Influence of Submarine Mud Diapirs(Mud Volcanoes)on Gas Hydrate Accumulation
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摘要: 海底泥底辟(泥火山)与周缘发育的天然气水合物存在着密切的关联,表现在静态要素和动态成藏2个方面。作为一种重要而有效的运移通道类型,泥底辟(泥火山)携带的气体将是天然气水合物的重要气体来源。同时,含气流体沿着泥底辟(泥火山)的上侵,可能会导致上覆地层中温压场和地球化学组分的改变,进而引起天然气水合物稳定带厚度的变化。因此,泥底辟(泥火山)将控制天然气水合物的成藏,如位于构造中心部位的矿物低温热液成藏模式和位于构造边缘的矿物交代成藏模式。另一方面,泥底辟(泥火山)的不同演化阶段将对天然气水合物的形成和富集产生不同的影响。早期阶段,泥底辟(泥火山)形成的运移通道可能并未延伸到天然气水合物稳定带,导致气源供给不够充分;中期阶段,天然气水合物成藏条件匹配良好,利于天然气水合物的生成;晚期阶段,泥火山喷发带来的高热量含气流体引起天然气水合物稳定带的热异常,可能导致天然气水合物的分解,直至泥火山活动平静期,天然气水合物再次成藏。Abstract: There are close relationships between the submarine mud diapirs(mud volcanos)and their periphery gas hydrates orebody.The intrusion of gas-bearing fluid in the mud diapirs(mud volcanoes)can change temperature,pressure and geochemical characteristics of GHSZ,and thus should affect the formation and enrichment of gas hydrate.At the same time,as an important and effective migration channel type,the mud diapir(mud volcano)structure exerts methane which can also become an important gas source for gas hydrate.In addition,the mud diapir(mud volcano)have different effects on the formation and stability of the hydrate in the different evolution stages.The migration channel might not extend to the hydrate stability zone in the early stages of mud diapiric formation,resulting in insufficient supply of CH4.This is conducive to the formation of natural gas hydrates in the middle stage,because of good matching in hydrate metallogenic conditions.The abnormal heat in the hydrate stability zone,caused by high temperature gas-bearing fluid from mud volcano eruption,may lead to the decomposition of hydrates in the late stage.Until the quiet period of mud volcano activity,hydrate can form the reservoir again.There are two models of the formation of gas hydrates within a mud volcano:low-temperature hydrothermal process dominated around the central part of the mud volcano and metasomatic process dominated at the peripherical part of the mud volcano.
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Key words:
- mud diapir /
- mud volcano /
- gas hydrates /
- reservoir mechanism
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