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TitreSeismic imaging a fractured gas hydrate system in the Krishna-Godavari Basin offshore India
AuteurRiedel, M; Collett, T S; Kumar, P; Sathe, A V; Cook, A
SourceMarine and Petroleum Geology vol. 27, 2010 p. 1476-1493,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20090228
ÉditeurElsevier BV
Documentpublication en série
Mediapapier; en ligne; numérique
Lat/Long OENS 81.9167 82.3333 16.3333 15.6667
Sujetshydrocarbures; gaz d'hydrocarbure; capacité de production d'hydrocarbures; gaz; hydrate; levés sismiques; topographie du fond océanique; topographie du fond océanique; combustibles fossiles; géologie marine; géophysique
Illustrationslocation maps; seismic profiles; tables; plots
ProgrammeHydrates de gaz, Caractérisation des Hydrates de gaz
Résumé(disponible en anglais seulement)
Gas hydrate was discovered in the KrishnaeGodavari (KG) Basin during the India National Gas Hydrate Program (NGHP) Expedition 1 at Site NGHP-01-10 within a fractured clay-dominated sedimentary system. Logging-while-drilling (LWD), coring, and wire-line logging confirmed gas hydrate dominantly in fractures at four borehole sites spanning a 500 m transect. Three-dimensional (3D) seismic data were subsequently used to image the fractured system and explain the occurrence of gas hydrate associated with the fractures. A system of two fault-sets was identified, part of a typical passive margin tectonic setting. The LWD-derived fracture network at Hole NGHP-01-10A is to some extent seen in the seismic data and was mapped using seismic coherency attributes. The fractured system around Site NGHP-01-10 extends over a triangular-shaped area of w2.5 km2 defined using seismic attributes of the seafloor reflection, as well as “seismic sweetness” at the base of the gas hydrate occurrence zone. The triangular shaped area is also showing a polygonal (nearly hexagonal) fault pattern, distinct from other more rectangular fault patterns observed in the study area. The occurrence of gas hydrate at Site NGHP-01-10 is the result of a specific combination of tectonic fault orientations and the abundance of free gas migration from a deeper gas source. The triangular-shaped area of enriched gas hydrate occurrence is bound by two faults acting as migration conduits. Additionally, the fault-associated sediment deformation provides a possible migration pathway for the free gas from the deeper gas source into the gas hydrate stability zone. It is proposed that there are additional locations in the KG Basin with possible gas hydrate accumulation of similar tectonic conditions, and one such location was identified from the 3D seismic datae6 km NW of Site NGHP-01-10.