Science Module: Unconventional Fossil Fuel Extraction
Oil and gas extraction:
Oil and natural gas are major fuel sources that are formed from the decomposed remains of plants and microscopic animals that lived millions of years ago. The principal component of natural gas is methane, which is the focus of BLM’s proposed rule. Prospective oil and gas wells are identified by surveying, which involves monitoring seismic waves as they reflect off of the bedrock of an area of interest to determine if it has the right composition to be a potential oil or gas reservoir. Oil and natural gas can be drilled for separately, but most conventional wells extract both oil and natural gas. Natural gas released from an oil well is sometimes called associated gas.
When a well is first tapped, there is generally enough natural pressure to bring oil and gas to the surface for collection. Some flaring of oil and gas is necessary during production testing to assess the pressure and composition of the well. During production, venting and flaring can be used as a relief measure when gas reaches an unsafe pressure or to dispose of gas that cannot be processed due to contaminants such as hydrogen sulfide. However, some gas is vented or flared due to lack of infrastructure to capture and reuse, process, or transport the gas.
The United States consumed 97 quadrillion Btu of energy in 2016. The largest source of that energy was petroleum (37%) followed by natural gas (29%). In 2016, 91% of the energy used by the US was produced domestically. Production of oil and gas on BLM lands accounts for approximately 5% of the US oil supply and 11% of the natural gas supply. In 2015, the value of oil and gas production from on-shore BLM wells was more than $20.9 billion and in FY2016, royalties from onshore BLM oil and gas leases generated revenue of $1.6 billion.
According to BLM analysis of publicly available data published in the 2016 rule, in 2014, oil and gas wells vented and flared a combined 111 billion cubic feet (Bcf) of natural gas, which is equivalent to 4.1% of the total gas produced during that time. In 2015, out of the total 85 Bcf flared, 83 Bcf was from flaring of associated natural gas from oil wells. The total amount of gas flared between 2009 and 2015 was 462 Bcf, which is 2.6% of the total gas produced during that interval, or enough natural gas to power approximately 886,000 homes a year over that period.
Greenhouse gases are gases that, when released, can trap heat in the atmosphere. The burning of fossil fuels such as oil, coal, and natural gas produces carbon dioxide, the most abundant greenhouse gas. Not all greenhouse gases have the same heat trapping ability; they are organized based on a value called their global warming potential (GWP). The GWP takes into account how long these gases stay in the atmosphere and how effective they are at trapping heat as compared to carbon dioxide, which has a baseline GWP of 1. Natural gas is considered a “cleaner fuel” because, when burned, it produces less carbon dioxide per unit of energy than fuel sources like oil and coal. However, the methane that natural gas is made up of is also a greenhouse gas, with a GWP value between 28 and 36. Because methane is such a powerful greenhouse gas, emissions of methane during production and transport could more than offset its benefits as a fuel.
The release and burning of gas has both regional and global impacts. Greenhouse gases are considered to be the major cause of climate change, which has global impacts on the environment. Regionally, flaring and venting can result in the release of toxic gases such as sulfur dioxide when burning natural gas contaminated with hydrogen sulfide
Industry experts have proposed that one way to limit flaring and venting is to make it easier to build pipelines and gas transport infrastructure. The construction of pipelines can also be hazardous to the environment, as the land must be cleared for installation of the pipeline. Additionally, any spills or leaks by oil pipelines could contaminate the surrounding environment or water supplies, while leaks in gas pipelines increase their greenhouse gas emissions profile.