The Pre-Caspian basin has a high oil and gas potential. The sedimentary cover is divided into three complexes – suprasalt, salt and subsalt. The most studied to date is the suprasalt complex. It has the largest number of industrial hydrocarbon accumulations.
The Pre-Caspian basin has been studied unevenly in area and in section. The central part is the least studied because of the thick sedimentary cover, which reaches more than 20 km. However, there are positive prerequisites for the discovery of new oil and gas fields in the subsalt complex.
Basin modeling and modeling of hydrocarbon systems are used nowadays to establish oil and gas potential. When using these methods, maps of the distribution of total organic content (TOC), hydrogen index (HI) and kerogen type over the studied region are the basis for determining the foci of hydrocarbon generation and a necessary element of any basin model. For their construction, the generation characteristics of the oil-producing strata are needed. For these purposes, the authors additionally investigated the core using the Rock-Eval method, selected from wells Embinskaya 9, Kozhasai PGS 1, Vostochny Akzhar 5, Karakulkeldy P 21. But geochemical parameters directly of the well core are always insufficient, they are distributed unevenly over the area and section, which significantly reduces the reliability and detail of the constructions.
Thus, the lack of analytical data on rocks in most of the territory does not allow us to single out oil and gas-producing rocks by area, however, according to the analysis of the physico-chemical properties and composition of oil, biomarkers for the fields of the Tengiz-Karaton zone and the South Embinsky uplift, the approximate age of the oil-producing strata is Devon-middle carbon, it gives reason to assume their wide distribution and good generation potential.
Based on the analysis of published data and conducted studies, four oil-producing strata were identified as the Middle Devonian, Upper Devonian, Lower Carboniferous and Lower Permian, maps of the distribution of Total organic carbon, hydrogen index and kerogen type were constructed for subsequent modeling of hydrocarbon systems.
1. Iskaziev K.O., Strategiya osvoeniya resursov nefti i gaza v podsolevykh otlozheniyakh severa Prikaspiyskoy sineklizy (Strategy for the development of oil and gas resources in the subsalt deposits of the northern Caspian syneclise): thesis of doctor of geological and mineralogical science, Moscow, 2021.
2. Iskaziev K.O., Khafizov S.F., Lyapunov Yu.V. et al., Pozdnepaleozoyskie organogennye postroyki Kazakhstanskogo segmenta Prikaspiyskoy vpadiny (Late Paleozoic organogenic structures of the Kazakhstan segment of the Caspian basin), Moscow: URSS, 2019, 250 p.
3. Miletenko N.V., Fedorenko O.A., Atlas litologo-paleogeograficheskikh, strukturnykh, palinspasticheskikh i geoekologicheskikh kart Tsentral’noy Evrazii (Atlas of lithological-paleogeographic, structural, palinspastic and geoecological maps of Central Eurasia), Almaty: Publ. of Research Institute of Natural Resources YuGGEO, 2002.
4. Akhmetshina L.Z. et al., Atlas paleontologicheskikh ostatkov permskikh otlozheniy severnogo i vostochnogo pribortovykh segmentov Prikaspiyskoy vpadiny (Kazakhstanskaya chast’) (Atlas of paleontological remains of Permian deposits of the northern and eastern marginal segments of the Pre-Caspian depression (Kazakhstan part)), Aktobe, 2013, 242 p.
5. Akhmetshina L.Z. et al., Atlas paleontologicheskikh ostatkov, mikrofatsiy i obstanovok osadkonakopleniya famensko-kamennougol’nykh otlozheniy Prikaspiyskoy vpadiny (Kazakhstanskaya chast’) (Atlas of paleontological remains, microfacies and sedimentation environments of the Famennian-Carboniferous deposits of the Caspian depression (Kazakhstan part)), Almaty, 2007, 476 p.
6. Zhemchugova V.A., Prakticheskoe primenenie rezervuarnoy sedimentologii pri modelirovanii uglevodorodnykh sistem (The practical application of reservoir sedimentology in the modeling of hydrocarbon systems), Moscow: Publ. of Gubkin University, 2014, 344 p.
7. Zhemchugova V.A., Myatchin O.M., Devonian reservoirs of oil and gas: Depositional environments, structure features, oil-and-gas bearing capacity (In Russ.), Vestnik Moskovskogo Universiteta. Ser. 4. Geologiya = Moscow University Geology Bulletin, 2015, no. 6, pp. 35–43.