GEOLINKS International Conference 2020, Book 1
ORE CONCENTRATIONS OF METALS IN NAPHTHIDES OF HYPERGENESIS ZONE: ASSESSMENT AND ENVIRONMENTAL ASPECT
Dr. Svetlana Punanova
The study examines the formation of secondary-altered crude oils associated with the processes of modern or ancient hypergenesis. As a result of geological processes during intense upward movement of the earth's crust, oil undergoes physical weathering, inorganic oxidation, washing out with water, biodegradation and sulfurization, and turn into heavy oils and hard bitumen. In zones of hypergenesis, the loss of light fractions occurs and the absolute concentration of trace elements (TE) associated with resinous-asphaltene components, such as V, Ni, Co, Mo, Cr, Cu, etc. sharply increases. In addition, oils absorb elements of variable valence (V, Fe, U) from low-salinity stratal waters. As a result of experimental studies on the interaction of oils with low mineralization waters, which are characteristic of hypergenesis zones, leaching of some elements (e.g., Zn) from oils and absorption of others from contacting waters (for example, concentrations of newly-formed organometallic compounds V and Fe increased by 1.3-12 times) were found.
The author utilized the method of neutron-activation analysis to study the content of TE in oils and natural bitumens of the Volga-Ural, Timan-Pechora, Kazakhstan, Tajikistan, and etc. Ore-level concentration values were found, for example: 180-1162 ppm for V and up to 100 ppm for Ni in the oils of the Melekess depression in Tatarstan, and 940 ppm for V and 130 ppm for Ni in the oils of Kazakhstan deposits.
Classification of oils by the content of “biogenic” elements V, Ni, Fe and by physical and chemical properties revealed significant differences of hypergene-altered oils in the general cycle of genesis of naphthides. Deposits of secondarily-altered oils are found in a wide stratigraphic range in oil and gas basins of various geostructural types in traps of the combined morphology – lithologically and tectonically shielded.
During the development of oil deposits that contain high concentrations of TE, it is necessary to take into account ecological aspects. The environmental aspect is due to the fact that many metals contained in oils – V, Ni, Cd, As, Hg, U, etc. belong to highly toxic compound chemicals.
naphthides, environment, ecological aspects, zones of hypergenesis, trace elements