D.K. Azhgaliev, R.A. Valiullin, A.K. Gabbasova
Structural and tectonic features of structure and petroleum potential of deep-seated Palaeozoic horizons in Caspian Basin
Key words: Palaeozoic series; deposits; object; horizon; structure; mega-high; Caspian Basin; oil and gas occurrence; faults; prospecting.
For citation: Azhgaliev D.K., Valiullin R.A., Gabbasova A.K. Structural and tectonic features of structure and petroleum potential of deep-seated Palaeozoic horizons in Caspian Basin. Geologiya nefti i gaza. 2022;(2):79–93. DOI: 10.31087/0016-7894-2022-2-79-93. In Russ.
The high estimate of the predicted potential and low reserve replacement rates make it necessary to increase efficiency of prospecting activities by means of deep-seated Palaeozoic horizons studies and development at depths of 5.5–8 km In these circumstances, a positive result would allow for a multiple and short-term increase in oil and gas reserves and strengthening of the hydrocarbon mineral resource base. This work was aimed at prediction of large objects (highs and mega-highs) in the Palaeozoic series, namely, oil and gas traps with a considerable amount of information and accurate data accumulated for them. High prospectivity of the Devonian interval of the section and especially the Upper Devonian-Lower
Carboniferous part is substantiated by the example of representative large objects. The research tool was an integrated analysis of well, seismic, and geopotential field data, as well as features of Palaeozoic deposits depth structure, and patterns of fault tectonics. Comparative analysis of Palaeozoic series architecture in the section of northern, eastern, and southern flanks of the Caspian Basin was carried out. Evaluation of petroleum potential of Palaeozoic horizons taking into account new approaches to prediction of large exploration targets (massive syn-depositional uplifts and carbonate buildups) capable
of accumulating large scale oil and gas pools was carried out. Prospectivity of a new type of objects is substantiated; these are mega-highs defining regional areas and zones for efficient planning and deployment of prospecting, improving quality of forecasts, and discovering new hydrocarbon fields. Zones of large highs and mega-highs supported by the results of integrated data analysis are recommended for prospecting activities. Deep-seated faults most notably contributed to formation of large oil and gas fields at the depths 5.5–8 km and more; they played a role of feeding channels and defined the conditions necessary for accumulation of considerable (in terms of reserves) hydrocarbon pools. Area of the territory favourable for prospecting activities was expanded as a result of substantiation of high prospectivity of the relatively deeper subsea part of Palaeozoic Caspian Basin composed of terrigenous and terrigenous-carbonate sediments.