Geophysical Reservoir Characterization and Monitoring of CO2 Sequestration in the North Sea and Assessment of Hydrogen Storage Sites in the Gulf of Mexico region

This work aims to enhance reservoir characterization accuracy for improved gas storage, sequestration, and monitoring analysis. The first objective is to conduct a comprehensive reservoir characterization of the Volve Field in the North Sea utilizing petrophysical analysis and rock physics modeling. This involves integrating core data, well-log, and synthetic modeling to determine the key petrophysical properties of the subsurface reservoirs. By analyzing the porosity, permeability, lithology, and fluid saturation, the reservoir parameters vital for successful exploration and storage are determined along with associated potential risks. The research then predicts these petrophysical properties from seismic inversion attributes using machine learning techniques. Next, we investigate the impact of pressure and temperature on the acoustic properties of various gases. These properties are essential for understanding subsurface gas effects. Acoustic Resonance Spectroscopy is employed to measure gas velocities and assess the effects of pressure and temperature. Our findings reveal that gas velocities generally increase with increasing pressure and temperature. To understand the impact of pressure on gas behavior in sandstone reservoirs, ultrasonic measurements on gas-saturated sandstones were carried out. The results show that P-wave and S-wave velocities generally decrease with increasing pore pressure. Furthermore, we performed an in-depth study of CO2 injection monitoring in the Sleipner Field, North Sea, focusing on the Utsira Formation. The research leverages advanced time-lapse inversion techniques and 4D seismic data analysis to enhance the accuracy of volume estimations and provide a comprehensive understanding of the dynamic behavior of the injected CO2 plume. The analysis encompasses cross-correlation, time shift, predictability, and other key elements to yield robust insights into the reservoir's response to CO2 injection. Interpreted gas volumes from the seismic changes closely align with the injected volume, with a calculated-to-actual ratio ranging from 0.9 to 1.1. Lastly, we focused on hydrogen storage development in salt caverns exploring the suitability of salt formations for hydrogen storage and operations. Of the 144 evaluated domes, 26 were selected in the initial screening due to their favorable structural integrity and storage potential. In summary, this thesis provides geophysical techniques, measurements, and case histories to augment our understanding of gas reservoirs and their changes.