Sequence Stratigraphy, Architectural Elements and Reservoir Potential of the Bengal Fan (Miocene-Pleistocene) in Offshore Northwest Myanmar

The Bengal fan, the largest submarine fan on Earth, has attracted extensive attention of petroleum geologists in recent years because of several large discoveries made in offshore Myanmar in the past decade. In our research, high-resolution seismic data acquired in offshore northwest Myanmar were analyzed to study sequence stratigraphy, architectural elements and reservoir potential of the Bengal Fan.

Seismic sequence stratigraphic analysis indicates that in the study areas, a typical depositional sequence in outer shelf and upper slope is mainly composed of LST (lowstand systems tract) canyons, TST (transgressive systems tract) sediments and HST (highstand systems tract) deltas. Whereas a typical depositional sequence in lower slope and basin-floor is mainly composed of LST deepwater depositional system, and TST and HST are condensed. Five depositional sequences were recognized in the Miocene- Pleistocene Bengal fan.

The analysis of seismic facies and seismic attributes indicates that deepwater architectural elements of the Miocene- Pleistocene Bengal fan in the study areas mainly include canyons, confined channel complexes, aggradational channel-levee complexes, individual channels, depositional lobes (i.e. sheet sands) and mass-transport complexes, which range in character from slope facies to basin-floor facies. Furthermore, confined channel complexes can be subdivided into entrenched channel complexes and offset stacked channel complexes according to their inner structure. And individual channels can also be subdivided into straight channels and sinuous channels according to their outer morphology.

Exploration results in adjacent blocks indicate that main reservoirs of the discoveries are the Pliocene depositional lobes (sheet sands) and channel-levee-overbank sediments. In our study areas, the analytic results of seismic facies, seismic attributes and acoustic impedance inversion indicate that channel complexes, depositional lobes and individual channels are probably sand-rich facies. And probable sandy levees are also recognized. The investigation of depositional evolution suggests that the Bengal fan experienced rapid progradation during the Miocene-Early Pliocene and gradual retrogradation during the Early Pliocene-Pleistocene. Controlled by the depositional evolution, the Early Pliocene channel complexes and depositional lobes have the best reservoir potential in the study areas.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California