Deep-water depositional architecture and sedimentary evolution in the Rakhine Basin, northeast Bay of Bengal

Abstract

Since the consecutive discovery of several gas fields from 2004 to present, the Rakhine Basin has been an active area for petroleum exploration in the Bay of Bengal. High-resolution 3D seismic data and well data from blocks AD1, AD6 and AD8 offshore northwest Myanmar are used to study the Miocene-Pleistocene depositional architecture and sedimentary evolution in the Rakhine Basin. Analysis of seismic facies and seismic attributes indicates that deep-water architectural elements include submarine canyons, confined slope channel complex systems, aggradational channel-levee complexes, isolated channels, frontal splays and mass-transport complexes, which have variable characters (shape, dimension, sedimentary architecture) within predominantly background deep-water slope-basin floor facies. Most of the sediments are interpreted to be sourced from the Ganges-Brahmaputra fluvio-deltaic system to the north with only minor lateral input from the Indo-Myanmar Ranges to the east. Investigation of the depositional evolution and architectural elements transformation during the filling history of the Rakhine Basin suggests the Rakhine Basin experienced rapid progradation during the Oligocene-Middle/Upper Miocene, gradual retrogradation during the Middle/Upper Miocene-Early Pliocene and gradual progradation during the Early Pliocene-Pleistocene. Published exploration results indicate that the main reservoirs of the discoveries in blocks A1 and A3 are Pliocene frontal splays and channel-levee fills, dominated by fine and very fine-grained sandstones, in structural and structural-stratigraphic traps. Analytic results from seismic characters and several exploration wells indicate that channel complexes and associated overbanks and frontal splays with fine-grained sandstones and siltstones trapped by the four-way closures are primary reservoir targets.

Regional controls in the distribution and morphometry of deep-water gravitational deposits along a convergent tectonic margin. Southern Caribbean of Colombia

“…The large volumes of fine-grained sediments accumulate in high-relief levees that confine the flows, allowing flows to travel downslope for hundreds of kilometers. A similar association between high sediment supply, gentle slope gradient, and the occurrence of extensive channel-levee systems occurs in the convergent margin of India, along the Bengal fan (Ma et al, 2020). Also, large channel-levee systems have been documented in the salt-diapir-influenced Fuji-Einstein system (Eastern Gulf of Mexico, Milliman and Meade, 1983;Piper et al, 2012;Sylvester et al, 2012), in the extensional domain of the upper-and mid-slope regions of the deep-water Niger Delta (Chima et al, 2019;Jolly et al, 2017) and in the Amazon Fan, (Pirmez et al, 2000;Pirmez and Flood, 1995).…”

Application of Reverse Time Migration to Faults Imaging in Rakhine Basin, Myanmar

“…Based on an analysis of seismic facies and attributes, previous studies found that the architectural elements mainly consist of a confined slope channel complex system and an aggradational channel levee complex [35,36]. Some studies hypothesized results that the basin underwent a rapid progradation during the Oligocene-Middle/ Upper Miocene, a gradual retrogradation during the Middle/Upper Miocene-Early Pliocene, and a gradual progradation during the Early Pliocene-Pleistocene [36]. Basu et al [37] described the stratigraphic chart and structural trends in the Rakhine Basin.…”

3D anatomy and flow dynamics of net-depositional cyclic steps on the world’s largest submarine fan: a joint 3D seismic and numerical approach

“…Turbidite systems in Rakhine Basin have received considerable attention recently, due to the discovery of the commercial Shwe gas field in the Rakhine turbidite systems of Pliocene age (e.g., Yang and Kim 2014;Zhan et al 2019;Ma et al 2020). The recoverable gas reserves from the Shwe gas field were estimated to contain 4 trillion cubic feet of extremely dry gas (Yang and Kim 2014).…”

“…However, plan-view distribution patterns of sandy supercritical-flow deposits in net-depositional cyclic steps remain undocumented, due to a lack of 3D anatomy of net-depositional cyclic steps. Ma et al (2020) have suggested that high-amplitude events imaged as peak reflectors are seismic responses to low gamma vs. high resistivity well-log signatures away from the shale baseline, both of which are asymptomatic of sand-rich lithologies composed mainly of fine-grained sandstones and siltstones. High seismic amplitudes are high RMS attributes in the Bengal seismic database utilized in this study, therefore, represent seismic responses of sandy deposits.…”