An Effective Thermal Conductivity Model of Dual-Porosity Hydrate-Bearing Sediments with Random Fractures

The effective thermal conductivity (ETC) measures how efficiently heat moves through hydrate-bearing sediments (HBS). As such, it serves as a fundamental parameter in reservoir evaluation. To overcome the limitations of existing models that often neglect fractures, this study develops a dual-porosity ETC prediction model that couples fracture–matrix elastoplastic evolution with hydrate-occurrence-dependent conduction pathways. Compared with conventional single-porosity models, the proposed framework explicitly quantifies how stress-induced fracture closure and fracture geometry (e.g., aperture and inclination) influence macroscopic thermal transport. The model demonstrates outstanding predictive performance on the experimental data, with relative prediction errors confined to within ±4%, which confirms the model’s physical consistency and predictive accuracy. It also captures unloading hysteresis and irreversible compaction of hydrate-bearing sediments, with the unloading ETC recovered to a range of approximately 70% to 90% under various stress conditions, and the postunloading ETC remaining 2–20% higher than the initial value. The results show that fracture porosity, fracture aperture, fracture inclination, matrix compressibility, and preconsolidation stress jointly control ETC evolution. In addition, the case studies in this paper demonstrate that excess-gas systems exhibit consistently higher ETC (by ∼10–15%) and stronger stress sensitivity than excess-water systems. The derived ETC model enables a robust evaluation of the steady-state conductive heat transfer properties within the composite sediment framework.