A Simulator Based on Coupling of Reaction Transport Model and Multiphase Hydrate Simulator and Its Application to Studies of Methane Transportation in Marine Sediments

Methane emissions at seafloor are generally associated with the upward methane migration from the deeper sediments, partly from hydrate dissociation. The anaerobic oxidation of methane (AOM) occurring in the surface sediments acts as an important barrier to methane emissions, caused by the reaction between sulfate ions and dissolved methane molecules. However, the current hydrate simulators rarely consider the transport of sulfate and the subsequent AOM reaction. In this study, to investigate AOM effects in hydrate systems, a new simulator named Tough+Hydrate+AOM (THA) is developed by combining the reaction transport model (RTM) with the widely used Tough+Hydrate (T+H) simulator. The THA simulator is validated using the single-phase cases of the Dvurechenskii mud volcano in Black Sea since the results obtained are in good agreement with previous ones. This simulator is then applied to investigate the response of a hydrate reservoir offshore West Svalbard to seasonal seafloor temperature change and also to confirm its adaptability in multiphase hydrate systems. The results obtained suggest that the AOM filter efficiency is as low as 5%, meaning that the majority of methane released from hydrate dissociation in the deeper sediments will escape into the ocean. The THA simulator considering AOM is expected to be an important tool for assessing methane emissions caused by hydrate destabilization.