Subsurface saline aquifers are widely regarded as promising option for CO2 sequestration. In this approach, CO2 is injected into deep and porous rock formations, beneath an impermeable caprock, where it is stored for long-term as supercritical fluid. This process helps mitigate anthropogenic emissions by securely trapping CO2 underground. However, several challenges must be addressed before initiating sequestration operations begin, including effective site selection and thorough reservoir characterization. These factors are crucial to ensuring both the safety and long-term viability of the storage site. Reservoir characterization is particularly challenging due to limited subsurface data, parameter uncertainties, and intricate geological conditions.
Three saline aquifers have been identified in the subsurface of the northern Negev. The lower aquifer consists of the Permian-Triassic Negev and Ramon groups, while the middle aquifer includes the lower to middle sections of the Jurassic Arad Group. A thick aquitard separates these aquifers, acting as a top seal for the lower aquifer and a bottom seal for the middle aquifer. The upper saline aquifer lies within the Lower Cretaceous Kurnub Group. Likewise, the middle and upper aquifers are isolated by another substantial aquitard.
The unit’s properties, such as lithology, thickness, porosity, and permeability, are derived from borehole data, while its depth is determined from seismic surveys. To estimate total storage capacity, challenges like sparse data availability and data interpolation are addressed. Storage capacity is directly influenced by the supercritical CO2 density, which depends on subsurface thermophysical conditions, thus, uncertainties in temperature and pressure were also evaluated.
Key four-way closure anticlines, identified from the top Zohar Formation structural map, were analyzed, and storage capacity ranges were calculated for each. Threshold criteria considering capacity, injectivity, retention, geomechanical risk, and economic constraints, were applied to exclude less suitable structures and identify the most promising anticlines.