Geochemical searches of oil and gas deposits by concentration of aromatic hydrocarbons in surface sediments

The object of the research is the Tsentralno-Kustovoi site of Kogalimneftegas company (the Vateganskiy shaft at the joint of the Surgut and Nizhnevartovskarches) - a territory where search and prospecting drilling, extraction of hydrocarbon raw material is actively conducted. The researchproblem is to define the prospects of oil and gas presence at the Tsentralno-Kustovoi site. The solution of the problem is executed on thebasis of the analysis of anomalies of migrating aromatic hydrocarbons as these substances are alien to natural biosystems, and the modernvegetation practically does not render masking influence on them. In the course of research ground samples collected from the faceof explosive holes in the course of seismic prospecting performance at the Tsentralno-Kustovoi site were analysed. The depth of theexplosive holes was 7-10 m. For the petrogeological analysis of the geochemical zonality of hydrocarbons, a theoretical physical andchemical model of a deposit has been made. According to this model, spatial localization of anomalies of migrating hydrocarbons innear surface layers occurs over the water and oil contact. These anomalies, in case of a deposit contained by a closed local raise, have aring form and trace the external contour of the water and oil contact. As informative parameters total concentration of aromatic hydrocarbonsof groups mono-, bi-, three- and polyaromatic molecules with 4-5 condensed aromatic rings are accepted. The choice of aromatichydrocarbons as search geochemical signs was defined by the fact that these substances are alien to natural biosystems and modernvegetation practically does not render any masking influence on them. These substances are capable to accumulation on clay mineralsand keep mobility of hydrocarbons and ability to moving in heterogeneous geological environments. By results of laboratory researches,concentrations of naphthalenes, which are least of all sensitive to pollution by modern organic chemistry (in comparison withalcobenzols and phenanthrenes) and have essentially bigger concentrations (in comparison with polycyclic hydrocarbons), have beenaccepted as the prognostic parameter of perspective sites. On the scheme of the forecast of prospects of oil and gas presence three perspectivesites are allocated, two of which are confirmed by drilling. For the third predicted site the cut of a possible trap (deposit) isoffered. Basing on the received results of research, the use of data about the maintenance in near-surface deposits of heavy aromatichydrocarbons as search attributes on oil and gas is recommended.

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