Numerical Modeling of Fluid Flow in Gas Hydrate Bearing Sediments in Black Sea

It is important to understand the stability, behavior and environmental effects of hydrates because gas hydrate reserves are being evaluated as potential energy sources of the future. Many studies have been conducted support that the Black Sea has suitable pressure and temperature conditions for gas hydrate formation, and it has been proven that there are signs of gas hydrate in marine sediments.  In this article, it is aimed to evaluate the effects gas hydrate-derived free gas (methane) found in Black Sea marine sediments and the chemical reaction of hydrate with groundwater over time by using a numerical modeling program. ANSYS Fluent, which is a computational fluid dynamics (CFD) program and works on the principle of finite volumes and whose suitability has been confirmed in past studies in fields with gas hydrate, was used as a numerical modeling program. For the purpose of numerical modeling, a previously collected and published depth-converted seismic reflection profile was selected as a reference model. This reference model includes the Bottom Simulating Reflector (BSR) seismic signature, which serves as a possible indicator of the presence of gas hydrates. Additionally, it incorporates a fault-like irregularity to examine its impact on the model. Through the simulations, the study will be investigated the fluid flow dynamics and the interaction between hydrate-derived free gas and groundwater within the model. The research will be focused on examining the temporal changes in the mass ratios of methane (CH₄) as well as the byproducts of this chemical reaction, namely carbon dioxide (CO₂) and hydrogen (H₂). In addition to the time-depend changes mentioned, the study also involves modeling the impact of the fault, which created discontinuities within the system, on the reactants and byproducts. The movement of these substances within the model, their accumulation within the sediment, and their dispersion or migration away from the model is presented. Simulation results show that dissolution time of methane and production time of carbon dioxide and hydrogen is strongly affected by the presence of faults, sea bottom morphology and initial rate of methane within marine sediments.