Gas sources migration paths, and seafloor seepage associated with marine gas-hydrates
Some continental margin sediments, like those on the Blake Ridge, are observed to have {ge}5% of their pore space occupied by gas hydrates. In situ microbial methane production is insufficient to form gas hydrate in these amounts, thus fluid migration and other gas-concentrating mechanisms are required to develop these gas hydrate accumulations. Several potential mechanisms exist. Some gas may be provided from deeper sediments by compaction and bubble distillation. Gas hydrate gas may be slowly recycled at the base of the gas-hydrate stability (BGHS) zone because of progressive subsidence and burial of the continental rise. Formerly stable hydrates will break down, and the methane released will migrate upward, re-enter the gas hydrate stability zone, and reform gas hydrate. Recycled gas will augment the gas produced in situ. Lateral gas migration may be focused along a relatively permeable conduit immediately below the BGHS. Gas may also migrate upward along faults or other permeable conduits and provide additional methane to form more gas-hydrate in sediments above the BGHS. Methane may escape onto the seafloor from faults that penetrate to the BGHS. Models of fluid movement will be assessed during ODP Leg 163.
- OSTI ID:
- 549170
- Report Number(s):
- CONF-950264--
- Country of Publication:
- United States
- Language:
- English
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