POTENTIAL SOURCE ROCKS EVALUATION FOR THE PRE-SALT COMPLEX OF THE EASTERN EDGE OF PRECASPIAN BASIN

Abstract

Through basin analysis, the major tectonic stages and paleogeographic conditions of the formation of potential oil and gas source rocks of the subsalt complex of the eastern side zone of the Precaspian basin are considered. Prediction and localization of potential source rocks is critical for the Precaspian petroleum system understanding, both during petroleum play assessment at the prospecting and exploration stages. The generation and emigration potential of the oil and gas basin is determined not only by the concentration of the initial organic matter in the rock, but also by the type of kerogen. Based on Rock-Eval studies and comparative analysis with published biomarker data, the generation potential, genetic type and thermal maturity are analyzed depending on the age and structural relatedness of potential source rocks. A high generation potential has been established for the Lower Permian deposits, the occurrence of multiple generation foci controlled by the type and concentration of organic matter is predicted, which led to the formation of specific reservoirs of the "akzharite" type. The generation potential of the Visean-Bashkirian deposits is poor to average, catagenetic unconformities have been established within KT-II, KT-I, which indicates erosions, the total organic carbon (TOC) is 0.1-4%, the hydrogen index increases with depth, for samples enriched with TOC and with a content of S2 > 1, type II kerogen has been established, which it is an indicator of reducing marine environment. 2D basin modeling was performed in order to reconstruct the thermal evolution of potential source rocks and their thermal maturity and transformation ratio were modelled to determine the regional characteristics of hydrocarbon generation and migration. It is assumed that the formation and distribution area of the primary source rocks is associated with reducing conditions of the deep-sea shelf and continental slope and intensive subsidence in the Late Devonian-Lower Permian times. Conducting a comprehensive analysis of paleogeographic and paleotectonic conditions for the formation of potential source rocks is of key importance in the seismic interpretation and reconstruction of thermal history. 2D basin modeling was performed in order to reconstruct the thermal history of potential oil-producing strata and the degree of catagenetic maturity and the kerogen maturity index were estimated to determine the regional characteristics of hydrocarbon generation and migration.