Hydrate-Based Carbon Dioxide Sequestration in the Black Sea: Implications for Turkiye’s Exclusive Economic Zone

Abstract

Abstract This study evaluates the potential for hydrate-based carbon dioxide (CO2) sequestration within Türkiye’s Exclusive Economic Zone (EEZ) in the Black Sea by mapping the CO2 Hydrate Stability Zone (CHSZ) and estimating storage capacities under different pore-water salinity conditions. CO2 hydrate equilibrium conditions were generated using the Hydrate Equilibrium Program (HEP), demonstrating that increasing salinity shifts hydrate stability toward higher pressures and reduces hydrate formation potential. CHSZ thickness maps were developed using spatial interpolation of hydrate stability data and revealed significant spatial variability, with the thickest hydrate stability zones occurring in deeper offshore regions. Monte Carlo simulations (5,000 realizations) were performed to quantify uncertainty in hydrate-based CO2 storage capacity using probabilistic distributions for key reservoir and hydrate parameters. For a pore-water salinity of 1 wt % sodium chloride (NaCl), the estimated storage capacity ranges from 587 MtCO2 (P90) to 2,111 MtCO2 (P10), with a median (P50) value of 1,154 MtCO2. Increasing salinity to 2 wt % substantially reduces the median storage capacity to approximately 125 MtCO2, highlighting the strong inhibitory effect of salinity on CO2 hydrate formation and stability. Sensitivity analyses indicate that sand fraction and hydrate saturation are the dominant controls on storage capacity uncertainty, followed by porosity. Comparison with current industrial emissions along the Turkish Black Sea coast suggests that the estimated offshore storage resource could accommodate decades of regional CO2 emissions under favorable conditions. The results demonstrate the significant potential of offshore hydrate-based carbon sequestration in the Black Sea while emphasizing the importance of accurate pore-water salinity characterization and site-specific investigations for future deployment.