Methodology For Minimizing Environmental Impacts During A Seismic Survey By Applying An Ecological Avoidance Program

摘要

Total Exploration and Production Uganda undertook a 3D seismic survey in Exploration Area 1/1A lying within the Murchison Falls National Park inhabited by many species of wildlife. During the seismic survey, an ecological avoidance program was applied to; i). Scout and map all sensitive features within the seismic footprint, ii). Avoid impacts on sensitive features and maintain their ecological integrity, iii). Proactively demonstrate sustainable oil & gas extraction in a sensitive ecosystem. A mitigation hierarchy of; Avoidance, Minimization, Restoration and Offsetting residual impacts was followed to limit ecological impacts. In this paper, we focus on Avoidance, presented as a model for future seismic or other intensive operations in similar sensitive ecosystems. This involved systematic surveys of predefined seismic lines for sensitive features, mapping locations of features, sensitizing Seismic crews, and on-ground supervision of Avoidance implementation. A total of 25,484 features such as; lekking grounds of ungulates, clay-licks and wallows were mapped along approximately 3300km in total of seismic lines surveyed. Out of 25,484 features mapped, 10,169 significant features were sorted, from which 678 features were sampled and revisited after seismic operations to assess compliance to Avoidance. Out of 678 features revisited, only one, a burrow was found to be impacted upon, having a tyre mark depression implying it was trampled by a vehicle. Three other burrows were found filled with soil, but with no indication of whether this was due to anthropogenic or natural occurrence. Five hundred and twenty features were found to have signs of animal activities such as; footmarks and physical presence of animals, including birds, indicating continued use of the features after seismic operations. The results indicate compliance by Seismic crews, suggesting that the Avoidance Mapping Procedure is an effective impact mitigation measure especially in such sensitive ecosystems. No such intensive seismic operation had been undertaken before in such a sensitive ecosystem. Some impact minimization measures used such as cable-less seismic data acquisition were implemented for the first time in Africa during these surveys. The Avoidance Mapping Procedure designed and applied was as well therefore the first of its kind, and provides an extensive knowledge, technicalities and experience in avoiding and minimizing impacts during seismic operations in such sensitive ecosystems.