The Basics - Climate Impact

Conventional and non-conventional natural gas production, gas processing, transmission and distribution all release natural gas into the atmosphere. Incremental emissions from hydraulically-fractured gas wells occur, in contrast to conventional gas wells, and methane emissions during shale gas production may contribute to global warming, as methane is a potent greenhouse gas (GHG). How much these additional emissions add to the overall GHG balance of shale gas is not yet clear and currently investigated.

However, proven cost-effective technologies now exist which can capture natural gas that would otherwise escape into the atmosphere. The captured gas may be sold, resulting in significant environmental and economic benefits. The application of technologies to reduce air emissions has been made compulsatory in the U.S. from 2015 onwards. Some companies already now apply these technologies.

Information on the more localized impacts of shale gas operation air emissions on human health and the surrounding environment can be found on the SHIP website in the Operations section.

In what way might shale gas affect the climate?

Shale gas consists of natural gas (=methane, CH₄) and, as such, may act as a greenhouse gas when released into the atmosphere. Depending on the technology used, this may be the case during the preparation of shale gas wells for production, i.e. during the flowback and drillout phases. Emissions from technical well pad installations, such as compressors, and from truck traffic add to the overall emission budget. Furthermore, when natural gas is burned, e.g. in power plants for energy production or for heating purposes, it is converted into CO₂ which also acts as a greenhouse gas when released into the atmosphere. Both shale gas production, as well as end use related factors, have to be taken into account when assessing the climate “friendliness” of shale gas.

What are methane emission pathways and mitigation measures?

During completion of a shale gas well, flowback of fracturing liquids and proppant is necessary to clean out the well bore prior to production. One standard practice is for operators to produce flowback into an open pit or tank, to collect sand, cuttings and fluids for disposal, and to vent or flare the natural gas that is co-produced with the flowback liquids and solids. Reduced Emission Completions (REC) is a practice to recover natural gas and condensate produced during flowback following hydraulic fracture: Portable equipment is brought to a well site to separate sand and water and to process gas and condensate for subsequent sale. This significantly reduces venting and flaring while increasing gas sales.

Methane emissions from drill pad installations, like compressors, valves, dehydrators, and pipelines, all add to the overall emission budget. Mitigation options are available for all of these emissions. The recommended technologies and practices are summarized and detailed, along with technical descriptions and payback estimates, within the U.S. Natural gas STAR program.

How precisely is the greenhouse gas balance of shale gas constrained?

Just like any energy resource, the greenhouse gas (GHG) balance of shale gas must consider the GHG emissions from cradle to grave, i.e. from production to end use. Life cycle analysis (LCA) is commonly used to calculate GHG balances of different energy resources, with energy production as end use. In terms of end use, natural gas is the cleanest of the fossil fuels: The combustion of natural gas emits almost 30 % less CO₂ than oil and about 45 % less CO₂ than coal.

On the production and transportation side, calculations of shale gas GHG emissions are much less constrained than those for conventional or liquefied natural gas or other fossil fuels. This is due to uncertainties regarding ultimate production volumes and variability in flaring, construction and transportation of natural gas from shales.

Uncertainties in input data and differences in calculation methods result in a variety of published results on the overall GHG balance of shale gas. However, most recent studies and reports indicate that the GHG balance of shale gas is much closer to that of conventional natural gas than to that of coal when currently available best technologies are used. New data on production volumes and the voluntary and/or legally required application of Reduced Emissions Completions, or other emission mitigation technologies, will significantly improve future studies.