Purdue and Cornell University scientists found high levels of the greenhouse gas methane above shale gas wells at a pre-production point not thought to be an important emissions source.  The findings could have implications for the design of gas well drilling sites and evaluation of the environmental impacts from natural gas production.  Letting natural gas escape unsold is serious enough, but letting it escape into the atmosphere is not a good idea at all.

The study, which is one of only a few to use a so-called “top down” approach that measures methane gas levels in the air above wells, identified seven individual well pads with high emission levels during the drilling stage.

The high-emitting wells made up less than 1% of the total number of wells in the area and were all found to be in the drilling stage, a pre-production stage not previously associated with significant emissions.

Paul Shepson, a professor of chemistry and earth atmospheric and planetary sciences at Purdue who co-led the study with Jed Sparks, a professor of ecology and evolutionary biology at Cornell said, “These findings present a possible weakness in the current methods to inventory methane emissions and the top-down approach clearly represents an important complementary method that could be added to better define the impacts of shale gas development. This small fraction of the total number of wells was contributing a much larger large portion of the total emissions in the area, and the emissions for this stage were not represented in the current inventories.”

Purdue Cornell Airborne Natural Gas Sniffer Rig. Click image for more info.

Purdue Cornell Airborne Natural Gas Sniffer Rig. Click image for more info.

The researchers flew above the Marcellus shale formation in southwestern Pennsylvania in the Purdue Airborne Laboratory for Atmospheric Research, a specially equipped airplane. The aircraft-based approach allowed researchers to identify plumes of methane gas from single well pads, groups of well pads and larger regional scales and to examine the production state of the wells.

“It is particularly noteworthy that large emissions were measured for wells in the drilling phase, in some cases 100 to 1,000 times greater than the inventory estimates,” Shepson said. “This indicates that there are processes occurring – e.g. emissions from coal seams during the drilling process – that are not captured in the inventory development process. This is another example pointing to the idea that a large fraction of the total emissions is coming from a small fraction of shale gas production components that are in an anomalous condition.”

The estimated bottom-up inventories have been produced from industry measurements of emissions from individual production, transmission and distribution components and then scaling up to create an estimate of emissions for the region. However, with thousands of wells, and a complex processing and transmission system associated with each shale basin, obtaining a representative data set is difficult, he explained.

A paper detailing the results has been published in the Proceedings of the National Academy of Sciences. The David R. Atkinson Center for a Sustainable Future at Cornell University funded this research.

“We need to develop a way to objectively measure emissions from shale gas development that includes the full range of operator types, equipment states and engineering approaches,” Shepson said. “A whole-systems approach to measurement is needed to understand exactly what is occurring.”

Shepson concluded the study results fairly.  But the press release leaves a lot to be desired in accurately describing the issue.  Production from completed wells looks to be quite well contained, which is where almost all the natural gas flows, much to the relief of production companies, consumers and environmentalists.

Drilling a well borehole is going to release some natural gas.  Drilling rig operators could do better in capturing the gas.  And its a certainty that drilling operators are using “gas sniffers” to identify gas finds.  But the natural gas has been forming and creeping through the ground for millions of years and while drilling on the way down there is always a chance a bit of gas trapped out of place is going to get dinged and flow.

The Marcellus formation is a huge, old and already fractured rock structure that’s been leaking the entire time since its formation.  In some places a water well will release a bit of natural gas as famously seen in attempts to frighten folks.

One way or another, eventually most of the natural gas underground is going to get into the atmosphere someday.  It might be best to use it with the CO2 allowed back into the natural carbon cycle.

For now the scientists have IDed a noticeable source of natural gas emissions and the well owners are sure to bring pressure on drilling rig operators to hold the gas in for sale instead of escaping.

Thanks are sent to the Purdue and Cornell University scientists and the David R. Atkinson Center for the financial backing.  We know a lot more now than before the team ran the research.


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