Geological structure analysis of the Zhetybay south field

Background: This study addresses the need to refine the block structure of the Triassic sequence in the Zhetybay South field, with a focus on the hydrocarbon productivity of the T₂V horizon, which is associated with Middle Triassic deposits. By integrating legacy geological and geophysical data with modern 3D seismic survey results, the analysis provides an updated interpretation of the structural framework and highlights the exploration potential of the target interval. Aim: This paper investigates the geological framework and hydrocarbon potential of the Triassic succession in the Zhetybay South field. Drawing on both legacy and recent data—from exploratory and production wells to 3D seismic surveys – the study synthesizes results from four reserve estimation campaigns conducted in 1972, 1983, 2010, and 2023. Particular emphasis is placed on reassessing the productivity of the T₂V horizon. Materials and methods: The primary data sources include well testing and perforation results, along with 3D seismic surveys conducted at the field in recent years. Results: The structure of the Triassic sequence has been refined, including the reflective horizon T₁o_bot, which hosts the T₁V accumulation. The presence of a potential oil and gas condensate accumulation within the T₂V horizon has been identified and confirmed by testing results from productive intervals. Conclusion: The integration of new 3D seismic data has enabled the revision of structural maps, clarification of the T₁V accumulation’s structural setting, and identification of a block-faulted framework. In the Nоrmaul Arch area, additional 3D seismic acquisition is recommended to improve fault mapping. A structural map of the T₂V horizon has also been developed, providing further support for its productivity. Since reservoir contacts are currently assumed, delineation of the accumulation’s potential extent remains necessary. Following these efforts, an operational reserve estimation for the T₂V horizon is recommended.