Effect of lithospheric flexure to recent sedimentation in Rakhine Basin

Abstract

Shell Myanmar and venture partners have been actively evaluating prospectivity of the Rakhine basin through a large amount of newly acquired 3D seismic data. From regional geological work and seismic data interpretation, unconformities that are likely associated to lithospheric flexure events within recent deepwater sediment are observed in the seismic. This observation has sparked the question: How does lithospheric flexure influence the deposition of deepwater turbidite sediment sourced from the east and north? Generally, sediment loading at accretionary prisms cause underlying plates to bend downward. As the result of plate bending, the plate swells near the trench. The amount of flexure and swell depends on the thickness of the underlying plate and the weight of sediment load. 3D seismic within Shell’s acreage and 2D seismic from IODP Expedition 362 are used to investigate the presence of the forebulge or swell due to lithospheric flexure. The seismic suggests that bulging does occur at Indian plate near to subduction zone. However, the presence of the Ninety East Ridge increases the complexity of bulging. Sufficient seismic coverage has enabled the observation of deepwater turbidite deposits pattern from trench to outer bulge and their correlation with the forebulge evolution. This presentation aims to share seismic observations of deepwater sediment dispersion patterns at recent age that correlate with forebulge evolution. Also, through this evaluation, areas likely deposited with coarser grain sediment at recent age have been postulated. However, this presentation does not intend to predict lithospheric flexure via flexural modelling or mathematic analysis. Lastly, understanding the impact of lithospheric flexure on recent sedimentation is useful for predicting reservoir presence, as the present is the key to the past. However, predicting reservoir through plate flexure evolution within the world largest deepwater fan and multiple sources input quickly proved to be challenging and debatable. In this context, contention has made room for a remarkable breadth of good science in evaluation correlation between lithospheric flexure and recent sedimentation patterns through seismic observation. This presentation will show block seismic cross sections and 2-2D regional lines from IODP Expedition 362, additionally block scale amplitude maps of recent age will be shown.

AAPG Datapages/Search and Discovery Article #90336 ©2018 AAPG Asia Pacific Region, The 4th AAPG/EAGE/MGS Myanmar Oil and Gas Conference, Myanmar: A Global Oil and Gas Hotspot: Unleashing the Petroleum Systems Potential, Yangon, Myanmar, November 13-15, 2018