The headlines read: NASA airplanes fly low over Denver skyline and the Front Range testing ozone levels (Denver Post), NASA, EPA, NCAR launch air-testing blitz to track pollution (Denver Post Environment) and Boulder researchers leading landmark Front Range air quality study (Daily Camera).
These articles give the reader the general impression that the study is on Denver’s ozone pollution due to traffic and normal industrial activity associated with cities. To their credit, The Denver Post Environment article briefly mentions that “NASA picked Colorado for intensive testing (looking at benzene, ethane, methane, formaldehyde and more)”. Really?
You won’t find too much benzene, ethane, and methane coming from your car or truck or light industrial activities. These substances are all produced as a result of oil drilling and production operations, although you will also get some methane from cattle stockyards.
The map of the study area (shown on the left) from NASA is quite telling as it encompasses the heart of the Niobrara Play over the Wattenberg Field all the way east to Platteville where the 527-mile-long White Cliffs crude oil pipeline that runs from Northern Colorado to Oklahoma will double its capacity in August.
During the exploration for oil and natural gas, the venting and exhaust of natural gas from wells being drilled as well as producing wells, is a normal and necessary part of oil and gas production. A significant amount of the gas release comes as a result of flaring at the well site.
You may ask why would an oil company burn off valuable hydrocarbon gases such as propane and ethane that they could sell?
There are many circumstances where it may not be economic, practical or safe to conserve natural gas (Flaring Questions + Answers, Bott, 2007) :
- Volumes of solution gas from crude oil wells may be too small or the location too remote to justify building pipelines and processing facilities.
- Incidents during drilling, production, processing or pipelining may lead to releases of natural gas.
- After drilling a successful well, it may be necessary to produce natural gas for a short period of time to establish flow rates and gas composition, key considerations when determining the type and size of equipment to be installed.
- During and after some drilling and servicing operations, it is necessary to dispose of natural gas contaminated with drilling mud, fracturing fluids or acids.
- Gas containing hydrogen sulphide (H2S) needs to be disposed of safely if it cannot be processed otherwise. Combustion converts the H2S into water vapour and sulphur dioxide (SO2), which are lifted and dispersed by the plume of hot gases. (Note: The Niobrara typically does not produce H2S)
While the intent of flaring is to completely combust all natural gases from a well, incomplete combustion of hydrocarbons can lead to the formation of carbon monoxide (CO). Nitrogen in the air is also oxidized during combustion to form oxides of nitrogen, known collectively as NOx. It just so happens that oxides of nitrogen such as nitric oxide (NO), and nitrogen dioxide (NO2) can contribute to ground-level ozone. Under some circumstances, inefficient combustion of hydrocarbons may also produce VOCs (Volatile Organic Compounds), which include a wide variety of hydrocarbon compounds heavier than ethane. VOCs can combine with oxides of nitrogen in the presence of sunlight to create ground-level ozone and smog. One of these VOCs is benzene. Glycol dehydrators, used to remove water from natural gas, are the largest industrial source of benzene emissions (Bott, 2007)
What about Formaldehyde? That substance really stood out in the NASA list as an uncommon air pollutant. It just so happens that formaldehyde is used in aqueous solutions as a preservative. In [drilling] muds, paraformaldehyde is added to protect against bacterial attack. It is used as a preservative for starch, xanthan gum, guar gum and other natural polymers that are prone to attack by bacteria. When added to a [drilling] mud in advance of a bacterial inoculation and maintained, paraformaldehyde can effectively control many strains of bacteria. (Schlumberger) Formaldehyde is is also produced at compressor stations and dehydration units that strip liquid from the gas and speed it up for transport through interstate pipelines. (TheTimesTribune, 6/18/2012)
So there you have it, inefficient combustion of natural gas at the well head produces nitrogen oxides and VOCs which produce ozone in the presence of sunlight, unburned natural gases such as methane and ethane, and benzene from the dewatering of natural gas liquids, and formaldehyde at dehydration and compressor stations. Throw in a a study area encompassing the heart of the Niobrara Play and what do you get?
Conclusion: NASA is studying pollution from oil drilling operations and comparing it to typical air pollution from a large city, Denver.