توحيد سامي

With the increasing deman‎d for clean energy, underground hydrogen storage in geological formations has emerged as a key solution for managing the intermittency of renewable resources. However, the safety an‎d sustainability of such projects strongly depend on the integrity of the caprock, which may be compromised by discontinuities such as faults. The main objective of this study is to quantify the risk of hydrogen leakage through the fracture network within the fault damage zone of a caprock aquifer an‎d to conduct a sensitivity analysis on key geological an‎d operational parameters. In this research, a conceptual three-dimensional model of a saline aquifer was developed. To overcome the high computational cost of coupled simulations, the major novelty of this study lies in the development an‎d validation of a dedicated module in the MRST environment that enables accurate an‎d efficient simulation of the hydrogen–brine system using a black-oil formulation. The discrete fracture network (DFN) within the fault damage zone was generated based on credible empirical correlations, an‎d simulated using the Embedded Discrete Fracture Model (EDFM). Comprehensive sensitivity analyses were performed on the damage zone width, injection rate, molecular diffusion, an‎d water vaporization. The results indicate that the damage zone width as it indirectly controls fracture connectivity an‎d injection rate are the dominant factors influencing leakage, an‎d their increase leads to a sharp an‎d nonlinear rise in the final leakage volume. Temporal flow dynamics revealed two distinct flow regimes: “matrix-limited” an‎d “aquifer-limited.” A key finding of this study is that the leakage rate, after an initial rise, tends to oscillate around a specific value governed by the injection rate an‎d fracture intensity. Conversely, molecular diffusion was found to have a negligible effect on the overall mass balance. Additionally, including wet-gas behavior (water vaporization) did not alter the leakage volume due to viscosity-related effects. Temperature an‎d salinity were also examined, showing that lower temperatures an‎d higher salinity can intensify hydrogen leakage. Moreover, a considerable proportion of the injected hydrogen dissolves into the brine, leading to storage efficiency losses, whereas the role of diffusion an‎d wet-gas effects remains minor.

ذخيره‌سازي زيرزميني هيدروژن , ناحيه آسيب‌ديده گسل , شبكه شكاف گسسته , شبيه‌سازي به روش نفت سياه , روش EDFM

Underground hydrogen storage (UHS) , Fault damage zone (FDZ) , Discrete fracture network (DFN) , Black-oil simulation , EDFM method

Tohid Sami

Mohammad Taghi Sadeghi