M.N. Babasheva, V.N. Babashev, F.M. Kuanyshev, A.P. Pronin
Northern Ustyurt: zonal forecast of oil and gas occurrence
Key words: facies; source rock; oil source; paleostructure; tectonic activity; fault; migration; Upper Palaeozoic; Mesozoic; Play; formation of accumulation; model; prediction.
For citation: Babasheva M.N., Babashev V.N., Kuanyshev F.M., Pronin A.P. Northern Ustyurt: zonal forecast of oil and gas occurrence. Geologiya nefti i gaza. 2023;(2):53–61. DOI: 10.31087/0016-7894-2023-2-53-61. In Russ.
Topicality of the work responds to the low prospecting efficiency on the Northern Ustyurt, where the common methods of the territory potential are being used (identification of reservoir rocks, impermeables, modern troughs with bounding uplifts), as well as number of local structures prepared. There is an opinion that zoning of the modern structural geometries if the Mesozoic deposits plays crucial role in exploration object selection. In terms of exploration, ridge-like uplifts associated with troughs are the most attractive. This approach to evaluation of the territory potential cannot explain the trend in the discovered field occurrence, namely: all the identified accumulations follow south-eastern or roughly EW trending course. These directions in field occurrence over the area coincides with the extension of Upper Palaeozoic carbonate accumulation zones, including the Lower Permian-Carboniferous carbonate swell of south-eastern strike. This structure was first identified by the authors in the Northern Ustyurt from the study of rock material. Upper Palaeozoic oil accumulations were formed on the slopes of the swell; they became the oil sources for the Mesozoic pools discovered. Judging about the role of the Mesozoic in formation of the Jurassic oil accumulations showed that the Jurassic paleotectonic activity was a favourable basis for vertical oil migration from the Upper Palaeozoic rocks into the Jurassic traps was critical. The authors are the first to propose using paleogeographic and paleotectonic features as factors for identifying areas having high probability of new oil field discovery, which allows minimizing exploration risks. Map of oil and gas bearing areas is created for the Kazakhstani sector of the Northern Ustyurt, which takes into account the actual settings required for oil accumulation in Jurassic deposits, they are: position of most likely oil source; and mechanism of the Jurassic deposits contacting with an oil source.