Georesursy (Sep 2017)
The Question of Environmental Consequences at Horizontal Drilling of Shale Formations in Connection with Their Enrichment with Microelements
Abstract
Priority directions of horizontal drilling in shale formations in the USA (Bakken, Barnett, Monterey, etc.) are considered. Growth and further development of this type of drilling in the territory of shale plays of the USA and other countries, as well as productive horizons of the Western Siberia, was noted. With a fairly detailed coverage in the domestic and foreign literature of all the pros and cons of shale horizontal drilling projects, and in particular the negative environmental consequences of hydraulic fracturing, the problem associated with the high content of metals and nonmetals in shales and oils is practically not considered. A significant number of them belong to the category of potentially toxic microelements, dangerous for the habitat. The article presents the average trace elements content in the combustible and black shale from various basins of the world, the concentrations of a number of elements markedly exceeding in shale the clark content of clay rocks. High concentrations of a number of elements in the Kenderlik shale of the Republic of Kazakhstan, domanic deposits of the Volga-Ural oil and gas basin are shown, as well as some features of the distribution of radioactive elements and mercury in oils and shales. The release of toxic elements significantly increases with the thermal impact on the formation and some processes of hydrocarbon processing. In the case of hydraulic fracturing, it is possible that toxic elements from both shales and from the naphthides contained in them could be discharged to the environment. In the course of horizontal drilling, as with any other processes of impact on the reservoir, additional studies should be conducted to assess the microelements composition of the shale formations and the hydrocarbons contained therein for monitoring environmental processes.
