Analysis of structural deformation mechanism based on discrete element numerical simulation：a case study of the southern margin of the Junggar Basin

Influenced by multiple tectonic movements，the foreland thrust‑fold belt at the southern margin of the Junggar Basin exhibits segmented east ‑ west sections and north ‑ south zones，with deformation characteristics overlaid by vertical tectonic superposition. However，differing understandings of the tectonic deformation mechanism and styles in this area have hindered the depth of oil and gas exploration. To study the tectonic deformation mechanism and process of this area since the Neogene，this study utilizes high‑precision seismic，drilling，and rock mechanics data. Based on actual geological conditions，it focuses on the number，strength，and thickness variations of detachment layers，combining factors such as their vertical combinations，lateral distribu‑ tion ranges，syn‑sedimentary processes，and pre‑existing structures. Consequently，ten sets of models are designed，and comparative experiments are conducted using discrete element numerical simulation. The experimental results indicate that the strength，thickness，and combination of detachment layers control the vertical superposition relationships and structural styles of the thrust‑fold belt，while the distribution of detachment layers and syn‑sedimentary processes control the lateral deformation range. Pre‑existing structures affect the later‑stage inherited structural development. On this basis，multi‑factor combination simulation experiments are carried out in sections and compared with actual seismic profiles，reconstructing the deformation processes of the southern margin of the Junggar Basin and revealing the tectonic deformation mechanism since the Neogene. This mechanism involves pre‑existing faults，ancient uplifts，the vertical superposition relationship of three sets of slip layers with different nature，and syn‑sedimentary processes，which control the formation and evolution of the structures in the western segment. Two sets of vertical superimposed slip layers，which are strong and thin at the bottom as well as weak and thick at the top，control the formation and evolution of the structures in the central segment. Pre‑existing faults and a single set of weaker slip layers control the formation and evolution of the structures in the eastern segment. This method can provide a reference for similar areas with complex structural deformation. © 2024 Editorial office of Oil Geophysical Prospecting. All rights reserved.