Sequence stratigraphy and seismic facies mapping of the syn-rift to post-rift transition in offshore Vietnam
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Abstract
The geological history of Southeast offshore Vietnam was closely related to the East Sea spreading process and could be divided into 3 main stages: pre-rift (Paleocene - Eocene), synrift (Oligocene and Middle Miocene) and post-rift (Upper Miocene to present). After the second rifting phase, this area was uplifted and eroded followed by a thermal subsidence which has created new accommodation space until present day.
This study focused on evaluating the sediment deposition based on sequence stratigraphic concepts for the transition time from syn-rift to post-rift phase. Seven sequences were defined based on characteristics of seismic facies and well log analysis. Sequence boundaries which are unconformity surfaces were interpreted by different evidence resulting from erosion activities. Within each sequence, seismic facies were characterized in accordance with the variation of lithology from wireline logs. The system tracts are able to be defined and then combined with the biostratigraphy data in order to predict the changes of depositional environment. From the Southwest to the Northeast of the study area, sediment supply decreases due to the farther distance from sediment source. The shelf break migration through time is from the west to the east of the study area. The depositional environment has shallowing upward trends from the lower to the upper part (from basin to outer-middle neritic) and deepening trend from the Southwest to the Northeast (from shelf to bathyal). Among them very good potential reservoirs were formed in syn-rift carbonates, basin floor fan/turbidite deposits in deep marine environment.
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Copyright © 2008 Department of Geology, Faculty of Science, Chulalongkorn University. Parts of an article can be photocopied or reproduced without prior written permission from the author(s), but due acknowledgments should be stated or cited accordingly.
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