Discovery of natural methane hydrate in deepwater sediments in the east-coast of India
have generated significant interest in recent times. This work puts forward a possible
relationship of multi-TCF gas accumulation through destabilization of paleo-hydrate in
Plio-Pleistocene deepwater channel sands of Krishna-Godavari basin, India. Analysis of
gas in the study area establishes its biogenic nature, accumulation of which is difficult
to explain using the elements of conventional petroleum system. Gas generated in
sediments by methanogenesis is mostly lost to the environment, can however be
retained as hydrate under suitable conditions. Longer the time a layer stayed within the
gas hydrate stability zone (GHSZ) greater is the chance of retaining the gas which can
be later released by change in P-T conditions due to sediment burial. P-T history for
selected stratigraphic units from each well is extracted using 1-D burial history model
and analyzed. Hydrate stability curves for individual units through time are generated
and overlain in P-T space. It transpired that hydrate formation and destabilization in
reservoir units of same stratigraphic level in different wells varies both in space and
time. Presence of paleo hydrates is confirmed by the occurrence of authigenic carbonate
cement and low-saline formation water. We demonstrate how gas released by hydrate
destabilization in areas located at greater water depths migrates laterally and updip
along the same stratigraphic level to be entrapped in reservoirs which is outside the
GHSZ. In areas with isolated reservoirs with poor lateral connectivity, the released gas
may remain trapped if impermeable shale is overlain before the destabilization of
hydrate. The sequence of geological events which might have worked together to form
this gas reservoir is: deposition of organic rich sediments → methanogenesis → gas
hydrate formation → destabilization of hydrate and release of gas → migration and
entrapment in reservoirs.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/1065 |
| Date | 07 1900 |
| Creators | Kundu, Nishikanta, Pal, Nabarun, Sinha, Neeraj, Budhiraja, IL |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | text |
| Rights | Pal, Nabarun |
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