The Interplay of Channel-Levee Systems and Mass-Transport Complexes in the Pliocene-Quaternary Rakhine Basin, Offshore Myanmar

Abstract

Channel-levee systems and mass-transport complexes（MTC’s）are important deep-water oil and gas reservoirs and seals, respectively. Previous research has focused on geological characterization of individual channel-levee systems and MTC’s in outcrop and seismic-reflection data. However, the influence of channel-levee systems on MTC deposition remains elusive. Here, we use three-dimensional seismic-reflection data (~30 Hz), which covers an area of ~2000 sq. km in the Rakhine basin, offshore Myanmar, to characterize growth styles of Pliocene to Quaternary channel-levee systems and their influence on the locations of MTC deposition. We observed two general types of MTC’s. Large-scale Pliocene MTC’s are characterized by chaotic, mounded seismic-reflection configuration and fan-like geometries, which we interpret to be fed by self-edge and/or slope failure. They range in area from ~200-360 sq. km, with maximum thickness of 220 ms (TWTT). Smaller-scale Quaternary MTC’s exhibit similar seismic characteristics, but we interpret them to have been triggered by local failures of anticlines and/or channel-levee systems on the paleo-seafloor. These smaller MTC’s are only tens of sq. km in area and <100 ms (TWTT) in thickness. The channel-levee systems appear to create topographic lows 10-30 km wide and up to 320 ms (TWTT) thick between levee-overbank deposits. The MTC’s infill depositional topography between laterally offset channel-levee systems. However, channel-levee systems do not clearly incise MTC’s. Depositional topography created by channel-levee systems, thus, determined the distribution of MTC’s, and not the other way around, as is commonly interpreted. This study helps to improve understanding of the interplay of channel-levee systems and MTC’s, which plays an important role in reservoir and seal geometries in the Pliocene-Quaternary Rakhine Basin, offshore Myanmar, and analogous prospective sedimentary basins where the locations of MTC deposition are influenced by channel-levee systems, such as Amazon Fan, offshore Brazil, and Kutei Basin, offshore Borneo.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018