In addition to the air quality impacts discussed in Stage 3, new activities and infrastructure come online in the production phase that may contribute to air emissions. In the production stage for oil operations, the associated natural gas that emerges from the well is separated from the crude oil. While saleable gas is sometimes captured and transported to market, it is often flared or vented due to the lack of natural gas pipelines in the area. As discussed in Stage 3, however, new EPA regulations effective in 2015 and 2016 will significantly limit both practices.
In natural gas operations, the produced gas generally undergoes processing to remove water and other constituents to meet sales quality requirements prior to transport. The dehydration units that remove water from the gas can also release VOCs and other hazardous air pollutants (HAPs) into the air. If the gas contains sulfur, it goes through a sweetening process to remove it. Once extracted, the sulfur may be flared, incinerated, or possibly captured for market.
After the gas has been conditioned, it is piped to compressor stations where it is pressurized for transport over longer distances. If the compressor engines are diesel-powered, they can emit nitrogen oxides, carbon monoxides, and VOCs.
There are also fugitive emissions of methane from pipelines and other equipment, as well as releases from the pneumatic instruments controlling the operation of valves. Researchers have identified these pneumatic devices, which release gas as part of their regular operation, as a major source of methane emissions from natural gas infrastructure. 1 These sources too will be affected by the EPA’s proposed regulations under the Clean Air Act, which require operators to locate and plug leaks from equipment and infrastructure, including pneumatic pumps, pneumatic controllers, and compressor stations. 2 The agency anticipates the rule will be final in 2016.
- David T. Allen, Adam P. Pacsi, David W. Sullivan, Daniel Zavala-Araiza, Matthew Harrison, Kindal Keen, Matthew P. Fraser, A. Daniel Hill, Robert F. Sawyer, and John H. Seinfeld, “Methane Emissions from Process Equipment at Natural Gas Production Sites in the United States: Pneumatic Controllers” Environmental Science and Technology 49 (2015), 633-4, http://pubs.acs.org/doi/pdf/10.1021/es5040156. ↩
- U.S. EPA, “Proposed Climate, Air Quality and Permitting Rules for the Oil and Natural Gas Industry: Fact Sheet” ↩