Testing Methods for Determining Emission Rates via Controlled Field Experiments

The recent increases in oil and gas extraction have led to an increased need to characterize emission rates of VOCs from both new well development and production processes. In this work, we characterize the precision and accuracy of several methods of estimating these emission rates. Tests were conducted at Christman Airfield (Fort Collins, CO) by releasing a VOC proxy (methane) and a tracer gas (acetylene) at known flow rates; the concentrations of these gases were measured downwind using an SUV equipped with a PICARRO A0941 mobile measurement kit and a PICARRO G2203 analyzer (Picarro Inc., Sunnyvale, CA, USA) which simultaneously measures acetylene and methane concentrations. We estimate the emission rate of methane using a tracer ratio method and an inverse Gaussian plume modelling method. The estimated emission rates are compared against metered emission rates. Furthermore, we evaluate these emissions-inversion methods using a 3D fluid-dynamic model to test the sensitivities of the methods to different parameters. We present the results of these field and modelling experiments and provide suggestions for emission rate estimates in future studies.