Мінеральні ресурси України (Apr 2023)
Development of classifications of oil deposits by the content of metals (on the example of the Dnipro-Donetsk depression)
Abstract
The results of long-term geochemical studies of the content of metals: aluminum, mercury, chromium, manganese, iron, zinc, cobalt, nickel and vanadium are presented, as well as the total concentration of these metals and sulfur in oils from 36 deposits of the main oil and gas-bearing region of Ukraine – the Dnipro-Donetsk Basin. The purpose of the research was to develop a classification of oil deposits on the example of the Dnipro-Donetsk basin based on geochemical studies of metal content and their cluster analysis, which can be used as the strictest criterion for dividing them into two fundamentally different groups – deposits formed mainly by oils of biogenic origin and deposits that contain oil of essentially abiogenic generation. According to the results of the cluster analysis, natural classifications of these deposits were developed for the first time according to the listed indicators and the V/Ni ratio, which are presented in the work in the form of dendrograms. It is shown that according to the results of the cluster analysis, the sample mean values of the analyzed indicators, which differ significantly between individual deposits or groups of deposits in the established series, can be interpreted in the terminology of qualitative assessment as: abnormally low; low; below average; average; above average; high; abnormally high. The analysis of the research results and their interpretation in the genetic sense with comparison with three different geochemical criteria of the relationship of the origin of oil to abiogenic or biogenic sources of petrogenesis according to the existing ideas made it possible to establish, firstly, the deposits that, according to each of these ideas, belong to those formed mainly by abiogenic matter, second, to establish and analyze coincidences and differences in the list of these deposits. It is substantiated that the comparative analysis of the results of the clustering of the considered deposits by the content of such abiogenic elements as Al and Hg in the oils according to the results of their clustering by the concentrations of V, Cr and Co shows that the totality of the deposits belonging to the clusters with high and abnormally high content of V, Cr and Co differs from the list of deposits with high and abnormally high concentrations of Al and Hg only in the absence of the Yuryivskyi deposit, and they completely coincide with each other.Thus, high and abnormally high contents of V, Cr and Co in the oils of the studied fields, based on the logic of previous studies, can be used as a stricter criterion for dividing them into two fundamentally different groups – fields formed mainly by oils of biogenic origin and fields containing oil significantly abiogenic generation. In this regard, according to the previously established laws, it makes sense to consider as a criterion the selection of deposits with oil of essentially abiogenic origin besidesto the concentrations of V, Cr and Co, also ratios of Co/Ni and Cr/Ni.
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