Satellite survey of gas flares: development and application of a Landsat-based technique in the Niger Delta

Abstract

Pollution from oil and gas exploitation in the Niger Delta has greatly endangered the natural ecosystem, with gas flaring identified as a key agent of environmental pollution in the region. Efforts to evaluate the impacts of flaring on the surrounding environment have been hampered by limited access to official information on flare locations and volumes; hence, an alternative method of acquiring such information is needed. This article describes the development and application of the Landsat Flare Detection Method (LFDM), based on the combination of the near-, shortwave, and thermal infrared bands of Landsat imagery. The technique was validated using a reference data set of flare locations interpreted from aerial photographs, achieving a user accuracy of 86.67%. The LFDM was applied to a time series of imagery (1984–2012 inclusive) to obtain a long-term flaring history of the region; 303 flares (251 onshore and 52 offshore) were detected over the study period. The spatiotemporal distribution of these flares corresponds to known variations in oil and gas activities in the region. There was considerable variation between states in the trajectories of gas-flaring activity and the proportion of onshore vs. offshore flaring, which indicates substantial spatiotemporal variations in the environmental impacts of this industry. The LFDM builds upon existing methods of flare detection, which were based on moderate-resolution imagery, by offering increased precision of flare location estimates, improved objectivity, accurate identification of onshore and offshore flares, and a long flaring history. The LFDM is an efficient and cost-effective method that can provide local- to regional-scale information, which is complementary to that derived from other remote methods of flare detection and ground-based surveys. It could thus be used for backwards (flare history) and/or forwards (monitoring) surveys, especially in monitoring the country’s progress towards the recently set 30% flare reduction target by 2017.