Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Deepwater (Slope and Basinfloor) Depositional Architecture and Evolution of the Northeast Bengal Fan (Miocene-Pleistocene) in Offshore Northwest Myanmar
(1) PetroChina Hangzhou Research Institute of Geology, Hangzhou, China.
Since the discovery of the Pliocene turbidites and the commercial Shwe gas field in offshore Myanmar in 2004, the northeast Bengal Fan, as part of the largest Bengal fan on Earth, has become the target of investigations. In 2008 and 2009, high-resolution 2-D and 3-D seismic data acquired in Block X1 and Block X2 in offshore northwest Myanmar were analyzed to study the depositional architecture, evolution and reservoir potential of the northeast Bengal fan.
In Block X1, seismic stratigraphic analysis indicates that the Pliocene- Pleistocene deposition is characterized by multiphasic stacked canyon fills, which are typical characters of upper slope facies. The canyon fills come from the northwest and are composed of multiphasic sediments, such as slumps, debris flows and so on. Besides the canyons, the discovery of shelf-edge deltas capping the canyon fills and trending northeast to southwest confirms the existence of provenance from the northeast inland Myanmar. In Block X2, deepwater depositional architectural elements interpreted from seismic stratigraphy and seismic attributes in the Miocene- Pleistocene stratigraphic interval mainly include confined channel complexes, channel-levee complexes, sheets, mass-transport complexes, and hemipelagic drape complexes, which range in character from slope facies to basinfloor facies. These architectural features reflect a combination of active (sediment input from channel systems) and relatively passive (slope failures and slumps) sediment supply systems in the study areas.
The investigation of depositional evolution in Block X2 suggests that the northeast Bengal fan experienced rapid progradation during the Miocene-Early Pliocene and gradual retrogradation during the Early Pliocene-Pleistocene. During the Miocene-Early Pliocene, deepwater architectural elements changed from hemipelagic drape complexes to confined channel complexes, channel-levee complexes, and sheets because of rapid progradation of the sediments. And then, these elements gradually evolved into smaller channel complexes, channel-levee systems, and hemipelagic drape complexes during the Early Pliocene-Pleistocene because of gradual retrogradation of the sediments. Controlled by the depositional evolution, the Lower Pliocene channel complexes and sheets are the best reservoir targets in Block X2; besides, the Upper Pliocene and the Upper Miocene are also likely to develop good quality reservoirs.