Numerical Modelling Research on the Mineral Alteration Due to the Methane Leakage at the Seabed

Abstract

In order to investigate the response of authigenic minerals to gas hydrate geo-systems, the biogeochemical processes and its induced mineralization were predicted by employing the comprehensive reactive transport modelling approach. On the available data basis, a 1-D vertical column model was built. Three cases with different upward methane flux rates were designed to investigate the effects of variations in the depth of sulfate methane transition zone (SMTZ) on the formation of authigenic minerals. The results indicate that the SMTZ depth is significantly influenced by the upward methane flux rate. During the simulations, oligoclase, k- feldspar, smectite-Na, smectite-Ca, chlorite dissolved. The AOM (Anaerobic Oxidation of Methane) reaction was strong at the interface, and the precipitation amount of calcite is large, which indicates that the formation of calcite at the interface is mainly controlled by AOM. When the methane leakage rate is 20 times higher than the basic case, aragonite starts to precipitate. During the simulation, oligoclase, k-feldspar, smectite-Na, Smectite-Ca, chlorite dissolved.