Study of Clastic Reservoir Distribution in Active Margin Basin: Stratigraphic Play in Ciputat Half Graben (NorthWest Java Basin)


Ciputat Sub-basin is a north-west half graben within North
West Java Basin. Rifting has begun during Late Eocene
until Late Oligocene, formed by subduction activities. SynRift in Ciputat Sub-basin divided into two phases
(Schlumberger, 1986). Syn-Rift Phase-1 begun with the
deposition of the volcanic clastic and carbonate sediment.
In the Syn-Rift Phase-2, fluvio-deltaic clastic sediment
deposited unconformable above Syn-Rift phase-1 sediment.
The fluvio-deltaic sediment is composed by clastic rock
and proven as stratigraphic reservoir in the Fields around
Ciputat Low.
Stratigraphic interpretation that generated by applying 3D
seismic data is difficult to detect clastic reservoir
distribution, due to thin reservoir (below tuning thickness).
However, nearly 90% of wells drilled in the Ciputat Low
discover hydrocarbons in this reservoir that are
stratigraphically trapped.
Utilization of Frequency-derived Attributes was performed
to illustrate the geologic layering in thin layers. Geologic
frequency is simply the number of reflecting layers within
unit thickness of rock, higher geologic frequency means
more layering (Brown, 2010). In this circumstances,
interpretation of reservoir distribution conducted by
applying the Average Instantaneous Frequency. The
attribute shows sedimentation pattern of clastic reservoir
validated by existences production wells inside it. Low
frequency thus correlates with better production from
clastic reservoir. It can be considered thicker sand-shale
layering have lower frequency than thinner sand shale
layer, even the thickness of these layers are below tuning
Clastic reservoir described by Average Instantaneous
Frequency showing distribution pattern that follows axial
fluvio-deltaic system along the half graben. Sediment
provenance derives from the Sunda Microplate in the
North-West and the local highs around. Development and
exploration activities in this area can be focused to
recognize stratigraphic trap of clastic reservoir.