Thermal maturity of organic matter and type of kerogen of Mesozoic sediments, Aryskum depression

Abstract

This work is devoted to the study of the oil and gas source potential of the Mesozoic deposits of the Aryskum depression of the South Turgay oil and gas basin and aims to study the features of the geological structure, determine the facial-genetic type and degree of maturity of organic matter. Geochemical methods play an important role in assessing oil and gas source potential, one of which is pyrolytic core analysis to determine the type of organic matter and thermal maturity of the studied rock material samples. To achieve this goal, the results of pyrolytic analysis of stone material from Neocomian and Jurassic deposits were used. Analysis of geological and geophysical materials made it possible to trace the pattern of distribution over the area of oil and gas-bearing sandy layers and the underlying clay layers with high insulating properties in the Aryskum horizon. The results obtained show that the total organic carbon content ranges from 0.47 to 1.41 wt%. To establish the type of kerogen and its position relative to the zones of oil and gas formation, the Van Krevelen diagram was used in the coordinates of atomic ratios of the elemental composition of kerogen and its modification for pyrolytic data, indicating that the kerogen of the studied samples is a mixture of types I, II and III, facies-genetic the type of organic matter of which belongs to humic, humic-sapropelic, and the sedimentation conditions are coastal-marine environment in moderately reducing conditions.