Measurements taken using aircraft point to high emissions during the drilling phase in the Marcellus shale formation

Institute of Environmental Physics, University of Bremen

Published: May 23, 2014

The article “Towards a better understanding and quantification of methane emissions from shale gas development”, by Caulton et al., published in the Proceedings of the National Academy of Sciences in April, 2014, presents methane emission estimates deduced from measurements taken using aircraft. These measurements were conducted in southwestern Pennsylvania in the region of the Marcellus shale formation, known for its high number of shale gas exploration sites. The measurements were taken in June, 2012 over 2 days.

The authors derive a regional methane flux of 2 –14 g CH₄ s⁻¹ km⁻² over an area of 2800-km², which does not differ statistically from a bottom-up inventory. They found that only 1% of the wells account for 4 – 30% of the regional flux. In addition, they measured unexpected high emissions at sites that were in the drilling phase.

The conclusions of this article are based solely upon two measurement days. Due to this short time span the derived regional flux should be regarded as a snapshot and not as a representative value. The study supports the findings of previous studies, that a small number of sites are responsible for a large fraction of the flux. The new and interesting point of this study is the identification of high methane emissions from wells during the drilling phase, a period that has not up to now been known for high emissions. Emissions during this stage need to be quantified in future more comprehensive studies.