ИСТИНА

The area of study includes large Astrakhan gas-condensate field and several smaller fields, such as Tabakovskoe and Elenovskoe, located on the slopes of Astrakhan dome and within Karasalskaya monocline (western slope of the Pre-Caspian depression). Within Astrakhan dome oil and gas hydrocarbons (flows, rims, bitumen inclusions, saturated in water) occur in the Middle Devonian – Lower Permian section in as wide range of areas within Astrakhan region (Astrakhanskaya, Pravoberezhnaya, Vysokovskaya, Devonskaya, Zavolzhskaya, Volodarskaya, Severo-Astrakhanskaya etc.). Key borehole logging tools for evaluating TOC% (total organic carbon) values in rocks are presented by gamma ray (GR) and neutron log (FCNL), which are common in all wells with geochemical core data. Gamma ray index (DGR) and Neutron index (DFCNL) were calculated for comparing geochemical parameters of core samples with logging interpretation data and then to matching the wells to each other. Reference levels for calculated curves were accepted by pure limestones values (DGK = 0, DFCNL=1) and domanikit’s/domanikoid’s curve values (DGK=1, DFCNL=0) with high radioactivity and high hydrogen content.