Earth Science and Engineering, Imperial College London
Doi
Abstract
Fluvial sandstones constitute one of the major clastic petroleum reservoir types in
many sedimentary basins around the world. This is especially true in the Tertiary
basins of Southeast Asia, which display a wide range of fluvial channel reservoir
types. This study is based on the analysis of high-resolution, shallow (seabed to ca.
500 m depth) 3D seismic data which provide exceptional imaging of the geometry,
dimension and temporal and spatial distribution of fluvial channels. The Malay Basin
comprises a thick (>8 km), rift to post-rift Oligo-Miocene to Pliocene basin-fill. The
youngest (Miocene to Pliocene), post-rift succession is dominated by a thick (1-5 km),
cyclic succession of coastal plain and coastal deposits, which accumulated in a humidtropical
climatic setting.
This study focuses on the Pleistocene to Recent (ca. 500 m thick) succession, which
comprises a range of seismic facies, mainly reflecting changes in fluvial channel style
and gross stratigraphic architecture. The succession has been divided into four seismic
units (Unit 1-4), bounded by basin-wide stratal surfaces. Units 3 and 4 have been
further divided into two sub-units. Two types of boundaries have been identified: 1) a
boundary that is defined by a regionally-extensive erosion surface at the base of a
prominent incised valley (e.g. Horizons C.1 and D.1); 2) a sequence boundary that is
defined by more weakly-incised, straight and low-sinuosity channels which is
interpreted as lowstand alluvial bypass channel systems (e.g. Horizons A, B, C, and
D). Each unit displays a predictable vertical change of the channel pattern and scale,
with wide low-sinuosity channels at the base passing gradationally upwards into
narrow high-sinuosity channels at the top. The wide variation in channel style and size is interpreted to be controlled mainly by the sea-level fluctuations on the widely flat
and tectonically-quiescent Sundaland Platform