Measurement of Trace Gases from an Unconventional Oil and Gas Development Site Using Mid-Infrared Dual Comb Spectroscopy

Abstract:

Unconventional oil and gas development is a significant source of emissions of both greenhouse gases like methane as well as higher carbon number volatile organic compounds (VOCs), which can substantially impact overall air quality. Understanding emissions from these sources has become increasingly important over the past decade as a larger fraction of energy extraction in the United States comes from these sites. While significant effort has been put into measuring methane emissions from different pieces of equipment such as compressors and well heads, as well as comparing average emissions from different basins, less research has been performed on emissions from different stages of bringing well pads into production and especially on emissions of VOCs.

Here, we present approximately eight weeks of methane and longer chain alkane measurements from three deployments covering all stages of bringing a well pad into production – drilling, hydraulic fracturing, mill out, flowback, and initial production – for a well pad located in the Denver-Julesberg basin outside of Denver, Colorado. These measurements were made with a mid-infrared dual comb spectrometer, a novel high-resolution, broad-band laser-based instrument that measures horizontal path-integrated data with high temporal resolution. The measurement paths ranged in length from 250-500 m and were located a few hundred meters past the sound walls of the well pad. This was the first deployment of this instrument, so we first compare our measurements against co-located point sensors deployed by the Colorado Department of Public Health and Environment (CDPHE) to validate our data. We then compare overall measured concentrations between the different stages of well pad development and find that for this well pad, the drilling and mill-out stages produced the largest plumes and most frequent plumes. Consistent with recent research, we find that large plumes are highly intermittent.