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Evaluating the Impact of Reservoir Heterogeneity on the Performance of Underground Hydrogen Storage in Depleted Hydrocarbon Reservoirs

Ahmadi ShapourAbadi, Sara | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58702 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ayatollahi, Shahab; Mahani, Hassan
  7. Abstract:
  8. With the escalating global demand for clean energy, underground hydrogen storage has emerged as a pivotal solution for balancing renewable energy supply and demand and mitigating greenhouse gas emissions. Although recent studies have investigated hydrogen flow behavior in porous media, particularly within depleted gas reservoirs, most research has simplified geological structures by employing homogeneous models, thereby failing to comprehensively evaluate the impact of natural reservoir heterogeneity on storage performance. In this study, the GEM compositional simulator from the CMG software suite was utilized to investigate the combined effects of spatial heterogeneity in porosity and permeability distribution (homogeneous, log-normal, and two-layer models), reservoir geometry (cubic and anticline structures), and vertical-to-horizontal permeability ratio (ranging from 0.001 to 1) on key performance indicators, specifically hydrogen purity and ultimate recovery factor. In all scenarios, injection and production conditions were designed to be controlled and identical across repetitive cycles. The results indicate that heterogeneity, depending on its type and intensity, can either enhance or impair reservoir performance. Low permeability (5 mD) increased recovery to 68% by elevating bottom-hole pressure and concentrating flow near the wellbore, whereas high permeability (500 mD) facilitated gas dispersion, reducing recovery to 44%. Porosity variations primarily influenced storage capacity with minimal impact on flow paths. Neglecting mixing effects resulted in overestimations of purity and recovery by 5.4% and 3.4%, respectively. Furthermore, increasing the permeability anisotropy ratio from 0.001 to 1 intensified vertical hydrogen migration and mixing with resident gases, causing a decline in recovery by up to 19% and purity by 22%. Reservoir geometry and structural dip were found to have a more dominant influence on gas mixing and hydrogen recovery than heterogeneity alone. Additionally, increasing the number of cycles continuously improved purity and recovery by effectively displacing resident methane. Heterogeneity impacts varied significantly based on permeability distribution; the two-layer model yielded the highest recovery (77.82%) and purity (62.5%), while the log-normal model exhibited the lowest values (73.10% recovery and 59% purity) due to rapid hydrogen dispersion and enhanced mixing. These findings suggest that reservoir heterogeneity, if properly managed, can potentially bolster storage performance. By providing a comprehensive numerical framework and a detailed analysis of natural heterogeneity and reservoir geometry, this research represents a significant step toward the optimal design of underground reservoirs for cyclic hydrogen storage and establishes a practical foundation for future studies in the field of clean energy
  9. Keywords:
  10. Underground Hydrogen Storage ; Reservoir Heterogeneity ; Permeability ; Porosity ; Vertical to Horizontal Ratio ; Hydrogen Purification ; Hydrogen Recovery ; Numerical Simulation ; Anticlinal Reservoir

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