Unlocking Hydrocarbon Potential: Petroleum Perspectivity Evaluation of the Jurassic Petroleum System, North Ustyurt Basin, Kazakhstan

Abstract Objectives/Scope The main objective of this study was to develop and analyze a basin and petroleum systems model (BPSM) to investigate potential reasons for previous unsuccessful exploration campaigns in the North Ustyurt Basin, an intracratonic basin with Mesozoic-Cenozoic infill of West Kazakhstan. With this 2D BPSM we aim to improve our understanding of the Jurassic petroleum system to evaluate its hydrocarbon potential and reduce exploration risks Methods, Procedures, Process Thermal history calibrated to vitrinite reflectance was reconstructed using 1D BPSM to assess timing of expulsion. Hydrocarbon charge was simulated in quick look 2D BPSM, while risk assessment accomplished with a commercial exploration risk, resource, and value assessment software, generating multiple Monte-Carlo simulations. The following petroleum system components and processes were assessed: trap, seal, source, reservoir and migration. Reservoir and fluid properties were obtained from interpretation of well data, while seismically derived maps were used to assess trap geometry. Timing of trap formation and charge as outputs of paleo reconstruction with Geological Chance of Success (GCOS) maps were used to evaluate and rank identified prospects. Results, Observations, Conclusions The principal source rocks of the region are enclosed within the Early-Middle Jurassic, showing the highest organic richness and sufficient maturity levels at the most subsided central part of the basin. According to BPSM results, Early Jurassic source rocks have reached the wet gas to gas window, while Middle Jurassic rocks reside in the main oil window. Significant burial during the Early Cretaceous resulted in hydrocarbon expulsion from the two Jurassic source rocks and also improved the sealing efficiency of the Jurassic cap rocks indicating favorable timing for the petroleum systems. This was taken as the main criterion to assess the charge probability when evaluating and risking the prospects. Five main prospects within the basin surrounding the main kitchen area were identified. The kitchen and migration pathways were numerically simulated to assess the overall potential of each prospect accounting risk factors to calculate GCOS. Final resources vs. GCOS values summarize geological uncertainties identified in this study. According to the outcome the main exploration risk in the region is related to availability of traps and the timing relationship of trap formation and hydrocarbon expulsion. Novel/Additive Information The geology and reservoir characteristics in combination with the distribution of potential source beds, timing of hydrocarbon generation, geochemical evidence for migration, and chances of preservation were used to rank the potential of Jurassic stratigraphic intervals in different parts of the basin. The results emphasize the potential of Jurassic source rocks and provide critical insights for further continued petroleum exploration in the North Ustyurt Basin.