SUBMARINE MUD VOLCANO AND ITS RELATIONSHIP WITH GAS HYDRATE

The coexistence of submarine mud volcanoes and their periphery gas hydrates illustrates the close relationship between them. Submarine mud volcanoes have been regarded as important exploration targets for deep-water natural gas hydrate in recent years. This paper deals with deep-water mud volcanoes from three aspects including morphology and internal structure, petrology characteristics of eruptions and ambient thermal anomaly. The mud volcanoes may vary in shape, and three kinds can be classified according to the shape of mud volcano crest:cone type, pie type and collapse type. Petrology of mud volcanic eruptions, of which composition is complex due to diverse sources, is significantly different to the abyssal sedimentary environment. The distribution of mud volcanoes, as a fluid dissipation structure, is commonly associated with faults, diapirs (mud diapirs or salt diapirs). The mud volcanoes often cause geothermal anomaly, which would affect the formation and occurrence of gas hydrate. The formation process of mud volcano related to a mud diaper could be divided into four stages:turtle back, pierce, eruption and collapse. Based upon the discussion above, the relationship between mud volcano and natural gas hydrate is analyzed. The results of the study suggest that the controlling effect of mud volcano over gas hydrate heterogeneity distribution, gas hydrate dynamic accumulation and its relationship with mud volcanoes, the coexistence of gas hydrate and conventional hydrocarbon controlled by mud volcanoes will become the main directions in future natural gas hydrate research.