Abstract: Fluvial Reservoir Architecture in the Malay Basin: Opportunities and Challenges
Mohd. Rohani Elias, Krishnan Dharmarajan
Miocene fluvial sandstones are significant hydrocarbon-bearing reservoirs in the Malay Basin. These include high energy, braided stream deposits of group K, associated with late development of extensional half grabens and relatively lower energy, meandering, and anastomosing channel deposits of group I formed during the subsequent basin sag phase.
Group K reservoirs are typically massive, commonly tens of meters thick, and cover an extensive part of the Malay Basin. These reservoirs have good porosity and permeability at shallow burial depths. However, reservoir quality deteriorates rapidly with increasing depth. Lateral and vertical reservoir continuity is generally good within a field, commonly forming a single system. Good water drive enhances recovery. Seismic modeling to determine fluid type and the extent of interfluvial shales is possible due to reservoir homogeneity.
In contrast, fluvial reservoirs formed by meandering channel deposits in group I range in thickness from less than 10 m to about 30 m and have less extensive areal distribution. Single-channel, meandering valley fills are present along the basin margin and form stratigraphic traps of limited areal extent. Coalescing channels, likely with tidal influence, are present further basinward within the lower coastal plain setting and form more sheet-like reservoirs over fairly extensive areas. There are marked variations in reservoir quality and continuity within this setting due to the intercutting of different channels having different sedimentary fills. Seismic interpretations, especially attribute maps from 3-D data, are used to map these reservoirs, both in exploring for isolated meander ng channels and in locating production wells.
AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994