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Seismic Stratigraphy and Geomorphology of a Syn-to-Post-rift Depositional Sequence; the Impact of Evolving Basin Dynamics on Depositional Architecture and Reservoir Development, Qiongdongnan Basin, South China Sea

Wild, Richard *1; Posamentier, Henry W.2
(1) South China Sea Exploration Team, Chevron, Houston, TX.
(2) Exploration & Reservoir Characterization, Chevron, Houston, TX.

The Oligocene to Early Miocene stratigraphy of the Qiongdongnan Basin, South China Sea is commonly interpreted to represent the transition from predominantly non-marine alluvial and lacustrine syn-rift strata to post-rift, marine depositional environments. Whilst several deepwater wells have penetrated the post-rift marine succession, relatively little is known about the late syn-rift to early post-rift stratigraphy of this emerging exploration area.

Analysis suggests that the onset of the marine incursion occurred earlier than previously interpreted and is related to the initiation of an Early Oligocene episode of rifting. Rapid subsidence associated with the rift-climax resulted in a predominantly marine late syn-rift succession with marginal marine and / or subaerial depositional environments restricted to the basin margins or occupying isolated basin highs.

The application of seismic geomorphology has helped decipher and characterize complex syn- to post-rift sedimentary architectures and identify a range of geomorphic elements including slope fans and aprons, channel complexes, distributary lobes, sediment waves and mass transport deposits. Mapping these features using 3D visualization techniques such as seed picking and optical stacking in flattened seismic volumes facilitates a more detailed understanding of how depositional geometry responds to spatial and temporal variations in tectonic deformation and subsidence, the creation and / or destruction of accommodation and sediment supply. Ultimately, this approach illustrates how in data limited environments the effective integration of seismic stratigraphy and geomorphology is key to the reduction of uncertainty with respect to reservoir prediction and connectivity in exploration and pre-drill analysis.


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