An integrated geomechanical–numerical simulation framework for fracture characterization and prediction in buried hills of the eastern south China Sea

Abstract: Buried hill reservoirs in the eastern South China Sea exhibit highly heterogeneous mechanical properties and complex fracture networks that exert significant control on reservoir productivity, fluid pathways, and wellbore stability. Their tectonic evolution, multistage deformation, and lithological diversity make traditional fracture prediction methods insufficient for supporting safe and efficient offshore drilling operations. To address these challenges, this study develops a new integrated framework that combines geomechanical analysis, finite-element numerical simulation, and multi-source geological and geophysical data to characterize fracture attributes and predict fracture behavior under present-day stress conditions. The workflow incorporates acoustic and imaging logging data, high-resolution seismic attributes, lithology-based mechanical property modeling, and 3D Mohr circle stress analysis. These datasets are used to construct a heterogeneous geomechanical model that captures the spatial variability of elastic and strength parameters across the buried hill. Numerical simulations are performed to evaluate the distribution of stress perturbations associated with structural relief and lithological layering, and to assess the likelihood of fracture initiation, propagation, and reactivation under different stress regimes. The results demonstrate pronounced variations in fracture intensity and failure potential both laterally and vertically. Zones near faulted structural highs exhibit locally elevated differential stress and shear strain concentration, leading to enhanced fracture connectivity and increased reactivation probability. In contrast, massive crystalline units and mechanically strong lithologies show limited deformation and lower fracture susceptibility. By integrating the simulated stress field with observed fracture indicators, the study identifies high-risk intervals with elevated risks of borehole collapse, drilling fluid loss, or induced fracturing, as well as fracture-favorable sweet spots that may enhance reservoir penetration and productivity. Furthermore, the framework provides quantitative guidance for optimizing well trajectories, selecting safe drilling windows, and improving well placement strategies in offshore buried hill settings. The results highlight the importance of incorporating geomechanical constraints into fracture characterization workflows to reduce drilling uncertainty and improve the reliability of fracture prediction models. This integrated analytical–numerical approach offers a robust and transferable methodology for evaluating fracture development in complex tectonic reservoirs. It provides practical insights into wellbore stability management, reservoir development optimization, and risk mitigation in the challenging geological environment of the eastern South China Sea. The proposed workflow can also be adapted to similar buried hill or basement reservoirs worldwide.

Keywords: fracture characterization; geomechanical modeling; finite-element simulation; buried hill reservoirs; in-situ stress analysis; south China Sea