| Author's Name: FENG Jiarui1, WEN Zhixin1, HE Zhengjun1, CHEN Xuan2, MENG Qingyang1,
MA Chao1, SU Ling1, WANG Yonghua1 |
| The Volga-Urals Basin is a typical foreland basin on the Eastern European Platform, accounting for a
significant proportion of global conventional and unconventional oil and gas reserves. However, the understanding of its
basin formation and reservoir accumulation remains limited. Through systematic investigation of geological data, the
evolution of the basin and its lithofacies paleogeographic characteristics are comprehensively analyzed based on the
sedimentary filling features during different Pre-Mesozoic geological periods. The results show that: (1) Under the
influence of different tectonic stresses such as tensional stress and compressional stress, the Volga Ural Basin underwent
tectonic evolutionary stages of extensional and compressional regimes, developing four prototype basin types/stages:
intracontinental rift, passive continental margin, back-arc depression, and back-arc foreland basin. (2) During different
tectonic evolution processes, the basin has undergone multiple-cycle changes from terrestrial to marine and back to
terrestrial. During the Meso-Neoproterozoic, the basin remained generally stable with sedimentation confined to its
eastern region, dominated by terrestrial clastic deposits; in the Early Ordovician, the opening of the Ural Ocean led to a
marine transgression across the East European Platform, characterized primarily by shallow marine carbonates; beginning
in the Devonian, the basin underwent multiple regressive-transgressive cycles; by the end of the Permian, the entire basin
was fully uplifted and subjected to erosion. (3) The basin developed four petroleum systems, with the Domanik Formation
serving as the primary source rock. The transitional facies and shallow marine facies developed during the transgressive
phase constitute two critical hydrocarbon reservoir units in the basin. Muhanovo-Erohovsk Sag and Kashan-Kama
Depression are respectively the key area for unconventional and conventional oil and gas exploration in the future. The
research findings provide a critical foundation for the evaluation of overseas oil and gas projects and the implementation
of exploration and development practices. |
