Quantification of Methane Emission Rates from Unconventional Natural Gas Completion Activities

Increased oil and natural gas development in the United States has spurred concern about methane leak rates and their impact on global climate change. These concerns have fostered research efforts focused on quantifying methane emission rates. Much of the initial work has focused on basin-wide emission estimates giving an average leak rate per well or component-based emission estimates which can be scaled up to well pad leak rates.

In an effort to directly measure and quantify the variability of methane emission rates from development and completion activities, rates were quantified for a number of new unconventional natural gas wells in Garfield County, CO between 2013 and 2015. This work focused on the development and completion portion of new well construction which has a short duration when compared to the production lifetime of a well. Emission rates from such operations are not yet well quantified but have been hypothesized to be much greater than emission rates from producing wells. The project included measurements at a number of different geographic locations in partnership with three of the largest operators working with a number of different subcontractors and various emission controls within a region producing mainly dry natural gas from tight sand formations. Methane emission rates were measured from drilling, fracking, flowback, and simultaneous operations using the tracer ratio method. Rates varied by several orders of magnitude within operational categories with flowback showing the highest overall emission rates measured.