Ecological Consequences of the Development of Shale Formations Containing Toxic Elements

Abstract

Abstract—The average concentrations of trace elements, including toxic elements, in shales from various shale basins of the world are reported. The concentrations of a number of elements significantly exceeding the Clarke numbers for clay rocks in the Kenderlyk shale of the Republic of Kazakhstan, in the Domanic sediments of the Volga–Ural oil and gas bearing basin, some American formations (Barnett), etc., were noted. It was demonstrated that the concentrations of potentially toxic elements in many deposits were higher than their average values in clays and other sedimentary rocks. The release of potentially toxic elements into the environment significantly increased as a result of thermal effects on the formation, which can occur on the development of similar deposits of fossil fuels and in some hydrocarbon conversion processes. This was confirmed by natural observations and laboratory studies. On the hydraulic fracturing, which is widely used in the development of shale formations by the horizontal drilling method, toxic elements from both shales and their naphthide components can be released into the environment. In the development of shale deposits, additional studies are required for the monitoring of the trace element composition of shale formations to exclude environmental risks.