Structural features, prototype-basin reconstruction and petroleum exploration potential of the Bay of Bengal Basin

摘要

Satellite-derived gravity data processed by applying various image enhancement methods (filter,gradient and continuation) and cross-sections of standardized seismic reflection profiling, are used to analyse the tectonic features and dynamics of the Bay of Bengal Basin.Free-air gravity anomalies obtained by enhanced processing indicate that there are NW-trending fracture zones in the west, EW-trending faults in the Ninetyeast Ridge, and NE-trending linear structures in the east of the basin, which suggest the influence of sea floor spreading, ridge emplacement and 1ndian Ocean crust subduction, respectively.Based on the standardized seismic reflection profiling, gravity anomalies and strata thicknesses, the basin comprises five tectonic/stratigraphic units, and can be divided into five structural elements that are West Depression, 85°E Ridge, Central Depression, Ninetyeast Ridge and Rakhine Depression.Prior to the collision, the sedimentary framework was controlled by multiple isolated rises developed in the 85°E Ridge, in response to episodic eruption processes of the hotspot.The post-collisional sediments known as the Bengal fan sediments were not significantly affected by the ridge and the sediments continuously migrated southward during the Eocene to Miocene.Subduction of the Ninetyeast Ridge promoted the westward growth of the Andaman accretionary prism in the south (7°N-14°N) and controlled the evolution of the Rakhine Depression, Indo-Burmese Wedge and the depocenter of the Bay of Bengal Basin in the north (14°N-20°N).We restored the proto-oceanic basin stage (Later Cretaceous to Early Oligocene) and the remnant ocean basin stage (Later Oligocene to present) of the Bay of Bengal basin since the Late Mesozoic based on detailed marine geophysical investigations and geological evidence.The two main prototype-basins have different geophysical characteristics, structural features and tectonic evolution processes, which result in variations of source rock, traps, hydrocarbon accumulation processes and modes.We propose that source rock and traps might have been related in time and space.Apparently, the tectonic evolution of the basin controlled the formation and evolution of traps and reservoirs in the Bay of Bengal Basin.