Mapping of potential environmental risks associated to formation water in the Oriente Basin, Ecuador

Abstract

Formation water is the water produced jointly with oil as part of oil production process, which in Ecuador it is performed mainly within the Amazon region. Despite this region is highly vulnerable, due to its biodiversity and hydrological richness, formation water is produced in large volumes, contains toxic substances and receives limited treatment. This research determined the spatial distribution of the potential environmental risks associated to formation water chemical composition using geographic information systems to generate risk and vulnerability maps. Specifically, the objectives were 1) to analyze the chemical composition of formation water; 2) to compare formation water chemical composition between oil fields; 3) to determine the level of vulnerability of the environment and nearby populations; 4) to map the potential environmental risks associated to formation water; and 5) to review the current water treatment methods. Results show that formation water contains elements that are carcinogenic and with high bioaccumulation potential, like cadmium. Moreover, their concentration varies depending on the reservoir from where the water is extracted and the geographical location of the field. The potential risk of an area is determined by its well density, formation water quality and production volume, and the course of any nearby river. Therefore, Blocks 15 and 57 and the basin of the Aguarico River are associated to high environmental risk. Finally, water treatment process removes suspended solids and oil, while production chemicals slightly contribute to its toxicity. To track environmental potential risks, it is suggested periodical water quality evaluations of nearby rivers, similar environmental studies, and better land use planning by the local governments considering the potential risks associated to oil production activities.