| dc.description.abstract | The Pliocene-Recent Muda formation is essentially undeformed in the West
Natuna Basin, and excellent resolution of this interval on three-dimensional seismic data
in Belida Field allows detailed interpretation of component fluvial-deltaic systems.
Detailed interpretation of seismic time slice and seismic sections along with seismic
facies analysis, horizon mapping, and extraction of seismic attributes provide the basis to
construct a sequence stratigraphic framework and determine patterns for sediment
dispersal and accumulation.
The Muda interval contains five third-order sequences, with depositional
environments confined to the shelf and consisting mainly of fluvial elements. Sequence
boundaries (SB) apparently result from major sea level falls, since there was no tectonic
uplift and the field underwent only regional slow subsidence during sedimentation of the
study interval.
Sea level fluctuation also caused changes in fluvial patterns. Analysis of
changing channel patterns indicates that major systems tracts relate to specific channel
patterns. The Lowstand Systems Tract (LST) is generally dominated by larger channel dimensions and low sinuosity channel patterns. The Transgressive Systems Tract (TST)
typically contains relatively smaller channels with high sinuosity. Channels in the
Highstand Systems Tract (HST) generally show moderate sinuosity channels and are
intermediate in size, larger than TST channels but smaller than LST channels. Crossplots
of stratigraphic position and channel morphology indicate that within the transition from
LST-TST, channel dimensions (width and thickness) generally decrease and channel
sinuosity generally increases.
High sinuosity, meandering and anastomosing channels are generally found near
the maximum flooding surface. Low sinuosity channels occur within the HST-SB-LST
succession, with the exception of higher sinuosity meandering channels evolving inside
valleys. Larger, lower sinuosity channels result from high gradient and high discharge
associated with stream piracy. Smaller, high-sinuosity channels result from low gradient
and small discharge.
Extraction of seismic attributes such as RMS Amplitude and Average Reflection
Strength show these depositional features in greater detail. In the Belida Field area,
lowstand channels were found to comprise the greatest volume of sandstone bodies.
Seismic delineation of the distribution and morphology of these channel systems provides
critical input for reservoir modeling and volumetric analysis. | en |
