Scientists from the Space Research Institute of the Russian Academy of Sciences (RAS) and Payne’s State Policy Institute with the Colorado School of Mines developed a new methodology for assessing the amount of flared associated petroleum gas (APG) with the help of satellite data. This system allows for much more accurate measuring the emissions opening the opportunities for more accurate climate monitoring and controlling the level of discharging international obligations to stop routine flaring.
Associate gas flaring at oilfields is a commonly used but absolutely ecologically unfriendly method of utilization. As a rule, the precise amounts of flared APG are not known, because operators very seldom account them, and in case there is certain reporting, its reliability often leaves the public asking questions. Meanwhile, this data is required for calculating the carbon footprint, for searching the locations for APG utilization газ, and for identifying the emergency situations, when the flares fail and methane is emitted directly into the atmosphere.
For over a decade, calibration based in annual reports by Cedigaz international organization was used to assess the amounts of flared APG. However, this method has serious drawbacks: wide-spaced errors and using unchecked empirical factor (0.7), which artificially “compressed” the data. This resulted in systemic mistakes: understatement of the amounts for major flares and overstatement – for minor ones.
To solve this problem, the researchers conducted a unique experiment. At the test facility of John Zink company in Oklahoma they performed 36 controlled gas fires. They precisely regulated the consumption of fuel (from small to very big one), the configuration of the flaring units (a single flare and two flares with 100 meters distance between them). They were registering the experiment with ground-based radiometers, spectrometers and cameras. The key element of the experiment was synchronizing the fires with the flight of Suomi NPP satellite equipped with VIIRS device capable of registering thermal radiation of flares in the infrared band even at night.
The analysis showed that the previously used factor was no longer needed. The new calibration based on direct measurements identified on ordinary linear dependency between gas consumption measured on the ground and thermal radiation in the air registered by satellite. It also became clear that signals from several adjacent flares are summarized in one pixel allowing for correct defining the common amount of flared gas. Atmospheric adjustment was a significant step forward: accounting for the effects of humidity and cloud cover, which are especially common for tropical areas, allowed for eliminating deviations and improving the accuracy of assessment in such regions as Venezuela, Indonesia and Nigeria.
Overall, the new methodology proved to be 70 times more accurate than Cedigaz calibration. The scientists also defined the minimal amounts for the satellite to steadily register the flares – 0.008 mln standard cubic meters of gas per day. The plan is to use the super-sensitive VIIRS channel for weaker signals (this channel was initially designed to monitor urban lights at night).
