Methane and Non-methane Hydrocarbon Emissions from Natural Gas Well Pad Soils
Abstract
In 2015, the subsurface casing of a natural gas storage well at the Aliso Canyon storage facility in California failed, causing one of the worst natural gas leaks in U.S. history. About 100,000 tonnes of natural gas leaked into the atmosphere from the soil around the wellhead over a period of several months. Except for this extreme case, however, very few measurements of well pad soil emissions from active oil and gas wells have been collected, and no nationwide estimate of this emission source exists.
To better understand emissions from subsurface natural gas infrastructure, we used a flux chamber to measure methane and non-methane hydrocarbon fluxes from natural gas storage wells and production wells in Utah and Texas. At the facilities examined, most well pad soil fluxes had similar chemical composition to raw natural gas, indicating that fluxes originated primarily from natural gas leaks from the wellbore or other subsurface infrastructure. Flux speciation also showed that bacteria consumed a portion of emitted natural gas before it reached the surface, and that the portion consumed varied with season. Fluxes from well pad soils tended to be highest near wellheads but were not spatially uniform, and areas of highest fluxes sometimes changed over time. Flux magnitude also varied temporally, often dramatically over short periods due to changes in atmospheric pressure and because gases tend to exhibit pulsed flow as they migrate up from the subsurface. Overall, emissions from the subsurface constituted only a small portion of total emissions from natural gas wells. Nevertheless, high soil fluxes at individual wells indicate compromised subsurface infrastructure, and monitoring of soil fluxes can help prevent future catastrophes.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A31M3109L
- Keywords:
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- 0322 Constituent sources and sinks;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0345 Pollution: urban and regional;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0478 Pollution: urban;
- regional and global;
- BIOGEOSCIENCES