Evaluation of the Organic Carbon Content in the Low-Permeability Shale Formations (As in the Case of the Khadum Suite in the Ciscaucasia Region)

The objective of the study is to evaluate the initial content of organic carbon, which is lost in the hydrocarbon generation and catagenesis. It is required for the reliable evaluation of source rock generation potential. The greater the differences between the contemporary and initial values of organic carbon, the greater the maturity of the source rock. Due to the catagenetic consumption of organic substance for the formation of hydrocarbons and non-hydrocarbon products, there is a reduction in the mass of organic substance during the catagenesis, and at every stage of transformation we deal with the residual concentrations. To restore the original values of organic carbon by the beginning of catagenesis, i.e. by the beginning of HC generation, we recommend using the conversion factors that take into account both the type and concentration of substance, as well as the catagenesis gradations, reached by the oil source deposits. As a result of calculations, it was determined that the original concentrations of organic carbon in Bajocian-Bathian clays is 2.73.12%, in the Aptian-Albian deposits – 3.9 to 4.4%, in the deposits of the Khadum suite – 3-5.5%. Due to that, the average hydrocarbon potential was increased 1.5-2 times. Based on the results of initial source rock state recovery, we have made a map of initial organic carbon content that allows us to give a reliable estimate of generation potential for the source rocks of the Khadum suite, and to determine the perspectives of hydrocarbon accumulations exploration in the low-permeability shale formations of Ciscaucasia.