METHANE GAS EMISSIONS - IS OLDER INFRASTRUCTURE LEAKIER?

Abstract:

Large gains in natural gas production from hydraulic fracturing is reinvigorating the US energy economy. It is a clean burning fuel with lower emissions than that of coal or oil. Studies show that methane (CH₄) leaks from natural gas infrastructure vary widely. A broader question is whether leak rates of methane might offset the benefits of combustion of natural gas. Excess methane (CH₄) is a major greenhouse gas with a radiative forcing constant of 25 times that of CO₂ when projected over a 100-year period.   An extensive field study of 250 wells in the Marcellus Shale conducted in July 2015 examined the emission rates of this region and identifed super-emitters. Spud production data will provide information as to whether older infrastructure is responsible for more of the emissions. Quantifying the emission rate was determined by extrapolating methane releases at a distance from private well pads using an inverse Gaussian plume model. Wells studied were selected by prevailing winds, distance from public roads, and topographical information using commercial (ARCGIS and Google Earth), non-profit (drillinginfo), and government (State of PA) databases. Data were collected from the mobile sensing lab (CH4, CO2 and H2O sensors), as well as from a stationary tower. Emission rates from well pads will be compared to their original production (spud dates) to evaluate whether infrastructure age and total production correlates with the observed leak rates. Very preliminary results show no statistical correlation between well pad production rates and observed leak rates.