Quantitative Seismic
Geomorphology of Pleistocene Fluvial Systems in the Malay Basin, Southeast Asia: Implications for Reservoir Modelling
Outcrop data
and satellite imagery of modern systems
typically provide only 2D and quasi-3D
data
on the geometry, orientation and
dimensions of reservoir sand bodies, which are critical elements for the
construction of geologically meaningful, 3D, object-based reservoir models. 3D
seismic
data
can also provide important
data
, although the ability to collate
large, statistically valid datasets is limited by the tools that are available
in standard
seismic
interpretation
software packages. We present a new
methodology for quantifying planform geometries and dimensions of fluvial channel
sand bodies that are imaged in shallow, near sea-bed, 3D
seismic
datasets.
Data
capture has been semi-automated using ArcGIS, which allows fast and efficient
mapping of these morphometric parameters. We have applied this methodology to a
Pliocene-Pleistocene fluvial succession that is spectacularly imaged on a
high-resolution, regionally-extensive, 3D
seismic
survey from the Malay Basin,
Southeast Asia, and we focus on the quantification of key channel parameters,
such as meander channel width, meander belt width and meander wavelength. We
demonstrate that the lower part of each
seismic
unit is characterised by wide,
deep, low-sinuosity channels, which pass gradually upwards into narrower and
thinner, high-sinuosity channels at the top. We speculate that a combination of
sea-level changes and fluctuations in discharge and sediment load, both of
which may have been linked to climate variations, may have controlled the
observed stratigraphic organisation. Empirical equations developed on modern
rivers have been tested on the channels identified in this study. The results
suggest that existing empirical equations cannot be applied to describe the
relationships between geometric parameters that characterise the fluvial
channels in this particular geological setting. Hence, several new empirical
relationships are proposed, which may be more applicable for predicting fluvial
channel dimensions in humid-tropical settings. Our
data
have been used to
constrain reservoir models for the deeper, oil- and gas-producing Miocene
succession, which contains a large proportion of fluvial channel reservoirs but
which is less clearly imaged on 3D
seismic
data
. The study highlights the value
of using high-quality, near sea-bed 3D
seismic
volumes for extracting analogue
data
on sand body dimensions; datasets such as these are increasingly
accessible to researchers from many parts of the world.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California