Monitoring and Investigating Methane Leakage in Coal Gas Production

Abstract

The Qinshui Basin in Shanxi Province in northern China is currently the largest production area of coal bed methane (CBM) in China. For this study, methane (CH 4) measurements were collected from 113 wellheads to determine primary gas leakage locations. The results indicate that the leakage is primarily from water outlets and tubing; three leakage points accounted for 95.79% of the total measured gas. With respect to measurement variability, the standard deviation for gas measurements of the tubing was the largest at 12.28. Wells with good geological conditions and scientifi c management exhibited very low leakage. In contrast, wells with unfavorable geological conditions and improper management had much higher leakage values. The standard deviation of leakage at the water outlets was the next lowest. The role of different processes and running states had the greatest role in CH 4 leakage. The leakage from horizontal wellheads was the highest, with an average rate of 20.80 l/min, compared to the average of leakage from fl owing wells at 0.88 l/min; this is far below that of the wells that used mechanical gas pumping. T he overall emission factor of the 113 examined wells was 176 kg CO 2-e t-1 , which was far greater than the previously reported Australian emission level (11.7 kg CO 2-e t-1).

Three considerations for modeling natural gas system methane emissions in life cycle assessment

“…Our primary goal is to illustrate current status and discrepancies rather than to provide a set of recommended values. We do, however, incorporate synthetic insights from the many recent studies that have estimated leakage outside the context of life cycle inventories (Abrahams et al, 2015;Allen et al, 2014Allen et al, , 2013Alvarez et al, 2018;Balcombe et al, 2018;Brandt et al, 2014;Ge et al, 2016;Hendrick et al, 2016;Jeong et al, 2014;Jiang et al, 2011;Karion et al, 2015Karion et al, , 2013Lavoie et al, 2017;Littlefield et al, 2016;Mitchell et al, 2015;Pétron et al, 2014;Phillips et al, 2013;Zimmerle et al, 2015).…”