Pliocene basin-floor fan sedimentation in the Bay of Bengal (offshore northwest Myanmar) |
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| Institution: | 1. UMR CNRS 5805 EPOC, Université de Bordeaux, Bâtiment B18, 33615 Pessac Cedex, France;2. Laboratoire des Sciences du Climat et de l''Environnement (LSCE/IPSL), UMR 8212 CNRS-CEA-UVSQ, Avenue de la Terrasse, 91198 Gif-sur-Yvette Cedex, France;3. Muséum national d''Histoire naturelle, 57 Rue Cuvier, 75005 Paris, France;4. Université Clermont Auvergne, CNRS, IRD, OPGC, Laboratoire Magmas et Volcans, F-63000 Clermont, Ferrand, France |
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| Abstract: | This study addresses reservoir development and hydrocarbon occurrence of the late Pliocene basin-floor fan deposits in the northeastern Bay of Bengal. The G-series turbiditic sandstones host dry gases, biogenic in origin, of three gas fields that are juxtaposed on the western flank of the NW–SE anticline. The gas reservoirs are stacked in back-stepping fashion being sourced from northwest as part of the Bengal fan. The Shwe field (Shwe fan) has an elongate fan-shaped morphology (12 km long and 4 km wide) and occurs about 30 km off the base of slope.The Shwe field reservoirs consist of two contrasting types of turbidite deposits, lower G5.2 and upper G3.2 reservoirs. The G5.2 is characterized by stacked lobe elements in which amalgamated and layered sheet sandstones provide an excellent vertical connectivity and high net-to-gross ratio (avg. 86%). On the contrary, the G3.2 represents overbank deposits, which is characterized by thin-bedded sandstones with low net-to-gross ratio (avg. 33%) as well as low-resistivity pays.Aside from the primary depositional framework, post-depositional modifications appear to have greatly affected Shwe fan, adding complexity in establishing a geological model. A line of evidence suggests that G5.2 lobe sands were injected into overlying G3.2, mostly in the form of sills. The injected sand beds measured from G3.2 cores account for 10 m, more than half of the total net sand. The sand injection is thought to be triggered by slumping that overpressured G5.2 lobes. Post-G3.2 erosional channel complexes incised into G5.2 and G3.2, ultimately diminishing gas pool extent as well as dividing Shwe fan into multiple compartments. |
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| Keywords: | Bengal fan Shwe gas field Lobes Sand injectite Pliocene turbidite Bay of Bengal Myanmar |
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