Print this pageSequence Architecture and Hydrocarbon Potential of the Phu
Khanh Basin Offshore Central Vietnam, South China 
Sea
LEE, GWANG H., and JOEL S. WATKINS
The Phu Khanh Basin offshore central Vietnam is the only untested basin on
the Vietnam margin of the South China Sea. Analysis of over 1,600 km of
multi-channel seismic reflection data indicates that the Phu Khanh Basin follows
a typical rift-margin development: faulted basement, synrift sedimentation, a
breakup unconformity, and postrift sedimentation.
Postrift sedimentation consists of a transgressive phase characterized by
ramp-like depositional geometries followed by a regressive phase characterized
by prograding sequences. During the transgressive phase rising sea level
provided favorable conditions for carbonate buildup development. The regressive
interval contains a number of third-order depositional sequences composed of
seismically resolvable lowstand, highstand, and rarely, transgressive systems
tracts.
Principal source rocks are believed to be synrift lacustrine sediments
deposited in graben and half-graben lakes. In the postrift section, the ramp
transgressive interval and starved, basinward portion of transgressive and
highstand systems tracts
within the regressive interval may have source rock
potential. Carbonate complexes, fractured/weathered basement, coastal sands, and
basinfloor fans probably have good reservoir quality. Potential traps include
carbonate complexes, basement hills, anticlines, fault traps, and coastal sand
traps. Hydrocarbon indicators such as flat spots, bright spots, and gas chimneys
with seeps on the seafloor occur at a number of locations.