Damage-integrated fracture prediction model for multi-stage fracture in deep carbonates: Application to the A Oilfield, Northern Tarim Basin

The deeply buried Ordovician carbonates in the Tarim Basin exhibit complex fracture superposition due to polyphase tectonics, challenging prediction due to sparse well data and deep reservoir heterogeneity. This study presents an innovative fracture prediction framework for deep carbonates by integrating damage deformation mechanisms. A confining pressure-dependent fracture predictive model was established via triaxial tests, acoustic emission monitoring, and modified Mohr–Coulomb criteria, explicitly incorporating damage deformation effects on fracture parameters. Through failure tests and numerical simulation on pre-fractured rock samples, a multi-stage fracture superposition algorithm was established to account for fracture accumulation from distinct tectonic events, applied to the A Oilfield in the Northern Tarim Basin for practical validation. By commencing with detailed fault interpretation in the A Oilfield, we reconstructed tectonic evolution characteristics and identified three major fracture-forming periods through integrated analysis. By integrating rock mechanics experiments, logging data, and seismic data, geomechanical models corresponding to different tectonic phases were constructed were constructed and utilized in stress field simulations, enabling dynamic integration of multi-stage stress field simulations and fracture parameter superposition analysis. The model predicts fracture linear density (0.1–1.5 m^-1) and aperture (0.5–2.75 mm) with 80 % consistency with FMI interpretations, outperforming traditional brittle models. For the A Oilfield, the results of fracture prediction directly guide the identification of high-potential exploration zones, as well as the evaluation of effective reservoirs. This study provides a mechanistic approach for deep carbonate fracture prediction, aiming to address the limitations of traditional models that overlook confining pressure effects and damage deformation. This approach not only enhances reservoir description accuracy in the A Oilfield but also offers a practical reference for similar deep carbonate basins worldwide.