in both volume and percentage terms. In 2018, it recaptured nearly 50-year highs, with 500 billion cubic feet and 7.5% of APG being flared.  Reports of negative producer prices for natural gas, and of a further doubling of activity in the Permian, indicate the growth trend continued in 2019.  In 2018-2019, the amount of gas wasted daily in the Permian alone was capable of supplying the residential needs of the entire state of Texas.
Five new long-distance gas pipelines from the region are under construction, with the first entering service in Q3 2019, and the others scheduled to come online during 2020-2022.

A loosening in U.S. federal regulatory policy starting 2017 enabled further increases to the waste of APG from both public and private lands.   These are summarized in a June 2019 report from the U.S. Department of Energy, which identifies the most consequential changes as:
1) "the rollback of the ... limits on methane leaked, vented, or flared from oil and gas wells on federal lands"; and 
2) "removing the requirement that companies seek out and repair leaks, requirements for reducing emissions from a variety or equipment elements, and requirements that companies prepare plans for minimizing waste before getting drilling permits"

See also
Natural gas in the United States
Environmental impact of the petroleum industry

References

External links
Flare and Vent Disposal Systems on PetroWiki
 International Petroleum Industry Environmental Conservation Association website
International Association of Oil and Gas Producers website

Category:Natural gas
Category:Methane
Category:Greenhouse gas emissions
Category:Air pollution control systems
Category:Energy efficiency
Category:World Bank