GEOLOGICAL AND GEOCHEMICAL FEATURES OF AN OIL FIELD OF PRECASPIAN REGION

Abstract

This article highlights the geological and geochemical features of the oil field of the Caspian region of the territory of Kazakhstan. The ways of hydrocarbon migration, which were carried out in the direction of the southern steeper part of the Arystanov stage, are described. All the studies carried out over the previous years have shown that the composition of dispersed organic matter (kerogen) contained in Jurassic and Triassic sediments has a predominantly mixed, mixtinite composition. The factor causing long-range migration may be faults, including a high-amplitude fault in the junction zone of the Kosbulak trough with the Akkulkovsko-Bazaysky ledge and the Aral-Kyzylkum fault, to which the deepest parts of the Kosbulaksky and Barsakelmessky bends are confined, and rock fractures in various porous and permeable reservoir rocks can also serve. The presence of significant reserves of dry methane gas deposits in the Paleogene of the Akkulkovsko-Bazaysky ledge and the established manifestations of gas in the northern half of the Kyzyloysky shaft in Upper Cretaceous sediments are associated with their vertical and lateral migration within these ledges, including vertical along the faults. The unconformity surface at the foot of the Lower Jurassic sediments provides the development of organic life, plant growth, and clay residues deposited above these unconformities become good source rocks. According to all geochemical indicators, the Middle Jurassic rocks are oil-producing that are located in a favorable middle zone of mesocatagenesis. The main volumes of oil reserves discovered on the territory of Northern Ustyurt were found in the sediments of the Middle Jurassic. The results of geochemical studies in the future will allow basin modeling to be carried out with greater accuracy.