Experimental determination of LDAR effect on fugitive methane emission reduction in urban natural gas distribution network

This paper reports the results of Leak Detection and Repair (LDAR) program performed on natural gas distribution network of Valiasr town in Isfahan province. The aim of this research was to determine the effectiveness of leak repairing on methane emission reduction. Leak detection was performed by flame ionization detector (FID) to obtain the hydrocarbon concentration in ppm. A TBS gas station, 7 major gas consumers, underground gas pipelines, 1829 regulators and 7549 counters were subjected to LDAR program. Various maintenance operations (including greasing, tightening, replacement and sealing) were performed on those localities emitting more than 5000 ppm. The emission rate of each facility was evaluated separately, before and after repairing procedures. Experimental results of a previous study on the same town were used to correlate leak concentration (ppm) to leak rate (L/min). The results of emission inventory development before LDAR revealed that 683,488 Sm3 of natural gas is annually leaked to the atmosphere. Regulators and counters were the main sources of such emission by 63% and 33%, respectively. Major gas consumers (i.e. hospital, stadium, residential complexes, etc.) hold 3% of the share, while fugitive emission from TBS station and pipelines were negligible. Emission evaluation was repeated after LDAR and showed that annual fugitive leakage was reduced to 330,330 Sm3. These findings suggest that 353,158 Sm3 of natural gas (equal to 5696 tCO2e of methane) could be annually preserved by implementing an LDAR program.